The Limits of Influence: Pico, Louvain, and the Crisis of Renaissance Astrology (MEDIEVAL AND EARLY MODERN SCIENCE) [Illustrated] 9004131698, 9789004131699

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THE LIMITS OF INFLUENCE

MEDIEVAL AND EARLY MODERN SCIENCE Editors

JOHANNES M.M.H. THIJSSEN University of Nijmegen

CHRISTOPH LÜTHY University of Nijmegen

Editorial Consultants Joël Biard, University of Tours Simo Knuuttila, University of Helsinki John E. Murdoch, Harvard University Jürgen Renn, Max-Planck-Institute for the History of Science Theo Verbeek, University of Utrecht VOLUME 4

THE LIMITS OF INFLUENCE PICO, LOUVAIN, AND THE CRISIS OF RENAISSANCE ASTROLOGY

BY

STEVEN VANDEN BROECKE

BRILL LEIDEN • BOSTON 2003

This book is printed on acid-free paper.

Library of Congress Cataloging-in-Publication Data Broecke, Steven Vanden. The limits of influence : Pico, Louvain, and the crisis of Renaissance astrology / by Steven Vanden Broecke. p. cm. — (Medieval and early modern science, ISSN 1567-8393 ; v. 4) Includes bibliographical references and index. ISBN 90-04-13169-8 1. Astrology, European—History. 2. Astronomy, Medieval. I. Title. II. Series. QB25.B74 2003 520’.9’02—dc22 2003057805

ISSN 1567-8393 ISBN 90 04 13169 8 © Copyright 2003 by Koninklijke Brill NV, Leiden, The Netherlands All rights reserved. No part of this publication may be reproduced, translated, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without prior written permission from the publisher. Authorization to photocopy items for internal or personal use is granted by Brill provided that the appropriate fees are paid directly to The Copyright Clearance Center, 222 Rosewood Drive, Suite 910 Danvers MA 01923, USA. Fees are subject to change. printed in the netherland

This book is dedicated to Dries Claeys (1915–2002)

TABLE OF CONTENTS

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii List of illustrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Chapter one. Some preliminary remarks on astrology . . . . . . . . . 1. The problem: “astronomy” and “astrology” . . . . . . . . . . . . . . 2. Natural and superstitious astrology . . . . . . . . . . . . . . . . . . . . . . . 3. Teaching the “science of the stars” . . . . . . . . . . . . . . . . . . . . . . . . 4. The structure of the “science of judgment” . . . . . . . . . . . . . . 4.1. Astrological physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2. Judicial astrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. Astrology, natural philosophy, and secrecy . . . . . . . . . . . . . . . 5.1. Astrology and natural philosophy . . . . . . . . . . . . . . . . . . 5.2. Epistemic secrecy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3. Epistemological secrecy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. Lucio Bellanti’s De astrologica veritate (1498) . . . . . . . . . . . . . Chapter two. Astrology and late medieval academic culture. Louvain, 1425–1516 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. Academic astrological genres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1. Annual almanacs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2. Conjunctions and comets . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. The uses of academic astrology . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1. Academic astrological consulting: Louvain and the Burgundian court . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2. The importance of being printed: patronage, secrecy, and censorship . . . . . . . . . . . . . . . . . . . . . . . . . 3. The teaching of academic astrology . . . . . . . . . . . . . . . . . . . . . . 3.1. Mathematics at the arts faculty . . . . . . . . . . . . . . . . . . . . . 3.2. Astrological instruction at the medical faculty . . . . 4. Astrology and theology in late medieval academic culture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1. The Louvain union of revelation and astrology . . . 4.2. Logic, revelation, and future contingents . . . . . . . . . 4.3. Astrology and future contingents . . . . . . . . . . . . . . . . . .

7 7 9 12 17 18 19 19 19 21 22 24

29 30 30 32 33 33 36 40 40 43 46 46 49 52

viii

table of contents

Chapter three. Between astrological reform and rejection: Giovanni Pico’s Disputations (1494) . . . . . . . . . . . . . . . . . . . . . 1. The problem: Pico and the astrologers . . . . . . . . . . . . . . . . . . . 1.1. Pico, Ptolemy, and astrological theory . . . . . . . . . . . . . 1.2. Pico and the challenges of conjunctionism . . . . . . . 1.2.1. The background: conjunctionist astrology in late fifteenth-century Italy . . . . . . . . . . . . . . . 1.2.2. Pico and astrological boundary-work . . . . . . 2. The solution: Aristotle, mathematics, and experience 2.1. Aristotle and astrological physics . . . . . . . . . . . . . . . . . . . 2.2. Mathematical astronomy and astrological physics 2.3. The value of common astrological experience . . . . 2.3.1. The antiquity of empirical records . . . . . . . . . 2.3.2. The inaccuracy of astronomy . . . . . . . . . . . . . . . 2.3.3. Contradictions in the astrological canon 2.4. The shape of astrological reform . . . . . . . . . . . . . . . . . . . 3. Astrology demonized: Girolamo Savonarola’s attitude to astrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chapter four. Humanism and court astrology: the 1524 conjunctions at Louvain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. The 1524 conjunctions and the expectation of a new Flood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. Albert Pigghe and the return to Ptolemaic practice (1519) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1. An astrological practitioner at the French court . . 3.2. Humanism and astrology . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3. In defense of reformed annual prognostications 4. Gaspar Laet in defense of personal experience (1520) 5. The debate at Louvain university: Thomas Montis’ disputation (1521) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. Prudence, faith, reason, and astrology: Scepper’s Assertion (1523) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1. Scepper’s dream . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2. Scepper and the Louvain humanists . . . . . . . . . . . . . . . 6.3. Scepper’s problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4. Scepper’s astrological critique . . . . . . . . . . . . . . . . . . . . . . 6.5. Scepper’s philosophical arithmetic . . . . . . . . . . . . . . . .

55 55 57 60 60 63 65 66 71 73 73 74 74 77 78

81 81 82 85 85 87 89 91 94 97 97 100 103 105 106

table of contents Chapter five. Astrology and the Louvain cosmographical tradition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. Introduction: cosmography and the 1524 debates . . . . . . 2. The rise of Louvain cosmography: Gemma Frisius . . . . . . 3. New opportunities for cosmographical patronage . . . . . . 4. Cosmography and academic mathematical instruction 5. Humanism and cosmography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. Astronomy and cosmography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7. Astrology and cosmography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8. Cosmographical instruments and astrological theorica: Gerard Mercator’s astrological instrument (1551) 9. Gemma’s familia: mathematics teaching and the medical profession . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Intermezzo. A few comments on the use and nature of astrological reform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. Business as usual: Albert Pigghe vs. Gaspar Laet . . . . . . . . . 2. Secrecy, openness, and astrological reform . . . . . . . . . . . . . . 3. The nature of astrological reform . . . . . . . . . . . . . . . . . . . . . . . . . 4. Meanwhile, among the prognosticators . . . . . . . . . . . . . . . . . . Chapter six. Copernican astronomy and Louvain astrology . . . . 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. Copernican astronomy and private astrological practice 3. Patronage, politics, and astrological activity . . . . . . . . . . . . . . 3.1. Politics and the position of the fixed stars . . . . . . . . . 3.2. The prediction of eclipses . . . . . . . . . . . . . . . . . . . . . . . . . . 4. Copernican astronomy and astrological physics in Gemma’s familia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1. Letter writing, Copernican astronomy, and the virtual familia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2. Planetary distances and the systemic virtues of Copernican astronomy . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3. The Louvain background to Dee’s Propaedeumata aphoristica (1558) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4. The interpretive problem of the Propaedeumata . . . 4.5. The Piconian background to the Propaedeumata 4.6. The Louvain connection: astrology, optics, and mathematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7. Pico’s Disputations and planetary distances . . . . . . . . 5. Astrological reform and the emergence of scientific realism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ix

113 113 115 118 121 125 127 129 131 134

137 137 139 142 143 147 147 149 153 154 158 160 161 164 168 170 171 174 179 181

x

table of contents

Chapter seven. Ptolemy, parapegmata, mathematics, and monsters. The reform of mundane astrology . . . . . . . . . . 1. Ptolemy, politics, and prognostication. Cornelius Gemma’s Ephemerides (1561) . . . . . . . . . . . . . . . . . . . . . . . . 2. Parapegmata and popular errors. Joannes Stadius’ De fixis stellis (1560) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1. Stadius’ restoration of ancient parapegmata . . . . . . . . 2.2. Medical astrology in sixteenth-century Louvain . . . 2.3. Particular experience and ancient authority . . . . . . 2.4. Popular errors and the new Ptolemy . . . . . . . . . . . . . . . 2.5. Emulating Ptolemy’s Phases of the Fixed Stars . . . . . . . 3. John Dee’s weather observations: towards a mathematical astrological physics (1548) . . . . . . . . . . 3.1. Weather observations at Nuremberg: Werner, Camerarius, and Schöner . . . . . . . . . . . . . . . . . . . . . . . 3.2. Weather observations at Louvain: John Dee . . . . . . . 3.3. Mathematical operationalism, natural philosophy, and astrological reform . . . . . . . . . . . 4. Strange heavens: teratology, prognostication, and Neoplatonism in the 1570s . . . . . . . . . . . . . . . . . . . . . . . . . 4.1. Cornelius Gemma and the new star of 1572 . . . . . . 4.2. Neoplatonism, Augustinianism, and the cosmocritical art . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3. Teratology and astrology in the cosmocritical art 4.4. The political and theological relevance of the cosmocritical art . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chapter eight. Prorogations, houses, and natal astrology . . . . . . 1. Horoscope collections and astrological expertise . . . . . . . 1.1. Joannes Stadius and the art of prorogation . . . . . . . 1.2. Particular experience and the reform of natal astrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. House division, prorogation, and the search for Ptolemaic authority . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1. Regiomontanus’ restoration of Ptolemaic prorogations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2. Prorogation and astrological house division . . . . . . 2.2.1. Abandoning the standard method: Regiomontanus and Ptolemy . . . . . . . . . . . . . . 2.2.2. Coexisting traditions. Gemma Frisius on house division . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

185 186 191 192 193 196 198 201 203 204 206 208 212 212 215 220 222 227 229 229 231 235 235 236 238 241

table of contents 2.2.3. The collapse of textual authority as a token of expertise . . . . . . . . . . . . . . . . . . . . . . . . . . 3. The collapse of empirical success as a token of expertise 3.1. Sixtus of Hemminga’s Astrologiae refutatae liber (1583) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2. Experience, the art, and the artists . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. Antecedents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xi

245 252 252 253 257 257 259 260 262

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271 Indices Index of persons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305 Index of places . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 Index of subjects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313

ACKNOWLEDGMENTS

It is with great pleasure that I acknowledge the crucial role of many friends and colleagues in the completion of this book. This project would not have been started – nor finished – without the support of my doktorvater Jan Roegiers. Charles Burnett and Jill Kraye graciously agreed to supervise my work during a crucial stay at the Warburg Institute. Time and again, members of the Louvain Seminarium Philologiae Humanisticae proved to be the heirs of a time when disciplinary boundaries were less constraining than they have since become. Jan Papy deserves special mention among them. Robert Westman made me aware that others traveled equally unfamiliar grounds. His critical comments on early drafts were particularly stimulating, as was the advice of Fernand Hallyn, John North, Geert Vanpaemel, and Christoffel Waelkens. Much later, Christoph Lüthy heroically read through the entire final draft. Many others offered valuable assistance, advice, and encouragement: Daniel Anderson, Gera van Bedaf, Paul Bockstaele, Wouter Bracke, Guido Cloet, Nicholas Clulee, Elly Cockx-Indestege, Chris Coppens, Andreas De Block, Gerard l’Estrange Turner, James Evans, Steve Farmer, Guido Giglioni, Anthony Grafton, Guido Gubbels, Wouter Hanegraaff, Darin Hayton, Stephen Johnston, David Juste, Robert Kargon, Robert Karrow, Allison Kavey, Daryn Lehoux, Jean Meeus, Ad Meskens, Adam Mosley, Jan Opsomer, Sophie Page, Lawrence Principe, Hilde de Ridder-Symoens, H. Darrel Rutkin, Jole Shackelford, Carlos Steel, Jacques Vandamme, Koenraad Van Cleempoel, Toon Van Houdt, and Shirley Yoo. The Fund for Scientific Research of Flanders (fwo-v) was particularly generous in funding the research on which most of this study is based. Further changes and revisions were made possible by a Frances Yates fellowship from the Warburg Institute, a travel grant from the Wellcome Institute, and a postdoctoral fellowship from the Johns Hopkins University. Excerpts from my paper “Dee, Mercator, and Louvain Instrument Making: an Undescribed Astrological Disc by Gerard Mercator (1551),” published in Annals of Science, 58(2001), pp. 219–40, were

xiv

acknowledgments

reproduced in chapter 5 of this book. I thank the editor and publisher for permission to use this material. Finally, I wish to thank my family and friends for their endless irony and support. Being able to engage in this strange pursuit is a great privilege. Doing so in the company of friends and loved ones is an even greater blessing.

LIST OF ILLUSTRATIONS

1.

View of LOUVAIN, c. 1600. (Copyright Leuven, Universiteitsbibliotheek.)

2.

Paul of MIDDELBURG, Invectiva (…) in supersticiosum quendam astrologum [Johannem Lichtenberger] (Antwerp, 1492). Title page. (Copyright Paris, Bibliothèque nationale.)

3.

Joannes LAET, Prognosticacie voor 1478 (Louvain, 1477). Fragments. (Copyright Paris, Bibliothèque nationale.)

4.

Cornelius Duplicius de SCEPPER, Assertio fidei adversus astrologos (…) (Antwerp and Cologne, 1523). Astrological chart of the conjunction of Saturn and Jupiter in Pisces (1 February 1524).

5.

Gemma FRISIUS in his Louvain workshop (Jan van Stalburch, 1557). (Copyright Brussel, Koninklijke Bibliotheek, Prentenkabinet.)

6.

Gemma FRISIUS, De principiis astronomiae & Cosmographiae (...) (Antwerp, 1544). Title page. (Copyright Leuven, Universiteitsbibliotheek.)

7.

Gerard MERCATOR, Astrological disc (Louvain, 1551). Front. (Copyright Basel, Historisches Museum.)

8.

Gerard MERCATOR, Astrological disc (Louvain, 1551). Front: Libra to Sagittarius. (Copyright Basel, Historisches Museum.)

9.

Gemma FRISIUS, De Radio Astronomico & Geometrico liber (…) (Antwerp and Louvain, 1545). Title page. (Copyright Leuven, Universiteitsbibliotheek.)

10. Joannes STADIUS, Tabulae Bergenses (...) de fixis stellis Commentarius (...) (Cologne, 1560), p. 238. Update for 1560 of Ptolemy’s astrological star catalogue, constellations of Leo and Virgo. (Copyright Leuven, Universiteitsbibliotheek.) 11. Joannes STADIUS, Ephemerides novae et auctae (...) (Cologne, 1560). Birth chart of René de Châlon (4 February 1519). (Copyright Leuven, Universiteitsbibliotheek.)

xvi

list of illustrations

12. Sixtus ab HEMMINGA, Astrologiae ratione et experientia refutatae liber (...) (Antwerp, 1583). Birth chart of Bernard de Merode (10 October 1522). (Copyright Paris, Bibliothèque nationale.)

View of LOUVAIN, c. 1600. (Copyright Leuven, Universiteitsbibliotheek.)

Paul of MIDDELBURG, Invectiva (…) in supersticiosum quendam astrologum [Johannem Lichtenberger] (Antwerp, 1492). Title page. (Copyright Paris, Bibliothèque nationale.)

Joannes LAET, Prognosticacie voor 1478 (Louvain, 1477). Fragments. (Copyright Paris, Bibliothèque nationale.)

Cornelius Duplicius de SCEPPER, Assertio fidei adversus astrologos (…) (Antwerp and Cologne, 1523). Astrological chart of the conjunction of Saturn and Jupiter in Pisces (1 February 1524).

Gemma FRISIUS in his Louvain workshop (Jan van Stalburch, 1557). (Copyright Brussel, Koninklijke Bibliotheek, Prentenkabinet.)

Gemma FRISIUS, De principiis astronomiae & Cosmographiae (...) (Antwerp, 1544). Title page. (Copyright Leuven, Universiteitsbibliotheek.)

Gerard MERCATOR, Astrological disc (Louvain, 1551). Front. (Copyright Basel, Historisches Museum.)

Gerard MERCATOR, Astrological disc (Louvain, 1551). Front: Libra to Sagittarius. (Copyright Basel, Historisches Museum.)

Gemma FRISIUS, De Radio Astronomico & Geometrico liber (…) (Antwerp and Louvain, 1545). Title page. (Copyright Leuven, Universiteitsbibliotheek.)

Joannes STADIUS, Tabulae Bergenses (...) de fixis stellis Commentarius (...) (Cologne, 1560), p. 238. Update for 1560 of Ptolemy’s astrological star catalogue, constellations of Leo and Virgo. (Copyright Leuven, Universiteitsbibliotheek.)

Joannes STADIUS, Ephemerides novae et auctae (...) (Cologne, 1560). Birth chart of René de Châlon (4 February 1519). (Copyright Leuven, Universiteitsbibliotheek.)

Sixtus ab HEMMINGA, Astrologiae ratione et experientia refutatae liber (...) (Antwerp, 1583). Birth chart of Bernard de Merode (10 October 1522). (Copyright Paris, Bibliothèque nationale.)

INTRODUCTION

A little over five years ago, I presented my first paper at an international conference. Months of study on an unknown astrological instrument had made it necessary to seek advice from a specialized audience, and a meeting of historians of science in a lush Danish abbey seemed eminently suited for the purpose. After I had presented my results and answered a number of helpful questions, I returned to my seat. Suddenly, a large man swiftly made his way across the darkened room, crouched next to me, and belligerently whispered: “Do you believe in this? This is rubbish! Charlatanism!” It took me a few seconds to realize that my assailant referred to the topic of my talk, rather than the quality of my analysis. Even so, it seemed wise to reassure him that I did not “believe” in astrology. This drew out a muffled groan from the historian’s lips as the next speaker started his talk, and the rules of scholarly propriety were restored. Most readers might consider my antagonist’s intervention unprofessional. However, it does highlight the problematic position of astrology in virtually any grand narrative of the history of Western science. Cultural historians have established the omnipresence and flexibility of astrology in early modern Europe beyond any doubt.1 But this does not seem to have convinced many historians of science that the topic might be relevant to their concerns.2 We still need an approach to early modern astrology that confirms its omnipresence and flexibility, but explores its intimate ties with other “scientific” disciplines like natural philosophy, medicine, or astronomy as well. This book wishes to address that need. This project is doomed to failure if it does not rely on a historically adequate definition of its subject matter. Early modern astrology was an exceptionally rich discipline in terms of conceptual resources, 1 Good examples include Allen, The Star-Crossed Renaissance; Thomas, Religion and the Decline of Magic, pp. 283–388; Grafton, Cardano’s Cosmos. 2 An excellent exception is Bowden, The Scientific Revolution in Astrology. Liba Taub still exhorted historians of science towards the “rehabilitation of wretched subjects” in 1997.

2

introduction

data processing, and the application of various instruments. If we choose an overly narrow definition, we compromise our reconstruction of this richness before we begin. If we cast our nets too wide, we run the risk of discussing nothing specific at all.3 This problem is explored in chapter 1. Chapter 2 provides a contextual study of the use and status of academic astrology in the late Middle Ages. Since many of my questions have not been addressed before, I have maximized the depth of my exploration by focusing on a particular community of astrological practitioners at Louvain (in current-day Belgium). Located at the crossroads of the French and German spheres of influence, the university of Louvain (1425) offered an exceptional combination of institutional continuity, available sources, and intellectual relevance. Its matriculation numbers rivaled those of Oxford, Cambridge, Padua, Salamanca, and Paris by the end of the fifteenth century.4 Chapter 3 traces another precedent for our story to northern Italy in the 1490s. In 1496, a Bolognese printer published the most incisive astrological critique ever written: the Disputations of Giovanni Pico della Mirandola. Coming from an author whose astrological sympathies were well known, this critique took many contemporaries by surprise. My reading of the Disputations argues that the work’s primary objective was to attack a new genre of popular prognostications that were based on astrological conjunction theories. Accordingly, Pico’s attitude to astrological theory was more forgiving than is often assumed. In fact, it is possible to read the Disputations as a sophisticated call for the reform of astrological practice. Chapter 4 shows how popular expectations surrounding a Saturn-Jupiter conjunction in February 1524 created a similar challenge in the Low Countries. Court astrologers firmly embraced the Disputations as a repository of arguments against the prediction of a new biblical Flood. Targeting local practitioners who pursued the traditions of late medieval academic astrology, these courtly opponents soon adopted the humanist-scholastic debate as a broader framework for their discontent. The 1524 debates thus forged a firm alliance between humanist culture and reformed astrological practice. Chapter 5 introduces the direct consequences of these changes. After 1524, several Louvain mathematicians successfully created a 3

Good examples of this problem are Geneva, Astrology and the Seventeenth Century Mind, and Vickers, “Analogy versus identity.” For a more useful approach, see Hutchison, “What Happened to Occult Qualities?” 4 See Schwinges, “Admission,” pp. 189 and 191.

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connection between astrology and the new discipline of cosmography. Cosmography provided mathematicians with an opportunity to publicize a number of astronomical and astrological problems, and to underwrite their expertise in sumptuous and/or didactic products. The success of this strategy was confirmed by a discourse that linked astrological competence with high social status. From the respective angles of court astrology and cosmographical culture, chapters 4 and 5 introduced the advent and initial promotion of a new practice of astrological reform. The subsequent Intermezzo focuses on this notion of astrological reform, and explores its functions among the people who promoted this practice. Such functions were two-fold. On the one hand, astrological reform provided an alternative to the astrologer’s traditional public function: making specific predictions of the future. On the other hand, we find that the success of this alternative enabled its practitioners to relegate specific predictions to the realm of private consulting. The final three chapters of this book each explore one aspect of astrological reform. Chapter 6 focuses on its astronomical component through the early reception of Copernican astronomy at Louvain. Social secrecy (which manifested itself in a sharp distinction between public and private practice) shaped the modalities of this reception.5 Although early interaction with Copernicus’ On the Revolutions was marked by astrological concerns, subsequent publications presented these concerns as strictly astronomical. Still, this public separation was occasionally undone in local references to the patronage of reformed astrological practice. Finally, this chapter explores the singular Louvain interest in Copernicus’ heliocentrism, and shows how this was motivated by its relevance to Pico’s astrological critique. In its early stages, astrological reform mainly affected predictive practice through the implementation of Ptolemy’s Tetrabiblos. This created a new problem for courtly reformers when their urban competitors began to imitate Ptolemaic practice and its reformist discourse. As a result, elite practitioners exerted themselves in a further cultivation of astrological reform. Chapter 7 presents Louvain results in the domain of mundane astrology (the prediction of largescale events), showing how it stimulated a surprisingly wide variety of innovations.

5

The notion of “social secrecy” is further explained in chapter 2.

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Chapter 8 focuses on the domain of natal astrology (the prediction of individual fates at birth). Initial reform in this sub-discipline also derived from the revival of Ptolemaic practices. Many Renaissance astrologers employed this public context to claim their ability to make specific predictions of one’s future. However, astrological critics began to turn such public testimony of a practitioner’s expertise against natal astrology. This development discredited even personal experience as a reliable criterion to identify proper astrological practice. The title of this book, The Limits of Influence, addresses the result of these developments. Influence (influentia) was one of three theoretical categories that scholastic Aristotelians used to explain celestial effects in the sublunary realm.6 The other two were celestial motion, which guaranteed terrestrial generation and corruption, and visible celestial light, which produced heat. Celestial “influences” in turn carried every other effect, ranging from cold to courtship, down to earth. This makes the notion of “influence” almost coterminous with late medieval academic notions of astrology. Likewise, the investigation of influence became an essential component of the practice of astrological reform. In addition, “the limits of influence” also evokes the limits of astrological reform. Public reform of astronomy (the “science of motion”) was thriving after the second half of the sixteenth century. This was the age of Tycho Brahe’s Astronomiae instauratae mechanica (1598) or Johannes Kepler’s New Astronomy (1609). The reform of mundane astrology became more complicated. After an initial emphasis on the first two books of Ptolemy’s Tetrabiblos, elite reformers largely abandoned the genre of annual prognostications, as their urban counterparts caught up with them. Instead, they transformed mundane astrology in different directions. At Louvain, these transformations led to weather prediction, the mathematization of astrological physics, and new directions in teratology. One can only guess what strange offspring awaits us elsewhere. At Louvain, but also as far away as Copenhagen, we find that the public reform of natal astrology came to a virtual halt by the 1580s. This was intimately connected with a failure to uphold the distinction between public reform and private prediction, a failure that derived from the need to provide spectacular tokens of exper6

See North, “Celestial Influence”; Grant, “Medieval and Renaissance Scholastic Conceptions.”

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tise. Obviously, this does not imply that natal horoscopes were no longer cast, and individual fates no longer predicted. Most indications show that the art was still widely practiced in the seventeenth century.7 The crucial point is that natal astrology became a largely private enterprise among the elite of the Holy Roman Empire after the 1580s.8 Natal astrology went underground until its spectacular resurgence in the late nineteenth and early twentieth century. By that time, it could not be reconnected with mainstream scientific culture. This interpretation is of direct relevance to popular narratives in the history of science, which date astrology’s demise as a respectable pursuit to the early modern period. Along with alchemy, astrology stands among the notorious “losers” of the changes that revolutionized European science between 1500 and 1700.9 As an alternative, I suggest that astrological reform began to operate at variable speeds in the second half of the sixteenth century. During this crucial period, some reformed practices remained successful in terms of their ability to sustain public support, while others began to fail. The former were eventually separated from their original disciplinary links with the latter, and reconstructed into something new (e.g., the “science of motions” was gradually turned into the discipline of “astronomy”). For now, it seems advisable to interpret this as a strictly local phenomenon. The conclusions of this book are based on the situation in one particular region of the Holy Roman Empire. In my view, current research does not permit a reliable comparison with astrological practice in Italy, France, Spain, or the British Isles. At the very least, one should view our own distrust of astrology as a historically contingent phenomenon. The increased perception of astrology as unreliable among the European elite, needs to be understood against the typical Renaissance background of a nascent capitalist economy, an incisive restructuring of cultural tools, and a failing trust in political and religious edifices. Obviously, important

7 Further references can be found in Guérin, “Les horoscopes au xviie siècle”; Curry, Prophecy and Power. 8 For an interesting English example, see Traister, The Notorious Astrological Physician, pp. 89–90. 9 Wright, “Astrology and Science,” provides a useful and critical review of common explanations for astrology’s “gradual fading-away” (p. 421) in the seventeenth century.

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casualties did occur. But it is anachronistic to interpret this as an inevitable downfall, or as an essential symptom of astrology’s pseudoscientific status. As a judgment, “astrology is a pseudo-science” closes the developments in this book. It should not explain, nor justify them. Veritas filia temporis.

CHAPTER ONE

SOME PRELIMINARY REMARKS ON ASTROLOGY

This study traces changes in astrological practice in sixteenth-century Europe. When using the term “practice,” I refer to “the mutual adjustment of cultural elements.”1 These cultural elements belong to various types: things, ideas, data (e.g., birth chart, harmonic theory, inscribed positions of celestial bodies). In the case of astrology, their adjustment emerges in the prediction of future events on earth (e.g., the growth of crops, the success of marriages, the fate of dynasties). Astrology hardly monopolized the prediction of future events in the sixteenth century. Some of its most important contenders were Christian theology, popular proverbs, and medical prognosis. This means that a reliable definition of astrology must include a characterization of the things, ideas, and data that were specific to it. This characterization should also have sufficient spatio-temporal stability to be at least relevant to late medieval and Renaissance Europe. This chapter sets out to develop a reliable definition of astrology, and to explore some of its crucial ramifications.

1. The problem: “astronomy” and “astrology” Dissolving the thorny semantics of “astrology” in a pre-modern context requires that we first expose the problem. This section does so through a historicizing look at the modern antagonism between “astronomy” and “astrology.”2 Addressing his fellow banqueteers in Plato’s Symposium, the stern Eryximachus describes astronomy as the study of love-connections. “Astronomy,” he explains, “investigates the movements of the stars and the seasons of the year.” It shows how celestial bodies exemplify both orderly and unruly “love,” thereby providing fertility and frost, or health and hail. In other words: Plato’s “astronomy” referred to 1 Pickering, “From Science as Knowledge to Science as Practice,” p. 10. Pickering attributes this definition to Ian Hacking. 2 For an introduction, see Pines, “The Semantic Distinction,” pp. 343–344.

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what we call astrology, the study of celestial effects on earth.3 Plato’s pupil Aristotle, who had little to say about love, discussed the mathematical study of the heavens in his Physics. Although this discipline brings to mind our notion of astronomy, Aristotle in fact called it “astrology.”4 One might infer that a semantic exchange between “astronomy” and “astrology” occurred in the period separating us from Plato and Aristotle. However, the ancient record tells a more complicated story. For instance, consider Cicero’s De divinatione (c. 44 bc). In the first book, Cicero attacks “the prophecies of astrologers.”5 Is this evidence of the semantic exchange? It seems not, since Cicero later mentions two “astrologers” who “did not employ their art as a means of divining, though they were eminent in all other branches of astrology.”6 “Astrology” seems to have become a generic term that covers both our notions of astronomy and astrology. This usage was predominant in ancient Latin culture, as even a cursory inspection of the Thesaurus Linguae Latinae will show.7 St. Augustine’s City of God (ad 413–427) praised Thales’ skill in the “astrological” calculation of eclipses.8 Discussing similarities in the health of twins, the same work mentioned how “astrology” attributed this to their similar time of birth.9 Such indeterminacy persisted through the Middle Ages. One influential example is the astrological textbook of Guido Bonatti (c. 1282), a Bolognese professor who had the dubious honor of being placed in the eighth circle of Dante’s Inferno. Bonatti distinguishes between “astrology,” a contemplative science of magnitude, and “astronomy,” a practical science of judgment. He explicitly adds that “astronomy” and “astrology” are often interchanged.10 A similar lack of interest in the distinction between both notions can be detected in the work of Pierre d’Ailly (c. 1350–c. 1420).11

3

Plato, Symposium 188b (eds./trans. Hamilton/Cairns, p. 541). Aristotle, Physics 193b26. 5 Cicero, De divinatione, i.12. 6 Ibid., ii.88: “(…) cum in ceteris astrologiae partibus excellerent, hoc praedictionis genere non usos.” 7 Thesaurus Linguae Latinae, vol. 2 (Leipzig: Teubner, 1900–1906), s.v. “astrologia” (c. 965–966) and “astronomia” (c. 968). 8 St Augustine, De civitate dei, viii.2. On St Augustine and astrology, see De Vreese, Augustinus. 9 Ibid., v.2. 10 Bonatti, Liber astronomiae, book i, ch. 12. 11 Thorndike, History, vol. 4, pp. 109–110. 4

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2. Natural and superstitious astrology This instability of the word “astrology” constitutes an important reason to abandon semantics in favor of semiotics. This implies a closer look at the ideas, things, and data that populate “astrological” practices. Previous historians often did this by adopting the medieval distinction between “natural” and “superstitious” astrology. This dichotomy was introduced in the encyclopedic Etymologies of Isidore of Seville (c. 560–636): Astronomy concerns the revolutions of the heavens, the rising, setting, motions, and etymologies of the stars. Astrology, on the other hand, is partially natural, partially superstitious. She is natural when she describes the course of sun and moon, or certain stations of the times (stationes temporum) of the stars. The astrology pursued by the mathematici, however, is superstitious: they make auguries from the stars, arrange the twelve signs in the heavens according to the single parts of soul or body, and attempt to predict the nativities and morals of men from the course of the stars.12

According to our bishop of Seville, “natural astrology” included both astronomical knowledge and astrological weather predictions. “Superstitious astrology,” on the other hand, concerned itself with nativities and the prediction of individual fate. This conceptual pair probably reached a wide audience by the Carolingian age, since it was adopted in De universo of Rabanus Maurus (c. 780–856) and De trinitate of Rupert of Deutz (c. 1075/6–1129).13 Isidore’s distinction classified astrological practices as manifestations of moral attitudes; this is confirmed by its later career. The Didascalicon of Hugh of St. Victor (1096–1141) slightly expanded the range of practices that count as “natural astrology,” and organized “superstitious astrology” around the criterion of free will.14 Likewise, Peter Abelard (1079–1142) was more interested in the intentions 12 Isidore of Seville, Etymologiarum sive originum libri xx, ed. Lindsay, chapter iii.27: “(…) Astronomia caeli conversionem, ortus, obitus motusque siderum continet, vel qua ex causa ita vocentur. Astrologia vero partim naturalis, partim superstitiosa est. Naturalis, dum exequitur solis et lunae cursus, vel stellarum certas temporum stationes. Superstitiosa vero est illa quam mathematici sequuntur, qui in stellis auguriantur, quique etiam duodecim caeli signa per singula animae vel corporis membra disponunt, siderumque cursu nativitates hominum et mores praedicare conantur.” Cf. Fontaine, “Isidore de Séville.” For the meaning of “statio,” see Le Boeuffle, Lexique, pp. 250–252. 13 Rabanus Maurus, De clericorum institutione (Migne (ed.), Patrologia Latina, vol. 107, p. 403). 14 Hugh of St Victor, Didascalicon (Migne (ed.), Patrologia Latina, vol. 176, p. 756).

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than the actual practices of astrologers: his Expositio in Hexaemeron distinguished between the prediction of “futura naturalia” and “futura contingentia.”15 According to Abelard, superstitious astrology predicts future contingents that happen through our volition, and does so through demonic intervention.16 Obviously, defining the category of “superstitious astrology” as a breach of human free will was to make the notion very problematic. Thomas Aquinas (1204–1274) acknowledged that the stars do act upon man’s sensory powers, and thereby influenced the will of most men indirectly. This implied that the definition of natural astrology was a matter of individual moral responsibility, as was epitomized in the popular adage “sapiens dominatur astris.”17 A remarkable illustration of the nebulous boundaries between natural and superstitious astrology comes to us from late medieval Paris. On 19 February 1494, the Parisian faculty of theology published its report on a question which the Parliament had passed on to its members ten months before: whether certain astrological books in the library of Master Simon de Phares (1444–c. 1499) should be condemned or not.18 Although trained as a physician, Simon de Phares seems to have pursued astrology as his exclusive career. While in the service of Jean ii of Bourbon (1427–1488), Simon settled in Lyon in the early 1480s, where he set up a successful astrological practice that attracted royal attention by 1490, when King Charles viii came to Lyon for a personal consultation. Soon after this, the official of Lyon ordered Simon to abandon all astrological practice and to surrender part of his library, referring to a new royal decree against magicians and soothsayers. The subsequent report of the Paris theologians condemned the “divinatory astrology” that predicts from nativities, determines the outcome of an enterprise with great specificity, claims to reveal both past and future secrets, and attributes marvelous properties to images or objects.19 This form of astrology was distinguished from a “true astronomy” that: 15

The astrological content of this commentary, and its connection to other astrological authors (notably Raymond of Marseille), has been discussed by d’Alverny, “Abélard et l’astrologie.” 16 See Migne (ed.), Patrologia Latina, vol. 178, pp. 754–755. 17 See Litt, Corps célestes, pp. 206–219. 18 On the biography and condemnation of Simon de Phares, see especially Boudet, Lire dans le ciel, pp. v–xi; Thorndike, History, vol. 4, pp. 544–561. 19 Du Plessis d’Argentré, Collectio, vol. 1, p. 325b.

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Considers the magnitude of the heavenly bodies, their oppositions and motions, which predicts the conjunctions, oppositions and other conditions of sun, moon and other planets, and which conjectures some of their general natural effects in a probable and prudent manner (which we would honor as a liberal, noble, and useful art).20

Isidore of Seville still shaped the conceptual framework of the Paris theologians. The list of condemned books, however, reveals a surprising interpretation of these categories. Among the books that escaped censorship were treatises on the construction and use of astronomical instruments, mathematical textbooks, one almanac, several of Pierre d’Ailly’s astrological works and a copy of Al-Kindi’s De pluviis. The most interesting case, however, is a manuscript of Joannes Angelus’ Astrolabium planum (1488).21 Only the third part of this work, “depicting the faces and the twelve degrees with their properties,” was condemned by the theologians. The three acceptable parts contained tables of ascension and astrological houses, a methodology to verify the ascendent in a nativity-chart, and an extensive review of the significations of each planet in different houses and aspects, each taken from Firmicus Maternus’ Mathesis.22 The fate of Angelus’ Astrolabium planum illustrates how “natural astrology” enjoyed a very wide margin of interpretation in late medieval academic culture. While the moral norms informing “natural” and “superstitious” astrology remained fairly stable, their identification with actual practices reveals itself as highly variable. The reasons for this are obvious in retrospect: the concept of “natural astrology” was developed to condemn astrological practices that presented moral challenges to early Christian religious authorities. Accordingly, its norms policed only a small subset of the ingredients that constitute a practice

20 Ibid., vol. 1, p. 325b: “Veram Astronomiam, quae corporum coelestium magnitudinem, oppositiones, motusque considerat, quae solis & lunae aliorumque planetarum conjunctiones vel oppositiones caeterasve habitudines praedicit, quae item effectus quosdam eorum naturales probabiliter ac prudenter in universali conjicit (quam ut liberalem, nobilem, utilemque Artem veneramur).” These descriptions of “true astronomy” and “divinatory astrology” are reminiscent of Jean Gerson’s Trilogium astrologie theologizate (1419), composed for the future king Charles vii. 21 A good introduction to Angelus’ astrological activities is Knobloch, “Astrologie als astronomische Ingenieurskunst.” 22 These parts of the Astrolabium planum reproduced Firmicus Maternus, Mathesis, chapters iii.2–14, iv.2–16, 19 and v.1–2.

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(i.e., the astrologer’s moral intent). This implies that the distinction between “natural” and “superstitious” astrology should be used with great caution as a definition of astrological practice.

3. Teaching the “science of the stars” This problem can be circumvented through the didactic traditions of Western astrology. By their very nature, pedagogical practices typically cover the full range of a subject. To an important extent, they also offer remarkable stability across space and time. The quintessential textbook of Western astrology, Ptolemy’s Tetrabiblos (second century ad), described astrology as a practical “prognostication through astronomy.” However, this central exercise was preceded by two preparatory disciplines. The first (both in rank and in power) was mathematical astronomy. In second place, Ptolemy referred to a discipline: By means of which we investigate (‰πισκεπτeµε©α), through the physical (φυσικÀ), peculiar quality (ŒδιοτροπÝα) of the (astronomical) configurations, the changes brought about in those things that are part of the sublunary realm (τ‡ν ‰µπεριεχοµÛνων).23

This unnamed second discipline studied the causal effects of astronomical configurations on earth, independently of astrological judgment. A similar disciplinary configuration can be found in one of the prominent textbooks of medieval Arabic astrology: Al-Biruni’s book on the #ilm al-tanjim or “science of the stars” (c. 1029). Its table of content reveals a curious fourfold division of subject matter. First, we find a thorough introduction to advanced astronomical theory. Next comes the practical application of this knowledge through the calculation of celestial configurations and chronological data. In third place, al-Biruni provides a review of basic astrological concepts (signs, planets, houses etc.). Finally, he instructs his readers in “judicial astrology” ( #ilm ahkam al-nudjum).24 Among these four branches, we find that the first two mirror Ptolemy’s first preparatory discipline (astronomy), the third his second preparatory art, and the fourth his “astronomical prognostication.” 23

Ptolemy, Tetrabiblos i.1 (ed./trans. Robbins, p. 3 – henceforth referred to as “Tetrabiblos”). The translation is my own. 24 Al-Biruni, Book of instruction, trans. Wright, pp. viii–xi. Compare Pines, “The Semantic Distinction.”

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A similar four-fold arrangement was introduced in Italian academic teaching at the end of the thirteenth century. At Padua, for instance, we find Pietro d’Abano using “astrology” as a generic equivalent to al-Biruni’s “science of the stars.” Accordingly, d’Abano distinguished between two branches: a “science of motions” and a “science of judgments.” Each branch comprised one foundational and one derivative part. D’Abano identifies the foundational (“demonstrative”) part of astronomy with Ptolemy’s Almagest. Its derivative (“narrative”) part covers a broader textbook tradition.25 For the science of judgment, he distinguishes between a fundamental “introductory” part, and a practical part that comprises three subdisciplines: mundane astrology, natal astrology, and horary astrology (including interrogations, elections, and magical images).26 Italian faculties of arts and medicine included astrology in their curriculum as an aid to medical prognosis. By all accounts, astrology was rather well esteemed. At Pavia in 1455, Master Joannes de Marliano received 125 florins for his astrological lessons, less than half of what he received for his medical lessons in the morning, but more than double the wages of his surgeon colleagues.27 The relation to medicine may also have shaped the academic organization of astrology. Demarcation issues formed a perennial point of contention in late medieval academic medicine.28 Debates over the scientific status of medicine were organized around the goals (were these predominantly theoretical or practical?) and certainty of its knowledge (was this to be found predominantly in science or art?). One professor of medicine and astrology at Siena, Lucio Bellanti (d. 1499), emphasized the scientific nature of astrology while acknowledging the practical nature of its goals.29 In doing so, he echoed Taddeo Alderotti’s position on medical knowledge in the late thirteenth century. Bellanti’s description of universal facts as “abstractions” of particular facts also shared an Averroistic outlook with the earlier medical teachings of Alderotti.30

25

Vescovini, “Peter of Abano and Astrology,” pp. 26–27. Siraisi, Arts and Sciences at Padua, pp. 84–86. On prior developments of this curriculum, see French, “Astrology in medical practice.” 27 Sottili, ed. Documenti per la storia dell’Universita di Pavia, p. 193. 28 Bellanti, De astrologica veritate, fols. a5v-a6r. 29 This position seems to come close to that of Averroes in the Colliget. See Ottosson, Scholastic Medicine and Philosophy, pp. 73–74 and 77–79; McVaugh, “The Nature and Limits of Medical Certitude.” 30 Ottosson, Scholastic Medicine and Philosophy, pp. 85–86. 26

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Medical instruction firmly embedded these issues, since it distinguished almost universally between theoretical and practical components of the curriculum. The former involved a general understanding of the arts course and specific physiological, pathological or semiotic principles, while the latter constituted a body of information with established therapeutic effectiveness.31 Medical practica combined visible signs with instructions for treatment, but did not typically concern themselves with the underlying causes of symptoms. Stylistically, the genre was characterized by assertion, rather than dialectical argument.32 Since medicine adopted the conceptual distinction between theorica and practica as a result of the introduction of Galen into the academic curriculum, one might suggest that the introduction of Ptolemy led to the adoption of a similar distinction between fundamental and derivative knowledge in astrology.33 After all, only Ptolemy’s Tetrabiblos provided a conceptual scheme that connected predictive practices to Aristotelian natural philosophy, even if Galen had made this connection more elaborately.34 Italian universities favored the practical dimensions of the “science of the stars.” This is clear from the statutes of the Bolognese studio (1405), which specify a four-year course in astrology.35 The first and second year were exclusively devoted to the study of geometry and astronomy, with a notable emphasis on the practical use of astronomical tables and instruments (e.g., the astrolabe) in the second year. Third-year students supplement this with the study of introductions to astrological theory and practice (Alcabitius’ Introductorium and ps.-Ptolemy’s Centiloquium). Only at the very end, in the fourth year, were students exposed to a “demonstrative” organization of their knowledge through Ptolemy’s Almagest and Tetrabiblos. Ferrara proposed a similar four-year curriculum in the fifteenth century.36 The descriptions of the astrology curriculum at Padua and Bologna show an interesting mixture of epistemological and didactic concerns. The ability to relate predictive skills to “demonstrative” first principles was an important feature of academic astrology. At 31

Maclean, Logic, Signs and Nature in the Renaissance, pp. 68–69. Wear, “Explorations in renaissance writings,” pp. 128–130 and 134. 33 McVaugh, “The Nature and Limits of Medical Certitude,” pp. 62–63. 34 See Riley, “Science and Tradition in the ‘Tetrabiblos’.” Girolamo Cardano explicitly made this comparison between Galen and Ptolemy in his commentary on Tetrabiblos: see Grafton/Siraisi, “Between the Election and my Hopes,” p. 104. 35 See Thorndike, History, vol. 4, pp. 281–282. 36 See Vescovini, “L’astrologia all’università di Ferrara nel Quattrocento.” 32

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the same time, the texts suggest that astrology teaching did not usually follow these demonstrative narratives. This seems to underlie the fluidity of medieval epistemological boundaries, where one man’s theorica could be another’s practica.37 However, this does not detract from the essential point: the general importance of astrological “theory” (however interpreted) was almost widely recognized in late medieval universities. Hence, it may provide a reliable framework to describe academic astrology in this period. Before we proceed to draw our conclusions, one last question remains: is the didactic discourse of late medieval Italian universities equally relevant to the transalpine regions of Europe? The answer is affirmative, with certain qualifications. By the middle of the fourteenth century, we find ample traces of astrology in northern teaching curricula. In 1358, astrological books were taught extraordinarie at Paris, while King Charles v sponsored an astrological chair in 1379.38 The borrower records of the university library confirm an extraordinary wealth of astrological manuscripts in the fifteenth century.39 Starting in 1389, the University of Vienna emphasized astronomy teaching, combined with Alcabitius’ introduction to astrology.40 By the fifteenth century, academic astrology had traveled as far northeast as Cracow, where an astrological chair was instituted around 1459. Like his Italian colleagues, the Cracow professor of astrology engaged with both judicial works (Ptolemy, Albumasar, and a host of other authorities) and the science of heavenly motions.41 The curriculum was reformed in the beginning of the sixteenth century. The new four-year program, terminating in a study of “demonstrative” literature, may have been inspired by the Bolognese model.42 At Salamanca, we find Diego de Torres occupying a chair in astrology in 1485.43 Oxford only required knowledge of Sac-

37 See Pedersen, “Theorica,” pp. 164–166. A similar remark is made in Taub, “The Rehabilitation of Wretched Subjects,” p. 84. 38 See especially Jacquart, “Médecine et astrologie”; Lemay, “The teaching of astronomy,” pp. 200–201. 39 See Vielliard, “Le registre de prêt de la bibliothèque.” 40 See Kren, “Astronomical Teaching in the Late Medieval University of Vienna.” 41 Lemay, “The Late Medieval Astrological School at Cracow,” pp. 339–341 and 350–351. 42 Markowski, “Die Astrologie an der Krakauer Universität,” pp. 87–88. 43 See Diego de Torres, Un texto, ed. Amasuno (1972). For a detailed survey of academic astrology at Salamanca in this period, see Flórez Miguel et al., La ciencia del cielo.

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robosco’s introduction to astronomy in its official curriculum. But the staggering knowledge of astrology at fourteenth-century Merton College indicates that “those with a particular interest in the subject developed their art by private research and discussion.”44 This last comment illustrates an interesting difference between Italy and northern Europe in the academic teaching of astrology. While the statutes of Italian faculties of arts and medicine include elaborately detailed astrological curricula, it is much more difficult to get a clear sense of what was taught, when, and by whom, on the other side of the Alps. Although it is clear that the distinction between “motions” and “judgments” of the stars informed northern European teaching, it is much more difficult to trace the distinction between theorica and practica. This does not seem to reflect a difference in what was taught. Even a sophisticated vernacular text like Geoffrey Chaucer’s Treatise on the Astrolabe contained both a “theorik” of the “moevinge of the celestial bodies with the causes” and the “general rewles of theorik in astrologie.”45 Instead, we may be dealing with an issue of visibility, related to differences in institutional organization. Most medical schools of northern Europe (unlike their Italian counterparts) were firmly separated from the local arts faculties. The latter mostly provided instruction in the introductory (and hence often “theoretical”) quadrivium. Accordingly, more advanced astrological lessons (comprising both “theory” and “practice”) were usually offered within the seat of the medical faculty. Although available, astrological instruction would have been organized either privately, or in the margins of official medical teaching. Another reinforcing factor was the predominance of theological faculties at northern universities. For instance, the Vienna statutes of 1389 emphasized how the new lessons of mathematics should be “useful to the service of the Catholic Church.”46 This survey discloses the basis for an acceptable description and definition of “astrology” within the framework of pre-modern higher learning. We encountered “astrology” as the “science of the stars,”

44 Carey, Courting Disaster, p. 53. On the development of scientific interests in fourteenth-century Oxford, see North, “1348 and All That.” 45 See Chaucer, Complete Works, vol. 3, p. 177. The context proves that Chaucer’s “astrology” indeed refers to the “science of judgments.” See North, Chaucer’s Universe, p. 46. 46 See Beaujouan, “Motives and opportunities for science,” pp. 221–223.

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covering both the “science of motions” and the “science of judgments.” Both comprised fundamental (emphasizing the “ideas” of a practice) and more derivative (emphasizing the “things” and “data” of a practice) components.47 Henceforth, I refer to a body of knowledge that emphasizes demonstration of the “science of the motions” as theoretical astronomy.48 The derivative techniques for calculating astronomical positions will be called practical astronomy. The demonstrative principles of the “science of judgments” are described as astrological physics in section 4.1. Finally, I refer to the practical derivatives of the “science of judgments” as judicial astrology.49 The transition to a suitable definition can be made under the guidance of Gervais Marstaller, who connected all of these elements in 1549. Marstaller asserted the validity of astrology: Because the celestial bodies exert some power over these sublunary bodies, and because that power can be predicted, or at least observed, under the guidance of Astronomy and of that art which we hence call Astrology.50

Paraphrasing Marstaller, I adopt the following definition of astrology: Astrology aims at predicting and/or studying the power of celestial bodies on earth, and measures their positions by means of astronomy.

4. The structure of the “science of judgment” Although our definition includes the essentials of astrological practice in pre-modern Europe, two elements of the “science of judgment” need further detail before we can proceed. This section attempts to fill those gaps.

47 Obviously, I do not intend to reify the distinction between “fundamental” and “derivative.” Nevertheless, one could argue that Western traditions of higher learning characteristically propose a demonstrative hierarchy between “ideas,” “things,” and “data,” where ideas occupy the highest rank. An excellent example is Lucio Bellanti’s discussion of the academic status of astrology (see section 6 of this chapter). Cf. Legowicz, “Le problème de la théorie.” 48 This was widely associated with Ptolemy’s foundational Almagest and the didactic theorica planetarum. 49 This fourfold subdivision agrees with the conclusions of Nicholas Jardine, who notes the recurring presence of the distinction between astronomy and judicial astrology on the one hand, and of theoretical vs. practical parts on the other, in astronomical textbooks. See Jardine, The birth of history and philosophy of science, pp. 225–226. 50 Marstallerus, Artis divinatricis (…) encomia & patrocinia, fol. b3r: “(…) Quod corpora caelestia habeant aliquam vim in haec inferiora, quodque vis ea praesidio

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4.1. Astrological physics The preceding section offered a fairly clear idea of the content and purpose of judicial astrology. But what did the theory of the “science of judgment” look like? Neither Ptolemy, nor Pietro d’Abano, provided as much as a name for this subdiscipline.51 Some clues can be gained from Ptolemy’s references to our elusive astrological theory. At the beginning of Tetrabiblos, Ptolemy referred to this as one of two preparatory disciplines. We know that the other preparatory discipline, astronomy, was treated separately in the Almagest. Finally, we know that Ptolemy only introduced his judicial astrology in the second book of Tetrabiblos. This makes it likely that the first book of Tetrabiblos prepared knowledge of astrological effects on earth independently of predictive interests. In other words, its content would constitute our astrological theory. This interpretation is confirmed by Ptolemy’s text. Following three introductory chapters on epistemology and methodology, the first book of Tetrabiblos enumerated the basic variables of the astrological art. These parameters include both well-known notions (planetary virtues, zodiacal signs, aspects, and even astrological houses) and more esoteric concepts (e.g., exaltations, terms, faces). Each parameter groups a limited number of celestial objects or regions that impart a specific virtue. For instance, there are seven planets, among which Mars has a natural tendency to “chiefly dry and burn.”52 There are twelve signs, among which Aries is equatorial, male, and commanding.53 Where possible, Ptolemy also provides a mathematical or empirical explanation for each of these effects. Ptolemy refers to this knowledge as the investigation of changes, brought about by the “physical quality” of the heavens. Interestingly, he preferred to express these causes in terms of the four Aristotelian sublunary qualities: hot, cold, wet, and dry. In view of Ptolemy’s consideration for the agreement between natural philosophy and

Astronomiae, & huius artis quae ob id Astrologia dicitur, possit praedici, seu quomodocunque observari (…).” 51 One should note Geoffrey Chaucer’s use of the word “introductorie” for the “statutz of oure doctors, in which thou maist lerne a gret part of the general rewles of theorik in astrologie.” See Chaucer, Complete Works, vol. 3, p. 177. Several popular textbooks of academic astrology in this period did carry the title Introductorium (e.g. by Alcabitius). However, their content seems much broader than anything Ptolemy or Pietro d’Abano had in mind. 52 Tetrabiblos, p. 37. 53 Ibid., pp. 67–71 and 75–77.

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astrology, I propose to use the term “astrological physics” for the content of Tetrabiblos, book i. In a late medieval academic context, this material provided the theory of astrological judgment. 4.2. Judicial astrology Pietro d’Abano distinguished astrological physics from the “practice of judgment,” which I henceforth call “judicial astrology.” D’Abano’s classifications illustrate the wide range of available applications for judicial astrology. Following his model, subsequent chapters distinguish between three forms of judicial practice, depending on the subject under consideration. Mundane astrology predicts events for the entire earth or large parts of it, natal or genethliacal astrology studies individual human beings, while questionary or horary astrology focuses on particular events in the life of individuals. This last field is further subdivided between elections (for the appropriate beginning of the event) and interrogations (for the outcome of the event).54

5. Astrology, natural philosophy, and secrecy 5.1. Astrology and natural philosophy One of the main reasons for emphasizing astrological theory, is the fact that its complex pattern of ideas and data overlapped with similar patterns in other academic practices. This section uncovers one of the most important areas of overlap: that between astrology and natural philosophy. Indeed, Ptolemy’s use of Aristotelian natural philosophy exerted a particularly strong influence on Western astrology. Thomas Aquinas, for instance, attributed celestial effects to the essences of celestial bodies. Saturn’s cold and dry powers, or Venus’ warm and hot effects, indicated that the planets were of different species in nature.55 This successful use of Aristotle’s natural philosophy as the theoretical foundation for astrology need not surprise us. Just as natural

54 The first two categories of my nomenclature should not pose any problems to those familiar with astrological literature. Laurel Means introduces the term questionary astrology to refer to “specific questions, who and how they are asked, and the means by which they may be answered” (“Categories of Prognostic Material,” p. 395). I depart from Means’ nomenclature by including elections under this heading. 55 See North, “Celestial Influence,” p. 278; Litt, Corps célestes, pp. 220–241.

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philosophy intended to explain natural change and continuity, so did astrology aim at predicting these phenomena. But their difference carried implications for much more than the chronological relation between knowledge and knower. As Dennis Des Chene remarks, Aristotle’s use of the term “nature” (as opposed to “essence” or “substance”) to discuss a substance implies a causal narrative where the cause is intrinsic to the substance. For a set of possible events that can happen to it, the “natural” substance has explanatory autonomy concerning the causes of those events.56 These are the events that occur “always” or “for the most part,” such as the cooling of hot milk. Since extrinsic coldness is often absent when this phenomenon occurs, one must assume that natural things tend towards a preferred qualitative state.57 Nature is the intrinsic principle that underlies this tendency. Ptolemy acknowledged the explanatory autonomy of at least animate sublunary beings: “Each seed prevails to express in general its own form, for example, man, horse, and so forth.”58 Nevertheless, he concluded his discussion of the importance of seed, local geography, and customs in sublunary generation, with the significant remark that: Unless each one of these things is examined together with the causes that are derived from the ambient, although this latter be conceded to exercise the greatest influence (for the ambient is one of the causes for these things being what they are, while they in turn have no influence upon it) …59

In this instance, Ptolemy claimed the primacy of celestial efficient causes over all sublunary change, including that of animate beings. Both his use of Aristotle’s four primary qualities and his discourse on celestial virtues, show that his astrological physics intended to provide knowledge of these primary causes. Both Nicole Oresme (c. 1320–1382) and Giovanni Pico later viewed astrological physics in the same way.60 One may interpret this attitude as a further development of Aristotle’s own remarks concerning the physical role of celestial bodies in On Generation and Corruption ii.10, where the sun’s annual motion around the ecliptic is mentioned as the efficient cause of continuous 56

Des Chene, Physiologia, p. 216. Ibid., pp. 73–75. 58 Tetrabiblos, p. 17. 59 Ibid., p. 19 (my italics). 60 Caroti, “Nicole Oresme’s Polemic Against Astrology in his Quodlibeta,” p. 82. Pico, Disputationes, vol. 1, p. 270. 57

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generation and corruption on earth.61 In Tetrabiblos, Ptolemy adds the other celestial bodies to this model in order to bring alteration and growth under the purview of superlunary efficient causality.62 The attractiveness of his astrological physics is evident: a universal and powerful predictive art lay ahead for those who could, and would, commit themselves to Ptolemy’s reductionism of sublunary efficient causes. Nor need one spell out the implications for natural philosophy: if successful, Ptolemy’s model would obliterate natural regularity from learned discourse by undermining the causal explanatory autonomy of natural things. For instance, those who wished to do so could still call milk essentially wet, cold, white, and sweet. But whether milk could maintain or attain that natural, preferred state at any given moment was dependent upon the heavens. Likewise, there was no inherent reason to assume that the model of “spontaneous generation” of imperfect animals (flies, frogs, fleas) through celestial causes could not be applied to higher life forms.63 5.2. Epistemic secrecy Ptolemy solved the discrepancy between this grand theoretical narrative, on the one hand, and allegations of modest practical success, on the other, by emphasizing the epistemic difficulties of astrology. In his opinion, the art could not aspire to factual certainty, because of the complexity of the underlying causal processes.64 Since it was impossible to disentangle the subtle web of proximate causes, one had to make do with a reasonable estimate of the universal efficient causes affecting a substance at a particular time and place. This model proclaimed its intellectual ancestry among farmers and herdsmen, who supposedly observed the variations of seasons and winds to predict the quality of their future crops or livestock.65 The high status of this “elite folklore” can be gathered from Cicero’s anti-astrological On Divination (c. 44 bc), where it appears under the respectful name of “rational prediction.” This shows how Ptolemaic astrology advocated the existence of “epistemic secrecy.”66 Its practice touched upon aspects of nature that 61 62 63

Aristotle, On Generation and Corruption 336a32–336b24. Tetrabiblos, pp. 7–9. See Thomas Aquinas on spontaneous generation in Litt, Corps célestes, pp. 130–

133. 64 65 66

Tetrabiblos, pp. 11–13 and 19. Ibid., p. 9. As an alternative to the term “epistemic secrecy,” one may choose to discuss the

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were unknown (“secret”) for practical and historically contingent reasons.67 However, the aforementioned tension between astrology and Aristotelian natural philosophy over the issue of reductionism, illustrates how even Ptolemy thought that the factual uncertainty underlying “epistemic secrecy” could be overcome. 5.3. Epistemological secrecy The Latin West also inherited astrological traditions that rejected Ptolemy’s epistemic secrecy. Their narratives can be traced back to Mesopotamian astral religion, where stars and planets were identified with so-called “great gods.” Such worship of the heavenly bodies was paired with divination through the scrutiny of their motions and positions.68 This tradition’s anthropomorphic interpretations of the heavens gained prominence in non-Ptolemaic ancient astrology. From there, it was passed on to the Latin West by predominantly Roman and Arabic intermediaries.69 The most popular of these works were attributed to Julius Firmicus Maternus (fl. 334–337), Messahala (fl. 762–c. 815), Omar Tiberiadis (d. c. 815/6), Zael (d. between 822 and 850), al-Kindi (d. c. 873), Albumasar (787–886), Albohali (fl. 854?), Alcabitius (fl. after 950), Haly Abenragel (fl. 1030–1040) and Haly Avenrodoan (988–1061/9), and were supplemented with compilations like the Liber novem iudicum.70 Albumasar, perhaps the most influential of these authors, illustrates the specific problems that this alternative tradition spawned. Even more than Ptolemy’s Tetrabiblos, it was Albumasar’s Introductorium maius that connected Aristotelian physics to astrology.71 This

“stochastic nature of astrology.” 67 This taxonomy of secrecy is taken from Eamon, Science and the Secrets of Nature, p. 11. 68 See Dhorme, Les religions de Babylonie et Assyrie; Pingree/Hunger, Astral Sciences in Mesopotamia; Pingree, From Astral Omens to Astrology, pp. 11–38; Pingree, “Mesopotamian Astronomy and Astral Omens.” 69 See d’Alverny, “Translations and Translators”; Burnett, “A group of Arabic-Latin translators”; Burnett, “Mathematics and Astronomy in Hereford”; Burnett, “King Ptolemy and Alchandreus the Philosopher”; Reichel, Astrologie, Sortilegium. 70 An excellent and brief introduction is Fahd, “Nudjum (Akham Al-)” in: Gibb et al. (eds.), Encyclopaedia of Islam, vol. 7, pp. 105–108. To be supplemented with Nallino, Raccolta di scritti editi e inediti, vol. 5; Regourd, “Astrologie. Islam”; Fahd, La divination arabe; Sezgin, Geschichte des arabischen Schrifttums, vol. 6: Astronomie and vol. 7: Astrologie – Meteorologie. 71 This is emphasized in Lemay, Abu Ma’shar and Latin Aristotelianism.

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was combined, however, with an account of sublunary generation that fully explained individual traits within a species through celestial causes.72 The latter existed as: (…) the distinction and distance of one genus from another, one species from another, one individual from another, as the harmony of soul and body, and of innumerous other accidents like sex, the distinction in form and habit, beauty or turpitude, the inequality of stature, various colors and mores, and similar things.73

From a modern perspective, one might assume that only cloning would have met Albumasar’s criteria for non-astrological sublunary generation; at any rate, it should be clear that this tradition endowed celestial virtue with virtually unlimited power over both body and soul.74 The relevant conclusion of the Introductorium maius was unambiguous in this respect: Just as the planets signify what is possible and what a man can choose, so by the same token they signify that a man will not choose but what the planets had signified, because his choice of a matter and its contrary is done by the rational soul, which comprises the vital souls of individuals through planetary significations.75

Albumasar’s astrological physics simply obliterated the notion of “epistemic secrecy.” Terrestrial individuality could be fully explained through an inscrutable combinatorics of celestial influences. Astrologers did not contradict the reality of regular sublunary events, but minimized their relevance for an authentic understanding of the natural world. This reminds one of Aristotle’s suggestion that the distinction between regular and irregular events was rooted in common opinion, which he ascribed to the “wise men of old.”76 By implication, astrology’s public flirtation with the prediction of chance events threatened to upset shared ideas of natural kinds, and the social ordering that these represented.

72

North, “Celestial Influence,” pp. 250–255. Albumasar, Introductorium (1489), fol. a7r. 74 Lemay, Abu Ma’shar and Latin Aristotelianism, p. 126. 75 Albumasar, Introductorium, Paris bn ms. lat. 16204, fol. 21: “Et sicut planete significant possibile atque electionem quod est hominis, similiter significant quod homo non eliget nisi quod significaverint planete, quia electio eius ad rem et eius contrarium fit per animam racionalem que complectitur anime vitali in individuis per significationes planetarum.” Latin passage quoted in Lemay, Abu Ma’shar and Latin Aristotelianism, p. 128 note 4. 76 Aristotle, Physics 196a1–17. 73

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Medieval authorities developed several strategies to resolve this tension. One of these replaced epistemic secrecy by epistemological secrecy. Contrary to its epistemic counterpart, epistemological secrecy espoused the conviction that certain natural phenomena were essentially unknowable.77 These arcana naturae were often rationalized through the notion of occult qualities.78 Since the human mind could not distinguish such qualities from the essence of a substance, it was unable to isolate or understand their operation as accurately as that of the primary qualities.79 One could perceive occult effects or qualities in the presence of a certain substance, but could not understand its actual mode of operation.80 This explanatory category was eminently suited to explain –and justify- the attribution of specific virtues to the heavens (e.g., Taurus’ effect on cattle).

6. Lucio Bellanti’s De astrologica veritate (1498) The preceding analysis shows how the relation between astrology and Aristotelian learning could lead to either support or suspicion. The latter option manifested itself in times of widespread unrest over astrological predictions. An instructive example comes from the Italy of the 1490s, where Giovanni Pico’s refutation of astrology countered an exceptionally widespread interest in mundane astrology (see chapter 3). This provided inspiration for several academic apologists, who turned to Aristotle’s epistemology and natural philosophy to defend the scientific status of astrology. This section explores what was perhaps the most influential of these defenses: the De astrologica veritate by Lucio Bellanti of Siena (1498).81 Lucio Bellanti (d. 1499) was a professor of medicine and astrology at the Sienese studio, who attained local notoriety through his involvement in the troubled Sienese politics of the 1490s.82 He opened his attack on Pico with a “question on the science of astrol77

Once again, I borrow my taxonomy of “secrecy” from Eamon, Science and the Secrets of Nature, p. 11. 78 For an exemplary study of the history of another occult virtue, see Copenhaver, “A Tale of Two Fishes.” 79 Hutchison, “What Happened to Occult Qualities,” pp. 91–93. 80 One textbook example of an occult quality was the attractive virtue of the magnet. 81 For the suggestion that the editio princeps of De astrologica veritate came out in in 1499 only, see Bühler, “The Date of the Florentine Incunable.” 82 On Bellanti, see Vasoli, “Bellanti, Lucio.”

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ogy,” which contained five articles that discussed the possibility of astrological prediction, its status as a science, its theoretical or practical nature, its nobility and utility.83 Reflecting a typically academic concern with the demarcation and interrelatedness of learned disciplines, these questions provide an excellent starting-point to position astrology more accurately in the late medieval university. Bellanti’s article on the scientific status of astrology wasted no time in pointing out the essential problems. First, was astrology based on commonly accepted principles? Second, could it establish a clear connection between cause and effect? Third, did it provide certain, “perfect” knowledge? Fourth, did it deal with knowledge about universal facts?84 These Aristotelian concerns were, of course, ubiquitous in late medieval academic life. First, Posterior Analytics i.2 (71b19–33) requires that the premises of a science be true, primary, indemonstrable, explanatory, prior, and more intelligible in themselves.85 Ideally, these should posit facts as essential connections between an effect and a cause (i.e., provide “knowledge of the reasoned fact”).86 The second objection reminds us that it was unclear whether the principles of astrology satisfied these requirements. Third, such an explanation has to follow a strict syllogistic logic, described in Aristotle’s Prior Analytics. Fourth, Aristotle famously posited that particular historical experiences could not provide factual premises, since one singular experience (or, in fact, any definite number of them) could not be reliably held to represent the normal course of nature. Instead, “facts” or “experiences” were intellectual constructs, acquired by the accumulation of individual observations in the memory through a process of “induction” (‰παγωγÜ).87 A similar process underpins the subsequent transition to “reasoned facts,” which typically result from a noetic investigation (negotiatio) of facts.88 In Bellanti’s opinion, astrology was indeed a science. Since every science disposed autonomously of its fundamental premises, the appropriateness of astrology’s premises could not be settled outside the discipline. Bellanti claimed that astrological facts were the result of a long empirical tradition. Moreover, its factual knowledge was often 83

Bellanti, De astrologica veritate (1502), fols. a1r-b1v. Ibid., fol. a3r/v. 85 Hankinson, Cause and Explanation, pp. 160–161. 86 Aristotle’s most famous example distinguishes between the false fact that “the planets are near because they do not twinkle” and the true fact that “the planets do not twinkle because they are near” in Posterior analytics i.13. 87 See Aristotle, Posterior analytics ii.19. 88 Jardine, “Epistemology of the Sciences,” pp. 686–693. 84

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related to three general causes: celestial motion, light, and occult influence.89 The worth of astrology’s “logic of demonstration” was initially proved by the following example of a syllogistic prediction: Anyone with a geniture having Mercury in the house of Mars, and Aries in the ascendent, is loquacious; Sortes has this sort of geniture; Hence, Sortes will be loquacious.90

For all their theoretical elegance, such demonstrations obviously did not agree with the empirical evidence that many people with a similar geniture were not loquacious. Bellanti pre-empted this objection by qualifying his syllogisms as reasoning ceteris paribus or “ex suppositione” (the supposition being that no material, fortuitous, or voluntaristic impediments would intervene).91 Bellanti also expanded this status from general astrological facts to the particular observations (“Mercury enters the house of Mars on 26 February 1498”) of the practising astrologer, pointing out that these could be considered as instantiations of general experiences, even if this was not always done in practice.92 It seems significant that Bellanti, following common Aristotelian mathematical discourse, referred to these generalized facts as “abstractions”: in fact, he explicitly classified astrology as one of the mediae scientiae or “mixed mathematics” (along with optics and music) between mathematics and natural philosophy.93 These disciplinary connections were clarified in Bellanti’s section on the theoretical vs. practical nature of astrology. Bellanti explained that the interpretation of a discipline as either speculativa (aiming at an internal effect) or practica (aiming at an external effect) was largely dependent on one’s criteria. Astrology, for instance, was best considered a practical discipline in terms of its goals, since it teaches the operational means by which “we can augment good and diminish evil.” Bellanti identified this as the proper subject matter of many parts of predictive astrology, although some parts of astrology 89

Bellanti, De astrologica veritate (1502), fols. a4r-a5r. Ibid., fol. a4v. 91 Ibid., fols. a5r and b1v. On reasoning “ex suppositione” and Renaissance science, See Wallace, “Aristotle and Galileo: the uses of ΥΠΟΘΗΣΙΣ (suppositio) in scientific reasoning.” 92 Bellanti, De astrologica veritate (1502), fol. a5r. 93 Ibid., fol. a4v. On the mixed mathematical sciences (scientiae mediae, chiefly optics, harmonics, and astronomy), see especially Lennox, “Aristotle, Galileo, and ‘Mixed Sciences”’; Mandioso, “Entre mathématiques et physique”; Bennett, “The Mechanics’ Philosophy and the Mechanical Philosophy.” 90

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were strictly theoretical, “such as the theorica planetarum and other things of this kind.”94 Only these last parts, he added, could be considered speculative knowledge, even if this label was only properly given to metaphysics, natural philosophy, and mathematics. Bellanti’s De astrologica veritate illustrates the Janus faces of late medieval astrology. It proudly promoted an ancient tradition of sophisticated practice, where ambitious epistemic ideas, highly specialized instruments, and complex data collections interacted to produce predictions of the future. But this tradition was also able to express itself in the less esoteric conventions of school learning when its predictions were viewed with suspicion. This book tells the story of a community of astrological practitioners who sought out different conventions when they were confronted with similar suspicions. In doing so, they pushed their tradition beyond its previous boundaries, and did so beyond public recovery.

94 Bellanti, De astrologica veritate (1502), fol. a5v: “Itaque dico partem astrologie practicam esse, quum doceat operandi modum, quo bonum augere malum minuere possimus, iuxta ptolemei scientiam verbo .v. libri fructus: sicut est pars electiones docens, multeque alie partes in pronosticatrice astrologia. Partem vero sic non esse practicam, sicut planetarum theorica, & alia huiusmodi.”

CHAPTER TWO

ASTROLOGY AND LATE MEDIEVAL ACADEMIC CULTURE. LOUVAIN, 1425–1516

A request for the foundation of a new university at Louvain (submitted by Duke Jan iv of Brabant, the Louvain town authorities, and the local chapter of St. Peter) was approved by Pope Martin v in 1425. It seems likely that the initiative originated (at least in part) in an attempt to reverse the struggling local economy, by preventing the outflow of local students and attracting foreign funds. Accordingly, we find that the Louvain town council diligently covered most of the new university’s expenses.1 Standing at the end of the first wave of German university foundations in the Middle Ages (1348–1425), the new university flourished beyond expectation, and remained the only academic institution of the Low Countries until 1562.2 Its success largely followed the increasing preference for university graduates in administrative positions across the Low Countries. University-trained jurists dominated the chancery of Flanders by the end of the fourteenth century. Most members of the provincial council of Brabant held academic degrees by the middle of the fifteenth century. It is estimated that over seventy percent of Brabant town officials were university graduates in the fifteenth century.3 This particular valuation of university learning in the southern Low Countries was not limited to the study of law. Jeroen Salman has shown how local and regional governments in the Dutch Republic bought thousands of “almanacs” with astrological predictions each year. They were freely distributed, both as sources of information

1

Van Eijl, “The Foundation of the University of Louvain,” p. 33. On the periodization of German university foundations, see Schubert, “Motive und Probleme,” pp. 13–78. The university of Douai (essentially a local outpost of Louvain) started teaching in 1562, while the northern provinces erected an independent university at Leiden in 1575. 3 De Ridder-Symoens, “Possibilités de carrière et de mobilité social,” pp. 349–352. 2

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and as public-relations gifts.4 The same pattern can be discerned in the southern provinces of the late fifteenth and early sixteenth centuries.5 This chapter investigates the active promotion of academic astrology in fifteenth-century Louvain by the Burgundian court and local town council. It details the various occasions when academic astrologers were consulted, and the impact of this public interest on the relations between the various disciplines that were taught at Louvain.

1. Academic astrological genres This section introduces late medieval academic astrology at Louvain through the work of one of its main practitioners: Joannes Vesalius (c. 1401–1476), great-grandfather of the anatomist Andreas Vesalius. Having obtained his ma at Cologne in 1424, Joannes van Wesele or Vesalius continued his studies at Pavia, where he was proclaimed master and doctor in medicine on 23 January 1427.6 In 1429, Louvain recruited him for its recent medical faculty.7 Vesalius remained at Louvain (with occasional visits to his native Wesel in the duchy of Cleves) until at least the end of the academic year 1442–1443.8 By 1454 he had moved to Brussels, where he is listed the following year as town physician.9 All available evidence indicates that he remained there until his death in 1476.10 1.1. Annual almanacs Several genres dominated academic astrological practice in the late Middle Ages. One of the most popular was the so-called almanac. 4

Salman, Populair drukwerk, pp. 334–344. Ibid., p. 219. 6 Meulemans, “Wesaliana,” p. 16; Belloni, “Joannes de Vesalia,” p. 69. 7 Reusens, Actes, vol. 2, p. 98. 8 Lefebvre, “Les sciences,” p. 48, states that Vesalius taught at Louvain until 1445– 1446. However, the Louvain town archives do not yield conclusive evidence of Vesalius’ presence after 1442–1443 (see Meulemans, “Wesaliana,” p. 19). 9 Belloni, “Joannes de Vesalia,” p. 78; Meulemans, “Wesaliana,” pp. 9, 22. Vesalius probably left for Brussels in 1453, when Joannes Spierinck succeeded him at Louvain. 10 His son Paul was matriculated as inhabitant of Brussels in 1469: see Reusens et al. (eds.), Matricule, vol. 2, p. 221, nr. 203. Vesalius is mentioned again as town physician of Brussels in 1471. His estate was split up there in 1476 (Meulemans, “Wesaliana,” p. 32). 5

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In its most restricted form, this genre was almost equivalent to our “ephemerides,” providing the astronomical positions of celestial bodies for a determinate period of time, usually a year.11 Sometime around the end of 1430, the town council of Louvain instructed Johannes Vesalius to compose an almanac for 1431. Vesalius complied and publicly read his predictions in the university hall before New Year’s Day. Other entries show that Vesalius made similar almanacs for the town in 1439 and 1440. Presumably, he did so during his entire career at Louvain University.12 The court of Duke Philip the Good (1419–1467) also appreciated Vesalius’ astrological skills, since the latter presented at least two different almanacs to the Duke. In 1432, Vesalius was rewarded for both a “grant” and “petit” almanac. In 1459 only a “grant almanach” was offered, which included “les jours esleuz,” the propitious days for bloodletting and purging.13 The term was probably qualified according to the amount of astronomical data that was incorporated: a “grant almanach” took into account the positions of all planets, while the “petit almanach” limited itself to considering the phases of the moon.14 This suggests that the almanac originally belonged to the astronomical component of academic astrology. This information was occasionally paired with medical information, as is the case in an astro-medical calendar by the Louvain professor Joannes Spierinck, printed in 1483/4.15 In its preserved form, this unique copy consists of a one-page medical calendar for the year 1484, listing the day, hour and minute of full and new Moon as well as the propitious days for performing venesections and purging. Since these constituted the quintessential data of late medieval astrological medicine, there is good reason to assume that this broadsheet was published primarily as a physician’s tool. The practice of the “science of motions” and the “science of judgments” was not clearly separated in fifteenth-century Louvain. This is confirmed in the Louvain town records, which specify that Vesalius’ annual almanacs were combined with “additional things that will happen in the following year.” This description reminds 11 Poulle, Les sources astronomiques, pp. 64–66; Berckmoes, “Bijdrage tot de studie van de almanak.” 12 See Meulemans, “Wesaliana,” p. 25. 13 Quoted in Abel/Martens, “Le role,” p. 46 note 1. 14 See Jacquart, La médecine médiévale, pp. 451–452. 15 See Elly Cockx-Indestege, “Jan Spierinck. Almanack pro anno 1484” in: Vijfhonderdste verjaring, pp. 387–389.

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one of the tacuinus, a common astrological genre at late medieval Italian universities. A document, written at Bologna around 1500, states that: Of those entrusted with the lectureship in astronomy [astronomia], one should compile a judgement on the annual revolutions of the planets, and the other (should compile) the tacuinus proper. This tacuinus should show the motions of all the planets for each day of the year in signs, degrees and minutes. It should also give all the aspects of the planets to the moon and to each other, as well as the dates of Sundays and feasts throughout the year.16

This suggests that the Bolognese studio clearly separated astronomical from astrological practice. At least since the last quarter of the fifteenth century, however, astrological judgment and astronomical tacuinus coalesced into a single text.17 A similar elision of astronomical data, medical prognosis, and astrological judgment seems to have occurred in the Louvain almanacs of the fifteenth century. This eventually resulted in an entirely new genre: the annual prognostication. 1.2. Conjunctions and comets In 1472, Vesalius composed a treatise on a comet that had appeared on 13 January in the sign of Virgo.18 Although the preserved text does not explicitly mention its dedicatee, several references indicate that it was written for Charles the Bold, Duke of Burgundy since 1467.19 This treatise confirms that the Dukes of Burgundy regularly drew upon Vesalius’ astrological expertise, and that they did so both in his role as Louvain professor and as Brussels town physician. Although all of Vesalius’ extant predictions concern mundane astrology, there is scant evidence that he may have cast genitures for these patrons as well.20 In this extant treatise, Vesalius refers to another tract on the generation of comets that he had previously written, possibly on the 1457 comet. Apparently, his interest in the topic was not occasional.21 Vesalius also composed a prognostication on the Saturn-Jupiter conjunction of 1464, which perished in the 1940 fire of the munic16

Reference and translation taken from Clarke, Giovanni Antonio Magini, p. 193. Clarke, Giovanni Antonio Magini, pp. 194–195. See also Dallari, I rotuli dei lettori legisti e artisti dello Studi Bolognese dal 1384 al 1799. 18 See Abel/Martens, “Le role,” for a discussion and edition of Vesalius’ treatise. 19 See Abel/Martens “Le role,” p. 54 note 1. 20 See § 30: “Libra verissime in nativitate principantis nostri ascenderat” (Abel/ Martens, “Le role,” p. 86). 21 Abel/Martens, “Le role,” p. 72. 17

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ipal library at Tournai. However, I have been able to establish that an astrological judgment, published by Kervyn de Lettenhove from an unspecified source in the 1860s, is probably identical to the lost Tournai document.22 Upon closer inspection, its text reveals a great deal of propaganda for the Burgundian dynasty, as the following section shows.

2. The uses of academic astrology 2.1. Academic astrological consulting: Louvain and the Burgundian court In his Recueil, Simon de Phares related that Vesalius’ successor Joannes Spierinck provided Charles the Bold with astrological advice on his war against the Swiss.23 This suggests a continuous tradition of Louvain physicians providing the Burgundian court with astrological services. Astrological academic consulting was rather common at late medieval courts, as previous studies on the Habsburg, French, and English courts have shown.24 We will later show how these consul22 A dossier on the lost manuscript prognostication was compiled in Abel/Martens, “Le role,” p. 46 note 2. The text that Kervyn de Lettenhove published from an unspecified source (but which he did date to 1454) is included in Oeuvres de Georges Chastellain, ed. Kervyn de Lettenhove, vol. 3, p. 447. Internal evidence from Vesalius’ use of the cycle of great conjunctions proves that this prognostication concerns the 1463/4 conjunctions of Mars, Jupiter and Saturn. Vesalius implicitly dates the published text to “Lustra ducenta quinquagintaque trina,/ Postquam terrena conjuncta fuere supernis” at the very end of this prognostication. Interpreting this as “two hundred lustra (periods of five years) and fifty trina (periods of three years) after the higher planets were conjoined earthly,” we can assume that Vesalius refers to “1150 years after Saturn and Jupiter were last conjoined in an earthy sign.” If we follow the mediaeval practice of calculating with mean rather than true conjunctions, Saturn and Jupiter conjunctions occurred in the earthy triangle between 54 ad and 293 ad. This means that a shift of triplicity (from the earthy to the airy triangle) happened in 313 ad, which in mediaeval astrological usage would mark the date when such conjunctions ceased to occur in an earthy sign. 1150 years after 313 ad gives us 1463 ad, which agrees well with a conjunction of Saturn and Mars in 1463 ad and one of Saturn and Jupiter in 1464 ad. I have used a table of mean Saturn-Jupiter conjunctions that was compiled by Keiji Yamamoto (Sangyo University, Kyoto) and kindly placed at my disposal by the author. 23 See De Phares, Recueil, ed. Wickersheimer, p. 263. 24 For Vienna, see the excellent article by Shank, “Academic Consulting,” from which I borrow the term ‘academic consulting.’ Many studies have been devoted to astrology at the French courts. For a useful list of masters of the Paris medical faculty who provided astrological consulting to the French royal court, see Jacquart, “Médecine et astrologie,” p. 127 note 24. An interesting provisional synthesis of some aspects of medieval French court astrology is provided in Boudet, “Les astrologues

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tations assumed propagandistic functions with the advent of printed annual prognostications in the 1470s. The university, town council and Burgundian court each solicited both medical and astrological services from Vesalius and Spierinck.25 We also know that Vesalius was among the doctors assisting Philip the Good’s ailing son Anthony in 1432, while Spierinck was paid several times for medical services to the Duke in the early 1460s.26 This does not imply that these three environments shared a similar perception of their professional competence and identity. Even when their mathematical or astrological competence was discussed, the university consistently referred to Vesalius, De Vettere, and Spierinck as physicians. Although the town council shared this language, its active interest in the continuity of mathematical instruction (see later) and desire to obtain annual almanacs indicate a substantially greater interest in astronomical and astrological services. The broadest range of options for an astrologer-physician seems to have been available at court.27 When Joannes Vesalius made his first entry at the court of Burgundy, he complemented a well-established body of astrological counselors, probably headed by Henry Arnaut of Zwolle, personal physician to Philip the Good.28 While the earliest reference mentions Arnaut as the Duke’s “professeur en médecine,” subsequent passages in the ducal accounts also identify him as “astronomien” or “maistre en médecine et astrologie.” Such nomenclature was quite unconceivable for a physician at Louvain. Henry Arnaut of Zwolle also stands out by the actual extent of his astrological and astronomical roles. These included the casting of horoscopes for the Duke in 1431, as well as the construction of at least one, and possibly two, elaborate astronomical clocks between 1447 and 1455. Abel and Martens have suggested that Vesalius’ court astrology served the Dukes as political advice or propaganda. This is certainly

européens et la genèse de l’Etat moderne.” Also see Carey, “Astrology at the English Court.” 25 So far, no evidence for individual astrological consultations among the broader urban population of the Low Countries in this period seems to have surfaced. For a spectacular example of such consultations in fifteenth-century London, see Page, “Richard Trewythian and the Uses of Astrology.” 26 On Vesalius, see Bonenfant-Feytmans, “Les ancêtres d’André Vésale,” p. 101 note 9; The payments to Spierinck are quoted in de Laborde, Les Ducs de Bourgogne, vol. 2.1, p. 477 (1860), p. 478 (1862), p. 481 (1873). 27 Cf. Boudet/Charmasson, “Une consultation princière en 1427”; Poulle, “Horoscopes princiers.” 28 On Henry Arnaut of Zwolle, see now Veenstra, Magic and Divination, p. 129.

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confirmed by his astrological poem on the 1464 conjunction of Saturn and Jupiter. The content of this text stands out as a direct response to the political troubles of that time.29 The succession of Charles the Bold had become a topic of serious consideration in the first half of 1462, when his father Philip the Good was confined to bed for four months.30 While the Duke was ailing, chancellor Rollin (1376–1462), the pivot of Burgundian politics for over fourty years, died. Charles himself is the object of a failed assassination plot, which he attributes to his political opponents, the Croÿ family. And in the autumn of 1463, his relationship with Philip took a serious downfall when the latter withdrew his pension for political reasons. In September, the French King Louis xi (1423–1483) had succeeded in acquiring Picardie and the cities of the Somme region, on the terms of the 1435 Treaty of Arras. While this gained Philip the astronomical sum of 400,000 écus, it also made him lose a strategic buffer against potential invasions in Artois. Charles’ vehement opposition to this development temporarily estranged him from his father. By the beginning of 1464, the old Duke and his son were reconciled and became close political allies, to the detriment of the Croÿ family. At the Etats-généraux held in Brussels in April 1464, Charles was appointed leader of a Burgundian army in order to regain what was lost the year before, through a Guerre du Bien public waged against the French king. The similarity between the final lines of Vesalius’ prognostication, and the contemporary political developments at the Burgundian court, are obvious. Vesalius’ references to a “wise lord” and “new king” seem to concern Charles the Bold, whose political vicissitudes were ordained by the stars, only to be overcome and to be followed by “a better reign over the world.”31 The political relevance of this document is also highlighted by the references to religious issues. Just as the Edict of Milan (313) had inaugurated the unity of Christendom and Roman Empire, so its gradual disintegration had become undeniable with the fall of Constantinople in 1453. Philip the Good recorded his particular interest in the liberation of the Holy Land in the 1431 statutes of his

29 On the authority of ps.-Ptolemy’s Centiloquium 13, Vesalius later connected the signification of the 1472 comet to the changes he had previously predicted from the Saturn-Jupiter conjunction of 1464. See Abel/Martens, “Le role,” p. 71. 30 These general comments are based on Vaughan, Philip the Good; Idem, Charles the Bold. 31 Oeuvres de Georges Chastellain, ed. Kervyn de Lettenhove, vol. 3, p. 447.

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famous Order of the Golden Fleece.32 The Banquet of the Feasant (1454) marked the beginning of a period in which the Order made preparations for a veritable crusade. After a decade of vacillating, the Burgundians joined the expedition that Pius ii and the Venetians had planned for departure on 1 May 1464. But the crusading plans were called off after the death of Pius, and subsequently became a hollow token of Charles the Bold’s political allegiances. The crusading fervor of the period in which Vesalius composed his prognostication, probably forms the background to Vesalius’ explicit (“the ceders of Lebanon,” “the faith of his kingdom”) and implicit (the astrological link between 313 and 1463) references to religious policy.33 2.2. The importance of being printed: patronage, secrecy, and censorship The Burgundian court frequently called upon the consulting services of Louvain astrologers in times of severe political distress. It is important to realize that these services were usually provided under private circumstances. In addition to epistemic and epistemological forms of secrecy, “social secrecy” or the intentional concealment of information seems to have regulated the distribution of astrological consults.34 Two forms of social secrecy were readily apparent in the previous examples. On the one hand, we encountered material secrecy in the limited distribution of manuscript consultation reports. On the other hand, we found an example of semantic secrecy in Joannes Vesalius’ use of poetic language, when discussing the Saturn-Jupiter conjunction of 1463/4. Some Louvain astrologers began to abandon the practice of social secrecy around the middle of the 1470s. This fundamental change was intimately connected with the introduction of print technology. Jan van Westfalen (d. after 1501), probably the first printer to settle in Louvain, enrolled on 7 June 1474, and finished the oldest printed Louvain book there on 9 December.35 About one year later, he also started to print annual prognostications by a certain

32 On the Order of the Golden Fleece and Philip’s crusading plans, see Paviot, “L’ordre de la Toison d’Or et la Croisade,” pp. 71–74. A more complete treatment of this topic is Müller, Kreuzzugspläne. 33 On the “cedars of Lebanon,” see Lerner, The Power of Prophecy. 34 This notion is borrowed from Eamon, Science and the Secrets of Nature, p. 11. 35 On Jan van Westfalen and the history of early Louvain printing, see now Coppens, Wieg van de boekdrukkunst.

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Joannes Laet (d. 1487). Westfalen’s workshop at least issued Laet’s prognostications in 1476, 1478, 1481 and 1485.36 Although very little is known about Joannes Laet, he seems to have been regularly consulted by two prince bishops of Liège, Louis de Bourbon (1477–1482) and Jean de Hornes (1484–1505). Laet worked and lived at Louvain in 1486, where his son and successor Gaspar Laet began his academic studies in 1479.37 Joannes Laet seems to have been in good standing with the university’s own physician-astrologers. He inserted a complimentary reference to Joannes Spierinck’s 1464 prognostication in his own printed prognostication for 1485.38 Another prognostication, published in 1491 by his son Gaspar Laet, was dedicated to William Schevez (d. 1497), who trained under Spierinck in the late 1460s and early 1470s.39 Joannes Laet was yet another astrological consultant from Louvain, but without the qualification of being a medical professor. There was something different about Joannes Laet’s printed “annual prognostications.”40 In his dedicatory letters, Laet frequently qualified certain statements with the terms confessum (admitted) and secretum (secret). The 1476 prognostication referred to his revolutions of princely nativities as a secretum celatum (hidden secret).41 In 1485, Laet bragged that his unique knowledge of the times of coronations and births of European princes was a secretum celatum et confessum (hidden and admitted secret) that should not be revealed 36 I thank Dr. Elly Cockx-Indestege, who kindly allowed me to use her unpublished list of printed prognostications by the Laet family, the result of meticulous research in hundreds of libraries worldwide. 37 See J.J. Thonissen, “De Laet (Jean)” in: Biographie Nationale, vol. 5, pp. 273– 274. Joannes Laet dedicated his prognostications for 1476 and 1479 to Louis de Bourbon, and his prognostication for 1485 to Jean de Hornes. A manuscript of the prognostication for 1476 specifies that “Iste Iohannes Laet moratur Lovanij in die ridder strate.” See Laet, Pronosticationes (Brussels, Royal Library, ms. 1109), fol. 136v. Gaspar Laet matriculated at Louvain on 16 March 1479: “Jaspar Laets, in art., Leod. dyoc..” See Reusens et al. (eds.), Matricule, vol. 2, p. 393, nr. 9. One of Joannes Laet’s neighbors in the “Ridderstraat” was the printer Joannes de Westfalia, who habitually printed Laet’s Louvain prognostications. See Uytterhoeven, Leuven Weleer, vol. 6, nr. 10b. 38 Laet, Pronosticatien (…) 1485, fol. 1v. 39 Laet, De eclipsi solis (1491). A copy of this prognostication is preserved in Edinburgh, Royal Observatory, and probably stems from the collection of William Schevez. The prognostication was printed by Joannes de Westfalia, but does not bear any explicit mark of its provenance. 40 Cf. Berckmoes, “Bijdrage tot de studie van de prognostikaties.” 41 Laet, [Pronosticationes pro anno 1476], fols. [1r/v].

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to the masses.42 His analysis of the prince bishop’s horoscope for that year revealed a slight problem in his left chest, which “along with many other reasons, indicates particular things.” Laet left these particulars confessum et secretum (admitted and secret). De Hornes’ future benevolence towards the city of Liège, on the other hand, was made confessum (admitted). On the one hand, there is a clear continuity with previous traditions of astrological consulting in Laet’s prognostications. More specifically, they completed the gradual conjoining of practical astronomy and judicial astrology at Louvain (see section 2.1). On the other hand, there was a difference in the publication and distribution of this private knowledge through the printing press. Publishing consults with political relevance was a dangerous enterprise. Nevertheless, we find that the court of Liège actively supported Laet’s prognostications. His dedications consistently thanked Louis de Bourbon or Jean de Hornes for their beneficence and interest. How can we solve this contradiction? By assuming that the transposition of private knowledge into the public domain simultaneously changed its message. Astrological consulting privately unveiled the princely future. Astrological patronage, however, publicly unveiled the prince’s control over future events. Joannes Vesalius’ consults on the 1464 conjunction or 1472 comet were private pieces of advice. Joannes Laet’s prognostications, on the other hand, were public tokens of princely power. Complete openness was not an appropriate ideal for the demonstration of this power. This would have turned Laet’s predictions into verifiable statements, thereby detracting from the patron’s status. Predictions were useless under complete openness, regardless of whether they turned out to be correct or false. Instead, predictions achieved their status as tokens of princely power by suggestion. In line with this maxim, Laet adopted a rhetoric that alternated between (social) openness and secrecy. Some things (confessa) were shared in public, while others (secreta) were reserved to the inner sanctum of the court. Obviously, this rhetoric could only work after Laet had established his expertise as a prognosticator. He deployed three tactics to prove his credibility: inserting reports of recent predictive success, mentioning textual authorities, and unveiling details of the celestial charts that were used. This strategy seems to have been quite suc42

Laet, Pronosticatien (…) 1485, fol. 1r: “Ende die revolucien der gheboerten der hogher princen, dits secretum celatum et confessum.”

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cessful. In the 1510s, a chronicler from Liège still marveled at Laet’s remarkably accurate prediction for the year 1482.43 The successful alternation of openness and secrecy was a difficult game. Once it entered the public domain, the meaning of predictions became difficult to control, and printing made this only harder. A curious episode in 1478 illustrates how Joannes Laet experienced this first-hand. The event is briefly referred to in the Historiae Lovaniensium of Joannes Molanus (1533–1585), who references the lost volume 4 of the Louvain Acta Universitatis. Quoting a decision of the academic council, Molanus wrote that: In the year 1478, the University prohibited printers from printing almanacs with this addition: printed at Louvain. From the Acta.44

The reference to 1478 seems to be based on the original fifteenthcentury university records. Turning to Joannes Laet’s prognostications, we find that the last indication of Louvain as their place of origin indeed occurred in the prognostication for 1478. In 1479, Jan van Westfalen preferred to publish a prognostication by the Italian astrologer Hieronymus de Manfredis, rather than the predictions that Laet usually provided.45 This shows that the academic censorship on printed Louvain “almanacs” did take effect. The motives behind the 1478 censorship are difficult to reconstruct. However, consider the following three facts. First, no other printed astrological texts from Louvain are known for this period. This makes it likely that the university targeted Laet’s prognostications. Secondly, the university did not restrict their being printed at Louvain. The real issue concerned their being presented as such. Louvain authorities apparenty found it undesirable to be publicly associated with Laet’s prognostications. In third place, one should consider local political events, which enable us to understand why Laet’s prognostications became problematic in the years 1477–1478. Ten years before, Liège had lived its darkest hour at the hands of Burgundy. In 1467, Charles the Bold had abolished the prince bishopric’s political autonomy. One year

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See Joannes de Los, “Chronicon rerum gestarum,” p. 81. Molanus, Historiae, ed. De Ram, vol. 1, p. 571: “Universitas anno 1478 prohibuit impressoribus, ne Almanack imprimant cum hac adjectione: impressum Lovanii. Acta.” 45 Hieronymus de Manfredis, Prognosticon anni 1479. 44

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later, he forced Louis xi to witness the systematic destruction of its capital of 20,000 inhabitants, thus avenging the frequent associations between France and Liège against Burgundian authority.46 But the grim death of Charles the Bold near Nancy on 5 January 1477 brought an unexpected reversal.47 On 19 March, the prince bishop convinced Mary of Burgundy to renounce her rights to the pays liégeois. Maximilian of Austria, who married Mary on 18 August, was less than happy with this spectacular concession, and moved fast to initiate negotiations. These started in late September 1477 at Louvain, where both parties regularly reconvened until at least April 1479. Louvain’s former professor of rhetoric, Petrus de Rivo, had already been charged with composing a panegyric to Maximilian in 1477.48 The role of Louvain was confirmed between February and April 1478, when Archduke Maximilian charged its mayor, Sire Louis Pynnock, with these negotiations.49 Under these circumstances, Louvain could not afford to manifest even the slightest partiality towards the Liège cause. It seems plausible that the public connection between Louvain and the prince bishop’s astrologer Joannes Laet was among the first to tumble. That Pynnock chose to act through the academic authorities becomes understandable when we consider that printer Jan van Westfalen was a member of the university, and therefore fell outside the town’s jurisdictional competence.

3. The teaching of academic astrology 3.1. Mathematics at the arts faculty The interest in Louvain astrological consulting explains why its academic practitioners also taught the art to their students. Following the example of other northern universities, Louvain organised its official curriculum within the confines of the arts faculty. The Louvain statutes (1427) prescribed lectures on Sacrobosco’s De sphaera, the first book of Euclid’s Elements, a treatise on arithmetic (probably by Boethius), and the treatise on music by Joannes de Muris.50 These 46 47 48 49 50

See Harsin, La principauté de Liège (…) 1477–1505, pp. 31–36. Ibid., pp. 37–70. IJsewijn, The Coming of Humanism, p. 263. See Harsin, La principauté de Liège (…)1477–1505, pp. 62–63. Reusens, “Statuts primitifs,” p. 154: “Statuimus et ordinamus quod in mathe-

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were first taught in the academic year 1430/1 as a general course for all arts students.51 The revised statutes (1429) stipulated lectures in the afternoon from around St. Dionysius’ day (October 1) until the feast of Purification (February 2), which suggests a rather concise treatment. This initial programme was entrusted to a student of the higher faculty of medicine called Gerardus Hoefmans.52 In 1431/2, the university asked Joannes Vesalius, professor at the arts faculty, to teach the mathematics course of the arts faculty.53 Vesalius declined, upon which the members of the assembly decided that two students of the medical faculty (masters Matthias de Lewis and Henricus de Helmont) would share the task. It was also granted that whoever wished to teach mathematics privately could do so in his own home.54 The boarding-homes of the regentes thereby seem to have become the main locus of mathematical instruction. These domus regentium gradually developed into the four pedagogies of the Castle, Falcon, Lily, and Porc, where most artistic training was organized until the closure of the old university in 1797.55 Vesalius’ refusal introduced two standard elements of mathematical instruction at the Louvain arts faculty: instruction within the confines of each of the four pedagogies, given by graduates who studied for a higher degree, usually in medicine. The Louvain town council seems to have been most concerned about the continuity of mathematical instruction. The university reg-

maticalibus legentur tractatus de sphera, primus liber Euclidis, aliquis tractatus de arithmetica et Johannis Muris musica.” The regentes of the arts faculty were instructed on 24 September 1428 to come to an agreement “de mechanica et de libris mathematicis” to be taught. See Reusens, Documents, vol. 2.1, p. 235; Van Belle, Faculteit van de Artes, p. 225. 51 The new statutes of 1429 specified: “In ultima congregatione ante festum Dionysii eligatur unus, qui habeat legere mathematicam, et eam incipere, et omni die legibili post meridiem continuare, et ante festum Purificationis beate Marie Virginis ad commodum scolarium et honorem Facultatis terminare” (Reusens, “Statuts primitifs,” p. 177). 52 On Gerard Hoefmans’ appointment to this task, see Andreas, Fasti Academici, pp. 248–249; Reusens, Documents, vol. 2.1, p. 235; Lefebvre, “Les sciences,” p. 47. See arab, oul 731, fol. 1v: “1430 14 novembris via scrutinii eligitur docturus librum aethicorum, et alter Mathematicarum in vico.” 53 Lefebvre, “Les sciences,” pp. 47–48. 54 See arab, oul 731, fol. 45r: “1431 fol 60 die 28 junij rogatur Joannes de Wesalia doctor in medicinis ut velit in scholis artistarum docere mathematicam. Id resolvetur folio 62 quia renuntiat ibidem eoque D. Mathias de Lewis eodem folio verso. Vide folio 62 verso. Folio 62 verso placuit facultati quatuor Magistris reclamantibus quod de cetero quilibet posset in domo sua legere mathematicam.” 55 Van Belle, Faculteit, pp. 201–212.

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ularly appointed either graduates in theology or medicine to the task at the town’s request. In 1443, the town council spurred the arts faculty to provide a lecturer for a public lesson on mechanica et mathematica.56 At least from 1445 to 1447, the theologian Joannes Block was entrusted with public lessons in both mathematics and rhetoric.57 These lessons were remunerated through one of the new canonries of St. Peter’s chapter, which the arts faculty attempted to incorporate into its proper structure at the beginning of the academic year 1445/6.58 However, there is reason to question the actual role of mathematics in the education of most university students. Prior to the academic year 1430/1, Matthias de Lewis and a certain master Berthold Steenwijck had already taught mathematics at the arts faculty. These lessons, however, were listed as extraordinarie. Such terminology qualified mathematics as a less important part of the arts curriculum, which could be entrusted to students of the higher faculties.59 Indeed, most students had little or no use for mathematics in their further career. Dispensations for students who had not completed the final courses of their program were frequently granted.60 The statutes of 1567/8 explicitly requested examiners for the master’s degree in arts to emphasize topics that were important for the study of the three higher disciplines, and to give little weight to the others.61 This could imply that mathematics fell out in many final examinations at the arts faculty. It was also the case that many students – especially those in the Law faculty – began their higher study before they had 56 See arab, oul 731, fol. 39v: “1443 25 augusti folium 83v: et hortatur civitate ut provideat illo anno de lectione mechanica et mathematica.” 57 See Lefèbvre, “Les sciences,” pp. 47 and 50–52. 58 arab, oul 731, fol. 40r: “1445 29 octob fol. 85 deputatur Unus qui hoc anno legat mathematicam, et unus sit Godefridus Gompel metaphysicam pro omnibus magistrandis, et dispensavit facultas secum ut possit eam legere in domo sua, qui ut sic acceptavit huiusmodi lectiones. Ibidem facultas tentat incorporari duas prebendas unam pro mathematico, alteram pro Rhetore, pro utilitate sua.” See Paquet, Salaires et prébendes. 59 arab, oul 731, fol. 44r: “1429 fol. 21v [in margine: quinta die mensis decembris] Item eadem die admissa fuit supplicatio Magistri Matthiae Leuwis supplicantis ut extraordinarie posset legere unum librum mathematicae. Et etiam admissa fuit supplicatio Magistri Bertholdi Steenwick supplicantis ad idem.” Also see Van Belle, Faculteit, p. 334. 60 See Van Belle, Faculteit, p. 265. In 1433, three candidates for the licentiatus degree were allowed to the exams of the arts faculty without having taken courses in mathematics, ethics, or parts of the physics lectures, on the condition that they would make up afterwards. 61 See Paquet, “Statuts (1567–1568?),” pp. 225–226.

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obtained their master’s degree in the arts. This seems to have been the central problem underlying a report, presented to Pope Adrian vi by the Louvain arts faculty in 1523.62 3.2. Astrological instruction at the medical faculty Professors of the Louvain medical faculty did teach more advanced lessons in “astronomy.” When Joannes Vesalius left Louvain in 1443, the town council did not approve of the university’s choice of Ludovicus de Vettere of Diest as his successor. The town refused to pay De Vettere until 1453, when Joannes Sucquet (c. 1415–1489/90) succeeded him.63 But in 1452, the municipal authorities did pay De Vettere “for his lessons in astronomy during the entire year.”64 Sucquet’s successor Joannes Spierinck (c. 1420–1499) also received a payment from the town in 1475 for his “lessons in medicine and astronomy.”65 Unfortunately, we have no direct evidence about the Louvain interpretation of “astronomy.” We know, however, that the Louvain town council valued both these lessons and the production of annual almanacs with astrological content. We also know that teachers of “astronomy” like Vesalius and Spierinck were regularly called upon to provide astrological advice. This makes it very likely that Louvain used it as a generic term for the “science of the stars,” including both astronomy and judicial astrology. Which kind of astrology would have been covered in the Louvain courses on “astronomy”? Although virtually no information about the early medical faculty has been preserved, a number of loose state62 Relevant extracts from this report were published in A. Fierens, “Les ambitions,” pp. 56–68. The faculty proposed that all new students under 25 would pursue the study of logic and natural philosophy up to the baccalaureus level, or would acquire equivalent knowledge elsewhere. The faculty’s proposal did not mention mathematics as a prerequisite, since this was usually prescribed for the magister title only. Compare to De Ridder-Symoens, “Onderwijs aan de middeleeuwse universiteit,” pp. 189–204. This paper emphasizes that only 50 % of the law students at Orléans had taken the ma degree in the period 1444–1546 (p. 193). 63 See Meulemans, “Wesaliana,” pp. 19–22. On Joannes Sucquet, see Wickersheimer, Dictionnaire, vol. 2, p. 488. 64 sal 5082, fol. 83: “voir syne lessen in astronomie voir tghehele jaer.” Quoted in Meulemans, “Wesaliana,” p. 20. 65 See Reusens, Analectes 38(1912), pp. 280–281: “Meester Janne Spierinck vor dexcercicie vander lesse van medecijnen ende astronomien boven sijn provende van enen quartier jars verschenen den jersten dach julij anno lxxv, vijf gulden.” On Joannes Spierinck, see Wickersheimer, Dictionnaire, vol. 2, pp. 486–487; Jacquart, Supplément, p. 183.

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ments allow a fairly reliable reconstruction. One may distinguish three general types of medical astrology, depending on the number of parameters that physicians considered relevant.66 The first can be traced back to the canon of ancient medicine. The Hippocratic Air, Waters, Places commented on the importance of astronomical knowledge for the prediction of weather and disease. These comments received an astrological reading in late medieval academic medicine.67 Equally important was Galen’s On Critical Days, which provided an astrological explanation of “critical days,” when diseases reached a crisis. According to Galen, critical periods generally followed the lunar phases and the moon’s position in the zodiac. This text advocated a minimalist astrology, where lunar positions played the main part, occasionally supplemented with certain fixed stars. Hellenistic astrologers expanded this type of medical astrology in various ways.68 A typically moderate example is the pseudo-Hippocratic Astronomia Ypocratis, which was very popular among late medieval physicians.69 This treatise studied the position of the moon within each of the zodiacal signs (in accordance with the doctrine of melothesia),70 and with respect to the maleficent planets Mars and Saturn. These parameters were applied for diagnosis, prognosis, and therapy. The most incisive impact of astrology in medicine occurred in texts like the pseudo-Galenic Prognostica de Decubitu. Infusing medical prognosis with the techniques of astrological interrogation, this treatise had more concern for the patient’s astrological chart than for the empirical constitution of his body.71 Similar attitudes prevailed 66 For general introductions to late medieval and Renaissance medical astrology, see Müller-Jahncke, Astrologisch-Magische Theorie und Praxis, pp. 135–174; Arrizabalaga, “Facing the Black Death”; Chapman, “Astrological Medicine”; French, “Astrology in Medical Practice”; French, “Foretelling the Future”; Wilcox, “Transmission.” 67 See Hippocratic Writings, ed. Lloyd/transl. Chadwick and Mann, pp. 149, 158. Other common Hippocratic loci that are open to astrological interpretation include Aphorisms iii.1;iii.5;iv.5. 68 See Barton, Ancient Astrology, pp. 185–191. 69 On the Astronomia, see Thorndike, “Three Latin Translations”; Kibre, “‘Astronomia’ or ‘Astrologia Ypocratis.’” I have consulted the edition Astronomia de Infirmitatibus, appended to Magninus Mediolanensis, Regimen Sanitatis (1500). 70 “Melothesia” is the presumed connection between specific signs or planets and specific parts of the human body, as exemplified in the so-called zodiac-man. See Hübner, “Eine unbeachtete zodiakale Melothesie”; Marcelis, De afbeelding van de aderlaat- en de zodiakman; and the reference to Charles W. Clark, “The zodiac man in medieval medical astrology” in: Dissertation Abstracts International 40(1979), 2199-A. 71 The Prognostica de Decubitu regarded the time of the patient’s taking to bed as

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in the uroscopy of William of England’s De urina non visa 72 or the Compendium astronomie iudicialis of Geoffroy de Méaux.73 Professors of the Louvain medical faculty easily adopted the first type of medical astrology. A good example is the medical almanac of Joannes Spierinck (1484), which listed lunar phases to indicate suitable days for venesection and purging. Joannes Vesalius also composed grant almanachs, which add the positions of other planets for higher precision. This expansion into our second type of medical astrology was considered acceptable among Louvain’s scholastic physicians, as the preface to Thomas Montis’ quodlibetica (1521) suggests: Through the motion of the moon, the physician can foretell the true hour of a crisis, and securely denounce its beneficial or harmful nature from the moon’s aspect with the other planets [my italics].74

This conforms to the moderate tradition of the Astronomia Ypocratis. Another text that promotes this form of medical astrology is the Regimen sanitatis of Maynus de Maineriis (c. 1331), printed at Louvain in 1482 and 1486 for didactic use in the medical faculty.75 Practical interests seem to have dominated academic astrological teaching. Vesalius’ comet tract (1472) presented the author as an astrological expert who studied the comet’s signification, but also as a natural philosopher (phisicus) who studied the physical constitution of the comet.76 Vesalius seems to have felt the need to explicitate that he discussed not only the practical, but also the theoretical part of academic astrology. Although the practice of judgment was central to the definition of astrology, Vesalius seems to have disposed of common cultural resources to extend his role into theoretical concerns. The comet tract also mentioned several of the textbooks that Vesalius consulted to determine the comet’s effects. Two references were made to Guido Bonatti’s Liber astronomiae, as well as to Leopold the basis for an astrological interrogation. See Weinstock, “The author of Ps. Galen’s ‘Prognostica de Decubitu.”’ 72 See French, “Astrology in medical practice,” pp. 44–48. 73 See the marvellous analysis of Jacquart, “Médecine et Astrologie à Paris.” 74 Montis, Quodlibetica, fol. a2v: “Per motum lune medicus veram crisis horam prenoscere potest, ac bonam aut malam crisim ex aspectu lune ad ceteros planetas intrepide denunciare potest.” 75 Magninus Mediolanensis, Regimen Sanitatis (Louvain, 1482 and 1486). These editions are Polain, 2559 and 2560. I thank Dr. Chris Coppens (Leuven, University Library) for his advice on the interpretation of these editions. Also see Jacquart, La médecine médiévale, pp. 462–463. 76 The history of the term physicus was discussed by Schipperges, “Zur Bedeutung von ‘physica’ und zur rolle des ‘physicus.”’

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of Austria’s Compilatio de astrorum scientia.77 Vesalius also adopted passages in ps.-Ptolemy’s Centiloquium, the last book of Haly Abenragel’s De iudiciis astrorum, Albertus Magnus’ (c. 1193–1280) commentary on the first book of Aristotle’s Meteorology, Alcabitius’ Isagoge and Abraham Ibn Ezra’s Beginning of Wisdom. Vesalius’ collection of late medieval astrological texts is fairly similar to those that were listed in the medical curricula of Padua and Bologna. It contained both basic (Alcabitius) and advanced (Bonatti and Abenragel) textbooks, as well as widely diffused collections of specific precepts (ps.-Ptolemy). This similarity to the Italian curricula is hardly surprising. Vesalius was educated at Pavia, and seems to have cultivated his Italian connections after he returned to the north. Around the time of his appointment as town physician of Brussels (1454), Vesalius dedicated a plague tract to Francesco Sforza (1401–1466), Duke of Milan.78 Such connections were reinforced after the 1460s, when academic contacts between Italy and the Low Countries became much more intense.79

4. Astrology and theology in late medieval academic culture 4.1. The Louvain union of revelation and astrology Another important issue of demarcation that transpired in Vesalius’ cometary treatise concerned the relation between astrology and theology. This relation was often interpreted in terms of natural versus supernatural interpretations of a phenomenon. Natural philosophy demanded that the comet’s effects derived from the virtue of its matter and the planet to which it was closest. Theology, however, regarded its virtues as directly imparted by God. Vesalius steered 77 His classification of the comet as being of the miles type was clearly taken from Bonatti, Liber astronomiae iv.105 (“De stellis cometis”). His astrological chorography was also partially indebted to the Liber astronomiae: see § 10 of Vesalius’ tract (Abel/Martens, “Le role,” p. 75). The references to Leopold of Austria are in § 24 and 25 (Abel/Martens, “Le role,” pp. 82–83). On Bonatti, see Vasoli, “L’astrologo forlivese Guido Bonatti.” 78 On Vesalius plague treatise, see Bracke, “Joannes de Vesalia, De epidemia”; Belloni, “Joannes de Vesalia”; Meulemans, “Wesaliana,” pp. 26–32. Belloni specifies that Vesalius assisted during the outbreaks of the plague in Maastricht in 1428, in Louvain in 1439, and in Brussels in 1454 (p. 78). A facsimile edition of the treatise is available as Johannes de Vesalia, Facsimile van Johannes de Vesalia’s pesttraktaat. 79 IJsewijn, The Coming of Humanism, p. 233, discusses a number of quadrivial exchanges.

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clear from this problem by emphasizing the astrologer’s inability to assess whether a judgment rested on the action of God or the heavens.80 The intellectual and social predominance of academic theology clearly affected Louvain astrological discourse. However, a broader overview reveals the simultaneous existence of a contrary, and more recurrent theme: the “concordance of astrology and theology.” In an attempt to demonstrate astrology’s truth and utility, Cardinal Pierre d’Ailly (1350–1420) had written a treatise with this title in 1414–1415. D’Ailly’s Concordance demonstrated how specific celestial configurations (especially Saturn-Jupiter conjunctions and great orbs) had signified important religious events or political upheaval throughout history.81 Louvain practitioners of this form of astrological history can be found throughout the fifteenth century. In 1444, a Louvain physician and astrologer called Joannes de Brugis wrote a Pronosticum de veritate astronomie with the aid of a few anonymous colleagues.82 Along with Pierre d’Ailly’s aforementioned trilogy, his Pronosticum represents “the apogee of a learned genre, founded on the correspondence between great conjunctions and the major events of the past, present, and future.”83 Joannes de Brugis discussed the nature of the sign of Scorpio, of conjunctions, and of the watery triplicity in the first three chapters of his treatise. The next four chapters contain a detailed discussion of the effects of the conjunctions of 1365, 1425, and 1484, discussing those of 1444, 1464, 1503, and 1524 as well. In the five last chapters, we find extended astrological analyses of the nativity of Christ, the coming of the Antichrist, and the eschatology of the world.84

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Abel/Martens, “Le role,” pp. 76–77. For an excellent discussion of the content and broader significance of D’Ailly’s astrological work, see Ackerman Smoller, History, pp. 61–84; North, “Astrology and the Fortune of Churches.” 82 For further references to Joannes de Brugis and his work, see now Boudet, Lire dans le ciel, pp. 80–83; Thorndike, History, vol. 4, pp. 146–147. Of the Latin Pronosticum only one manuscript is known, while a French version is known in two mss., one of which was owned by Simon de Phares. De Phares devotes an entry of his Recueil to Joannes de Brugis (De Phares, Recueil, ed. Wickersheimer, pp. 563–564). Dirk Martens published the Latin Pronosticum in Antwerp before 1504, probably because of its relevance to the imminent Saturn-Jupiter conjunction of 1503. 83 Boudet, “L’astrologie, la recherche,” p. 29. For the situation in an earlier period, see d’Alverny, “Astrologues et théologiens au xiie siècle.” 84 On Renaissance interpretations of the birth chart of Christ, see Zambelli, Una reincarnazione di Pico; Shumaker, Renaissance Curiosa, pp. 53–90. 81

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Between 1480 and 1483, the Louvain university printer Jan van Westfalen published the editio princeps of Pierre d’Ailly’s astrological writings. One year later, Paul of Middelburg wrote his Praenostica for the next twenty years at Louvain. Apart from common data like the planetary conjunctions and solar eclipse of 1484 (see chapter 1), Van Middelburg also referred to Saturn-Jupiter conjunctions signifying the biblical Flood (3381 bc), the advent of Christ (6 bc), the advent of Islam (ad 571), the reign of the Carolingians (ad 808), the change of triplicity in ad 1365, and the immediately preceding conjunction of ad 1464. This tradition of astrological history was still thriving at the Louvain faculties of arts and medicine in the 1510s. This is clear from a quodlibetal disputation that master Henricus Afinius held on 19 December 1516.85 Before an audience of hundreds, Afinius confidently followed D’Ailly’s astrological belief that the stars had influenced all human aspects of Christ.86 Afinius implemented this tradition to disprove the common notion that Christ was conceived on 25 March, and then oddly used it to buttress his opinion on the problem of calendar reform.87

85 The published text of this disputation is Afinius, Questiones tres. Afinius had been invited to discuss a medical, astronomical, and metaphysical question. At the time of his disputation, Afinius had probably long completed his medical studies at Louvain (he was enrolled at the Faculty of Arts on 31 August 1499), and seems to have been well-established as town physician of Antwerp, and personal physician of Erasmus (see the introduction to the latter’s letter to Afinius dd. 1517 in: Collected Works of Erasmus, vol. 4 (Toronto/Buffalo, 1977), p. 268). The terms in which Afinius refers to Alessandro Achillini (1463–1512), professor at the medical faculties of Bologna (1484–1506 and 1508–1512) and Padua (1506–1508), suggest that Afinius may have studied under him (probably at Bologna) after his Louvain studies (Afinius, Questiones tres, fol. c3r: “Alexander enim Achillinus bononiensis (…) aliquoties mihi inter colloquendum [my italics] comparavit”). 86 See Ackerman Smoller, History, p. 38. 87 In his Elucidarium, d’Ailly had mentioned two opinions on Christ’s natal chart. One, reported by Albertus Magnus, stated that Christ was born with Virgo 8° in the ascendent, while the other preferred Libra 2°. Both charts agreed in having the moon in Taurus 4°. Afinius applied an astrological technique to rectify natal charts to these data, in order to determine the time between birth and conception. Although Joannes Angelus’ (d. 1512) Astrolabium planum contained the most common late medieval tools to do this, Afinius preferred to rely on the slightly different values of Leopold of Austria (fl. 1280) and Antonius de Montulmo’s (fl. 1390). This established that Christ was conceived on 6 April according to the first natal chart, and on 8 April in the second case.

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4.2. Logic, revelation, and future contingents Which specific interests allowed Louvain academic astrologers to discuss the theological premises of revealed truth with such frequency? This section argues that astrology provided a tool to transcend a local conflict between the twin faculties of arts and theology on the correct interpretation of propositions about the future. Our initial clue for this interpretation comes from Joannes Laet’s choice of terminology in his printed prognostication for 1479. In his letter of dedication to Louis de Bourbon, Laet carefully referred to his predictions as “future contingents” (futura contingentia).88 In the early 1470s, a fierce debate on “future contingents” had jeopardized the very existence of the university. Laet’s use of this concept inevitably linked his prognostication to this debate, which was probably exactly what its author intended. After an earlier incident in the period 1446–1448, the Louvain debate on future contingents erupted on 13 December 1465, when the annual quodlibetal disputation treated the following question: “did St Peter have the power not to deny Christ, after He had told him that this would happen thrice before the cock crowed?”89 The disputante was Peter de Rivo, who held the chair of rhetoric at the arts faculty since 1460.90 De Rivo approached the question from the angle of the existence of contingency and moral freedom. Central to the problem of future contingents is our intuition that a statement such as (1) “There will be a sea-battle tomorrow” is either true or false (principle of bivalence). At the same time, we seem committed to connect this proposition about the future to a corresponding proposition about the past, such as statement (2) “There was going to be a sea-battle yesterday.” Here is the problem: depending on whether the sea-battle indeed happens tomorrow, or not, we are inclined to say that (2) is true or false. It seems intuitively impossible to defend the truth of (1) and the falseness of (2), or vice versa. Put this way, we are left with the distinct impression that both past and future are somehow unalterable.91 88

Laet, Prenosticata pro anno 1479, fol. [1r]. A wonderful dossier of texts from the Louvain debate has been collected and introduced in Baudry, La querelle des futurs contingents. An English translation is provided in Baudry, The Quarrel over Future Contingents, trans. Guerlac. The text of De Rivo’s disputation is edited in Baudry, La querelle, pp. 70–78. 90 See Baudry, La querelle, pp. 20–21. 91 See Normore, “Future Contingents.” My characterization of the general problem cites Normore’s excellent introduction on pp. 358–359. 89

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In his quodlibetal disputation, De Rivo solved this by rejecting the principle of bivalence.92 Future contingent propositions where neither true nor false; instead, they were neutral and lacked any truthvalue.93 This solution entailed serious problems for any account of divine prophecy, of which De Rivo was well aware: So far I have spoken philosophically, as is appropriate in the School of Arts. But because I feared some of my hearers might perhaps be disturbed in their faith by the foregoing, because they had earlier heard me state that there is not a determinate truth in future contingents, and it might perhaps seem to them that the propositions about the future contingent contained in the prophetic Scriptures and in the Creed, such as “Antichrist will be born,” “The dead will rise again,” “Christ will judge the world,” and the like, are not determinately true and consequently not firmly to be believed (…), lest it happen that the weak in faith be scandalized by this conclusion of mine, I stated two things.94

Can biblical prophecies be absolutely true? De Rivo said that they could, if one accepted two qualifications to his previous account. First, eternal divine foreknowledge could not be adequately expressed by a future proposition; hence, some of the biblical prophets used the past tense. Second, biblical prophecies should be considered as material expressions of God’s uncreated truth, as opposed to the created truth that needs verification before it is accessible to man.95 These qualifications did not go down well with the theological faculty. A pupil of the theologian Henricus Van Zomeren attacked De Rivo in the quodlibetal disputations of 1466, stating that “truth is never missing from the scriptural prophecies” on the authoritity of Scripture and St Augustine.96 De Rivo acknowledged that it was heretical to follow Aristotle when judging the truth-value of biblical prophecies. But he did not concede that it was a rational fallacy. Aristotle only referred to propositions regarding created truth, not

92 In doing so, De Rivo mainly followed Peter Aureoli’s earlier views. See Normore, “Future Contingents,” pp. 370–371. 93 See Baudry, La querelle ¸ p. 71. The locus classicus for discussions on future contingents is Aristotle’s De interpretatione i.9 (18a29–19b4). For a review of current discussion, see Craig, Divine Foreknowledge, pp. 1–58. 94 Translation from Baudry, Quarrel over Future Contingents, trans. Guerlac, p. 43. Original text in Baudry, La querelle, p. 76. 95 See Baudry, La querelle, p. 77. 96 Ibid., p. 294.

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to uncreated truth. A good catholic therefore had to uphold both Aristotle and Faith. Giving up the former would deny the existence of contingency; abandoning the latter would deny the truth of biblical prophecy.97 De Rivo’s distinction between created and uncreated truth was quite handsome to the logicians, but unacceptable for a theologian like Van Zomeren. On 14 November 1469, he resumed the debate with unprecedented fervor; both parties enlisted the support of an ever widening circle of authorities. By the fall of 1470, the triumph of De Rivo seemed imminent: the theological faculties of Louvain and Cologne had just provided a particularly favorable advice, and the members of the academic council were inclined to oppose Van Zomeren, who found himself threatened with expulsion. With a little help from his Roman friends (notably Cardinal Bessarion), Van Zomeren retaliated through a direct appeal to the Pope, which increased the animosity among Louvain theologians even further. No later than October 1471, news reached Louvain that the Pope was enfuriated, and even considered declaring the entire university heretical. A very strong admonition reached the university in the form of a papal brief on 23 May 1472.98 In the beginning of September, it was De Rivo’s turn to set out for Rome, where his docile behavior towards the papal commission was much appreciated. Although De Rivo retracted some of his views on 19 March 1473, he felt confident enough to claim that this did not affect his theoretical position after he returned to Louvain. A new extended investigation concluded the affair when De Rivo signed a second and final retraction in 1476. What made De Rivo’s defense of Aristotle and Faith so unacceptable to the Louvain theologians? A remarkable answer emerges when we focus on Van Zomeren’s comments about the distinction between created and uncreated truth. Here is a representative sample: That, moreover, in admitting that propositions of the faith about the future are true by virtue of the uncreated Truth of the sayer or by expected truth, he did not mean to admit they are absolutely true, he seems to be persuaded for many reasons. First, because both when and how often he said or admitted them true by the uncreated Truth of the sayer or revealer or by expected truth, he said it not as a conclusion deliberately drawn from him, but only from the necessity of replying to arguments

97 98

Ibid., p. 366. The history of this debate is summarized in Baudry, La querelle, pp. 32–46.

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Van Zomeren did not accuse De Rivo of erroneous reasoning. The real problem lay with the motivations underlying his opponent’s use of the distinction between created and uncreated truth. Van Zomeren took De Rivo to task for not being primarily concerned with the absolute truth of biblical prophecy. As a member of the arts faculty, his competence was restricted to logical and physical problems like the contingency of future events, or the truth of propositions about them. Propositions of the faith, even if they were about the future, were the strict prerogative of his colleagues at the theological faculty. In 1465, this did not stop De Rivo from using Christ’s prophecy to St Peter as a signpost for his logical discourse. The lack of objections from the arts faculty, indicates a much broader power struggle between Louvain logicians and theologians over the authority to discuss biblical propositions. This was the real subtext of the Louvain debate on future contingents. Despite their initial success, the Louvain logicians suffered a rapid defeat when Van Zomeren appealed to Rome in 1471. 4.3. Astrology and future contingents The outcome of the Louvain debate on “future contingents” probably created a specific local meaning for this term: it claimed truth for propositions about the future, without disputing the primacy of supernatural causes. This would explain the common use of “future contingents” as a synonym for astrological predictions at Louvain. When Joannes Laet adopted the term in his 1479 prognostication, he simultaneously emphasized the contingency and natural basis of his predictions.100 Two Louvain astrologers of the early sixteenth century also turned to this conceptual framework to legitimize their own predictions.101 99

Translation from Baudry, Quarrel over Future Contingents, trans. Guerlac, pp. 259–

260. 100

Laet, Prenosticata pro anno 1479, fol. [1r]. See Afinius, Questiones tres (1517), fol. c3r: “Aristoteles autem primo peryhermenias ut a rebus contingentibus futuris necessitatem auferret in eis dixit non esse determinatam veritatem.” In another quodlibetal disputation, held on 18 December 1521, Thomas Montis also employed this vocabulary when he emphasized that the February 1524 conjunctions (see chapter 4) “will happen contingently to us” (“nobis contingenter futuri”). 101

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Joannes Laet’s use of the term clearly avoided De Rivo’s obstinate emphasis on the primacy of natural reason, thus creating a legitimate space for naturalizing astrological discourse.102 In other words, Laet’s use of “future contingents” was highly localized, and agreed with the position of Van Zomeren, who policed the local interpretation of “future contingents” after 1471. Referring to astrological predictions as “future contingents” was an excellent way to make one’s predictions palatable to the Louvain theologians. The local success of astrological history can also be understood against the background of the debate over future contingents.103 In their struggle for the authority to interpret biblical propositions on future events, Louvain theologians emphasized the continuity between past and future. Seen from this perspective, D’Ailly’s concordance of astrology and theology provided an attractive ally. When astrologers showed how the biblical Flood, or the birth of Christ, were foretold in the stars, they created an interpretive framework that moderated the distinction between past and future, or between biblical prophecy and astrological discourse. Pierre d’Ailly had famously done so, for instance, when he suggested the Antichrist’s coming in the year 1789.104 Using Peter de Rivo’s terminology, one could state that astrology’s success in establishing created truths of the past simultaneously warranted belief in uncreated truths of the future. Astrology provided a body of knowledge that avoided the logician’s strict separation of past and future. Especially in the 1470s, this implied a unique potential to bridge the institutional rivalries that separated the Louvain faculties of arts and theology.105 The next two chapters describe how this careful balance became unhinged through the popular culture of late medieval annual prognostications, first in Italy, then at Louvain.

102 Already in 1465, De Rivo presented astrological and astronomical knowledge as potential refutations of the existence of contingency. See Baudry, La querelle, p. 73. 103 This paragraph can be read as a comment on Pomian, “Astrology as a Naturalistic Theology of History.” Pomian points out that medieval conjunctionism provided intelligibility without purpose to history, but fails to specify historical parameters for the adoption of this particular “chronosophy.” 104 Thorndike, History, vol. 4, pp. 107–108. 105 A spectacular example of the success of Pierre d’Ailly’s astrological history among theologians comes to us from Paris, where the faculty of theology was asked to examine and judge the astrological library of Simon de Phares in 1494. All of the works of Pierre d’Ailly (including his heavily astrological De legibus et sectis) were described as “unobjectionable.” See Thorndike, History, vol. 4, pp. 112–113.

CHAPTER THREE

BETWEEN ASTROLOGICAL REFORM AND REJECTION: GIOVANNI PICO’S DISPUTATIONS (1494)

1. The problem: Pico and the astrologers At his death on 17 November 1494, Giovanni Pico della Mirandola (1463–1494), the Wunderkind of late Quattrocento Florence, left an unfinished manuscript that was twice the size of his previous works brought together. Published in 1496 under the supervision of Gianfrancesco Pico (c. 1470–1533) and Giovanni Mainardi (1462–1536), its twelve books of Disputations against divinatory astrology contained the most extensive and incisive attack on astrology that the world had yet seen.1 Pico composed a fourfold encyclopedia of contradictions within the astrological canon and of conflicts between this canon and Aristotelian physics, common experience, or Christian faith. Giovanni Pico was an unlikely candidate for authoring this pinnacle of astrological criticism. After originating in antiquity, the genre had been dominated by philosophers with a bent for scepticism, churchmen with a knack for salvation, or combinations of these.2 The young count of Mirandola could not be further removed from being a stern sceptic or churchman. Moreover, astrology had been part and parcel of Pico’s previous work. In the notorious Conclusions (1486), banned by papal injunction and causing Pico’s flight to France, he was quite willing to subject both the human body and intellect to celestial virtues. In a set of eight theses derived from Porphyry’s views, as related in Proclus’ commentary on Plato’s Timaeus, Pico suggested that human skills (craftsmanship, medicine) inhere

1 The modern edition is Pico della Mirandola, Disputationes, ed. Garin (henceforth referred to as “Disputationes”). Important interpretations of the Disputationes are Vickers, “Critical reactions”; Weil, La Philosophie … Pic de la Mirandole; Zanier, “Struttura e significato delle Disputationes Pichiane.” 2 On the ancient traditions of astrological criticism, see Long, “Astrology: Arguments Pro and Contra.”

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in specific types of intellect, in which individual souls come to participate through celestial virtue, with heaven being “a celestial animal.”3 The enterprise baffled Pico’s Florentine friends and contemporaries. Some three months before Pico’s death, Marsilio Ficino (1433–1499) had a very difficult time convincing Angelo Poliziano (1454–1494) that the astrological content of his famous De vita coelitus comparanda (1489) could be reconciled with Pico’s criticism.4 Even more perplexed was Pico’s opponent Lucio Bellanti, who –in spite of his veneration for the author- was convinced that Pico would have burned the Disputations had he lived long enough to witness its publication.5 Modern scholars have tried to resolve this problem by situating the attack on astrology within a “distinctive structure of Pico’s thought.”6 This structure usually “rests on the sharp distinction he makes between the [corporeal] realm of necessity and the [spiritual] realm of freedom.”7 According to Ernst Cassirer and Pico’s biographer Eugenio Garin, Pico proclaimed that man chooses his own destiny by mastering the physical world around him, not the other way around. This view is usually taken to be expressed most forcefully in Pico’s Oration on the Dignity of Man.8 Daniel Pickering Walker has refined this view by claiming that Pico did not intend to attack the “good” astrology which “safeguarded human responsibility and divine providence.”9 Although Walker’s solution points in the right direction, it lacks specificity. After all, we have seen that the astrological theory of Ptolemy’s Tetrabiblos disavowed determinism on the basis of epistemic secrecy (chapter 1). Although Pico’s Disputations acknowledged the value of this model, this did not stop his undiscriminating attack

3 Farmer, Syncretism in the West, pp. 306–307 (conclusions 22.4–8). These conclusions seem to be connected to Pico’s own Platonic theses 5>9–12 (Farmer, Syncretism in the West, pp. 440–441). Farmer, Syncretism in the West, pp. 448–449 (conclusion 5>34). 4 See Ficino’s letter to Poliziano dd. 20 august 1494 in: Ficino, Opera omnia (1576), p. 958. 5 Bellanti, De astrologica veritate (1502), fol. a1v. 6 Cassirer, “Giovanni Pico,” p. 342. 7 Ibidem. 8 Cassirer, “Giovanni Pico,” pp. 338–346; Garin, Giovanni Pico (1937), pp. 169– 193; Garin, The Zodiac of Life, pp. 26–27. 9 Walker, Spiritual and Demonic Magic, p. 55.

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on the entire tradition of Latin astrological practice – good or bad. Why was Pico unable, or unwilling, to convert his theoretical moderation into an equally moderate attitude towards astrological practice? This chapter argues that the contrast reflects Pico’s broader concerns. The Disputations criticized the practice of judicial astrology in late fifteenth-century Italy, and not so much its theoretical soundness.10 Accordingly, I claim that Pico’s Disputations proposed a revision of late medieval astrological practice that would affect astrological ideas, things, and data (chapter 1). Pico’s modified astrological physics was based on astronomical and Aristotelian ideas (sections 2.1 and 2.2). In the realm of judicial astrology, Pico exposed the implausibility of astrological data (section 2.3.1) and the inaccuracy of its instruments (section 2.3.2), especially with respect to the Latin canon of astrological textbooks (section 2.3.3). The perennial struggle to grasp Pico’s motives is symptomatic of the thoroughness and novelty of this proposal. Nevertheless, it directly inspired attempts at astrological reform in the sixteenth century (chapter 4). 1.1. Pico, Ptolemy, and astrological theory One commonly neglected aspect of Pico’s Disputations concerns its ambivalent relation to astrological physics. The clearest statement of this ambivalence is found in chapter iv.1, where Pico acknowledged that: If the whole of astrology founded itself upon these [reasons, experiences and authorities], and did not seek out more faithless foundations, I would not deem her wholly ruinous, but in need of support. In other words, my judgment would fail as much as it would waver.11

This quote concluded a chapter in which Pico explained his argumentative strategy in the first three books of the Disputations. Pico claimed that the first three books were devoted to statements that

10 The relevance of Italian popular astrology to the genesis of Pico’s Disputations was previously suggested in Zambelli, L’apprendista stregone, pp. 47–48; Fitzgerald, “Some Notes on Pico’s Dispute,” p. 1054. This chapter provides further detail to this suggestion, and combines it with evidence for Pico’s reformist concerns. The Danish astronomer Tycho Brahe proposed a similar interpretation in 1574 (see Brahe, Opera, vol. 1, p. 168). 11 Disputationes, vol. 1, p. 422: “Quibus si tota niteretur astrologia, nec infideliora sibi fundamenta locaret, non esset apud me penitus ruinosa, sed nitabunda, hoc est tam caderet illa mea sententia, quam vacillaret.”

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can be both “justly granted” (dari sine piaculo) and “rationally denied” (rationabiliter negari). A statement of this type, Pico explained, was best dealt with by dissecting its constituent parts, showing these to be founded on dubious assumptions, and concluding that “the claim certainly cannot be not false” (ipsa omnino non esse falsa non possit).12 This was, of course, a testimony to the first-hand knowledge of scholastic disputations that Pico picked up while studying in Paris (July 1485 – March 1486).13 Accordingly, the first three books set up a virtual disputation around the proposition that the sun and the moon have the power to change inferior bodies. Pico first demonstrated that this does not justify the overall claims of astrological practitioners.14 Next, he allowed his opponents to expand the proposition to “all celestial bodies impart something to the sublunary realm,” only to show that this too does not warrant the claims of astrologers.15 Pico repeated this process of expanding and refuting his opponent’s initial proposition until he reached the utmost proposition that can be both granted and denied, only to find that it still does not justify the habitual claims of astrologers. Surprisingly, he identified this utmost proposition (id quod maximum dari potest) with Thomas Aquinas’ position on astrology: For Thomas will concede to them the utmost that can be granted without inflicting a clear breach of the truth, that powerful virtues reach us from all planets, and that different properties belong to different stars: not just those of heating, cooling, humidifying, and drying, but also more occult ones. Through these, the turmoil of earthly things brings

12 Ibid., vol. 1, p. 420: “Noster hic fere in disputando mos ut, si quid et ponat adversarius, quod et dari sine piaculo et contra rationabiliter negari possit, negemus id potius nos quam demus, etiam si sit tale, quo concesso, nihil magis conficiat ille quod contendit; atque ita, serie pervenientes ad id quod maximum postulare potest, ostendamus, etiam id si detur, quod iure negari posse declaratum est, minime tamen colligi quod arbitratur. Sic enim et res ipsa quae venit in disputationem tota per sua membra particularius exploratur, et quam multa gratis accipiat adversarius intelligit, quamquam parum certam et absurdam opinionem tueatur, quae tam multis vel nominibus falsa vel certe dubia, tum, utcumque omnia se habeant, ipsa omnino non esse falsa non possit.” 13 On Pico’s French contacts, see Dorez and Thuasne, Pic de la Mirandole en France (1485–1488). Shortly before leaving for Paris, Pico famously played out the scholastic tradition against that of humanist rhetoric in his letter to Ermolao Barbaro of 3 June 1485. See Breen, “Giovanni Pico Della Mirandola on the Conflict of Philosophy and Rhetoric.” 14 Since astrologers habitually accept the influence of all celestial bodies. 15 Since the effect does not need to include that of all four Aristotelian qualities (hot, dry, cold, wet).

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various gifts, allowing the inferior corporeal nature to derive not every property of men and other things from proximate causes, but at least some from celestial things instead.16

Now let us return to our initial quote. Pico has exactly these subaltern propositions in mind when mentioning the reasons, experience and authorities of astrologers. From our analysis of Pico’s disputational model, we find that he considers these subaltern propositions doubtful, but hardly impossible. This is confirmed in his statement that astrology is merely in “need of support,” in as far as its claims are based on these propositions. Pico freely acknowledges the relativity of his astrological critique in the Disputations. Instead, he presents an exhortation to found the art on the aforementioned propositions only, not to discard them altogether.17 It is not very difficult to trace the source of this idea, since it was developed to defend astrology in Ptolemy’s Tetrabiblos.18 The Latin West had considered Ptolemy (c. 100–c. 170) the “prince of astrologers” ever since this book and the pseudonymous collection of aphorisms Centiloquium were first translated in the first half of the twelfth century.19 Like Ptolemy and Thomas Aquinas, Pico accepted the idea of a celestial influence that could be expressed in terms of Aristotle’s four primary qualities.20 When Pico proposed to rebuild astrology on this basis, he was simply following in Ptolemy’s footsteps.

16 Disputationes, vol. 1, p. 424: “Dabit enim illis Thomas, id quod maximum dari potest citra apertam calumniam veritatis, ut scilicet omnium planetarum ad nos defluvia cum virtute proveniant, et aliis alias stellis esse proprietates, non modo calefaciendi, frigefaciendi, humectandi et exsiccandi, sed occultiores, unde varia munera terrenorum turba sortiatur, ut non omnem proprietatem quam habent homines ceteraque natura corporalis inferior a suis causis proximis habeat, sed aliquam a caelestibus.” 17 Pico makes a similar statement in chapter iii.13 (see Disputationes, vol. 1, p. 294). 18 Boll, “Studien über Claudius Ptolemaeus,” p. 131 sqq., argued that Ptolemy’s astrophysical ideas can be traced back to Posidonius. 19 The best edition of Tetrabiblos is \ΑποτελεσµατικÜ, ed. Hübner. A more commonly accessible, and to our purposes sufficiently reliable edition cum English translation is Ptolemy, Tetrabiblos, trans. Robbins [henceforth referred to as “Tetrabiblos”]. The standard edition of Centiloquium is Ps.-Ptolemaeus, ΚαρπÞσ, ed. Boer. To my knowledge, there is no English translation of this text. On the twelfth-century Latin translations of astrological works, see Tester, History, p. 152 note 91. 20 In fact, Pico’s explicit acknowledgment of the reality of occult qualities went a little further than Ptolemy. Pico assumed that these were uniquely linked to specific substantial forms. See Disputationes, vol. 1, pp. 384–386: “Fluunt illae dotes et potestates [occultas] a principiis intimis ipsorum corporum, hoc est ab eorum formis, sive dicere mavis essentiis.”

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chapter three 1.2. Pico and the challenges of conjunctionism

1.2.1. The background: conjunctionist astrology in late fifteenth-century Italy Albumasar played a crucial role in Pico’s decision to forfeit his support of Ptolemaic astrological physics. As he explained in chapter iv.1, astrology’s “more faithless fundaments” led Pico to opt for rejection instead, using systematic exposure of the technical, historical, empirical and physical problems of astrology. What were the impious assumptions that deflected Pico from astrological reform to rejection? The relation between religion and astrology dominates in chapters ii.4–5 of the Disputations, as well as in the entire books iv and v. The repeated charge with impietas in chapter ii.5 reveals a rather specific concern: For how will impiety arm itself any better against the spearheads of religion than by upholding that divine miracles, through which religion is most forcefully strengthened, should be referred to the heavens?21

Pico states, quite simply, that astrology’s impiety lies in its attempt to reduce the supernatural to the natural. Specifically singled out was the idea, popularized among fifteenth-century intellectuals by Cardinal Pierre d’Ailly (1350–1420), that the birth of Christ had been preceded by a Saturn-Jupiter conjunction announcing the birth of a prophet to a virgin.22 Pico execrated the idea that perfectly natural and regular events like planetary conjunctions would be causally connected to a strictly supernatural event like the Incarnation. Even if a partial reduction of Christ’s birth could be warranted from a natural-philosophical standpoint, it was still considered intolerable because of its impious motivations. Under no circumstances should supernatural events be turned into objects of natural inquiry.23 Pico summarized this attitude when he exhorted followers of Pierre d’Ailly to admit that “if you do not search for these [supernatural phenomena], you are not searching at all; and if you do search for them, you are searching impiously.”24 Pico’s critique of Pierre d’Ailly’s astrological historiography was an attempt to contain the widespread use of these ideas in popular 21 Disputationes, vol. 1, p. 126: “Unde enim se potius adversus tela religionis armabit impietas, quam ut divina miracula, quibus omnis potissimum religio confirmatur, ad caelum pertendat esse referenda?” 22 See Ackerman Smoller, History, Prophecy, and the Stars, pp. 48–60. 23 Disputationes, vol. 1, p. 516. 24 Ibid., vol. 1, p. 518: “Haec si non quaeris, nihil quaeris; si quaeris, impie quaeris.”

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conjunctionist astrology.25 One of the most notorious implementations of Pierre d’Ailly’s ideas in Pico’s age was a Praenostica, written and published by Paul of Middelburg in 1484.26 Around this time, Paul of Middelburg (1446–1534) was both lecturer in astronomy and astrology at Padua and court-astrologer at Urbino. By astrological standards, his Praenostica was a well-researched and careful analysis, which drew heavily on a tradition of political astrology that extended back to Sassanid Persia (ad 226–620), but was known through Arabic intermediaries only. With the De magnis coniunctionibus of Albumasar (787–886) as their reference-text, authors like Roger Bacon (c. 1214/20–c. 1292) and Pierre d’Ailly in turn popularized this political astrology in the Latin West. It provided a form of mundane astrology that based its predictions on the study of Saturn-Jupiter conjunctions and the sun’s vernal ingress.27 In the Praenostica, Paul of Middelburg followed suit by analyzing the effects of a Saturn-Jupiter conjunction that was predicted for November 25, 1484, and combining this with a study of the long-term effects of past conjunctions. Among the latter, he particularly emphasized a conjunction that was linked to the biblical Flood, and another one that preceded the birth of Christ.28 Following the Arabic tradition, Paul strongly emphasized the combination of Saturn-Jupiter conjunctions with dynastic change, religious confusion, or an adverse climate.29

25

I borrow the term “conjunctionism” from Garin, The Zodiac of Life, p. xiii. Paul of Middelburg, Praenostica ad viginti annos duratura (1484). On Paul of Middelburg, see Struik, “Paulus van Middelburg (1445–1503).” The relevance of Middelburg’s Praenostica for the situation on the Italian peninsula is amply proven by the existence of at least four Italian incunabula editions of this text. In 1485, the Praenostica came out both at Bologna and Perugia. Two Venetian editions followed in 1488 and 1492. See Guarnaschelli/Valenziani (eds.), Indice generali, nrs. 7314 and 7315; Garcia Craviotto (ed.), Biblioteca Nacional, nrs. 4358 and 4359. 27 For a more extensive discussion of this tradition of late medieval academic astrology, see section ii.3. A review of late Sasanian astrology and its relation to Arabic prediction is provided in Albumasar, On Historical Astrology, ed./trans. Yamamoto/Burnett, vol. 1, pp. 580–598; Pingree, From Astral Omens, pp. 39–50. 28 Paul of Middelburg, Praenostica, fol. a4r: “Nonnulla tum etiam transacti temporis magnarum coniunctionum profectiones et directiones quarum ad hec usque tempora durare putatur significatio non ab re annotandas arbitrati sumus. Orbis namque magnus cognominatus a coniunctione qui diluvium precessit (…) Coniunctionis vero magne quae christi salvatoris nostri adventum significasse dicitur ascendentis anni eiusdem perfectio ad xiij. libre gradum devolvetur.” 29 One should not overlook Paul’s simultaneous effort to moderate his claims by incorporating the influence of other celestial events and individual natal charts. 26

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The powers of prophecy and conjunctionism in late fifteenthcentury Italy should not be underestimated. Cesare Vasoli showed how both elite and popular mentalities in late fifteenth-century Italy shared an expectation of imminent social change.30 On Palm Sunday 1484, Giovanni Mercurio da Correggio drove through the streets of Rome, proclaiming God’s imminent judgment.31 Ottavia Niccoli confirmed the profound impact of these apocalyptic interpretations. Many of them were pseudonymously ascribed to saints, churchmen, or scholars from a distant past. Although many texts were presented as astrological prognostications (pronostico) or judgments (iuditio), their titles often suggested prophetic origins as well.32 Apparently, the boundaries between prophecy and prognostication were not clearly drawn in these popular texts. This common ground was physically embodied in a number of successful crossovers between prophecy and prognostication. Arguably the most famous example was Johannes Lichtenberger’s Pronosticatio (1488). Lichtenberger (c. 1440–c.1502/3), a former courtastrologer to Emperor Frederick iii, became a parson in his native Rhineland Palatinate in 1481. In 1488, he concocted his own extensive analysis of the 1484 Saturn-Jupiter conjunction in Scorpio from Paul of Middelburg’s aforementioned Praenostica, an anonymous work on comets (1474), and a host of prophetic treatises, often of Joachimite inspiration.33 But whereas Paul of Middelburg published exclusively in Latin for an audience of courtly patrons, urban literati, and academic physicians, at least half of the pre-1500 Lichtenberger editions were vernacular versions. At first, these were predominantly German, but one can discern a clear shift towards the Italian peninsula in 1492, when the first Italian version of Lichtenberger’s prediction was published at Modena.34 This particular Italian interest in Lichtenberger’s mixture between prognostication and prophecy did not abate in the first quarter of the sixteenth century, when Lichtenberger editions appeared 30

Cesare Vasoli, “Temi mistici e profetici alla fine del Quattrocento.” On Correggio, see Wouter Hanegraaff and Ruud Bouthoorn, Lodovico Lazarelli (1447–1500): The Hermetic Writings and Related Documents (forthcoming Phoenix, 2003/4); Kristeller, “Lodovico Lazarelli e Giovanni da Correggio, due Ermetici del Quattrocento.” Ruderman, “Giovanni Mercurio da Correggio’s Appearance in Italy,” can be unreliable. 32 Niccoli, Prophecy and People, pp. 4–12. 33 Kurze, “Popular Astrology and Prophecy,” pp. 177–193; Talkenberger, Sintflut, pp. 56–109. 34 Joannes Lichtenberger, Pronosticatione in vulgare. 31

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in Italy only. The increased interest in popular prediction after 1492 is confirmed by Torquato’s famous Prognosticon de eversione Europae, which also appeared in that year.35 These concerns were spurred by the troubles of Italian politics in the early 1490s. After the death of Lorenzo de’ Medici in 1492, the delicate diplomatic balance between competing Italian states was rapidly distorted. His successor Piero de’ Medici also managed to loosen the old ties between Florence and the French throne, as king Charles viii prepared a military campaign against Naples. A steady stream of popular portents, preaching, and prophecies accompanied these drastic developments.36 1.2.2. Pico and astrological boundary-work The popularity of hybrid texts like Lichtenberger’s Pronosticatio provides an excellent opportunity to investigate the nature of astrological criticism among the Italian elite in this period. For instance, consider Paul of Middelburg. Lichtenberger’s popularity apparently raised a threat for the future bishop of Fossombrone, who retaliated in his Invectiva of (not surprisingly) 1492.37 What was the nature of this perceived threat? Although Paul of Middelburg initially questioned his opponent’s credentials as an astrological practitioner, his attack mainly emphasized Lichtenberger’s disciplinary transgressions. Middelburg accused his opponent of having adulterated astrology with foreign and dubious tenets, which he identified with a number of popular prophetic works.38 The Invectiva was not so much concerned with Middelburg’s public identity as a reliable astrologer, but sought to establish his abstinence from popular practices instead. It was an exercise in

35 Kurze, “Prophecy and History,” pp. 67–68; Fava, “La fortuna del pronostico di Giovanni Lichtenberger.” 36 For a more detailed account of Florentine predictions in the early 1490s, see Weinstein, Savonarola and Florence, pp. 62–66. 37 Paul of Middelburg, Invectiva, fol. a1v: “Cum tot occurrant undique vates, ne limphaticos dixerim larvatos supersticiosos et sortilegos, (…). Que tamen falsa semper et inania reddunt, factum est ut divina illa matheseos astrologica theoria tanquam inutilis et caduca reddita ab omnibus sit posthabita et neglecta, (…).” 38 Kurze, “Popular Astrology and Prophecy,” p. 191. Lichtenberger characterized his Pronosticatio in the very same terms. See Lichtenberger, Pronosticatio Latina, fols. a1v–a2r: “Et ut complectar rem particularius deus dedit homini triplicem futura predicendi viam (…) Prima via que omnium est communio, consistit in longa vita qua per longam experientiam rerum omnium magistram ex dudum preteritis per similitudinem & coniecturam futura predicere homo potest (…) Secunda via ex astris seu scientia astrorum (…) Tercia est via revelationum (…) Predictas tres futura sciendi vias autor presentis operis qui sese innominabilem compellabit amplectetur.”

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boundary-work between prognostication and prophecy. Middelburg’s decision to cast the problem in these terms was undoubtedly related to the popular impact of hybrid texts like Lichtenberger’s Pronosticatio. Understanding astrological critiques as responses to social problems also explains the attitude of Pico and his Florentine circle to Paul of Middelburg. When Pico mentioned Middelburg in the Disputations, it was not to discredit his prognosticatory work. Instead, Pico praised this “famous mathematician, now living at the court of Guido, the most learned duke of Urbino” for his criticism on contemporary interpretations of Ptolemy’s Tetrabiblos iii.10.39 In 1492, Ficino had already addressed an equally laudatory letter to Paul of Middelburg.40 Being a practitioner of conjunctionist astrology was not enough to lose Pico’s respect. What really mattered was the public’s response to such practices. This reveals a number of interesting parallels between Pico’s Disputations and Middelburg’s Invectiva. The latter ultimately condemned Lichtenberger’s work for being non-astrological, and justified this on both social and intellectual grounds. Pico’s Disputations adopted a similar attitude. While Pico initially defended the option of astrological reform, he ultimately conceded its practical irrelevance. In his opinion, astrological reform was ruled out by the popular impact of late fifteenth-century Italian conjunctionism: For [an error posing as wisdom] is nothing else than abstinence from deliberation and intellect, our sole innate power to remove falsity. Thus its lie gets away, more honest through testimony, more robust through power, better sustained through protection. Besides, there is no further hope for recovery where nature itself aids the disease. This happens -as I said just now- through an insanity which, under the mantle of an art or science, propagates and sells itself among the people. It is no less insane because it claims wisdom on the surface, and all the more pernicious as it is fallacious.41

39

Disputationes, vol. 2, p. 354. Ficino, Opera omnia (1576), p. 944. 41 Disputationes, vol. 1, p. 38: “Non aliud hoc, quam consilium et mentem, cuius sola vis abigendae falsitati nobis innata est, missam facere, ut mendacium ipsius, et testimonio honestius, et potestate robustius, et praesidio munitius, evadat. Porro nulli spes ad sanitatem, cum natura ipsa adiuvat morbum. Hoc autem, ut dudum dicebam, evenit per insaniam quae, sub specie vel artis vel scientiae, populo se circumfert et venditat, non ideo minus insane quod sapientiam summa cute mentitur, sed quo fallacior eo perditior.” 40

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Pico abandoned astrological reform for outright rejection. Conjunctionist astrology had already adopted different criteria for “good” astrology than the ones that he listed in chapter iv.1 of the Disputations. But this situation was aggravated beyond recovery by its popular appeal (“sells itself among the people”). Given the context in which the Disputations were written, one may suggest that this social dimension in fact triggered Pico’s shift from reform to rejection. Another contributing factor was Pico’s independent status as count of Mirandola.42 This allowed him to defend a general theory of astrological physics without exploring Paul of Middelburg’s criteria for sound astrological practice. This preliminary analysis of Pico’s Disputations establishes two ways of reading his critique: as an exhortation to astrological reform and as a definitive rejection of astrology. Pico expressed this central motif most clearly in the introductory chapter of book iv, where he acknowledges that one can legitimately argue for and against the basic tenets of astrology. His ultimate adoption of a position against all astrology was motivated by the social challenges of popular astrological practice in the 1480s and 1490s, which threatened to compromise the relation between religion and natural science, and between God and human society. This implies that anyone who was willing to accept the fundamentals of astrological physics, and who did not find himself implicated in the socio-intellectual quagmire of late Quattrocento Italian astrology, could set aside the rejection in Pico’s accusations of impiety, and read the Disputations as an exhortation to astrological reform. This is exactly the kind of reading that several astrological practitioners would adopt in the sixteenth century.

2. The solution: Aristotle, mathematics, and experience Pico’s solution mobilized every ingredient of late medieval astrological practice. In the realm of astrological physics, Pico developed an alternative that was based on astronomical and Aristotelian concepts. In the realm of judicial astrology, he exposed the empirical limitations of common astrological data, as well as the inaccuracy of the instruments that produced them. However, the Disputations mostly

42

See Farmer, Syncretism in the West, pp. 312–313.

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derived its imposing size from its critique of data inscriptions in the textbooks that figured prominently in the canon of Latin judicial astrology. 2.1. Aristotle and astrological physics The late mediaeval Latin astrological canon encompassed widely divergent accounts of the relations between superlunary and sublunary causation, and between nature and chance. Practising astrologers commonly adopted epistemic secrecy to pre-empt such criticism. But local circumstances, functionally identical to Aristotle’s “common opinion,” might render this appeal to epistemic secrecy superfluous through the social impact of astrological predictions. This is what happened in the Italian prelude to Pico’s Disputations of the 1480s and 1490s. This spurred Pico to construct his argument against an astrological physics that he would have accepted under different circumstances. This argument is developed in the third book of Disputations around two central concepts: an Aristotelian account of the relation between heaven and earth on the one hand, and astronomical arguments concerning the distance and size of celestial bodies on the other. Pico identifies exactly two sources of celestial influence on earth: motion and light.43 In accordance with common scholastic opinion, he assumed that the daily motion of the universe sustains all motion in the sublunary realm.44 Light, on the other hand, has two distinct effects, as Pico explains most effectively in chapter iii.6.45 On the one hand, it transfers a celestial heat (calor caelestis) which penetrates everything, and without which even cold bodies cannot act accordingly.46 The other property of lux has a “virtue that consummates

43

Disputationes, vol. 1, pp. 194–208. Disputationes, vol. 1, pp. 194–196. Pico refers to Aristotle, Physics 256a sqq. The wider scholastic context is sketched by Grant, Planets, Stars & Orbs, pp. 588–591. 45 Disputationes, vol. 1, p. 196: “Nam, quando lux summa qualitas corporum, corporeae vero naturae primus vitae gradus (…), fit necessario ut lux et consumatricem quandam habeat corporum virtutem et vitale nonnihil interim possideat, non quod ipsa aut vivat aut vitam afferat, sed corpus vitae capax ad vitam maxime praeparat et disponit, quoniam sequitur lucem, quasi proprietas eius, calor quidam non igneus, non aereus, sed caelestis, sicuti lux caeli propria qualitas; calor -inquam- efficacissimus maximeque salutaris, omnia penetrans, omnia fovens, omnia moderans.” 46 Ibid., vol. 1, p. 196: “Calor quidam non igneus, non aereus, sed caelestis, sicuti lux caeli propria qualitas; calor –inquam- efficacissimus maximeque salutaris, omnia penetrans, omnia fovens, omnia moderans.” 44

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bodies,” and is therefore comparable to traditional Aristotelian heat as an efficient cause of sublunary change.47 Pico’s calor caelestis has often been identified with Ficino’s famous spiritus. A Stoic version of spiritus reached medieval academic culture through Galenic medicine, which identified it as a fine lucid matter, the material auxiliary of the nutritive soul in its communication with the rest of the body.48 Ficino’s Neoplatonic cosmology expanded the role of spiritus to the point where it became a cosmic principle that connects all hierarchies of the sensible world.49 Analogous to the human spirit, the spiritus mundi connects the World body to the World soul, and in fact constitutes the latter’s vehicle. “Spirit” assumed a central function in Ficino’s Neoplatonic world: it is the subtle carrier of participation across the different levels of reality, and thereby also established occult connections between material substances in the macro- and microcosm. This last feature Ficino claimed to have harnessed in the astrological technology of De vita coelitus comparanda, the famous third book of his De vita (1489).50 A closer look at Pico’s sources in Disputations iii.6 invalidates a Neoplatonic interpretation of his own calor caelestis. Instead, all available evidence points to Aristotle’s De generatione animalium as Pico’s predominant textual source.51 Unlike Ficino, Pico preserved spiritus in the Aristotelian-medical context where he first found it.52 This much can be inferred from the following remark on calor caelestis:

47 Ibid., vol. 1, p. 196: “Fit necessario ut lux et consumatricem quandam habeat corporum virtutem”; Ibidem, vol. 1, p. 218: “Cum nullam faciat elementarium qualitatum, utpote ab illis sua propietate diversus, degenerat tamen in elementari natura ad actiones elementorum, praecipue vero caloris cui, sicuti nomine, ita natura proximat magis.” 48 On medieval and early modern notions of spiritus, see Fattori/Bianchi eds., Spiritus. On medical usages, see Hill, “The Grain and The Spirit in Mediaeval Anatomy”; Zanier, “Platonic Trends in Renaissance Medicine”; Siraisi, “The Music of Pulse.” 49 Kristeller, The Philosophy of Marsilio Ficino, pp. 115–120. The identification of Ficino’s spiritus with Pico’s calor caelestis is habitually derived from the analysis of Walker, Spiritual and Demonic Magic, pp. 54–59. 50 For an introduction to Ficinian magic, see Walker, Spiritual and Demonic Magic, pp. 3–59. 51 The modern editor of Pico’s Disputations, Eugenio Garin, identified six references to Generation of Animals in Disputationes iii.6, excluding the paraphrase of Generation of Animals 736b35–36 that is discussed below. 52 This attitude may be traced back as far as Pico’s Heptaplus iv.1 (1489), where the theory of spiritus is attributed to physicians and philosophers (medici et philosophi), identified as Avicenna and Aristotle. Spiritus, however, does not carry the universal cosmological function that Ficino attributes to it. See Pico, Heptaplus, ed. Kieszkowski, p. 74.

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chapter three For no [sublunary matter] is more akin [to celestial light] than the spirit, particularly the human one, that sanguine, subtle, clear, and mobile vapor which corresponds by analogy to the heavens, as Aristotle and Avicenna write.53

Here, Pico seems to refer to a passage in Aristotle’s De generatione animalium ii.3.54 That work introduced “spirit” (πν况α) as an efficient cause for the development of complex natural substances.55 Given the continuity between embryo and adult human being, one could naturally assume that both shared a single substantial form. It was more difficult to explain, however, how simple substances like seed could consistently develop into humans through the ubiquitous and hence quite random efficient action of the four elements.56 Aristotle solved this by invoking an autonomous substance, a “breath (πν况α) included in the semen” which sustained vegetative and sensory souls.57 “Pneuma” made it possible to save the causal explanatory autonomy of living things. It seems that Pico’s astrological work adopted the theory for the very same reason.58 Pico’s statement departs from Ficino in its firm separation of calor caelestis from spiritus. Pico’s astrological physics accorded little

53 Disputationes, vol. 1, p. 218: “Etenim nulla [materia] potius talis [cognata est] quam spiritus, et praesertim humanus, qui sanguineus vapor, tenuis, clarus, mobilis, caelo, quemadmodum scribunt Aristoteles et Avicenna, proportione respondet.” 54 Pico paraphrases Aristotle, Generation of Animals 736b35–36. Due to its centrality in discussions on the individual immortality of the human soul, Pico could not have failed to notice this notorious text in his Paduan years (1480–1482). See Mahoney. “Giovanni Pico della Mirandola and Elia del Medigo.” For a brief review of Pico’s statements on the issue of individual human immortality, see Roulier, Jean Pic de la Mirandole (1463–1494), pp. 368–370. 55 The literature on Aristotelian notions of πν况α is immensely fascinating. For an introduction, see Freudenthal, Aristotle’s Theory of Material Substance; Nussbaum, Aristotle’s De Motu Animalium, pp. 143–164; Aristotle, Generation of Animals, ed./trans. Peck, pp. 576–593; Balme, Aristotle’s De Partibus Animalium I and De Generatione Animalium I, pp. 158–165. A related discussion is summarized and expanded upon in Sauve Meyer, “Aristotle, Teleology, and Reduction.” 56 A very general review of late scholastic answers to this question is provided by Des Chene, Physiologia, pp. 161–166. For a less problematic account of the role of forms in generation (which squares rather well with Pico’s own solution), see Hankinson, Cause and Explanation in Ancient Greek Thought, pp. 142–144. 57 Aristotle, Generation of Animals 736b36. 58 The question of Pico’s allegiance to either Aristotelian or Neoplatonic cosmologies will not be addressed at present. A wonderful basis for approaching this thorny issue is Kristeller, “Giovanni Pico della Mirandola and His Sources.” See also Allen, Icastes: Marsilio Ficino’s Interpretation of Plato’s Sophist, pp. 34–48. For an alternative account of Pico’s syncretism, see Farmer, Syncretism in the West.

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or no Neoplatonic potential to spiritus or calor caelestis.59 Instead, celestial heat simply sustained the proper operations of all sublunary qualities, including those of spirit in living things, by diffusing itself universally.60 The relation between celestial heat and sublunary efficient causes was hence analogous to that between sublunary vital heat and the four manifest qualities.61 Briefly stated: no change occurred in the sublunary realm without the heavens; but the nature of that change was primarily determined by sublunary secondary causes.62 Pico carefully explained this last point in Disputationes iii.6. He states that celestial heat has no elemental qualities in itself. Still, it easily “degenerates” into these as it is received by “vitiated” sublunary matter, and is most akin to elementary heat when this happens.63 Inspired by the Aristotelian view that hot/cold are active and moist/dry passive, Pico explains that the stronger light of the sun accidentally causes dryness by evaporation.64 The more tepid light of the moon, on the other hand, may accidentally educe terrestrial humidity.65 Such accidental elemental effects are linked to the astronomical position of both celestial bodies: when the moon is waning, her decreasing heat educes more vigorous vapors, causing “insalutary” rains and

59 It is probably possible to interpret this episode as a partial dissolution of the Florentine elitist alliance between utilitarian magic and ancient philosophical traditions, under the constraints of the popular impact of one component in this alliance. See Long, Openness, Secrecy, Authorship, pp. 148–154. 60 Disputationes, vol. 1, p. 208. 61 Ibid., vol. 1, p. 200: “Igitur, si calor iste [caelestis] perfectione virtuteque continet corporum inferiorum omnes qualitates, omnes etiam cum causis illarum proximis et generabit et vegetabit; sicuti calor ipse seminalis, licet calor est et dicitur, materiam tamen omnem fetus, sive illa calida [est] sive frigida, regit, digerit, servat, format, moderatur.” 62 Ibid., vol. 1, p. 208: “Ita patet in corporeo mundo nihil quidem fieri sine caelo; verumtamen quod hoc aut illud fiat, id a caelo non esse, sed secundis causis, cum quibus omnibus caelum talia facit qualia ipsae facere natae sunt, sive illae ad species, sive ad individuum, causae pertineant.” 63 Ibid., vol. 1, p. 218: “(…) cum nullam faciat elementarium qualitatum, utpote ab illis sua proprietate diversus, degenerat tamen in elementari natura ad actiones elementorum, praecipue vero caloris cui, sicuti nomine, ita natura proximat magis.” 64 These passages point to Aristotle’s Meteorology iv as another possible source of Pico’s astrological physics. See Aristotle, Meteorology 378b10–379a11. 65 Disputationes, vol. 1, pp. 220–222: “Sed in idoneis affinibusque subiectis nec exsiccabit radius Solis humorem salutarem, nec generabit Luna inutilem noxiamve humiditatem, sed operabitur idem sua natura sidus utrumque, licet Luna remissius quod intentius Sol efficiet; ex accidenti vero, per infectionem peregrinae materiae, dissimiliter illis eveniunt, Sol ut exsiccet, Lunae ut humefaciat.” On hot/cold as active principles, see De generatione et corruptione ii.2, 329b20–33.

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menstruations. The waxing moon, on the other hand, instills an invigorating humidity. Similar differences occur in the sun’s annual motion along the ecliptic, or daily motion over the local horizon.66 Likewise, the luminaries may accidentally cause coldness as their heat decreases or increases.67 Of their own accord, celestial bodies sustained the very possibility of autonomous sublunary change. But Pico also believed that sublunary substances were often incapable of receiving this beneficial influence. In that case, it degenerated into an effect, similar to that of elementary heat. Depending on the amount of celestial light that was received, this effect apparently manifested itself as either of the four manifest qualities. Pico’s astrological physics codified a partial role for the heavens in sublunary change. This enabled Pico to argue for an astrological theory, based on the interaction between celestial causes and sublunary proximate causes. The underlying concern for explanatory autonomy in the sublunary realm, was forcefully expressed in Pico’s insistence that lions were born from lions, and horses from horses, under any celestial configuration.68 The alternative was to live in a world populated by monsters: “Aristotle states that when some son is not formed according to the seed of his parents, deriving his likeness from them, he should be ranked with the monsters.”69 Paradoxically, a certain reading of Ptolemy’s Tetrabiblos may have inspired Pico’s astrological physics. Since Aristotelian physics upheld a strict distinction between superlunary and sublunary matter, it was commonly held that these descriptions did not express the nature of the heavenly bodies as such. Instead, there are indications that Ptolemy interpreted his astrological physics in terms of an interaction between heat imparted by the heavens, and moisture that is present in sublunary substances. Although Saturn’s nature was described as cold and dry, this was “probably because it is furthest removed both from the sun’s heat and the moist exhalations about the earth.”70 Other passages in Tetrabiblos strongly suggest that Ptolemy

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Disputationes, vol. 1, p. 222. Ibid., vol. 1, pp. 222–226. 68 Ibid., vol. 1, pp. 188–190. 69 Ibid., vol. 1, p. 268: “Si quis pro parentum seminibus filius non effingatur et inde ducat suam similitudinem, monstris enumerandum dicat Aristoteles.” 70 Tetrabiblos, pp. 35–37. Note that Ptolemy refers to such terrestrial exhalations with the term ˆνα©υµÝασισ. Aristotle’s Meteorology describes this as the evaporation of the element of water by the sun’s heat (see 346b16–347a11). 67

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only accepted hot and wet as authentic physical categories of celestial influence. By this token, cold and dry were in fact accidental qualities, privations of heat and moisture. 2.2. Mathematical astronomy and astrological physics This agreement between Piconian and Ptolemaic astrological physics underlines how Aristotelian physics could not halt basic astrological claims. The accidental nature of celestial influence on sublunary elemental qualities did not disprove its operational relevance, as indicated by Ptolemy’s remark on Saturn’s effects. In order to counter this argument, Pico turned to mathematics.71 First of all, he proposed that, ceteris paribus, propinquity determined the relative effect of celestial light.72 By this criterion Pico claimed that all celestial bodies, apart from sun and moon, were either too small or too distant to have any notable effect. Cicero too had made this point, but Pico supports it with much greater detail, taken from the Ptolemaic astronomical tradition.73 Distance obstructs any effect of Saturn and Jupiter, while Mars’ decrease in size exceeds its greater proximity, the sun being almost 100 times larger. For Mercury and Venus too, the ratio between distance and size is largely inferior to that of sun and moon.74 The first parameter, distance, was supplemented with two others: the quantity and density of a celestial body’s light. Pico emphasized that the proportion of these three factors had not been established, and could not be estimated through experience for other planets besides sun and moon.75 According to size (parameter 2), Mars should have been less hot than Saturn or Jupiter. The objection that Mars’

71 The basic material for a comparative study of the role of mathematics in Pico and Ficino’s astrological thinking has recently been provided in: Allen, “Marsilio Ficino: Daemonic Mathematics and the Hypotenuse of the Spirit.” 72 Disputationes, vol. 1, p. 242. 73 Cicero, De divinatione, ed./trans. Falconer, p. 475. See Van Helden, Measuring the Universe. Cosmic Dimensions from Aristarchus to Halley. 74 Disputationes, vol. 1, p. 250. 75 Ibid., vol. 1, p. 230: “Tria enim fere facient intentionem caloris, magnitudo lucis, densitas et propinquitas. Non est autem ad liquidum exploratum quantum magnitudo densitati, quantum densitas magnitudini, quantum alteri vel utrique praeponderet ipsa propinquitas; quare ratiocinari volentibus in incerto res erit, nec arbitrari poterit sensus, cum praeter Solis et Lunae ceterorum radios non persentiat; et hoc primum obstat astrologis quorum ars nulla, si remanent in ambiguo vires caelestium radiorum.”

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compactness76 and vicinity (parameters 3 and 1) compensated for this, was no less incredible to Pico: how could Saturn be cold, and Mars hot, if the former is 50 times the size of the latter? And if the relative importance of the size of the emitting planet were small, but that of the distance great, then this would imply that Venus should influence us more than any other planet (apart from the luminaries), notwithstanding the fact that many astrologers attribute coldness to her.77 This critique eliminated the complexity of astrological practice by reducing it to two bodies (Sun and Moon) only. Pico’s mathematical approach to astrological physics continued an old tradition that seems to have reached the Latin West through the De radiis of al-Kindi (d. c. 873).78 In this work, al-Kindi describes the effects of the stars in terms of rays that propagate their proper virtues to the earth. While these rays are dispersed in every direction of the universe, their strength is taken to diminish with distance. The English friar Roger Bacon developed this theory into a comprehensive natural philosophy by combining it with optics. The conjunctionist theories against which Pico reacted and the optical model which he adopted were closely entwined in Bacon’s own work, and Pico may have encountered both while preparing his Conclusions,79 or when he borrowed one of Bacon’s astrological tracts from the Vatican Library on 3 January 1487.80 His acquaintance with the optical model may also have been reinforced during his subsequent studies in Paris, where he was introduced to the astrological critiques of Henry of Langenstein (c. 1325–1397) and Nicole Oresme (c. 1320– 1382).81 The latter had pursued this enterprise furthest in no less than six works.82 Although his Quaestio seems to contradict itself on 76 Pico here seems to assume a converse ratio between the size of the emitting surface and the intensity of the emitted light. 77 Disputationes, vol. 1, pp. 230–232. 78 Travaglia, Magic, causality and intentionality. The Renaissance reception of alKindi’s work is discussed in Burnett, “Al-Kindi in the Renaissance.” 79 Farmer, Syncretism in the West, p. 452. 80 Bertola, I primi due registri di prestito della Biblioteca Apostolica Vaticana, pp. 79–80. 81 Disputationes, vol. 2, p. 530: “Ubi vero in Academia parisiensi primitus apparuit [astrologia] (…) restiterunt eis viri doctissimi Guilelmus Alvernius episcopus Parisiensis, et post eum Nicolaus Oresmus mathematicus excellens, et Henricus ex Assia, et Ioannes Caton, et Brenlanlius Britannus astrologiam.” Pico quotes verbatim from Oresme’s Quaestio in chapter x.11, which discusses the association of zodiacal signs with different parts of the human body (see Caroti, “Nicole Oresme’s Polemic,” p. 75). He also refers to Oresme’s De proportionibus in Disputationes, vol. 2, p. 14. 82 For a general introduction to Oresme’s life and work, see Marshall Clagett, “Oresme, Nicole” in: Gillispie (ed.), Dictionary of Scientific Biography, vol. 10. The classic study on Oresme and astrology is Coopland’s Nicole Oresme, which must now

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this point, Oresme at least once preceded Pico in stating that the heavens imparted motion and light, but no other influences.83 Popular in previous scholastic epistemological work, the optical model had enabled Oresme to buttress his claims on celestial influence.84 Pico’s astrological physics broke down astrology’s monopoly over efficient causation, and imposed doubt about its absolute relevance by adopting the same model. 2.3. The value of common astrological experience Most of the Disputations’ size did not derive from Pico’s analysis of the theoretical problems of astrology, probably because its immediate target was a specific kind of astrological practice. Instead, he focused on various problems concerning the accumulated practical experience that Latin astrologers claimed to possess. 2.3.1. The antiquity of empirical records Astrological experience was unreliable by its limited antiquity. In book xi of the Disputations, Pico argued that the history of astrology did not stretch back far enough in time for it to have yielded a sufficiently high number of reliable observations.85 Since the biblical be combined with Stefano Caroti’s work. See Caroti, “La critica”; Caroti, “Nicole Oresme’s Polemic.” Oresme’s anti-astrological work is contained in: De configurationibus qualitatum et motuum, ed. Clagett in: Nicole Oresme and the Medieval Geometry of Qualities; Tractatus contra iudiciarios astronomos, ed. Coopland in: Nicole Oresme and the Astrologers; Le livre de divinacions, ed. ibidem; Quaestio contra divinatores horoscopios, ed. Caroti; Quodlibeta, ed. Hansen in: Nicole Oresme and the Marvels of Nature. 83 See Oresme’s conclusions to the Quaestio, ed. Caroti, p. 277. It should be noted that Oresme at one point does seem to accept the action of an occult influentia (see Quaestio, ed. Caroti, p. 228). 84 See Quaestio, ed. Caroti, p. 274: “Decimo, nota quod omne corpus luminosum, aut etiam habens aliam virtutem ut influentiam, vel etc., agit seu illam diffundit sperice. In omni enim actione est imaginanda figura pyramidalis, cuius basis est ipsum agens aut pars eius, et conus est in passo, et hoc etiam patet in Perspectiva. Et quod quanto pyramis est brevior et obtusior, tanto actio et virtus est fortior, ceteris paribus: patet hoc in Perspectiva; et quod actio fit fortius secundum lineam perpendicularem, quam secundum aliam; et quod linea perpendiculari existente ab agente [punctus sive] in puncto remotiori ab agente est semper actio debilior ceteris paribus. Patet hoc etiam in Perspectiva, nec valet instantia de speculo concavo reflectente etc., quia in speculo congregantur plures radii in uno puncto etc., non est igitur una linea ibi sed multe congregate; et de terra dicitur quod ibi sunt radii incedentie et reflexionis, ideo et etiam terra est magis apta ad etc.” On optics and epistemology in scholastic culture, see Tachau, Vision and Certitude in the Age of Ockham. Also see Lorcin, “Le soleil, l’oeil et la vision au moyen âge.” 85 Disputationes, vol. 2, p. 472.

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Flood occurred about 4000 years before his own time, Chaldean observations spanning 470,000 years had to be a fiction.86 Pico proved this point with various references to the Deluge, and with Porphyry’s testimony on the Babylonian records brought back to Greece by Callisthenes. Equally important was Ptolemy’s Almagest as a source for the ancient history of astronomy, since it underscored the primitive nature of Babylonian and Egyptian observational methods.87 Reference to the biblical Flood of course provoked the objection that God had subsequently revealed astrological knowledge to man. Pico retorted with the circular argument that astrology’s frequent clashes with other sciences made it impossible that this was a gift from God.88 The disease proved its origins, so to speak. 2.3.2. The inaccuracy of astronomy In chapter ix.8, Pico observed that astronomical predictions were entirely dependent upon the quality of the observational data underlying their models. This was hindered by the precision of observational instruments, and especially by the limited detail of their graduations. Another obstacle to the accuracy of observations was the refractive effect of varying atmospheric conditions. Both factors implied that any astronomical table was subject to a periodical correction (castigatio) on the basis of new observations.89 Reviewing the different values reported for the tropical year between Hipparchus (fl. 160–125 bc) and the thirteenth century, Pico showed that even the tropical motion of the sun was not established beyond reproof.90 He further highlighted discrepancies in the theories for Mercury and Mars.91 The astrological consequences were obvious, since an astronomical error of just one degree could yield erroneous astrological predictions.92 2.3.3. Contradictions in the astrological canon The impact of Pico’s critique of astrological experience was directly dependent upon the extent to which one accepted his previous de86 Disputationes, vol. 2, p. 474. Pico probably took the reported figure of 470,000 year-old observations from Cicero, De divinatione ii.97. 87 Disputationes, vol. 2, pp. 476–484. 88 Ibid., vol. 2, p. 486. 89 Ibid., vol. 2, pp. 322–324. 90 Ibid., vol. 2, pp. 326–330. Pico’s viewpoint on the problem of precession is further developed in chapter ix.11 (Disputationes, vol. 2, pp. 338–348). 91 Ibid., vol. 2, p. 330. 92 Ibid., vol. 2, pp. 332–338.

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cisions on mathematical precision and astrological impiety. At least the latter was primarily rooted in Pico’s specific local context, for which reason he sought further reinforcement of his claims in a strategy that contributed most to the volume of the Disputations. This strategy aimed at unmasking the mutual inconsistencies of Western Latin astrological traditions. Pico made this clear at the beginning of chapter ix.12, when he wrote that: The mathematicians inflict mutual wounds upon each other, and so experience –no matter how old- cannot rely on equal authority against [this], nor arbitrate any matter whatsoever.93

This chapter contained one of Pico’s most spectacular exposures of internal contradictions, devoted to the genethliacal practice of prorogation (directio) in Tetrabiblos iii.10. Ptolemy had stated that the time-span of a particular person’s life could be likened to an arc of the zodiac. At birth, a person’s life was “launched” at a certain point (the prorogator), from where that person started a lifelong journey along the zodiac. This journey was symbolized by a steady progression of his initial point, during which time it would encounter one or several destructive points or planets (the ˆναÝρετα, henceforth transliterated as “anaereta”) that represented serious threats to life, or even the individual’s death (see chapter 8). Pico pointed out that the “Egyptians” counted the distance between prorogator and “anaereta” in degrees of oblique ascension, while Dorotheus of Sidon and Abraham Ibn Ezra preferred to use degrees of right ascension. Ptolemy and others, however, employed both systems as well as a more exotic one, depending upon the specific kind of horoscope that was under scrutiny. Albumasar in turn preferred ecliptic degrees, with which Ibn Ezra’s Initium sapientiae somehow agreed on the authority of Albategnius. John of Seville’s popular handbook advocated yet another combination of techniques, as did Messahalla.94 One can readily understand how these typical narratives combined to question the authority of the late medieval Latin astrological canon. It is indicative of Pico’s reformist attitude that he sometimes used these contradictions to recruit support for his own astrological physics. In book viii, he argued that the ubiquitous zodiacal signs

93

Ibid., vol. 2, p. 350: “Nam mutuis utrobique vulneribus confodiunt se mathematici, nec niti aequalem ita adversus auctoritatem, vel arbitrari rem quamque vel tot aetatum experientia potuit.” 94 Ibid., vol. 2, pp. 350–354.

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should be interpreted as mnemonic signs for a celestial influence that was caused by both luminaries, sun and moon.95 He reinforced this radical view with the authority of some traditional astrologers, notably Abraham Ibn Ezra and Haly Avenrodoan.96 Pico aptly transformed an equivocal passage in Ibn Ezra’s Liber rationum on the unclear nature of zodiacal signs into a statement on their arbitrariness.97 Another reference presented Ibn Ezra as a forebear of Pico’s statement that the stars imparted heat only.98 A similar ambivalence characterizes Pico’s attitude towards the commentary on Tetrabiblos of Haly Avenrodoan. On the one hand, Pico enthusiastically endorsed his views on the efficacy of the zodiac: For when one says that a certain property and influence belongs to one sign, and a different one to another, this can be true in two ways: either because stars meeting in that part of a sign are predicated to have this power, so that the efficacy that belongs to the host is attributed to the guest, or because the sun, when arriving in that sign, effects such things (…) For when Avenrodoan wished to explain and comment upon the opinion of Ptolemy, so to speak with his pen immersed in the river of truth, he almost involuntarily erased and expunged Ptolemy. For he asserts that the parts of a circle have no effect, and that the things which are thought to happen through them, are roused by the activity of the sun or of other stars in those parts.99

Pico was less devoted to Haly where the Commentator seemed to depart from Pico’s astrological physics. When Haly connected both the sun and Saturn to the sign of Cancer, he incurred Pico’s vehe95

Ibid., vol. 2, pp. 224–285. Pico summarizes his opinion on Avenrodoan and Ibn Ezra in chapter ii.6: “Contra Avenrodan nullum fuisse locutum in astrologia cum ratione ait praeter Ptolemaeum, et quod si inspexeris dicta aliorum invenies ea multum a veritate remota, dicta vero Ptolemaei nullo modo posse falsa reperiri. Hebraei quoque Hebraeorumque primus Abraham Avenazra dissentit a Ptolemaeo, et Albumasarem saepe laceravit, immo totum eius librum qui latine censetur de magnis coniunctionibus abiciunt atque repudiant?” (Disputationes, vol. 1, pp. 140–142). 97 Disputationes, vol. 2, p. 246. 98 Ibid., vol. 1, pp. 228–232. 99 Ibid., vol. 2, pp. 248–250: “Cum autem huius quidem signi talem, alterius aliam esse proprietatem et influentiam dicunt, duplici hoc ratione habere veritatem: aut quoniam stellae, in ea tunc signi parte convenientes, tali potestate praeditae sunt, ut quae hospitii dicitur hospitis sit efficacia; aut quoniam Sol ad signum illud perveniens, talia operatur (…) Nam opinionem Ptolemaei Avenrodan dum exponere cupit et declarare, stylo, ut ita dixerim, in amne veritatis immerso, obliterat vel invitus penitus et expungit. Asserit enim circuli partes nihil efficere, et quae fieri ab eis putantur, ea operatione vel Solis, vel stellarum in illis partibus agentium, excitari.” As the last sentence makes clear, Pico remained hesitant concerning the irrelevance of “other stars” besides the sun, which he had previously expunged from his optical model. 96

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ment opposition.100 And when other astrologers were seen to present different significations and connections, Pico happily exposed this in order to discredit any appeal to authority. Al-Kindi, for instance, argued for Cancer’s humid nature, not the fiery nature that one would expect from the fact that the sun is high in the sky when in Cancer.101 This iconoclastic dissection of the astrological canon was combined with a humanistic veneration of philology. In chapter ii.7, Pico emphasized the carelessness of astrologers towards their texts as an example of their general ignorance. Underscoring his habit of reading Ptolemy in the original Greek, rather than in a “common translation” (vulgata translatio), Pico argued that two common astrological practices (annual predictions and prorogations) had been corrupted with respect to the original methods of Tetrabiblos.102 2.4. The shape of astrological reform This last statement implied a qualified respect for Ptolemy’s Tetrabiblos. In fact, Ptolemy’s astrological work often escaped Pico’s critique of the astrological canon.103 This becomes clear when we inspect Pico’s sketch of an acceptable predictive art (which he never called astrology). Like Ptolemy, he traced the ancestry of this art back to the meteorological lore of ancient mariners, farmers, and physicians. Unlike Ptolemy, he presented his own alternative as a restriction, not an expansion of these venerable traditions. Mariners used the phases of the fixed stars to predict storms on the Persian sea or propitious days for navigation as indicators, not as causes, for use by the illiterate and unlearned.104 Likewise, Pico developed an elementary lunar astrology which rejects the account in Tetrabiblos ii.8,105 but accepts that of ps.-Ptolemy’s Centiloquium 56, namely that the moon augments humidity in the first quarter, and decreases it in the other three.106 100

Disputations, vol. 2, p. 390. Ibid., vol. 2, p. 112. 102 Ibid., vol. 1, pp. 144–156. 103 This section develops a suggestion made by Grafton, Commerce with the Classics, p. 112, on the legacy of Ptolemy’s critical approach in Pico’s work. 104 Disputationes, vol. 1, pp. 282–286. 105 Tetrabiblos, p. 45: “For in its waxing from new moon to first quarter the moon is more productive of moisture; in its passage from first quarter to full, of heat; from full to last quarter, of dryness, and from last quarter to occultation, of cold.” 106 Disputationes, vol. 1, p. 298. Compare to Ps.-Ptolemy, ΚαρπÞσ [Centiloquium], ed. Boer, p. 50. After Giovanni Pico’s death, Gianfrancesco Pico wrote to Battista da Mantova that he had found a manuscript translation of the Centiloquium among his 101

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This astrologia lunaris in turn became a tool for the critical evaluation of didactic poems like Hesiod’s Opera et dies or Virgil’s Georgics.107 When Pico came across Virgil’s verse “septima post decimam felix et ponere vites” (Georg. i.284), the reading that it was beneficial to plant vines on the 17th day of the lunar cycle was abandoned for its lack of conformity with lunar astrology; according to Pico, it was much more reasonable to interpret Virgil as referring to two propitious days, the 7th and the 10th. Pico further confirmed that Hesiod’s precepts for castrating males of various species, or predicting the birth of female animals, also mostly derived from the moon’s effect on the flux of bodily humors.108 In medical astrology, Pico explained the astrologer’s belief that the moon in Cancer causes scurvy through the general dryness of matter when the sun is in this sign.109 Physicians were advised to take into account the waxing and waning of the moon, so that the flux of humors does not harm patients, for instance when performing venesection.110 Last but not least, Pico set out to rewrite astrological chorography, the connection between celestial bodies and the characteristics of terrestrial regions or peoples. Pico took the five zones theory as his basis, and concluded that the nations on mean latitudes were generally more humane, prudent, wise, and apt to reign.111

3. Astrology demonized: Girolamo Savonarola’s attitude to astrology Pico’s close ties with the Dominican Girolamo Savonarola (1452– 1498) have often been cited as another trigger for the composition of the Disputations; I see no reason not to adopt this explanation.112 It was Pico who convinced Lorenzo de’ Medici in 1490 to bring Savonarola back to Florence. Four years later, it was Savonarola who uncle’s papers. It is likely that this was a copy of the new translation by Giovanni Pontano. See Garin, Giovanni Pico della Mirandola, p. 50. 107 My description of Hesiod and Virgil’s works as agricultural poems is based on the classification of Renaissance didactic poetry in Ludwig, “Neulateinische Lehrgedichte”; it is no accurate characterization of these poems from the standpoint of modern classical scholarship, but does reflect the general perception among readers in Pico’s age. 108 Disputationes vol. 1, pp. 300–302. 109 Ibid., vol. 1, pp. 278–280. 110 Ibid., vol. 1, pp. 302–304. 111 Ibid., vol. 1, pp. 286–290. 112 On Savonarola’s prophetic activity and his relation to Pico, see Weinstein, Savonarola and Florence; Garfagnini, “Savonarola tra Giovanni e Gianfrancesco Pico.”

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stood by Pico’s deathbed, and who later buried him in a Dominican habit in the church of San Marco, near the grave of Pico’s dear friend Poliziano.113 Savonarola’s status as self-proclaimed prophet was evidently endangered by the increasingly vague distinction between prophecy and prognostication.114 Pico’s opponent Lucio Bellanti in fact claimed that Paul of Middelburg’s warning of the advent of a false prophet had awakened Savonarola’s concern with the 1484 predictions.115 There is strong evidence, therefore, that Pico’s concerns over the proper demarcation between supernatural and natural knowledge were indeed stimulated by his close contacts with Savonarola. But this does not imply that Pico’s solution to the problem was indebted to Savonarola, as many interpretations of the Disputations would have it. The Conclusions (1486), written well before Pico’s acquaintance with Savonarola, contained two theses on the nature of mundane astrological effects that fit in well with the general subjectmatter of the Disputations.116 Much more extensive information on Pico’s idiosyncracy comes to us from Savonarola himself, who published his own astrological critique in 1497.117 The most striking characteristic of this treatise was its complete lack of interest in the arguments that constituted the bulk of Pico’s Disputations. Although Savonarola happily reinforced his own message with references to Pico’s critique, he opposed an outright demonization to Pico’s subtle interplay between reform and rejection. Savonarola argued that the human conviction that it was possible to know and avoid (or embrace) certain celestial effects was in fact inspired by demons.118 He construed astrology as heretical, a satanic practice that was beyond redemption in both natural-philosophical and moral terms. Although Pico was not entirely averse to demonic 113

Weinstein, Savonarola and Florence, pp. 100–101 and 211–216. Weinstein, Savonarola and Florence, chapter ii (pp. 67–111). 115 Bellanti, Defensio astrologiae, fols. q2r-q2v: “Mirum autem est, ut tam brevi temporis spatio astrologiam falsam abiciendamque deprehenderit [Picus], nisi forte veri luminis particeps factus ab eo (quem sepissime consulebat) fratre Hieronymo Savonarola, omnem veritatem sit complexus, cuius suasu hoc opus scripsisse credendum est (…) Nam multis ante temporibus, falsi prophete adventum astrologia denunciavit: ut inter cetera apparet, per prognosticum singularis viri Pauli Theutonici, qui aperte talia in religionem monstra iam diu dictis & scriptis fore ostendit. Cui si (ut par erat) creditum fuisset, & populis & Christi religioni plurimum conduxisset.” 116 Farmer, Syncretism in the West, p. 313 (conclusions 23.7–8). 117 Savonarola, Contro gli astrologi, ed. Gigante. The first edition was entitled Tractato contra li astrologi ([Firenze: Bartolomeo de’ Libri, 1497]). 118 Savonarola, Contro gli astrologi, ed. Gigante, pp. 119–124. 114

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intervention as an explanans himself, this never superseded his natural-philosophical, historical and textual arguments. Savonarola’s attitude reminds us how difficult it was to accept the exceptionally varied combination of cultural resources in the Disputations. The number of environments that could simultaneously support humanist historicism and philology, innovative Aristotelianism, advanced mathematical traditions, and late medieval Latin astrology was quite limited in late fifteenth-century Europe. The urban courts of northern and central Italy uniquely blended these cultural currents, in a way that was then only beginning to assert itself in those transalpine regions of the Holy Roman Empire that profited from an expanding urban commerce. Savonarola would soon demonstrate that even the political and cultural power of Medici patronage had its limits. By that time, however, the discourse of Italian humanism had started to flourish in at least some cultural centers of transalpine Europe. When the worth of astrological knowledge became problematic there, it initiated a process that gradually unfolded the full potential of Pico’s message.

CHAPTER FOUR

HUMANISM AND COURT ASTROLOGY: THE 1524 CONJUNCTIONS AT LOUVAIN

1. Introduction The first two decades of the sixteenth century marked the rise of humanism as a prominent cultural trend in the Low Countries. While this development emerged from several places at once (including several Latin schools, epistolary exchange, printing presses, and private academies), its most forceful cultivation was centered around Louvain. Through the printing press of Dirk Martens, the university town obtained easy access to the fine fleur of Italian humanism, including authors like Poliziano, Ermolao Barbaro, and Filelfo.1 Teachers like Martinus Dorpius adopted the didactic principles of Italian humanism, while the foundation of the Collegium Trilingue (1517) provided the local movement with an institutional identity that both Erasmus and Vives adopted.2 The work of Giovanni Pico played a significant role in these didactic innovations, as Marc Laureys has shown.3 The collection of Pico’s Auree epistole carried great weight as a suitable stylistic model for the teaching of letter writing. However, the interest in Pico was not limited to his relevance for the trivium. Richard Pafraet, whose production usually served the needs of the Deventer humanists, printed the first two books of the Disputations in 1502. The Parisian circle of Jacques Lefèvre d’Etaples, arguably the most influential proponent of Piconian ideas in northern Europe at that time, also exerted a strong influence on Louvain humanism. We will see that the emulation of Pico’s Disputations was part of this trend.4 This chapter provides a detailed study of the Louvain reception of Pico’s Disputations. It shows how astrologers with court connections 1 2 3 4

IJsewijn, “The Coming of Humanism,” pp. 231–232. IJsewijn, “Humanism in the Low Countries”; De Vocht, History. See Laureys, “The Reception of Giovanni Pico in the Low Countries.” See Renaudet, Préréforme et humanisme à Paris.

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firmly embraced Pico’s work. These practitioners mainly turned to the Disputations as a repository of arguments against popular predictions of a new biblical Flood in February 1524. One particularly influential messenger of these predictions was Gaspar Laet, son of Joannes Laet, who dominated the northern European market for annual prognostications from Antwerp. Laet, who studied medicine and astrology at Louvain, was well versed in the various traditions of Louvain academic astrology. Laet’s courtly opponents often adopted the humanist-scholastic debate as a broader framework for their discontent. Erika Rummel has carefully deconstructed this debate, showing how the distinction between humanists and scholastics was co-opted for various local purposes across early-sixteenth century Europe. What started out as a rather friendly display of epideictic rhetoric in Italy provided a structure for feuds between academic faculties in northern Europe in the period 1500–1520. Stepping away from Rummel’s focus on disputes between dialecticians and theologians, this chapter presents a debate among astrological practitioners over matters of expertise. Interestingly, their discussions led to an appropriation of the new confessional struggles after 1520, which confirms Rummel’s analysis.5 By adopting the humanist-scholastic dichotomy, court astrologers were able to recruit the support of those scholars and patrons who identified with these labels. The 1524 debates forged a firm alliance between humanist learning and astrological practice, which will be explored in subsequent chapters.

2. The 1524 conjunctions and the expectation of a new Flood In 1499, Johann Stöffler (1452–1531) and Jakob Pflaum published the first edition of their popular astronomical ephemerides, calculated for the period from 1499 to 1531.6 The table of planetary positions for February 1524 was followed by this remark: 5

Rummel, The Humanist-Scholastic Debate. Stöffler/Pflaum, Almanach nova. Despite having produced one of the most successful sixteenth-century astronomical tools, Stöffler and Pflaum’s mathematical work remains largely unstudied. On Stöffler, see Moll, Johannes Stöffler (1877); Karl Hartfelder, “Stöffler, Johannes,” in: Allgemeine Deutsche Biographie vol. 36 (Leipzig: Duncker & Humblot, 1893), pp. 317–318; Hellmann, “Aus der Blütezeit der Astrometeorologie”; Büttner, “Johannes Stöffler und die Beziehungen zwischen Geographie und Theologie”; Lamprey, “Georg Hartmann 16th-century astrolabes.” 6

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In this year we will see neither a solar nor a lunar eclipse, but most wondrous positions of the planets will occur. For in February there will be 20 small, mean, as well as great conjunctions, 16 of which will occupy a watery sign. These will signify indubitable change, variation, and alteration for almost the entire world, climes, kingdoms, provinces, estates, dignitaries, brutes, sea-creatures, and crops, such as we have rarely heard of for many centuries from historiographers, or our ancestors. Therefore lift up your heads, you Christian men.7

Most prominent in this note was a conjunction of Saturn and Jupiter, expected on 1 February in the sign of Pisces. A conjunction of Saturn and Mars, as well as of Jupiter and Mars, would follow on 5 February. In the meanwhile, the new Moon would rise on 4 February in Aquarius. While Stöffler and Pflaum hesitatingly limited themselves to predicting great “change, variation, and alteration,” the Italian astrologer Luca Gaurico (1476–1558) went on to present the 1524 conjunctions as causes of a second biblical Flood from at least 1507 onwards.8 The interpretation of this event as a natural calamity with religious significance in turn seems to have become common at least since the late 1510s. When Albert Pigghe (c. 1490–1542) quoted Stöffler and Pflaum in his Astrologiae defensio (1519), he added the phrase “or rather, inducing something like a second Flood, they threaten us with the submersion of nearly the entire world” as a summary of common astrological opinion.9 One may assume that this was not far from the truth, in view of the scenes that Ottavia Niccoli uncovered. All over the Italian peninsula, people prepared for the imminent disaster by taking refuge in the mountains, building up provisions on upper floors, or resorting to religious rites and preaching. An important stimulus behind the Italian attention to the 1524 predictions was the frequent experience of local floodings since the second half of the fifteenth century.10 7 Stöffler/Pflaum, Almanach, fol. gg2r: “Hoc anno nec Solis nec Lune eclipsim conspicabimur. Sed presenti anno errantium siderum habitudines miratu dignissime accident: In mense enim Februario 20 coniunctiones cum minime mediocres tum magne accident. quarum 16 signum aqueum possidebunt. que universo fere orbi climatibus regnis provincijs statibus dignitatibus brutis beluis marinis cunctisque terre nascentibus indubitatam mutationem variationem ac alterationem significabunt. talem profecto qualem a pluribus seculis ab historiographis. aut natu maioribus vix percepimus. Levate igitur viri christianissmi capita vestra.” 8 See Zambelli, “Many ends for the world.” 9 Pigghe, Astrologiae defensio, fol. 14r: “Immo secundum veluti diluvium inducentes, totius fere mundi submersionem minitantur.” 10 Niccoli, Prophecy, pp. 140–149.

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Over the course of the following six years, the expectation of a major Flood was increasingly shaped by this prophetic-religious element. In 1523, Cornelius Scepper (d. 1555) listed a new Flood the like of which had not been seen since Noah, great death-tolls, especially among women and Jews, wholesale destruction of crops, cities and towns, thunder and lightning, earthquakes, the death of illustrious kings, epidemics, the apparition of rainbows and of a fierce white star, and last but not least the upheaval of Christianity by the institution of new priests and a new council. The latter aspect seems to have gained importance with the Diet of Worms (1521), where several participants received pamphlets, using the 1524 predictions as propaganda for the Protestant cause by identifying the predicted religious change with the Lutheran revolt.11 The initial problem of the 1524 debates was very reminiscent of the one that spawned Pico’s Disputations in a previous generation (see chapter 3). In both cases, certain forms of judicial astrology (conjunctionist prognostications) commanded technological resources through which they generated considerable impact (printing technology and commercial distribution). The strong ties between conjunctionism and the astrological history of religions also implied a new threat to the beneficial relations between academic astrology and theology at Louvain (see chapter 2).

11 Use of the 1524-conjunctions as propaganda for the Lutheran cause was first suggested in Warburg, Heidnisch-Antike Weissagung. See also Scribner, For the Sake of Simple Folk. Previously, a bibliographical study of the 1524 debates had been published by Hellmann, Beiträge, vol. 1, pp. 10–21. The first extensive study of the debate was published in Thorndike, History, vol. 5, pp. 178–233. The research was taken up again around 1980 by Paola Zambelli, who embarked upon a fairly comprehensive analysis of the general motives and opinions underlying the approximately 160 publications related to these conjunctions in her “Fine del mondo o inizio della propaganda?” Valuable further research was presented on a two-day conference dedicated to this theme in 1984, and collected in “Astrologi hallucinati” (see note 8). Interesting additions to Zambelli’s research on the 1524 debates include Niccoli, Prophecy and People in Renaissance Italy (chapter 6) and Talkenberger, Sintflut. Other recent studies were (very) critically reviewed by Zambelli, “Eine Gustav-HellmannRenaissance?”

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3. Albert Pigghe and the return to Ptolemaic practice (1519) 3.1. An astrological practitioner at the French court In the early spring of 1519, the Paris printer Henri Estienne published Albert Pigghe’s Defense of Astrology.12 Pigghe was born in the early 1490s in Kampen, and enrolled at Louvain on 28 February 1507. His prodigious career at the arts faculty culminated on 3 April 1509, when Pigghe came out as primus among the new Louvain graduates. After an obligatory two-year teaching job at the arts faculty, Pigghe studied theology, graduating as baccalaureus formatus in 1517. He moved to Paris around this time. It is not unlikely that Pigghe publicly lectured on astronomy there, as his opponent Marcus Beneventanus later claimed.13 However, Pigghe’s Parisian career was not aimed at an academic career. Pigghe clearly tailored his Parisian publications to obtain a position at the court of François i (1494–1547) instead. The Defense of Astrology (1519) was dedicated to Galeazzo Florimonte (1484–1565), physician of Antonio Colonna and his representative at the French court.14 In 1520, Pigghe dedicated a calendrical treatise called On the Invention of the Equinoxes to François du Moulin de Rochefort (d. before 1526). Du Moulin, the former tutor of young François i at Amboise, had become the King’s chaplain in 1519.15 Pigghe also implemented his mathematical knowledge to suit the geographical interests of the French court. A luxurious manuscript containing a dialogue between François i and Caesar was probably written by du Moulin around 1520. Among the lavish illustrations in this manuscript, we encounter two Ptolemaic maps of western France, drawn by Pigghe in November 1520.16 12 Pigghe, Astrologiae defensio. On the dating of this treatise, see Thorndike, History, vol. 5, p. 186. 13 Quoted in Jedin, Studien, p. 49. 14 On Florimonte, see Pignatti, “Florimonte, Galeazzo.” At the court of François I, Florimonte was also in close contact with Lefèvre d’Etaples. 15 For information on Du Moulin, see Holban: “François du Moulin de Rochefort”; Idem, “Un témoignage inconnu”; Limouzin-Lanoble, “Du Moulin de Rochefort (François).” 16 A fac-simile reproduction of this manuscript was published by Dunoyer de Noirmont, Les commentaires. The inscription on the maps reads “Albertus pichius auxilio Godofredi pictoris batavi faciebat praecipiente francisco molinio Mense novembri sesquimillesimo vigesimo.” Significantly, another inscription states that these were constructed using the Geography of the “astrologus” Ptolemy. Pigghe’s geographical interests are also attested by his De progymnasmatis geographicis, written in Rome for

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Pigghe’s acquaintance with Du Moulin suggests that he had gained access to a close-knit group that was centered around the King’s mother Louise de Savoie (1476–1531). Astrological interests formed an important element of cohesion in this circle. Du Moulin has been named as the “ghostwriter” of Louise de Savoie’s Journal (with the latter’s consent), notable for its astrological arrangement and content.17 Another member of this circle was Du Moulin’s Franciscan protégé Jean Thenaud, whose position at court was based on literary, historical, astrological, and cabalistic texts in the vernacular that he composed for Louise de Savoie and François i.18 Between 1514 and 1533, Thenaud provided the royal family with several horoscopes and prognostications. His investigation of the appearance of three suns intersected by a white cross in 1513 shows that the royal court was acquainted with a prophetic interpretation of the 1524 conjunctions as early as 1514.19 The first book of his Triumphe des Vertuz, presented to the King in the summer of 1517, contained brief horoscopes for both François and his sister Marguerite d’Angoulême (1492–1549).20 In 1518, he was solicited to cast a horoscope for the newly born dauphin, accompanied by an elaborate interpretation. In 1533, he repeated this task for the King himself. Last but not least, Anne-Marie Lecoq has shown that Thenaud is the author of a French dialogue on the 1524 conjunctions, written around 1520.21 “Maistre Albert [Pigghe]” himself appears in this dialogue as the protagonist’s pope Clement vii and extant in several manuscripts. Lecoq, François Ier, pp. 229–244 comments upon Pigghe’s maps, indicating that Guillaume Budé too was a collaborator on this project. 17 This has been suggested by Dickman Orth, “Francis du Moulin and the Journal of Louise of Savoy,” following up on Griffiths, “Louise of Savoy and the reform of the Church.” 18 On Jean Thenaud, see especially Holban, “Le vrai Jean Thenaud.” Also Thenaud, La lignée de Saturne, ed. Masters/Jasenas; Lecoq, François Ier imaginaire; Thenaud, Triumphe, ed. Schuurs-Janssen. 19 Which Holban calls Traité des sept âges du monde, preserved in Paris, Bibliothèque Nationale, ms. Fr. 5106, fols. 32 sqq. Having been unable to check this source myself, I quote from Holban, “Le vrai Thenaud,” pp. 196–197: “La loy de Machomet s’imposa annonçant la venue de l’Antechrist. Ladicte secte commencée durera une haulte révolution et sera accomplie en 1524 en semblable conjonction dicelles haultes planettes au signe de Pisces (…) Item en cedit temps les Gotz et Magotz prindrent les seigneuries de leur païs qu’ils tiennent encore de présent et n’ont plus este subjects à princes et ne seront. Sainct Jean en son Apocalypse dict qu’ilz adhereront à l’Antechrist et qu’ilz seront destruicts.” 20 See Triumphe, ed. Schuurs-Janssen, pp. 24–25. 21 Lecoq, “D’après Pigghe, Nifo et Lucien.”

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advisor about the effects of these conjunctions. Pigghe also seems to have been the source of Thenaud’s knowledge of Nifo’s On the False Prognostication of a Deluge (1520), the treatise that directly influenced Thenaud’s dialogue. 3.2. Humanism and astrology The first part of Pigghe’s treatise contained a lengthy refutation of common methods for making annual prognostications. In the second part, Pigghe applied these objections to counter the widespread claim that universal calamities would follow the planetary conjunctions of February 1524. Interestingly, Pigghe adopted the debate between humanists and Parisian scholastics as a framework for his own discontent.22 Siding with the humanists, Pigghe called upon the King to take the lead in a combined reform of logic, theology, and astrology.23 This alliance between true astrology and the bonae literae was frequently emphasized in Pigghe’s Defense.24 It was further elaborated in the preface of On the Invention of the Equinoxes (1520), where Pigghe wrote that: Day by day [Germany] continues to bring forth so many champions of the best letters, that there is no nation nowadays over which it cannot claim primacy in the knowledge of languages and any kind of discipline. And as for that one matter which up to this time was wanting among the students of the bonae literae, who apply themselves much more to the knowledge of languages than of things (rerum), I would say that this is almost the only nation which embraces those mathematical and true disciplines with the greatest application. [Germany] especially cultivates, restores, and illuminates astronomy and cosmography.25

22 For an in-depth analysis of the controversy between humanists and scholastics, see Rummel, The Humanist-Scholastic Debate. 23 Pigghe, Astrologiae defensio, fols. 21v-22r. Pigghe’s scathing remarks seem to be indebted to those levelled in the fourteenth century against the preponderance of philosophy at the Paris theological faculty. See e.g. the letter of Pope Clement vi to the masters and students of Paris, dd. 20 May 1346, in: Chartularium Universitatis Parisiensis, ed. Denifle/Chatelain, vol. 2, pp. 587–589, nr. 1125. 24 See e.g. Pigghe, Astrologiae defensio, fol. 13v: “Haec omnia bonarum disciplinarum zelus, ac divina ipsa astrologia, quae a nugatoribus istis, tot contumelijs, ludibrijs, & iniurijs afficitur, pro se, me loqui iussere.” 25 Pigghe, De inventione, fol. 2v: “Tot protulit egregios & profert indies optimarum literarum vindices, ut nulla nunc sit natio, cum qua non possit & in linguarum cognitione, & omni disciplinarum genere, de primatu certare, & quod unum fere hoc tempore in studiosis bonarum literarum desiderabatur, qui linguarum cognitioni quam rerum nimio plus student, sola pene dixerim, aut, quod negari non potest,

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Likewise, Pigghe adopted a doxography that showed how illustrious names of the Latin astrological tradition shared his suspicions of conjunctionist astrology. Conjunctionist astrology, Pigghe claimed, was an invention of Albumasar, and had never been accepted by more reliable authors like Abraham Ibn Ezra (De mundo et seculo) or Messahalla (Book of eclipses).26 Pigghe’s own method of prognosticating through eclipses was traced back to Hermes (as quoted by an unknown Arabic translator of Ptolemy), Aristotle, and Ptolemy.27 This excluded conjunctionism from the lineage of ancient astrological practice.28 Pigghe’s humanist background is equally apparent in his profound debt to Pico’s Disputations. This shows up in the first and second parts of the Defense, where Pigghe attacked common methods for the making of annual prognostications. However much one would like to credit Pigghe with having devised a single original argument, this simply does not seem to have been the case. Pigghe sharpened his sensitivity for chronological problems while reading Pico’s Disputations.29 Like Pico, he emphasized the dubious theological credentials of the great conjunctions.30 When Pico preferred Ptolemy’s use of four annual starting-points to the common practice of using annual revolutions, based on a single vernal ingress, Pigghe followed.31 Pigghe used Pico’s Disputations as a goldmine of arguments against conjunctionist prognosticators.32 However, this simple conclusion overlooks one crucial point: astrological criticism was not Pigghe’s final goal. Instead, he aimed for a reformed astrological

maxime omnium mathematicas verasque illas disciplinas. Astronomiam praesertim, & Cosmographiam, quibus caelum terraque cognoscuntur, amplectitur summo studio, colit, restituit, illustrat.” 26 Pigghe, Astrologiae defensio, fol. 15v. 27 Ibidem. 28 Pigghe, Astrologiae defensio, fols. 15v-16r: “Quae autem recentiores de reliquorum planetarum, & maxime superiorum coniunctionibus maximis, minimis, & mediocribus fabulantur, & de tam pollentibus eorundem viribus & operationibus, ea, post Ptolomei tempora, conficta esse ab Albumazare, & reliquis fabulatoribus.” 29 Compare for instance Pigghe, Astrologiae defensio, fol. 7r to Disputationes, vol. 1, p. 532; or Pigghe, Astrologiae defensio, fol. 7v to Disputationes, vol. 1, p. 534. 30 Pigghe, Astrologiae defensio, fol. 8r. 31 Tetrabiblos, pp. 195–197; Disputationes, vol. 2, pp. 182–184; Pigghe, fol. 8v. 32 Pigghe frequently states that the power attributed to the signs is inherent to the corresponding constellations and fixed stars, located on the eighth sphere. See e.g. Pigghe, Astrologiae defensio, fol. 12r.

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practice on the basis of Ptolemy’s Tetrabiblos, of which he provided an example through an annual prognostication for 1519 at the end of his treatise.33 Once again, we find a close match between this general project and Pigghe’s contacts at court. In the preface of his Defense, Pigghe emphasized his patron’s contacts with the Italian philosopher Agostino Nifo (c. 1473–c. 1538), under whom Florimonte had studied from 1500 to 1506. Pigghe in turn presented his “example of the Ptolemaic teaching on the judgment of mundane matters” as a tribute to Nifo, “the restorer of a purer astrology.”34 3.3. In defense of reformed annual prognostications Pigghe based his reformed astrological practice on two proposals. The first promoted his adoption of Ptolemy’s astrological physics. Pigghe shared this feature with Nifo’s own treatise on the 1524 conjunctions.35 Both works emphasized Ptolemy’s particular regard for the harmony between astrological physics and natural philosophy (chapter 1). Pigghe only accepted planetary motion and light as celestial causes.36 This implied that the action of the planets was dependent upon their position to the luminaries, from whom they received their light.37 Although Pico had adopted the same attitude, Pigghe differed with him on the issue of planetary virtues. While conceding primacy of action to the luminaries, Pigghe did not accept the claim that other planets had no efficient action in the sublunary realm.38 He claimed that their influence was modified and restricted by the luminaries, but not annihilated.39 Pigghe also acknowledged that different planetary virtues counteracted each other in combina-

33 Unlike Pico, there is no evidence that Pigghe had a Greek text of Tetrabiblos (editio princeps Nuremberg, 1535) at his disposal. He most probably read Tetrabiblos in an Arabo-Latin translation. 34 Pigghe, Astrologiae defensio, fols. 3r/v. For a preliminary analysis of Pigghe’s relation to Nifo, see Talkenberger, Sintflut, pp. 168–172. 35 Nifo, De falsa diluvii prognosticatione, fol. d4r. 36 Pigghe, Astrologiae defensio, fol. 16r: “In philosophia receptum est stellas coelestes in nos agere motu & lumine.” 37 Ibid., fol. 16r. 38 Ibid., fol. 16v: “Neque tamen Pici sententiae subscribimus: ut dicamus praeter Solem & lunam: reliquas stellas nihil in rebus inferioribus virium exercere (…) Sed ut ratio exigit: luminaribus primarias virtutes tribuimus, reliquis autem secundarias & eorundem subministras.” 39 Ibid., fols. 17v.

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tion, comparing this to the use of compound drugs in medicine.40 Pigghe’s emphasis on astrological physics had direct consequences for the conjunctionist astrology he set out to refute. Planetary conjunctions were only relevant to the extent that they (slightly) altered the effects of sun and moon. Pigghe’s second proposal advocated a change in astronomical data. His Defense made the audacious (but erroneous) claim that a fundamental error plagued the astronomical data of the Alfonsine tables. Pigghe’s confusion derived from a realistic interpretation of the famous eighth and ninth spheres of Alfonsine astronomy. Although the models for these spheres were often seen as geometrical calculating devices, Pigghe seems to have thought that they provided a true representation of the “precession of the equinoxes.” In doing so, he followed the example of the Leipzig mathematician Joannes Essler, who combined both models to calculate precession from the resulting unified arrangement. As a result, both Essler and Pigghe proposed a correction to common estimates of Alfonsine precession: Essler found a value of 4;30°, Pigghe of 5;9°.41 These changes to the science of judgments (through Ptolemy) and the science of motions (through the 5;9° correction) constituted his proposal for a “reformed” astrological practice. The most interesting aspect of these strategies concerns their basis in theoretical considerations. Pigghe explicitly engaged with the twin traditions of astrological physics and astronomical theory. At the same time, he carried his conclusions down to the level of astrological practice. This constitutes a “disciplinary” measure in the most literal sense: Pigghe went back to the fundamentals of his art to reform its wayward practice. However, this practice turned out to be inherently limited: Nonetheless we find that there is some kind of infinite variety in these particulars. For when it rains here at a certain time, the sky may be clear in a place hardly two miles further. Such differences cannot be judged from a celestial cause, or from the diversity of horoscopes. Instead, many of these differences arise in diverse places because of the different constitution of the passive matter or object (…) And because

40

Ibid., fol. 18v. Ibid., fol. 10r. See Essler, Speculum astronomiae, fol. a3r; Pigghe, De inventione, fol. 13v. More background is provided in Dobrzycki, “Astronomical Aspects of the Calendar Reform.” 41

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of this, Ptolemy, in his letter to Syrus, stated that the prediction of particular things should be relegated to divine inspiration, and not to the expert.42

Pigghe adopts the classic discourse of epistemic secrecy, developed in Ptolemy’s Tetrabiblos (chapter 1). By implication, he also refused to reduce the state of sublunary bodies to superlunary causes.

4. Gaspar Laet in defense of personal experience (1520) 4.1. Pigghe’s nemesis Gaspar Laet, son of Joannes (chapter 2), was the second of a long line of Flemish astrologers, who remained in business for at least a century. Gaspar matriculated at Louvain in 1479, and took the casting of annual prognostications over from his father around 1487.43 Continuing his father’s patronage relation with prince bishop Jean de Hornes (d. 1505), Gaspar set up a medical and astrological practice in Antwerp. The Antwerp printing presses allowed him to reach a Europe-wide audience with both Latin and vernacular prognostications. Starting in 1493, the annual prognostications of the Laet family were regularly translated into English, and continued to dominate the English market until the middle of the sixteenth century. In the English edition of Gaspar Laet’s prediction for 1520, the King’s printer Richard Pynson (d. 1530) emphasized the popularity of Laet’s previous prognostications and his solid reputation as an astrologer.44 4.2. Laet’s prognostication for 1520 was preceded by an extensive reply to Pigghe’s allegations. Although doxography played an important role, Laet did adopt a radically different historical framework. The humanist Pigghe had evoked the concept of an ancient practice that some astrological writers (Albumasar in a distant past, annual prognosticators in a recent one) had rejected. Laet, on the other 42 Pigghe, Astrologiae defensio, fol. 32r: “Nihilominus, invenimus in his particularioribus veluti infinitatem quandam esse. Eadem namque hora, qua hic pluviat, in loco vix duabus leucis abhinc serenum caelum est. Quae differentia, ex causa caelesti, aut ex horoscoporum diversitate minime perpendi potest, sed proveniunt plurima istorum diversa in locis diversis, ob materiae, aut rei passibilis alteram habitudinem (…) Et ob haec ad Syrum, Particularium rerum praedictionem ad numine afflatos vult esse relegandam, minime vero ad scientem.” 43 See “De Laet (Gaspard)” in: Biographie Nationale, vol. 5, pp. 260–270. 44 Capp, Astrology and the Popular Press, p. 27.

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hand, defends a more homogeneous picture where virtually every author (except for detractors like Pigghe) could find a place. Laet quoted Albumasar, Abraham Ibn Ezra, Messahala, Albertus Magnus, Henricus Bate (1246 – after 1309), and Pierre d’Ailly as “ancient” authorities in support of conjunctionist astrology. His “moderns” referred to contemporary colleagues like Paul of Middelburg, or the prognosticators of the universities of Cracow, Erfurt, and Leipzig. The eclecticism of some of these authors may have encouraged such widely diverging interpretations. Pigghe quoted Ibn Ezra’s De mundo vel seculo to buttress his Ptolemaic emphasis on eclipses and the primacy of Sun and Moon.45 But the very same text could also support Laet’s use of conjunctionist astrology, based on Saturn and Jupiter.46 Above all, however, we find that history was of limited relevance to Laet. Instead, he based his expertise on personal experience: Nor would you [Pigghe] have made so many mistakes [in your prognostication for 1519] if you had taken a look at some other authors that introduce us to astrology, and if you knew that Ptolemy had not predigested everything that is required for astrological predictions. [These things] should not be written down, nor foretold. In as far as he said that the significators Mars and Mercury produce heat and dryness etc., Ptolemy introduced us to a very ingenious method of making judgments on future events. He left the other matters to experience, following the first aphorism of the Centiloquium. This states: “A prognostication stems from yourself as well as from knowledge.” And in the fourth aphorism, he says: “A soul suitable for prognostication, attains more truth than he who has studied the furthest reaches of science.”47 45 See Pigghe, Astrologiae defensio, fol. 15v. The reference is to Ibn Ezra, Liber coniunctionum (1507), fol. u3v: “Et per hoc poterimus scire omnia seculi iudicia quod quidem verum est ideoque 2 luminarium significant super mundum magisquam planete omnes: ipsa nanque prepotentia sunt: et antiqui omnes hoc concedunt.” 46 Ibn Ezra also incorporated extensive digressions on the various effects of SaturnJupiter conjunctions which ultimately derived from Dorotheus of Sidon and Messahala. See e.g. Ibn Ezra, Liber coniunctionum (1507), fols. x1r-x2v. On Dorotheus of Sidon (fl. Egypt[?], 1st century ad), see the article by David Pingree in: Gillispie (ed.), Dictionary of Scientific Biography, vol. 15, p. 125; on Messahalah (fl. Bagdad, 762–c. 815), see David Pingree, “Masha’allah” in: Gillispie (ed.), Dictionary of Scientific Biography, vol. 9, pp. 159–162. 47 Laet, Prenosticatio (1520), fol. a2v: “Nec tam etiam errasses si aliquos alios auctores introductorios in astronomia unquam vidisses et scias Ptholomeum non omnia masticasse quae ad preiudicia astrorum requiruntur nec scribenda sunt aut praeiudicanda prout dicit ipse si mars et mercurius fuerint significatores producere estuositatem siccitatem etcetera. Sed introduxit nos et dedit nobis modum Ptholomeus iudicandi de futuris eventibus multa ingenio. Et experiencia relinquens iuxta verbum primum centiloquij. A te et a sciencia pronosticatio. Et verbo quarto dicit Anima ydonea ad pronosticationem plus adipiscetur veritatis quam qui summe studuit in sciencia.”

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This passage displays a remarkable entwinement of personal and common authority. The first aphorism of Centiloquium was a locus classicus for astrological practitioners seeking to defend their expertise. Here is how the popular commentary on Centiloquium, ascribed to Haly Avenrodoan (988–1061/9), interpreted it: Knowledge of the stars derives from yourself and from those [stars]. But the astrologer should not predict specifically but universally (…) Through matter we achieve uncertain cognition of a thing, but certain [cognition we have] through the form. These judgments that I teach you are in between the necessary and the possible (…), that is, for he who considers the natures of things and the work of the stars. But those men who have foreknowledge through the best part of their souls, are much nearer to the truth because the power of the soul dominates in them, even though they have little knowledge of this art.48

Avenrodoan explained that there were two ways to know the future: one was astrological, the other through divine inspiration.49 While the astrologer’s knowledge was limited to the prediction of universals, greater wisdom awaited the man who combines both faculties.50 On the authority of Centiloquium, then considered to be genuinely Ptolemaic, medieval students of astrology learned to appreciate the value of gnostic elements in their discipline.51 As Laet faced ser-

48 Ptolemaeus, Liber (…) Centiloquium (1484), fols. f6v-f7r: “Scientia stellarum ex te et ex illis est. Astrologus autem non debet dicere rem specialiter sed universaliter (…) Per materiam habemus de re cognitionem dubiam per formam vero certam: et haec iudicia quae trado tibi sunt media inter necessarium et possibile (…) hoc est apud eam qui rerum naturas et stellarum opus considerat. Sed illi qui ex meliori parte animae cognitionem habent futurorum: propinquiores sunt veritati propter animae vim in eis dominantem: licet non multam habeant huius artis scientiam.” My translation is from the Arabo-Latin version made by Plato Tiburtinus or John of Seville in 1136, the most popular version in the mediaeval Latin West. See ΚαρπÞσ, ed. Boer, xxiii. In this version, at least aphorism 1 is substantially different from that in Boer’s Greek text. Since my focus is on the medieval Western reception of this text, I nevertheless prefer to use this. 49 Ptolemaeus, Liber (…) Centiloquium (1484), fol. f7r: “Ex te et illis. Significat quod quid res futuras scire desiderat: duabus vijs omnia incedere: Una ut aspiciat motus stellarum: et opera quae fiunt in rebus secundum earum motum: et libros quos antiqui scripserunt (…) Alia via est quo aliquis per divinam inspirationem habuit istam scientiam: multa vero poterit dare iudicia.” 50 Ibid., fol. f7r. 51 One of the earliest Western examples are the recommendations in Raymond of Marseille’s Liber iudiciorum, written c. 1140–1150. D’Alverny, “Abélard,” p. 625 gives the following passage, translated from Paris, bn, ms. lat. 16208, fol. 16: “Si quelqu’un veut interroger un astrologue au sujet du passé, du présent et de l’avenir, il doit d’abord prier Dieu, auteur de tout bien, et le supplier avec grande dévotion et d’un

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ious controversy, he drew upon this common tradition to defend his individual liberty from it.52

5. The debate at Louvain university: Thomas Montis’ disputation (1521) Over time, the 1524 predictions attracted enough attention at Louvain to warrant a dedicated quodlibetal disputation on 18 December 1521. The disputant for the occasion was a “physician and astrologer” called Thomas Montis (c. 1500 – after 1552?).53 Montis’ astrological

coeur contrit, afin que par sa sainte miséricorde Dieu lui accorde d’accéder à la connaissance de la vérité qu’il cherche.” 52 Laet, Prenosticatio (1520), fol. a2r. 53 Montis, Quodlibetica, fol. a1r: “Quodlibet Magistri Thomae Montis Medici & astrologi de significationibus coniunctionum superiorum planetarum quae erunt anno m.ccccc. & .xxiiii. in Februario. Per eundem ex diversis auctoritatibus collectum ac responsum in alma universitate Lovaniensi in scolis artium.” Very little is known about Montis’ biography. Apart from the Quodlibet, there is a very rare Flemish prognostication for 1526 published under his name at Antwerp (nk 3543), as well as two later ones (for 1546 and 1552), both of which seem to point towards Liège. See P. Bergmans, “Montis (Thomas)” in: Biographie Nationale, vol. 15, p. 196. Our Thomas Montis may be the “Thomas filius Martini du Terne, de Montibus” who matriculated at Louvain on 31 August 1514 as a student of the pedagogy of the Falcon. See Reusens et al. (eds.), Matricule, vol. 3, p. 496, nr. 333. One caveat should be mentioned: it is difficult to assess the precise relation between Montis’ published text and the content of his original disputation. Montis’ quodlibeta was printed by Adrian Berghen at Antwerp on 10 October 1522, almost ten months after the actual disputation took place, giving him sufficient time to expand upon its original content. At the very least, I have been unable to detect any discernable influence of the popular 1524 treatises of Agostino Nifo (1520) or Joannes Virdung of Hasfurt on Montis’ published text. The fact that Montis dedicated his published text to Master Nicolas Coppin, chancellor of the University and professor of Theology, in my view warrants its direct relevance to academic astrological culture. Further editing for the press unfortunately erased any traces of objections that the audience may have had during Montis’ Louvain performance. One should realize, however, that this static character might have been present in the actual disputation, as a consequence of the declining popularity of the quodlibeta from the later fourteenth century onwards. See Lawn, The rise and decline of the scholastic “quaestio disputata”, p. 16 and pp. 126–128. Montis’ quodlibetica seems to contradict Glorieux’s contention that quodlibetal disputations gradually shifted from being a typical master’s to a bachelor’s exercise by the early fourteenth century (Glorieux, La littérature quodlibétique, vol. 1, pp. 13–18). Montis calls himself medicus on the title page of his quodlibeta, which indicates that he had completed his medical studies by October 1522.

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question enquired “whether changes in the sublunary world could be caused by the conjunctions of the higher planets that will occur in the year 1524.”54 Montis’ reply was later printed with a dedicatory letter to the university chancellor Coppin. This dedication shows much more affinity with the traditions of the prognosticator Gaspar Laet than with those of the courtly practitioner Albert Pigghe. Montis did not share Pigghe’s active concern with astrological physics. Instead, he simply dismissed detractors (invectores) who deny the role of the heavens in sublunary corruption, or who deny that the heavens have particular effects in the sublunary realm.55 Montis’ authorities were also remarkably close to Laet’s astrological pantheon. The former’s quodlibetica quotes the mainstays of traditional academic astrology: Messahala, Albumasar, Haly Abenragel and Abraham Ibn Ezra, with additional material from Alcabitius, John of Seville (fl. 1142), Albertus Magnus, Aristotle, and Robert “Perscrutator” of York (fl. 1326).56 Montis’ academic disputation was different from Laet’s urban prognostication in two ways. First, we encounter a condemnation of Pierre d’Ailly’s astrological historiography, which Laet had considered entirely unproblematic. This attitude marks a rupture in a Louvain tradition that had been cultivated throughout the fifteenth century. As late as 1516, the concordance of astrology and theology was still publicly defended at Louvain (see chapter 2). Apparently, the prediction of imminent religious upheaval for 1524 did affect the academic position of Pierre d’Ailly’s conjunctionism. Secondly, different defensive strategies prevailed among scholastic academics. An academic disputation required logically rigorous arguments that were grounded in textual authority, not an appeal to personal experience. It is true that both Montis and Laet quoted successful predictions of the advent of the morbus gallicus, inundations, the rising oppression by the Turks, and ecclesiastical dissent

54 Montis, Quodlibetica, fol. a3r: “Anno itaque m.ccccc.xxi. die .xviij. mensis Decembris hora tercia post meridiem in alma universitate lovaniensi in scolis artium ad tres respondi Quodlibeticas questiones mihi antea per domini Quodlibeticarum propositas, quarum prima fuit cum argumentis. Reliquae vero duae sine argumentis. Dimissis autem duabus questionibus quae medicinales erant. Terciam que astrologica erat reassumo et fuit ista. Utrum per coniunctiones superiorum planetarum que erunt anno M.ccccc. et .xxiiij. futuro poterint causari mutationes in his inferioribus.” On the terminology sine/cum argumentis, see Glorieux La littérature quodlibétique, vol. 1, pp. 24–25. 55 Montis, Quodlibetica, fols. a2r/v. 56 Ibid., fols. a4v-b2r.

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from the Saturn-Jupiter conjunctions of 1484 and 1504.57 But while Laet invited his readers to trust this personal experience, Montis exerted himself to show how these predictions were based on publicly available astrological precepts.58 This strategy was disastrous when it had to compete with astrological predictions. Consider Montis’ opinion on the Mars-Saturn conjunction of 5 February 1524. Using Albumasar’s On Great Conjunctions, Montis predicted much rain, thunder, and lightning from the difference in latitude between both planets.59 In the second part of his argument, Montis turned to Haly Abenragel’s On the Judgments of the Stars, and concluded that: “Mars lessens much of the evil signified by Saturn.”60 It was entirely possible to resolve such internal contradictions within a textual canon, but this did not happen in 1521. Montis never managed to go beyond his vague and unsatisfying conclusion that evil things would befall mankind.61 Why was this the case? The relation between astrological theory and practice in late medieval academic teaching explains a great deal. As demonstrated by the Bolognese curriculum and Joannes Vesalius’ self-presentation, astrological practice was valued more than theory at late medieval universities. This implied that a serious theoretical conflict posed insurmountable problems for university-trained astrologers like Montis. This type of conflict emerged from the juxtaposition of Albumasar and Abenragel. Albumasar’s rules were often rooted in an older analogical discourse that described the conjunction of 5 February 1524 as the meeting of bellicose Mars with moribund Saturn. Abenragel, however, followed Ptolemy’s Aristotelian 57

Laet, Prenosticatio (1520), fol. a1r; Montis, Quodlibetica, fols. a4v-b1r. Montis, Quodlibetica, fols. b2r-b3v. 59 Ibid., fol. b1r: “Mars etiam in septentrione elevatus supra Saturnum et Jovem siquidem talis elevatio fortis sit non minus superfluitatem pluviarum, nec non multitudinem tonitruorum et coruscationum significat.” This refers to Albumasar, De magnis coniunctionibus (1489), fol. n8v: “Cum fuerit mars transiens super eum [=Saturnum] significat illud infortunium in plura climata multos pisces et quod subtiliatur ex avibus cum superfluitate pluviarum et multis tonitruis et coruscationibus.” See the modern edition of Albumasar, On Historical Astrology, ed. Yamamoto/Burnett, vol. 1, p. 421. 60 Montis, Quodlibetica, fol. b2r: “Primo quia Mars in dicta coniunctione secundum aliquem elevationis modum supra Saturnum elevatus multum de malo per Saturnum significato minuet ut patet ex Halij parte octava capite .xxiii.” This refers to Abenragel, De iudiciis astrorum (1551), p. 389: “At si quando [Mars] ingrediatur supra Saturnum, non significat multum mali.” 61 Montis, Quodlibetica, fol. b3r: “Verum tamen est ut inquit Leupoldus tractatu quinto sive compilationis annus ille peior est in quo Saturnus et Jupiter coniunguntur.” 58

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narrative, describing the event as the meeting of a cold and dry planet with a hot and dry one.62 Albumasar’s analogical reading resulted in an accumulation of the malevolent effects of both planets. Abenragel’s physical propositions resulted in the annulment of Mars’ heat by Saturn’s cold. In other words, the conflict could only be resolved by establishing a common ground in astrological physics. This was exactly what academic practitioners like Montis were not trained to do. Not surprisingly, this problem arose in the context of a scholastic disputation, the quintessential exercise in consensus building at late medieval universities. This tension is confirmed at the end of Montis’ quodlibetica, which added that the chart for the vernal ingress of 1524 indicated wars, strifes, great destruction and death among princes and noblemen, and other horrendous changes, “as will appear more extensively in the prognostications for the year 1524.”63 Printed by Adriaan van Berghen, who specialized in popular predictions, Montis’ published text probably intended to further the author’s local reputation as a prognosticator. Apparently, the transition to urban prognosticatory culture enabled Montis to make particular conclusions after all.

6. Prudence, faith, reason, and astrology: Scepper’s Assertion (1523) 6.1. Scepper’s dream The most extensive contribution to the 1524 debates was simultaneously published at Antwerp and Cologne on 16 May 1523. It carried the handsome title An Assertion of Faith against the Astrologers and was written by a young man called Cornelius Duplicius de Scepper. At the time of his publishing debut, Scepper was on the verge of exchanging his student life for a professional career.64 Born at Nieuwpoort on the 62 This is affirmed by Abenragel’s description of the nature and properties of Saturn. See Abenragel, De iudiciis astrorum (1551), p. 9: “Participat cum Marte in infortunio & non in alio, & est ei contrarius et inimicus natura et proprietate, quia refrigerat eum, & propter frigiditatem suae naturae caliditatem & ardorem illius extinguit.” This account is very much indebted to Ptolemy, Tetrabiblos, chapter i.7. 63 Montis, Quodlibetica, fols. b3r/v: “(…) ut latius deo annuente in pronosticis Anni .xxiiij. futuri patebit.” 64 A good introductory biography of Scepper, particularly in relation to Louvain, can be found in De Vocht, History, vol. 2, pp. 166–171; see also J.-J. De Smet, “De

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coast, Scepper received his first education from his uncle, a parish priest near Cassel. Afterwards, he went to study in Paris, where he inserted himself in the circle of Jacques Lefèvre d’Etaples. Scepper took lessons with famous masters like Gerard Roussel (c. 1480–1555) and Josse Clichthove (d. 1543).65 Around 1522 Scepper came to Louvain, matriculating on 3 December, and apparently concentrating on the study of law and the bonae literae.66 In June 1523, only a month after the publication of the Assertion, we find Scepper crossing the channel with the exiled Christian ii of Denmark (1481–1559). The young humanist prodigy had been hired by Christian’s chancellor Godschalck Ericsen (d. 1544), and stayed in the King’s service until 1526. Scepper presented the entire narrative of the Assertion as a dream that came to him after a convivial dinner party in Antwerp.67 While pondering the dedication of an intended treatise on the 1524 predictions to the English royal astronomer and clockmaker Nicolaus Kratzer (c. 1487 – after 1550),68 Scepper had retired to bed, where he immediately surrendered to a deep sleep. In his dream, a beautiful young man appeared before him, inviting Scepper to mount one of two winged horses. These horses carried both men over vast stretches of land, among which Scepper distinguished Utopia, described by Thomas More (1477–1535), the Canary Islands, as well as the recently conquered region of Yucatan. Further beyond these lay the goal of Scepper’s journey: an unknown plain in which an impressive military camp had been erected, consisting of enormous tents and fortified by a ditch and palisade. The vulnerability of its foundations indicated this had been done hastily. A little further he discerned a hill, on one side of which a stronghold had been built, beautiful, great, and with natural defences, but having incurred some damage on its ramparts. The elevated stronghold was the fortress of Faith, built on a slope that was particularly steep, and known as Patience. Several roads led Schepper (Corneille-Duplicius)” in: Biographie Nationale, vol. 5, pp. 709–718; Margolin, “Une lettre inédite.” 65 Scepper, Assertio fidei, fols. 57r and 62r. 66 Scepper’s involvement with legal studies at Louvain is mentioned by Paquot, Mémoires, vol. 2, pp. 634–636: “Ses discours quodlibétiques prouvent qu’il fut quelques termes à Louvain, apparemment pour y étudier en Droit. Quoi qu’il en soit, il parvint depuis à la connaissance de Christiern ii (…) [Parmi ses écrits:] Orationes Quodlibeticae, Lovanii olim habitae. Je ne sais si ces discours ont été imprimées.” 67 Scepper, Assertio fidei (1523), fols. 1r-7r. 68 On Kratzer, see North, “Nicolaus Kratzer – The King’s Astronomer.”

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towards the fortress. The main path seemed plain and straight, but had been sabotaged by a band of heretic innovators, dwelling in the valley, where they preferred recent instead of ancient manners. These men imposed a new religion, new rites, new ceremonies, and new books on approaching pilgrims who sought to follow the established path towards faith. Many were thus deceived into thinking that they were marching up to the fortress, when they were actually diverted from the true path. Scepper and his companion followed the different but less well-known path of Simplicity, which was lined with a great variety of fruit and herbs. The enemies of faith, Scepper noticed, had been ordered in a tripartite division. The first order comprised some beautiful youths who considered themselves important enemies of Faith. The second order consisted of men who preached chastity, piety, religion, and temperance in the name of Christ, but had their mind set on injustice. Many among these were astrologers, wielding a variety of mathematical instruments while contemplating the disposition of the stars. From this, some calculated the horoscope of Christ, showing that Mars in the eighth house had signified his violent death. Others predicted great hardship from a conjunction of Mars and Saturn. Scepper distinguished many men who preferred to take recourse to experience over the teachings of the ancients. Most of these were Phoenicians, Arabs, Saraceans, Egyptians, Chaldeans, and Persians, although the group also comprised Latin authors like Roger Bacon or Pierre d’Ailly. These astrologers disposed of cohorts of lightly armed soldiers handling logical syllogisms and enthymemes, and some luscious harlots who used rhetorical deceits and frills. The third and last group consisted of men who claimed to uphold ancient customs, but nevertheless carried flags showing Scorpio, Cancer, Pisces, or other forces producing floods. Three men came forth from the fortress of Faith to battle this formidable enemy: Scepper identified them as Pico, Nifo and Pigghe. At the entrance of the fortress, a great number of people sought an entrance under the leadership of both Henry viii (1509–1547) and Charles v (1515–1556). Scepper’s familiarity with Philology eventually gained him access to the inner recesses of the fortress, where he encountered a large crowd of servants like Temperance, Fortitude, Humility, Poverty, and Patience. Scepper also met True Philosophy and Rhetoric, both of whom lamented the general contempt that had befallen them. Rhetoric explained that many contemporaries held her to be adverse to religion, and confused her with sophistries, a situation that Scepper found confirmed in his own youthful experience.

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After this, Scepper finally encountered Religion herself, an old woman with great splendor and majesty. She set forth how Astrology had become particularly pernicious in the popular predictions related to 1524, and urged Scepper to stand fast in his faith in divine mercy. Before retreating into a small garden named Prudence, Religion instructed Scepper to set forth these predictions, so that she could assist him in a thorough refutation of the prognosticators. 6.2. Scepper and the Louvain humanists Scepper’s dream shared a number of central attitudes with Pigghe’s Defense (1519). Scepper’s frame story consciously linked the 1524 debates with those between humanists and scholastics. The 1524 predictions were presented as a problem that affected the entire society, and local courts were called upon to take the lead to resolve this problematic. Like Pigghe, Scepper came to this outlook through his specific environment. When the lofty companion finally awoke Scepper from his dream, he was urged to write down his knowledge after the example of Juan Luis Vives, “your friend, the champion of philosophy.”69 This simple reference to Vives (1492–1540) suggests that the Louvain humanist milieu of the early 1520s played a crucial role in the genesis of Scepper’s Assertion. While residing at Louvain (late 1517 – February 1523), Vives made part of his living by giving private lessons in the university hall on humanist topics. On 3 March 1520, the university authorities allowed him to comment on Cicero’s Somnium Scipionis, a course that he had previously given at Paris around May/June 1519.70 These lectures resulted in a Louvain edition of the Somnium by Dirk Martens (c. 1446–1534), followed by the publication of Vives’ own Somnium in April, including an introduction and paraphrase on Cicero’s work (the Vigilia).71 69

Scepper, Assertio fidei, fol. 122v: “Preclara tibi sunt ad id faciendum exempla. Augebit & animum ioannes ludovicus Vives Valentinus, philosophiae vindex amicus tuus.” 70 The Louvain course was expanded in October 1521 to a public course on the letters of Pliny the Younger in the morning, and a private one on Virgil’s Georgics in the afternoon. An introduction and further references to Vives’ years in Louvain is provided by Jan Roegiers, “Leuven en Vives” in: Vives te Leuven, ed. Tournoy et al., pp. 9–21. On Vives and the Somnium Scipionis, see the note by Dirk Sacré, Ibidem, pp. 83–87. 71 The original edition of Vives’ Somnium was badly printed by the Antwerp printer

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A number of similarities between the Somnia of Cicero/Vives and Scepper’s Assertion stand out. Both texts employ the frame story of an allegorical journey under divine guidance in order to discuss a contemporary problem. Although Scepper’s problem was strictly astrological, his dream did share Vives’ criticism of scholastic learning and science.72 One cannot claim with certainty that Scepper attended Vives’ lectures on the Somnium Scipionis, although he was certainly in a position to do so both at Paris and at Louvain. At the very least, Scepper was personally acquainted with Vives, and shared his enthusiasm for Cicero’s text in constructing the literary setting of the Assertion.73 It may have been through Vives that Scepper met other proponents of the humanist movement in the Netherlands like Joannes Fevyn (1490–1555) and Franciscus Craenevelt (1485–1564).74 Fevyn’s letter to Craenevelt of 18/19 July 1523 suggests that this circle introduced Scepper to Godschalck Ericsen, and that the latter had not only been interested in Scepper’s literary or legal talents. Fevyn, clearly very curious about the political situation in Denmark, had questioned Ericsen on the rumor that Copenhagen was under siege. The prudent Ericsen had refrained from elaborate comments, but Fevyn understood that he had consulted Scepper on this matter as a mathematician.75 Fevyn’s interest in celestial omens is confirmed in the next paragraph, where he reports the sighting of two suns on 9 July to Craenevelt.76 In the preface to the Assertion, Scepper stated Jean Thibault. Erasmus incited Vives to re-publish his work in March 1521 on the presses of Joannes Frobenius at Basel. A later 1544 edition describes Vives’ work as “written at Louvain in 1519,” a statement which is presently unverifiable. See Vives, Somnium, ed. George, p. xli. 72 For an introduction to and edition of Vives’ text, see Vives, Somnium, ed. George. It may also be remarked that Scepper, like Vives, frequently refers to his opponents’ delusions as dreams (somnia), e.g. at fol. 49r: “Atque in scientiam introduxerint rem commenticiam, somnioque plane simillimam. Quicquid igitur Saturni Martisque in Piscibus coniunctio predicat apud Astrologos, probavimus non inepto ad Scorpium descensu, quod eo libentius fecimus, quod sciamus te facilius fidem adempturum illorum somnijs.” 73 Vives and Scepper also seem to have shared an interest in geography and astrology. Vives planned to start a course on Pomponius Mela’s Cosmographia at Louvain in October 1521, and had previously taught Hyginus’ Poeticon at Paris. 74 Fevyn was praised in Vives’ edition of Augustine’s De civitate Dei (Basel, 1522), and officiated at Vives’ wedding to Margareta Valdaura at Bruges in 1524. See G. Bietenholz, “Jan van Fevijn” in: Bietenholz/Deutscher, Contemporaries, vol. 2, p. 26; De Vocht, History, vol. 2, p. 522. 75 See Craenevelt, Literae, pp. 163–165 (Ep. 67). 76 Ibidem.

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that prior to their departure to England, Christian ii had consulted his young secretary on the nature of the effects predicted from the 1524 conjunctions: Add to this that I do not write against astrology, but only against those who have upset the entire world by a false prediction. For they have persuaded not only the common people of this thing, but the highest kings and princes as well. In this respect, consider those things that the fairest prince Christian, King of Denmark, Sweden and Norway enquired from me on this matter.77

At least one English observer later referred to Scepper as Christian’s astrologer, which confirms that Scepper was more than just a secretary and legal counselor to Christian ii.78 However, times had changed between 1519 and 1523. Scepper’s Assertion responded to a much more strained context than Pigghe had known. Once again, this left its marks on Scepper’s public practice: I remembered, O mistress [Religion], that while I studied the books of the astrologers with more curiosity than prudence, being carried away I became an entirely different man. The things which were set down in them pleased me so much (seeing that they confirmed their teachings not merely by appearances and verisimilitudes (for I would not dare to call them true) but also through frequent experiences), that they led me to believe that there was some latent power in them which evaded us, little men.79

The visions revealed in Scepper’s dream clearly hint at the relevance and urgency of the contemporary rise of Protestantism:

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Scepper, Assertio fidei, fol. a4r: “Adde neque me in Astrologiam scribere, sed in eos tantum qui falsa praedictione totum in se orbem converterunt. Neque enim solum vulgo eam rem persuaserunt, sed summis etiam regibus & principibus. Occurrunt quae hac de re, me percunctatus est, Serenissimus princeps D. Christiernus, Daniae, Suetiae, Norvegiaeque Rex.” 78 In his report to Charles v on the arrival of Christian ii in England, Charles van Praet, Charles’ ambassador at the English court, calls Scepper “Un jeune homme de Dunkerque, astrologue et à demi devin, lequel commence à avoir grand crédit vers luy.” See Saint-Genois/Yssel de Schepper, Missions diplomatiques, p. 25. 79 Scepper, Assertio fidei, fol. 53v: “Memini ego o domina, dum Astrologorum libros curiosius quam prudentius pertracto, raptum me in novum quendam hominem coaluisse. Adeo placebant quae ibi congesta fuere, dum non apparentibus solum verisimilibusque (nam veras dicere non ausim) sua confirmant, sed & experimentis frequentibus fidem faciunt, inesse latentem quandam & quae nos fugiat homunculos potentiam.” A previous concern with magic, from which Scepper’s Parisian master Josse Clichthove detracted him, is hinted at on fol. 57r.

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In silence these men secretly rejoiced among one another, imposing a new religion on those who arrived, shouting out new rites and ceremonies, and contriving new books which are alien to faith.80

The first public burning of Lutheran books in the Netherlands had been held at Louvain and Liège in late 1520, around the same time that Claes de Grave first printed translations of Lutheran writings in Antwerp. In April 1522, Charles v appointed inquisitor Frans van der Hulst (d. 1530), who crushed the Antwerp Augustinians with exceptional harshness in the spring of 1523. Scepper’s familiarity with the cultural scenes of Antwerp, Liège, and Louvain, made the advent of Protestantism particularly tangible to him. This explains why both Scepper’s Assertion and Vives’ Somnium were dedicated to Cardinal Erard de la Marck, prince bishop of Liège (1472–1538).81 Vives was on familiar terms with the prince bishop around 1522, and it is not unlikely that he introduced Scepper to De la Marck’s household.82 De la Marck had turned his diocese into a heaven for humanists and a hell for heretics.83 It may even have been De la Marck who pointed out the connection between Protestantism and astrology to Scepper. When the Lutheran faction distributed astrological propaganda at the Diet of Worms in the spring of 1521, the prince bishop had been present as one of its main participants.84 6.3. Scepper’s problem The goal of Scepper’s Assertion was to safeguard a space for Christian piety and faith within astrological practice. This entailed two main problems: It is God who allows this thing to happen. When He loathes the vices of mankind, He imposes that flood of waters by a fire emitted from the heavens, or by releasing waterfalls, or by imposing a tempest. Stars, fate,

80 Scepper, Assertio fidei, fol. 2v: “Ipsi inter se taciti gaudere clanculum, advenientibus novam religionem imponere, novos ritus, nova officia ingeminare, novos libros, & a fide alienos comminisci.” 81 A general survey of De la Marck’s literary patronage can be found in Puraye, La renaissance des études au Pays de Liège. 82 See the letter of Vives to Erasmus dd. 20 May 1522 (Erasmus, Opus epistolarum, ed. Allen, vol. 4, p. 1281). 83 On Erard de la Marck’s policy towards protestantism, see Harsin, Le règne d’Erard de la Marck, pp. 265–324. 84 On Seitz’s treatise, see Zambelli, “Fine del mondo,” pp. 336–340. Erard de la Marck’s role in the Diet of Worms is discussed extensively in Kalkoff, Der Wormser Reichstag, pp. 60–90.

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chapter four and necessity do not govern Him, nor does He wait for the conjoined Jupiter, Saturn and Mars to reach the humid degrees of a watery sign, or the puteal degrees of an earthy sign, or the fiery degrees of a fiery one. These are fictions of men who posit that all things that come to pass happen by necessity, and that terrestrial events derive from the certain course of the stars. In the meantime they do not consider how much they detract from divine power, how much they inspire human unease with prayers, fasting, and vigils when they hunt down the prediction of future things from the nature of a birth-chart. If they should hear me, they need to hasten themselves towards adopting better teachings. Neither these times, nor the difficulty of the matter can deter them from this.85

Scepper’s first concern was about God’s supernatural prerogative over religious or political change. His second concern transferred this conflict to the level of practical piety. If it took the prediction of an imminent disaster to lead Christians towards practices of atonement (prayers, fasting, vigils), then this clearly illustrated that man’s judgment had fallen prey to astrology. The means to assert faith were two fold. Scepper’s first strategy applied the various arguments of Pico’s Disputations to the 1524 predictions, in order to dismantle the tradition of academic astrological practice on which these relied. Despite his claim that he owed little or nothing to the Disputations, the legacy of Pico looms large in the Assertion.86 The twelve zodiacal signs,87 the triplicities,88 and the lunar nodes known as “head and tail of the Dragon”,89 all shared the grim fate they had previously met 85 Scepper, Assertio fidei, fol. 71r: “Deus est a quo haec res permittitur, quem cum humanorum viciorum tedet, aut igne celitus emisso, aut resolutis aquarum cataractis, aut aliunde immissa tempestate, ingentem illam aquarum molem immittit. Non regitur stellis fative necessitate, neque exspectat donec Iuppiter Saturnusve aut Mavors coniuncti, in partes humidas signi aquei perveniant, aut puteales terrei aut urentes ignei. Hominum sunt hae fictiones, ponentium omnia quae eveniunt, de necessitate contingere, certoque syderum cursu inferiora deduci. Et non consyderant interea quantum divinae potentiae adimant, quantum precibus, ieiunijs, vigilijs, hominum scrupum inijciant, cum ex geniturae qualitate, futurorum quoque predictionem venantur. Qui si me audiant ad meliores doctrinas capessendas properaturi sunt, a quibus non illos aetas non rei difficultas deterrere potest.” 86 Ibid., fol. a4r: “Neque ego diffiteor hoc argumentum a quibusdam tractatum esse. Scripsit enim in Astrologos Iohannes Picus, sed sic quidem scripsit, ut non omnia contuderit. Equidem huius viri rationes aut nullas assumpsi, aut certe paucissimas, & sic quidem assumpsi, ut illum adversus Lucium Bellantium tuerer, non centonem consarcirem, quod prudens lector facile animadvertet, si non tam titulorum quam argumentorum rationem habeat.” 87 Ibid., fol. 15v. 88 Ibid., fol. 15v. 89 Scepper, Assertio fidei, fol. 39r. Also see Disputationes, vol. 2, pp. 82–89.

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with in the Disputations. Common astrological concepts like luminous and shadowy degree arcs, or puteal, masculine, and feminine degrees were rejected by means of Pico’s arguments.90 Scepper’s second strategy used number-theory and Neoplatonic ontology to discredit any appeal to personal astrological experience. The following sections explore both themes in further detail. 6.4. Scepper’s astrological critique Scepper relied heavily on previously published treatises on the 1524 conjunction, especially those of Agostino Nifo, Thomas “Philologus” of Ravenna, Joannes Virdung of Hassfurt (d. 1538/9), and even Thomas Montis.91 Scepper excerpted every single prediction from these texts, providing as many counter-arguments as possible. As an illustration of Scepper’s various resources, let us consider his fourfold treatment of the Saturn-Mars conjunction on 5 February 1524. His first argument exploited the contradictions among astrological authorities. Referring to Firmicus Maternus, Almansor, Guido Bonatti and Abraham Ibn Ezra, Scepper adduced loci which essentially stated that the combination of two malevolent planets would result in a benevolent effect.92 This shows that Scepper did not imitate Montis’ strategy of vague reconciliation; instead, he opted for outright contradiction of common prognostications. Scepper also expected the 1524 conjunctions to provoke ordinary weather phenomena. This is suggested by his regard for the socalled “lunar mansions,” an alternative division of the zodiac that was 90 See Scepper, Assertio fidei, fol. 38r; fol. 62v; fol. 64v. Also see Disputationes, vol. 2, pp. 130–134. 91 Scepper quotes Nifo’s De falsa diluvii prognosticatione as the source for his discussion of the effects of the two eclipses in 1523: “[margin:] Ratio quarta quae est Niphi/Eclypses duas” (f. 21r). Replies to Ravennatus’ treatise can be found on fols. 50r-52r. Scepper does not mention Montis explicitly, but his discussion of the arguments based on Robert “Perscrutator” of York was most probably inspired by Montis’ use of this rare author (ff. 64v-65r). 92 Scepper, Assertio fidei, fol. 47r. Scepper makes much of a passage in Firmicus Maternus, Mathesis, chapter vi.22 (“Saturnus et Mars si unum partis hospitium acceperint, et in uno loco pariter constituti, aequabili societatis potestate iungantur, si in opportunis geniturae locis, & in iis, in quibus gaudent signis, vel partibus (…) felicitatis insignia, patrimonii augmenta, gloriae commoda, virtutis incorrupta praesidia, felicem filiorum sobolem ex ista societate decernunt, praesertim si diurna fuerit genitura.” See Firmicus Maternus, Astronomicωn Libri (1533), p. 64) and in Almansor, Propositio 7 (“Quando duae coniunguntur infortunae, sit ex eis fortuna perfecta, sicut ex duarum fortunarum coniunctione, & hoc secundum dicta Ptolemaei.” See Almansor, Almansoris propositiones (1533), p. 94).

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mostly used for weather prediction or medical astrology.93 Further confirmation comes from his emphasis on the relevance of astrological faces or decans, introduced by Ptolemy for the specific purpose of making weather predictions.94 On this basis, Scepper pointed out that the Saturn-Mars conjunction would occur in a dry, rather than a humid lunar mansion.95 The third argument against the predicted effects from the Saturn-Mars conjunction of 5 February 1524 was based on experience. Both in 1513 and 1520, Scepper recalled, there had been similar conjunctions with much clearer significations of floods, thunder, and lighting.96 Experience had shown that these effects did not come about, thereby invalidating the theory by which they were predicted. The fourth and last argument made the common epistemological point that singular and fallible experiences could not possibly be the base for universal propositions, which were necessary for any true science.97 6.5. Scepper’s philosophical arithmetic While Pigghe turned to natural philosophy and mathematics to reform the basis of astrological practice, Scepper appealed to different philosophical traditions to reform the strained relation between astrology and theology. Scepper claimed that it was his ultimate intention to attain a union of astrology and philosophy, “so that, as in a painting, it would be possible to consider all things.”98 This philosophy was not the scholastic brand, characterized by love of

93 Scepper, Assertio fidei, fol. 53r: “Demum nec Lunares mansiones his curae fuere, quae tamen quantum momenti habeant, pridem deduximus.” Scepper refers to an earlier passage where he uses lunar mansions on the authority of Gaphar and Regiomontanus’ Ephemerides. See Scepper, Assertio fidei, fol. 31r. 94 Scepper, Assertio fidei, fol. 53r: “Deinde haec promulgarunt, quasi nullum faciei discrimen esset. Quae tamen tanti momenti apud veteres fuit, ut in quaestionibus, illius magis rationem habuerint, quam oekodespotis, quod ab albenait, & iergi, & zaele, & albubatele & bonato, & dorotheo, in Astrologicis iudicijs praeditum est.” Scepper’s list contains a who’s who in medieval astrological weather prediction. Compare with the appendix to Jenks, “Astrometeorology,” pp. 209–210. 95 Scepper, Assertio fidei, fol. 47r. 96 Ibid., fol. 48r. 97 Ibid., fol. 49r. 98 Ibid., fol. a4r: “Illud certe operaeprecium fecerit lector, quod in omnibus his quae enumerabimus, sic Philosophiam Astrologiae, sic Astrologiam Philosophiae coniunximus, ut velut in tabula, omnia queat inspicere.”

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“reasonings, syllogisms, and enthymemes.”99 What Scepper did have in mind, is hinted at in the following passage: In the process, we have brought out some mysteries from the divine teaching of the Pythagoreans. Immediately afterwards, we spurred fine minds not to disdain the study of philosophy completely. While this is useful to all men, it is all the more necessary to those who aim at eloquence. But we refer only to genuine eloquence, for that other one, which men call sophistry, we always advised to avoid as if it were a serpent.100

Scepper detailed his rediscovered arcana in chapter iii.2, which analyzes “from the monuments of the ancient Platonist philosophers, by which means astrologers predict true things.”101 Taking his cue from the first aphorism in pseudo-Ptolemy’s Centiloquium, Scepper develops Cicero’s distinction between natural (a natura) and artificial prediction (ab arte) through Ficino’s translations of late antique Neoplatonist texts.102 There was no doubt in Scepper’s mind that natural predictions, defined as sensations of the mind through divine (Iamblichus) or demonic (Porphyry) inspiration, were perfectly possible.103 But the status of artificial (i.e., astrological) prediction was more problematic. Scepper admits that the certainty of these predictions is dependent on the astrologer’s ability to grasp all relevant causes. Since this was impossible, astrological predictions were often incorrect.104 That predictions ab arte nevertheless continued to lure men, was a result of their demonic origins. Whereas soothsaying about past things was relatively easy for demons, this was not at all the case when it came to predicting future things: For since those things which occurred in the past, could easily be known through those demons, whom it pleases to involve themselves with hu99

Ibid., fol. a4r. Ibid., fol. 4r: “Eruimus interdum archana quaedam e divina Pythagoreorum traditione, subinde adhortantes, ne penitus bona ingenia philosophiae studium aspernarentur, quod ut omnibus hominibus utile est, ita his presertim qui eloquentiam affectant necessarium. De syncera loquimur tantum. Namque alteram quam sophisticen vocant, ut viperam semper monuimus fugiendam.” 101 Ibid., fol. 54r: “Quibus modis Astrologi interdum vera praedicunt ex Platonicorum veterumque philosophorum monumentis.” 102 Scepper quotes Iamblichus, Porphyry, Proclus, and Michael Psellus, all of which are contained in the Aldus Manutius-editions of Ficino’s philosophical work and translations. I have not been able to find the specific source of Scepper’s analysis of the problems of divination, but a similar Pythagorean approach is at least contained in Iamblichus, De mysteriis iii.5. 103 Scepper, Assertio fidei, fol. 54v. 104 Ibid., fol. 55r. 100

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chapter four mans (and whom the ancients called either lares or genii or Penates), it easily happens that they render us more certain about past things through their clever attentiveness (…) It is unnecessary that one should hear this from outside: since these demons are most light and imperceptible, they stir the senses imperceptibly, so that one who predicts does not suspect that it had been instigated or said to him by someone else. This happens often, not only in this art, but in all those that set out to predict such things. For when those spirits notice that mortals can easily be deluded (since you are most eager to learn of all future things), they take up every occasion to withdraw you from the true worship of God towards certain inanities. With soft whispering they inspire things that have happened. But since they are not certain about all things, they often deceive us. The same does not apply, however, for things that are yet to happen. Since they cannot obtain knowledge of future matters but through external signs, it follows that they deceive very often.105

This analysis discredited prognosticator’s appeals to personal experience, which had now become tainted with the suspicion of demonic intervention. Scepper’s awareness of this factor, on the other hand, enabled him to avoid this pitfall. Scepper concluded that astrological predictions must be checked by revealed truth, since even demonic knowledge of the future is ultimately dependent on God. He proved this through a fine example of philosophical number theory: Thus you will easily grasp the double [nature of] truth, one being simple and derived immediately from God; Plato and Pythagoras also mentioned this when they said that truth comes forth from unity. The other is taken in consequence, almost from the former’s shadow. This can be compared to the second unity, which is ten, as philosophical understanding sufficiently shows. For this last number is ultimate among the Pythagoreans, and a sign of completion, although it does not depend directly upon that first unity, but is instead packed with intermediate

105 Ibid., fol. 56r: “Nam cum ea quae prius gesta sunt, ab his daemonibus facile noscantur, quibus ea res cordi est, quique hominibus sese inserunt, sive illi a veteribus lares, sive genij, aut Penates dicti sunt, ex illorum solerti diligentia facile fit, ut eorum quae praeterlapsa sunt, certiores fiant (…) Nec opus est hac in re externo auditu, ipsi enim cum sint levissimae & insensibiles, insensibiliter organum movent, ut nec is qui predicit, putet id ab alio sibi instigatum dictumque fuisse. Quod non in ea solum arte usuvenit, sed in his omnibus, quae harum rerum predicendarum curam sibi assumunt. Videntes enim spiritus illi, facili modo ludificari posse mortales, ut estis omnium futurorum cupidissimi, nullam ansam magis pertrectant, quam ut vos a vaero dei cultu, ad inania quaedam revocent, tenuique susurro quae preterita sunt, insinuent. Ut autem non certi sunt rerum omnium, ita in multis decipiunt. In his vero quae futura sunt, non eadem ratio. Nam cum futurorum cognitionem habere non possint, nisi per exteriora signa, fit ut frequentissime mentiant.”

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numbers of both kinds, both odd and even. And since it is allowed to philosophize about demons through even numbers, and about good spirits through odd ones, so it is most convenient to [reflect] upon the secondary truth by means of ten. (…) Thus the secondary truth depends upon that first one, but in such a way that the assessment of the former is of no [value] to the latter. For which reason the Pythagorean authors, as well as some poets sharing their opinion, have bound divinity to nine. Since that first divine being is followed, with respect to their nature, by spirits that have been expelled for their insolence, we will philosophize remarkably well by whishing to elicit some truth from them, although not that [truth] which they have of themselves, but [that which they obtain] through the indulgence of the first unity. This manner of philosophizing in no respect departs from the sacred writings, in which it is stated that those malevolent [beings] can only effect something in as far as God permits them to. Now you see to which philosophical reasoning all these things can be adapted. We willingly engaged in them because those men falsely boast that divinatory astrology is a part of philosophy.106

The influence of Pythagorean mystical number-theory on Scepper’s philosophy is clear in his attention to the importance of the numbers 1 and 10, to the link between odd and even numbers on the one hand, and good and evil natures on the other, and to the association of 9 with completeness. Scepper expanded this tradition by connecting its speculations with Neoplatonic ontology. In his hands, Pythagorean numbertheory says something about the relation between God and the lower

106 Ibid., fol. 57v: “Duplex igitur vaerum facile colligis, alterum quidem simplex, & a deo immediate profectum, cuius etiam meminere plato, et pythagoras, cum ab unitate vaerum promanare dixerunt. Alterum ex consequenti & quasi ex alterius umbra desumptum, quod secundae unitati nempe denario comparari posse philosophica perspectione satis constat. Velut enim is numerus apud Pythagoreos ultimus est, & consummationis signum, nec tamen immediate a prima illa unitate dependens, sed intermedijs utriusque generis numeris, & paribus & imparibus stipatus. Et cum per pares quidem non omnino male de daemonibus, per impares de dijs bonis philosophari liceat, ita de secundaria vaeritate per denarium convenientissime (…). Dependet igitur secunda veritas a prima illa, sed sic quidem ut nulla sit illius ad hanc estimatio. Quin & divinitatem novenario terminati authores sunt Pythagorici, & aliquot etiam poetae ex illorum opinione & sententia. Cumque post divina illa entia prima, sint in suae naturae respectu spiritus, illi qui ob superbiam deiecti sunt, egregie philosophabimur, si ex his aliquid vaeritatis elicere velimus, non quod e se habeant, sed primae illius unitatis indulgentia. Quae etiam philosophandi ratio, non usquequaquam abhorret a divinis literis, in quibus proditum est nihil posse malignos illos, nisi quatenus id illis a deo permissum est. Vides quam ad philosophicam rationem haec omnia accommodari possunt, quod eo libentius obivimus, quo falso illi gloriantur, Astrologiam divinatricem philosophiae partem esse.”

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demons. The result reminds one of Boethian number-theory, which showed that the only real truth resides in the One, and is granted by the One.107 Philosophical arithmetic thus proved the absolute primacy of revealed truth. But it could also be applied to the evaluation of astrological knowledge. This occurred in chapter iii.6, where Scepper attributed the tradition to Christiani philosophi, contrasting them with the people who follow the philosophandi ratio pythagoricorum. From the principles that two or six are more perfect with respect to unity than seven, Scepper proved that the signs of Taurus (the second) or Virgo (the sixth) were more perfect and powerful than Cancer (contrary to common astrological teaching), and that the association of sterility with Virgo could not be founded on any sound philosophical grounds.108 Where did Scepper learn to value the tradition of philosophical arithmetic? His sources include Dionysius Areopagiticus (fl. c. 500), Joannes Damascenus, Gregory of Nazianze (c. 330–c. 389) and Boethius, but also Jacques Lefèvre d’Etaples (d. 1537), Josse Clichthove, and Gerard Roussel. Apparently, both Josse Clichthove and Gerard Roussel were Scepper’s instructors while he studied at Paris, and he explicitly refers to the latter as his “teacher in Philosophy.”109 As late as 1538–1539, Scepper looked back upon this formative period with Charles de Bovelles (b. c. 1520), another member of Lefèvre’s circle.110 Michael Masi has shown how Roussel’s commentary on Boethius’ De arithmetica (1521) used philosophical arithmetic to induce certainty about theological matters.111 Roussel employed number-theory 107 Compare to the remarks on Boethian philosophical arithmetic in Masi, “The Liberal Arts,” p. 36: “The De Arithmetica states repeatedly that mathematical rules are established by a certain divine order, an order determined by the nature of the divine intellect itself: ‘God, the founder of this perishable world, had his reasoning as its primary exemplar and in accord with this he created all things.’” On Boethian arithmetic, see the references in L. Minio-Paluello, “Boethius” in: Gillispie (ed.), Dictionary of Scientific Biography, vol. 2, pp. 228–236. To be supplemented with the articles in Boethius and the liberal arts, ed. Masi; Boethius, ed. Gibson; Batschelet-Massini, “Zur kosmologischen Arithmetik des Boethius”; Boethius, Institution arithmétique, ed. Guillaumin. 108 Scepper, Assertio fidei, fols. 61v-62r. 109 See Scepper, Assertio fidei, fol. 57r on his relationship with Clichthove; Idem, fol. 61v for the reference to Roussel or Gerardus Ruffus. 110 See the letter to Bovelles in Margolin, “Une letter inédite,” pp. 113–117. 111 Masi, “Liberal arts,” p. 27. On Roussel, see Schmidt, Gérard Roussel (1845). The use of numerology in theology (and bible-exegesis) was also central to the work of Roussel’s teacher Jacques Lefèvre d’Etaples, as appears from the cabbalistic inter-

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against Arianism, which rejected Catholic doctrine on the unity of God. Elaborating on the theme of the relationship between unity and multiplicity, Roussel claimed that both “one” and the divine nature were above all division. At the same time, “three” emanates from this unique perfection, which is dispersed over different objects.112 Scepper’s nocturnal journey had led him to the fortress of Faith, besieged by Lutherans, Turks, impious Christians, and judicial astrologers. Scepper’s Assertion withstood these assailants with two weapons. The first was a combination of Neoplatonic ontology and philosophical number-theory; the second was Pico’s rational evaluation of astrology. Neoplatonic ontology discredited appeals to direct divine inspiration: the incompatibility of the 1524 predictions with divine rule indicated that astrologers were the unwitting spokesmen of demons. Philosophical arithmetic in turn “demonstrated” the superiority of divine over demonic knowledge and action. Finally, Scepper used Pico’s astrological critique to discredit justifications of the 1524 predictions from within the astrological tradition. All this embodied the fundamental lesson that a correct application of reason could not contradict revealed truth.113

ests of his De magia naturali (1492–1494). Through a comparison with Symphorien Champier’s later work, Brian Copenhaver has shown that occult and magical speculations had become much more problematic in early 16th-century France. This may have reinforced the ancillary role of numerology to theology in the work of Gerard Roussel. See Copenhaver, “Lefèvre d’Etaples, Symphorien Champier and the secret names of God.” The Neoplatonic interests of Lefèvre have been touched upon in Joukovsky, “Thèmes Plotiniens à la Renaissance.” 112 See Masi, “Liberal Arts,” pp. 36–41. 113 Compare to the attitude of Roussel as expressed by Masi, “Liberal Arts,” p. 26: “His mathematical commentary shows a strong desire to cling to traditional forms of thought, with a hope of lifting them to lofty spiritual levels and deepening their extensions into a profound personal commitment.”

CHAPTER FIVE

ASTROLOGY AND THE LOUVAIN COSMOGRAPHICAL TRADITION

1. Introduction: cosmography and the 1524 debates Louvain mathematicians shared an anecdote. It recounted how Margaret of Austria, regent of the Low Countries (1507–1530) for her nephew Charles v, had consulted an astrologer around the time of the 1524 debates.1 This man, known as Franciscus Monachus, provided her with successful predictions of the captivity of François i at Pavia (1525) and of the death of René de Châlon (1544): Since Mars was in the fourth and lowest house in the geniture of François, and the tail of the dragon in the mid-heaven, Franciscus Monachus of a Franciscan convent near Mechlin not only predicted his captivity to Margaret of Austria, the aunt of your father, but even the year, month, day, and hour of that event. The same Franciscus predicted that the 26th year would be fatal for René de Châlon, prince of Orange. This in fact happened on St.-Desiderius’ day in the year 1544.2

Little firm evidence exists about the elusive Franciscus Monachus (c. 1490–1565). He was a Franciscan from Mechlin who studied at Louvain, and designed the oldest known globe from the Low Countries.3 No extant copy of this terrestrial globe has been discovered, but some idea of its origins and content can be derived from the

1 So far, I have encountered this story in Joannes Stadius’ Ephemerides (first edition in 1556). Sixtus ab Hemminga, another Louvain student of astrology, also mentioned Franciscus Monachus as an important proponent of astrology. See Sixtus ab Hemminga, Astrologiae refutatae liber, p. 142. 2 Stadius, Ephemerides (1556), fol. a4r: “Tamen quia Mars in Francisci genesi esset in quarto, in loco abiecto, quod cauda Draconis in M.C. non captivitatem tantum, sed & annum, mensem, diem, horam. D. Margarete Sabaudae, D. Patris tui amitae, Franciscus Franciscanae familiae apud Mechliniensis Monachus praedixit (…) Predixerat idem Franciscus Renato Chalonio Orengie Principi annum 26. fatalem futurum, quod nimis vere ad Fanum Desiderii anno 1544. accidit.” 3 The best general survey of the life and work of Franciscus Monachus is in Karrow, Mapmakers, pp. 407–409.

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accompanying manual, which was printed at Antwerp in c. 1526– 1527.4 This document teaches us that Monachus’ globe catered for two different audiences. On the one hand, it was commercialized by an Antwerp printer called Roeland Bollaert. On the other hand, it received patronage from Jean Carondelet (1469–1545), member of the Privy Council at Mechlin since 1508 and special advisor to Margaret of Austria. Not unlike Pigghe at the court of François i, Franciscus Monachus’ skills in both cosmography and astrology were much appreciated at the Mechlin court around the middle of the 1520s. The role of court astrologer was a fairly traditional one in the Low Countries (chapter 2). But employment as a cosmographer was an entirely novel pursuit, invested with the brilliance of new discoveries. Both the courtly patronage networks at Mechlin and the urban commercial markets at Antwerp were prepared to invest in the attractive, tangible knowledge displayed on a terrestrial globe. Chapters 2 and 4 showed how traditional academic physicianastrologers (e.g., the Laet family) successfully transposed their services into urban commercial markets. Print technology also enabled them to transcend their local settings. The strong impact of Laet prognostications created an opportunity for competitors with a humanist background to target courtly patrons, using claims that disputed the legitimacy of traditional academic astrology. However, most environments did not support astrology as a completely selfsufficient profession. Urban prognosticators, for instance, generally combined it with a medical career. Hence, it is no surprise that even courtly critics combined their astrological activity with diplomatic, administrative, or even “philosophical” services. The relevance of Franciscus Monachus’ courtly career lies in the fact that he successfully combined astrological practice with new mathematical occupations like commercial cosmography.5 This chap4 Franciscus Monachus, De Orbis Situ (c. 1526–1527). The manual was printed by Martinus de Keyser at the expense of Roeland Bollaert. The dating which is used here, follows the arguments set forth in Van der Krogt, Globi Neerlandici, pp. 41–42. 5 To my knowledge, no single commonly accepted scholarly definition of cosmography exists. One may reasonably claim that the conceptual foundation of this discipline was Ptolemy’s Geography, which was translated as Cosmographia in the early fifteenth century by Jacopo d’Angelo. In his preface, d’Angelo was quite clear about his motives for doing so: since Ptolemy specifically wrote a treatise on describing the world (on a map) by means of astronomical data, preference had to be given to a name referring to both earth and heavens. Cosmography soon became the standard name for treatises and maps made in the tradition of Ptolemaic cartography. Although from 1482 onwards the title Geographia was adopted for Latin editions

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ter relates how other students followed this example, and how they cultivated cosmography as a new token of their astrological expertise. Cosmography was allied with the practice of astrological reform; astrological reform was allied with the practice of cosmography.

2. The rise of Louvain cosmography: Gemma Frisius On 26 February 1526, a frail and somewhat delicate seventeenyear old student from Friesland presented himself for official matriculation at Louvain University.6 The young man used his Frisian patronym Jemme Reinierszoon, which the University registrar latinized to Gemma Reyneri. Gemma was born at Dokkum on 8 December 1508. After the premature death of his parents in war-torn Frisia, the young boy was taken under the care of some relatives and sent off to Groningen for his schooling. His talent for study in the humanities earned him a place at Groningen College in Louvain, where he was assured of board and lodging while beginning his academic study at the arts faculty.7 Gemma enrolled as a poor student (pauper ) of the Lily, one of the four pedagogies (the others being the Castle, Falcon, and Porc) around which all arts teaching had been organized since c. the 1440s. At the Lily, Gemma entered a community of eighty-seven

of Ptolemy, cosmography remained a common denominator for sixteenth-century maps, globes, or texts describing the world by means of astronomical data, or for treatises expounding how to do so. This is the sense in which I use this term. One may further distinguish between terrestrial and celestial cosmography, depending on whether the terrestrial surface or the celestial sky is described, although this distinction was not customary in contemporary treatises. Geography is distinguished from cosmography by its focus on a qualitative, rather than mathematical description of the terrestrial surface. See De Smet, “Les géographes de la Renaissance et la cosmographie.” 6 The best bio-bibliographical introductions to Gemma Frisius are Karrow, Mapmakers, pp. 205–215; Antoine De Smet, “Gemma, Frisius” in: Nationaal Biografisch Woordenboek, vol. 6, pp. 315–331. To be supplemented with Van Ortroy, Bio-bibliographie. The most recent extensive biography of Gemma Frisius, with direct references to the primary sources, is De Vocht, History, vol. 2, pp. 542–565. The sources of all subsequent information on Gemma Frisius can be found in Van Ortroy and De Vocht, unless where stated otherwise. 7 Apart from the reference in Suffridus Petri’s biography of Gemma Frisius, which is generally reliable, I have not found any further trace of the existence of this college. Van Ortroy, following modern studies of the old Louvain colleges, concludes that Petri’s collegium Gruningiae was an association of students from the Northern provinces (Van Ortroy, Bio-bibliographie, pp. 17–18).

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professors, masters, cooks, craftsmen, and students of widely varying level and background.8 This community was spread out over several buildings, all situated in the area around the Nieuwstraat and the West of the Dorpstraat, several of which were connected by a small garden.9 Despite their lack of luxury, these houses at least offered the comfort of a quiet and convivial atmosphere, where Erasmus (1469–1536) greatly enjoyed his stay in the period 1517–1521.10 Erasmus’ preference for the Lily had as much to do with its intellectual profile as with the relative comfort of its surroundings. The first long-standing regent of the Lily was Carolus Viruli (1438– 1493), author of a popular letterbook (the Epistolarum formulae) for use in the arts faculty, which constituted one of the most important contributions to the advancement of Latin prior to the coming of humanism to the Low Countries.11 Among Viruli’s successors in the first half of the sixteenth century were Erasmus’ intimate friend Joannes de Neve (1515–1522), the physician Joannes Heems of Armentières (1522–1560) and Peter Curtius (1522–1531). The latter, a member of the Louvain humanist circle of Erasmus, Juan Luis Vives, Marcus Laurinus (1488–c. 1540), Joannes Fevyn, and Franciscus Craenevelt, temporarily became the sole regent of the Lily in the last year of Gemma’s studies there.12 In the wake of De Neve’s habit of attracting humanist pedagogues like Joannes Despauterius (1460–1520) and Martinus Dorpius (1485–1525),13 Gemma also enjoyed the presence of teachers like Petrus Curtius (for Latin and eloquence) or Michael Driutius (1519–1594, for philosophy) in the formative years that he spent at the Lily.14 Given this environment, it seems very likely that he took courses at the Collegium Trilingue (1517), the center of humanist studies at Louvain, which was then frequented and managed by most of the aforementioned names. His teachers there would have been Conrad Goclenius (d. 1539, for Latin) and Rutger Rescius (d. 1545,

8

Bosmans, De Lelie, p. 144. Ibid., p. 150. The Nieuwstraat is currently the Vanderkelenstraat; the Dorpstraat is now better known as Diestsestraat. 10 On Erasmus’ attachment to the Lily, see De Vocht, History, vol. 2, pp. 80–88. 11 The context of Viruli’s work is discussed by IJsewijn, “The Coming of Humanism,” pp. 224–225. 12 See the biography of Curtius in: Craenevelt, Literae, pp. 205–209. 13 See Bosmans, Lelie, pp. 67–70. 14 On Peter Curtius, see De Vocht, History, vol. 3, pp. 132–136 and vol. 3, pp. 574– 575; on Michael Driutius, see De Vocht, History, vol. 2, pp. 421–422. 9

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for Greek).15 At the time of Gemma’s ma study, Joannes Campensis (1491–1538), the Trilingue’s Hebrew teacher, was composing a book of grammar that greatly facilitated the study of this third language at Louvain.16 When Gemma obtained his ma on 19 March 1528, he had received a good humanist grounding in Latin, and had probably picked up some Greek from Rescius. Within one or two years, he also made his publishing debut with a re-edition of Peter Apian’s Cosmographia (February 1529 [1530 n.s.?]), probably at the request of the Antwerp printer Roeland Bollaert.17 This shows that Gemma acquired considerable skills in mathematics during, or at the very least immediately after his ma-studies at the Lily.18 Gemma Frisius was the first Louvain alumnus who shaped his mathematical career around the discipline of cosmography, rather than astrology. His cosmographical practice was predominantly didactic, and focused on three domains: classroom teaching, authorship of didactic texts, and authorship of didactic instruments. A close study of these activities will show that Gemma Frisius and his pupils integrated certain astrological topics and techniques within cosmographic didacticism. This simultaneously clarified the common astro15 Goclenius was the successor of Adrian Barlandus on the Trilingue chair of Latin, and taught there from 1519 to 1539. On Goclenius’ Latin courses at the Trilingue, see De Vocht, History, vol. 2, pp. 109–115; On Rutger Rescius, see: Craenevelt, Literae, pp. 413–415. The various difficulties in maintaining the Greek course at the Trilingue around the time of Gemma’s study are discussed in De Vocht, History, vol. 2, pp. 316– 338. 16 See De Vocht, History, vol. 2, pp. 118–122. 17 On the publishing history of this edition of the Cosmographia, see Van der Krogt, Globi Neerlandici, pp. 46–48. 18 It has been suggested that his teacher of mathematics was Joannes Driedo (d. 1535), one of the first Louvain theologians to become a habitué of the new Trilingue. On Driedo and the Trilingue, see De Vocht, History, vol. 2, pp. 505–508. The suggestion that Driedo taught Gemma Frisius mathematics was first advanced by De Vocht, History, vol. 2, pp. 543. De Vocht’s attribution of a serious interest in mathematics to Driedo was based on an autobiographical passage in the preface to his De captivitate et redemptione generis humani, where Driedo recalls his special interest in astronomy in the first decade of the sixteenth century, while teaching at the pedagogy of the Falcon. This passage was first emphasized in the bio-bibliographical oration of Van den Broeck, “Oratio,” pp. 250–252. Driedo’s statements seem to refer to the standard medieval course on advanced mathematical astronomy, the theorica planetarum. According to Driedo, it was Adrian of Utrecht, the later pope Adrian vi, who urged him towards the study of theology, in which he was promoted Doctor in 1512. Driedo’s active pursuit of mathematics may be confirmed by the interests of his pupil Albert Pigghe (see chapter 4), but textual evidence connecting Driedo with Gemma Frisius is still absent.

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nomical component of cosmography and astrology, and identified the main problems that both disciplines needed to solve. Public interest in cosmography became the vehicle for an increased awareness of the problems of astrology. At the same time, it provided cosmographers with an occasion to present themselves as astrological experts. This novel alliance between astrology and cosmography emphasized two elements that were largely absent from Franciscus Monachus’ work. First, it increased the role of Louvain university as a cosmographical center.19 Apart from Gaspar van der Heyden’s role in engraving and constructing the Monachus globe, no clear function was laid out for Louvain in the earlier stage of cosmography in the Low Countries. Secondly, it integrated astronomy in these pursuits. Franciscus Monachus’ active interest in astronomy seems to have been limited. When Bollaert and Carondelet desired a celestial counterpart to the terrestrial globe, they simply copied the existing products of Joannes Schöner.20

3. New opportunities for cosmographical patronage Among the central figures of the patronage networks that supported Louvain cosmography was a veteran of the 1524-debates: Cornelius Scepper. After the publication of Scepper’s Assertio (1523), Christian ii entrusted his secretary-astrologer Scepper with diplomatic missions. He was promoted as the King’s vice-chancellor in October 1524, and soon embarked on a mission to the imperial court in Madrid.21 Among the men that Scepper met there was Joannes Dantiscus (1485–1548), ambassador to the Polish throne and patron of a reclusive astronomer called Nicolaus Copernicus (1473–1543).22 Like their contemporary colleagues in Holbein’s The Ambassadors

19 Although Monachus’ patron Carondelet had been supportive of the Louvain humanist movement. See J.C. Olin, “Jean (ii) de Carondelet” in: Bietenholz/Deutscher (eds.), Contemporaries, vol. 1, pp. 272–273. See also De Vocht, History, vol. 2, pp. 285– 286 on Carondelet’s support of Erasmus. 20 It is unclear whether this was because they regarded innovations as unnecessary in the representation of astronomical knowledge, because they felt that such innovations were absent from the field, or because Franciscus Monachus could not supply them with the necessary skills or knowledge. 21 On Scepper’s mission to England and his appointment as vice-chancellor, see Brewer et al., Letters and papers, vol. iv, p. 777. 22 On Dantiscus, see Joannes Dantiscus, eds. IJsewijn and Bracke.

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(1533), Scepper and Dantiscus found a common interest in mathematics, which they satisfied during joint moon-observations at Burgos.23 Scepper left Spain in June 1525,24 and remained at the expatriate Danish court until the death of Queen Isabella in January 1526.25 He then entered the service of Charles v, who sent him to Spain26 and Poland. At the end of these exhausting missions, Scepper finally returned to the Low Countries at the end of 1528, where he resumed contact with the Collegium Trilingue circle through his old teacher Conrad Goclenius.27 Dantiscus mostly stayed in Spain until August 1529, when he followed the Emperor to Italy and Germany.28 Although their correspondence had remained intense, it was a great joy for him to meet Scepper again at the Augsburg Diet around July 1530.29 From Augsburg, they separately made their way to the Low Countries, where Dantiscus reached Brussels in late January 1531.30 He immediately ordered a sphera (either a globe or an armillary sphere), which the Louvain printer Bartholomeus de Grave had almost ready on 3 February.31 Dantiscus’ intermediary for this order was the Trilingue professor Conrad Goclenius, whom he undoubtedly knew through Scepper.32 Goclenius had a strong personal interest in geography and astronomy.33 Several other members of his circle also owned terrestrial 23

de 420: Dantiscus, Correspondence, ed. De Vocht, p. 334. de 18: Dantiscus, Correspondence, ed. De Vocht, p. 17. 25 See De Vocht, History, vol. 3, pp. 167. 26 See Erasmus, Opus epistolarum, ed. Allen, vol. 7, p. 1994a:60–63. In the course of this stay, Scepper established a strong friendship with the Emperor’s chancellor Gattinara (see Erasmus, Opus epistolarum, ed. Allen, vol. 8, p. 2336:7–34) and pursued his correspondence with Dantiscus. See Dantiscus, Correspondence, ed. De Vocht, pp. 27–33. 27 See Erasmus, Opus epistolarum, ed. Allen, vol. 7, p. 2063:61. 28 See Dantiscus, Correspondence, ed. De Vocht, pp. 47–62. 29 Scepper wrote to Erasmus from Augsburg on 28 June 1530. Dantiscus, who remained behind in Italy due to illness, rejoined the Court between 30 May and 29 July. See Dantiscus, Españoles y polacos, ed. Fontan/Axer, letters ii.53 (p. 220), iiib.9 (p. 324) and i.5 (pp. 76–77); Dantiscus, Correspondence, ed. De Vocht, p. 53. 30 There remains some confusion concerning Dantiscus’ date of arrival at Brussels, due to the misdating of de 101 in De Vocht, History, vol. 2, p. 437 note 6, which was corrected in Dantiscus, Correspondence, ed. De Vocht, p. 123. The terminus a quo is established through de, 107: see Dantiscus, Correspondence, ed. De Vocht, p. 64 note 3. 31 de 107: Dantiscus, Correspondence, ed. De Vocht, p. 64. 32 In his letter, De Grave says that Goclenius will deliver the sphera to Dantiscus. 33 At his death in 1539, the epitaph composed by Alardus of Amsterdam referred to his notable astronomical and cosmographical skills. Quoted in De Vocht, History, 24

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globes or armillary spheres, taking great pride in their extraordinary size and quality. On 15 April, Scepper promised Dantiscus to show him a sphera at his home in Bruges, the best and largest he had ever seen.34 On 30 May, Scepper’s brother-in-law Marcus Laurinus, dean of Bruges and another habitué of the Trilingue, asked Dantiscus for a map which was in his possession, and which was needed for the completion of an enormous terrestrial globe by Scepper’s secretary Livinus Algoet (d. 1547), a former amanuensis of Erasmus. Algoet had accompanied Scepper to Augsburg in 1530, where he made a maritime chart for Dantiscus, perhaps the very same one that Laurinus now wished to borrow.35 These few examples illustrate the entwinement of the circles of court diplomats, Louvain humanists, and instrument-makers at the exact time that Gemma started his career in cosmography. These networks were founded on the courtly patronage of a humanist culture in which cosmography had come to acquire great respect. At least one instrument-maker outside the Louvain Trilingue circle tried to gain access to this network and the commissions that it provided. Henry Baers Vekenstyl, an established Louvain mathematician who built rather sturdy mathematical instruments, contacted Dantiscus on 7 February 1532. Along with his letter, Baers probably presented the astrological directorium for which he had published the manual in 1530.36 Apparently, Dantiscus had not solicited the gift, and there is no trace of any subsequent orders by him or another high patron. Although Baers was a member of the university, probably providing physicians with easy-to-use astrological instruments, he did not belong to the Trilingue circle, while his instruments were

vol. 3, pp. 568–567: “Astrorum motus commeminitque situs./ Novit Athlantiaci metiri pondus olympi,/ Quaeque sub ambobus tenditur ora polis.” In June 1531, the Portuguese poet Angelus Andreas Resendius, a student of Goclenius, dedicated his poem on the deeds of the Portuguese in India to his master, who was equally enthusiastic about the treasures contained in Nicolaus Olah’s Chorographia Hungariae. Resendius’ poem was published as Resendius, Epitome (1531). See De Vocht, History, vol. 2, pp. 395–403; vol. 3, p. 559. On Goclenius’ appreciation of Nicolaus Olah, secretary to the new regent of the Low Countries Mary of Hungary, see De Vocht, History, vol. 3, pp. 560–561. Olah’s close ties with the Trilingue are discussed in De Vocht, History, vol. 3, pp. 36–44. 34 de 116: Dantiscus, Correspondence, ed. De Vocht, p. 71. 35 The letter from Laurinus to Dantiscus is de 129: Dantiscus, Correspondence, ed. De Vocht, p. 82. On Livinus Algoet, see Karrow, Mapmakers, pp. 34–36. 36 This letter is de 190: Dantiscus, Correspondence, ed. De Vocht, p. 129. On Baers Vekenstyl, see the introduction to Baers Vekenstyl, Les tables astronomiques, ed. Poulle/ De Smet. The manual is Baers Vekenstyl, Libellus novus (1530).

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most certainly no competition for the beautiful products of Gemma and his collaborators.37 Likewise, Baers was not implicated in the actual construction of instruments for the high end of the market. Like Franciscus Monachus before him, Gemma preferred to rely on the skills of Gaspar van der Heyden instead.

4. Cosmography and academic mathematical instruction Up to this point, our evidence presented cosmography as a popular pastime on the crossroads where Louvain humanists and their courtly patrons met. But how did this new discipline relate to traditional academic instruction? The preserved records of academic life at sixteenth-century Louvain allow for the reconstruction of a fascinating answer. First of all, we know that Gemma Frisius regularly taught mathematics in his private Louvain home.38 One of his pupils, the cartographer Gerard Mercator, tells us that Gemma’s lessons encompassed both the theorica planetarum (an advanced medieval course in the theory of mathematical astronomy) and the principles of Euclidean geometry.39 From Gemma himself, we learn that he also taught the use of the universal astrolabe.40 This information indicates an interesting mixture of old and new. On the traditionalist side, Gemma covered both the quadrivium of the arts faculty (geometry) and the more specialized curricula of medical students (theorica planetarum). The universal astrolabe, on the other hand, was a relatively new instrument.41

37 Baers at least registered as a member of the University in 1532. See arab, oul 237, fol. 32r. 38 The Frisian historian Suffridus Petri writes in his De scriptoribus Frisiae (1593), p. 160: “Mathematicas artes privatim in aedibus suis docere solebat, ubi et nos eum docentem studiose audivimus.” 39 Mercator’s study of geometry and astronomy under Gemma Frisius must have occurred shortly after 1534/5. See the letter from Mercator to Wolfgang Haller, published in Correspondance Mercatorienne, ed. Van Durme, pp. 164–167. 40 Gemma Frisius, De astrolabo catholico, fol. 81r: “Olim cum Lovanij auditoribus aliquos nostris familiaribus traderem rudimenta Astronomiae ac Geometriae, exposui quoque usum Planisphaerij parallelogrammi.” The term planispherium parallelogrammum can either refer to the universal astrolabes of Gemma and his pupil Juan de Rojas, or to the similar organum Ptolemaei, an instrument for determining the time of day, described in Gemma’s editions of Peter Apian’s Cosmographicus liber. 41 See, for instance, the elaborate discussion of astrological house division in Gemma Frisius’ De astrolabo catholico (1556), which is contextualized in chapter 8.

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How did Gemma’s initiative relate to official university teaching? Private instruction was probably quite popular at Louvain in the 1530s and 1540s.42 We know of at least one other humanist physician, Justus Velsius (c. 1510/5-after 1581), who privately taught mathematics at Louvain in the first half of the 1540s.43 Although the arts faculty was rather suspicious of these private teachers, higher academic authorities actively supported them.44 For instance, when the arts faculty prohibited Velsius from teaching the Dialectica of George of Trebizond (1396–1486), the academic deputies urged it not to overlook the general utility of his lessons.45 Moreover, both Velsius and Gemma Frisius were elected as members of the university.46 Private tutors who provided instruction on specialized subjects definitely had a place in the academic structures of sixteenth-century Louvain. On the whole, this is fairly reminiscent of the fifteenth-century situation, where the university supported mathematical instruction while relegating it to the margins of academic instruction. Since mathematics was usually privately taught by students or professors of the medical faculty, we may assume that Gemma’s lessons continued this tradition.

42 In arab, oul 729, nine discussions in the Council of the faculty of Arts related to private teachings are mentioned between 1536 and 1545. The exceptional autobiographical document of Maarten Snouckaert, who was in Louvain from 1529 to 1534, states that he and his brother took regular private courses on the Institutiones while studying at the faculty of civil law (see Vandermeersch, “Een uitzonderlijk egodocument”). 43 See Vanden Broecke, “Humanism, Philosophy, and the Teaching of Euclid.” Velsius gave his lessons on Euclid at the instigation of his patron Juan de Rojas, a Spanish nobleman in the service of Charles v, who studied mathematics at Louvain between 1541 and 1546 with both Velsius and Gemma Frisius. On De Rojas, see Maddison, “Hugo Helt”; Victor Navarro Brotons, “Rojas Sarmiento, Juan de” in: Diccionario historico, vol. 2, pp. 263–264. 44 E.g., arab, oul 729, fol. 44: “Nullus docere potest privatim logicam phisicam aut grammaticam nisi eos qui visitant pedagogia[m] vel scholam divi petri.” In 1539, a concession was granted (fol. 38: “Facultas prohibet ne ullus privatim doceat logicam aut phisicam nisi eos qui scholas publicas visitant, sed permittit ut grammatica et inferiores privatim doceri possint”) which was however quickly withdrawn (fol. 38: “refertur esse contra statuta facultatis et universitatis item contra concordata inter facultates quod cuique liberum foret docere grammaticam et libellos introductionis, et desuper dantur Deputati”). 45 arab, oul 55, fols. 27v/28r: “Ipsa Facultas artium non sit ita intenta ad proprium commodum quin etiam respiciat eorum utilitatem.” 46 In September 1542, Velsius invokes the privilegium fori, the right for members of the university to be tried before the rectoral court (arab oul 57, fol. 13r). Gemma Frisius became a member of the university council in 1535 (arab oul 273, fol. 146r).

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As a hybrid of academic (astronomy) and artisanal (cartography and instrument-making) traditions, cosmography was only gradually acknowledged in the arts faculty. Our first indication of this change occurs in an edition of Sacrobosco’s De sphaera, published at Louvain in 1547 as a basic astronomical textbook for use at the arts faculty.47 In the preface, the printer Joannes Waen stressed its necessity for the study of cosmography and geography, a relationship that is exemplified by the cosmographical illustrations he provided throughout the book.48 This gradual rapprochement seems to have been consolidated in the reform of mathematics teaching that the arts faculty pursued at the end of the 1550s. In 1559, a deputation of the arts faculty requested financial support from Philip ii (1559–1598) for a muchdesired reform of both philosophy and mathematics teaching, on the model of what was already accomplished for grammar.49 In 1560, the faculty adopted new statutes that prescribed the teaching of the principles of arithmetic, geometry, of the heavens and its motions, as well as Sacrobosco’s De sphaera.50 In the following year, a sum of first three and then six guilders was awarded to each professor who would acquit himself of teaching the introductions to arithmetic and geometry.51

47 The printer Joannes Waen dedicates his Sacrobosco, Sphera (1547) to Jerome Ruffaut, abbot of St.-Védaste near Arras, “ut tui nominis authoritate commendatae, liberius omnibus in scholis [my italics] versarentur” (f. a2v). The spherical shape of the earth is illustrated through the common cosmographical image of a ship observing the changing aspect of a building as it moves away at sea (f. b1v). We find a simplified version of the typical free-standing armillary sphere that illustrated Peter Apian and Gemma Frisius’ Cosmographicus liber (f. b8v). A didactic volvelle (another standard feature of cosmographical treatises) is included for the illustration of various definitions of rising-times (f. c4v). A terrestrial globe with indications for geographical latitude occurs on fol. d8v. On Sacrobosco’s textbook, see Sacrobosco, The Sphere, ed./trans. Thorndike. 48 Ibid., fol. a2v: “Cosmographia certe & Geographia plane essent inutiles hac cognitione sublata.” 49 arab, oul 729, fol. 71: “1559, folium 95. Deputatio ad suam Majestatem pro subsidio habendo et exponitur Facultatem Artium esse fundamentum ceterarum, quod reformaverit jam grammaticalia et meditetur id quoque praestare in philosophicis quibus adjunget principia mathematica, cumque aliae facultates fuerint gratificatae id quoque confidat Facultas Artium.” 50 Ibid., fol. 72: “1560, folium 121. Nova Statuta facultatis (…) Traduntur principia Aritmeticae et geometricae et sphaera de Sacrobosco et coeli et motus eorum.” 51 Ibid., fol. 75: “1561, folium 157. Singulo professori facultas dat tres florenos ut doceat introductionem ad aritmeticam et geometriam (…) 1561, folium 160. Conceduntur 6 florenos singulis professori ut doceant[ur] Aritmeticam et Geometriam.”

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On the one hand, this reform reduced the fifteenth-century curriculum of mathematical teaching. Musica was abandoned both in theory and in practice, while the amended statutes of 1567/8 make no mention of geometry. A survey of teaching activities at the arts faculty in 1568 lists introductions to arithmetic and astronomy for all four pedagogies, while an elementary course in geometry was offered to students of the Porc only.52 On the other hand, the reform also updated the content of mathematical instruction. In 1568, the pedagogies of the Castle and the Falcon had abandoned the philosophical arithmetic of the Boethian tradition for the thoroughly practical orientation in Henricus Glareanus’ (1488–1563) De vi arithmeticae practicae speciebus epitome or Gemma Frisius’ Arithmeticae practicae methodus facilis.53 For their introduction to astronomy, the students of the Castle had exchanged Sacrobosco’s old De sphaera for a brand-new textbook by Cornelius Valerius (1512–1578).54 Although Valerius’ textbook was clearly inspired by its thirteenth-century predecessor, it also departed from this model in significant ways. Brief introductions to the related disciplines of geometry and cosmography accompanied the main text, which stands out by didactic clarity and practical orientation.55 Other parts of his treatise incorporated information that derived from the more advanced theorica planetarum-tradition.56 These innovations enabled the arts faculty to compete successfully with the established system of private mathematical instruction.

52

Vander Linden, “L’université,” pp. 20–28. On the use of Glareanus, see Vander Linden, “L’université,” p. 23. Glareanus’ arithmetic was first printed in Freiburg, 1539. Later editions appeared in Freiburg in 1543, 1550 and 1555; at Vienna c. 1550 and in Paris in 1551, 1561 and 1563. See Fritzsche, Glarean, pp. 107–108; Dürst, “Glarean als Geograph und Mathematiker.” Gemma’s arithmetic (first published Antwerp, 1540) was easily the most popular of its kind in the sixteenth century. Extant editions are described in Van Ortroy, Biobibliographie. On the use of Gemma’s textbook, see Vander Linden, “L’université,” p. 27. 54 Vander Linden, “L’université,” p. 23. First edition is Valerius, De sphaera (1561). 55 Compare Valerius’ initial definition of a sphere (f. 5v: “globus absolute rotundus & volubilis, mundi formam referens, quae circulos & varias siderum figuras continet”) with that in Sacrobosco’s text (see Sacrobosco, Sphere, ed. Thorndike, pp. 76–77). Valerius’ text was also intended to be used in combination with a celestial globe. See Valerius, De sphera, fol. 14r: “Magno usui circulus hic erit in globo astrifero ad ortus & occasus siderum, tum ad dierum noctiumque inaequalitatem depraehendendam.” 56 Discussions of the motion of the tenth, ninth and eighth sphere occur in Valerius, De sphaera, fols. 21v/22r. 53

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The reform of mathematical teaching at the arts faculty may have been related to the establishment of a new public chair of mathematics by the city council in 1563. Its first beneficiary was Joannes Stadius (1527–1579), whose popular Ephemerides had already gone through two editions by the time of his appointment. Nothing is known about the content of Stadius’ lessons,57 but his successor Peter Beausard (1569) seems to have limited himself to didactic and practical introductions to geometry and arithmetic.58 This suggests that the public lessons in mathematics were quite similar to what was offered at the arts faculty in the late 1560s. This serves as an important memento for our interpretation of early modern university teaching. As a whole, “academic instruction” refers to the more-or-less standardized curricula of the artistic and higher faculties. But it cannot be properly distinguished from more informal modes of instruction, organized in the margins of official teaching and often concentrating on new topics. Although cosmographical didacticism operated in a grey zone at the margin of official academic teaching, it nevertheless constituted an acknowledged and well-respected part of Louvain university life. Another important set of sources allowing us to assess the continuity between late medieval astrology and early modern cosmography are the new Louvain instruments, whose use constituted an important topic in mathematical classroom instruction of the sixteenth century. The next four sections describe how Louvain cosmographical instruments merged new geographical interests (section 5) with old astronomical and astrological concerns (sections 6–8).

5. Humanism and cosmography From its very beginning, Louvain humanist teaching attached considerable importance to geography. Both Willem Neesen and Vives gave a course on Pomponius Mela’s (fl. 43 ad) De situ orbis in 1519 and 57 Stadius was paid 300 florins by the city council for his lessons on mathematics and ancient history. See sal, L’université 3991, folder 6: “D. Stadio pro duabus Lectionibus – iij c R[henani].” 58 Joannes Molanus, a contemporary colleague of Beausard at Louvain, states that Beausard taught the In geometrica elementa eisagoge (Antwerp, 1565) of Arnold de Lens in his public lessons. See Molanus, Historiae, ed. De Ram, p. 579: “Arnoldus de Lens, medicus ducis Moscoviae, conscripsit geometrica elementa a Plantino excusa. Quae Beausardus publica praelectione sua digna esse judicavit.” Beausard’s own Arithmetices praxis (Leuven, 1573) was explicitly published for the benefit of his students.

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1521/2, thereby implementing the advice of their friend Erasmus.59 In De recta pronunciatione, Erasmus stressed that “Geography should come before [rhetoric], and be thoroughly mastered. Arithmetic, music, and astronomy need only be sampled.”60 In his opinion, geography was useful for both history and poetry, where it served to identify the terms that the ancients used for mountains, rivers, regions, and cities.61 He recommended Pomponius Mela when one needed fast facts and lacked the time to collect various bits of information in a personal commonplace book. This last statement suggests that a concern for stylistic variation (copia) was never far removed from Erasmus’ interest in ancient geography. But his desire to obtain accurate information was equally important. This aspect provides us with a link to cosmography, geography’s mathematical twin. In 1533, Erasmus provided the prefatory letter for an editio princeps of Ptolemy’s Geography, published by his friend Joannes Froben.62 While acknowledging the worth of ancient chorographers and geographers like Strabo, Erasmus praised Ptolemy for crowning their work by means of mathematics.63 But he also acknowledged the imperfections in Ptolemy’s lists of geographical coordinates, which only a skilled modern cosmographer could correct.64 In a letter that Erasmus had previously received, Anselm Ephorinus (c. 1505–1566) identified Peter Apian as this savior of Ptolemaic cosmography.65 59 Erasmus, De ratione studii, trans. McGregor, p. 673. On the teaching of Pomponius Mela at Louvain, see De Vocht, History, vol. 1, p. 460 and vol. 2, p. 607. 60 Erasmus, De recta pronuntiatione, trans. Pope, p. 387. 61 Erasmus, De ratione studii, trans. McGregor, pp. 672–673. 62 This manuscript is now at the Vatican Library, Palatinus Graecus 388. Before this manuscript was printed, Erasmus supposedly made a few technical notes in the margins, which were included in the Froben-edition: see De Smet, “Erasme et la cartographie.” The attribution of these notes to Erasmus, as well as his personal involvement as editor of the Geography, was refuted by Reedijk, “The story of a fallacy.” The prefatory letter is Erasmus, Opus epistolarum, ed. Allen, vol. 10, p. 2760. 63 Erasmus, Opus epistolarum, ed. Allen, vol. 10, p. 2760:149–150: “Complures quidem tum apud Graecos, tum apud Latinos mixtim de Geographia et Chorographia conscripserunt, inter quos nemo Strabone vel diligentior vel copiosior. At Ptolemeus omnium primus hanc disciplinam ad certiorem rationem redegit, commentus dimensionem latitudinis universi orbis a polo ad polum, longitudinis ab exortu ad occasum, adhibita collatione terrae habitabilis ad celum, ut iam non facile quis toto quemadmodum aiunt coelo possit aberrare.” 64 Erasmus, Opus epistolarum, vol. 10, p. 2760:150: “Utinam et numerorum notas sicut a Ptolemeo traditae sunt incorruptos haberemus, praesertim libro octavo. Sed hanc quoque, ut spero, provinciam aliquis arripiet, cui et ingenium et eruditio et ocium suppetet tam arduo negotio par.” 65 Erasmus, Opus epistolarum, vol. 9, p. 2606:430: “Videbimus illum, qui olim

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Other Louvain humanists of the 1520s shared Erasmus’ enthusiasm for cosmography. In his encyclopaedia of the liberal arts, the young pedagogue Joachim Fortius Ringelberg (c. 1499-after 1531) wrote that “Cosmography is not only of admirable use for reading Geographers, but also for any author who mentions zones, climes, longitude, and latitude.”66 One can readily understand why Gemma Frisius, a Trilingue-student with considerable cosmographical skills, was greeted with particular enthusiasm among Louvain humanists. In his cosmographical treatises, Gemma occasionally played out his role as teacher of ancient geography.67 But he consistently combined this with an emphasis on the innovation of geographical knowledge by Spanish and Portuguese seafarers.68

6. Astronomy and cosmography The success of terrestrial globes epitomizes this widespread interest in ancient and contemporary geography. But these instruments also Rhomae Ptolomeum tabulis ornavit, multum errasse. Ipse Apianus tabulas omnes manibus propriis confitiet, quippe qui iam norit quo vitiatae loco illae priores et ibi nobis imposuerint.” 66 Fortius Ringelberg, Opera, p. 425: “Quae ad legendos non Geographos modo, verum autores omneis, qui ullam zonarum, climatum, longitudinis, latitudinis mentionem faciunt, mire conducent.” 67 Gemma Frisius’ 1539 edition of Apian’s Cosmographia was concluded with a poem by Diego Pirez (Didacus Pyrrhus, a former student of the Trilingue who came from a Portuguese merchant family at Antwerp), which stressed this aspect as the book’s foremost quality. On Didacus Pyrrhus, see De Vocht, History, vol. 3, pp. 419– 421. 68 See Gemma’s letter to the reader of his De principiis, dd. 15 September 1530: “Sed quum indies novae terrarum partes lustrentur, quarum hij autores non meminerunt nec tamen ideo culpandi.” Apart from the obvious stimuli coming from trans-Atlantic trade, one should also consider that agricultural productivity was expanding beyond previous limits in the Low Countries, after the critical last decades of the 15th century. Demographic expansion, an urban population of 30 to 55 % and a secure import of wheat from the Baltic created new opportunities for agricultural specialisation in dairy, “industrial” crops, and horticulture, which ensured a higher income and reduced the size of average holdings. Market-oriented farming turned land into a valuable commodity, justifying a more precise and complete system of recording private property. The first important result was the introduction of mapping in the surveyor’s trade and the gradual replacement of medieval written surveys by mapcentered landbooks. The expectations of a surveyor’s commissioner shifted towards precise and clear maps of his property, on which information concerning tithes or surface area was indicated. See Van der Wee, “The agricultural development of the Low Countries”; Kain/Baigent, The cadastral map, p. 45; Harvey, “Local and regional cartography,” pp. 491–493.

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provided much specific astronomical knowledge, as a closer study of Gemma Frisius’ De principiis astronomiae et cosmographiae (1530) will show. This was the manual for a lost terrestrial globe that Gemma constructed in 1529/30.69 Apparently, this terrestrial globe also included the positions of important fixed stars.70 The heading at the top of the pages of part ii (De usu globi) read “on the use of the astronomical globe.” Gemma’s instructions catered for both cosmographical and astronomical interests. His chapter on the determination of terrestrial longitude inevitably included a discussion of various astronomical methods, based on the lunar cycle.71 But Gemma also focused on astronomical problems that were quite irrelevant to cosmography. As he instructed his audience to find the sun’s position on the ecliptic by means of the horizon-ring, Gemma emphasized that precession would render the data obsolete at a rate of only 44’ per century.72 His description of methods with which to situate celestial bodies on the globe’s surface included the use of astronomical instruments like the cross staff. This method, Gemma added, enabled one to determine planetary positions as well as the place of “all stars that are affixed to the southern hemisphere, unknown to Ptolemy and others.”73 The determination of terrestrial longitude also introduced the accurate handling of astronomical tables, ephemerides, and instruments.74 These elaborations involved the buyers of Gemma’s globes in a joint project to improve cosmographical knowledge through astronomical observation. The purchase of a globe provided reliable knowledge, as well as an entry-ticket into the community that corrected and expanded such knowledge.

69 For a descriptive reconstruction of Gemma Frisius’ first globe, see Van der Krogt, Globi Neerlandici, pp. 48–51. 70 See Gemma Frisius, De principiis, fol. a2r: “Elapsis annis plus minus viginti tribus, cum pro aetatis meae modo ac capacitate dedissem in lucem Globum Geographicum una cum insignioribus octavi orbis stellis.” 71 De principiis, pp. 62–71. See Pogo, “Gemma Frisius.” 72 De principiis, pp. 32–33: “Quin etiam per successionem longam alia correctione opus fuerit. Nam in centenis fere annis adiicienda sunt 44 fere minuta, & in aliis pro ratione.” 73 Ibid., p. 61: “Hac arte omnia sydera quae inferiori hemisphaerio infiguntur, Ptolomaeo, aliisque incognita, per nostri seculi nautas in globum depingi facile possent.” 74 Ibid., pp. 62–64.

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7. Astrology and cosmography Although Gemma’s first globe taught both cosmographical and astronomical skills, there was only one discipline that encompassed each of the globe’s functions: astrology. Most operations that were previously described also carried direct relevance to astrology. Timetelling, finding the position of a celestial body, determining terrestrial coordinates, were all standard procedures of the astrologer’s practical astronomy. When Gemma advocated the use of fixed stars to determine the time at night, he suggested that one would also calculate and mark planetary positions on the globe.75 Planetary positions had no distinct cosmographical purpose, but were all the more important in astrology. Time could be expressed in common unequal hours, each of which Gemma invested with a specific astrological relevance.76 Near the end of his globe manual, Gemma focused on specifically astrological functions of his instrument, such as the determination of astrological houses, or the practice of revolutions and prorogations (see chapter 8).77 In order to perform this last task, the globe was fitted with a dedicated brass position semi-circle.78 This device enabled the globe to compete with much more laborious astrological tools like Regiomontanus’ Tabulae directionum et profectionum.79 Within the realm of instrument-based astrological practice, the size and threedimensionality of globes also made them more precise than the popular astrolabe’s two-dimensional representation of the heavens.80 This 75 Ibid., p. 39: “Atque hac industria depingimus loca planetarum in globo habita longitudine & latitudine ex tabulis, volvendo deinde scilicet quartam altitudinis ad gradum longitudinis in ecliptica, latitudinem vero in quarta altitudinum sive alio quadrante quaerendo: ibi enim est locus planetae: qui aut cera aut carbone notandus est ut possit facile deleri, nam haec loca indies migrant.” 76 Ibid., p. 53: “Quandoquidem Astronomi omnem diem artificialem et similiter noctem, dividunt in 12 portiones: quarum cuilibet tribuunt dominium unius de septem planetis, sequentem vero horam sequenti adsignant planetae.” 77 Ibid., pp. 73–81. 78 Ibid., p. 28: “Item circulus positionis qui semicirculus est affixus horizontis & meridiani duabus sectionibus, exemptilis etiam, ut ab una mediatet in aliam transferri possit: Hic Astrologorum iudiciis inservit.” 79 Regiomontanus, Tabulae directionum (1552), vol. 1, fol. b1v: “Nam & ipse modum dirigendi per sphaeram solidam officio semicirculi Meridiano & Horizonti coëuntis summopere laudat, & Ptolomeum idem (quod verum est) sensisse arbitratur. Postremo tamen in tabulis suis [i.e., tables of oblique ascension] ponit fiduciam, ignorans utique quantum his duobus modis interesse possit discriminis, quod revera 5. gradus (absurdum dictu) nonnunquam excedit.” 80 It shared this advantage with the armillary sphere and the astronomical ring.

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advantage was not lost upon Mercator: “Imitation constitutes almost the entire use of the celestial globe, allowing anyone to learn how to adjust its parts to any similar part of the heavens.”81 Disadvantages of the globe included its cost, difficult construction, and frailty during transportation.82 Gemma’s manual also revealed unsolved astrological problems. The passage on planetary hours was concluded with Gemma’s avowal that he accorded little weight to these.83 In chapter ii.22, he informed his audience of the contemporary debate on astrological house division. Gemma Frisius described no less than three methods: the single longitude method of Ptolemy and Firmicus Maternus, the equatorial (fixed boundaries) method of Regiomontanus, and the prime vertical (fixed boundaries) method of Campanus.84 Gemma equipped his globe to handle each of these methods, explicitly refusing to commit to any single one of them.85 More extended discussions on house division occurred in Gemma’s later cosmographical publications (see chapter 8). In this early stage of his career, Gemma’s cosmographical didacticism stimulated public awareness of this problematic and of his ability to deal with it.

See Beausardus, Annuli usus (1553), fol. 5v: “Inter varia Matheseos instrumenta, quibus coeli motus observantur, & calculantur, ea equidem meo iudicio, si quid iudicio, semper visa fuere certissima & usui aptissima, quae tali industria ac arte confecta sunt, ut coeli, (…), figuram ac typum referant (…) Sphaericum enim in planum certe et sine omni errore transferre, omnium difficillimum, imo impossibile arbitror.” 81 Mercator, Declaratio, ed. Van Raemdonck, p. 22: “Totus fere usus globi coelestis consistit in imitatione, ut quis omnes eius partes omnibus similibus partibus in coelo sciat aptare.” 82 See Gemma Frisius, De astrolabo catholico (1556), fol. 9r; Beausard, Annuli Usus, fol. a1r. 83 De principiis, p. 53: “Haec cum parvi sint momenti, levi quod aiunt brachio pertranseo.” 84 For a more substantial discussion of this problematic, see chapter 8. This study adopts the nomenclature for methods of house division of North, Horoscopes and History. 85 De principiis, p. 75: “Sed nos in re tam difficili sententiam non dicimus, dabitur fortassis commodior de his disserendi locus. In praesentiarum omnibus illis nostro globo satis fiet.”

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8. Cosmographical instruments and astrological theorica: Gerard Mercator’s astrological instrument (1551) Among Gemma’s pupils, it was Gerard Mercator who most actively integrated the realms of astrology and cosmographical instrument making. This element is most clearly distinguishable in the astrological volvelle that Mercator designed and printed at Louvain in May 1551.86 This unique instrument complemented the famous celestial globe that Mercator had published one month before: For it was our intention to adapt this work not only to astronomy but also to astrology. For this purpose we have produced an isagogical instrument for the art of making judgements out of Ptolemy, Alcabitius, Joannes of Seville, Cardano and some other astrologers.87

In the first sentence, Mercator explains that his celestial globe served both astronomy and astrology. The first discipline, Mercator claimed, was served by his use of Copenican precession theory; the second by his inscription of each star’s “nature” or astrological virtues.88 Mercator clearly intended to associate his notions of “astronomy” and “astrology” with the scholastic traditions of astrological theorica: astronomical theory and astrological physics. This interpretation is confirmed by the vocabulary of Mercator’s further instructions. Although his astrological instrument offered little more than a novel presentation of popular astrological textbooks, Mercator consistently referred to its lists of significations as “natures.” This natural-philosophical terminology was supplemented with other scholastic physical concepts like “intension,” “remission,” or “commixture.”89 This shows that Mercator’s transfer of traditional astrological textbooks to the format of cosmographical instruments simultaneously served to “anchor” traditional astrological theorica. Mercator clearly referred to this additional agenda in the following remark: Thus he will have set up very suitably a figure of the sky for that time and place and will openly contemplate all things in one gaze. There will be no more need for lengthy wandering among the authors or a good

86

The single known extant copy of this volvelle, which seems to have escaped scholarly attention, is in Basel, Historisches Museum, nr. 1876.20. A description and interpretation of this instrument, with a transcription and translation of the explanatory sheet on the back, is provided by Vanden Broecke, “Dee, Mercator, and Louvain Instrument Making.” 87 Vanden Broecke, “Dee, Mercator, and Louvain Instrument Making,” p. 236. 88 Ibid., p. 235. 89 Ibid., p. 237.

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chapter five memory of many things. (…) But he who is not a natural philosopher has to follow the writings of the astrologers and, as if in an immense forest, gets lost amidst a multitude of meanings.90

The astrological volvelle enabled the astrological practitioner to become a natural philosopher because of its ability to avoid a multitude of meanings. This brief statement points to a double background that has become familiar by now. First, it responds to the exposure of internal contradictions in the traditional astrological canon by Pico and his Louvain epigone Scepper; second, it points to various attempts at controlling the ensuing problems. These efforts emphasized the imposition of discipline on popular judicial astrology through traditional theory (i.e., theoretical astronomy and Ptolemaic astrological physics). Mercator’s astrological volvelle followed a similar line, as can be shown from the parts of his textual sources that were not included. In the case of Ptolemy’s Tetrabiblos, we find Mercator adopting most of the material in book i, but excluding the lengthy materials on astrological predictions in the other books. From Schöner’s Opusculum astrologicum (1539), Mercator borrowed the content of the “compendious introduction” that followed the first, astronomical part, but none of the material on the judgment of elections or nativities in parts 3 and 4. Clearly, Mercator identified the astrological problematic with the practice of making judgments, and its solution with a methodical combinatorics of the individual effects of celestial bodies: By these few things we think that the first approaches and method to a special art have been sufficiently disclosed, while many have provided a more complete and sufficiently clear treatment thereof. Now, take our difficulties to heart, studious Reader. Even if anyone should ridicule Astrology and lay her aside, he should know that this hardly impresses us, for we wanted to secure every man’s studies.91

Strangely, the academic echoes of Mercator’s didactic narrative did not reflect the audience that actually bought the combination globevolvelle. One of the main dealers of Mercator globes in the Low Countries was Christophe Plantin (c. 1520–1589).92 His accountbooks show that Plantin usually sold the Mercator globes for 24 to 25 guilders a pair before 1575. Due to general inflation (which particularly affected the price of copper), the price for Plantin’s cus90

Ibid., p. 239. Ibid., p. 240. 92 A good survey of the trade in Frisius and Mercator globes is provided in Van der Krogt, Globi Neerlandici, pp. 72–75. 91

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tomers rocketed to between 30 and 57 guilders in 1575/6. In the 1560s, Plantin paid his printers around 20 deniers (1/3 guilders) a day, roughly the same as what the masons at work on the nearby cathedral earned.93 This means that the price of a small globe amounted to one week’s pay, while the beautiful Mercator globes would have cost the equivalent of almost three months of work, 190 pounds of ham or well over 1500 liters of barley, well outside the reach of most university students. This leads us back to the wealthy amateurs who patronized Louvain cosmography. Much like Cornelius Scepper, they probably shared an interest in astrology as an aid in the determination of public and private policies. Indeed, the public wielding of a cosmographical instrument was often constructed around the image of the gentleman-astronomer/astrologer who was independent from external authority or counseling. One of the earliest texts from the Southern Netherlands that promoted this image was a Latin prognostication from Antwerp for the year 1518. This pseudonymous prognostication was ascribed to Ramiro Gaditano, a Spanish nobleman and former student of astronomy and astrology at Salamanca.94 Having traversed many seas, Gaditano had recently set foot on land in Antwerp. The Spaniard was reasonably impressed with the sumptuousness of this port, and immediately went about to determine the correct latitude with his astrolabe, comparing it to the data in Ptolemy’s Geography, which he consulted in a local bookshop. Comparing his result to the values that local astrologers accepted, Gaditano concluded that their prognostications were calculated for the wrong horizons, and immediately set about to write a superior set of predictions. Such accusations of astronomical incompetence were a common method to establish one’s position in the astrological market.95 Novel was the link between astronomical/astrological competence and high social status. It is this image that instrument makers like Mercator appealed to when they negotiated between the worlds of craftsmen and wealthy clients.96

93 See Verlinden/Craeybeckx (eds.), Dokumenten voor de geschiedenis van prijzen en lonen, vol. 1, pp. 391; 466–467; 537. 94 Ramyrus Gaditanus, Mantia sive divinatio syderalis (1518). 95 Compare to the discussion between Gaspar Laet Jr. and Jean Thibault c. 1530 (Interlude). 96 The non-profitable delights of the study of mathematics and use of globes were also emphasized in pedagogical recommendations for Elizabethan noblemen. See Feingold, The mathematicians’ apprenticeship, pp. 190–193.

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chapter five 9. Gemma’s familia: mathematics teaching and the medical profession

Gemma’s didacticism addressed the cosmographical interests of networks linking courtly patrons to the Louvain humanist circle. This element propelled the better part of Gemma’s early career.97 He rose to capture ambassador Dantiscus’ favor with particular swiftness. Already on 16 April 1531, Joannes Campensis maliciously referred to Gemma as the Polish ambassador’s favored stratagema.98 But patronage also included a perilous level of commitment. In the beginning of 1532, Dantiscus invited both Gemma and Campensis to return to Poland with him. After much vacillation in Louvain and his native Frisia, Gemma eventually declined to follow his patron.99 More than two years later, Gemma finally explained his situation and motives to Dantiscus.100 After the ambassador’s departure, Gemma had tried his hand at making a living from his mathematical skills, none of which turned out to be as satisfying as permanent service under Dantiscus.101 As an alternative, Gemma supported his young family through medicine, which he had previously studied for one or two years.102 This letter highlights how mathematicians like Gemma grappled with a limited market for cosmographical instruments, minimal control over the commercial circuit, and the hazards of courtly patronage. A mathematician’s family could not be supported through the commercial market for cosmography alone, since it usually involved the services of publishers, printers, and engravers.103 Dantiscus’ patronage was essential, but required considerable sacrifices in terms of 97 Another tangible example of Gemma’s relations with the Louvain “literary” humanist scene is his contribution of an elegy in four verses, and a dialogue of forty lines, on the death of chancellor Mercurio Gattinara (1530) to Epitaphia (1531). 98 de 117: Dantiscus, Correspondence, ed. De Vocht, pp. 71–72. 99 Scepper expresses his regret in de 202: Dantiscus, Correspondence, ed. De Vocht, pp. 135–136. 100 de 291: Dantiscus, Correspondence, ed. De Vocht, pp. 225–226. De Vocht only paraphrases this letter, which has been transcribed and published completely by Waterbolk, “‘Reception’ of Copernicus’ teachings,” pp. 239–240. de 291 was addressed to Dantiscus from Louvain on 26 July 1534, almost two months after Gemma’s marriage on 2 June. 101 Waterbolk, “‘Reception’ of Copernicus’ teachings,” p. 239. 102 For further details on Gemma’s marriage, see Van Ortroy, Bio-bibliographie, pp. 20–22. 103 On the relationship between patronage, the commercial book-market, and remuneration of authorship, see Chartier, Culture écrite et société, pp. 55–64 and pp. 88– 93; Long, Openness, Secrecy, and Authorship.

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geographical and social relocation. Only Gerard Mercator managed to unite the roles of instrument-designer, instrument-maker, and publisher in one person, thereby acquiring sufficient commercial control to reap adequate profit from his mathematical activities.104 Gemma, on the other hand, had few options besides the pursuit of medicine and classroom teaching to support his family. In doing so, he reconnected with the old professional pattern of late medieval medical students, who financed their studies by teaching mathematics to younger arts students.105 Like these predecessors, Gemma Frisius congregated a familia of students around him who took lessons in his private home. This context provides us with quite a few names that will figure prominently in the rest of this book: John Dee, Cornelius Gemma, Antonius Gogava, Sixtus ab Hemminga, Gerard Mercator, Juan de Rojas, and Joannes Stadius all claimed to have learned at least part of their mathematical trade under Gemma Frisius. Gemma summarized his new professional situation in a letter, written to Dantiscus on 12 December 1539: As for the state of my affairs, I earn my living through medicine and have put the mathematical arts somewhat aside, as my situation, which requires a profitable rather than a joyful art, urged me to do.106

The available evidence suggests that Gemma found both profit and joy in the medical profession. Typical of Gemma’s genuine commitment to medicine is the famous nightly scene (set between 1535 and 1537) in which he aided young Andreas Vesalius to rob a corpse from the gallows outside Louvain.107 On 30 August 1541 he obtained a doctorate in medicine, which allowed him to access the highest levels of the medical market. In the preface to his De radio astronomico (1545), Gemma expressed a deep enthusiasm for the simultaneous

104 For a good analysis of Mercator’s position as author, maker, printer, and publisher of cosmographical products, see Léon Voet, “Uitgevers en drukkers” in: Mercator, ed. Watelet, pp. 133–149. 105 See Schwinges, “Student education, student life” in: De Ridder-Symoens (ed.), Universities in the Middle Ages, pp. 197–198. 106 de 407: Dantiscus, Correspondence, ed. De Vocht, pp. 320–322: “Quantum vero ad statum rerum mearum attinet, ego arte medica victum querito: artes vero Mathematicas nonnihil sepono, ita urgente nostrarum conditione, quae quaestuosam magis requirunt quam iucundam artem.” Gemma probably exaggerated his disdain for medicine, since Scepper praised Gemma’s zeal and skill as a physician to Dantiscus only half a year later. See de 417: Dantiscus, Correspondence, ed. De Vocht, p. 330. 107 Related in the dedicatory letter of Vesalius, De Fabrica (1543).

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rebirth of mathematics and medicine in his own time.108 One may also assume that Gemma played an active role in the public anatomy lessons that his friend Thriverus had started in the early 1540s.109 The last trace of Gemma in the Dantiscus correspondence occurs in a letter from Scepper (1546), who praises his former protégé as a famous medical practitioner, who was recently sent for by Charles v.110 Obtaining a medical doctorate clearly allowed Gemma to regain the Brussels patronage circles with more security than cosmography allowed for. Like his fifteenth-century predecessors, Gemma also connected his position as a medical practitioner with astrological services. A fortuitous event in the summer of 1541 provided him with just the right motive to do so. On 15 July, Scepper wrote Dantiscus that he had provided Gemma with a copy of Rheticus’ Narratio prima (1540).111 Five days later, Gemma enthusiastically wrote Dantiscus about his hopes to see various astronomical problems finally resolved.112 Copernican astronomy gave a new impetus to Louvain mathematics in the 1540s; once again, astrology played an essential part in its reception and distribution (chapter 6).

108 Gemma Frisius, De radio, fols. 3v-4r:: “Demum nostris hisce postremis mundi temporibus e profundis rursum tenebris videmus disciplinas omnes revocari, ac quasi denuo nasci. Ego quidem de aliis haud facile iudicavero disciplinis, quam in quibus aliquot trivi annos iam inde a teneris unguiculis: Medicinam dico, quae naturalis Philosophiae haud exiguam complectitur partem, & Mathematicas artes, quae ad maximarum perducunt rerum cognitionem. In his tanta vel mea aetate satis exili facta est permutatio ac diversitas, quanta est inter umbram ac ipsam rem lumine irradiatam.” 109 The evidence is summarized and critically reviewed by Hallyn, “Een vierde nota.” Thriverus’ public lecture on anatomy started on 12 June 1541: see De Vocht, History vol. 2, p. 537 note 4. Gemma’s biographer Suffridus Petri, who attended the lectures of both men, and generally provides very reliable testimonies, emphasizes the friendship between Gemma and Thriverus. See Suffridus Petri, De Scriptoribus Frisiae, pp. 95–96. 110 See De Vocht, History vol. 2, p. 562. Scepper’s letter to Dantiscus is de 476. 111 de 426: Dantiscus, Correspondence, ed. De Vocht, pp. 340–341. De Vocht only paraphrases this letter, the crucial passage of which has been reproduced completely by Waterbolk, “‘Reception’ of Copernicus’ teachings,” pp. 233–234. Waterbolk’s essential article has settled problems relating to the chronology of Gemma’s gradual acquaintance with the Copernican theory, and the channels through which this happened. 112 de 429: Dantiscus, Correspondence, ed. De Vocht, pp. 344–347. I agree with Bernard R. Goldstein, who does not accept Waterbolk’s claim that Gemma read a manuscript of the older Commentariolus, and referred to it in this letter. See Goldstein, “Remarks on Gemma Frisius’ De Radio Astronomico et Geometrico,” p. 177.

INTERMEZZO

A FEW COMMENTS ON THE USE AND NATURE OF ASTROLOGICAL REFORM

Although the universal Flood failed to materialize, contemporaries remained alert about the effects of the February 1524 conjunctions. The Bolognese notary Andrea Pietramellara recorded that the weather in February 1524 was surprisingly fair. From March through July, however, heavy showers and storms frequently induced the local clergy to make supplications through prayer and the ringing of church bells. By the beginning of the fall, Pietramellara witnessed an increasing number of outbreaks of the plague.1 In 1556, the Louvain alumnus Joannes Stadius reminded his readers how 1524 had indeed been a particularly wet year.2 Germans linked the conjunctions with the rise of Lutheranism.3 In 1583, Sixtus ab Hemminga mentioned how the conjunctions were often said to have caused the German Peasants’ War and the captivity of François i at Pavia (1525).4 If anything, this suggests that the courtly calls for astrological reform were highly problematic. Many contemporaries must have felt that the dire prospects of the 1524 conjunctions had been confirmed to an important extent. Presumably, this was even more the case before February 1524. Hence, we must carefully question why court practitioners like Pigghe and Scepper felt the need to advocate astrological reform.

1. Business as usual: Albert Pigghe vs. Gaspar Laet In his reply to Pigghe’s attack, Gaspar Laet leaked insider information about the Louvain origins of Pigghe’s astronomical corrections. 1

Thorndike, History, vol. 5, pp. 231–232. Stadius, Ephemerides (1556), fol. a3v: “Sic Planetarum in humidis signis congressus humiditates anno 1524.” 3 Thorndike, History, vol. 5, p. 233. 4 Ibid., vol. 5, pp. 310 and 396; Ibid., vol. 6, p. 116. 2

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More specifically, Laet claimed that Pigghe copied everything from a treatise that was passed on to him by a clergyman living outside Louvain.5 Although this story cannot be verified, it does suggest that Laet and Pigghe belonged to contiguous circles in the Low Countries. Pigghe’s Defense used every possible means to distance itself from the culture of annual prognosticators to which Laet belonged. Even so, Pigghe did not succeed entirely. When introducing Laet to his readers, Pigghe stated that his “name is famous among the French,” and admitted that Laet was “generally held to be the foremost astrologer.”6 It seems doubtful whether Pigghe’s audience would have needed an introduction to Gaspar Laet. Already in 1494, Simon de Phares attested to Gaspar Laet’s extraordinary success in France.7 His annual prognostications enjoyed the dubious honor of being frequently pirated at Paris.8 Laet’s prognostications probably reached the French court as well: Pigghe suggestively wrote that such popular predictions enjoyed equal support from kings and princes.9 Laet’s French connections enable us to see Pigghe’s call for astrological reform in a different light. Pigghe always claimed that his attack was spurred by Laet’s excessive use of conjunctionist astrology. But closer inspection shows that Laet’s methodology was hardly ex-

5 See Laet, Prenosticatio (1520), fol. a1v: “Item et aliud capitulum apologeticum: quem tractatum noster suffurator accommodato habuit cum lovanij esset studens a quoddam religioso viro docto mathematico extra lovanium in rure degente. ex quo tractatu totum id quod de octavo spera longo sermone contexit suffuratus est, nullam mentionem de docto viro faciens sibi et alijs persuadens quasi ex suo capite emanasset.” 6 Pigghe, Astrologiae defensio, fol. 6r: “Quorumque unus ex his, cuius nomen est apud Gallos celebre, & primus praecipuusque astrologus habetur Gaspar Laeth, Physicus Antwerpiensis.” 7 De Phares, Recueil, ed. Wickersheimer, pp. 267–268: “Maistre Jaspart Layet, filz dudit Jehan Layet à Louvain, a esté moult aprecié de Jehan de Horne, evesque du Liege, pour les prenosticacions qu’il a accoustumé de fere par chacun an, qui courent par le pays de Flandres et en vient en France, touttefois mal translatées (…) Cestui, en ses prenosticacions, a par plusieurs ans dictes choses, desquelles l’on a veu cothidiennes experiences.” 8 Laet himself warned against pirated prognostications at the end of his prognostication for 1524. See also Perrat, “Un tas de prognostications de Louvain.” 9 Pigghe, Astrologiae defensio, fol. 2v.

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ceptional.10 Instead, it seems that Gaspar Laet formed a direct threat to Pigghe’s status as an astrological practitioner at the French court.11

2. Secrecy, openness, and astrological reform While Pigghe emphasized the incommensurability of his Ptolemaic prediction for 1519 with Laet’s prognostications, his Parisian audience probably viewed both men as direct competitors. How did Pigghe circumvent this problem? In his prognostication for 1519, Pigghe analyzed the impact of a solar eclipse on the geniture of François i. This exercise was rather harmless, since Pigghe’s conclusions were uniformly positive.12 Incidentally, Laet reached the same result in his own prognostication for 1519.13 However, the rules of the genre obliged Laet to provide more contentious information on other rulers (Leo x, Maximilian of Austria, and Henry viii). Pigghe, on the other hand, did not follow, and launched himself into an extended weather forecast instead. In his “reformed” prognostication, Pigghe willingly neglected the pièce de résistance of traditional annual prognostications: the prediction of political particulars. Obviously, one could attribute this to his typically Ptolemaic preference for epistemic secrecy. However, other evidence suggests that Pigghe was more concerned with the problems of social secrecy. Consider that Pigghe had no qualms about analyzing horoscopes for the high and mighty in private. When Pope Adrian vi invited him to become his secret chamberlain in Rome (1522), Pigghe continued to cast occasional horoscopes for friends like Jerome Aleander (1480–1542).14 Also consider that Pig10 The other significators which Laet used for his prognostication for 1519 are enumerated in the prologue to his text. First, he mentions the great orb that started with the Flood conjunction. As a central point of reference, Laet mentions the solar eclipse in June 1518, followed by profections and directions on (presumably the great orbs starting with) previous great, middle, and small conjunctions, as well as significant current planetary positions such as the quartile aspect between Saturn and Jupiter from February to August 1519, solstices, equinoxes, and monthly syzygies, as well as a solar eclipse in October, and lunar eclipse in November 1519. 11 Pigghe’s association of Laet with conjunctionist astrology was undoubtedly reinforced by the fact that Laet referred to the great conjunction of 3381 bc as early as 1506. See Laet, Pronosticatie (1506). 12 Pigghe, Astrologiae defensio, fols. 26r/v. 13 Laet, Pronosticatie (1519), fol. a4r. 14 See Jedin, Studien, to be supplemented with the biography in: Craenevelt, Literae, pp. 256–260.

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ghe expressed particular concerns with the impact of astrological predictions while addressing his courtly patrons: [True astrology] witnesses how the souls of simple men are severely shaken by these matters. Many men (as I have witnessed) are even deterred from undertaking things, or from some useful business to which they were resolved. Astrology says that it pains her to see how poor mortals are tormented by such needless fear in her name.15

Previous chapters showed that Pigghe’s concerns were well founded. The impact of an astrological prognostication was strongly determined by parameters like the specificity of predictions, local sociopolitical circumstances, and material transmission. The printing age was marked by the increasing speed with which the interrelations between these parameters were transformed, and by a corresponding increase in the number of “critical episodes” for the astrological profession. All this played a quintessential role in the genesis of Giovanni Pico’s remarkable Disputations (1494), written only after the printed 1484 predictions had reached a broad Italian audience. Similar concerns dominated Louvain astrology when the university refused to be publicly associated with the printed prognostications of Joannes Laet in 1478. The 1524 debates only erupted after the predicted Flood was publicized in the popular prognostications of Luca Gaurico and Gaspar Laet. Already in the late 1470s, Joannes Laet controlled this impact through a careful alternation of openness and secrecy. His prognostications aimed at satisfying public interest, while avoiding excessive specificity. This strategy was essential to safeguard the prestige of both patron and practitioner. Astrological reformers like Pigghe implemented a radically different solution to the problem of impact. Instead of alternating between openness and secrecy in the public prediction of political particulars, Pigghe privatized political particulars completely. Astrological reformers subjected dangerously specific predictions to total (social) secrecy, and legitimated this move by an appeal to the Ptolemaic ideal of epistemic secrecy. Of course, this left a vacuum in the public space of court patronage. Into this vacuum stepped the public practice of astrological reform itself. Like traditional annual prognostications, astrological reform was a practice. It adjusted various ideas, things, and data in order to make predictions of the future. Reformed practice distinguished 15

Pigghe, Astrologiae defensio, fol. 14r.

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itself, however, by an insistence on the problematic nature of the astrological tradition. In the public space, astrological reformers emphasized the investigation of fundamental concepts in astrological physics and theoretical astronomy, the development of more precise instruments, or the gathering and evaluation of data sets. The grand framework of these activities was a reconstruction of astrological practice that emphasized the close ties between “theory” and “practice.” Astrological reform aimed at “disciplining” the prognosticators in more than one sense. A similar reading can be applied to our other courtly reformer, Cornelius Scepper. After the 1524 conjunctions, Scepper was recruited by Charles v (1526), and rapidly became one of Europe’s foremost diplomats. Although Scepper did not resume his astrological role in public, there is ample evidence that he did not renounce the art in private. In 1531, Scepper provided Philipp Melanchthon with astrological advice on the political future of his previous employer, Christian ii.16 This seems to have been a standing habit of Scepper’s, since Melanchthon privately remarked that he often got it wrong.17 On 29 June 1532, Melanchthon sent Joachim Camerarius the genitures of Charles v and his brother Ferdinand, claiming that they agreed with a collection of horoscopes that Scepper had once owned.18 When Scepper arrived in Istanbul on a diplomatic mission in the summer of 1533, he was specifically targeted with local prophecies.19 Scepper also engaged in astrological self-analysis. In a letter to his friend Dantiscus, dated 12 June 1546, he wrote: I will now return to that letter of yours in which you advise me to carefully consider the fact that, thanks to my stepdaughter, I have now become a grandfather. [This occurred] against the will of my astrology, which predicted an earlier death among the cheerful chatter of friends. Would I then commend Albumasar and other writers of that sort? You also wish to know whether I have abandoned those calculations with which I often occupied myself.20 16

Warburg, “Heidnisch-antike Weissagung,” pp. 269–272. Ibid., p. 271: “Schepperus negat rediturum esse. Sed me non movet Schepperus. Sepe enim fallitur.” 18 Ibid., pp. 272–273: “Mitto tibi geneses eorum, quorum petiisti, ac alterius quidem et altera circumfertur, sed Gauricus affirmabat hanc veram esse, si recte memini. Mars erat in fovea, in eo catalogo, quem Cornelius Scepperus habebat. Neque hic multo aliter se habet.” 19 Finlay, “Prophecy and Politics in Istanbul.” 20 Edited in Waterbolk, “The ‘Reception’ of Copernicus,” p. 242: “Redibo ad epistulam tuam qua me admones uti perpendam me ex privigna avum effectum 17

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Scepper replied that he had. Referring to his youthful Assertio fidei (1523), he assured Dantiscus that his interest in astrology was spurred by Christian ii, who implored him to continue his astrological activity. Scepper claimed not even to remember the basic rules now.21 But the rest of the letter tells a different story: Moreover, I later learned from my mother, who is still alive, that the geniture which portended an earlier death, and which was thought to be mine since it came from me, was not my real birth chart. It seems that I am one year younger than I thought at the time. I have found this confirmed in the archives of my guardian’s books.22

Life expectancy was traditionally calculated with the Ptolemaic method of prorogation. When this method did not yield the expected results, Scepper blamed his data, but not the technique as such. His private belief in astrological practice was undiminished. In retrospect, Scepper’s Assertio fidei can also be seen to embody the advent of a distinction between the public practice of reform and private astrological consulting. Although it did not specify the parts of the astrological tradition that could be withheld, Scepper’s Assertio publicly established his trustworthiness as a private astrological practitioner. Reinforced by philosophy, his faith enabled him to overcome the astrological dangers of demonic delusion.23

3. The nature of astrological reform The central accomplishment of these astrological reformers was twofold. First, they created a new public role for astrological practitioners. This role focused less on the practice of predicting, than on the practice of astrological reform. A central concern of astrological repraeter matheseos mee voluntatem que celeriorem vite exitum portendebat eumque inter letos convivarum strepitus, proindeque valere iubeam Albumazarem ceterosque id genus scriptores, scireque desideras an a talibus calculis quibus subinde occupari solebam desierim.” 21 Waterbolk, “The ‘Reception’ of Copernicus,” p. 242. 22 Ibid., p. 242: “Caeterum genesis illa que celeriorem vite exitum portendebat, quam a me esse mea tunc putabatur, didici tamen postea ex matre que adhuc superstes est, veram illam meam non fuisse, meque uno anno quam tum credebam, iuniorem. Id quod ex archivis tutelarium librorum etiam deprehendi.” Archivum tutelarium librorum probably refers to the documents of the so-called “weeskamer,” although these usually do not contain birth data. 23 In the dedicatory letter preceding his Arithmetica, Roussel also links philosophical truth with the practice of prudentia. See the edition of this letter in Lefèvre d’Etaples, The Prefatory Epistles, ed. Rice, p. 428.

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form was the reconstruction of links between astrological theory and practice (i.e., making astrological practice more “philosophical”). Such reconstruction was often carried out in public, thus providing a distinct advantage in an astrological market that was characterized by rowdy competition and open conflict. The 1478 censorship of Joannes Laet’s printed predictions had indeed become a thing of the past. Astrological reform meant much more than a humanist exchange of one set of astrological rules for another, more ancient set. Instead, it defended a fundamental change in the definition of astrological practice. Both Pigghe and Scepper, for instance, publicly advertised themselves as “philosophers.” This was a clear reference to their investigation of the links between astrological practice on the one hand, and Ptolemaic astrological physics (Pigghe) or philosophical number-theory (Scepper) on the other. In second place, astrological reformers managed to bring political particulars back to the realm of private consulting, where they had been before the advent of annual prognostications. They were able to do so because public practice of astrological reform covered the full range of traditional astrological practice (both “theory” and “practice”), thus satisfying the needs of astrological patronage. The dominant narrative of astrological patronage relations was expanded from public prediction to public reform. Public astrological practice previously supported the patron’s power through his access to correct predictions. Patrons were now invited to demonstrate their power by supporting the practice of astrological reform. This is exactly why court practitioners preferred to present their reformist challenges to urban prognosticators in print. Astrological reformers could afford not to place particular predictions at the center stage of their public practice, because their public practice of astrological reform was a token of expertise in itself. It was a sign of the astrological reformer’s (and, by implication, his patron’s) access to correct private predictions.

4. Meanwhile, among the prognosticators Urban prognosticators, however, were in hot pursuit of these very same strategies. Once again, the Laet family provides us with an interesting example. As the expected Flood drew nearer, Gaspar Laet gradually adopted the astrological and literary conventions of his courtly critics. In

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the prognostication for 1524, he emphasized a solar eclipse on 25 August 1523, rather than the planetary conjunctions of February 1524. Although his predictions still sounded ominous, he downplayed the importance of the conjunctions because “no constellation can be so universal that it encompasses the entire world.”24 Ptolemaic models also informed Laet’s seasonal predictions.25 Predictions for individual crops, using the Arabic doctrine of Lots, had disappeared. By 1526, Gaspar Laet had modified his techniques to such an extent that Albert Pigghe could have written this prognostication. At least some urban practitioners were emulating the astrological reform that court astrologers had preached before 1524. At the same time, they adopted its rhetoric against their own competitors, as the work of Gaspar Laet’s son shows.26 After a few initial trials, Gaspar Jr. single-handedly continued the family tradition of annual prognostications after 1533.27 In a 1529/30 pamphlet, he exposed several technical errors in the prognostications for 1530 by his Antwerp competitors.28 At least one of them, the Antwerp printer, physician and astrologer Jean Thibault, published an Apology against these al-

24 Laet, Pronosticum (1523), fol. 1r: “Nulla enim constellatio adeo universalis esse posset quod totum mundum comprehendat.” 25 Ibid., fol. 3v: “Hyems duplex supputationis initium habet. unum temporis, quod capit inicium ab introitu solis in primum punctum capricorni. Et durat usque ad initium introitus solis in arietem. Aliud est principium qualitatum hoc in tempore contingentium. Et illud principium hyemis erit anno praesenti.” 26 Gaspar the Elder sent three sons to Louvain University between 1510 and 1514. See Reusens et al. (eds.), Matricule, vol. 3, p. 388, nr. 195; vol. 3, p. 388, nr. 202; vol. 3, p. 496, nr. 343. Two of them, Gaspar Jr. and Ptolemeus, continued their medical studies at Montpellier, where they matriculated in 1517 and 1520 respectively. See Matricule de l’Université de Médecine de Montpellier, ed. Gouron, nrs. 536 and 701 (pp. 32 and 41). Gaspar Jr. mentions his medical studies at Montpellier in his Correctorie (1530/1), fol. a3r: “Ende seer lichtelic sonder arbeyt, door die tafelen van emanuel Hebreus in suis tabulis alarum, die welcke hi calculeerde in Tarascon by Mompelliers, die ic daer met groter diligentie hebbe vercreghen als ic tot Mompelliers was studerende.” J.-J. Thonissen, “De Laet (Gaspard)” in: bn, vol. 5, pp. 269–270, claims that Gaspar Jr. obtained the doctorate in medicine at Louvain on 25 May 1512, which is very unlikely in light of the other evidence. In my opinion, it was Gaspar the Elder who was granted the md. The Antwerp town records mentioned him as sworn “licentiaet in medecynen” between 1505 and 1509. See Van Schevensteen, “Naamlijsten,” p. 141. 27 Based on the unpublished list of Laet-prognostications of Dr. E. Cockx-Indestege. 28 Gaspar Laet Jr., Correctorie. The subsequent publication of Thibault’s Apologie is referred to in the title of Laet’s later Defensie Responsijf. It is possible that Thibault’s Apology was included in his lost prognostication for 1530 (nk 01151).

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legations.29 Although this text is lost, we can reconstruct its contents from Laet’s subsequent Defensie Responsijf (c. 1530–1531). In his initial Correctorie, Laet Jr. debunked the work of his competitors on both astrological and astronomical grounds.30 Astrologically, he insisted on the dangers of preferring Albumasar over Ptolemy.31 In the astronomical domain, he blamed his competitors for their incapacity to correct printing errors in the common ephemerides.32 Thibault’s Apology retorted that Laet’s astrological advice for purging and bloodletting was unreliable.33 His claim rested on a strict interpretation of Regiomontanus’ advice to avoid venesection when the Moon is within 13° of a maleficent aspect to the Sun, Mars, or Saturn. In his Defensie Responsijf, Laet simply overruled Regiomontanus with the ancient authorities of Firmicus Maternus, Hermes, and Ptolemy, whom he justified on optical, kinematical, and physical grounds.34 He also degraded Thibault’s work by comparing it to popular works like the Shepherd’s Calendar.35 Both exhibited a similar lack of order, superimposed one signification upon another, and uncritically anthropomorphized the heavens.36 29 At least three Antwerp prognostications by Thibault, for 1526, 1527 and 1531, are known (nk 2006, 3939 and 2007). General bio-bibliographic references to Thibault can be found in Prost, Les sciences et les arts occultes, vol. 2, pp. 248–250 and 537–538. A new study of the tract which Cornelius Agrippa ab Nettesheym wrote in 1530 to defend Thibault against the Antwerp physicians, would be very welcome. Agrippa’s defence of Thibault is structured around his identification of Thibault as an empiricist physician. This agrees well with the (critical) picture which Gaspar Laet Jr. paints of him. See Prost, Les sciences et les arts occultes, ii:241–244 for a review of the content of Agrippa’s defence. 30 Laet Jr., Correctorie, fol. a1r. 31 Ibid., fol. a4r: “Noch beliecht hi Ptholomeum scrivende datmen soude maken figuren vanden hemel, als die Sonne comt in deerste mi. van Aries, in Libra &c. ende considereren dan die aspectus ende oppositien dwelc Ptholomeus niet en scrijft in quadripartito, want hi hem niet wel en verstaet, mer Albumasar die vele erroren scrijft in die Astronomie is dat segghende.” 32 Laet Jr. lists these errors on fols. a1v-a2r of his Correctorie. 33 Laet Jr., Defensie Responsijf, fol. a1r: “Deerste deel is declarerende hoe alle mijn laetdagen die hi wilt reprehenderen int iaer van xxix ende van xxx goet ende bequaem sijn om laten.” 34 Ibid., fol. a2r. 35 Bernard Capp describes the Shepherd’s Calendar as “a large perpetual calendar which contained religious, moral and astrological advice, and rules for preserving health” (Capp, Astrology & the Popular Press, p. 27). 36 Laet Jr., Defensie Responsijf, fol. a4r: “Ende om dit te bewisen, soe beghint hi inden ierste te twalen vander materie, niet houdende eenighe ordene, maer vallende is vanden os op den ezel nu scrivende van die xij teekenen des hemels, ende van die vij planeten, ende van die xij domus, ende noch schandelick van groote scheten, ende vanden ghelijckenisse des menschen tseghen den hemel, het welck al staet

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The effect of Gaspar Laet’s changing language and methodology was significantly small. In the preface to his prognostication for 1543, Laet anticipated criticism about his treatment of a Saturn-Mars conjunction in late 1543 and early 1544. This critique was threefold. First, the conjunction of a cold and a hot planet would temper its overall effect. Second, the relative size of Saturn and Mars was too small to have significant results. Third, Saturn and Mars had no manifest specific impact on the Low Countries. Laet ascribed these arguments to “certain astronomers in past years,” who “fabricated [them] from Giovanni Pico.”37 His subsequent reference to the 1524 debates suggests a riposte to his father’s opponent Albert Pigghe.38 Gaspar Laet Jr. was obviously perfectly aware of the problematic nature of conjunctionism. Still, he neglected it in favor of a set of particular predictions that could not fail to attract considerable attention. To many people, the later work of the Laet family must have represented the best of both worlds, taking up crucial elements of reformist practice, and fusing these with public particular predictions. This provides us with a background against which to understand the staggeringly broad range of interests that flourished among Louvain mathematicians after 1524: cartography, instrument making, Copernican astronomy, weather observations, the study of ancient encyclopedists, new natural philosophies, and new techniques of astrological prediction. I argue that each of these activities contributed to a single overarching project: the further elaboration of astrological reform. That is the central message of the next four chapters.

beschreven bycans inden Schaepherders Kalengier, ende in duytsche ende walsche historien, die de vrouwen dagelicx sijn lesende.” 37 Ibid., fol. 1r: “(…) met meer andere redene gefabriceert uut Joanne Pico (…).” 38 Gaspar Laet [Jr], Pronosticatie (1542/3), fol. 1r: “Niet teghenstaende dat die sommige astronomijns hebben willen sustineren in voerleden iaren dat die coniunctie oft aspecten vanden oppersten planeten, seer luttel souden moghen influeren ende opereren (…)”; Ibidem, fol. 1v: “Met deeser gelijcker argumenten wouden sommige astronomijns te niet doen ende ons alleen versekeren van die groete wateringen ende opvloeijnge, die ons geintimeert waren van allen die coniunctien int iaer van xxiiij voerleden gesciet, (…).”

CHAPTER SIX

COPERNICAN ASTRONOMY AND LOUVAIN ASTROLOGY

1. Introduction The summer of 1541 proved to be an exciting time for Gemma Frisius. Cornelius Scepper provided him with a copy of Rheticus’ Narratio prima (1540), the text that announced the basic tenets of Copernican astronomy to European stargazers, in the first half of July. On 20 July, Gemma enthusiastically wrote Dantiscus about his reading of the Narratio prima: I could enumerate many things that never satisfied me. Take, for instance, the motion of Mars, which I often found to differ by three ecliptic degrees from even the most exact calculation with astronomical tables. Or the size of the moon, which does not vary as much before our eyes as the most reputable authors of this art maintain. The length of the year has never been determined in perfect accordance with the truth. I will refrain from saying anything about the motion of the firmament and the apogees, which, not even exhibiting a slight resemblance to the truth, is ridiculed by all. I also leave aside several other things on the longitude and latitude of nearly all the fixed stars, for fear of annoying your Honour in an even more discourteous manner. If that author would mend and buttress these matters (which I expect, judging by the proemium which he sent forth), wouldn’t this amount to giving us a new earth, a new heaven and a new world?1

1 de 429: Dantiscus, Correspondence, ed. De Vocht, pp. 344–347. A French translation can be found in Rheticus, Narratio prima, ed. Hugonnard-Roche et al., pp. 248– 249. This letter was published, with a number of errors, in Van Ortroy, Bio-bibliographie, pp. 408–410. The following quote is transcribed directly from the original at Linköping Stiftsbibliothek, mss. Br 19, nr. 55: “Ego sane multa possem enumerare, quae nunquam mihi satisfacere potuerunt. Quale est, quod Martis motum saepe a calculo, vel exactissimo secundum tabulas, tribus signiferi partibus abesse observaverim. Quod Lunae magnitudo non tantum varietur ad nostrum conspectum, quantum notant gravissimi hujus artis auctores. Quod anni quantitas nunquam inventa sit exacte conformis veritati. Nihil nunc dicam de motu Firmamenti et Apogiorum, qui ut ne umbram quidem habuit veritatis, ita omnibus ridendus approbatur. Omitto

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Gemma expected Copernicus to solve five specific problems: the angular position of Mars, the apparent size of the moon, the length of the year, the precessional motion of the fixed stars and the apogees, and the position of the fixed stars. This astronomical critique was not uncommon among European astronomers of the sixteenth century. The second problem was highlighted in Regiomontanus’ popular Epitome of the Almagest, while the debates on calendar reform naturally emphasized the third one.2 The length of the year was also dependent upon the fourth problem, a correct determination of precession. Finally, we know that Copernicus made private comments about the Alfonsine predictions of Mars’ position by 1504.3 This chapter does not discuss the historical antecedents of Gemma’s complaint. Instead, it focuses on the immediate context of Gemma’s problematic, in order to circumvent a traditional pitfall for students of early Copernican astronomy. It is tempting to assume that Gemma Frisius’ mind contained one single conception of Copernican astronomy that can be puzzled together from his preserved writings. If such a unique conception truly existed, I have been unable to identify it. Instead, it seems more rewarding to start out from the overwhelming evidence that sixteenth-century discussion of Copernican astronomy was intimately shaped by the various interests that it seemed to serve.4 On this assumption, the present chapter argues that Gemma Frisius’ attitude towards Copernican astronomy reflects the new circumstances of elite astrological practice. Section 2 shows how a series of planetary conjunctions, surrounding the Saturn-Jupiter conjunction of September 1544, stimulated Gemma’s private interest

etjam plura alia de omnium fere stellarum longitudine et latitudine, ne D. T. Revme obstrepam incivilius. Haec si reddiderit auctor ille sarta et tecta (id quod maxime animus praesagit ex eo proëmio quod praemisit), nonne hoc est novam dare terram, novum coelum ac novum mundum.” I thank Dr. Mathias von Wachenfeldt, librarian at Linköping, for his kind assistance in providing me with copies of the original text. 2 Regiomontanus, Epytoma (…) in almagestum ptolemaei (1496), chapter v.22, fol. f6r: “Sed mirum est, quod in quadratura luna in opposito augis epicycli existente non tanta appareat, cum tamen si integra luceret, quadrupla oportet apparere ad magnitudinem suam, quam apparet in oppositione, cum fuerit in auge epicycli.” These problems were also mentioned in the Narratio prima. See Copernicus/Rheticus, Three Copernican Treatises, trans. Rosen, pp. 127 and 133–134. 3 See Gingerich, Eye of Heaven, pp. 170–171; Kremer, “Bernard Walther’s Astronomical Observations,” p. 185. 4 See various classic papers by Robert S. Westman. Westman, “The Melanchthon Circle”; Westman, “The Astronomer’s Role in the 16th Century”; Westman, “Proof, poetics, and patronage.”

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in Copernican astronomy. Twenty years after the 1524 debates, the local problematic of conjunctionist prognostications was still tangible. Significantly, these astrological concerns were mostly dissimulated in the subsequent publication of Gemma’s results, which promoted On the Revolutions as a work of astronomical reform. However, such dissimulation was differentiated in accordance with its intended audience. More precisely, Gemma seems to have promoted a local subtext, which connected astronomical reform and astrological power, around the court of Charles v (section 3). This confirms that the new circumstances of astrological practice revolved around a clever exploitation of the (local) boundaries between public and private practice. Exactly the opposite development occurred with respect to astrological theory. Section 4 focuses on Gemma Frisius’ interest in Copernican astronomy as a body of reformed theoretical astronomy (i.e., the cosmological models that explain and underlie the practice of predictions). Gemma’s didactic familia provided a space where these theoretical concerns could be discussed in relative independence from the need for short-term authentication of a patron’s power. This led to a remarkable interest in the systemic features of Copernican astronomy that was motivated by their relevance to Pico’s astrological critique.

2. Copernican astronomy and private astrological practice Chapter 5 argued for the central role of cosmographical didacticism in the relation between Gemma Frisius and his Polish patron Joannes Dantiscus. Both men also shared an active interest in astronomical reform. It is very likely that Dantiscus informed his Louvain protégé of Copernicus’ advances as early as 1531. Interconnections between astronomical and astrological reform became explicit as soon as the Louvain circle began to discuss Copernicus’ work. On 15 July 1541, Cornelius Scepper informed Dantiscus that he had received a copy of the Narratio prima in Brussels, and referred to its author Rheticus as a “young astrologer [my italics] and mathematician.”5 Five days later, Gemma exclaimed, in his afore-

5

de 426: Dantiscus, Correspondence, ed. De Vocht, p. 341: “Juvenis astrologus et mathematicus.”

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mentioned report on the Narratio Prima: “How many errors, covers and labyrinths, how many puzzles, more difficult than those of the Sphinx, had enveloped our astrology.”6 This pattern is confirmed in Gemma’s De radio astronomico et geometrico (1545).7 This treatise was a further addition to Gemma’s impressive bibliography on cosmographical teaching. It described an astronomical instrument, the cross staff, which Gemma had improved for observational uses.8 The cross staff could be implemented for cosmographical purposes, and in fact appeared in every edition of Gemma’s popular Cosmographia (see chapter 5). Likewise, Gemma’s preface emphasized its relevance to geography, optics, geometry, and astronomy. Focusing on the astronomical content of De radio astronomico, we encounter a strong emphasis on contemporary astronomical reform. Gemma’s demonstrations of the instrument’s use were frequently presented as either new observational advances, or confirmations of Copernican astronomy. A fine example is Gemma’s use of the cross staff to verify the longitude and latitude of Mars, which he linked to a critique of the accuracy of Alfonsine planetary theory.9 The position of Mars was observed on 31 October 1544 at 7 pm. From its position with respect to the fixed stars Cap γ and Cap δ, Gemma concluded that the longitude of the fiery planet was 316;20°, and its latitude -1;30°.10 Recomputation of Mars’ position from the 6 de 429: Dantiscus, Correspondence, ed. De Vocht, pp. 344–347 (my italics). The following quote is transcribed directly from the original at Linköping Stiftsbibliothek, mss. Br 19, nr. 55: “Quot enim erroribus, involucris, labyrinthis, quot denique aenigmatibus plus quam Sphingicis involutam habuimus nostram Astrologiam.” As before, I interpret this use of “astrology” in the context of traditional academic astrology teaching. 7 This treatise contains Gemma Frisius’ observation report for the solar eclipse of 9 June 1545, which constitutes our terminus post quem for its date of publication (see fol. 25v). On the history of the cross staff, see Roche, “The radius astronomicus in England”; Mörzer Bruyns, The Cross-Staff. History and Development. Although there is not a great deal of literature on Gemma Frisius’ De radio astronomico, one should consult: Barker, “The Optical Theory of Comets from Apian to Kepler”; Goldstein, “Remarks on Gemma Frisius’ De Radio Astronomico et Geometrico.” 8 See Goldstein, “Remarks on Gemma Frisius’ De Radio Astronomico et Geometrico,” pp. 169–171. 9 See the diagrams in Gingerich, The Eye of Heaven, pp. 169, 195, 233. 10 Gemma Frisius, De radio astronomico, fols. 33v-34v: “Pridie Kalend. Novemb. ho. 7 pomeridiana, anno 1544 quo tempore haec conscripsimus, visa est Martis stella haud longe supra duas stellas fulgentiores, quae sunt in cauda constellationis Capricorni. Distabat ab occidentaliori 57 minutis tantum, ab orientaliori 1 gradu, & 6 minutis. Acceptis ergo per circinum distantiis inventis ad gradus eclipticae, duco duas circinationes (…) Visusque est Mars in decima sexta parte Aquarii secundum viam eclipticam, cum triente, & latitudo eius austrina apparuit unius gradus & semissis.”

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Alfonsine tables results in a predicted longitude of 318;27°.11 This agrees rather well with the error in Joannes Stöffler’s Ephemerides for the period 1532–1552, which was still the standard tool in the 1540s.12 Stöffler predicted Mars’ longitude as 319;3° on 1 November 1544.13 From the Tuckerman tables, we learn that the true observable longitude would have been 316;21°,14 whereas the recomputation of Mars’ longitude with Copernicus’ On the Revolutions yields 315;53°.15 From his observational test, Gemma concluded that: We have observed Mars on several other occasions, and sometimes found the planet to stand more than three degrees apart from the common computation of the Ephemerides. It will be worthwhile to correct such intolerable errors, which come forth from the Alfonsine computation, through Ptolemy’s methods, as Copernicus has recently done with an immense effort.16

In a letter that Gemma wrote to his pupil Stadius on 28 February 1555, he added that the Alfonsine problems became particularly apparent as one predicted conjunctions of superior planets.17 Closer inspection of the context of Gemma’s observational reports imparts new meaning to this last statement. More specifically, it suggests that

11 For computational convenience, I have disregarded the equation of time in the case of the Alfonsine computation, and both this equation and the difference in longitude between Louvain and Cracow for the Copernican result. In the case of Mars, this simplification changes the results with no more than a few minutes, which is sufficiently precise for our present purposes. 12 Stöffler, Ephemeridum opus (1533). 13 Stöffler, Ephemeridum opus, fol. Cc5r. Stöffler seems to have followed the Alfonsine convention of using astronomical days which start at noon on the previous calendar-day. By this convention, Gemma observed Mars on 1 November at 7h. 14 Tuckerman, Planetary Positions, p. 790. 15 I thank Cindy Lammens (Gent University) for her corrections of a previous version of this argument. 16 Gemma Frisius, De radio astronomico, fol. 34v: “Atque si tabulae communes in Martis loco plus duobus gradibus aberrant, observavimus eundem quoque Martem aliis variis temporibus, & aliquando a calculo communi Ephemeridum invenimus illum abesse plus tribus gradibus. Hos ergo errores intolerabiles, qui ex Alphonsino calculo nobis pullulant, licebit secundum artificium Ptolomaei corrigere, ut proxime fecit immenso labore Copernicus.” 17 See Stadius, Ephemerides (1585), p. 2: “Sic hisce nostris oculis congressus Saturni & Martis aspeximus, per sex & amplius dies antevertere, in Stofloeri Ephemeridibus annotatos. Et quantum in Martis motu tabulae Alphonsinae (ex quibus hactenus Ephemerides collectae sunt) aberrent, docuimus, demonstravimusque in libello nostro de Radio. (…) Omitto intolerabiles in motu Mercurij errores.” This letter was printed in every edition of Stadius’ popular Ephemerides, which was based on Copernican parameters, and can be found on pp. 1–3 of the Ephemerides (1585).

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astrological concerns initially propelled these observational tests.18 Here are ten Louvain observations that Gemma reported in De radio astronomico: 1. Comet, 1532 and July 1533 2. Conjunction of moon and the star Spica, 12 June 1540 3. Lunar diameter, 15 December 1542 4. Solar eclipse, 24 January 1544 5. Solar altitude, 24 January 1544 6. Solar altitude, 24 October 1544 7. Solar diameter, 27 October 1544 8. Lunar diameter, 27 October 1544 9. Position of Mars, 31 October 1544 10. Solar eclipse, 9 June 1545 Out of ten observations, no less than four were made in the last week of October 1544. Stöffler’s Ephemerides predicted a conjunction of Saturn and Mercury on the 25th, and one of Jupiter and Mercury on the 28th.19 We know that the latter conjunction took place on 27 October 1544 around 1 pm on the meridian of Louvain.20 For the time of conjunction, the Alfonsine tables predict a longitude of 247;10° for Mercury.21 In reality, it was 245;55°, a difference of 1;15° (Tuckerman). Jupiter’s longitude was then 244;54° according to the Alfonsine tables, a difference of -1° with the real value. More importantly, the Alfonsine results imply that the conjunction occurred well over a day before it really did. A careful observer like Gemma Frisius would have noticed that the Alfonsine tables got it quite wrong in the nights before and after the predicted conjunction of Jupiter and Mercury. The problems with Jupiter and Saturn would have been perceived more dramatically one month beforehand, as the two planets conjoined, for the first time in twenty years, in the watery sign of Scorpio. Johann Stöffler had predicted this conjunction for 25 Septem-

18 Richard Kremer suggests a similar motivation for Bernard Walther’s increased observational activity in the period 1503–1504 (around the time of a Saturn-Jupiter conjunction). See Kremer, “Bernard Walther’s Astronomical Observations,” pp. 185– 186. 19 Mercury was approaching its maximum elongation from the sun at the time, making the conjunction with Jupiter visible. 20 Tuckerman, Planetary Tables, p. 790. 21 Once again, I have disregarded the equation of time, which does not affect my comparisons.

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ber.22 This time, he had wisely abstained from the interpretive comments that triggered the panic of 1524. Observers would have seen Saturn and Jupiter conjoined in the night of 17/18 September. By the night of 24/25 September, the difference in longitude amounted to almost 0;37°. The Alfonsine tables predicted Saturn’s longitude at noon on 17 September to be 237;13°, and that of Jupiter as 236;43°, a difference of 0;30°. The difference with the true positions is 0;46° and 1;18° respectively (Tuckerman). There is no hard evidence that Gemma Frisius observed the September 1544 conjunction. But he did observe Mars on 31 October 1544, for which day Stöffler had predicted a maleficent quartile aspect with the sun.23 The increasing frequency of his observations in the last week of October 1544 is most probably related to a temporary wealth of phenomena that typically attracted considerable attention in judicial astrology.24 We may assume that an interest in the prediction of planetary conjunctions propelled Gemma’s observations in the fall of 1544. In short, popular astrological practices formed an essential stimulus for Gemma’s initial interaction with Copernican astronomy.25

3. Patronage, politics, and astrological activity De radio astronomico thus provides interesting testimony to the genesis of Gemma’s interests in Copernican astronomy. These interests did not remain confined to the realm of his private astrological practice. Gemma dedicated De radio astronomico to Pedro Fernandez de Cordoba, Count of Feria (1518–1552), on 1 February 1545. As a patron, Fernandez de Cordoba was an excellent choice, despite his early death. On 11 December 1545 (one day after the winter solstice), the young Count was received as Knight of the Order of the Golden Fleece in Utrecht.26 Since its foundation in 1430, the Order had gradually ceased to attach any practical significance to its crusading ideals. Nevertheless, its membership still carried great respect under Charles v as a ritual 22

Stöffler, Ephemeridum opus, fol. Cc3r. Ibid., fol. Cc5r. 24 See Gaspar Laet [Jr], Pronosticatie, ([1542/3]). 25 For a preliminary version of Robert Westman’s argument that similar concerns shaped Copernicus’ interest in astronomical reform, see Westman, “Copernicus and the Prognosticators.” 26 See Alós y de Dou, “El Toisón de Oro”; Fagel, De Hispano-Vlaamse Wereld, p. 340. 23

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intermediary between the old Burgundian feudal order and the new Spanish monarchical state.27 At least one of Gemma’s Louvain colleagues, Cornelius Valerius, chronicled this significance on various occasions between 1540 and 1555, including a versified gratulatio on the Order’s 1545 chapter.28 Gemma carefully modelled his dedication to Fernandez de Cordoba around the theme of contemporary astronomical reform.29 Does this allow us to infer that Gemma’s patron shared his underlying astrological interests? The next two examples will show that the answer is “yes.” They simultaneously remind us, however, that astrological patronage also entailed a strict separation of public and private practice. De radio astronomico was a tale of the patron’s power, as illustrated in his control over the practices of reform (handling a cross staff, for instance). It was not intended to relate the detailed results of these practices. This is exactly why Gemma’s dedication emphasized his patron’s worship of the Muses while participating in the Emperor’s military campaigns against Duke Charles of Guelre (1542–1543).30 Even the horrid siege of Düren, or the wintercamps after the treaty of Venlo (September 1543), had not detracted the count from the study of the bonae artes, Gemma added. Once again, we find Louvain practitioners promoting the image of the nobleman who combines political and military responsibilities with a private study of the mathematical arts (see the examples of Gaditano or Mercator in chapter 5). It was against this background that Gemma Frisius cultivated his fascinating interaction between private astrological practice and public astrological patronage. 3.1. Politics and the position of the fixed stars Advances in the coordinates of the fixed stars were eagerly awaited at Louvain. Following the report of an observation of the star Arcturus that confirmed Copernicus’ data, Gemma wrote that:

27

See L’ordre de la Toison d’or, eds. Cockshaw and Van den Bergen-Pantens. See Tournoy, “De Orde van het Gulden Vlies in de Latijnse literatuur (15de17de eeuw).” 29 See Gemma Frisius, De radio astronomico, fols. a3r-a5v. 30 Gemma Frisius, De radio astronomico, fol. 5r: “Verum enimvero cum hic te Princeps Illustrissimus facile inter primos declaraveris, qui inter medias armorum strepitus, inter cruentas inimicorum strages, non desiisti Musas a hoc Martis certamine alienissimas, colere: (…)” 28

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This, in my opinion, is where Alfonso’s collaborators failed him most, so as to prevent him from allowing any calculation: that they have not used their own observations, but rather those of Ptolemy and others who came after him (each assigning him different motions), and have tried to establish the true motions of the stars by steering a middle course.31

This did not imply that all problems were now resolved. It is well known that Copernicus did not build his star catalogue on original observations, relying on an Arabo-Latin translation of Ptolemy’s Almagest or the derivatives in Giorgio Valla’s De expetendis et fugiendis rebus and the printed Alfonsine tables instead.32 Gemma seems to have been aware of this, since he advocated the systematic empirical verification of star positions in De radio astronomico (1546).33 His method was akin to the famous cosmographical triangulation method of his De locorum describendorum ratione (1533). Replacing the sheet of paper in terrestrial cartography with a blank globe, and the horizontally placed astrolabe with a cross staff, Gemma proposed to transfer the angular distances between stars to the surface of the globe, until the entire starry vault was depicted. By means of a few additional observations, the great circles could then be inserted on the globe.34 This method contributed to Gemma’s reputation among other admirers of Copernicus. In the preface to his Ephemerides novae for 31 Gemma Frisius, De astrolabo, fol. 76r: “Ac mihi sane videtur Alfonso nihil aliud prorsus defuisse quo minus omnem calculum absolverit: nisi quod illi quibus id negotij dabatur non usi sint observationibus a se factis, sed potius ex Ptolomaeo aliisque sequentibus, ut eunque motus diversos adsignantibus, conati sint per mediocritatis modum constituere veros stellarum motus.” 32 For a general discussion of Copernicus’ star catalogue, see Swerdlow/Neugebauer, Mathematical Astronomy, pp. 121–123. 33 Gemma Frisius, De radio astronomico, pp. 21–23. Ibid., fols. 36r/v: “Poscit ergo ratio praescripta emendatam coeli stellati sive firmamenti descriptionem: sed nullas adhuc vidimus tabulas satis correctas, ex quibus illam perficere liceat [my italics]. Quae enim a Ptolomaeo nobis per manus traditae sunt, pluribus in locis emendatione egent, ob errores qui multitudine scriptorum, & diuturnitate temporis paulatim irrepserunt. Aliae vero ad imitationem Ptolomaei factae, sive ab Alfonso, sive ab aliis, ob easdem causas non paucos habent errores. Quamobrem hortatos cuperem Matheseos cultores, ut pro virili quisque sua huic parti honestissimae aliquando aliquam impendat operam. Nos quoque si Deus annos produxerit nobis, strenue id ipsum praestare conabimur, laborem non detrectabimus.” 34 Note that Gemma’s procedure for the construction of a celestial globe differs from the more famous one described in Ptolemy’s Almagest viii.3 (see Toomer, Ptolemy’s Almagest, pp. 404–407), which Mercator quoted as one of the sources for his own celestial globe of 1551. See Vanden Broecke, “Dee, Mercator, and Louvain Instrument Making,” p. 235.

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1551, Rheticus claimed that his master Copernicus had urged him on to observe the fixed stars.35 “And if the most learned Gemma Frisius,” Rheticus continued, “holds the opinion that this is where action is needed, I think that he, like a new Copernicus for our age, casts the foundations of this science.” Still, this is not what Gemma practiced in his own publications.36 Although we have records of original star observations in the margins of his copy of On the Revolutions, these results did not appear in his star catalogue (1553).37 Instead, he seems to have tried his hand at harmonizing discrepancies between the data in existing star catalogues. One domain where the new Copernican data were publicly put to the test was astrological consulting. New advances in this direction had been made in Girolamo Cardano’s De supplemento almanach (1538), a text that became quite influential at Louvain in the 1547 edition. In chapter 10 of this treatise, Cardano had used the fixed stars in the zenith to make political predictions for a specific era and place.38 His prime example was the star at the end of the tail of Ursa Maior (η UMa), which was in the zenith around the time of the founding of Rome. Cardano attributed the fact that the Romans subsequently became the rulers of the entire world to the Martian nature of this particular star. As precession caused it to recede from the Roman zenith, the empire was transferred first to Byzantium, then to France and finally to Germany, where the star attained the highest position in Cardano’s own time. Cardano provided the venerable four-empire theory with an astrological explanation. The nature of the fixed stars predisposed the character of peoples, while precession guided their dominion. 35 Having been unable to consult the Latin text of this preface to Rheticus’ Ephemerides, I base myself on the French translation in Rheticus, Narratio Prima, ed. Hugonnard-Roche et al., pp. 221–227. 36 First published in the Antwerp 1553-edition of Gemma’s De principiis astronomiae et cosmographiae, and also included in the Copernican Ephemerides of Gemma’s pupil Stadius (1556). See Ernalsteen, Joannes Stadius, pp. 29–35. 37 In Gemma’s annotations to the constellation of Gemini, he writes that “the 21st star of Taurus (β Tau) stands 27;1° apart” from α Gem. See Copernicus, De revolutionibus, copy Leeuwarden, pbf, 399 Wk: “distat 21 Taurus 27 gr. 1 m.” Also, he finds that the distance from β Tau to the 14th star of Gemini (η Gem) is 23;40°. See Copernicus, De revolutionibus, copy Leeuwarden, pbf, 399 Wk: “ab hac ad 14 [Gemini]: 23 g. 40 m.” I thank Dr. Cindy Lammens (Gent University) for providing me with relevant excerpts from Gemma’s annotations to Copernicus’ On the Revolutions. 38 See Cardano, Opera omnia, vol. 5, pp. 584–585.

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Gemma Frisius was sympathetic to the general idea of attributing slow and universal mutations to the influence of particular fixed stars. Copernicus’ new theory of precession allowed him, however, to disagree with Cardano’s interpretation of this theory.39 Since Copernican astronomy showed that η UMa was 21° removed from the zenith at Rome around 753 bc, Cardano had erected grave astrological theorems on false fundaments. Gemma nevertheless added a chauvinistic note at the end, when he noted that η UMa was in the zenith at Louvain, Cologne, and Cracow in his own time.40 A similar re-interpretation of Cardano’s theory appeared in the Tabulae Bergenses (1560) of Gemma’s pupil Stadius. Stadius believed that the position of η UMa had made the inhabitants of the Low Countries more bellicose in his own time. But he refused to follow Cardano’s assertion that the motion of η UMa had also signified the advent of the reign of Charles v.41 This last concession assigns a crucial role to the patronage context in which Gemma and his circle worked. In the preface of De radio astronomico, Gemma raised the issue of the causes of astronomy’s rebirth. While granting that certain celestial configurations indeed influenced the human soul, Gemma refused to imply that the human will was subjected “to their reign” (illis imperiis).42 This 39 Gemma Frisius, De astrolabo, fol. 44r: “Poterimus locum stellae fixae colligere per quaslibet motuum tabulas seu canones. Dicemus autem per opportunitatem de fixarum motu aliqua, verum nunc sequar Copernici tabulas seu Canones ad inveniendum locum caudae ursae maioris ad tempus urbis Romae. Quoniam hae solae experientiae praecedentium observationum respondent.” 40 Ibid., fol. 45v: “Nostro autem tempore Cauda ursae maioris declinat a Aequinoctiali partibus 51 cum sextante. Itaque iam nobis Lovaniensibus & Coloniensibus & Cracoviensibus quotidie semel per verticem fere ducitur. Sed de his satis.” 41 Stadius, Tabulae Bergenses, pp. 193–194: “Nunc videre est, quam inconsulte Ursae maioris declinationem decrescentem (quam ille crescere opinatus est) vel transferre, vel confirmare Monarchias pronunciaverit Cardanus: Non haec tam studiose agimus, ut ipsius existimationem oppugnemus: sed ne imprudens lector autoritatem Cardani sine iudicio sequutus, in re ardua & maximi in prognosticis momenti laberetur, certe (ut me ab omni invidia liberem) bellicosos & strenuos esse, quibus est verticalis stella Benanatz sive ultima caudae Helices, fateor, & docent Atrebates, Hannonij, Eburones, Sicambri, Ubij, Geldubenses, Menapij, Brabanti, quibus proximis seculis verticalis fuit: sed tantum abest, ut in istis provincijs Monarchiam constituerit, ut illae mutuis cladibus attritae, vel Gallorum incursu afflicta, a varijs calamitatibus & populationibus magna pars aegre respirarit. Quod si ab Imperatore Carolo Quinto harum provinciarum magna ex parte Principe, Monarchiam istam, ex stellae declinatione praesagiendam, dixeris vindicatam & assertam, quae stellarum eandem in Pannoniam & Bohemiam ad Ferdinandum Serenissimum Imperatorem, nec succedente Regum maximo D. Philippo harum ditionum Principe, retraxit?” 42 Gemma Frisius, De radio astronomico, fols. a4r/v.

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statement introduced a digression on the importance of the prince’s support, which Gemma singled out as the true cause of astronomy’s rebirth. In the public realm, the patron’s support of reform projects came first, and the practical implementations of that reform second. 3.2. The prediction of eclipses In the margin of his copy of Copernicus’ On the Revolutions, Gemma mentioned two Louvain observations that confirmed the Copernican values for the solar semi-diameter: In December 1547, I often measured the diameter of the sun, for which I always found 34’. For the oblong parts of the cross-staff totaled 440, of which 4 1/3 were in between the brass pins. From this, the sine of the angle is determined to be 988, when the radius of the circle is equal to 100,000. And this was on 30 December, deriving a diameter of 33’50”, and a semidiameter of 16’55”.This squares with Copernicus. I have experienced the same thing in December 1550.43

Likewise, De radio astronomico quoted one previous observation of the sun’s diameter and two observations of the moon’s apparent semidiameter. In this treatise, Gemma consistently connected Copernicus’ solutions for the solar and lunar diameter to the correct prediction of eclipses.44 The practical nature of his concerns is clear from Gemma’s instructions for the observation of eclipses. De radio astronomico reported two solar eclipse observations, made at Louvain in 1544 and 1545. After 1524, eclipses became the main parameters of mundane astrological practice (see the Intermezzo, above). As Gemma was collecting the observational data that appeared in De radio astronomico, Gaspar Laet jr. publicized these changes in his prognostication for 1543.45 Concerning a series of four predicted eclipses in 1544, another prognosticator from Bruges wrote:

43

Original text and translation in Gingerich, An Annotated Census, p. 148. Gemma Frisius, De radio astronomico, fol. 28v: “Hac igitur observatione si frequenter usi fuissent, ii qui homocentros nobis in coelo orbes finxerunt, nunquam pro certissima experientia nobis somnia obtrusissent, ac doctrinam de eclipsium exactissimo calculo confudissent. Constat enim Solem circa solstitium aestivum perpetuo minorem apparere secundum visum, quam alio quovis anni temporae. Circa hybernum vero solstitium maiorem. Utrum vero in eccentro feratur sol, an in epicyclo, non est huius loci disserere”; ibidem: “Constat saltem motum eius ad centrum mundi inaequalem apparere, eiusque magnitudinem visam inaequalem propter distantiae variationem. Id quod ad eclipsium observationem necessarium est cognoscere.” 45 Gaspar Laet [jr.], Pronosticatie vanden iare ons heeren M.D. ende xljjj. 44

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Out of these iiii. Eclipses shalbe brought forth wonderfull maters, as we shall expresse here after. Mars shall be in the Eclyppes of the Sonne in the house of death, in Scorpio, in propria domo, gaudio proprio, & proprio triplicitate. Jupiter shalbe in proprio casu, betwene Saturne and Mars, in the eyght house of death also.46

Under these circumstances, correct prediction of eclipses became a crucial asset. An excellent example is offered by a controversy surrounding the solar eclipse of 21 August 1560. This event was eagerly discussed among contemporary prognosticators. In Antwerp alone, at least five different prognostications for 1561 announced its effects. The physician-astrologer Adrianus van Vossenholen emphasized the fact that the eclipse occurred in the house of religion when the sun was in Virgo 8°, thus creating an eschatological association with Pierre d’Ailly’s horoscope of Christ (see chapters 2 and 3).47 According to his colleague Petrus de Goorle, the eclipse signified great pestilence and putrid blood, while Nicolaus Bazelius predicted: Great bloodshed among Christians (…), every road or street will be extremely dangerous (…) hence, merchants and travelers will encounter much grief and accidents.48

Even Gemma Frisius’ son Cornelius, self-proclaimed foe of the prognosticators (see chapter 7), conceded that this eclipse would affect most of 1561.49 While practitioners agreed on the overall importance of the eclipse, there was little consensus on its exact meaning. The most problematic factor concerned the astronomical data: time, duration, and magnitude of the eclipse were used to infer the chronology and strength of its effects.50 Nicolaus Bazelius complained that the Copernican tools of Joannes Stadius (another member of Gemma Frisius’ familia) were unreliable. Although Stadius predicted maximum obscuration at 13h6m with a total duration of 1h48m, the eclipse actually started around 11h and lasted until 13h30m.51 In the dedication 46 Schuute, A pronostication for the yere (…) m.ccccc.xliiii, fol. b4r. Annual prognostications by Cornelis Schuute, printed at Antwerp, are preserved for the period 1535–1561. 47 Van Vossenhoolen, Predictio astrologica (1561), fols. a3r/v. Note that the lunar eclipse of 12 March 1560 occurred in Libra 2°, which was D’Ailly’s alternative ascendent for the horoscope of Christ. 48 De Goorle, Prognosticatie (1561), fols. a4r/v; Bazelius, Prognosticatie (1561), fol. a3r. 49 Cornelius Gemma, Ephemerides Meteorologicae (1561), fol. d7v. 50 See Ptolemy, Tetrabiblos, trans. Robbins, pp. 160–188 (chapters ii.4–ii.8). 51 Bazelius, Prognosticatie (1561), fol. a2v. For Stadius’ relevant eclipse prediction,

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of his 1561 prognostication to the Antwerp burgomaster Nicolaus Rockocx, Petrus de Goorle also exposed Stadius’ errors, “which are sometimes found to be over one and a half hour early or late.”52 Still, he found that Stadius’ astronomical results agreed quite well with the eclipse’s observed effects, and reproduced them faithfully.53 The solar eclipse of 21 August 1560 was entangled in a widespread debate among astrological prognosticators concerning the reliability of Copernican astronomy. In the course of a single prognostication, Bazelius managed to rely on both Stadius’ Copernican ephemerides (for the 1560 winter solstice) and Carello’s Alfonsine counterpart (for the vernal equinox of 1561).54 From Petrus de Goorle, we learn that prognosticators eventually appealed to theoretical astronomy in an attempt to settle the issue.55

4. Copernican astronomy and astrological physics in Gemma’s familia This last statement introduces a crucial new element to our story. So far, we focused on Gemma’s interest in Copernicus’ contributions to practical astronomy, and their relevance for astrological practice. It was argued that Gemma published these contributions in direct interaction with a context of courtly patronage. The interest in astrological events of this entourage was probably heightened by the intense military activity of Charles v. Patronizing astrological and astronomical reform publicly associated the patron with the ability to foresee future events.

see his Ephemerides (1556), fol. y2r. 52 De Goorle, Prognosticatie (1561), fol. a1v: “Also datse meestendeel ex ipsius proprio calculo gheprobeert wordende, somtijts meer dan onderhalf ure vroeger oft later te geschiedene bevonden worden, danmen in sine Ephemerides aengeteekent vint, die also geheel mendeus et incorrect ghedruct sijn.” 53 Ibid., fols. a2v-a3r. 54 Bazelius, Prognosticatie (1561), fols. a3r/v. On Giovanni Battista Carello, see Adelung, Fortsetzung (…) Allgemeines Gelehrten-Lexikon, vol. 2, p. 109; Gingerich, The Eye of Heaven, p. 232. 55 De Goorle, Prognosticatie (1561), fol. a1r: “Dat ten lesten die sake seer hooghe (ex ipsis Theoricis Planetarum, & sic ex primis Principijs) is ghetracteert gheweest, also datter schier van noode gheweest waer datmen daer toe hadde ghebruyckt lieden van goeden verstande, die in ipsis Theoricis Planetarum Purbachij & in easdem commentarijs Erasmi Reynholdi, etiam Erasmi Oswaldi, vel maxime in ipsius Ptholomei magno Sintaxi also gheverseert ware, dat hi onse questie soetelijcken ter neder gheleyt hadde, die noch op desen tijt, God betert, onbeslist hangt.”

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The following section qualifies this argument. It demonstrates that the interaction between astrological reform and courtly patronage did not necessarily take the shape of a one-to-one relation. Several members of Gemma’s professorial familia engaged in activities that suspended immediate confirmation of the patron’s power. Part of these activities focused on De revolutionibus as a novel body of theoretical astronomy: a cosmological model that explains and underlies the practice of astronomical prediction. However, it will appear that even the interest in astronomical theory was intimately linked with the problematic status of astrological physics. 4.1. Letter writing, Copernican astronomy, and the virtual familia Several published examples of astrological work in Gemma’s familia share an interesting characteristic: the inclusion of two prefatory letters. Following the standard dedicatory letter, where the main author of a treatise addresses his intended patron, we sometimes find a letter where Gemma, the mentor of these authors, introduces and commends the subject of each treatise. Our first example, Antonius Gogava’s Greco-Latin translation of Ptolemy’s Tetrabiblos (1548) reveals little difference in content between dedicatory and introductory letter.56 Gogava’s own dedicatory letter to Maximilian of Egmond, count of Buren, launched itself into an extended praise of the patron’s virtues, and finally compared the dangers of the battlefield with the risks of translation.57 In the subsequent letter, signed at Louvain on 1 October 1548, Gemma commended his pupil’s preference for Ptolemy’s ancient textbook over the more doubtful comments of contemporaries on astrological judgments.58 Both letters were examples of “persuasive” letter writing, the first making a request, the second delivering a recommendation.59

56

Gogava was born in Grave (now in the Netherlands), possibly in 1529. After his completion of the Tetrabiblos-translation, Gogava moved to Italy, where he studied medicine at Padua and became attached to the court of Vespasiano da Gonzaga at Mantua. After his studies, he established a medical practice at Venice, where he published a number of manuscripts on harmonics and optics before moving to Madrid. He died there in 1569. See V. Jacques, “Gogava (Antoine-Hermann)” in: bn, vol. 8, pp. 86–88. 57 See Obreen, “Egmond (Maximiliaan van).” 58 See Gogava, Cl. Ptolemaei Pelusiensis Mathematici Operis Quadripartiti, fol. a2r. 59 See Erasmus, On the Writing of Letters, trans. Fantazzi, pp. 71–73, 172–188.

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Things are different in our second example: Joannes Stadius’ ephemerides, based on Copernican parameters (1556). In his dedicatory letter to the new King Philip ii, Stadius emphasized two themes.60 First of all, he points out how images of Philip’s reign could be observed in the “celestial economy” (oeconomia coelestis).61 This was a direct reference to the central role of the sun in the Copernican system, which Stadius compared to the King’s command.62 Far more energy was expended, however, on Stadius’ exposition of the second theme: the astrological effect of celestial bodies in the sublunary realm. Once again, the patron’s support of Copernican astronomy and the astrology based on it, were presented as confirmation of his power and authority. On 28 February 1555, Gemma Frisius finished an introductory letter that was consistently printed after Stadius’ dedication in each edition that appeared during Stadius’ lifetime.63 This letter addressed Stadius in a familiar tone that contrasted strongly with Stadius’ deferential approach to Philip ii. This change of tone went hand in hand with a change of interest. Gemma’s letter spent little time demonstrating the merits of astrology, or relating socio-political topoi to astronomical theory. Instead, it provides a thorough discussion of the main objections against the use of Copernican astronomy, thereby brushing up against the academic prerogatives of natural philosophy and theology. The discussion of academic topics in familiar letters was hardly exceptional. What is remarkable, though, is the fact that their stylistic conventions (a friendly tone, and the desire to sustain conversation between the two correspondents) were inserted in a patronage con-

60 Stadius, Ephemerides novae et exactae (1556). A biography of Stadius is provided in chapter 6. 61 Stadius, Ephemerides novae et exactae, fols. a2v-a3v: “Qui quod Sol coelo est, hoc Rex imperio, sic Saturnus, sic Jupiter, sic Mars pepetua lege, & constanti harmonia in Epicycliis circumferentur, ut ipsorum motus cum accessu & recessu Solis aptissime congruat & cohaerat, atque hunc tanquam Regem suum venerari ac colere videantur (…) Imo si altius Rex serenissime inspicias, non regni tantum imagines coelesti in oeconomia conspicias, sed & eorum quae in terris fiunt, decreta (…).” 62 Compare with Copernicus’ dedication of De revolutionibus to Pope Paul iii. See Westman, “Proof, poetics, and patronage,” esp. pp. 186–194. 63 See Ernalsteen, Joannes Stadius Leonnothesius, pp. 29–49 for a complete bibliographic description. Stadius supervised editions in 1556, 1560, and 1570. After his death, his son Hieronymus signed the dedication of a 1581 edition, Francesco Giuntini the dedication of a 1585 edition.

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text that did not revolve around the two correspondents, Gemma and Stadius.64 Why was it considered useful to do so? It seems significant that this epistolary setting carefully replicated the situation of Gemma’s physical familia. Gemma Frisius started out as a medical student who provided private mathematical instruction to interested students. His early mathematical activity was heavily dependent on the interest in cosmographical didacticism on the part of Louvain students, Antwerp merchants, and courtiers at Brussels and Mechlin. Gemma’s promotion as medical doctor in 1541, which provided him with a fairly stable elite clientèle at court, simultaneously introduced a change in his mathematical ambitions, which shifted from cosmographical didacticism to astrological and astronomical reform. There is ample evidence that these last concerns also came to play a larger role in his private professorial role after 1541. In other words, Gemma’s familiar letter to Stadius exhibits the main characteristics of their familiar setting at Louvain: both were supported by court patronage, centered on astronomical and astrological issues, and engaged in academic didactic exchange. If the 1555 letter was indeed a virtual extension of this familiar space, then it seems likely that its insertion in a patronized context carried the public message that this same patron supported Gemma’s local familia. Such support paradoxically entailed that the familia’s rules of proper discourse were safeguarded.65 Familiar discourse could publicly fail to speak about its patron, because its public existence as such provided sufficient testimony to the patron’s status. In other words, patronage support of an academic familia did not pre-determine the latter’s public practices. Gemma Frisius’ interaction with Copernican theory provides us with an excellent example.

64 On the characteristics of the familiar or friendly letter, see Stowers, Letter Writing in Greco-Roman Antiquity, pp. 54, 58–78. Compare with Stewart, “Towards Defining an Aesthetic for the Familiar Letter.” 65 Compare with Bazerman, “Letters and the Social Grounding of Differentiated Genres,” p. 15: “The letter, in its directness of communication between two parties within a specific relationship in specific circumstances (…), seemed to provide a flexible medium out of which many functions, relationships, and institutional practices might develop – making new uses socially intelligible at the same time as allowing the form of the communication to develop in new directions.”

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4.2. Planetary distances and the systemic virtues of Copernican astronomy In his letter to Stadius, Gemma singled out two kinds of theoretical objections against Copernican astronomy.66 The first objection concerned the difference between Copernican and Alfonsine predictions of planetary positions. In reply, Gemma minimized the relevance of authority and antiquity for astronomy; instead, he proposes the combination of observation and demonstration (leading to increased precision) as a sounder criterion.67 Its embodiment is the historical improvement from Ptolemy, over Alfonso the Wise, to Copernicus and Reinhold in his own day.68 In second place, Gemma discusses objections to the “paradox of the earth’s motion and the sun’s being at rest in the center of the universe.”69 Initially, he adopts an instrumentalist perspective to the problem: hypotheses can be established in different, interchangeable ways. The crucial phrase occurs immediately after this, when Gemma adds that hypotheses are advanced: So that, having assumed principles that are not entirely absurd, but conformable to nature, we would have an explanation of the motions that corresponds to the visible positions of the stars in the heavens, both for the future and the past, as for the present.70 66 To some extent, my discussion is dependent upon Fernand Hallyn’s “La préface,” an illuminating study of Gemma Frisius’ aforementioned 1555 letter. 67 Stadius, Ephemerides (1585), pp. 1–2: “Non enim res semper aestimanda est ab authoritate tractantium, sed adhibita demonstrationis norma Ïσπερ πρÞσ τ’“ρÀκλειον λÝ©ον expendenda est. Neque iterum, an vetera, an nova sint, quae tractantur, refert: sed potius Aristotelis consilium utrobique rectissimum sequendum est; quo pronunciat, φιλεÝν ˆµφÞτερου, πεÝ©εσ©αι τοÝσ ˆκριβÜστεροισ δεÝν (…) De his igitur nemo censuram ferre poterit, nisi qui eiusdem principijs usus, hoc est, τοÝσ φαÝνοµενοισ καÝ ˆπÞδειξεσι, simili ut illi via processerit. Verum hoc opus, hic labor est, sic patet iter ad astra.” Gemma refers to Aristotle, Metaphysics 1073b. 68 Stadius, Ephemerides (1585), p. 2: “Hoc sequuti maiores nostri, omissis Ptolemaei tabulis, sibi novas extruxerunt, quod unicum fuit Alphonsi studium plusquam Regnum (…) Hoc studium fuit Copernici, viri ingeniosissimi & solertissimi, hoc nos pro nostra tenuitate per multas observationes, ex quibus haec pulcherrima scientia initium progressumque capit, adiunctis etiam demonstrationum fulcimentis infallibilibus, sequuti sumus.” 69 Ibid., p. 2: “Restat iam ultimus nodus de Terrae motu, Solisque in mundi centro quiescentis τÞ παρÀδοξον.” 70 Ibid., p. 2: “Sed ut assumptis non prorsus absurdis, sed naturae congruis exordijs, habeamus certam rationem motuum correspondentem, in coelo conspicuis stellarum locis, tam pro tempore futuro vel elapso, quam pro praesenti.” I disagree with Fernand Hallyn’s translation of this passage, who renders assumptis non prorsus absurdis as “acceptées comme n’étant absolument pas absurdes” (Hallyn, “Préface,” p. 6), which effectively makes Gemma’s position on the degree of absurdity of the

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This passage provides two conditions that an astronomical theory must meet. The first requires that a hypothesis uses principles that are “not entirely absurd, but conformable to nature.” Gemma’s second criterion simply leads us back to his first objection: an astronomical theory must provide accurate predictions of the angular positions of celestial bodies. Although one could easily argue that this criterion carried most practical weight, one should heed the fact that it was logically second (“having assumed”). Let us therefore focus on Gemma’s use of the first condition. Although much could be said for the Ptolemaic model, Gemma pointed out that it was quite absurd (or “not conformable to nature”) in two respects.71 First of all, it allowed for non-uniform planetary motion (the reason for the introduction of the infamous equant). Second, it could not explain the synchronism between the retrograde motion of the three superior planets and the solar motion. Gemma emphasized the importance of these pro-Copernican arguments through the Aristotelian distinction between demonstratio quia (“demonstration of the fact”) vs. demonstratio propter quid (“demonstration of the reasoned fact”).72 Like his colleagues at Wittenberg, Gemma probably knew that the cosmological paradox could be solved, by transferring Copernican parameters to a traditional geostatic model.73 Nevertheless, he insisted on retaining the earth’s daily motion around its own axis and its annual motion around the sun (“the first two motions”): But if someone would like to do so, he can refer those terrestrial motions that [Copernicus] posited besides the two first ones [my italics], to the heavens, and still use the same canons of calculation.74

Copernican hypothesis much stronger than is expressed by the original non prorsus. 71 Stadius, Ephemerides (1585), p. 2: “Non pauca tamen illae [hypotheses Ptolemaei] absurda committunt, dum stellae in suis circulis inaequaliter moveri intelliguntur, tum non habent tam evidentes τñν φαÝνοµενων causas atque illae Copernici.” 72 See Hallyn, “Préface,” pp. 7–8. Gemma uses the terminology of Aristotle, Posterior Analytics 71b17–72b4. On the importance of Aristotle’s theory of demonstration for sixteenth-century astronomy, see Barker/Goldstein, “Realism and Instrumentalism,” pp. 243–252; Barker, “The Role of Religion,” pp. 72–82. 73 On Peucer’s Hypotyposes orbium coelestium, see Westman, “The Melanchthon Circle,” pp. 180–181; on Praetorius, see Westman, “Three Responses,” pp. 289–305. 74 Stadius, Ephemerides (1585), p. 3: “Quin si quoque quispiam velit, poterit illos motus terrae, quos praeter duos primos ponit, ad coelum referre, ac uti ijsdem canonibus calculorum.” Further statements on the translation of Copernican astronomy in the work of Gemma are conveniently summarized in Hallyn, “La préface,” pp. 10–11. My identification of Gemma’s “first two motions of the earth” is based on Copernicus’ terminology and order of exposition in book 1 of On the Revolutions.

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Translation exercises were limited to a restoration of the traditional eighth and ninth spheres of Alfonsine astronomy. This attitude agrees well with Gemma’s previous emphasis on the synchronism between solar and retrograde motion, which Copernicus explained through the earth’s annual motion around the sun. Gemma’s attitude was extremely rare. Among the first generation of post-Copernican astronomers (born between c. 1495 and 1525), only Rheticus displayed a similar commitment to the systemic features of the Copernican model.75 What prompted this Louvain mathematician to acknowledge the systemic advantages of Copernicus’ annual motion of the earth? Which problem did he expect this to address? Turning to Gemma’s correspondence on the matter provides two distinct clues.76 In his letter to Dantiscus of 20 July 1541, Gemma wrote:

75 See Westman, “The Melanchthon Circle.” This paper investigates the attitudes of the highly influential “Melanchthon circle” at Wittenberg, which included -under the guidance of Philip Melanchthon (1497–1560)- Erasmus Reinhold, Caspar Peucer (1525–1602) and Georg Joachim Rheticus. In his meticulous study, Westman proposed the term “Wittenberg interpretation” to refer to “a common methodological outlook or style, a consensus on how to ‘read’ the newly published De revolutionibus.” This hermeneutic was characterized by: 1. The use of Copernican astronomy to predict the angular positions of planets or eclipses, pending a more careful recomputation of the parameters in De rev. if this was necessary (as did Reinhold); 2. In some cases, a preference for specific features of the Copernican model, e.g., the absence of the equant-point; 3. The wish to translate these models into a geostatic reference-frame. Apart from these three positive concerns, the absence of an interest in planetary distances was another specific feature of the Wittenberg interpretation. Until now, Rheticus was the only early exception to this moderate and pragmatic attitude towards the Copernican theory. 76 Further evidence seems contained in Gemma’s enthusiasm for Copernicus’ lunar model as a solution for the observed variability of the lunar diameter, which contradicted recent Italian proposals to revive Aristotle’s homocentric astronomy as a model for mathematical astronomy. See Gemma Frisius, De radio astronomico, fols. 28v-29v. On the history of Copernicus’ lunar model, see Neugebauer, History, pp. 84–86, and Swerdlow/Neugebauer, Mathematical Astronomy, pp. 193–197. Homocentric astronomy was best known in the Latin West through Alpetragius’ (fl. second half 12th c.) De motibus celorum, which had recently been defended in Girolamo Fracastoro’s Homocentrica (1538). On this tradition, see Grant, Planets, Stars & Orbs, pp. 559–556; Goldstein, Al-Bitrûjî, vol. 1; Swerdlow, “Aristotelian Planetary Theory in the Renaissance.” Fascinating perspectives on the cosmological attractions of homocentric astronomy among mathematical astronomers are provided in Shank, “Regiomontanus and Homocentric Astronomy.” Further considerations of the ramifications of homocentric astronomy are provided in Mulsow, Frühneuzeitliche Selbsterhaltung, pp. 140–200.

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And why [would Copernicus’ theory] not [be] new? For we may expect that the universe, which before was thoroughly unknown and depicted with uncertain boundaries, will henceforth be well-known as if this was deduced from the heavens.77

Copernicus had enabled man to fix the “uncertain boundaries of the universe.” This theme was repeated with a little more clarity in the letter to Stadius of 28 February 1555: From these [i.e. Copernicus’ hypotheses], a better knowledge of the planetary distances is gained than from the others [i.e., the Ptolemaic hypotheses].78

Gemma’s enthusiasm for Copernicus seems to have been linked with the problem of planetary distances. This problem is easily stated: Ptolemaic astronomy offered no conclusive method to determine distances between the earth and the various planets (apart from the luminaries).79 In his Planetary Hypotheses, Ptolemy calculated planetary distances on the assumption that no empty spaces existed between the spheres of successive planets. Moreover, there was no compelling argument for Ptolemy’s ordering of the planets. His own scheme was largely based on the increasing sidereal periods of successive planets. Copernicus’ heliostatic astronomy changed this when it explained planetary retrograde motion as an optical effect of the earth’s motion around the sun. The planetary epicycles that Ptolemy used to account for retrograde motion were now replaced by the earth’s orbit around the sun. Since this single circle had become a common feature of every single planetary model, it could also function as a common standard for planetary distances in the Copernican universe.80

77 de 429: Dantiscus, Correspondence, ed. De Vocht, pp. 344–347: Van Ortroy, Biobibliographie, pp. 408–410: “Et quid ni novum? quum hactenus ignotum prorsus et incertis depictum limitibus orbem, iam deinceps tanquam e coelo asportatum notissimum simus habituri?” 78 Stadius, Ephemerides (1585), p. 3: “Unde hic amplior cognitio de planetarum distantijs colligitur, quam ex illis.” 79 The classic study on the history of measurements of the universe is van Helden, Measuring the Universe. 80 It is well known that this posed two new problems. First, Copernicus’ figures for greatest and least distance of every planet suggested that the universe was either filled with spheres that were much thicker than necessary, or else contained a considerable amount of empty space. Both assumptions violated fundamental tenets of Aristotelian physics. Copernicus also had to account for the absence of a detectable annual parallax of the fixed stars by placing them at previously unimagined distances from the center of the universe.

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It is less easy to grasp the reasons that spurred Gemma’s extraordinary interest in Copernicus’ planetary distances. In the following sections, I will argue that the answer lies in his attempts to adress the Piconian critique of Ptolemaic astrological physics. These attempts were part of a project that Gemma and his pupils carried out at Louvain in the 1540s and 1550s, and which found its most systematic expression in John Dee’s Propaedeumata aphoristica (1558).81 4.3. The Louvain background to Dee’s Propaedeumata aphoristica (1558) In between terms at Cambridge, where he studied the arts since 1542, the English polymath John Dee (1527–1608/9) visited Louvain in the summer of 1547. Having received his ma in 1548, he returned to Louvain in June, remaining there at least until July 1550.82 In his autobiographical Compendious rehearsall (1592), Dee relates that he spoke and conferred “with some learned men, and chiefely mathematicians, as Gemma Frisius, Gerardus Mercator, Gaspar à Mirica, Antonius Gogava, &c” in 1547.83 In the famous Mathematicall Praeface to the Billingsley Euclid (1570), Dee emphasized the role of Mercator and Gogava: I was (for *21. yeares ago) by certaine earnest disputations, of the Learned Gerardus Mercator, and Antonius Gogaua (and other,) thereto so prouoked: and (by my constant and inuincible zeale to the veritie) in obseruations of Heauenly Influences (to the Minute of time,) than, so diligent: And chiefly by the Supernaturall influence, from the Starre of Iacob, so directed: That any Modest and Sober Student, carefully and diligently seking for the Truth, will both finde and confesse, therin, to be the Veritie, of these my wordes.84

81 The standard edition is Dee, Propaedeumata aphoristica, eds. Shumaker/Heilbron (henceforth referred to as “Dee, Propaedeumata”). This edition establishes and translates the text of both the first and second editions (London, 1558 and 1568). The next sections develop an idea that was advanced by John Heilbron in Dee, Propaedeumata, pp. 56–58. 82 On Dee’s stay at Louvain, see Clulee, Dee’s Natural Philosophy, pp. 26–30. For an overview of the chronology of Dee’s life, see Roberts/Watson (eds.), John Dee’s Library Catalogue, pp. 75–78. Dee himself dates his final departure from Louvain on 15 July 1550 in Compendious rehearsall, published by Crossley on the basis of Dee’s own diary of that period. This date agrees well with the information gathered from his book-acquisitions in this period. We also know that Dee gave lectures on Euclid at Paris in the summer of 1550, where he probably arrived from Louvain. 83 Dee, Autobiographical Tracts, ed. Crossley, p. 5. 84 Dee, Mathematicall Preface (1570), fol. b4r.

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Dee dedicated the Propaedeumata to Mercator, with whom he had spent much of his time at Louvain “learning and philosophizing,” until his “whole system of philosophizing in the foreign manner laid down its first and deepest roots.”85 It is exactly the topic of these discussions, Dee continues, which constitutes “that subject which I am now to treat.”86 There was something remarkable about Dee’s presentation of the Propaedeumata. First of all, it seems difficult to situate his dedicatory letter in a patronage context. As a patron, Mercator had very little to offer. Having left Louvain in 1552, he continued his cosmographical activity in the modest city of Duisburg, which remunerated his lessions at the local gymnasium with “three fat pigs.” Only in 1564 did Mercator become court cosmographer to the local Duke of Cleves.87 This enabled him to initiate prestigious chronological, cosmographical and instrument-building projects, but hardly placed him in a position where he could invest and distribute his social status over a network of clients. Neither did Dee aspire to any commercial success for the first edition of the Propaedeumata. In third place, we find that the Propaedeumata did not respect established academic hierarchies. Its title page referred to the mathematician-instrument maker Mercator as “mathematician and philosopher.”88 The Propaedeumata addressed neither court, city, nor university. Instead, Dee explained that: The purpose is that from the report of this scout I may consider, in myself and with my learned friends, whether I should now extend my forces, such as they are, immediately into foreign fields or should train them still more diligently in military discipline at home.89

Once again, we encounter familiar letter writing as a rhetorical aid for the codification of a concern with theory in Gemma’s circle. Although we might be tempted to read it as a sidereal messenger, the Propaedeumata was more of an informer. It was addressed to the Louvain familia that trained Dee, requesting feedback on the progress of his investigations across the channel. Facing unexpected competition, Dee clearly lacked confidence about the strength of his results, and turned to Mercator and friends with the request to “put their heads together for the investigation of the truth and the expanding 85 86 87 88 89

Dee, Propaedeumata, p. 111. Ibid., p. 113. Van der Gucht, “Gerard Mercator. Une biographie,” p. 144. Dee, Propaedeumata, pp. 102–103. Ibid., pp. 117–119.

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of useful sciences.”90 Soon, Elizabeth i (1558–1603) would indeed recruit Dee’s skills for the expansion of her personal power.91 At this time, however, it was still too early.92 4.4. The interpretive problem of the Propaedeumata Dee’s Propaedeumata offered his proposal for a reformed astrology, based on the optical model of celestial influence (see chapter 3). Dee illustrated this model through the action of a loadstone.93 Since action at a distance was considered impossible, some invisible diffusion of the magnet’s power must be inferred. The study of the magnet’s actions teaches us two things. First, its power is spread out in every direction in the surrounding medium. Second, this power only acts upon bodies with a specific constitution. In Dee’s time, such diffusion of power through a medium was usually referred to as the “multiplication of species.” The Latin term “species” (the “likeness of an object”) referred to the “force or power or influence by which objects act on other objects.”94 Its basis had been worked out by the Arabic philosopher al-Kindi (d. c. 873), who claimed that objects interact with each other through “rays,” which every object disperses continuously in every direction of the universe.95 These rays are constituted by a likeness of the object’s quality. Since their force diminishes with distance, a unique combination of influences of variable strength results in every part of the world. Robert Grosseteste (1168/70–1253) highlighted the metaphysical potential of this idea through his conviction that the world was shaped from the gradual action of light on formless matter. In doing so, he privileged geometrical and optical analysis as a suitable narrative for natural-philosophical discussion. It was Roger Bacon 90 Ibid., p. 113. The elusive Jofrancus Offusius had published a very similar scheme to that of Dee’s Propaedeumata in his ephemerides for 1557. See Dee, Propaedeumata, pp. 54 and 59. For an overview of information on Offusius, see Gingerich, “The Master of the 1550 Radices.” 91 See Clulee, John Dee’s Natural Philosophy, pp. 33 and 121–125. 92 That the publication of the Propaedeumata was not evident in 1558 is also confirmed by the fact that it appeared as an appendix to an edition of a genethliacal treatise by the more reputed Cyprianus Leovitius. See Clulee, John Dee’s Natural Philosophy, p. 35. 93 Dee, Propaedeumata, p. 133 (Prop. xxiiii). 94 Lindberg, “Light, Vision, and the Universal Emanation of Force,” p. 246. 95 See Al-Kindi, “De radiis,” eds. d’Alverny and Hudry; Loth, “Al-Kindi als Astrolog.”

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(c.1214/20–c. 1292) who carried this project to completion in his extensive De multiplicatione specierum.96 In this work, Bacon developed the natural-philosophical implications of the “species”-model, often in dialogue with Aristotelian physics. At the same time, he systematized and promoted Grosseteste’s idea that the propagation of species was open to mathematical analysis by means of optics and geometry. Nicholas Clulee initially argued that Dee’s proposals in the Propaedeumata were profoundly shaped by his study of these three authorities between 1556 and 1558. However, he did not clarify what motivated Dee to embark on these studies.97 In a later contribution, Clulee pointed to Nicole Oresme, who used the optical model to criticize astrology, and to a later reworking of Oresme’s ideas by the obscure Claudio Celestino (1542).98 However, these obscure texts strike us as unlikely sources for the problems that Dee sought to address.99 Instead, the next section argues for a more plausible and straightforward source, namely the critique of Pico’s Disputations. 4.5. The Piconian background to the Propaedeumata After his departure from Louvain, Dee made a study tour through France. While in Melun, he jotted down a singular note in his copy of Ptolemy’s Tetrabiblos on 14 September 1551.100 The note contained a brief exposition of Dee’s ideas on the relation between celestial influences and the human body and soul. It states that the souls and bodies of men vary with the region they inhabit, and identifies two distinct causes: heat and cold, as they operate both through the proper virtue of the region and through the heavenly revolutions. Of the four primary qualities, only these two can have a real effect.101 As an illustration, Dee mentioned the generative semen of men, which is 96

See Lindberg, Bacon’s Philosophy of Nature. Clulee, “Astrology, Magic, and Optics,” pp. 654–676. 98 Clulee, John Dee’s Natural Philosophy, pp. 57–59. 99 Ibid., p. 60, states that the challenges of Oresme and Celestino “contributed” to Dee’s earlier Louvain discussions with Mercator. 100 Now preserved in London, Royal College of Physicians, 48e d18/8: Claudius Ptolemaeus and Haly Avenrodoan, Quadripartitum (1519). 101 London, rcp, 48e d18/8, fly-leaf: “Cuius rei caussam, a duobus potissimum rebus derivare videntur omnes, qui sunt philosophiae praeceptis exculti, frigore minimum et calore. Horum, cum ex loci naturae virtute, tum ex anni varia revolutione, variae efficiuntur mixtiones, diversissimarum generantes mortalium naturali. Hae siquidem ex quatuor illis primis qualitatibus, solae efficere aliquid, et in natura moliri quiquam valent, reliquae sua debilitate subiectae, ab hijs pati solent.” 97

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more deprived in Egypt than it is in England, due to the violent heat and the humor. This heat, he added, was not the extrinsic heat that one usually feels, but a secret celestial ardor nurturing everything that the earth contains.102 There is a distinct Piconian flavor to these comments.103 In Dee’s early astrological physics, the central role is accorded to a nurturing heat that flows down from the heavens. Like Pico, Dee suggests that moisture and dryness play no active role in this process, thus anchoring them firmly in their sublunary state.104 And last but not least, Dee shares Pico’s preference for the Aristotelian-naturalistic unity of body and soul.105 This legacy was still pervasive in the Propaedeumata, although Dee was now trying to harmonize Pico’s emphasis on the sublunary realm with astrology’s attribution of elemental qualities to celestial bodies. In aphorism c, Dee advised his readers to: “Hold this steadily in mind, that each planet, by reason of its own peculiar body, mixes some other sensible quality with the general virtue of its heat (calor generalis).”106 What was this “other sensible quality”? Dee asks us to consider the sun’s light. It is common knowledge that this light imparts a “general heat” to us, which is responsible for processes of qualitative change (e.g., the drying up of wells in the summer). At the same time, however, we notice the sun’s role in formal change (generation and corruption, e.g., when new life begins in the spring). This is why “a special dominion over vital heat accompanies the sun’s excellent light” (Prop. ciiii).107 102 London, rcp, 48e d18/8, fly-leaf: “In aegypto igitur quam in Anglia solis fervore per istum magis & Humore suo spoliatum existit, hominum intrinsecus in eorum visceribus latens genitale semen. Jam non loquor de calore illo extrinseco eius regionis incolaris feriente, sed de secreta fervoris vi, qua a summo stellarum choro ad penitissima quaeque quae in terris continetur allabitur.” 103 Dee’s note departed from Pico’s Disputations on one single point: the explanatory autonomy of sublunary substances. Dee emphasizes that Egyptian or English bodies and souls were causally dependent upon their environment, and ultimately upon the heavens. It is no surprise to find these comments inserted in a copy of Tetrabiblos, where Ptolemy had promoted exactly this kind of causal reductionism (see chapter 1). The same attitude on the role of the semen is expressed in Prop. xxi. See Dee, Propaedeumata, p. 131. 104 Compare to Prop. ciii–cvi, where Dee attributes the dominion over vital heat to the sun, and the regulation of sublunary moisture to the moon. See Dee, Propaedeumata, p. 185. 105 This element was emphasized in Clulee’s comments on this text. See Clulee, “Astrology, Magic, and Optics,” p. 646. 106 Dee, Propaedeumata, p. 183. 107 Ibid., p. 185.

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So far, there is little that could not be found in book iii of the Disputations. The same conclusion applies to Dee’s conviction that the moon governs sublunary moisture as a result of its limited heat (Prop. ciiii).108 However, Dee stated that the moon was not only an “arouser,” but also a “producer” of humidity (Prop. ciii). This suggests that Dee in fact defended two interpretations of the “other sensible quality.” On the one hand, the traditional astrological idea that celestial influence actively distributed all elemental qualities (“producer”); on the other hand, Pico’s Aristotelian idea that celestial influence only imparted a double heat which affected sublunary qualities (“arouser”). This agrees with Dee’s sharp distinction between sensible and “more secret” rays (Prop. xxv).109 Dee compared the relation between these sensible and insensible rays to that between body and soul (Prop. cxi).110 Even more remarkable was his statement that insensible rays could not be stopped from penetrating “in an instant of time everything that is contained in the universe” (Prop. xxv).111 Dee seemed to confirm this in Prop. liii, as he described his general “catoptrical” procedure for the investigation of various effects of celestial bodies. In the second edition (1568), Dee clarified that this method was intended for the investigation of sensible rays.112 What should we make of Dee’s lack of clarity concerning occult influences?113 If anything, this seems to constitute yet another parallel with Pico’s Disputations. In chapter iv.1, Pico characteristically stated that celestial occult influences could be both upheld and rejected, depending on one’s general position about astrology. Most of his efforts were directed towards the astrologer’s use of the

108

Ibid., p. 185. Ibid., p. 133. See also Prop. xciiii. In the 1568-edition, Dee explicitly calls the latter “more secret rays of influence (influentiae).” 110 Dee, Propaedeumata, p. 189. 111 Ibid., p. 133. Clulee notes this treatment of occult influences without inferring any particular conclusions from it (see “Astrology, Magic, and Optics,” p. 655). 112 Dee, Propaedeumata, p. 148, note 55. 113 In fact, this could introduce a departure from Roger Bacon, whom Clulee mentions as Dee’s main source for the argument of the Propaedeumata (Clulee, “Astrology, Magic, and Optics,” pp. 642–643). In De multiplicatione specierum, Bacon proposed a unitary theory of the nature and propagation of “species” (see Lindberg, Bacon’s Philosophy of Nature, pp. liii–lxxi). 109

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four primary qualities.114 The similarities with Dee’s attitude in the Propaedeumata suggest that Dee read his sources in mathematical optics with a highly selective eye, alert to the problems that Pico’s Disputations had raised.115 4.6. The Louvain connection: astrology, optics, and mathematics This leaves two questions unanswered. First, did Dee’s acquire his interest in the Disputations at Louvain? Second, did this early interest include the optical model and a mathematicized astrology? The first question is the easiest to answer. It seems impossible that Dee would not have been exposed to Pico in his Louvain student days if we consider the impact of Pico’s Disputations on the Louvain 1524 debates, as well as the continuity between the protagonists of these debates and Gemma’s familia.116 Pico’s Disputations still received elaborate comments in a defense of astrology that was published at Louvain in 1552.117 The second question is more difficult, because no annotated copy of the Disputations from Gemma’s familia has so far been discovered. The second best thing, however, may be an astrological text for which Dee, the Louvain circle, and Pico all showed a remarkable respect: Haly Avenrodoan’s medieval commentary on Ptolemy’s Tetrabiblos.

114

Disputationes, vol. 1, pp. 384–390. My argument for a more restrictive reading of the Propaedeumata problematizes Deborah Harkness’ recent argument that Dee’s optical studies provided the basis for a continuity in Dee’s work which encompasses both the Propaedeumata (1558) and the remarkable angel conversations (1581–1586). Harkness builds up a case around aphorism xiiii, where “Dee described the metaphysical connection between light and certain ‘spiritual species’ that were able to “flow from things both through light and without light.” This connection, along with the privileged position Dee accorded to light, forged a metaphysical connection between light, perfection, and spirituality” (Harkness, John Dee’s Conversations with Angels, pp. 118–119; also on pp. 74–75). It is unclear to me how the Propaedeumata make an essential connection between light and spirituality, when Dee explicitly says that spiritual species propagate themselves through light and without it. 116 Daniel C. Andersson (Warburg Institute, London), whose dissertation includes a study of Henry Howard’s attack on divination (early 1580s), informs me that no solid discussion of Pico’s Disputations seems to have occurred in England before the 1560s. For an older account of early English astrological debates, see Allen, The Star-Crossed Renaissance, pp. 101–146. 117 This tract was written by Pieter Haschaert, a physician of Brussels, and published by Antoine-Marie Bergagne, a Louvain printer who published several learned Latin tracts in the 1550s. See Thorndike, History, vol. 5, pp. 329–330. 115

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Pico’s frequent admiration for Ptolemy’s commentator has been mentioned before (chapter 3).118 In the dedicatory letter of his own translation of Tetrabiblos (1548), Gemma’s pupil Gogava complained about the lack of Greek or Latin commentaries on Tetrabiblos. Fortunately, there had been Haly Avenrodoan: Who, to my knowledge, remains the only one who imparted us his own commentary. To this, he owes his life and eternal fame among posterity, even if he sometimes departs from the opinion of Ptolemy, which will provide us, God willing, with an occasion to speak [about this topic]. This should not seem strange in view of the difficulty of these matters.119

Coming from a man who, only half a page before, had accused Arabic translators of rendering Tetrabiblos with contradictions and verbal horror and rot (dictionis horror et pudititas), these comments betray a remarkable appreciation for Avenrodoan. John Dee’s annotated copy of this text provides us with some interesting clues on the impulse that Renaissance astrologers received from Avenrodoan’s commentary.120 The first example concerns the commentary on Tetr. i:393–398 (chapter i.4), where Ptolemy discussed the nature of the moon’s effects. Avenrodoan glossed this passage as an indication that a planet’s power depends upon its magnitude, but also on its proximity and sidereal period. Dee underlined the latter part, adding the following marginal note: From this, I take it that all planets have an effect in accordance with both their size and distance from the Earth and the individual elements. However, I already assumed this, and wrote it down, before I read it here. See below, chapter 8.121

118 Passages where Pico finds Avenrodoan’s opinions worthy of consideration can be found in: Disputationes, vol. 1, pp. 140, 458, 472, 492, 548; Disputationes, vol. 2, pp. 12, 36, 82, 248–250, 288, 304, 324, 330. Cardano, who published his own commentary on Tetrabiblos in 1554, also testified to his deep admiration for Avenrodoan. See Ernst, “‘Veritatis amor dulcissimus,”’ pp. 50–51. 119 Ptolemaeus, Quadripartiti traductio, trans. Gogava, fol. a3r: “[Hali Arabis,] qui unus, quod sciam, hactenus enarrationem nobis suam impartiit, cui vitam quoque acceptam refert, & memoriam sui apud posteros aeternam. Quanquam nec semel ille a Ptolemaei sententia aberrat, quo de & nobis dabitur Deo favente dicendi locus, & mirum videri in tanta rerum difficultate non debet.” 120 London, rcp, 48e d18/8. Dee dates his comment on the fly-leaf of this copy to 14 September 1551. It is difficult to date the annotations, but their content and the obvious importance of the text make it likely that the same terminus ante quem can be proposed for the notes. On Dee’s general reading policies, see Sherman, John Dee. The Politics of Reading and Writing, who does not comment on the content of Dee’s annotations. 121 London, rcp, 48e d18/8, fols. 8v-9r: “[text of Avenrodoan’s commentary, Dee’s

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In the text of the commentary to Tetr. i:403–407, Dee underlined a passage which states that “it is fitting that [astrologers] should investigate whether the stars which have a particular aspect to the luminaries, increase or decrease their action through those,” and added the manuscript comment “Rule through which the virtues of the stars can be found.”122 Dee’s heavy underlining and annotating of the commentary to Tetr. ii:939–941 and ii:950–951 (chapter ii.11) connects this text to his interest in the force of the fixed stars (Prop. xxxv, xxxvi, lxxviii, lxxxviii).123 This interpretation implied an active interest

underlinings are italicized] Postquam docuit nos quod virtutes stellarum corporum suorum sequitur magnitudinem et corpus lune parvum est sicut in almagesti monstravit: et eius opus solis in parte una: dicit hic quod est hoc pro eo quod est multum circa terram et pervenit ad nos eius virtus antequam mutetur: et propter hoc apparet eius opus magis quam aliarum stellarum: et videmus visibiliter quod tradit humores terre: et corporum eam sequentium (…) [manuscript note by Dee:] Hinc colligo quod omnes planetae operentur tum pro ratione magnitudinis suae tum pro modo distantiae a terra & Elementis singulis. Quod quidem ante quam hunc legerem et putabam & scripsi vide infra capite octavo.” 122 Ibid., fol. 9r: “[text of Avenrodoan’s commentary, Dee’s underlinings are italicized] Convenit ut inspiciant ad stellas habentes communitatem cum duobus luminaribus per figuras si augent in suis operibus: vel ab eis minuunt (…) [manuscript note by Dee:] Regula qua stellarum virtutes deprehendi possunt.” 123 Ibid., fols. 42v-43r: “[text of Avenrodoan’s commentary, Dee’s underlinings are italicized] Vult dicere quod stelle fixe quae erant in suo tempore in principio arietis habent complexione quae non commiscetur cum complexione solis: quae pertinet ad totum signum arietis: et quod accidit idem quaedam virtus quae trahit fumositates humidas quae sunt materia pluviarum et ventorum. Similiter stelle fixe quae erant suo tempore in medio signo arietis: habent complexione non commiscente cum complexione solis quae pertinet ad totum signum arietis: et accidit idem quaedam virtus quae assimilabitur virtuti iovis et veneris in temperamento. Similiter stelle fixe quae tempore suo erant in fine arietis habent complexione non commiscente cum solis complexione quae pertinet ad totum signum arietis: et accidit idem virtus una quae assimilabitur virtuti martis in sua combustione: et est generatrix mortalitatum eo quod facit putrescere humiditates in hyeme congregatas: et quando res ita fuerit: convenit ut cum aliqua res harum stellarum mutabitur ad signum tauri commixtio fiat inter eas: et opus solis quod pertinet ad totum signum tauri. verbi gratia iam intelleximus quod complexio solis quae pertinet ad totum signum arietis est generatrix fumositatum humidarum quae faciunt nubes: tonitrua: et relampagos [marginal note by Dee: “Quando figura Arietis pervenerit ad Taurum cur judicandum sit”] (…) Et est declaratum quod hec complexio harum stellarum generat similiter fumositates humidas: et quando mutabuntur he stelle ad medium arietis: et commiscent sue virtutes facientes humiditatem cum virtute solis in signo arietis: accidit nihil ventorum et minus pluviarum (…) Verba Ptolomei quae dicit in quolibet signo per se possunt habere glossa duas. una est quam ante diximus quod signa recipiunt a sole virtutem unam quae concordat cum suo opere quando ipsum ingreditur. alia est quod signum recipit ab omnibus alijs stellis fixis quae sunt in eo vim unam quae concordat cum coniunctione quae fit per commixtione omnium: tamen glossa prima est convenientior verbis

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in astronomical precession, which re-appeared in the Propaedeumata (Prop. lxxv).124 If we assume that Dee’s reading of Avenrodoan’s commentary reflects his interests at Louvain, then we can conclude that each of the fundamental concepts of the Propaedeumata (light physics, optical model, and mathematical narrative) were already in place in this early period. Dee’s later study of Grosseteste and Bacon undoubtedly helped him to systematize and detail these elements towards publication in the Propaedeumata. But there is no reason to assume a development in two phases, including an indeterminate naturalistic bent at Louvain and a more detailed “mathematical turn” after Dee’s return to England.125 This conclusion is reinforced if we consider another astrological artefact of Gemma’s Louvain familia: two Latin treatises that Antonius Gogava appended to his translation of Ptolemy’s Tetrabiblos in 1548. One of these treatises, entitled De sectione conica, was usually ascribed to Roger Bacon in the medieval manuscript tradition.126 Marshall Clagett has shown that this treatise, which he calls the Speculi almukefi compositio, was probably composed between c. 1250 and c. 1350. Regiomontanus prepared a slightly shorter manuscript version in the second half of the fifteenth century. It is this later text that Gogava used for his own edition.127 The Speculi almukefi compositio provided a theoretical discussion of conic sections basis in the tradition of Alhazen’s (c. 965–1039) De speculis comburentibus. The treatise also suggested astronomical or astrological applications of its content.128 Gogava’s other treatise, entitled De speculo ustorio, was simply an abbreviation of Alhazen’s De speculis comburentibus, containing the first four propositions.129 This tract is particularly interesting because it contains the basis of what the Propaedeumata called “catoptrics” or the study of the reflection of light. Dee found this discipline impor-

Ptolemei et bene apparet quod virtus geminorum est similis virtuti iovis. [note by Dee in the margin: “Duplex interpretatio singulorum signorum”].” 124 Dee, Propaedeumata, pp. 161–163. 125 Clulee, John Dee’s Natural Philosophy, pp. 70–71. 126 Gogava criticized this attribution to Bacon. 127 On the history and content of this text, see Clagett, Archimedes in the Middle Ages, vol. 4.1, pp. 99–111, which is supplemented with a critical edition and translation (pp. 114–158). An edition (with translation of the original additions) of Regiomontanus’ text can be found on pp. 203–234. 128 See the edition in Clagett, Archimedes in the Middle Ages, vol. 4.1, pp. 137–138. Also see Clagett, Archimedes in the Middle Ages, vol. 4.1, p. 179. 129 See Clagett, Archimedes in the Middle Ages, vol. 4.1, pp. 319–320.

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tant for both the investigation and use of celestial rays. While enabling a more precise investigation of the properties of celestial rays, catoptrics also allowed one to bundle them and increase their force (just as burning mirrors concentrate light rays).130 Gogava’s assimilation of these treatises to the quintessential astrological textbook, indicates that the utilitarian aspects of a mathematical and optical approach were promoted among Louvain’s astrological patrons by 1548. Similarly, one could argue for Gerard Mercator’s early commitment to the optical model on the basis of a little cosmographical textbook that his son Bartholomeus (1540–1568) published in 1563. This treatise was based on Gerard Mercator’s lectures at the Duisburg Gymnasium in the early 1560s.131 Unlike other textbooks, it contained a short chapter on the effects of the stars and their incidence in the sublunary world. In this chapter, students could learn that “all separate stars have their own rays through which they transfer the proper virtues of their nature to inferior bodies,” rays which are most vigorous when they hit an object “according to the diameter of the star itself,” and least so when they are projected aside. Mercator also emphasized the relevance of the angle of incidence.132 130

On catoptrics, see Dee, Propaedeumata, pp. 67–73. Mercator, Meditatiunculae (1563), fols. a2v-a3v. Bartholomeus recounts how his father, when he was drawn away from his teaching by urgent affairs (“Rebus deinde paulatim (ut fit) urgentibus, Principalium negotiorum necessitate distractus”), entrusted these lessons to him, who had previously attended his father’s instruction. Faced with the need of providing course-material almost overnight, Bartholomeus mainly based himself on things learned from his father, bringing these together in a rational and methodical manner (“Quod erat in proclivi, ex recenti memoria pulcherrimarum rerum quas a Patre quasi per manus acceperam, solicite meditari coepi rationem quandam & methodum, rudioribus accommodatissimam, qua simul & brevissime & facillime, discentium ingenia ad mediocrem praestantissimarum artium cognitionem deducerentur. Proinde & ijs quae Patrem meum studiosum harum artium cultorem accurate audiendo consequi potui, hoc qualecunque compendium construxi”). For a general introduction to this treatise, see Thiele, “Breves in sphaeram meditatiunculae.” 132 Mercator, Meditatiunculae, fols. e7r/v: “Radiorum vero illos qui sidus ipsum secundum diametrum metiuntur, potentissimos esse: quippe qui plurimorum in se incidentium vi iuventur ac stimulentur: impotentiores vero qui extra diametrum positi sunt, ut qui minorem corporis arcum metientes, pauciorum iuventur influxum: infirmissimos vero & maxime imbecilles, qui ad contingentiam duntaxat laterum proijciuntur. Haec ad genuinam astrorum naturam spectant, at applicatio hanc ipsam quoque virtutem vel auget vel minuit pro ratione incidentiae radiorum in corpora subiecta: quod ex pueris pilam tractantibus cognoscere licet. Nam quemadmodum pila, si oblique in terram cadat, oblique etiam resultat, ac minus moratur, at si ad perpendiculum iaciatur, sursum fertur violentius, atque haeret diutius. Eodem modo 131

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4.7. Pico’s Disputations and planetary distances Chapter 3 showed that the core of Pico’s Disputations consisted of an argument for the explanatory autonomy of sublunary substances, and against astrology’s physical reductionism. The quintessential tools of this argument were Aristotelian naturalism (especially his use of the concept of pneuma) and astronomical data (which Pico applied to an optical model of celestial influence). We have previously found that Dee embraced both Pico’s interpretation of Aristotelian physics and the optical model of celestial influence in his Louvain years. How is it possible, then, that both men applied these same tools to argue respectively for and against astrology? The answer is contained in the one element that we have left out: astronomical data. Aristotelian physics enabled Pico to demonstrate that sublunary changes embodied cooperation between celestial and sublunary bodies. The optical model provided a means to describe this interaction quantitatively: the sublunary effect of a celestial body’s heat was determined by three parameters: size, distance, and angle of incidence on the terrestrial surface.133 The inability of Ptolemaic astronomy to determine the proportion of these three parameters enabled Pico to buttress his claim that the reality of planetary influence could only be demonstrated for sun and moon.134 This argument was problematized, however, by the systemic changes that Copernican astronomy introduced. It now became possible to derive the planetary distances with absolute certainty, and thus also to counter Pico’s argument against the reality of planetary influences beyond the sun and moon. An example: according to the medieval Ptolemaic values of Campanus of Novara,

radij illi qui oblique terram petunt, minus vehementes sunt, dum obiter praetereuntes terram contingant tantum, rursum qui directa ad perpendiculum in terram cadunt, potentissimi sunt, dum (non patente transitu) in seipsos reflecti coguntur, & haerent, & sic vires quodammodo duplicantibus bene intellectis facilis patet aditus in sequentia.” 133 Each of these elements are discussed in Dee’s Propaedeumata xxx–xxxii. Pico’s assumption of a converse relation between the size of the emitting surface and the intensity of the emitted light appears in Prop. xliii. 134 Disputationes, vol. 1, p. 230: “Tria enim fere facient intentionem caloris, magnitudo lucis, densitas et propinquitas. Non est autem ad liquidum exploratum quantum magnitudo densitati, quantum densitas magnitudini, quantum alteri vel utrique praeponderet ipsa propinquitas; quare ratiocinari volentibus in incerto res erit, nec arbitrari poterit sensus, cum praeter Solis et Lunae ceterorum radios non persentiat; et hoc primum obstat astrologis quorum ars nulla, si remanent in ambiguo vires caelestium radiorum.”

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the mean distance between the earth and Mars was 5,600 terrestrial radii. Saturn was about 3.5 times further removed, namely 19,400 terrestrial radii. Copernicus’ On the Revolutions, however, decreased the mean distance for Mars to only 1,700 terrestrial radii. Saturn was now 6.5 times further, namely 11,000 terrestrial radii.135 It is easy to see how this could affirm the old astrological maxim that Saturn imparted cold influences, and Mars hot ones, which Pico had disputed on the basis of the Ptolemaic data.136 Copernican astronomy could easily have been perceived as an aid in the refutation of Pico’s Disputations.137 This does not imply that Louvain mathematicians suddenly converted to Copernicus’ heliostatic beliefs: we have seen that Gemma Frisius did consider the merits of a translation to the old geostatic framework. Neither did they slavishly adopt Copernicus’ astronomical data. The appreciation of Copernicus’ work at Louvain was strongly linked to his use of Ptolemy’s observational and mathematical methods to correct astronomy. His improvements on Ptolemy were ascribed to the fact that On the Revolutions could draw on a longer range of observations.138 Their superiority, however, did not imply their correctness. In 1561, Gemma’s son Cornelius Gemma wrote that Reinhold’s Copernican tables were superior to the old Alfonsine ones, although the new predictions often provided wrong predictions for Mercury and Mars.139 Uncertainty about the Copernican data for each individual parameter in the optical model, as well as the physical interpretation of these parameters, called for a further program of astrological research. 135 These astronomical data were borrowed from the table in Dee, Propaedeumata, p. 87. 136 Disputationes, vol. 1, pp. 230–232. 137 The relevance of planetary distances to astrological criticism was also defended by Louvain participants in the 1524 debates. Cornelius Scepper argued against the supposed influence of the fixed stars by referring to the ratio between their size and distance. Although the fixed stars were at least, Scepper wrote, 702 times larger than the moon, they were also 65,357,500 miles removed from the earth. Scepper’s value for the size of the fixed stars seems to be derived from Alfraganus’ estimate for stars of magnitude 6 in his popular textbook Elements, translated by Gerard of Cremona. See van Helden, Measuring the Universe, 29–31. In Scepper’s opinion, this distance necessarily impeded any possible influence of the fixed stars. See Scepper, Assertio fidei, fols. 25v-26r. 138 Gemma Frisius, De radio astronomico, fols. 29v-30r: “Est enim huius rei pertractatio apud Claudium Ptolomaeum, ac in tabulis Peurbachii, aliisque multis, omnium autem emendatissime apud Copernicum. Qui sua observata cum priorum traditis conferens, ex longiori elapso spacio multa emendavit, quae prioribus ob angustiam temporis percipi non poterant.” 139 Cornelius Gemma, Ephemerides meteorologicae (1561), fol. a3r.

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Rooted in his earlier work at Louvain, Dee’s Propaedeumata provided a complete outline of this program, including various methods for “number crunching.”

5. Astrological reform and the emergence of scientific realism Nicholas Jardine convincingly argued that the reception of Copernican astronomy in the sixteenth century was often dominated by a position of “pragmatic compromise” between natural philosophy and mathematical astronomy. This position postulated (1) doubt, or even denial, concerning the reality of existing astronomical models, as well as (2) a strict distinction between the proper concerns of both disciplines.140 Turning back to Gemma Frisius’ remarkable letter on Copernican astronomy (1555), we find element (1) fairly intact. This document neither denied, nor categorically asserted, the reality of the Copernican model.141 In the end, the pragmatic concern to save the empirical phenomena dominated Gemma’s support of both the improved observational basis of Copernican astronomy and certain “systemic” features like the earth’s double motion. It was argued that this development was intimately linked to the local impact of Pico’s Disputations at Louvain. An important component of its astrological critique concerned the problem of celestial distances, which Pico emphasized through an optical model of celestial influence. Several members of Gemma’s mathematical familia (Dee, Gogava, Mercator) in turn cultivated this optical model as a high road to astrological reform. Traditional knowledge of the angular positions of celestial bodies no longer warranted the “truth” of astrological and astronomical practice at Louvain. The diameter and terrestrial distance of celestial bodies now came to supplement these pragmatic “truth conditions” of astronomical theory. As a result, Louvain mathematicians like Gemma Frisius eagerly discussed and defended the more spectacular claims of Copernican astronomy.142

140 I borrow the notion of “pragmatic compromise” from Jardine, The birth of history and philosophy of science, pp. 237–243. 141 Cf. Machamer, “Fictionalism and Realism”; Barker/Goldstein, “Realism and Instrumentalism.” 142 Apparently, Gemma Frisius accorded relatively little weight to specifically antiCopernican theological objections. This was not impossible in the sixteenth century: cf. Navarro Brotóns, “The Reception of Copernicus.”

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Judged by the standards of its own time, we find that Gemma Frisius’ self-confident undermining of element (2) was no less spectacular. Gemma emphatically described how Copernican ephemerides were based on “theses that are quite alien to the common opinion of the philosophers.”143 He claimed that the critics of heliocentrism “lack both philosophy and the method of demonstration,” and publicly suggested that the principles of the Copernican model were “not entirely absurd, but conform to nature” (see section 4.2). Accordingly, he described how the Ptolemaic model was “rather absurd” in at least two respects.144 How should we interpret Gemma’s assertivity about his prerogative to discuss (higher) philosophical concerns? In my opinion, Gemma did not seek to profile himself as a natural philosopher, but simply claimed the mathematician’s right to take up these concerns with his own tools. His letter to Stadius predominantly predicated “truth” of mathematical propositions, but used a restricted notion of “cause” as “sufficient condition.”145 Jardine previously identified three developments underlying such erosion of the “pragmatic compromise” in the late sixteenth century: the study of the locations of celestial bodies (i.e., comets and new stars) in the 1570s, the weakening of traditional natural philosophy, and the increasingly non-academic contexts of astronomical practice.146 The available evidence shows each of these elements in place at Louvain in the 1540s, more than half a century before Kepler composed his famous Apologia (1600), which borrowed Gemma’s arguments for heliocentrism.147 In the next chapter, I will relate this local obfuscation of the boundaries between mathematics and natural philosophy to a broader cosmographical project, outlined by Gemma’s pupil Gerard Mercator in the context of astrological reform. This suggests that Louvain astrology must be accorded an important place along the road leading to the “forging of modern realism.” More important than this “priority issue,” however, is the following point. The Louvain context strongly suggests that the extension of criteria for the resolution of conflict between astronomical theories 143

Stadius, Ephemerides (1585), p. 1. Ibid., p. 2. 145 Cf. Jardine, “The Forging of Modern Realism,” p. 145, note 13. 146 Jardine, The birth of history and philosophy of science, pp. 246–247. 147 Ibid., p. 141. On the increasing mathematical prerogatives towards traditional natural philosophy at Louvain in the 1540s, see Vanden Broecke, “Humanism, Philosophy, and the Teaching of Euclid.” 144

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beyond observational success (i.e., the emergence of realism), did not result from the presence of this conflict in certain sixteenth-century astronomical communities as such. Instead, it arose from a more fundamental attempt to practice astrological reform.

CHAPTER SEVEN

PTOLEMY, PARAPEGMATA, MATHEMATICS, AND MONSTERS. THE REFORM OF MUNDANE ASTROLOGY

We recall how the 1524 debates led astrological reformers to advocate a Ptolemaic practice that favored eclipses and lunar phases in mundane astrology. Two motives propelled this methodological shift. On the one hand, it provided rhetorical justification for a lack of public specificity about the future. It enabled court practitioners to distance themselves from the highly competitive world of printed prognostications, and to organize their public practice around suggestions of their private capacities in the service of the prince. Although some prognosticators like the Laet family successfully imitated the new methodological shift, they could not afford to combine this with an equally elaborate form of social secrecy. On the other hand, Ptolemaic practice illustrated the results that could be obtained from the practice of astrological reform. Ptolemaic practice provided a model where astrological physics claimed to control judicial astrology with a firm hand. This created an unexpected new problem for court practitioners, as their urban competitors began to imitate Ptolemaic practice and its reformist discourse with remarkable ease. This could have eroded the hard earned right to a non-specific public narrative, had elite practitioners not exerted themselves in a further cultivation of astrological reform. In doing so, they managed to patrol the barriers, both linguistic and social, that distinguished them from urban prognosticators. This chapter presents four Louvain examples from the realm of mundane astrology. Interestingly, these four cases mirror the double nature of Louvain astrological interest in Copernican astronomy (chapter 6). In the first two sections, we encounter astrological practitioners who emphasized the reform of judicial astrology, mainly by uncovering and purifying ancient methods of weather prediction. This is followed by a study of two other projects that focused more on astrological physics. These differences were not absolute or clear-cut, however. To a much greater extent than traditional academic astrology, reformed practices and theories were dependent on one another to

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demonstrate their respective value.1 In this respect, they resemble the development of sixteenth-century medical practica, many of which became more philosophical in an attempt to elucidate the theoretical basis of therapeutical practices.2

1. Ptolemy, politics, and prognostication. Cornelius Gemma’s Ephemerides (1561) One component of astrological reform in Gemma Frisius’ familia was centered on the public restoration of ancient Ptolemaic practice. Our first example comes from Cornelius Gemma (1535–c. 1578), Gemma Frisius’ oldest son. After Latin studies in Mechlin, Cornelius began his studies at the Louvain arts faculty when he was fifteen. He continued at the medical faculty, succeeded professor Nicolas Biesius in 1569, and obtained the doctorate in 1570. Cornelius Gemma died around 1578 in the plague epidemic that claimed a third of the Louvain population.3 Having edited his father’s posthumous De astrolabo catholico in 1556, Cornelius Gemma started publishing his own work around 1560, with a series of annual Ephemerides meteorologicae.4 Printed by Joannes Withagen, they supplemented a respectable publisher’s list with a strong emphasis on mathematical and medical works in both Latin and the vernacular.5 This section will focus on the Ephemerides for 1561 as an example of the new direction that the practice of mundane astrology took at Louvain.

1 One symptom of this new development is an increasing concern to connect astrology with physica. See the Artis divinatricis (…) encomia & patrocinia (1549), where Melanchthon claims that divinatory astrology is physical (f. h1v), and where Milichius identifies astrology as a part of physica (f. i4v). 2 Wear, “Explorations in renaissance writings,” p. 123. 3 On Cornelius Gemma’s biography, see especially Van Ortroy, Bio-bibliographie, pp. 124–126. Previous studies of his work include Céard, La nature et les prodiges, pp. 365–373; Hallyn, “Un poème sur le système Copernicien”; Mulsow, “Seelenwagen und Ähnlichkeitsmaschine”; Secret, “Cornelius Gemma et la prophétie”; Van Nouhuys, The Age of Two-Faced Janus. 4 See Van Ortroy, Bio-bibliographie, pp. 367–374. Cornelius Gemma’s Ephemerides are extant for the years 1561 to 1564. In the Ephemerides for 1561, Cornelius refers to a prediction that he made the year before. It is unclear whether this was published or not. See Gemma, Ephemerides (1561), fol. d7r. 5 Withagen published, among others, De conservanda bona valetudine (1557), prognostications by Boileau de Buillon (1558, 1559, 1562), Apianus’ Cosmographia (1561, 1564, 1573, 1574, 1575, 1581, 1584), a Flemish version of Piemontese’s book of

ptolemy, parapegmata, mathematics, and monsters 187 Two things stand out upon inspection of Cornelius Gemma’s Ephemerides. First, there is ample evidence of a strained relationship with political and ecclesiastical authorities. On the penultimate page, we find a declaration, signed by the Antwerp priest Sebastian Baers, that “This does not contain anything which is contrary or offensive to the peace of the Roman Church or the State; hence, it can be admitted.”6 To my knowledge, this makes it the earliest astrological work from the Low Countries bearing an ecclesiastical imprimatur. Second, we find a remarkable change in format with respect to traditional annual prognostications. Even Albert Pigghe, nemesis of the prognosticators in the 1524 debates, structured his Ptolemaic predictions around the traditional format of annual prognostications. These contained a methodological introduction, followed by brief chapters on the state of the four seasons and each of the twelve months in the following year. Then came predictions of harvests, diseases, wars, as well as differentiated medical prognoses, depending on one’s predominant zodiacal sign. Last but not least, sixteenthcentury annual prognostications habitually provided specific predictions of the imminent fate of countries, cities, and rulers. The actual prognostication could also be combined with a brief almanac (see chapter 2). Cornelius Gemma offered little or none of this in his Ephemerides. Only after the main section of his tract (49 pages) did he discuss traditional prognosticatory concerns, and then only for five pages. He was adamant about his motives in the introduction to this part: I have decided (…) to extirpate the old way of writing in this place (…). But in order to satisfy masses that are avid to learn of new things, I will say as much as I can without [incurring] envy, or detriment to my name. For that which concerns kings and the casual state of public matters, is no part of our art or intention, as I have said before. In my calculations for last year, I wrote down some things that imitated the ineptitudes of others. This was due to the impetuosity of my juvenile soul, and not to the guidance of prudent advice. For this reason, we may have missed certain things, and above all presented many things that relied on sheer luck, instead of secure reasoning.7

secrets (1562) as well as Lemnius’ Occulta naturae miracula (1564), Cornelius Schylander’s Medicina astrologica (1570, 1577) and a number of geographical tracts. 6 Gemma, Ephemerides (1561), fol. e3r. 7 Ibid., fol. d7r: “Statueram hoc loco, (…) veterem scribendi consuetudinem extirpare (…). Ut tamen novarum rerum avido vulgo faciam satis, dicam quae maxime potero citra invidiam, & nominis mei detrimentum. Nam quod ad reges attinet, & publicarum rerum fortuitos casus, nec artis esse nostrae neque propositi dixi dudum.

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Apparently, Cornelius Gemma’s lost prognostication for 1560 contained certain political predictions that were badly received. Like his predecessors in 1524, Cornelius attempted to restore trust through public methodological innovation in his installment for 1561. Interestingly, the preface of the Ephemerides claimed that it intended to lead the populace away from the error of predicting from “tables that are inspected only once, or the chart of a single new moon.”8 Predictions based on the chart for the new moon were a typical Ptolemaic procedure and hence well respected among many post-1524 prognosticators. Cornelius Gemma displayed a significant lack of interest in these previous methodological reforms. To him, the problem was not which data prognosticators used, but how much data they considered significant. A radical increase in the amount of relevant data was intended to neutralize three quintessential problems of contemporary astrology: astronomical inaccuracies, a multiplicity of concurrent causes, and an incomplete knowledge of the elementary constitution of different terrestrial regions.9 Cornelius Gemma’s predictions assiduously studied every lunar phase for 1561, as well as most planetary aspects and the phases of the fixed stars with respect to the sun, thereby surpassing any competitor in thoroughness. The second novelty of the 1561 publication was its restriction to weather predictions, which occupied over 90 % of the Ephemerides. Cornelius Gemma wrote that he restricted himself to “the narrow orbit of my art, so that I do not seem to trick the task when I am able to predict, more accurately than others, the climate of the heavens and the quality of the surrounding air.”10 This shows that Louvain astrologers gradually came to voice new public claims about predictive accuracy for a more restricted domain of discussion: the weather. Similar developments in natal astrology will be discussed in chapter 8. Like his predecessors, Cornelius Gemma presented this change as a restoration of ancient Ptolemaic practice; whether this was the

Scripsi quaedam obiter anni superioris calculo, in quibus multorum ineptias imitabar, sed impetus potius iuvenilis animi, quam prudentis consilij ductu, quare ut in nonnullis falsi fortasse fuimus, multa quoque coniecimus, non tam rationibus certis quam foelici quadam temeritate subnixi.” 8 Ibid., fol. a4r: “(…) vel semel tantum inspectis tabulis, vel unius novilunij fabricato schaemate, (…).” 9 Ibid., fol. a3v. 10 Ibid., fol. d7r/v: “(…) memet deinceps artis meae angusto circulo continebo, ut non omnino operam lusisse videor, si accuratius paulo quam caeteri temperiem coeli, & aëris circunfusi qualitatem augurari possim.”

ptolemy, parapegmata, mathematics, and monsters 189 case, depended on the part of Tetrabiblos that one chose to focus on. Ptolemy had arranged the chapters of his book on mundane astrology according to the specificity and precision of the predictive techniques that they discussed. The initial chapters (ii.2–3) contained a general “astrological chorography” of terrestrial regions. Then followed a detailed treatment of eclipses and their effects (ii.5–8), which could last several years and affect large regions of the earth. The following step was to study the soli-lunar syzygies that initiated each season of the year (ii.10). This had become quite common in sixteenth-century annual prognostications, as had the monthly investigation of new or full moons (ii.12). Less common, however, were the other lunar phases, which Ptolemy recommended as “more minutely detailed indications,” as well as the planetary “applications and recessions.” The same goes for the “day by day intensifications” that were produced by the phases of the fixed stars (ii.12).11 Cornelius Gemma’s annual ephemerides provided a practical adherence to chapter ii.12 of Tetrabiblos, with which they replaced the more common emphasis on chapters ii.2–11 in post-1524 annual prognostications. The ensuing narrative provided a steady enumeration of daily weather changes to replace the more traditional list of meteorological, economical, political, and religious predictions on an annual, seasonal, or monthly basis. This brings us to the third and final characteristic of Cornelius Gemma’s ephemerides: an increased attention for the theoretical underpinnings of astrological practice. Although Gemma’s ephemerides were part of the tradition of judicial astrology, its predictions consistently included equally detailed causal explanations. For instance, Gemma predicted a general change towards more humid weather on 15 January 1561, which was first brought on by a southern breeze, and later by a northern wind. He also specified that there would be snow in some places, and more strong winds in others, beginning on the 18th or 19th and intensifying on the 20th. In a separate column, he explained that: Leo 10° was in the ascendent [in the chart of the new moon on the 15th], with Jupiter almost in midheaven and Mercury on the western horizon. Since Mercury and Saturn dominate [this chart], with Mercury standing beneficially under the rays of Saturn’s light –in mutual reception-, one should not doubt that this face of the heavens (…) will bring forth winds in some places and plenty of snow in others. The quartile aspect of Mars and Venus [on the 17th] (…) signifies a remission of the cold. 11

Tetrabiblos, pp. 209–211.

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chapter seven The conjunction of Sun and Mercury (…) signifies winds around the 20th, unless retrograde Saturn in trine to Mercury hinders this.12

The differences with traditional prognostications are clear when we look at Gaspar Laet jr.’s prediction for the weather around 15 January 1561: New moon on the 15th [of January] at 6 pm. Saturn dominates: an icy cold, windy for a short period.13

Other Louvain graduates started to express similarly strong reservations about annual prognostications in the 1550s. A good example is Livinus Lemnius (1505–1568), who began to study the arts and medicine at Louvain in 1521. He may have obtained a doctorate in medicine in Italy around 1526 before becoming town physician in his native Zierikzee (Zeeland), where he remained until his death.14 In 1554, Lemnius dedicated a treatise De astrologia to Cornelius van Weldam, a counselor to Charles v, and a number of local noblemen and politicians from Zierikzee.15 Lemnius recounts how these patrons had repeatedly beseeched him for annual prognostications “in the common way,” supplementing the medical almanacs that he habitually composed.16 Lemnius dismissed these requests as harmful to piety, morals, and the respublica and instead decided to write a treatise on licit astrology.17 Publicizing the errors of a patron’s wishes was so uncommon in book dedications that we may accept Lemnius’ version of the facts. Lemnius accused common practitioners of pushing their art towards unwarranted specific predictions. He did, however, believe in the truth of the art’s basic tenets.18 This was sanctioned by Scripture19

12 Gemma, Ephemerides (1561), fols. a6v-a7r: “Adscendens 10 [Leonis], [Jove] Fere in culmine M[edii] C[aeli], [Mercurio] in finitore occiduo. Dominantur [Mercurius] [Saturnus], & [Mercurius] sub radijs adhuc foecundus Saturni lumine, cum receptione mutua, ut dubium non sit quin haec coeli facies (…) alibi ve[n]tos paritura sit, alibi copiosas nives interim. Quadratus [Martis] ac [Veneris] (…) frigoris remissionem fore significat. [Conjunctio] [Solis et] [Mercurii] (…) ventos circa 20 diem fore significat, nisi quid obstet [Saturnus] retrogra[dus] in [triangulo] [Mercurii].” 13 Laet, Prognostication (1561), fol. a3r. 14 For bio-bibliographical data on Lemnius, see Van Hoorn, Levinus Lemnius. His most important work, the Occulta naturae miracula, is discussed in Margolin, “Vertus occultes et effets naturels”; Eamon, Science and the Secrets of Nature. 15 Lemnius, De astrologia, fol. a2r/v. 16 Ibid., fol. a2v. 17 Ibid., fol. a3v. 18 Ibid., fol. 8r. 19 Ibid., fol. 11r.

ptolemy, parapegmata, mathematics, and monsters 191 and the economy of Creation,20 and had been developed through experience of the effect of certain fixed stars, the sun, moon, and even some zodiacal signs, by mariners, farmers, and physicians.21 The company of mariners, farmers and physicians leads us right back to Ptolemy, who invoked the predictive knowledge of such practitioners as both empirical basis and theoretical model for his own astrology (chapter 1), as Pico was to do after him. Did Louvain practitioners begin to advocate a restoration beyond Ptolemy, a return to Cicero’s “rational” founts of ancient astrological practice? The next section explores this important question.

2. Parapegmata and popular errors. Joannes Stadius’ De fixis stellis (1560) Joannes Stadius was born at Loenhout (Brabant) in 1527 into a family of successful farmers.22 He may have taken lessons at the nearby Latin school of Hoogstraten and probably studied at Louvain, although he never seems to have taken a formal degree.23 Gemma Frisius’ introduction to Stadius’ Ephemerides (1556) expresses their familiarity with one another, while in his Tabulae Bergenses (1560), Stadius claims that he “was also aided, over four years ago, by the observations [of Regulus] of that excellent man Gemma Frisius.”24

20

Ibid., fol. 11v. Ibid., fols. 12r-21v. 22 This biographical account of Stadius is based on Ernalsteen, Joannes Stadius Leonnouthesius, pp. 5–15. 23 Stadius observed the lunar eclipse of 8 December 1554 in the presence of the praetor Torino, Walter Echelpoel, “a trustworthy and most diligent man.” See Stadius, Ephemerides (1556), fol. g3r: “Observavimus nos teste praetore Torino Gualtero Echelpolio, viro incorruptissimo & diligentissimo.” Although I have not found any other reference to Echelpoel, Dr. Leo Van Buyten (K.U.Leuven) informs me that “echel” is Louvain dialect for “leech,” while Torinus might refer to the nearby village of Tourinnes-la-Grosse. My interpretation of Torinus as Tourinnes-la-Grosse, rather than the Italian city Turin, is also suggested by Stadius’ remark that he returned from Antwerp to “Torinus” on 19 August 1554 (Stadius, Tabulae Bergenses, p. 203). In his Ephemerides (1556), Stadius refers to the physician Jean Dubois (Joannes Sylvius) as his witness in a priority dispute with Cardano. In connection to Stadius, we know that Dubois studied medicine at Louvain in the 1550’s, where he also published his De lue venera declamatio (Louvain, 1557). See Hoefer, Nouvelle biographie générale, vol. 14, pp. 855–856. Stadius’ contemporary Joannes Molanus included him among the scriptores mathematici of Louvain. See Molanus, Historiae, ed. De Ram, vol. 2, p. 579. 24 Stadius, Tabulae Bergenses, p. 187: “Adiuti quoque ante quadriennium optimi viri Gemmae Frisij observationibus.” 21

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This shows that Stadius may be considered a member of Gemma’s mathematical familia. In the beginning of 1554, we find Stadius in Antwerp. From 1556 onwards, Stadius frequently resided at Brussels, where he made many of his astronomical and astrological observations. His mathematical proficiency earned him a place at the court of Robert de Bergues, Prince Bishop of Liège (1557–1563), at the end of the 1550s. Stadius returned to Louvain in 1565, succeeding Petrus Beausardus as holder of the new public chairs of mathematics and ancient history. In 1576, he obtained a teaching post in mathematics at the university of Paris, where he died in 1579. 2.1. Stadius’ restoration of ancient parapegmata In early 1560, Stadius published a set of astronomical tables at Cologne. He audaciously imitated the Alfonsine tables by naming this user-friendly compendium of Reinhold’s Prutenic Tables (1551) after his patron Robert de Bergues. The letter of dedication clearly emphasized the astrological relevance of the Tabulae Bergenses, claiming that the light of each celestial body was endowed with a particular power to animate the seeds of things. Stadius also emphasized the “Copernican” discovery of a decrease in solar eccentricity, providing astronomical content to the biblical prophecy of a final conflagration.25 The Tabulae Bergenses were also presented as a contribution to judicial astrology. Its reorganisation of “Prutenic” material intended to provide easier calculation of celestial motions for any point in time; its history of astronomy was constructed around the calendar problems that figured prominently on the agenda of the Council of Trent (1545–1563); its treatise on the fixed stars promised an exposition of foreknowledge about diseases, sterility, or tempests in any particular year.26 This last treatise, entitled De fixis stellis, is central to our present concerns. It was directly inspired by an ancient astronomical genre called parapegmata. Parapegmata constitute the oldest extant genre of Greek astronomy and astrology.27 They were perpetual lists of the heliacal risings and settings of the fixed stars (fixed star phases), 25

Ibid., fols. a2r-a3r. Ibid., fol. a3v. 27 See Rehm, “Parapegma.” A more general interpretation of the historical position of parapegmata is Goldstein/Bowen, “A New View of Early Greek Astronomy.” 26

ptolemy, parapegmata, mathematics, and monsters 193 written for specific latitudes. These lists provided the times of the year at which specific fixed stars first emerged from being invisible under the sun’s light, i.e., when they were first seen to rise just before sunrise, or to set just after sunset. Parapegmata usually provided astronomical and astrological data, including weather predictions, on a day-to-day basis. Many ancient literary authors incorporated material from parapegmata for their own purposes. Stadius in turn extracted this semiagronomic material from authors like Varro, Virgil, or Pliny to build his own catalogue of meteorological precepts. Renaissance readers read Roman encyclopaedias or didactic poems for their literary qualities, but also as repositories of factual information. It was assumed that these literary genres would disclose the way in which the ancients did things or thought about things, if adequate text criticism was applied.28 In the case of Virgil’s Georgics or Pliny’s Natural History, it was assumed that these texts reported tacit knowledge of ancient farmers. 2.2. Medical astrology in sixteenth-century Louvain Equally important were the Hippocratic, and to a lesser extent, Galenic texts, which supplied Stadius with further information on the sublunary effects of fixed stars.29 This created an interesting dialogue between astrology and the medical category of “non-naturals.” Following Galen (c. 129–200), scholastic medicine commonly distinguished three categories of physiological entities: naturals, nonnaturals, and contra-naturals. By the term res naturales, physicians denoted basic components of the ordinary bodily functions, especially complexions, humours, bodily parts, and functions.30 Contranaturals stood for all pathological conditions. The intermediary category of non-naturals grouped six elements: air and water, food and drink, repletion and excretion, motion and rest, sleep and waking, and emotions.31 “Air and water” was the main point of entry for astrological knowledge into early modern medicine. In the sixteenth century, Louvain physicians became increasingly uncomfortable with the astrological components of their trade. Our earliest indication comes from Hubertus Barlandus, who expanded 28 29 30 31

See Ludwig, “Neulateinische Lehrgedichte.” Stadius, Tabulae Bergenses, pp. 201–202. Siraisi, Medieval and Early Renaissance Medicine, pp. 100–109. Jarcho, “Galen’s Six Non-Naturals”; Bylebyl, “Galen on the Non-Natural Causes.”

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and republished the Epistolae medicinales of Giovanni Mainardi, one of the original editors of Giovanni Pico’s Disputations, in 1529.32 In a letter that Mainardi wrote at Mirandola in 1500, he thoroughly attacked any use of astrology in medicine.33 In his dedication to the medical students of Louvain, Barlandus strongly emphasized the importance of mathematics for true physicians, even if this went against the opinion of Mainardi.34 In a fuzzy re-enactment of Galen’s defense of the ancient rational sect of medicine, Barlandus claimed that neglecting mathematics was tantamount to neglecting natural reason.35 Medical astrology was a perfectly laudable pursuit, which Mainardi had unjustly criticized.36 Other protagonists of Louvain medical humanism shared these concerns. Following a coup against the scholastic faction in the medical faculty, Gemma Frisius’ friend Hieremias Thriverus (1504–1554) became medical professor in 1543.37 Around 1547, his pupil Willem Pantinus (d. 1583) started studying Celsus’ De re medica, which he publicly taught around 1550.38 His published commentaries on Celsus contained some illuminating remarks on medical astrology.39

32 On Mainardi, see Atti del Convegno (…) di Giovanni Manardo; Nutton, “The Rise of Medical Humanism: Ferrara 1464–1555.” Hubertus Barlandus (d. after 1 August 1544) was a cousin of the famous humanist Hadrianus Barlandus. He studied under Vives, Jan Becker, Adrianus Barlandus, and possibly Erasmus, and pursued medicine in the first half of the 1520s. He perfected himself in this last discipline at Paris and Montpellier, and travelled to Italy and the upper Rhine-valley before settling as a physician in Namur in 1531. In 1533, he became personal physician to Adolf of Burgundy. Barlandus became the self-appointed thorn in the side of Louvain scholastic medicine in his Velitatio of 1532, having inaugurated this role with the dedicatory letter that preceded his Mainardi edition. See De Vocht, History, vol. 2, pp. 518–524. 33 On this letter, see the study and edition of Zambelli, “Giovanni Mainardi e la polemica sull’astrologia.” 34 Barlandus, Epistola, fol. a2r. 35 Ibid., fols. a2v-a3r. 36 In a letter to Erasmus, written on 30 December 1528, Barlandus even declared his intention to travel to Tübingen and study mathematics under Joannes Stöffler. See Erasmus, Opus epistolarum, ed. Allen, vol. 7, p. 2081:6–10. 37 See De Vocht, History, vol. 2, pp. 537–538. For a general (but incomplete) overview of Thriverus’ career and writings, see Van Hee, “Jeremias de Drijvere.” 38 Most chronological indications regarding the life of Pantinus need to be puzzled out of the biographical data he provides in his published commentary on Celsus. See De Vocht, History, vol. 3, pp. 333–334. My chronology is based on the data given by De Vocht, but is further specified by Pantinus’ settlement at Bruges, having been promoted licentiatus, around 1552. 39 Celsus, De re medica, ed. Pantinus (1552).

ptolemy, parapegmata, mathematics, and monsters 195 While explaining a Celsian paraphrase of Hippocrates’ Aphorisms iii.9, Pantinus emphasized that notable weather changes, along with important celestial configurations, were very important in medicine.40 Pantinus refrained from treating them thoroughly, however, “so that I would not seem to state alien matters among those who seek glory under this banner of vaticination.”41 Astrology inspired Pantinus with distrust, because its practitioners aimed at supplanting the conclusions of other specialists like politicians or mariners.42 Pantinus’ oblique references to vaticination or political astrology remind us of the world of annual prognosticators. The examples of Cornelius Gemma and Livinus Lemnius in section 1 showed that this fear of being associated with the prognosticators was quite common in the 1550s. Pantinus opposed the appropriation of medical themes by the prognosticators, choosing not to discuss the topic thoroughly to avoid the risk of being associated with them. Louvain humanist physicians shared an astrological problematic with the local mathematicians through the role of air as a nonnatural. The fact that astrological influence was only part of one of six non-naturals, and therefore concurrent with a wide variety of other diagnostic and prognostic signs, softened the impact of this problematic on medical practice.43 Nicolaus Biesius taught this attitude to the Louvain medical students in the 1550s and early 1560s.44 When faced with the same problem, the Italian physician Girolamo Cardano chose to consider only two non-naturals: changes in diet and exercise.45 Although Hieremias Thriverus’ De temporibus (1535) treated the correct timing of medical therapy, virtually no role was laid out for the stars.46 40 Celsus, De re medica, ed. Pantinus, p. 148: “Possim hic multo longior esse, si & medicum quid deceat, & quid omnes mortales ex aere coeloque in corpore bene gubernando, animadvertere & observare oporteat, ostendere velim. Nam & temporum aerisque graves & magnae mutationes & concursiones siderum pleraeque excellentes atque constitutae, tantam vim, quantam verbis exprimere non facile sit, omnino obtinent (…).” The commented passage was Celsus, De medicina ii.1,1: “Igitur saluberrimum ver est, proxime deinde ab hoc hiems; periculosior quam salubrior aestas, autumnus longe periculosissimus.” 41 Ibid., p. 148: “(…) non aliena, quibusdam qui hoc vaticinandi nomine potissimum & nomen & gloriam consectantur, dixisse videar.” 42 Ibid., pp. 147–148. 43 Compare with Bazin, “Considérations sur l’air”; Nicoud, “Diététique et saisons.” 44 See Biesius, De methodo medicinae (1564), fols. 31r-32v. Biesius classifies the nonnatural category of air under the external antecedent causes. Compare this to Hankinson, “Galen’s Theory of Causation.” 45 See Siraisi, The Clock and the Mirror, pp. 130–131. 46 Thriverus, De temporibus (1535).

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Still, medical humanists actively advocated solutions to the astrological issue. In 1542, Thriverus dedicated a book of physical and meteorological Paradoxa to Cornelius de Scepper, one of the protagonists of the Louvain 1524 debates.47 One of Thriverus’ paradoxes concerned the Aristotelian interpretation of wind as a hot and dry exhalation. Instead, he proposed to interpret this phenomenon as air that is moved by the stars. Through common experience, Thriverus suggested that celestial bodies imparted variable coldness or heat while moving wind and rain. He added that: We will leave the rest to the astrologers, whose task it is to distinguish the stars that generate and move the winds, with their name and designation. They should also explain the signs that announce the northern or southern [winds].48

2.3. Particular experience and ancient authority The connection between medicine and weather prediction was an important component of Louvain astrological reform. According to the testimony of his son Cornelius, Gemma Frisius had kept two observational journals. One contained “his experience in the entire medical art,” while the other offered “a report of everything that pertained to the position of the stars as well as to the daily mutations of the atmosphere.”49 Stadius took Thriverus’ recommendations to heart, since chapters vii to x of De fixis stellis were packed with precepts like: The star Arcturus does not rise without a boisterous hailstorm.50

47 Thriverus, Paradoxa (1542). Thriverus’ title refers to the ancient genre of paradoxography, from which his book is distinguished by the fact that it does not aim at collecting mirabilia as such, but rather uses these to discuss natural-philosophical issues. See Romm, The Edges of the Earth, pp. 92–93. 48 Thriverus, Paradoxa, fol. a6v: “Reliqua astrologis relinquimus, quorum officium est astra quae ventos gignunt, moventque sigillatim ac nominatim distinguere, sed & horum est signorum quae boream aut austrum praenuntiant, rationem enarrare.” 49 Gemma, Ephemerides (1561), fol. a2r. 50 Stadius, Tabulae Bergenses, p. 200: “Arcturi sidus non sine procellosa grandine emergere (…).” This is taken from Pliny, Nat.Hist., ii.106. Note that ancient parapegmata seldomly posited a causal relationship between the rising of fixed stars and weather changes.

ptolemy, parapegmata, mathematics, and monsters 197 Or: Spica in Virgo with [Jupiter] promises an ecclesiastical dignity.51

Such experiences were presented as restorations of the ancient parapegmata tradition. But how did Stadius validate them? How did he convince readers that his attempt at astrological reform was indeed reliable? This calls for a more detailed examination of the wealth of weather reports that we find in De fixis stellis. Consider the following examples: And nothing could be taught more profitably than the prophecy [vaticinium] of Diaphanes, if one investigates the sign of the moon when concealed Sirius rises with the sun. For if the moon then (…) passes through Sagittarius, [the weather will be] rainy. This is also the case for Capricorn, as the memorable year 1555 demonstrated with strange, stormy showers and winds at the time when the Dogstar rose.52

Or: In the year 1552, on the 13th day of January, when [the north-west wind Caurus] ruined many buildings, knocked down a great number of trees, frightened everyone with thunder, lightning, and a storm that raged and intensified for 18 hours, impelling the Scheldt to such swelling that it poured out beyond its banks, with ships being partly landed, partly mangled by the collision, and inflicting enormous damage; at that time, the sun set with Mercury and Mars, the star of Aquila was concealed, while Jupiter rose from the opposite side with Procyon and Sirius, along with the moon in opposition to Saturn. Can you see now, that tempestuous stars are mixed with tempestuous planets everywhere?53

Stadius’ recollections literally brought his astrological claims home, to the Duchy of Brabant and the local elite he associated himself

51 Ibid., p. 210: “Spica virginis eadem cum eodem [Iove], & Ecclesiasticam dignitatem praesignificat.” 52 Ibid., p. 202: “Tum etiam Diaphanis vaticinium si de Lunae quod obtinet signo, quum Sirius occultatus cum Sole exoritur, exploratum esset, nihil commodius tradi poterat. Si namque Luna (…) Sagittarium [permeabit] pluviosam [tempestatem], ut Capricornum, cuius exemplum praebuit annus 1555 mira flatuum & pluviarum circa Canis ortum intemperie memorabilis.” 53 Ibid., pp. 203–204: “(…) Annus 1552 ipso Ianuarij decimotertio die, quum tot aedificia everteret, arborum ineffabilem multitudinem sterneret, fulgure & tonitru universos perterrefaceret, seviente & increscente semper ad 18 horas tempestate, Scalden tanto aestu impulerit ut supra littora effusum, navibus partim excussis, partim collisione laceratis, inaestimabile damnum dederit [Chorus]: Sol cum Mercurio & Marte descendebat, Aquila occultabatur, ex adverso Iupiter cum Procyone & Sirio oriebatur, & Luna cum Saturni diametro. Vides ubique tempestuosa sidera tempestuosis planetis permixta?”

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with. The local context of these anecdotes invited readers to trust Stadius’ competence as an astrological reformer. His teacher Gemma Frisius employed similar strategies in De radio astronomico et geometrico (1545), when he publicly reported astronomical observations that had recently been collected in a general climate of astrological concern (chapter 6). These issues were particularly important for Stadius, eager to gain patronage from the prince bishop of Liège and to secure his public status as a practitioner. Contrary to many urban prognosticators (see the Intermezzo), Stadius’ humanist rhetoric placed him under a strong obligation to subordinate his individual experience to the authority of ancient traditions. Most astrological narratives in De fixis stellis were organised around general precepts (“The seas are tempestuous when Sirius rises in the morning”) and their ancient sources. Stadius’ personal experience, on the other hand, indicated his “expertise,” the extent to which ancient parapegmatic traditions were in fact restored. The similarities with Peter Dear’s analysis of empirical discourse in the tradition of the “mixed mathematics” are clear.54 Both traditions provided descriptions of a limited number of particular experiences. Both traditions publicly validated these singular experiences through their agreement with common ancient practice.55 Both traditions included historical circumstances or witnesses in their description of singular experiences. Both traditions presented their particular experiences (“empirical data”) as tokens of trust in the common experience that they embodied. For predictive disciplines like astronomy and astrology, this included the future fulfilment of predictions based on shared and public precepts.56 2.4. Popular errors and the new Ptolemy Stadius’ experiences adopted a number of common strategies through which mathematicians established their expertise. But what exactly was Stadius’ expertise about? A fascinating anecdote in De fixis 54 Dear, Discipline and Experience, chapters 2 and 3. The same categories of analysis may be applied, for instance, to the novel representation of individual specimina in sixteenth-century herbals. See the comment by DaCosta Kaufmann, “Empiricism and Community in Early Modern Science and Art,” pp. 405–406. 55 A fine example is Stadius, Tabulae Bergenses, p. 200: “Arcturi sidus non sine procellosa grandine emergere, testis est cum Columella Plinius, id certissimum tunc esse signum, si Lunae aut Martis radijs adiuvetur, multa experientia confirmatum habemus.” 56 Dear, Discipline and Experience, pp. 59 and 95–97.

ptolemy, parapegmata, mathematics, and monsters 199 stellis brings us closer to an answer. As a farmer’s son and mathematician, Stadius was convinced that astrology could improve contemporary agricultural practices. In his student years, Stadius claimed, this conviction was further fed by the Arabic doctrine of astrological Lots, which allowed one to calculate a specific significator for any type of produce. While Ptolemy’s Tetrabiblos acknowledged only the Lot of Fortune, the popular Arabic textbooks of traditional prognosticators developed the doctrine in stupefying detail.57 This made it a popular target for astrological reformers like Albert Pigghe, who wrote in 1519: These prognosticators of ours also have the habit of predicting particulars on [the growth of] nearly any crop: wheat, winter wheat, oats, figs, wine, oil and all kinds of fruit, assigning particular Lots to the [ecliptic] circle. But this Lot we willingly leave aside for them [to use], since we teach astronomy, not sortilege. For judging these matters by means of those Lots or Parts, as they call them, is a manifest sortilege: they have neither a natural, nor an astrological basis. What can be judged on these things in a natural way is as follows. Let us determine the state of the air, especially for the coming summer, [which we found] earlier to be very hot and dry. From this, it will be necessary to predict good things for those crops that flourish in heat and drought, which is the case for oil, wine, and similar things. For this reason we say that the wine will be good, soft, well ripened and cheap next year. On the other hand, bad things are predicted for those crops that can only grow in more wet soil, such as oats, barley, many kinds of vegetables, pastures etc. From this we predict a future dearth of food for livestock.58 57 The Lots were points on the ecliptic, calculated through simple arithmetical operations on the longitudes of relevant planets, which were assumed to indicate the future state of a specific class of things. Chapter 6 of Albumasar’s popular Ysagoga minor defined 55 different kinds of Lots. My favorite is the “Lot of whether the rumor is true or false,” which is taken “from Mercury to the Moon, and the [degrees] are cast out from the Ascendent” (Albumasar, The Abbreviation, ed./trans. Burnett, p. 48). For another example of the ramifications of this theory, see Kennedy et al., “Al-Biruni’s Treatise on Astrological Lots.” 58 Pigghe, Astrologiae defensio, fol. 32v: “Solent & hi nostri prognosticatores de singulis fere terraenascentibus, particularia praedicere, de tritico, siligine, avena, ficubus, vino, oleo, & singulis particulatim fructibus, ex partibus, quas ipsi appellant, eorundem, singulis fructibus, partes singulas, in circulo assignantes. Sed hanc partem eis libenter relinquimus, quod non sortilegia, sed astronomiam didicimus. De his etenim rebus, per sortes istas, aut partes, ut ipsi dicunt, iudicare, manifesta sortilegia sunt, & quae nulla rationem neque naturalem habent, neque astrologicam. Quid autem via naturali de his rebus iudicari potest est eiusmodi. Invenimus habitum aurae, praecipue per aestatem futuram, supra modum ardentem fore, aestuosam & siccam. Qua e re bene ominari his terraenascentibus, quae caliditate & siccitate gaudent necesse erit. Cuiusmodi sunt olea, vina, & quae sunt huius generis. Ob id dicimus, vina, anno sequenti bona fore, dulcia, bene cocta, & vili satis precio.

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Stadius, by contrast, recalled how his confidence in Arabic astrology made him wager on the prediction of crops with his father, Petrus Stadius, “a simple but virtuous man,” who kept the popular habit of predicting harvests from the general conditions on specific days.59 Such youthful faith in the Lots was met with laughter when Stadius’ results turned out worse than those of his father.60 While investigating the causes of his father’s predictive success, he suspected that the phases of fixed stars played a crucial role. Following Ptolemy, he also became convinced that astrology would make better predictions if it encompassed more celestial causes. Stadius turned to the various aspects of the planets (especially conjunctions and syzygies) in the constellations, and found that his improved technique easily surpassed the precision of his father’s predictions.61 Stadius had recognized the venerable archetype of ancient “rational prediction” (Cicero) in his father’s agronomical rules of thumb. Precisely this ability to situate them in their ancient lineage enabled Stadius to improve on these common methods. Following Ptolemy, he regarded his father as a man who used correct methods without knowing the grounds of his predictive success. The emphasis on specific days of the year for the prediction of crops was correct, but failed to attribute this to the heliacal rising and setting of specific stars on those days. It was only after Stadius identified this hidden cause that he was able to supplement his father’s empirical rules with Ptolemaic astrological practices. This attitude is exceedingly similar to that of the court astrologers who attacked annual prognosticators in the 1524 debates. Stadius followed their Ptolemaic rhetoric when he referred to the astrological Lots as conjectures “devoid of causal explanation” (ˆναÝτιολογητα). Much like Laurent Joubert’s medical Erreurs populaires (1578), these reformers claimed to provide better knowledge for the masses through the imposition of elite practices and values.62 De fixis stellis

Econtrario aut, male his terraenascentibus ominatur: quae non nisi terra humectiore crescere possunt, cuiusmodi sunt avena, hordea, multa leguminum genera, pascua &c. Qua e re in his rebus, in animalium pabulis futuram caritatem praedicimus.” 59 Stadius, Tabulae Bergenses, p. 207. 60 Ibid., p. 207. 61 Ibid., pp. 207–208. 62 For an introduction to social and anthropological approaches to the theme of “popular errors” in early modern Europe, see Davis, “Proverbial Wisdom and Popular Errors.” A good introduction to the work of Laurent Joubert is Céard, “Paradoxe et erreur populaire.”

ptolemy, parapegmata, mathematics, and monsters 201 expanded the promise of controlling popular predictive practices, since the earlier focus on annual prognostications had now come to integrate agricultural, medical, and sea-faring practices. The expertise that guaranteed such control was embedded in the re-enactment of (a humanist version of) ancient doxography: Stadius’ predictive contest with his aging father. In this story, an astrological reformer (Ptolemy/Joannes Stadius) successfully incorporated valuable folklore (anonymous farmers/Petrus Stadius) while severing it from unreliable recent precepts (Arabic astrologers). The basis of Stadius’ expertise lay in his complete emulation of Ptolemy. 2.5. Emulating Ptolemy’s Phases of the Fixed Stars This complete emulation implied a disciplining of popular folklore by subjecting it to operative causal explanations. In Ptolemy’s words, the astrologer needed to “discern, not their essential, but only their potential effective qualities, such as the sun’s heating and the moon’s moistening, and so on with the rest.”63 Although these concerns were a typical part of astrological physics, Stadius presented them as the backbone of his De fixis stellis: From this ratio of mixtures, an able and skilful natural philosopher will prudently discern the nature through which zodiacal signs change the weather (…) And I recommend to anyone, to take Ptolemy’s Phases by the hand, recalculate them for the local latitude and to gather observations for four years, so that one might subsequently predict with greater certainty the conditions, injuries, and favors of the heavens.64

Stadius’ reference to the “ratio of mixtures,” or his presentation of the astrologer as a “natural philosopher,” clearly connected his project to the realm of astrological physics.65 In doing so, Stadius turned away from the restoration of ancient parapegmata and implemented an observational methodology instead. This observational methodology was derived from Pliny’s Natural History ii.48, which cited Eudoxus’ opinion that a four year-cycle controlled weather

63

Tetrabiblos, p. 11. Stadius, Tabulae Bergenses, p. 205: “Atque ex hac commixtionum ratione, dexter & solers Physicus, quae sit natura signorum in tempestatibus variandis, prudenter discernet (…) & suaserim ego, ut quatuor annorum observationes, Ptolemaei inerrantium fastis ad exemplar adsumptis, & ad suum horizontem accommodatis, sibi quilibet instituat, ut deinde securius de coeli statu, iniuria, benignitate, praedicere possit.” 65 Ibid., pp. 204–205. 64

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conditions.66 Its ultimate goal was to build up a new judicial astrology, structured around the model of Ptolemy’s neglected Phases of the Fixed Stars.67 Stadius claimed that he was composing a commentary on this work, which he failed to append to the Tabulae Bergenses because his four-year series of original observations was not yet complete.68 As an alternative, Stadius concluded the Tabulae Bergenses with an updated “catalogue of the general and particular qualities of the heavenly constellations and signs for the year 1560.”69 This was in fact an updated version of Ptolemy’s astrological star catalogue in Tetrabiblos ii.11. Stadius first determined the Copernican rate of precession for epoch 1560 and positioned the longitudes of the fixed stars. Next, he reviewed the individual powers of 286 fixed stars in terms of planetary natures, as well as the meteorological effects of the different parts of their constellations. Still following Ptolemy’s example, he differentiated these effects according to the northern and southern parts of these constellations. The first column focuses on the longitudinal distribution of meteorological effects. The left margin of his updated catalogue is perhaps the most significant, because it shows Stadius constructing a new body of astrological physics, based on original observations. Consider the following examples: This part of the sign of Aries produces less thunder, and more hail than in Ptolemy’s time.70

66 Ibid., p. 205: “ Singulo quoque quadriennio tempestatum vices ad stata fere tempora redire (quod ex Eudoxo Plinius refert) deprehendet, sed eas aut remissiores aut intentiores, prout a generaliore constitutione adiuvabantur, hoc est, a planetarum transitu, συζ†γÝαισ, luminarium deliquijs.” Note, however, that Cardano recommended the same methodology in his commentary on Tetrabiblos (1554). See Grafton, Cardano’s Cosmos, p. 146. 67 On the position of the Phases in the history of Greek parapegmata, see Riley, “Ptolemy’s Use of His Predecessors’ Data.” Johan Ludwig Heiberg mentions two pre-19th-century editions of the Phaseis (Bonaventura, 1592; Petavius, 1630). See Ptolemy, Astronomica Minora, ed. Heiberg, vol. 2 (1907), p. v. This treatise was also included in Erasmus Schreckenfuchs’ edition of Ptolemy’s Opera omnia (excluding the Geography), published by Henricus Petreius in Basel, 1551. Joannes Grapheus’ edition of a translation attributed to Niccolo Leoniceno (Antwerp, 1527: nk 3782) indicates an earlier interest in this work in the Low Countries. 68 Stadius, Tabulae Bergenses, p. 205: “Nos commentaria in Ptolemaeum de inerrantium fixarum significatione huic loco adijceremus, sed quum hoc quadriennium nondum nobis observatum sit, ea suppressimus.” 69 Ibid., pp. 233–245. 70 Ibid., p. 233: “Portio ista dodecatemorij Arietis est minus tonitruosa, & magis grandinosa quam seculo Ptolemaei.” Stadius also remarked that “Extremae Arietis partes aestuosae plusquam seculo Ptolemaei sed minus pestilentes” (ibidem).

ptolemy, parapegmata, mathematics, and monsters 203 Or: The end of Leo is rather temperate in this age, although it was once dry and harmful.71

Or: The first part of Sagittarius is humid and colder than before.72

Although De fixis stellis consciously inserted itself in an ancient tradition of judicial astrology, Stadius clearly assumed that its reliability depended on a sustained observational practice. This practice, he thought, would ultimately lead to a reformed astrological physics concerning the fixed stars.

3. John Dee’s weather observations: towards a mathematical astrological physics (1548) Stadius’ weather observations continued a European practice that went back to at least the early fourteenth century.73 The Bodleian Library (Oxford) preserves weather observations from the period 1337–1344, ascribed to the Merton student William Merle.74 Interest in these practices seems to have shifted from England to the Holy Roman Empire around 1500. Extant weather observations from this period bear the names of renowned mathematicians like Martin Biem (Cracow, 1502), Joannes Aventinus (Munich, 1511), or Joannes Werner (Nuremberg, 1513). Gustav Hellmann assumed that these observers intended to compare their observations with astrological weather predictions.75 However, our study of Stadius’ De fixis stellis showed that the information from such observations served not one, but two different goals: the first was aimed at the selection of practical precepts, the other at constructing a reformed astrological physics. While Stadius’ emphasis lay on the first component, it also became clear that this was not entirely separate from a more ambitious theoretical agenda.

71 Ibid., p. 238: “Finis Leonis ad temperiem se inclinat hoc seculo, cùm olim siccus & noxius esset.” 72 Ibid., p. 241: “Prior pars [Sagittarij] est humida & frigidiora quàm olim.” 73 See Hellmann, Meteorologische Beobachtungen. 74 Hellmann, Meteorologische Beobachtungen, pp. 25–26; Bos/Burnett, Scientific Weather Forecasting in the Middle Ages, pp. 67–69. 75 Hellmann, Meteorologische Beobachtungen, pp. 16–17.

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This section focuses on another member of Gemma’s familia who pursued a programme of weather observations, but whose results were mainly theoretical: John Dee. In order to bring out the rareness of this attitude, we first discuss the situation in another important center of astronomical and astrological observations, Nuremberg.76 3.1. Weather observations at Nuremberg: Werner, Camerarius, and Schöner On 27 December 1534, the Nuremberg humanist Joachim Camerarius dedicated his editio princeps of the Greek texts of Tetrabiblos and Centiloquium to Albert of Hohenzollern, Duke of Prussia (1490– 1568). In his dedicatory letter, Camerarius argued that the science of the stars suffered from structural problems. While the practice of other arts continued in the most difficult of times, this was not the case for astronomy and astrology, due to their dependence on royal expenditure for perpetual observations in many different locations. With a hint to a widespread assumption that the mathematician Ptolemy was one of the Hellenistic kings bearing the same name, Camerarius presented the Tetrabiblos as the tangible result of such magnanimity.77 Camerarius’ letter clearly focused on the methodological continuity of astronomy and astrology. It sketched an observational practice characterized by broad geographical distribution and royal patronage, and presented Ptolemy’s work as an example of the benefits of this methodology. Joannes Schöner followed Camerarius’ outlook in his edition of Joannes Werner’s weather observations between 1513 and 1520 (1546). Schöner’s dedicatory letter pointed out that the study of astronomy would falter unless the legacy of the ancients was first conserved, then diligently studied, and finally increased. Hence, he had previously edited the astronomical observations of Peurbach, Regiomontanus, and Walther, which were now supplemented with Werner’s astrological counterpart.78 Schöner’s interpretation of the role of these observations is remarkable: For it is most useful that students of great men become accustomed to the right exercise [tractatio] of those arts through precepts as well as examples.79 76 For an introduction to the mathematical scene at Nuremberg in this period, see Pilz, 600 Jahre Astronomie, pp. 58–219. 77 See Ptolemaeus, Tetrabiblos, ed./trans. Camerarius, fol. 4r. 78 Werner, Canones, fols. a2r/v. 79 Ibid., fol. a2v: “Utilissimum est enim discentes magnorum virorum non solum

ptolemy, parapegmata, mathematics, and monsters 205 These weather observations were examples (the title page calls them “observations”), Schöner wrote, for the practical aphorisms on weather prediction that Werner provided.80 Closer inspection of these aphorisms reveals a strong continuity with previous practices of weather prediction. Werner assigned the primary role to the sun, assuming that it influenced the sublunary realm both directly and indirectly. Indirect influence occurred through planetary aspects, which enticed other planets to release their proper virtues among the four sublunary elements. Werner also arrives at a fairly traditional conception of the nature of the planetary virtues: Saturn causes cold weather, Jupiter and Mars elicit hot conditions. Werner adopted the traditional concept of fiery and watery signs, presupposed knowledge about the specific virtues of the fixed stars, and advocated the use of lunar prorogations. This astrological heuristic was dominated by the relative positions of the luminaries, combined with the angular aspects of the other planets and their position in the zodiacal signs. Such procedures can easily be traced back to the Ptolemaic techniques for weather prediction in Tetrabiblos, book ii.81 All in all, we find only occasional departures from ancient precepts.82 This suggests that weather observations were supposed to interact with (existing) precepts of judicial astrology, as happens in the following example: 9 February [1513]. The sun entered the sign of Pisces, and applied to a trine aspect with the stationary Saturn. Hence, a great frost with much snow arose for many days, and the Argestes wind blew abundantly.83

praeceptis, verumetiam exemplis assuefieri ad legitimam istarum artium tractationem.” 80 Ibid., fols. a3v-b2r. 81 See Tetrabiblos, p. 199: “Furthermore, we must take into consideration the special qualities of the signs of the zodiac to obtain prognostications of the winds and of the more general natures; and the variations of degree from time to time are in general again shown by the conjunctions which take place at the aforesaid points and by the aspects of the planets to them, and in particular also by the conjunctions and full moons in the several signs and by the course of the planets. This might be called monthly investigation.” 82 Capricorn belongs to the cold earthy triangle, Aquarius to the hot airy one in traditional Latin astrology. Werner considers them both as cold signs, probably because planets assume their lowest position above the horizon in northern regions when they are in these signs. 83 Werner, Canones, fol. b1v: “9 Februarij Sol ingressus Piscis signum, applicuit ad trinum Saturni Stationarij. Multis itaque diebus ingens gelu, cum multa nive extitit, & ventus Argestes crebre flabat.”

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The obvious “theory-ladenness” of Werner’s observation reveals an intention to select existing astrological experiences, not to establish novel ones. 3.2. Weather observations at Louvain: John Dee John Dee carefully observed the sky above Louvain from May 1547 to 16 February 1551, although only a sample from August 1548 has been preserved.84 The content and structure of Dee’s notes differ substantially from those of Joannes Werner. First, one may note that they describe atmospheric conditions without referring to astronomical configurations. The most distinctive novelty, however, is Dee’s sustained use of topological concepts, which provide a relational ordering of different meteorological phenomena.85 His weather observations used four fixed parameters: cloudiness, wind direction, wind force, and time. For cloudiness, Dee distinguished four categories, ranging from heavy clouds to an open sky. When describing wind directions, he resorted to a familiar scheme of sixteen winds, probably adopted from the Louvain cosmographical treatises. Wind force could be expressed in three ways, ranging from “considerable” (multis) to “more vehement” (vehementior ), while Dee also allowed for an upward extension of these degrees. Dee also recorded each change in atmospheric condition to the hour. Temperature is listed occasionally, while more detailed data on precipitation were kept on a separate sheet.86 The absence of astronomical data or careful chronology of Dee’s records was not unique: the Bolognese notary Andrea Pietramellara had kept an equally meticulous empirical journal in 1524.87 But even Pietramellara did not use anything like Dee’s systematic topological ordering of atmospheric conditions. 84 Hellmann, Meteorologische Beobachtungen, part 1, p. 52, quotes an entry in the old catalogue of the Ashmolean Mss. stating: “Dr. F. Bernard hath one of Stoffler’s Ephem: wherein are entered with Dr.: Dees hand his Observations of the Weather from May 1547 to 16. Feb. 1551, they are very exact & particular.” The preserved weather observations for August 1548 are on two leaves inserted after the text of his copy of Abenragel, De iudiciis nativitatum (1546), now in London, rcp, d48/6. 85 My description of Dee’s classifications for weather observations as topological concepts (as opposed to classifying concepts on the one hand, and quantifying concepts on the other) is derived from standard measurement theory. See Berka, Measurement: Its Concepts, Theories and Problems, pp. 5–9. 86 Listed under the title Appendix in aliquot praecedentis mensis dies. 87 Extracts published in Hellmann, Meteorologische Beobachtungen, part 2, pp. 19–25. Andrea Pietramellara was probably related to Jacobus Pietramellara, a well-known

ptolemy, parapegmata, mathematics, and monsters 207 Why did Dee develop these unique methods for recording the weather? Since we know that Dee’s astrological concerns at Louvain were directly related to the content of his published Propaedeumata aphoristica (see chapter 6), it may be rewarding to look for clues in this later work. This treatise on astrological reform advocated an astrological practice, constructed around an optical model of celestial influence. The success of this enterprise was obviously dependent on the availability of suitable data (e.g., the hot and wet nature of Venus) to which the optical model could be applied. Dee sketched a method to derive such data in Prop. c, which recommended that a particular planet’s sublunary (e.g., atmospheric) effects be evaluated against the humidity of the moon.88 Prop. liii shows that Dee probably intended his readers to concentrate on specific conjunctions between the moon and other planets. On such occasions, the former could in principle obstruct the latter’s proper effect. He also suggested that this be combined with the more random accumulated experience of continuous observations. This evidence suggests that quantitative, metrical concepts (the systematic replacement of qualitative predicates with quantitative ones) were not necessary to describe suitable data for the optical model. For instance, one could apply the traditional effects of the planet Mars (e.g., hot, dry, choleric, inducing quarrels, deceit or conspiracies) to the optical model in order to detect greater or lesser intensities of these effects (e.g., more or less heat, dryness, quarrels, conspiracies etc.). However, this is not what Dee seemed to have in mind. In Prop. xix, he advocated the “art of graduation” as the proper method to express celestial effects. This art of graduation referred to a scholastic medical tradition that expresses the intensity of each natural quality on a scale of (usually) one to four.89 We know that Dee later propagated a calibrated version of this “art of graduation,” thereby using fully quantified measurements.90 In Prop. xcvi, he also made the step towards quantification by calibrating the strength of planetary influences against the sun’s heat at closest approach (Prop.

Bolognese prognosticator who authored a prognostication on the 1524 conjunctions. See Hellmann, “Aus der Blütezeit der Astrometeorologie,” pp. 45–46. 88 Dee, Propaedeumata, p. 183. 89 This tradition was partially rooted in the astrological writngs of Al-Kindi. See Jacquart, La médecine médiévale, pp. 467–477; Arnaldus de Villanova, Aphorismi, ed. McVaugh. 90 Clulee, “John Dee’s Mathematics and the Grading of Compound Qualities”; Bowden, The Scientific Revolution in Astrology, pp. 96–97.

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xcvi).91 This makes it quite likely that quantification was also implied in the topological concepts of the 1548 observations. Dee’s careful timing of weather changes shows that he intended to compare these topological descriptions of atmospheric conditions to another set of chronologically fixed data. Most likely, these were astronomical data: Dee’s later weather observations were consistently kept in the margins of his astronomical ephemerides, while the August 1548 observations are bound with a set of astronomical calculations for 1 November 1548.92 We can safely conclude that Dee kept his Louvain weather observations with the ultimate intent of developing a quantified astrology, which at least expressed the mathematical ratios between astronomical and atmospheric conditions. This poses the obvious problem of why Dee cultivated an interest in quantified experience during his Louvain period. What made it acceptable to describe both astronomical and atmospheric phenomena as mathematical ratios? 3.3. Mathematical operationalism, natural philosophy, and astrological reform In his dedicatory letter to Mercator, Dee writes: For from what I have made available not only can a means be found of proceeding demonstratively [apodictice] in the art with regard to an infinite number of particular situations [ad infinitos particulares], but also, besides, the main principles of the science [disciplinae praecipua fundamenta] have been laid down and established here.93

Dee’s language immediately propels us to the lofty, theoretical realms of academic philosophy, since he promises access to demonstrative knowledge, based on principles that are specific to the discipline. This is combined, however, with a pre-eminently practical element: the consideration of singular situations. More than any other work of the Louvain school, Dee’s Propaedeumata undermined the distinction between astrological physics and judicial astrology. Dee claimed that its content endowed astrological methods with mathematical certainty. To this extent, it represented sixteenth-century concerns 91

Dee, Propaedeumata, p. 180. See Clulee, “Astrology, Magic, and Optics,” p. 645 note 44. 93 Dee, Propaedeumata, p. 112: “Ex his enim quae in medium attulimus, tum ad infinitos particulares, in Arte casus, Apodictice procedendi haberi facultas potest: tum ipsa praeterea disciplinae praecipua, in his sunt iacta, confirmataque fundamenta (…).” Translation by Wayne Shumaker. 92

ptolemy, parapegmata, mathematics, and monsters 209 with “method,” providing didactic-legitimizing concepts to tie down vague representations of ancient practices.94 Still, a closer inspection of the structure of Dee’s Propaedeumata shows that this remained a theoretical work. The first thirty aphorisms enumerate Dee’s astrological “principles.” Most are clearly physical: we encounter the propagation of species through rays (Prop. iv–v), the action of these rays as efficient causes (Prop. vi), the occasional use of light as a vehicle for propagation (Prop. xiii), and the unity of body and soul (Prop. xxiii). Dee’s second part fleshes out the mathematical properties of his optical model (Prop. xxxxlix). His third section explains why and how these physical and mathematical principles should be applied (Prop. l–cxx). Significantly, however, Dee never applied his complex mathematical combinatorics of celestial influences to practical effect. In this respect, it resembled Cardano’s harnessing of the multiplicity of Hippocratic precepts through mathematics in his commentary on Airs, Waters, Places (1570).95 Although the methodological Propaedeumata did not contain empirical discourse, the implementation of its method could abundantly generate it. At the beginning of his third section of aphorisms, Dee provided a clear hint of what kind of discourse he expected this to be: If you were skilled in “catoptrics,” you would be able, by art, to imprint the rays of any star much more strongly upon any matter subjected to it than nature itself does. (…) By this means obscure, weak, and, as it were, hidden virtues of things, when strengthened by the catoptric art, may become quite manifest to our senses.96

By means of “catoptrics” (the study of the reflection of light) and a burning mirror, Dee suggested, one could alter the intensity of celestial radiation.97 This would yield information on what nature can be made to do, but also on what nature is. This fascinating mix94 Dear, Discipline and Experience, pp. 121–122. Gilbert’s Renaissance Concepts of Method remains indispensable. 95 Ultimately, this complexity led Cardano to infer that “Hippocrates meant the physician to limit the environmental factors actually taken into account to changes in diet and exercise” (Siraisi, The Clock and the Mirror, p. 131). 96 Dee, Propaedeumata, p. 148: “ΚΑτοπτρικƒσ si fueris peritus, cuiuscunque Stellas radios in quamcunque propositam materiam fortius tu multo per artem imprimere potes, quam ipsa per se Natura facit. (…) Hinc obscurae, debiles, & quasi Latentes rerum Virtutes, arte Catoptrica multiplicatae, sensibus fient nostris manifestissimae.” Translation by Wayne Shumaker. 97 Dee, Propaedeumata, pp. 68–69.

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ture of operational and natural-philosophical interests comes as no surprise upon closer inspection of the Propaedeumata. Dee’s aphorisms constantly insist that celestial virtues can be harnessed and controlled by man for his own benefit. Following his optical theory of celestial efficiency, Dee assumed that burning mirrors provided the proper tools for this task, for instance in the production of talismans.98 Likewise, Dee found it self-evident to associate his astrological pursuits with natural philosophy. Throughout the dedicatory letter to Mercator, who is called “philosopher and mathematician,” Dee describes his topic as a philosophical scrutiny of nature. Echoes of this attitude were heard in the instruction sheet of Mercator’s astrological volvelle (1551). In a reference to contemporary astrological criticism, Mercator assured his readers that “if God grants us life and leisure, we will some day attempt to show by natural as well as mathematical demonstrations how we feel about this.”99 Mercator became more specific about his goals after his departure from Louvain to Duisburg in 1552. The preface of his Chronologia (1569) presented Mercator’s general cosmographical project as a “natural history.” For most sixteenth-century scholars, natural history was a collection of experiences, “raw” material that natural philosophy explained with the aid of reason. Mercator concurred: That is, causes are investigated and knowledge gathered from these effects, which are perceived by the senses. Indeed, even those so-called principles of demonstration, although they are indemonstrable, since there is nothing prior to them in cognition by which they could be demonstrated, are not known and do not obtain the status of principles until they are understood as being consistent with sensible things.100

Mercator planned five parts for his cosmographical annex to natural history. “Cosmopoeia” studied the genesis of the world, astronomy the genesis of celestial things, geography the genesis of terrestrial 98

Prop. ii, xxvi, lii, xcix. Mercator, Instrumentum Isagogicum, lines 41–42: “Si vitam & studijs ocium concesserit Dominus, tentabimus aliquando naturalibus & mistim Mathematicis demonstrationibus ostendere quid de ea sentiamus.” See Vanden Broecke, “Dee, Mercator, and Louvain instrument making,” p. 234. 100 Mercator, Chronologia, fol. (+)3r: “(…) Hoc est ex ijs effectibus qui sensu percepti sunt causas indagari atque ita scientiam colligi, quinimo nec principia ipsa quae vocant demonstrationum, tametsi indemonstrabilia sunt, quod prior in cognitione nulla habeant per quae demonstrari possint, non prius tamen agnoscuntur & principij rationem obtinent quam consentanea sensibilibus rebus intelliguntur (…).” 99

ptolemy, parapegmata, mathematics, and monsters 211 things, chronology the times of natural and human events, and genealogy human deeds, in as far as they were dependent on the natural world.101 The conceptual furniture of this natural history was predominantly mathematical. Mercator defined astronomy as the investigation of the “orbits, distances, magnitudes, projections and mixtures of rays” of celestial bodies, while his geography disclosed the “place, magnitude, division, weight, inequality, condition with respect to the sea and heavens &c.”102 Chronology was dedicated to the correlation of astronomical and historical events. In other words, Mercator intended to collect the “mathematical principles of natural history.” He advocated a natural philosophy that was rooted in the specialized experience of the mathematician.103 Once again, it is possible to refer to Pico’s Disputations as the proximate cause for these early Louvain developments towards “mathematical astrological physics.” We have previously argued that interest in the systemic properties of Copernican astronomy in Gemma Frisius’ familia was probably due to its utility in tackling Pico’s astronomical argument against the reality of planetary influences (chapter 6). Dee may very well have turned Pico’s entire use of the Kindian optical model against the Disputations, by applying it to a general elucidation of the physical interaction between heaven and earth.104 That these pursuits in astrological physics were combined with operational goals, is hardly surprising. Pico’s Disputations had shown that astrology ultimately undermined the concept of natural regularity by obliterating the causal explanatory autonomy of natural things.

101 Ibid., fols. (+)3r/v. Mercator does not provide a name for his first discipline in the Chronologia. In his cosmographical lecture notes, edited in 1563, we find a similar excursus under the name cosmopoeia (Mercator, Meditatiunculae, fols. b7v-c3v). On the relation between Mercator’s natural-philosophical and theological interests, see Suhl, “Zu Gerhard Mercators Evangelienharmonie”; Thiele, “Schöpfungsmythos und Naturwissenschaft.” 102 Mercator, Chronologia, fol. (+)3r. 103 On the role of “practical” mixed mathematics in the emergence of a mechanical and experimental philosophy, see also Bennett, “The Mechanics’ Philosophy and the Mechanical Philosophy.” 104 Dee’s Propaedeumata combined two different opinions on the causality of celestial light. Dee engaged with the Ptolemaic idea that celestial bodies actively distributed each of the four elemental qualities, as well as with Pico’s interpretation that they only imparted a variable elemental heat, with variable effects on sublunary moisture (chapter 6). At the very least, however, we can state that Dee consistently followed Pico’s model of a cooperative relation between superlunary and sublunary causality.

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Astrological physics predicated that the actualization of a sublunary substance’s natural state was permanently dependent upon the heavens (chapter 1). Under these assumptions, specialized knowledge of celestial causality could not fail to attract operational interests. Dee’s consummate expression of these various lines of influence was, of course, the obscure but ambitious “Archemastrie” described in his preface to the Billingsley Euclid (1570). Nicholas Clulee has aptly stated that the Archemastrie “combines the practices of the mathematical arts and of magic, and the goals and theories of natural philosophy, with methods of experimental verification. The resulting fusion cuts across traditional disciplinary divisions.”105 Modifying Clulee’s characterization of “experiment,” we might paraphrase Frances Yates by suggesting that magical interests did stimulate increasingly ambitious claims for the natural-philosophical relevance of mathematical experience.106

4. Strange heavens: teratology, prognostication, and Neoplatonism in the 1570s 4.1. Cornelius Gemma and the new star of 1572 Even among historians of science, it is rare to associate a particular historical period with natural, rather than human events. The 1570s were such a period, on account of two spectacularly new objects in the heavens: in November 1572, a supernova appeared in the constellation of Cassiopeia, while a comet was observed in the heavens in November 1577. Although both were transitory phenomena (the supernova remained visible for about two and a half years, the comet for less than three months), many astronomers found ample occasion for a thorough observation of these rare objects. A few of these results, including those of the Danish astronomer Tycho Brahe (1547–1601), challenged common Aristotelian physics. Parallax-measurements indicated that both the new star and the 1577 comet were situated well 105

Clulee, “At the Crossroads of Magic and Science,” p. 65. The notion of “experiment,” which Clulee seems to connect to seventeenthcentury usage, was thoroughly historicized by Dear, Discipline and Experience. Neither Dee’s extant weather-observations, nor his Propaedeumata, seem to warrant the suggestion that Dee departed from strategies of legitimizing experience that were common to the tradition of the mixed mathematics. For Frances Yates’ interpretation of Dee, see her Giordano Bruno and the Hermetic Tradition, esp. pp. 148–150. Compare with Wayne Shumaker’s comments in Dee, Propaedeumata, pp. 43–49. 106

ptolemy, parapegmata, mathematics, and monsters 213 above the moon, in a sphere that was traditionally taken to be completely homogeneous and perfectly unchangeable. This resulted in a flood of tracts and debates on the proper interpretation of such phenomena.107 These strange heavens coincided with a crucial phase in the history of the Low Countries. In the spring of 1572, the separatist movement under William of Orange booked its first successes against the Spanish crown. The antagonism between northern and southern provinces was put aside in 1576, when the entire Low Countries united in revolt against the Spanish Habsburgs under the Pacification of Ghent. By the end of the 1570s, the formation of two “smaller unions” with different religious and political preferences had started to erode the common project. This gradually restored Spanish prerogatives in the southern provinces and erased any hope for a diplomatic settlement of the issues. Celestial phenomena were eagerly adopted in propagandistic pamphlets on either side of the conflict.108 Publication patterns in the southern provinces indicate an extraordinary interest in mirabilia in this period. Out of 30 tracts on natural or mathematical topics, published in 1572 or 1573, no less than eight were explicitly devoted to rare or occult phenomena.109 Their popularity increased even more at the time of the 1577 comet: out of 28 publications on natural or mathematical topics in 1577 or 1578, eleven concerned astrology and/or new marvels.110 Under these circumstances, the political meaning of the new star of 1572 could hardly fail to attract interest in the Low Countries.111 The earliest example was published anonymously at Antwerp on 15 December 1572. This vernacular tract argued that the new star was a sublunary meteor, not unlike comets, but with a more dense matter, 107 For an introduction to the varied roles that these phenomena played in early modern science, see Hellman, The Comet of 1577; Methuen, “‘This comet or new star”’; Thoren, The Lord of Uraniborg, pp. 55–73; Westman, “The Comet and the Cosmos”; Westman, “Three Responses to the Copernican Theory.” 108 Mout, “Prognostica tijdens de Nederlandse Opstand.” 109 These numbers are based on Belgica Typographica, a bibliography of printed works from the southern provinces, 1541–1600. The eight editions are listed in Cockx-Indestege et al. (eds.), Belgica Typographica (bt): bt 1851, bt 4634, bt 4824, bt 8042, bt 8733, bt 8797, bt 9089, bt 9232. 110 The eleven editions are listed ibidem: bt 273, bt 1122, bt 1250, bt 4309, bt 4647, bt 4648, bt 4828, bt 6581, bt 7697, bt 7728, bt 7857. 111 My account of literature on the 1572 supernova from the Low Countries is based on the thoroughly documented survey of Van Nouhuys, The Age of Two-Faced Janus, pp. 150–158.

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which explained why it had not moved for over a month. Having presented the new phenomenon as a less familiar type of comet, our anonymous author proceeded to subject it to a traditional astrological analysis of comets. This led up to the familiar conclusion that “heat, sterility, pestilence, popular unrest, and the deaths of princes and great lords” were to be expected.112 Referring to the contemporary troubles, the author conceded that these were already present, and that God might just as well have created the comet to announce their end, followed by a new triumph of the Catholic Church.113 The Flemish tract was published on a Monday. The following Wednesday, 17 December 1572, Cornelius Gemma received the imprimatur for his own Latin treatise on the new star.114 In this work, he contested the naturalistic interpretation that the new star was a sublunary, fiery meteor. Cornelius first attacked the attempts at reducing the phenomenon to common, natural categories. The brightness of its light, as well as its novelty, spoke out against the suggestion that this was a celestial body. Its lack of similarity to traditional comets or exhalations placed it outside the Aristotelian category of sublunary meteora.115 Rather than acquiescing in an apparent paradox, Cornelius Gemma adduced his astronomical parallax determinations to establish the star’s position in the superlunary realm. By implication, it had to be a supernatural phenomenon, a divine prodigy comparable to the star of Bethlehem. This interpretation was reinforced when Cornelius read religious imagery into the star’s position relative to other celestial bodies. Most likely, he concluded, this divine sign heralded the accession of peace, grace, and forgiveness, and perhaps even the parousia.116 A number of parallels can be drawn between Cornelius Gemma’s treatise on the 1572 supernova and the Ephemerides that he wrote a decade earlier. First, they received active support from local ecclesiastical authorities. Prior to publication, Cornelius sollicited and obtained an imprimatur for both works. The Louvain theologian Joannes Molanus signed it in 1572. The very same Molanus later recalled:

112

Van Nouhuys, The Age of Two-Faced Janus, p. 155. Ibid., p. 156. 114 For bibliographical descriptions of Gemma’s treatises on the 1572 supernova, see Van Ortroy, Bio-bibliographie, pp. 378–386. 115 Van Nouhuys, The Age of Two-Faced Janus, pp. 152–153. 116 Ibid., pp. 153–154. 113

ptolemy, parapegmata, mathematics, and monsters 215 When he had not yet been promoted, Cornelius Gemma wrote some [almanacs]; but admonitions led him to abstain from this, reneging them like others have done.117

Second, both tracts seem to have responded directly to the discourse of competitors on a lower rung of the astrological profession. In the ephemerides, an expanded Ptolemaic practice became a means to avoid popular political predictions completely. The 1572 tract obtained its ecclesiastical approval with suspicious swiftness after the publication of an anonymous Dutch tract on the same topic. This initial tract offered a pessimistic outlook, to which Cornelius Gemma opposed a strictly religious and more hopeful interpretation. The grounds on which Cornelius Gemma reached this conclusion nevertheless suggest a fundamental difference separating the naturalistic conclusions of the ephemerides from the supernatural message in the treatise on the new star. Had Cornelius become a Christian prophet instead of a Ptolemaic astrologer? The following sections show how he managed to be both. 4.2. Neoplatonism, Augustinianism, and the cosmocritical art In 1575, Cornelius Gemma published a tract entitled De divinis characterismis naturae.118 In this treatise, he presented the outlines of the “cosmocritical art” (ars cosmocritica), a new and exceedingly ambitious divinatory science. Since the meaning and extent of the cosmocritical art was intimately linked to its philosophical foundations, we will explore these first. Two philosophical ideas were fundamental to the cosmocritical art. The first was a typically Neoplatonic conception of the universe as a metaphysical hierarchy. Initially, Cornelius Gemma distinguished seven levels of being: prime matter, prepared matter, spirit, the soul’s carrier, soul, mind, and common intellect.119 In practice, however, this scheme was simplified to a five-fold arrangement (matter, the informed mixtures, spirit, soul, and God and his angels) or even a three-fold one (body, spirit, soul).120 The supreme divine being

117 See Molanus, Historiae, vol. 2, p. 571. This might refer to the earlier political predictions that Cornelius Gemma explicitly rejected in his ephemerides. 118 Gemma, De naturae divinis characterismis. The word characterismus seems to be a latinization of the rare Greek χαρακτÛρισµοσ. This may be treated as equivalent to χαρÀκτηρ, “character” or “mark,” in the context of Cornelius Gemma’s treatise. 119 Gemma, De naturae divinis characterismis, vol. 1, p. 29. 120 Ibid., vol. 1, pp. 30–33.

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diffuses itself through these lower orders on the principle that each pair of active and passive substances share a likeness (similitudo) that enables them to interact. Hence, the entire universe can be regarded as: One animal, in which a single Mind, or one soul endowed with one spirit, is diffused through a single body with perfect uniformity. Not so much human reason, but the beauty of this entire order, or the harmony of its single parts and actions, demonstrates this through the force and power of the intellect.121

This universal animal manifests itself in various ways in different parts of the visible world. In the human microcosm, it is embodied as the harmonious interaction between body, spirit, and soul. In the macrocosm, it represents the relation between sublunary elements, ether, and the celestial realm. In the state, it stands for subjects, kings, and God.122 This divine omnipresence was also hierarchically distributed. Gemma claimed that prime matter, which he held responsible for the incertitude of natural knowledge, displayed least divinity.123 In the mixtures of prepared matter, Gemma adduced a divine presence to explain traditional concepts like occult quality, quality “of the entire form” (Galen), or individual spirit (Fernel).124 Divinity comes into its own on the next higher level, where Gemma situated his own notion of spirit. Every effect of the soul or celestial rays was brought into being by spirit. In the case of the soul, Gemma mentions the formation of the foetus, where spirit guides its generation from beginning to end. Concerning celestial rays, he assured his readers that their native heat (calor nativa) had a double nature, one of which was spirit.125 Beyond spirit, we find even more divinity in the faculty of imagination and the “occult seeds” of reason and intellect, of which the soul disposes from the very beginning. It derives common notions and concepts from mind, and entrusts these to memory, while the di-

121 Ibid., vol. 1, p. 34: “Totum illud quod mundus vel universum dicitur, esse quoddam animal unum cui Mens unica vel animus unus uno spiritu praeditus, per corpus unicum sit summa aequabilitate diffusus. Hoc enim non tam humana ratio, quam totius ordinis pulchritudo, partium singularum & actionum conspiratio, ex intellectus vi & potestate demonstrat.” 122 Ibid., vol. 1, pp. 33 and 141–143. 123 Ibid., vol. 1, pp. 29–30. 124 Ibid., vol. 1, pp. 30–31. 125 Ibid., vol. 1, p. 31.

ptolemy, parapegmata, mathematics, and monsters 217 verse faculties of the soul are gradually integrated with one another.126 Complete divinity belongs to the two superior levels of Gemma’s metaphysical hierarchy, which belong to the angels and the common intellect. At the apex of this hierarchy stands an omnipotent unity that man can only know metaphorically: God.127 Governed by the principles of proportion, likeness, or harmony, Gemma’s Neoplatonic universe conspired to celebrate divinity: All things [serve] the suitable and truthful good of One, as well as the glory of His name and the well being of the universe.128

This Neoplatonism was combined with a predominantly Augustinian outlook on this harmonious hierarchy .129 Cornelius Gemma emphasized how the metaphysical “golden chain” had been ruptured as a result of the biblical Fall: For had that previously intact golden chain not burst, almost into broken shackles, by the offences of mortals, and had each thing respected its proper place in the universe, then lower things would have agreed with higher ones beyond disorder, in both effects and causes. But the crime of arrogance -or rather conspiracy against God-, spread down towards mankind from the angelic nature. Hence, this most beautiful but loosened order between God, angels, stars, and the sublunary realm, chiefly spoiled the figure of this jewel of the universe.130

The absence of harmony in the new post-lapsarian order manifested itself in the problem of evil: The divine good is sometimes corrupted through the vice of matter, at other times through intermediate guides or evil demons. These accomplish nothing, however, without divine permission; and neither is this permitted unless we deserve it.131 126

Ibid., vol. 1, p. 32. Ibid., vol. 1, p. 32. 128 Ibid., vol. 1, p. 57: “(…) Omnia vel tum ad unius commodum ac verum bonum, tum ad nominis sui gloriam, ac salutem universi.” 129 For instances of this “golden chain,” see Gemma, De naturae characterismis, vol. 1, pp. 35, 59, 81, 127. 130 Gemma, De naturae divinis characterismis, vol. 1, p. 81: “Illa etenim χρàσειη σεÝρασ si per delicta mortalium non ante convulsa tanquam abruptis ansulis dissiluisset, suum quaeque servarent convenientem locum in universo, & praeter ˆταξÝαν omnem, postrema prioribus tam in effectuum, quam causarum genere consentirent. Sed ex natura angelica superbiae scelus, ceu coniuratione in Deum facta, tandem ad homines dimanavit: unde solutus ilicet ordo ille pulcherrimus inter Deum, Angelos, stellas, & orbem sublunarem, universi faciem ornamenti parte praecipua spoliavit.” 131 Ibid., vol. 1, pp. 60–61: “(…) Bona deorum corrumpi alias materiae vitio, alias per intermedios duces vel daemones malos; quibus tamen nihil efficitur, nisi divinitus permittatur; nec fere permittitur nisi sic mereamur.” 127

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The unique accomplishment of De divinis characterismis was to combine this pessimistic, Augustinian anthropology with Ficino’s notion of spirit as the basis for interaction between different ontological levels.132 This led to the remarkable result that passions of the human soul could negatively affect seemingly unrelated substances: Thus, a token of human desire passes into the world-spirit, as a result of corrupted conceptions in this surrounding sphere (…); this [worldspirit] pours characters of that [desire] back into the elementary realm; and through those characters into the bodies that, born from these principles, constitute community and state.133

The transitivity between moral and physical structures provided the backbone of Cornelius Gemma’s cosmocritical art. It implied that prodigious natural events were simultaneously symptomatic of the moral corruption that originated in the Adamite Fall. This symptomatic quality functioned on different levels. Within the domain of natural events, marvels highlighted the extent to which original sin had permanently ruptured the golden chain of being. On the level of the supernatural, miracles illustrated God’s providential power over the world. From a divine perspective, there was no essential difference between the natural and the supernatural, since both were subsumed under God’s providential plan for the world. The difference between natural and supernatural events was essential, however, to the extent that symptoms were also signs. While the birth of Siamese twins at Louvain in 1536 and 1547 was symptomatic for the corrupted structure of the world, it could also be exploited to read the specific nature of this corruption in a local setting.134 As a physician, Cornelius Gemma eagerly adopted the medical analogy. He pointed out that diseases resulted from a lack of cooperation between constituent parts of the body; hence, health would result from the restoration of this harmony.135 But how to find out which constituent parts are responsible for a particular disease?136 The birth of Siamese twins could result from

132

Ibid., vol. 1, p. 31. Ibid., vol. 1, p. 63: “Ita & conceptibus vitiosis in orbe hoc continente (quem universum nominant) humanae libidinis nota transit in spiritum mundi; hic rursus eiusdem characteres refundit in elementa; & per haec denique in ea corpora quae illis primordiis oriunda civitatem at rempublicam constituerunt.” 134 Ibid., vol. 1, pp. 91–92. 135 Ibid., vol. 1, p. 42. 136 The medical background of Cornelius Gemma’s problematic ties in with a 133

ptolemy, parapegmata, mathematics, and monsters 219 natural causes, confined to the elementary realm where divinity was least present; it could be a supernatural event, imposed by the highest and most divine metaphysical ranks; or they might result from a preternatural mixture of causes, connected to universal spirit and soul.137 This was a crucial problem, since the profoundly Christian anthropology of the cosmocritical art implied that the importance of a prodigious sign was directly related to its degree of divinity, and hence to its status in the ontological hierarchy of the world. Cornelius Gemma’s solution was rooted in the “cyclognomical art,” which he had published in 1569.138 This art enabled practitioners of the cosmocritical art to determine whether a particular prodigy could be situated in common natural and preternatural structures, or not.139 The second methodological rule of the cosmocritical art advised its practitioners to cleanse their souls. This gnostic element may have been introduced in response to the contemporary Aristotelian problematic of how to make a proper transition from empirical to causal knowledge (negotiatio).140 On the other hand, there is clear evidence of an unacknowledged debt to the famous first aphorism of the pseudo-Ptolemaeic Centiloquium.141 Gemma’s third piece of advice expands upon this theme by reminding his readers that some signs are effects signifying their causes, and others causes signifying their effects.142 In fourth place, we learn that the cosm-

wealth of epistemological issues that cannot be adequately discussed here. However, see Maclean, “Evidence, Logic, the Rule and the Exception.” 137 Gemma, De naturae divinis characterismis, vol. 1, p. 44. 138 Ibid., vol. 1, p. 122: “Imprimis etenim discendus est ordo Mundanae fabricae, partiumque consensus ante descriptus, quem tamen expressit latius ars cyclognomica, universitatem rerum una passim ternarij sacri ratione distribuens, ad normam animae rationalis: nam in hoc theatro omnes naturae leges, earumque conspiratio cum divinis maxime patet.” The cyclognomical art was the topic of De arte cyclognomica (Antwerp, 1569). For a reliable introduction to this fascinating mnemonic art, see Mulsow, “Seelenwagen und Ähnlichkeitsmaschine.” 139 As an example, one can find comprehensive tables of possible disproportions in every realm of the visible world in Gemma, De naturae divinis characterismis, vol. 1, p. 47 sqq. 140 Scholarly literature most often discusses this problem in the context of the Paduan theories of methodological “regress.” See the introduction by Jardine, “Theories of Knowledge,” pp. 686–693, and the collected essays in Di Liscia et al. (eds.), Method and Order in Renaissance Philosophy of Nature. 141 Cornelius Gemma introduces his methodical rules as καρπÞυσ, “flowers,” which probably refers to the original Greek name of Centiloquium. See Gemma, De naturae divinis characterismis, vol. 1, p. 122. 142 Gemma, De naturae divinis characterismis, vol. 1, p. 125.

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ocritical art should first consider the best interests of public good and divine glory, by presenting universal or hypothetical predictions only. 4.3. Teratology and astrology in the cosmocritical art Gemma’s last methodological precept leads us back to one of the central questions of Louvain astrology: how can one safeguard a proper relation between astrological practice and political or religious authority? The answer that Gemma provided in his astrological ephemerides, also applied to the cosmocritical art: by means of general, non-committal predictions. This remarkable parallel warrants a further investigation of the position of astrology in the cosmocritical art. The proper domain of the cosmocritical art was situated in the gray zone of rare, prodigious, marvellous events: the things that natural philosophers referred to as “monsters” or τÀ τÛρατα. We have already come across the Louvain Siamese twins of 1536 and 1547; the examples multiplied themselves in book ii of De divinis characterismis. Cornelius Gemma was convinced that prodigies had become more frequent since 1555, especially afflicting the Low Countries after c. 1560. The winter of 1564, for instance, was exceptionally harsh after a conjunction of the superior planets and concurrent meteorological chasms.143 On 18 July 1566, one month before an iconoclastic movement swept across Flanders and Brabant, Cornelius Gemma observed a colored cloud on the horizon, which provoked terrible lightning and hailstorms.144 Other common prodigies were ghosts, dreams, counter-natural stones and vermin in human bodies, comets, celestial chasms, and various miscarriages. Ancient and medieval teratology was dominated by three sentiments: horror, pleasure, and repugnance.145 Like other “preternatural philosophers” of the sixteenth century, Cornelius Gemma struggled to integrate these approaches in a semiology that advertised its medical, natural-philosophical, and theological roots.146 Cosmocritical practice, however, seems to have been much more inspired by astrology than by any other discipline. Gemma provided three princi143

Ibid., vol. 2, pp. 41–45. Ibid., vol. 2, pp. 54–55. 145 Daston/Park, Wonders and the Order of Nature, p. 176. 146 The term “preternatural philosophy” is borrowed from Daston/Park, Wonders and the Order of Nature, pp. 159–172. 144

ptolemy, parapegmata, mathematics, and monsters 221 ples for cosmocritical predictions: experience, intellect, and reason. The presentation of these principles confronts us, once again, with the gnostic validation of predictive knowledge that we first encountered in the 1524 debates (chapter 4). Experience (historia) serves as a propaedeutic for prediction, which occurs either gnostically through the intellect (intellectus), or epistemically through reason (ratio).147 Now consider Gemma’s four starting-points for the “rational” cosmocritical art. The first stipulated a thorough investigation of the “substance” of a prodigy: its form, matter, color, symmetry, quantity, place, time etc. Gemma defended this precept through its similarity to Ptolemy’s rules for the interpretation of eclipses and comets in Tetrabiblos book ii.148 In second place, practitioners of the cosmocritical art were advised to heed the proportion between the active and passive causes that lead to a prodigy. The initial examples of this rule were taken from “meteorological ephemerides”: for instance, that Saturn and Jupiter produced earthquakes more easily if the earth had previously amassed more internal vapors through snow or frost.149 The third rule advocated an examination of concurrent causes. The value of this habit was demonstrated by the reliability of astrological weather prediction, and the uncertainty of individual political predictions.150 Only the fourth guideline (the investigation of likeness between things) turned to the ancient tradition of dream-interpretation, rather than astrology, for inspiration.151 An important part of the cosmocritical art was constructed out of recycled materials from Cornelius Gemma’s earlier astrological practice. In order to justify this use, Gemma adopted Ptolemy’s perennial maxim that the uncertainty of astrology belonged to its practitioners, but not to the art:152 And so I do not eliminate the art at all. Instead, I make it more divine than the impious masses assume it to be, having taken the occasion

147

Gemma, De naturae divinis characterismis, vol. 1, p. 127. Ibid., vol. 1, pp. 127–128. 149 Ibid., vol. 1, p. 131. 150 Ibid., vol. 1, pp. 133–134. 151 Gemma, De naturae divinis characterismis, vol. 1, p. 134 sqq. On dream interpretation (oneiromancy), see Reading Dreams, ed. Brown; Kruger, Dreaming in the Middle Ages. 152 Tetrabiblos, p. 13: “For a thing like this is an impotence, not of the science, but of those who practise it.” 148

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chapter seven from impostors and prognostications. Nothing is more stupid than their minds, more ridiculous than their rules, more rotten than their prophecies.153

The hostile attitude to popular prognosticators of the meteorological ephemerides (1561) did not change. Significantly, Cornelius Gemma pre-empted criticism of the cosmocritical art by positioning himself within an astrological problematic, defined by the respective positions of Pico and the prognosticators. In Gemma’s opinion, both erroneously assumed that astrological predictions were only based on knowledge of the heavens. In fact, he claimed, proper astrological practice was dependent on a close scrutiny of both the superlunary and the sublunary realm. This misunderstanding led the Disputations to misfire, as Pico found out when he died on the astrologically appointed day, restoring prognosticators’ confidence in their ability to provide specific predictions.154 4.4. The political and theological relevance of the cosmocritical art Gemma’s “more divine art” offered a solution to the astrological problematic that was radically different from his early weather predictions. While its semiotic strategies were profoundly indebted to those of Ptolemaic astrology, its natural-philosophical and theological background were tailored for the singular, “monstrous” experiences of teratology. In other words, the cosmocritical art enabled Cornelius Gemma to discuss exactly those phenomena which the prognosticator’s audience was eager to learn about: rarities, prodigies, marvels. Despite frequent disclaimers about his ability to make specific predictions, Cornelius Gemma often derived clear pro-Spanish predictions from his cosmocritical art. One example is his analysis of the arrival of the notorious Duke of Alba in August 1567. Gemma reported a solar eclipse preceding this event on 9 April 1567. Also, wheat had rained down near Luxemburg, from where the Duke made his way into the Low Countries, while showers destroyed the harvests, followed by epidemics and unusual frost.

153 Gemma, De naturae divinis characterismis, vol. 1, p. 202: “Artem igitur minime tollo, sed diviniorem facio, quam vulgus profanum putet, occasione sumpta ab impostoribus & prognosticis, quorum ingeniis nihil magis insulsum, regulus nil aeque ridiculum, vaticiniis nihil putidius.” 154 Ibid., vol. 2, pp. 3–9.

ptolemy, parapegmata, mathematics, and monsters 223 These prodigies incited Gemma to portray Alba’s extremely repressive Council of Troubles as an instrument of divine justice, comparing its bloody tactics to excessive, and almost fatal, bleedings in the medical treatment of difficult diseases. Likewise, William of Orange had done well to flee from Antwerp on 11 April, before Regentess Margaret of Parma arrived there in person. Manifest warnings were wasted, however, on Count Egmont Lamoral, who was arrested by Alba in September, and decapitated in June 1568.155 A similar attitude underlies Gemma’s interpretation of the Saint Bartholomew’s massacre of 1572. Although visibly shaken by the unusual extent of this sordid persecution, Gemma held it to confirm his conviction that “there is no reason why we should seek elsewhere than in ourselves for the cause of our ruin.”156 The connection between the cosmocritical art and the Spanish crown went further than Gemma’s tenure as royal professor of medicine at Louvain. This suggestion seems to have been widely shared in the sixteenth and seventeenth centuries. The Nederlandse Historien of Pieter Corneliszoon Hooft claimed that Gemma predicted two notorious executions in the troubled period 1568–1570, while the second part of Jacques-Auguste de Thou’s Historiae (1606) claimed that Alba invited him to Nijmegen for an astrological consultation.157 Another local institution that may have favored the cosmocritical art was Louvain’s theological faculty. Cornelius Gemma’s work seems to have developed in close contact with members of the Louvain theological faculty. In December 1572, Joannes Molanus provided a remarkably swift imprimatur for Gemma’s tract on the new star, the original nucleus of the cosmocritical art. The printed version of De divinis characterismis naturae contained laudatory verses by professor Petrus Bacherius and by the Spanish theologian Benito Arias Montanus.

155

Ibid., vol. 2, pp. 55–57. Ibid., vol. 2, p. 73: “Non est cur nostrae ruinae causam quaeramus alibi quam in nobismetipsis.” This casts a dark shadow over the irenicist motivations that Jan van Dorsten and Alastair Hamilton attribute to Abraham Ortelius (1527–1598), Gerard Mercator, and Cornelius Gemma. Through their philosophical investigations, these men supposedly intended to stimulate a tolerance that could transcend the religious and political divisions of their own time. See Van Dorsten, “Temporis Filia Veritatis: Learning and Religious Peace”; Hamilton, Family of Love. Irenicist motivations were recently claimed for the natural-philosophical work of Jean Bodin by Blair, Theater of Nature, pp. 146–148. 157 References in Van Ortroy, Bio-bibliographie, pp. 131–132. 156

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The theological background to the cosmocritical art probably struck a particular chord at Louvain. At the time of Cornelius Gemma’s medical studies, professor Michael Baius (1513–1589) explored new directions in theological method and doctrine.158 Baius sought to establish a methodological common ground with the Protestants. This attitude simultaneously emphasized two topics that were central to Protestant theology: the nature of grace and human free will. Concerning the former, Baius rejected the Protestant position that divine grace essentially bestows the remission of sin.159 But he was equally critical of the scholastic attitude, which minimized the importance of original sin by defining it as the privation of God’s supernatural gift of original justice, thereby implying that the Fall did not change man’s essential nature. On the authority of St. Augustine’s On the Original Sin, Baius proposed that original sin made man a hopeless slave of his passions, unable to choose the good because of his corrupted nature. According to the Louvain theologian, this is the sense in which Augustine wrote that human nature had become a natura vitiata. The corruption of human nature, not the Adamite Fall, constitutes the true essence of man’s sinful state. This interpretation posed considerable problems, however, for any theology of merit: if divine grace amounts to a restoration of man’s original nature, then God merely gave man his due.160 Baius found a loyal defender of his ideas in his friend and colleague Joannes Hessels (1522–1566). Other Louvain theologians, especially Ruard Tapper (1487–1559) and Judocus Ravestein (c. 1506– 1570), were horrified. In 1567, Ravestein obtained a papal condemnation of 79 propositions that implicitly referred to Baius’ teachings. Baius addressed an apology to Pius v (1566–1572) in 1569, in which he contested this attribution of the condemned propositions. Although Baius officially deferred to the papal decision, he regularly expounded his position before his Louvain students and colleagues in the 1570s, when Cornelius Gemma wrote De divinis characterismis naturae.

158 For a general review of Baius’ biography and doctrine, see Le Bachelet, “Baius Michel.” 159 On Baius’ attitude towards the doctrine of divine grace, I have followed the interpretation of Vanneste, “Nature et grâce dans la théologie de Baius.” 160 Vanneste, “Nature et grâce,” pp. 330–331 minimizes the importance of this problem.

ptolemy, parapegmata, mathematics, and monsters 225 This last work displayed remarkable attention to the issues that were debated by his colleagues of the theologian faculty. Consider, for instance, the following passage: And so they reveal a perpetual knot in the constitution of the world, from which I demonstrate that the stars do not naturally cause someone to be evil, or even more inclined towards evil. It was only when the most common order of sin attained the receptive parts of nature, that a specific propensity could follow from a specific concourse at birth, even in the presence of beneficent causes, applied to corrupted matter [materia vitiosa] (…) Although an act of the rational soul will transcend any celestial or corporeal force in this junction of things, and proximate causes will be stirred orderly by preceding ones in the rest of nature.161

In the first part of this passage, Cornelius Gemma identifies original sin as the cause of a general corruption of matter, which is referred to as materia vitiosa (a curious pendant to the Augustinian natura vitiata). This original corruption favors human receptivity to evil over any goodness that may be granted by the heavens. Likewise, Baius defended that man’s natural goodness was destroyed in the Fall. A change of tone appears, however, in the second part of Gemma’s text. Here, we find a Ficinian conviction that the rational soul can transcend any state that results from corporeal embodiment. This optimism echoes the traditional Catholic idea that original sin is transcended through the cooperation between God and the human soul.162 For all its receptivity to Baius’ problematic, the cosmocritical art ultimately embodied more traditional notions of grace, on the basis of a strongly Neoplatonized belief in man’s ability to decipher

161 Gemma, De naturae divinis characterismis, vol. 2, pp. 12–13: “Fateantur itaque nexum esse perpetuum in tot mundi syntagmate, quo plane convincam, non quidem astra efficere suapte natura, ut sit quispiam malus, vel etiam ad malum propensior: sed quando peccati communissima ratio naturae susceptricis partibus inolevit, futurum ut iam agentibus causis etiam bonis, & ad vitiosam materiem applicatis, certo concursu sub vitae prima cunabula, certam quoque propensionis speciem consequatur (…) Quanquam in ea rerum copula actus animae rationalis omnem exuperet tum caeli, tum corporis potestatem, ac in reliqua parte naturae causae quidem proximiores a praecedentibus ordine moveantur; ut tamen quae suis affectibus sint vicinae, per se magis agant impellantque fortius.” 162 Gerard Mercator shared Cornelius Gemma’s active interest in theological debates. For an introduction, see De Lang, “De godsdienstige ideeën van Gerardus Mercator.”

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divine messages.163 These messages simultaneously confirmed the legitimacy of Spanish rule, through the study of: Monsters and prodigies, which warn us openly and by divine command to raise our dormant soul towards higher things, and to remain mindful of the agreement of cause and effect in the triple world of divine, human, and natural law, as it pertains to the State.164

163 One could make an interesting comparison with the teratology of the Lutheran theologian Caspar Peucer, whose ideas influenced Cornelius Gemma’s cosmocritical art. See Céard, La nature et les prodiges, pp. 178–186. 164 Gemma, De naturae divinis characterismis, vol. 2, p. 16: “Magis multo haec confirmantur, si et res insolitae conspirarint, ut monstra, prodigia, quibus aperte monemur atque divinitus quidem, ut animum alto in pulvere dormientem excitemus, attentumque teneamus in illa consensione causarum atque effectuum in triplici mundo, seu legis divinae, humanae ac naturalis circa rempublicam.”

CHAPTER EIGHT

PROROGATIONS, HOUSES, AND NATAL ASTROLOGY

The desire to return to Ptolemaic practice also manifested itself in natal astrology. Its most forceful expression was the use of prorogations, a specialized technique for the prediction of life expectancies that Ptolemy discussed in Tetrabiblos iii.10.1 Ptolemy compared the lifespan that was allotted at birth to an arc of the celestial ecliptic. This arc started with a particular ecliptic point (the prorogator) where a person’s life was “launched,” and from where that person started a lifelong journey along the ecliptic. This journey was symbolized by a steady progression of the initial point, during which time it encountered one or several destructive points or planets (the “anaeretae”) that represented serious threats to life, or even the individual’s death. Prorogation gained a broader scope in Tetrabiblos iv.10. Instead of a single prorogator, symbolizing the individual’s lifespan, this chapter proposes no less than five prorogators for each individual (horoscope, lot of fortune, moon, sun, and mid-heaven). Each of these was linked with a specific sphere of human life, which implied that every person simultaneously completes five different prorogatory trajectories.2 1 Latin astrological texts habitually use three terms to refer to this technique: prorogatio, directio and progressio, although at least Gemma Frisius also suggested dimissio or emissio. See Gemma Frisius, De astrolabo catholico (1556), fol. 96v. All three render the Greek aphesis (“a letting go,” “dismissal”). Historians of astrology have preferred “prorogation” (especially through Robbins’ translation of Tetrabiblos iii.10), “progression” (Hogendijk) or “direction” (Burnett and North). The use of “direction” has the problem that additional neologisms would have to be coined for Greek derivative words like ±φετγσ (“director”?). Likewise, the use of “progression” has already spawned cumbersome translations like “emittive point” (Hogendijk). This study therefore adopts “prorogation,” which at least has the advantage of consistency and tradition in translating the various variants of ±φεσισ. In Arabic, ±φεσισ was usually translated as tashyir, while ±φετγσ was rendered as haylag. Its Latin transliteration hyleg, hylech, or hileg was frequently used in medieval and early modern Latin texts. Neither Latin nor English seem to offer common translations for the destructive degrees or planets that Ptolemy called τÞποι j ˆστÛροι ˆναÝρετικοι. The Greek ˆναÝρετα was simply transliterated to the Latin “anaereta,” which is the word I have retained in English. 2 Tetrabiblos, p. 449: “We shall apply the prorogation from the horoscope to events

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The technique of prorogation filled an important gap in the practice of natal astrology. In the words of Joannes Schöner: The genethliatical art consists of two things: the inquiry of things to come, on the one hand, and the examination of the time of these events, on the other (…) as the latter teaching cannot exist without the former, so the former has little importance without the latter.3

Early modern astrologers could choose among three available methods for the timing of future events: prorogations, profections, and revolutions. It is still unclear why prorogations became predominant among astrological reformers in the late fifteenth century. However, two specific features may have played in its favor. First of all, there is the fact that revolutions, which seemed to dominate late medieval natal astrology, were typically cast to gain information about a specific moment in the future, usually a particular year following one’s birthday.4 Prorogations, on the other hand, provided a complete symbolic representation of critical times in a client’s entire life. The early modern appetite for personalized predictions could easily have favored such unveilings of a chronologically wider range of future events. In second place, it seems probable that the widespread rhetoric of astrological reform highlighted the ancient credentials of prorogations. It was much more difficult to connect revolutions to Ptolemy, whose Tetrabiblos never mentioned this technique.5 Instead, they were perceived as part of the traditional Arabic legacy that many astrological reformers had come to distrust, or even reject.

relating to the body and to journeys abroad; that from the Lot of Fortune to matters of property; that from the moon to affections of the soul and to marriage; that from the sun to dignities and glory; that from the mid-heaven to the other details of the conduct of life, such as actions, friendships, and the begetting of children.” 3 Schöner, De iudiciis (1545), fol. 95r: “Doctrina Genethliaca in duabus rebus consistit in disquisitione apotelesmatum, seu eventuum, & definitione temporis decreti (…) Quemadmodum autem sequens doctrina sine praemissa non potest consistere, ita praecedens sine sequenti parum momenti habet.” 4 Revolutions, which contemporary astrologers call “solar returns,” are based on the idea that the annual return of the sun to the specific point of the ecliptic where it stood at the time of a person’s birth, is an event of particular significance for that person. The celestial configurations at the exact moment of this return signify influences that remain active for one year, i.e., until the next solar return. On occasion, early modern astrologers also calculated monthly revolutions. These were based on the lunar, instead of the solar cycle: one takes the exact time of a solar return, and adds the length of a mean lunar cycle for each month in that year. The result gives the time for which a monthly chart is calculated. 5 However, ps.-Ptolemy’s Centiloquium 88 does mention monthly revolutions.

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This chapter discusses three results of the widespread attempt to revive the Ptolemaic practice of prorogation. First, it shows how astrologers seized upon prorogations to prove their ability to make specific predictions of a client’s future. One of their preferred strategies was to publish detailed comments on local celebrity deaths. Next, we witness how the status of prorogation techniques was increased through its links with astrological house division. Since house division constituted a problem in its own right, this connection ultimately hindered the ancient credentials of prorogation. Although the technique could still claim empirical success, its relation to ancient practice had become ambiguous. The third part describes how Sixtus of Hemminga, a member of Gemma’s astrological familia, used public testimonies of the practitioner’s expertise against astrology. This last development discredited even personal experience as a reliable criterion to identify proper astrological practice.

1. Horoscope collections and astrological expertise 1.1. Joannes Stadius and the art of prorogation One of Louvain’s most outspoken proponents of Ptolemaic prorogation was Joannes Stadius (see chapter 7). In the introductory chapters of his Ephemerides, Stadius claimed that this technique offered the “chief fruit of predictions.”6 From the second edition (1560) onwards, his ephemerides contained four examples that proved its efficacy in predicting the recent deaths of local nobility.7 A good example is René de Châlon, the uncle of William of Orange, who died on 14 July 1544, aged 25, after a bullet struck him in the shoulder. In the dedicatory letter to Philip ii, Stadius reminded his patron of the prediction of this unexpected event by Franciscus Monachus (see chapter 5).8 In 1560, Stadius published and interpreted de Châlon’s birth chart to demonstrate that he too could provide such crucial information.9

6

Stadius, Ephemerides (1570), p. 16. These were Edward vi (1537–1553), René de Châlon (1519–1544), Ludovicus Brederode (1533–1557), and Aloisius Carvaialus (1520–1558). 8 Stadius, Ephemerides (1556), fol. a4r. 9 Stadius, Ephemerides (1570), pp. 30–33. 7

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A simple application of Ptolemy’s precepts for prorogation indicated that Mars was René de Châlon’s destructive planet or “anaereta,” which awaited the arrival of the sun (de Châlon’s prorogator) through a quartile aspect. Stadius calculated that this meeting would occur after 25 years, 5 months, and 12 days. However, this staggering fit with the actual events did not conclude Stadius’ analysis. Instead, he proceeded to determine “which causes assisted in impeding this assault, or else –also being afflicted- intensified the force of these threats.”10 Turning his attention to the other maleficent planet, Saturn, Stadius discovered that it cast a negative opposite aspect upon René de Châlon’s ascendent after 28 years and 2 months. Any potential objections that this postdated the actual death by almost three years were countered by invoking a number of techniques that Ptolemy detailed in Tetrabiblos iv.10. The application of these “profections”11

10 Idem, p. 31: “(…) Quae causae opitularentur, hunc assultum repressurae, aut minarum vehementiam ipsae quoque afflictae intenderent.” 11 The last part of Tetrabiblos iv.10 is devoted to a further refinement of the results of prorogation by means of “annual chronocrators.” See Tetrabiblos, p. 453. These are determined in order to enable the investigation of things awaiting the client in a particular year of his life. Ptolemy does not give a specific name to this complementary technique, which I will designate as “profection.” This follows the standard Latin term profectio, which seems to have been the standard translation for the Arabic intiha. Profections seem to have equipped the astrologer with a method to perform prorogations over a very brief time-span. Determining the annual chronocrator is done by, starting from the prorogator, counting up a number of signs (in the order of the signs) equal to the number of years since birth. The annual chronocrator is the planet that rules the sign one then arrives at. Ptolemy’s concise treatment left his Arabic successors with the task of turning profection into a practical technique. Some of the earliest descriptions of the use of profections are found in Omar’s De nativitatibus. Omar mainly used annual profections. He studied the 30° interval that started with the degree attained by the annual profection. Any planets or houses within this specific 30° interval of the birth chart signified a specific influence. The time in the year when this influence would manifest itself was estimated by converting each degree of this interval to approximately 12.175 days. See Omar of Tiberias, Three books on nativities, trans. Hand, pp. 39–40. The sign of the annual chronocrator (signum profectionis, burg al-muntaha) was sometimes taken as the starting-point for the determination of a monthly chronocrator. One does this by taking the number of months since birth, and adding these to the sign of the annual chronocrator at c. 28 days per sign. At least Cardano, however, used 30 days for each month, simply calculating 13 months or signs per year. See Cardano, Opera omnia, vol. 5, p. 362. The monthly chronocrator is the planet that rules the sign one eventually arrives at. From this sign, one can start to calculate a daily chronocrator by taking the number of days since birth and adding these to the sign of the month, at a rate of two and a third days per sign. Cf. Regiomontanus, Tabulae directionum (1552), vol. 3, fols. ζ4v-η1v. The necessary tables are printed on fols. l8v-m1v of the same volume.

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and planetary “transits”12 enabled Stadius to confirm the dire fate that his initial prorogation had predicted.13 Stadius located his expertise in the area of Ptolemaic prorogation, combined with the subsidiary techniques of Tetrabiblos iv.10.14 The same Ptolemaic practice was adopted to account for the deaths of Ludovicus of Brederode in 1557 and of Aloysius Carvaialus in 1558. 1.2. Particular experience and the reform of natal astrology Stadius’ publication of political particulars did not violate the strict distinction between public practice of reform and private prediction of particulars that characterized Louvain astrological reform. These political particulars were post factum explanations, not predictions. Moreover, Stadius seemed to impose standard epistemological strictures on the relevance of particulars, by carefully calibrating them against ancient authoritative traditions. This was done against parapegmata in the case of mundane astrology, and against Ptolemy’s Tetrabiblos for natal astrology. Such calibration occurred on two fronts. First, particular experience could function as testimony of a commonly accepted rule or effect. Second, particular experience could acquire its meaning in relation to an ancient process of discovery.15 Other astrological practitioners were less reserved in their public use of particular experiences. An interesting example is Girolamo Cardano, who was the first to publish a horoscope collection (1538).16 Cardano’s horoscope collections, like Joannes Werner’s weather records, contained much more than astrological data. Most

12 For a suitable, albeit contemporary definition of transits, see Gettings, Dictionary of Astrology, pp. 518–519. 13 Stadius, Ephemerides (1570), pp. 31–32. 14 Stadius warned his readers not to equate Ptolemy’s “transits” with the more common revolutions. His distrust of revolutions was based on empirical claims, and astronomical arguments about the precision of traditional solar theory. A more likely reason, however, is their association with annual prognostications. After all, Stadius happily identified Ptolemy’s “general chronocrators” with the popular Arabic alfridaria. See Stadius, Ephemerides (1570), pp. 32–33. Also note that textbook examples of astrological revolutions were included in Cornelius Gemma’s edition of his father’s treatise on the universal astrolabe, on the authority of ps.-Ptolemy. See Gemma Frisius, De astrolabo catholico, fols. 171r-175r. 15 This was the case in Stadius’ update of Ptolemy’s astrological star catalogue in the Tabulae Bergenses, as well as in Cornelius Gemma’s supposed use of his father’s astrological observations in the Ephemerides Meteorologicae. 16 Grafton, Cardano’s Cosmos, pp. 64–70.

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horoscopes also provided an elaborate astrological analysis. This explained their exceptional popularity. All over Europe, readers were allowed a celestial glance behind the scenes of political doom, intellectual genius, moral decay, or bodily charm. The horoscope collection became a literary genre that served both astrological clients and practitioners. The first group obtained a “Who is who in the Renaissance?” with powerful and homogenously structured biographies, while specialists mined its wealth of useful study material. At the pinnacle, however, stood Cardano himself, whose astrological expertise emerged from his readership’s agreement with the truthfulness of his analysis. Cardano’s original horoscope collection was a modest affair. Its ten horoscopes served as illustrations of the astrological precepts in Cardano’s Libelli duo (1538).17 However, the total already ran up to 67 in a revised and corrected edition that came out at Nuremberg in 1543. Four years later, another Nuremberg edition included a handsome collection of 100 birth charts as a separate book, rather than as an appendix. This indicates a tendency to privilege particular experiences as such, which is confirmed in Cardano’s dedicatory letter (1543): From this it is clear that even if Pico came back to life, astrology would not be uncertain.

Or: Even if you don’t believe in astronomy, this one geniture will convince you –unless you are an ass- that the art is not empty.18

Cardano suggests that his detailed recourse to particular experiences mirrored Pico’s detailed criticism of astrology. The Disputations had discredited the richness of common astrological experience through a staggeringly elaborate analysis of its precepts. Cardano retaliated with an overwhelming collection of experiences, hoping to convince his readers that at least some astrological precepts (provided in the rest of the Libelli duo) were valid. In doing so, he bypassed the epistemological strictures that Stadius imposed on his own particular experiences. This was a dangerous attitude, as Cardano found out when he analysed the birth chart of Edward vi in 1552. Cardano’s original reading predicted marriage and a steady rule for the young King. 17 18

See Ernst, “‘Veritatis amor dulcissimus,”’ pp. 44–46. Translations taken from Ernst, “‘Veritatis amor dulcissimus,”’ p. 57.

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Instead, Edward died in July 1553, even before Cardano’s interpretation was published.19 Cardano excused this glaring failure by insisting that a web of manipulative advisors around the young King had alienated him from court, well before he could complete a full analysis of Edward’s birth chart.20 Although the published account tried to integrate his additional findings, it was apparent that these were not entirely satisfying. Joannes Stadius gleefully emphasized this point in his own analysis of Edward’s birth chart. More specifically, he claimed that Cardano’s reading did not satisfy the rules of proper Ptolemaic practice in two respects. The first issue concerned the determination of Edward’s exact time of birth, which Ptolemy had taught in Tetrabiblos iii.2.21 Stadius disputed Cardano’s application of this precept because it was unsuitable for Edward’s unnatural birth through Cesarean section. Another problem was Cardano’s choice of prorogators. Although he initially opted for Saturn and Venus as prorogators, his mistake later enticed him to focus on the sun and moon. Again, Stadius unmasked this as a violation of Ptolemy’s rules.22 Stadius’ alternative reading of Tetrabiblos led him to propose the ascendent as Edward’s true prorogator, and Saturn as his destroying planet.23 He continued:

19 Published among the twelve genitures that were appended to his commentary on Tetrabiblos (1554). See Cardano, Opera omnia, vol. 5, p. 507. On this episode, see Grafton, Cardano’s Cosmos, pp. 115–123; Ernst, “‘Veritatis amor dulcissimus,”’ p. 40. A similar problem arose in Cardano’s analysis of the birth chart of Aimar de Rançonnet. 20 Grafton, Cardano’s Cosmos, pp. 122–123. 21 Tetrabiblos, pp. 233–235: “If the distance of the degree occupied by the ruler from that of the general horoscope is greater than its distance from that of the corresponding mid-heaven, we shall use this same number to constitute the mid-heaven and thereby establish the other angles.” Cardano, Opera omnia, vol. 5, p. 507: “De vero tempore geniturae. Saturnus fuit dominus loci novilunij & ipse fuit in decimaseptima parte signi, ideo etiam coeli medium.” 22 Cardano, Opera omnia, vol. 5, p. 507. Ptolemy stated that only planets in the first, seventh, ninth, tenth, or eleventh houses could function as prorogators, which was not where Cardano situated the sun and moon in Edward’s birth chart. See Tetrabiblos, p. 273. 23 Ptolemy states that the method of prorogation “in the order of the following signs” (counter to the diurnal motion) is fitting when the prorogator is between ascendent and mid-heaven. He also states that Saturn and Mars are the proper anaeretae for this kind of progression. In Edward vi’s chart, both are in the vicinity of the horoscope, Mars to the west and Saturn to the East. Thus, only Saturn will meet the prorogator when carried along by the diurnal movement. See Tetrabiblos, pp. 279–283.

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chapter eight Now, since it is clear that the ascendent is the prorogator of life, and the closely approaching Saturn the ascendent’s destructive place; and since the outcome has shown that Edward lived for only 15 years and almost nine months, who would deny that the oblique ascensions should be determined in such a way that the destructive planet Saturn would meet the prorogator at that point in time?24

Stadius solved the puzzle of Edward’s birth chart by forcing its empirical parts to fit Ptolemy’s precepts. He did this by means of an alternative method to determine the time of birth. Although Ptolemy had not described this technique, several astrological textbooks mentioned it as a more reliable method.25 This technique recommended that the birth chart be recalculated in such a way that its basic data (the degree of the ascendent) would fit subsequent empirical data (Edward’s death at the age of fifteen years and nine months). In other words, individual history was to provide feedback on the quality of the astrologer’s basic data. Stadius first determined that Saturn was in Virgo 15;53° on 11 October 1537. Subtracting 15;44° (the astrological equivalent of fifteen years and nine months) from its oblique ascension, he derived that the true ascendent of Edward’s birth-chart was Virgo 4°, instead of Cardano’s Leo 17°.26 Once again, this shows how Stadius’ public practice subordinated particular experiences to the exploration of ancient common precepts.27 Unfortunately, another problem would soon confront this typical Louvain reformist attitude: the complexity of ancient authority.

24 Stadius, Ephemerides (1570), p. 28: “Nunc quum constet Horoscopum hic esse vitae prorogatorem, & Saturnum obviaturum proxime ut anaretam Horoscopo: & eventus docuerit vixisse tantum annis quindecim, & mensibus fere novem, quis negaverit ita constituendas ascensiones obliquas, ut proxime ad tale tempus Saturnus anareta Significatori occurat?” 25 See Schöner, De iudiciis nativitatum, fols. 3r/v. 26 Stadius, Ephemerides (1570), pp. 28–29. 27 Note that Stadius also adopted the strictly Ptolemaic practice that he publicly advocated in his private astrological practice. This is clear from his manuscript analysis of the birth chart of Justinus of Nassau (18 March 1562?-1631), son of William of Orange, which was written at Ghent on 25 June 1571. This astrological report is preserved in Leiden, University Library, Codex Vulcaniani 32. Stadius, Joannes. Genitura Justini de Nassau. Ghent, 25 June 1571. It was published in De Bas, “Horoskoop van Justinus van Nassau (1559–1631).” See, for instance, Stadius’ prediction for 20/21 August 1579 in this document.

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2. House division, prorogation, and the search for Ptolemaic authority 2.1. Regiomontanus’ restoration of Ptolemaic prorogations Shortly after his arrival at the court of Mathias i Corvinus (1440– 1490), the German mathematician Regiomontanus finished one of the most successful tools of sixteenth-century astrology: the Tabulae directionum et profectionum (1467).28 He claimed that these tables restored Ptolemy’s intended method of prorogation, which had not been divulged in Tetrabiblos for reasons of calculatory ease: Considering that it is preferable to be close to what is true than to despair in seeking the truth in its fundaments, he [=Ptolemy] explained some short calculations that came close to the truth.29

This refers to Tetrabiblos iii.10, where Ptolemy described how a person’s lifespan could be calculated by measuring the number of equinoctial degrees between prorogator and “anaereta,” converting these degrees to years at a rate of one year per degree. Ptolemy was notoriously unclear, however, about the precise method by which the common ecliptic position of prorogator and “anaereta” (i.e., their longitude) should be converted to equinoctial degrees: A place is similar and the same if it has the same position in the same prorogation with reference both to the horizon and to the meridian. This is most nearly true of those that lie upon one of those semicircles that are described through the sections of the meridian and the horizon.30

In this highly influential passage, Ptolemy recommends using socalled “position semi-circles” to make this conversion. These position semi-circles are great circles that pass through both intersections of meridian and horizon. The equinoctial position of a point 28 Joannes Regiomontanus (1436–1476) studied at the University of Vienna under Georg Peurbach, whom he assisted in his astronomical studies after his appointment in 1457. Among Regiomontanus’ most important mathematical works are an Epytome Almagesti, De triangulis omnimodis, the Tabulae directionum et profectionum and a set of Ephemerides for the years 1475 to 1506. See Zinner, Regiomontanus; Rosen, “Regiomontanus, Johannes” in: Gillispie (ed.), Dictionary of Scientific Biography, vol. 11, pp. 348–352; Graf-Stuhlhofer, “Tradition kontra Empirie”; Swerdlow, “Regiomontanus on the Critical Problems of Astronomy.” 29 Regiomontanus, Tabulae directionum (1552), vol. 1, fol. b1v: “Satius ergo putans prope verum versari, quam veritatem ipsam radicitus quaerendo desperare, supputationes quasdam breves veritati propinquas exposuit.” 30 Tetrabiblos, p. 291.

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Figure 1. Regiomontanus’ restored Ptolemaic prorogations

on the ecliptic (in this case, the prorogator and “anaereta”) is determined by the point of intersection of the equator and the position semi-circle that passes through this ecliptic point. If we plot these equinoctial points for prorogator and “anaereta,” then the equatorial arc between them indicates the number of years (figure 1). Unfortunately, position semi-circles are rather cumbersome to calculate. Ptolemy therefore proposed the use of unequal hour-lines as a practical alternative. He legitimated this by saying that position semi-circles “at the same position make nearly the same temporal [i.e., unequal] hour.”31 Regiomontanus claimed to conclude 1300 years of approximate practice, by providing a tool for the implementation of Ptolemy’s position semi-circles.32 2.2. Prorogation and astrological house division Regiomontanus’ return to Ptolemy’s “authentic” method of prorogation had considerable consequences for another crucial concept of astrological practice: the astrological houses. In their earliest development, astrological houses enabled practitioners to account for the 31

Ibidem. There is some evidence that Regiomontanus’ idea was plagiarized from a lost treatise on prorogations by the Albanian astrologer Gin Gazul, on whom more later. The French mathematician Oronce Finé, who defended Gazul against Regiomon32

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Figure 2. “Equatorial (fixed boundaries)” or “Regiomontanus” houses

local differences in visibility of the heavens.33 The Western tradition codified this into a division the heavens in twelve zones or “houses.” Although different methods of house division are known, all have at least two reference-points in common: the local eastern horizon constitutes the “cusp” (dividing line) of the first house, while the local western horizon determines the cusp of the seventh house. While the planet’s positions in the zodiac at a specific time provide a gentanus, already deplored the unavailability of Gazul’s treatise in his De duodecim caeli domiciliis (1553), fol. 8r. First, consider the fact that both Regiomontanus and Gazulus invoked the authority of Haly Abenragel, De iudiciis astrorum iv.7, as Regiomontanus tells us: see Regiomontanus, Ratio, fol. v3r; Regiomontanus, Tabulae directionum (1552), vol. 1, fol. b1v. Second, consider that both authors seem to connect their different proposals on house division with the practice of prorogation. This could imply that Gazulus’ unpreserved proposal on prorogation was very similar to the later one by Regiomontanus. Both Regiomontanus’ equatorial houses and Gazulus’ prime vertical houses are constituted by means of position semi-circles. Hence, both their proposals on prorogation probably used position semi-circles. On Gazul, see Grmek/Dadic, “O astronomu Ginu Gazulu I dubrovackom traktatu o astrolabu.” 33 The indispensable study on house division (domification) is North, Horoscopes and History. This book provides a typology of methods of domification as well as an interesting survey of medieval and renaissance doxographies of domification. Edward Kennedy has elaborated North’s typology from medieval Islamic sources in “The Astrological Houses as Defined by Medieval Islamic Astronomers.” Very interesting material related to the genesis of house division in Greco-Roman practice is collected in Neugebauer/Van Hoesen, Greek Horoscopes.

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eral account of celestial influence, their position within the houses “translates” this influence to the observer’s specific position, which is latitude-dependent. According to John North, “almost all medieval western horoscopes, at least before the late fifteenth century, are cast according to the standard method.”34 This common medieval practice changed in the late fifteenth century.35 By the 1530s, “equatorial” house division (promoted by Regiomontanus) seems to have become the new standard for European astrologers (figure 2). However, two alternative systems frequently opposed this monopoly: the “single longitude” and “prime vertical” methods. By that time, standard domification had become notably absent from the astrological scene. The introduction of alternative methods of domification was already exploited in Pico’s Disputationes, which questioned both the natural philosophical basis of astrological houses and the contradictions on this matter in the astrological canon.36 After Pico, Latin astrologers invested great effort in dealing with the multiplicity of methods. This seems to have occurred in two stages. At first, the debate acknowledged several methods on the basis of either ancient lineage or contemporary practical habits. These different methods were allowed to co-exist, and attempts were made to relegate them to different areas of astrological practice. The second stage of the discussion abandoned this conciliatory attitude. Instead, the goal was to identify a new “standard method” for the early modern period. This development was intimately linked to the ambitious claims of astrologers like Stadius about their genethliacal expertise. 2.2.1. Abandoning the standard method: Regiomontanus and Ptolemy An obscure Albanian called Gin Gazul composed the earliest known Latin critique of the standard method of domification.37 Around the middle of the fifteenth century, this Gin Gazul (d. 1465) sent an explanation of his alternative “prime vertical” method to the court of the Hungarian King Matthias i Corvinus. Regiomontanus, who worked at Corvinus’ court with Martin Bylica from 1467 to 1471, probably learned of Gazulus’ proposal there. Although Gazulus’ tract De directionibus has not been preserved, some of its content can

34 35 36 37

North, Horoscopes and History, p. 42. Ibid., pp. 155–156. These criticisms are further developed in Disputationes, chapters vi.3 and ix.7. This section expands upon North, Horoscopes and History, pp. 27–30.

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be derived from Regiomontanus’ disparaging remarks in the Tabulae directionum (1467) and his posthumously published Ratio, sive ˆπÞδειξισ duodecim domorum coeli (1536).38 Regiomontanus’ description suggests that Gazulus had described his system without providing a calculatory algorithm for its actual use. Regiomontanus solved this problem by calculating the necessary tables and inserting them in his Tabulae directionum. Ironically, he thus seems to have become the single most important propagator of the prime vertical-method he set out to refute.39 Regiomontanus consistently presented his “equatorial (fixedboundaries)” houses and position semi-circle prorogation as part of a single package. This remained the predominant mode of reception of the two theories in the Renaissance. For most practitioners, using Regiomontanus’ position semi-circles in prorogation also implied their use for house division. Why did Renaissance astrologers adopt such strong preferences for a unified practice? Regiomontanus provides an interesting clue in the preface to his tables of prorogation, where he criticizes “some archdeacon from Parma” for having recommended two ways of determining prorogations. The first involved a simple manipulation of celestial globes, equipped with position semi-circles. The second recommended calculation by means of unequal hour-lines, i.e., the method that Ptolemy described.40 Regiomontanus’ anonymous archdeacon was probably Matteo Guarimberto, whose tract on prorogations, aspects, and rays (printed in 1534) was available in numerous manuscripts.41 Among Louvain instrument makers of the sixteenth century, it was still customary to fit globes with position semi-circles in order to perform both prorogations and equatorial house divi-

38 Regiomontanus, Tabulae directionum (1552), vol. 3, fol. δ3r (probl. xvi): “[Joannes Ragusinus] igitur postquam opinionem Campani sectari decrevit, documentum edidit aequandarum domorum, idoneum quidem propositio suo ac geometricis fundamentis stabilitum.” The French mathematician Oronce Finé, who defended Gazul against Regiomontanus, already deplored the unavailability of Gazul’s treatise in his De duodecim caeli domiciliis (1553), fol. 8r. On the history of Regiomontanus’ tables of prorogation, see Zinner, Regiomontanus, 91–97. 39 Regiomontanus, Tabulae directionum (1552), vol. 3, fols. δ3r/v. 40 See Regiomontanus, Tabulae directionum (1552), vol. 1, fol. b1v. 41 In the prospectus of forthcoming books from his Nuremberg press, Regiomontanus also listed an otherwise unknown tract on prorogations against Guarimberto (see Zinner, “Die wissenschaftliche Bestrebungen Regiomontans”). Guarimberto’s treatise was included in Camerarius’ influential editio princeps of Tetrabiblos (1535).

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sion. The comments on Guarimberto reveal that fifteenth-century globes already integrated these functions prior to the publication of Regiomontanus’ tables of prorogation. This suggests that Regiomontanus intended to supplant an existing tradition of instrument-based astrological practice.42 Within these traditions, it was more customary that a single feature served multiple functions. Medieval astrologers, for instance, often determined the cusps of standard houses by means of an astrolabe’s unequal hourlines.43 It is not unlikely that the same attitude favored the application of position semi-circles in both prorogation and house division well before Regiomontanus’ Tabulae directionum. Likewise, Gazul and Regiomontanus could easily have interpreted chapter iv.7 of Abenragel’s Liber in iudiciis astrorum as pertaining to both prorogation and house division.44 This interpretation seems to be confirmed by canon 16 of the Tabulae directionum, where Regiomonantus presents the construction of astrolabes as an argument against Gazul’s use of position semi-circles with equal spacing along the prime vertical.45 Finally, one may note that the astrolabe, offered by Regiomontanus to Cardinal Bessarion in 1462 (five years before the tables of prorogation were finished), was already equipped with equatorial house divisions.46 Prorogation provided a genethliacal practice that was based on a unified set of quantified parameters (equatorial positions of prorogator and “anaereta”). Imitating instrument-based traditions, Regiomontanus’ equatorial house division expanded these unifying strategies into the domain of house division. Through the Tabulae directionum and its promotion of position semi-circles, astrologers could rely on a single method to determine both the equatorial positions of prorogator and “anaereta,” as well as the house cusps. This 42 As early as the fourteenth century, Latin texts on celestial globes (the sphera solida) described its astrological functions as the “perfection” of this instrument. See Lorch, “The sphera solida and Related Instruments,” p. 156. 43 North, Horoscopes, pp. 58–59. 44 Another reinforcing factor may have come from Ptolemy himself, who made his most elaborate remarks on astrological houses in the context of discussions of prorogations in Tetrabiblos iii.10. See my analysis of the Stadius-Peletier debate on this matter. 45 Regiomontanus, Ratio, fol. v3v: “Item contra Campanum de horis inaequalibus contra mentem Ptolomaei, itemque Hipparchi, qui observationes suas scripsit per horas temporales. Item contra facturam Astrolabij. Item propter intricatam horarum talium discretionem.” 46 See the plate for latitude 48°: King/Turner, “The Astrolabe Presented by Regiomontanus,” figure 1 (following p. 192).

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enables us to understand why Renaissance astrologers commonly referred to Regiomontanus’ equatorial house division as the “rational” method: to an unprecedented degree, it enabled a mathematical and instrument-based unification of genethliacal practice. As was customary in early modern medicine, the theoretical credentials of mathematics provided an attractive means to legitimize judicial astrology.47 Regiomontanus’ concern with the theoretical legitimacy of astrological practice stands out in his arguments against Gazul’s proposal on house division. His first argument was naturalphilosophical, claiming that astrological houses should indicate the inherent quality of specific zones in the local sky.48 The second argument was aesthetic and hinged on the physical pre-eminence of the equator and the harmony of equatorial houses.49 2.2.2. Coexisting traditions. Gemma Frisius on house division As early as 1530, Gemma Frisius’ cosmographical textbooks commented on the collapse of the medieval standard method of house division (see chapter 5). Gemma returned to this topic in his posthumously published De astrolabo catholico (1556), a tract on the universal astrolabe.50 When Gemma’s son dedicated the published tract to Philip ii, it probably came with an outstanding example of this astrolabe, built by Gemma’s nephew Gualterus Arsenius (c. 1530–1580).51 47 Compare to Maclean, Logic, Signs, and Nature, p. 181: “It would seem that the application of the rules of quantification is subsequent to the act of judgement known as indication (…), and hence is a post hoc justification of such acts rather than the producers of them.” 48 Regiomontanus, Tabulae directionum (1552), volume 3, fol. δ3r: “Nam ex multis pauca decerpantur, spacia domorum hac lege distinctarum magnitudines certas ac firmas servare nequeunt, quas profecto servandas esse confiteberis, si circa influxus aut proprietates huiusmodi domorum recte philosophari libeat”; Idem, Ratio, fol. v2v: “Talem quoque surrepticiam, & confusum domorum influxum, aut tam incertam proprietatem, sive etiam significationem in reliquis quoque coeli domicilijs est invenire.” 49 Regiomontanus, Ratio, fol. v3v. 50 On the universal astrolabe, see Poulle, “Un instrument astronomique”; North, “Werner, Apian, Blagrave and the Meteoroscope.” 51 It is most likely that the 1556 Arsenius astrolabe, which is preserved in the Leonard Linton collection (New York, ic 454), was offered to Philip ii with a copy of De astrolabo catholico. The throne of the 1556 astrolabe bears the arms of both the Habsburg and the Tudor families, which is a direct reference to the marriage of Philip ii and Mary Tudor in July 1554. Several astrological comments on this marriage can be found in De astrolabo catholico. The description of the parts of the astrolabo catholico also matches the preserved Arsenius-astrolabe (Gemma Frisius, De astrolabo, fols. 10r-11v). One difference between both concerns the sliding cursor, which Gemma’s treatise mysteriously describes as bearing graduations up to 1000.

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Among the many functions of the universal astrolabe was the division of the zodiac in astrological houses. Gemma Frisius devoted ten chapters to this, two of which contain extensive comments on the underlying problematic (chapters 50 and 56). In chapter 50, Gemma confessed his confusion over the impressive credentials of different methods of domification: Students will perhaps expect my opinion in this important controversy. (…) I foresee difficult considerations, [since] the authors who fight over this matter follow contrary and conflicting opinions, whose authority nonetheless carries great weight.52

Nevertheless, Gemma was prepared to narrow the choice down to two options, the equatorial and single longitude methods. Like Regiomontanus, Gemma interpreted Ptolemy’s Tetrabiblos iii.10 in favor of the equatorial system, aware that contemporary astrologers like Girolamo Cardano and Cyprianus Leovitius (1524–1574) recently advanced a similar interpretation.53 But exactly the same criteria (antiquity and contemporary use) could be invoked in favor of the single longitude method. Indeed, single longitude domification had recently found a strong advocate in Joannes Schöner, who defended it in his textbook De iudiciis nativitatum (1545). An alternative interpretation of certain passages in Tetrabiblos and Centiloquium enabled Schöner to reclaim Ptolemy for the doxography of single longitude house division.54 Another authoritative text that was clearly in favor of single longitude houses was Firmicus Maternus’ Mathesis (courth

In several copies of the treatise (e.g., Louvain University Library, CaaA3), this number was manually corrected to 100, which matches the ruler of the Linton astrolabe (separately preserved in Bielefeld, Kunstgewerbesammlung). On this astrolabe and its context, see Van Cleempoel, “The three ‘Spanish’ astrolabes of Gualterus Arsenius.” 52 Gemma Frisius, De astrolabo, fols. 85r-86v: “In hac non levi controversia fortasse studiosi meam expectabunt sententiam. (…) Rationes video difficiles. Auctores in re ipsa pugnantes & contraria seu pugnantia sequentes, quorum etiam auctoritas non levis est ponderis.” 53 Gemma Frisius, De astrolabo, fol. 85v. Gemma’s reference to the Ptolemaic origins of equatorial house division is at fols. 93v/94r. 54 Schöner adduces loci from Tetrabiblos iii.9, iii.10 and iv.5, as well as aphorism 37 of the Centiloquium. One may note that only aphorism 37 and the two passages from iii.10 (both at Tetr. m 128) are easily interpreted as matching single longitude domification. Schöner’s reading of the two other loci grants certain unsubstantiated assumptions (e.g., interpreting the culminating point of the zodiac, not the intersection of zodiac and meridian, as one of the four κÛντρα).

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century). Among more recent writers, Schöner mentioned Giovanni Pontano (De rebus coelestibus ii.1)55 and Patricio Tricasso da Cerasari.56 Schöner attached more weight, however, to the utility of single longitude houses in astrological practice. More specifically, he contested Regiomontanus’ emphasis on the subservience of astrological houses to the practice of prorogation: For the reason underlying the signification or influence of the twelve houses, which the inventors of astrology seem to relate to the zodiac, is different from that underlying times and prorogations. The latter should comply with the former indications, and should not rule or be preferred. For the philosophers agree that the motion of the stars that we consider in the zodiac is the cause of birth and death. In fact, even the ignorant know that time comes forth from the motion which is effected by the sun, and belongs to it. This is almost an observational fact, which the mathematician should not doubt.57

Schöner linked astrological houses to a more traditional astrological practice that focused on the qualitative analysis of the various elements of a birth chart, rather than the chronological reading that was central to prorogation. Schöner’s textbook primarily used astrological houses to qualify the influence of zodiacal signs and planets in a birth chart. This made it desirable, in his opinion, that the common referent for the position of signs and planets (the ecliptic) would also be used to determine the position of houses.58

55 Pontanus actually did not say much about the mode of domification beyond the constitution of the four angles. From his assertion that the distance between two angles is not always 90 degrees, it should however be obvious that he did not uphold single longitude domification. See Pontanus, De rebus coelestibus (1519), fol. 129r. 56 The technique of revolutions, which revolves the natal chart by assuming a division of the zodiac in equal houses of 30° each, was also adduced as favorable evidence. See Schöner, De iudiciis, fol. o5v. 57 Schöner, De iudiciis, fol. o5v: “Alia est enim ratio significationis qualitatis, aut influentiae duodecim locorum coeli, quae ab inventoribus Astrologiae ad zodiacum relata esse apparet, alia temporum ac directionum, quae illis subservire non praeferri, aut imperare debent. Motum enim stellarum quae in zodiaco consideramus & nascendi, & moriendi causam esse constat inter philosophos: tempus vero fluere e motu, esseque eius, quasi observationem quandam, non est Mathematici dubitare, cuius autorem esse Solem etiam indocti vident.” 58 Even so, the ubiquity of Regiomontanus’ equatorial method compelled Schöner to implement them in several sample-genitures, while claiming that personal experience indicated the superiority of single longitude division. Schöner, De iudiciis, fol. o5v.

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This clarifies the source of Gemma Frisius’ confusion in the 1550s. Instead of engaging with Schöner’s discussion on the true nature of astrological practice, Gemma allowed both opinions to coexist: The method of Joannes Regiomontanus, that man of sharp wits, seems more commendable to me. It has more probable physical accounts, tried by long experience. Still, the other mode of using equal parts of the zodiac, which Firmicus consistently followed, does seem worthy of attention. This method also enables one to perceive indications of many events, due to the forces of the configurations of those houses with the ascendent, which are known through experience. Through the former method we would judge the virtues of the stars, comparing the [equatorial] houses (stationes) with the stars. And we would observe the indications of configurations through the latter mode.59

Gemma distinguishes two different types of astrological interpretation. The first relates the virtues of celestial bodies to the (equatorial) houses. The second prefers to connect (single longitude) houses with the mutual “configurations” of celestial bodies, i.e., with their aspects and rays. This distinction, different from Schöner’s position, was strangely reminiscent of Pico’s critique in chapter vi.3 of the Disputations. Pico’s physical analysis claimed that the virtues of astrological houses could either be construed in relation to inherent virtues of different parts of the heavens, or in relation to the variable radiation of planetary virtues with respect to local terrestrial horizons.60 One could assume that Gemma intended to connect equatorial houses with the first interpretation, and single longitude domification with the second. The threat of astrological criticism also seems to have informed Gemma’s slight preference for Regiomontanus’ equatorial method at the beginning of his previous statements. In another passage, Gemma explained that he wished to avoid a wholesale slandering of the art:

59 Gemma Frisius, De astrolabo, fols. 86r/v: “(…) Probari mihi magis rationem Ioannis Regiomontanis viri perspicacissimi, quae physicas habeat rationes probabiliores & longa magis experientia comprobatas, quanquam mihi & alter modus partibus zodiaci aequalibus utens, quem omnino Firmicus sequitur, non videatur prorsus negligendus: ex quo etiam multorum eventuum significationes accipiuntur, propter configurationum harum partium cum horoscopo vires experientia ipsa notas. In illo enim modo stellarum vires magis iudicamus, cum stationes has cum illis conferimus. In isto autem, configurationum significationes observamus.” 60 Disputationes, vol. 2, p. 22.

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These things I wanted to add in favor of Regiomontanus, so that students of astrology would not waver in a matter that is sufficiently certain, and adversaries would not obtain an opportunity to slander this honorable study (…).61

The Louvain context makes it likely that Pico was central to Gemma’s thoughts went he mentioned these “adversaries.” 2.2.3. The collapse of textual authority as a token of expertise Gemma’s pupil Joannes Stadius was more adamant about the issue of house division: This varied and fleeting distribution of figures occasioned much uncertainty and unsuspected error in astrology, while each man twists the respected examples and judgments of the ancients to recently invented and devised houses. (…) Would a heedless judge, having inconsiderately followed the opinion of Ptolemy, not attribute the prorogation of life to the sun or moon as he finds them in the ninth or eleventh house according to these methods? While another, having taken up his own method to erect the same chart, will find the sun or moon cast down in the twelfth or eighth house, close to the cusps of the houses, and will plausibly reject them on the same authority in his choice of prorogation? Will he lose himself in the entire sky?62

The prime purpose of astrological houses was to assist the making of correct Ptolemaic prorogations, Stadius wrote. Likewise, a correct method of domification was to be tested against its conformity with the latter technique. Contrary to Regiomontanus, however, Stadius claimed that Ptolemy never intended any other system than the unequal hour-line prorogation that Tetrabiblos iii.10 had described.63 Consistent with his own opinion, he assumed that Ptolemy also intended to use the rare unequal hour-line method of house division.64 61 Gemma Frisius, De astrolabo, fol. 84 r: “Haec sunt quae pro Regiomontano adiicere volui, ne deinceps fluctuent in re satis certa studiosi astrologiae, aut ne immerito ansam habeant calumniandi honestum hoc studium adversarij (…).” 62 Stadius, Ephemerides (1556), fol. b3v: “Peperit haec figurarum varia fluxaque distributio multum incerti in astrologia & non considerati erroris, dum singuli veterum exempla & iudicia observata ad sua domicilia nuper inventa & excogitata detorquent, (…) Anne improvidus iudex Soli aut Lunae, Ptolomaei suffragium inconsiderate secutus, vitae prorogationem attribuet, quum illos iuxta horum modorum aliquem in nona aut undecima deprehenderint? Alter vero, sibi peculiarem in eadem erigenda figura modum secutus, Solem aut Lunam videbit iuxta domorum interstitia in 12 aut 8 abiectos esse, atque illos eodem suffragio in hac prorogationis electione probabiliter reiiciet? totoque coelo aberrabit?” 63 Ibid., fols. b3v–b4r. 64 Ibid., fol. b4r. Although Stadius initially seemed to advocate Regiomontanus’

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In doing so, Stadius created a new problem. Position semi-circles were easy to handle in domification, but relatively cumbersome for the purpose of prorogation. The mathematical complexity of unequal hour-lines, however, made them unsuitable for the determination of house-cusps, while providing effortless prorogations.65 This is why Stadius advised his readers to use Regiomontanus’ equatorial houses. As far as we know, his promise to resolve the problem in a commentary on Tetrabiblos, never materialized.66 Stadius’ return to Ptolemy’s attested practice also provided him with a motive to contest Cardano’s pan-European fame. As we know, the latter publicized large collections of particular experiences to stake his expertise in natal astrology. His public failure to predict the deaths of Edward vi or Aimar Rançonnet also exposed the increased risks that this strategy entailed. Imitating Cardano’s horoscope collections, Stadius seized this opportunity to stake his own claims as a practitioner. Using his slightly altered technique of prorogation, Stadius published an analysis of Edward’s birth chart that demonstrated his ability to do better than Cardano in predicting unexpected deaths precisely. This message attracted considerable opposition from other astrologers. First, they implemented the debate on house division to problematize Stadius’ emphasis on the practice of prorogation. In second place, they appealed to particular experience to undermine public trust in Stadius’ claims. Both procedures agreed in their simple reversal of Stadius’ own strategies. The first attack on Stadius came from the French mathematician Jacques Peletier (1517–1582).67 In his treatise De constitutione

equatorial houses, he proceeds to define positions in a specific house outside the equator with respect to the degrees of unequal hours. This proves clearly that Stadius’ preferred system of house division involved unequal hour-line domification. The last part of Stadius’ remarks is reminiscent of a passage from Abraham Ibn Ezra’s Libro de los fundamentos de las tablas astronomicás, cited in North, Horoscopes, p. 24. 65 By means of a table of oblique ascensions and a table of houses for latitude 51°28’ taken from the Tabulae directionum, Stadius gives a worked example of the calculation of houses in the Regiomontanean mode. See Stadius, Ephemerides (1556), fols. b4v-c1v. 66 Stadius, Ephemerides (1556), fol. b4v. 67 J.J. Verdonk, “Peletier, Jacques” in: Gillispie (ed.), Dictionary of Scientific Biography, vol. 10, pp. 493–495 provides a general introduction to the biography, bibliography, and studies of Peletier, who, “working alternately as a teacher in mathematics and as a surgeon, devoted his life to poetry and science.” The tract on horoscopes, De constitutione, was the last in a volume of three treatises published in Peletarius, Commentarii tres (1563), pp. 49–72. This is the only known edition of the third treatise.

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horoscopi (1563), Peletier successfully undermined Stadius’ claims of practising natal astrology in an authentic Ptolemaic vein.68 His main argument derived from a text-critical study of the Greek text of Tetrabiblos.69 Peletier first turned to chapter iii.10, the locus classicus around which Regiomontanus and Stadius had constructed their case that Ptolemy reckoned houses in equatorial, not ecliptic degrees. Peletier pointed out how Ptolemy, in the beginning of this chapter, seemed to state that the eleventh house stood in sextile (i.e., 60° apart) to the ascendent, the tenth house in quartile (i.e., 90° apart), and the ninth house in trine (i.e., 120° apart).70 Stadius’ examples, however, allowed Aquarius to be in the tenth house with Gemini in the ascendent. In the birth chart of René de Châlon, this yielded a difference of more than 114°.71 Stadius solved this problem by suggesting that “Ptolemy set down double aspects, one in the zodiac, and the second in the equa-

68 It should be pointed out that Peletier’s De constitutione horoscopi never used Stadius’ name. There is ample evidence, however, that the treatise was directed against Stadius. First, Peletier claimed to defend the single longitude method against “those who uphold Abraham Ibn Ezra and Regiomontanus as their assertors” (p. 57) – the exact same doxographical lineage that Stadius claimed for himself. Second, several of the Ptolemaic interpretations that Peletier refutes are found almost verbatim in Stadius’ ephemerides. Compare Peletier, De constitutione horoscopi, p. 60: “Nonnunquam, inquit ille, è Signis longarum ascensionum depravatus Hexagonicus interficit: rursusque è Signis brevium Trigonicus depravatus” with Stadius, Ephemerides (1556), fol. b4r: “Non negamus etiam Ptolomaeum duplices constituere aspectus, in Zodiaco alterum, atque in aequatore secundum, & potissimum quidem ubi sextilem tardarum ascensionum, & trigonum brevium indicat.” Third, Peletier’s choice of examples seems specifically directed against those in Stadius’ Ephemerides. Compare Peletier, De constitutione, p. 60: “Itaque qui Abrahami Avenesrei & Regiomontani opinionem secuti sunt, quum non possent Ptolemaeum Ptolemaeo conciliare, neque viderent quo pacto duae illae sententiae stare possent: nimirum, decimum locum secundum aequales Zodiaci sectiones tetragonicis radijs Ascendens respicere, & ascendente Geminorum Signo, Aquarium esse in medio Coeli” with the birth chart of René de Châlon in Stadius, Ephemerides (1560), fol. c4r, where the sun (Aquarius 25;21°) casts trine rays upon Mars (Gemini 23;35°). Fourth, only Stadius seems to have felt the necessity of replying to Peletier’s allegations, and still experienced this need in 1570, when the new edition of his Ephemerides came out. 69 Peletier, De constitutione, p. 51. 70 See Tetrabiblos, p. 273. 71 Peletier, De constitutione, p. 60: “Itaque qui Abrahami Avenesrei & Regiomontani opinionem secuti sunt, quum non possent Ptolemaeum Ptolemaeo conciliare, neque viderent quo pacto duae illae sententiae stare possent: nimirum, decimum locum secundum aequales Zodiaci sectiones tetragonicis radijs Ascendens respicere, & ascendente Geminorum Signo, Aquarium esse in medio Coeli (in quo nihil esse absoni ostendemus) finxerunt duplicem aspectuum rationem: unam in Ecliptica, alteram in Aequatore: eosque mixto modo considerandos esse.” Stadius’ birth chart

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tor.”72 Peletier made a much more ambitious claim that the difficulty could be solved by re-interpreting Ptolemy’s references to the “midheaven” or cusp of the tenth house (medium coeli), which Stadius identified with the astronomical meridian. He found the basis for his argument in a passage in Tetrabiblos iii.2.73 This passage did not refer to the meridian as “midheaven,” but as “that which is similar to midheaven” (κατa τe µοιον µεσουρÀνηµατι).74 This also explained Ptolemy’s statements on “the remainder of the angle itself,” rather than “the angle,” as the habitual Latin translations had it.75 Furthermore, Ptolemy also referred to ascendent, meridian, and descendent as “these three limits,” not “these three angles.”76

for René de Châlon had the sun in the ascendent (Aquarius 25;21°) cast trine rays upon Mars on the cusp of the tenth house (Gemini 23;35°). 72 Stadius, Ephemerides (1560), fol. b4r: “Non negamus etiam Ptolomaeum duplices constituere aspectus, in Zodiaco alterum, atque in aequatore secundum, & potissimum quidem ubi sextilem tardarum ascensionum, & trigonum brevium indicat.” Stadius refers to Tetrabiblos iii.10, and interprets this passage as mentioning equatorial aspects. Peletier, De constitutione, p. 60, replies: “Verba enim haec, E Signis longarum ascensionum aut brevium, nil aliud notant quam Signa Zodiaci quibus competunt longae aut breves ascensiones,” and adds: “Insuper si aspectus sint in Aequatore, non erit Hexagonicus unquam ab Hexagonico diversus, sive longas sive breves ascensiones spectemus” (p. 61). 73 Peletier, De constitutione, p. 64: “Venio ad postremam illam clausulam: quae si ab Interpretibus fideliter esset conversa, nihil fortasse scrupuli inijceret.” Here as elsewhere in the text, Peletier quotes the Greek text of Tetrabiblos, adding a Latin translation of his own which is indebted to Operis Quadripartiti, trans. Gogava (1548). Comparing Peletier’s translation of the relevant passage in Tetrabiblos iii.2 with that of Gogava, shows how the former adds original nuances to this translation. Compare Peletier, De constitutione, p. 63: “Si vero fuerit maior partium distantia ab ea quae est circa integrum Horoscopum parte, quam ab ea quae circa simile Medio Coeli, eundem numerum ad partem Medij Coeli constituendam usurpabimus: & secundum eam, id quod reliquum est ipsius anguli, conficiemus” to Operis Quadripartiti, trans. Gogava, fol. h4v: “Verum sane ubi huius dominationis partium distantia maior invenitur a posito horoscopo, quam a medii coeli cardine, tum eodem partium numero ad constituendum medii coeli angulum abutentes, secundum eius ductum reliquos cardines figurabimus.” Compare also to De praedictionibus Astronomicis, trans. Melanchthon, p. 127: “Cum autem longius distant gradus huius dominatoris ab horoscopo, quam a medio coeli, utemur eo numero ad constituendum medium coeli. Hoc constituto, & reliquos cardines mutabimus.” 74 Peletier has the Greek text of Tetrabiblos as edited by Camerarius (1535). See Tetrabiblos, ed./trans. Robbins, p. 234 note 1. 75 Peletier, De constitutione, p. 64: “Ob id etiam in fine dixit τa λοιπa το† κÛντρου καταστησÞµε©α, id est reliquum ipsius cardinis constituemus: non ut Interpretes verterunt, reliquos cardines.” Peletier’s interpretation was influenced by the specific reading of Camerarius’ Greek text, which differs slightly from the modern text (cf. ed. Robbins, p. 234 note 2; ed. Hübner, p. 175). 76 Peletier, De constitutione, p. 65: “Atque adeo apparet ex loco illo libri tertij de

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Peletier concluded that Ptolemy’s astrological midheaven (the cusp of the tenth house) did not coincide with the meridian.77 Instead, it is defined by the intersection of the ecliptic and the great circle going through the ecliptic poles and our zenith.78 Since the single longitude system was the only common method of domification to adopt this interpretation of the midheaven, Peletier was able to claim that this was the true Ptolemaic method. This interpretation was reinforced in two ways. First, Peletier adduced the authority of Centiloquium 37 and Firmicus Maternus.79 Second, he also put the weight of his own biography in the scale. The comparison of his own horoscope, drawn up with the single longitude-method, to the events of his own life provided positive proof that equatorial houses did not work. The conjunction of the luminaries preceding Peletier’s birth announced investigation of abstruse things, intense study, great reflection, and assiduous labour, which was corroborated by Peletier’s publication on Euclid’s Elements, his elucidation of Ptolemy’s writings, explanations of algebra in Latin and French, teachings on medical method, as well as his poetry.80 Indications that were obtained from the equatorial method, however, matched his biography much less. The position of Aries 14° in midheaven with the sun in trine aspect from Leo would have bestowed honours upon Peletier, directed his plans towards them, and would have made him the beneficiary of many opportunities. In reality, Peletier confessed, few men experienced a less prosperous fate than he had. Why else did he relinquish the enviable

Prorogatoribus, Ptolemaeum exclusisse Meridianam partem ab anguli appellatione. Ubi enim de Horoscopo, Meridiano & Occidente dixit, tum subijcit, ‰ν τοÝσ τρισd τοàτοισ Âροισ: id est, In ijs ipsis tribus finibus: non, sicut Interpretes verterunt, In his tribus cardinibus. Ubique enim pro angulis τÀ κÛντρα dicit.” Peletier refers to Tetrabiblos, p. 290 (m134). Remark that the Gogava-translation did not translate Âροσ as cardo. Cf. Operis Quadripartiti, trans. Gogava, fol. k3v: “Cum autem praecedens locus in his tribus limitibus non reperitur.” Melanchthon did. See his De praedictionibus astronomicis, p. 157: “At si locus praecedens in in his tribus cardinibus non extiterit.” 77 See Stadius, Ephemerides (1560), fol. b4r: “Precipue si Medium Coeli in circulo meridiano constituas (quod Ptolomeum, ubi de deductione prorogatorum explicat, fecisse liquido constat, nam prorogatorem in Medio Coeli constitutum per rectas ascensiones deducit in horoscopo per obliquas).” 78 Peletier, De constitutione, p. 64. 79 Peletier, De constitutione, pp. 66–67. Note that Peletier no longer accepts the attribution of Centiloquium to Ptolemy, following Cardano in his commentary on Tetrabiblos. See Grafton, Cardano’s Cosmos, p. 137. 80 Peletier, De constitutione, p. 69.

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task of leading a college, taken up at Paris at the age of 27, in order to travel and see foreign cities and customs? Peletier’s astrological autobiography gradually spiraled towards a rather depressing tale of the correlation between planetary influence and the dark pages of his life and character. If anything, this showed that the sun had to be the ruler of the ninth house, not the tenth, in his geniture, and that single longitude-domification was the only reliable method.81 Peletier presented Stadius with the choice between a genethliacal practice providing quantifiable precision but few authoritative credentials, or one that offered less discernible precision but greater conformity with Ptolemy’s Tetrabiblos. Both options were also divided over the familiar question whether natal astrology should focus on a chronological or a qualitative analysis of birth charts. Like Schöner, Peletier clearly preferred the second option, which enabled him to cite Stadius’ disregard for the Ptolemaic doctrine of rays as an additional argument. This also undercut the theoretical credentials of Regiomontanus’ combination of equatorial houses and position semi-circle prorogation. The brevity of Stadius’ response (1570) indicates the profound impact of Peletier’s analysis: We would either have to reject the teaching of the time of events, which is performed by a prorogation, if we are to make our way in this labyrinth, thus being robbed of the foremost fruit of predictions; or else, deny the significators any prorogatory dignity when they are found outside midheaven. (…) All these things are contrary to the doctrine of Ptolemy, and are refuted by experience and events, on which account I advise the unequal distribution of houses, until someone comes forth who will be able to solve this difficulty.82

81 Peletier, De constitutione, p. 70: “Sed iam pro instituto dico, si fuisset mihi Arietis decimaquarta pars in Coeli Medio, nimirum in decimo loco, ex recentiorum opinione, equidem ad honores capessendos fuissem propensior, atque eo mea consilia direxissem: presertim quum ad eam rem mihi multa adiumenta, multaeque occasiones, hominum iudicio ostenderentur. Sol quippe in Leone, in quo domicilium habet, & ex angulo Orientis, Arietem, in quo habet carpentum, respiciens Trigonicis radijs, me ad honores evexisset, Principum gratiam & amicitiam conciliasset. In quo tamen nemo fortunam expertus est minus prosperam, quam hactenus fecerim.” 82 Stadius, Ephemerides (1570), p. 16: “Aut doctrina de eventuum tempore, quae per directionem fit, nobis abijcienda est, si in istum nos Labyrinthum insinuabimus, & spoliabimur praecipuo praedictionum fructu: aut significatoribus exuenda est omnis prorogatoria dignitas, quando extra centrum Medii Coeli ultro citroque deprehenduntur. (…) quae omnia ut cum Ptolemaei doctria pugnant, ita & ab experientia,

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Stadius was unwilling to give up his enthusiasm for prorogations and a chronological analysis of birth charts. This implied, however, that only empirical success could be adduced in its favor. The problem must have been widely acknowledged: Stadius’ Ephemerides had become the single most important tool of many astrological practitioners by 1570. A thorough knowledge of the astrological tradition still allowed Stadius to dominate traditional interpretive practices: he managed to correct Peletier’s astrological autobiography. The latter emphasized the inconsistency between the trine aspect of sun and midheaven in an equatorial house division on the one hand, and his lack of good fortune on the other. By sixteenth-century standards, this interpretation was not far-fetched.83 But Stadius claimed that these precepts were of Arabic origins, and not genuinely Ptolemaic.84 In his opinion, Peletier had not accurately followed Ptolemy’s instructions in Tetrabiblos iv.3.85 Nevertheless, Stadius’ claim to provide an exact chronology of future events through Ptolemaic prorogation was severely challenged. It is important that the nature of this challenge be carefully characterized. Stadius’ empirical examples of successful explanations still testified to his expertise as a practitioner. However, Peletier ruptured the intimate link between this empirical success and Ptolemaic authority. Stadius’ expertise was no longer guaranteed by ancient, common experience. The following section shows another member of the Louvain familia taking the final step of discrediting particular experience as a reliable indicator of astrological expertise.

& eventibus confutantur, qua re nobis inaequali domorum distributione tantisper utendum esse consulo, dum aliquis nobis exorietur, qui & istam difficultatem tollere poterit.” 83 Chapter i.10 of Schöner’s De iudiciis nativitatum (1545), entitled “On the honor and dignity of the new-born,” explicitly stated that: “[If] the moon [stands] in Taurus at midheaven or in the ascendent, and the sun [is] standing in Leo in the first [house]: by these, he that has them placed in this manner, will achieve great dignity,” and “the sun [being] well-disposed in the ascendent, or midheaven, or ninth house, signifies glory and excellence.” See Schöner, De iudiciis nativitatum, fols. m3v and m4r. 84 Stadius, Ephemerides (1570), p. 16: “Verum quia istam partem urget Peletarius, idque potius ex Arabum placitis quam Ptolemaei.” 85 Stadius, Ephemerides (1570), pp. 16–17.

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chapter eight 3. The collapse of empirical success as a token of expertise

3.1. Sixtus of Hemminga’s Astrologiae refutatae liber (1583) Straining political tensions dominated the Netherlands as Jupiter closed in on Saturn in the beginning of 1583. The Spanish reconquista of the Netherlands had regained sudden vigor under the command of Alessandro Farnese (1545–1592) and was slowly approaching Antwerp. François, Duke of Anjou and newly appointed prince of the revolting provinces, disclosed a bitter hidden agenda when his troops unexpectedly tried to seize the city in January.86 Christopher Plantin wisely negotiated an appointment as academic printer in Leiden while his assistants completed 550 copies of the Astrologiae refutatae liber, written by a senior debutant called Sixtus of Hemminga (1533–1586).87 Its author, one of four prodigal sons from a Frisian patrician family, had studied “mathematics” under Gemma Frisius in the early 1550s.88 As he reached the age of 50, however, Sixtus looked back upon his youthful astrological fancy with great regret.89 The Astrologiae refutatae liber developed this common theme through a critical examination of thirty birth charts. There is ample evidence that Sixtus of Hemminga specifically aimed at gaining high patronage support. At least one copy of the Astrologiae refutatae liber bears a dedication to François, Duke of Anjou (1554–1584).90 François d’Anjou was the youngest son of the French King Henri ii and Catherine de’ Medici. By 1583, each of his brothers –François ii, Charles ix and Henri iii- had occupied the French throne, and it was commonly assumed that François d’Anjou was the next in line after the childless Henri iii. D’Anjou’s international aspirations were considerable. In 1579, he accomplished the improbable by extracting a marriage contract from Elizabeth i, although it was

86

See Parker, The Dutch Revolt, pp. 197–198 and 205–207. Sixtus ab Hemminga, Astrologiae refutatae liber (Antwerp, 1583). See Voet, The Plantin Press (1555–1589), vol. 3, p. 1100. 88 The best biography of Sixtus of Hemminga is Suffridus Petri, De scriptoribus Frisiae, dec. xiii.9, pp. 242–248, who mentions Sixtus’ studies under Gemma at pp. 244–245. This seems confirmed by Sixtus’ claim that he personally drew up Gemma’s horoscope after his death, and transmitted it to his son Cornelius Gemma. See Astrologiae refutatae liber, p. 208. 89 Hemminga, Astrologiae refutatae liber, fol. a4r. 90 This copy is preserved in London, Warburg Institute, call number fah 2430. 87

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never concluded. In 1581, he exploited the troubled situation in the Netherlands to proclaim himself Duke of Brabant and Count of Flanders. Sixtus’ dedicated book confirms this “French connection” in its selection of birth charts that were included for public discussion. François d’Anjou’s father Henri ii, his deceased brothers François ii and Charles ix, his niece, the Spanish Infante Isabella, all figured prominently in Sixtus’ selection of thirty horoscopes. The English aspirations of the Duc d’Anjou are reflected in the birth charts of Henry viii, Edward vi, Mary i Tudor, Elizabeth i, and John Cheke. François d’Anjou’s position in the Spanish provinces was severely compromised, however, when he attempted to overtake Antwerp in January 1583. This may explain why the majority of extant copies of the Astrologiae refutatae liber no longer addressed François d’Anjou. Instead, we find a dedication to Bernard de Merode, stadholder of the northern province of Frisia. Apart from a few personal changes in the last paragraph, Sixtus did not revise the dedicatory letter.91 3.2. Experience, the art, and the artists This dedication was remarkably candid about Hemminga’s claims: The vanity of judgments and predictions is necessarily followed by uselessness, leaving nothing but the bare contemplation of heavens and stars, which is not [restricted] to the astrologer, but common to all mortals.92

Sixtus recalled how his youthful infatuation with astrology was initially accompanied by a reasoned suspicion of fraud. The decisive “antidote,” however, came from the “pharmacy of true experience.”93 This emphasis on particular experience marked an important shift with respect to the criteria of previous astrological critiques, as Hemminga realized particularly well: Giovanni Pico della Mirandola once wrote about foreknowledge against the astrologers in a most learned fashion, while Lucio Bellanti of Siena

91 Based on a comparison with the copy in London, British Library, call number 718.e.10. 92 Hemminga, Astrologiae refutatae liber, fol. a3v: “Iudiciorum autem & praedictionum vanitatem, necessario sequitur inutilitas: ut nihil reliqui sit quam coeli siderumque nuda contemplatio, quae non Astrologo tantum, sed mortalibus communis est omnibus.” 93 Ibid., fol. a3v: “(…) confugi ad antidotum ex verae experientiae officina depromptam, (…).”

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chapter eight answered him. Cornelius Scepper, a man of great learning, also wrote against these astrologers, as did several others on each side. But each of these men fought arguments with arguments, disputations with disputations, words with words, treating this matter in a general way. To my knowledge, however, no one has thus far taken up his pen to refute the particular predictions concerning birth charts, thereby stepping down towards practice and experience.94

This passage refers to an epistemological pattern that was frequently encountered in the previous chapters: particular experience was subservient to common experience, which included astrological precepts, for the legitimation of knowledge claims. The very same concept of relevant experience informed Pico’s Disputations. In this text, Pico applied virtually every imaginable argument against astrology: physical, astronomical, historical, logical, text-critical. One argument, however, is staggeringly absent: empirical testing. Pico briefly mentioned that one winter, he found weather predictions to be correct on 6 or 7 out of 130 days, but never returned to this theme again.95 It seems that Pico, like all of his contemporaries, considered particular experience to be no match for the common experience that astrological precepts provided. Instead, he played out various bodies of common experience (natural-philosophical, astronomical, astrological) against one another. Hemminga’s Astrologiae refutatae liber represents a break with this common epistemological pattern.96 Consider the brief “rational” analysis that introduced the book. Unsurprising for a former member of Gemma Frisius’ familia, Sixtus thoroughly rehearsed Pico’s critique of astrological physics and the uncertainty of its astronomical basis.97 His specific attack on astrologers, however, concerned their

94 Ibid., fol. a6r: “Scripsit olim de praenotionibus contra Astrologos Joannes Picus Mirandula, & quidem doctissime; cui respondit Lucius Bellantius Senensis: scripsit & contra hos, vir multae eruditionis Cornelius Scepperus, pluresque alij, pro & contra. Sed hi omnes argumenta argumentis, disputationes disputationibus, verbaque verbis opponentes, generatim hanc rem pertractarunt: ad particularium vero praedictionum quae de nativitatibus agunt, refutationem, ita ut ad praxim & experientiam descenderit, nemo, quod sciam, hactenus calamum arripuit.” 95 Disputationes, vol. 1, p. 162. 96 One possible predecessor was Thomas Bodier, whose treatise on critical days (1555) included a comparison of 55 charts of patient’s astrological dispositions with the outcome of their diseases. Unlike Hemminga, Bodier adduced this as evidence that further empirical investigation of medical astrology was called for. See Thorndike, History, vol. 5, pp. 301–303. 97 Hemminga, Astrologiae refutatae liber, pp. 3–4 and 10–22.

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failure to contradict this criticism with convincing historical experience.98 Other members of Gemma’s familia had previously adopted such appeals to particular experience as arguments for the validity of astrological practices. One example was Gemma Frisius’ 1555 letter to Stadius. Addressing the problem that Stadius’ use of Copernican astronomy was perceived as a violation of common textual authority, Gemma located trust (and even “truth”) in the precision of astronomical predictions. Another example was Stadius’ laconic appeal to experience in reaction to Peletier’s destruction of the supposed Ptolemaic basis of his prorogations.99 These tactics inspired Hemminga directly. In the first part of his book, he revisited the notorious 1524 conjunctions, which were often said to have caused the German Peasants’ War and the captivity of François i at Pavia.100 “I do not consider this a prediction,” Sixtus wrote, “but rather a silly accommodation of the events to that planetary conjunction.”101 Essentially the same theme was repeated in much greater detail through Hemminga’s analysis of thirty birth charts, which accounted for almost 90 % of the volume of his book. One interesting example is his discussion of the birth chart of Bernard de Merode, dedicatee of the Astrologiae refutatae liber, which Sixtus calculated using Copernican data.102 This examination consisted of two distinct parts. The first dealt with traditional interpretive approaches, focusing on the quality rather than the chronology of predicted events. Using De Merode’s good fortune and manner of death as examples, Hemminga shrewdly demonstrated how a single authoritative text could lead to opposite predictions, depending on the precepts one preferred to use. For this purpose, Hemminga consistently relied on Cyprianus Leovitius’ textbook Brevis et perspicua ratio judicandi genituras ex physicis causis, first published in a single volume with Dee’s Propaedeumata (1558).103 Next, Hemminga applied a particularly meticulous prorogation to De Merode’s birth chart, through which he identified no less than 17 critical moments in his patron’s life.104 Fourteen of these referred 98

Ibid., pp. 4–7. Stadius, Ephemerides (1570), p. 16. 100 See Thorndike, History, vol. 5, pp. 310 and 396; vol. 6, p. 116. 101 Hemminga, Astrologiae refutatae liber, p. 5: “Non hic audio praedictionem ullam, sed plane insulsam eventuum ad synodum illam erraticorum accommodationem (…).” 102 Ibid., pp. 188–195. 103 See Thorndike, History, vol. 6, pp. 111–115. 104 Hemminga again followed Leovitius’ instructions, now in his 1552 edition of 99

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to past times, and were therefore open to verification. Sixtus generously allowed four of them to be chronologically coincident with actual events in de Merode’s life; the other ten, however, had come to nothing.105 Sixtus was less forgiving in most other analyses. Assiduously comparing predicted events with individual biographies, he concluded that natal astrology systematically failed to yield reliable knowledge. Paraphrasing Ptolemy, Hemminga suggested that the problem concerned both the artists and the art.106 Hemminga had come to allot direct epistemological relevance to particular experience, instead of approaching it as a “gnostic” justification of claims to expertise. This lead to results that surpassed even Pico. Hemminga concluded a substantial list of past criticism on astrology with passages from Tetrabiblos,107 adding that: It seems probable that Ptolemy wrote his Tetrabiblos, especially the two last books, not to teach that art publicly, but to show that astrology is truly worthless.108

Ptolemy’s astrological authority had imploded, and particular experience revealed itself as an unreliable guide to assess practitioner’s claims to expertise.109 These fundamental problems were codified in Hemminga’s separation of astrology from the science of motions, “which recent mathematicians prefer to name separately as Astronomy.”110 The symptoms of separation and renaming were clear: the science of the stars was crossing the threshold into a new age.

Regiomontanus’ Tabulae directionum et profectionum (vol. 3, fols. q1r sqq.). See Hemminga, Astrologiae refutatae liber, fol. a5r. 105 Hemminga, Astrologiae refutatae liber, p. 193. 106 Ibid., fol. a6r: “Hanc Leovitij genethliologicam non solum incertam, sed & nullam: Artem item non esse, cuius nulli sunt artifices.” 107 Ibid., p. 22. 108 Ibid., p. 26: “Ut verisimile sit Ptolemaeum libros suos Quadripartiti, sive De praedictionibus Astrologicis, maxime vero duos posteriores conscripsisse, non ut artem illam ex professo doceret, sed ut ostenderet Astrologiam revera nullam esse.” 109 Hemminga had previously classified as unreliable most Arabic authors, as well as Firmicus Maternus, Guido Bonatti, and Joannes Schöner. See Hemminga, Astrologiae refutatae liber, fol. a5r. 110 Hemminga, Astrologiae refutatae liber, p. 1: “Astrologicae vanitatis assertores fatentur quidem doctrinam suam non constare certis demonstrationibus, imperfectam esse, coniecturalem, & incertam illius comparatione quae de motibus corporum caelestium tractat, quam Mathematici recentiores separatim maluerunt Astronomiam appellare, attamen multam contendunt habere certitudinem ex vera saepeque repetita experientia accumulatam atque extructam.”

CONCLUSION

In the summer of 1467, the Hungarian King Mathias i Corvinus hosted a public contest to find the time of conception of the newborn son of Count Johann von Rosgou by astrological means.1 Around the same time, the King sponsored the completion of Regiomontanus’s astrological tables, by which “the times of all future events are chiefly investigated.”2 Regiomontanus’s successors increasingly preferred to distance themselves from astrological practice. In 1600, Tycho Brahe sent the following reply to a request for astrological counseling: I do not freely devote much time to such issues, being more addicted to serious and momentous studies.3

Twenty years later, his former assistant Joannes Kepler introduced a prognostication for 1620 as follows: If I only put forward what the heavens provide, then the calculation of an annual ephemeris would absolve the matter, and I would retain my fame in this annual exercise without being contradicted by anyone.4

What caused this apparent defection among elite astrological practitioners? The question has been addressed in this book through a detailed study of the Louvain astrological community, which was located at the border of the Holy Roman Empire.

1. Antecedents The University of Louvain was erected in 1425, at the end of the first wave of German university foundations. Its medical faculty soon became home to a flourishing community of astrological practitioners. 1

Zinner, Regiomontanus, trans. Brown, p. 94. Regiomontanus, Tabulae directionum (1552), vol. 1, fols. b1v-b2r: “(…) ubi tempora futurorum accidentium omnium per directiones potissimum investigari solent.” 3 Brahe, Opera, vol. 8, p. 305:1–3. 4 Kepler, Gesammelte Werke, vol. xi.2, p. 196: “(…) wann ich allein das jenige einbringen solte, was der Himmel gibt, so wäre mit calculierung einer Ephemeridis 2

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Local astrological instruction was actively supported by the Louvain town council, and proved beneficial to the university’s relations with the Burgundian court. The latter frequently consulted Louvain astrologers in times of political distress. Important changes in this general pattern began to appear in the 1470s. We witnessed the advent of local practitioners like Joannes Laet, who lacked a professional connection with the medical faculty but offered the same kind of astrological knowledge. Laet managed to secure patronage for himself and his son at the court of Liège. At the same time, he introduced a novel element to astrological practice into the Low Countries. Previous astrological consults for the Burgundian court were largely private affairs, which the historian must reconstruct through unique manuscripts and secondary references. Joannes Laet, on the other hand, cultivated his patronage relations in the public domain. His strategies were centered on the careful exploitation of a new astrological genre: the annual prognostication. Annual prognostications originated from a gradual blending of astronomical ephemerides (often called “almanacs”) and astrological judgments. Their makers often included the patrons who sponsored them, in the political subject matter of the prognostication. On the one hand, this merger illustrated the intimate links uniting the respective practices of the “science of motions” and “science of judgments” at medieval universities. On the other hand, it confirmed a broadening interest in academic astrology in late fifteenthcentury society. This interest allowed Laet to model annual prognostications as public tokens of his patron’s power, which he distributed by means of print technology.5 This shows that astrology often cemented valuable relations between the university and political authorities. But it could also alleviate dissent within the university. Louvain logicians and theologians came to blows over the authority to discuss biblical propositions in the period 1465–1475. Louvain astrologers (whose natural allegiances were with the arts faculty) adopted the central terminology of the debate, and vigorously pursued a “conjunctionist” astrology that favored the “concordance of astrology and theology.” The “multi-disciplinarity” of academic astrology would soon begin to conflict with its increasing popularity. This happened first auff ein jedes Jahr, der Sachen uberflüssig geholffen, und behalt ich bey dieser Jährlichen Arbeit den Ruhm ohne jemandes widersprechen.” 5 Compare Long, Openness, Secrecy, and Authorship, p. 247.

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when a delicate balance between competing Italian states began to disintegrate in the 1490s. A steady stream of popular portents, preaching, and prophecies accompanied these political changes. Not surprisingly, implementations of the older “conjunctionist” astrology figured prominently in these popular texts. Although several contemporary treatises attacked this development, none was as critical as Giovanni Pico’s Disputations. Pico’s attack has often been presented as a humanistic defense of individual freedom against the search for universal natural laws.6 However, astrological authorities like Ptolemy disavowed the existence of a “law-like” astrology. Apparently, the astrological debate involved much more than a lofty standoff between alternative world-views. Instead, I have argued that Pico questioned the practice of judicial astrology in a society that was marked by political turmoil, increasing demands for political and religious predictions, and radical changes in communication technology. Pico’s composition of the fiercest attack on astrology ever written was motivated by the social impact of astrological prognostications in his own time. This interpretation also allows us to explain Pico’s explicit wavering between astrological reform and rejection. Likewise, we can understand why his central critical tools (Aristotelian physics, mathematics, and common experience) could be employed either against or in favor of astrology. Finally, it invites us to question Eugenio Garin’s claim that Pico ultimately fell into his own trap when he tried to defend both a superlunary world of necessity and a sublunary world of freedom.7 A close reading of Pico’s natural philosophy suggests that he avoided the trap by resuscitating the theory of sublunary pneuma of Aristotle’s biological works.

2. Problems The Low Countries underwent similar developments at the end of the 1510s. By that time, Louvain had begun to accommodate a new cultural trend called “humanism.” Louvain humanists initially promoted Pico’s work for its didactic qualities. However, some astrological practitioners, questioning the validity of popular predictions surrounding an ominous Saturn-Jupiter conjunction in 1524, soon embraced the Disputations as a repository of arguments. In 6 7

Garin, The Zodiac of Life, pp. 26–27. Ibid., p. 92.

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doing so, they managed to oppose the influence of conjunctionist prognosticators at several courts in France and the Low Countries. These claims were reinforced by the adoption of the humanistscholastic debate as a broader framework for their discontent. This confirms and supplements Erika Rummel’s conclusions, showing how the debate not only hosted local controversies between dialecticians and theologians, but also disputes over astrological expertise. The sudden rise of humanist court astrology left the university in a difficult position. Academic authorities avoided compromising their traditional ties with the local courts, but found it equally difficult to discard its traditional astrological practices (including conjunctionism). The tension spawned a frustratingly ambiguous public response in 1521. This failure of traditional academic strategies of reconciliation contributed to a remorseless debate between urban prognosticators and courtly practitioners. The former ultimately appealed to their personal experience. The latter successfully proposed a restoration of ancient traditions like Ptolemaic astrology, number theory, and Neoplatonic ontology.

3. Solutions The initial practice of “astrological reform” was constricted by a social basis that was largely confined to courtly contexts. Shortly after the 1524 debates, a new generation of Louvain mathematicians began to solve this problem by developing another new branch of Renaissance mathematics: cosmography. The cosmographer’s mathematical descriptions of the world were invested with the brilliance of new discoveries, but shared little of the controversy surrounding astrology. Not surprisingly, courtly patrons, humanist scholars, mathematicians, and wealthy merchants eagerly congregated around this project in the 1530s. In this context, Louvain mathematicians like Gemma Frisius and Gerard Mercator publicly associated their cosmographical projects with the practice of astrological reform. Scholars like Bernard Capp and Patrick Curry have reported a similar connection between astrological reform and its socio-political context for seventeenth-century England.8 However, the Louvain case adds two important elements to this general pattern. First, we 8

Capp, English Almanacs, pp. 182–183; Curry, Prophecy and Power, pp. 57–58 and 78–79.

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found that the practice of astrological reform often legitimized a retraction of political predictions from the public domain. However, this does not imply that court practitioners steered clear of political particulars all together. Instead, one might interpret this process as a return to older, medieval models of court astrology, which favored private interaction between patron and practitioner. In second place, we encountered the dialectical nature of astrological reform. Until the first half of the sixteenth century, urban prognosticators and courtly practitioners shared a common astrological culture, which was often received through the same academic training. As a consequence, courtly attempts to reorganize this culture (astrological reform) were easily imitated by the prognosticators. This created a need for continuing reform in which court practitioners took the lead. The medieval “science of the stars” still provided the preferred framework for this practice of reform. Some initiatives aimed at reforming the “science of motions.” Others favored restorations of the “science of judgments.” Some reformers were drawn to the improvement of practical precepts. Others reconstructed the links between a discipline’s “theory” and “practice.” However, all of these initiatives shared at least one goal: securing our knowledge of future events. This context shaped the early reception of Copernicus’ reform of the science of motions. For instance, it allowed us to discern the astrological subtext of a seemingly detached discussion of practical Copernican astronomy. Astrology’s shrouded presence in the background reflected the new circumstances of elite practice. The political threats of conjunctionist astrology were still tangible, and imposed more rigid boundaries between public and private discourse. A public separation between practical astronomy and judicial astrology began to emerge. Paradoxically, a reverse development characterized the theoretical components of the twin “sciences” of motions and judgments. Louvain mathematicians were extremely interested in Copernican heliocentricity, and publicly defended its relevance to the reform of astrological physics. This conclusion contradicts most accounts of the reception of Copernican cosmology, which commonly depict the 1570s as a time when the traditional subservience of astronomy to natural philosophy began to erode. More important, however, is our suggestion that previous accounts failed to situate Renaissance astronomy in its proper disciplinary matrix and goals. As far as the science of judgments is concerned, reform projects affected both mundane and natal astrology. As with the reception

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of Copernican astronomy, Louvain reformers of mundane astrology seemed to pursue two different (but related) tracks. Cornelius Gemma and Joannes Stadius directed their efforts towards judicial astrology. They implemented their humanist skills to restore and purify various ancient methods of weather prediction and observation. Others, like John Dee, preferred to reconstruct the links between astrological physics and judicial astrology. To this end, Dee and Mercator promoted a mathematical natural history that included quantified weather observations. At least in this instant, we find confirmation of Frances Yates’ claim that “magical” interests promoted the natural-philosophical relevance of mathematical experience. Natal astrology presented a different story. Here, reform projects focused strictly on judicial astrology. More specifically, they pursued the restoration of Ptolemy’s method of “prorogation,” which enabled the precise prediction of life expectancies.9 A successful prorogation provided astrological practitioners with an important means of selfpromotion. Hence, they began to publish detailed explanations of local celebrity deaths. The status of prorogation techniques was also defended through its conceptual links with astrological house division. But since house division constituted a problem in its own right, this connection ultimately discredited the ancient credentials of prorogation. While astrologers could still claim empirical success, their relation to ancient practice had become ambiguous. This situation enabled a former member of the Louvain astrological community to invert such claims against astrology in 1583, thereby discrediting even personal experience as an indicator of the practitioner’s expertise.

4. Results The local results of these changes were obscured by ransacking Spanish garrisons and the plague, both of which struck Louvain in 1578/9. The epidemic claimed the lives of many professors, while students preferred to pursue their studies in less hazardous places. In 1583, the faculties of arts and theology informed the Council of Brabant that most pedagogies were closed, the classrooms empty, and the students gone.10 9 For another attempt to establish genethliacal expertise through the restoration of Ptolemy, see Dooley, Morandi’s Last Prophecy, pp. 112–124. 10 Van der Essen, “Les tribulations de l’Université de Louvain,” p. 73.

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However, other mathematicians trained in the Holy Roman Empire shared the astrological problematic that this book described; their work offers a view on the ultimate outcome of German practices of astrological reform. As an example, I now turn to Tycho Brahe (1546–1601), whose mathematical career was strongly influenced by the work of Gemma’s familia.11 Following a new trend in sixteenth-century aristocratic instruction, Tycho received an academic education.12 Soon after transferring to Leipzig in March 1562, the young Dane discovered his interest in celestial observations, which would become a lifelong passion. Even in this early phase, Tycho’s interests clearly included both celestial motions and judgments.13 Upon settling in Denmark, Tycho kept the habit of producing annual weather predictions, which drew some attention from local medical professors.14 Tycho begun his career as an astrological author in 1573, when he published a treatise on the supernova that appeared in the constellation of Cassiopeia in November 1572. The tract showed clear signs of concern over public respectability, which Tycho met by presenting himself as an unwilling author.15 Also, it showed that the public 11 After his precocious study of Stadius’s Ephemerides, Tycho also acquired and perused the latter’s Tabulae Bergenses. The history of astronomy offered at the beginning of Tycho’s oration on the mathematical disciplines (1574) was clearly dependent on this text. See Brahe, Opera, vol. 1, pp. 148–149. Among Tycho’s prized instruments were a large cross staff and astronomical ring, both constructed by Gemma’s nephew Gualterus Arsenius. See Brahe, Opera, vol. 6, pp. 285–286. Another important influence was Gemma Frisius’s De radio astronomico. Tycho publicized Gemma’s discussion of the optical comet theory in 1573, and adopted his method to inscribe star positions on a celestial globe at Uraniborg. See Brahe, Opera, vol. 1, p. 12; vol. 7, pp. 150 sqq. Tycho owned a copy of Mercator’s Chronologia, from which he could have learned a great deal about the latter’s projects in astrological theory. See Brahe, Opera, vol. 8, p. 281. Tycho’s correspondence also referred to John Dee as one of his close friends. See Brahe, Opera, vol. 6, p. 183; vol. 7, pp. 141 and 284. Last but not least, we find that Cornelius Gemma’s teratological work elicited Tycho’s admiration on several occasions. See Brahe, Opera, vol. 3, p. 67; vol. 4, p. 239; vol. 6, p. 173. 12 See De Ridder-Symoens, “Adel en Universiteiten in de zestiende eeuw”; Maria Rosa Di Simone, “Admission,” in: De Ridder-Symoens (ed.), Universities, pp. 311–324. 13 See Brahe, Opera, vol. 10, pp. 5–11. Although Tycho’s astrological interests have never been systematically studied, good introductions include Shackelford, “Power, Providence, and Cosmic Causality”; Oestmann, “Tycho Brahe’s Attitude to Astrology”; Christianson, “Tycho Brahe’s German Treatise”; Christianson, “Tycho Brahe’s Cosmology.” 14 See Brahe, Opera, vol. 3, p. 93; Gassendi, Opera, vol. 5, p. 394; Brahe; Opera, vol. 1, p. 6. 15 Tycho decided not to publish his astrological weather predictions for 1573, the basis of his original manuscript treatise, because he was concerned with the precision of his results and the public scorn that might ensue. See Brahe, Opera, vol. 1, pp. 6,

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prediction of political particulars had become impossible. When Tycho expanded on the effects of a future lunar eclipse (8 December 1573) on individual rulers, he switched to mythological imagery to discuss the fate of King Frederick ii.16 Danish court practitioners, like their Louvain colleagues, now resorted to social secrecy when they entered the domain of annual prognosticators. Another shared strategy consisted in Tycho’s public calls for astrological reform, which were crowned by his announcement of a treatise called Against the Astrologers, for Astrology.17 At least three local elements spurred these exhortations. At Copenhagen, there was a strong local demand for astrological predictions. As was the case in Louvain, proposals for astrological reform served as boundary markers, through which elite practitioners distinguished themselves from competing “popular” practitioners. In 1574, Tycho also voiced his concern over the implications of Pico’s Disputations.18 Finally, there is clear evidence that Copenhagen’s powerful theologians initially frowned upon Tycho’s astrological activity.19 In Tycho’s earliest astrological work, we find a reformer who pursued the humanist track of restoring and purifying ancient judicial astrology.20 However, Tycho’s ambitions went well beyond this. He also intended to “restore the celestial motions and fabricate tables,” and wished to vindicate “the effects of stars” through careful weather observations.21 This aligns Tycho with Dee’s and Mercator’s attempts

9–10. A few weeks before publication, his friend Pratensis came out strongly against Tycho’s plan to use the word lucubrationes in the title of his treatise, calling this “a dishonored term.” See Brahe, Opera, vol. 7, p. 12. In his prefatory letter, Tycho blamed Pratensis for the decision to publish his manuscript results, and publicly implored his friend to bring out the tract anonymously or pseudonymously. However, Tycho’s private correspondence underlines his active role in the preparation of this publication. See Brahe, Opera, vol. 1, pp. 13–14. In a later version of this story, Tycho also assigned a prominent role in the publication of this tract to the Danish chancellor Peder Oxe. See Brahe, Opera, vol. 3, p. 95. 16 Brahe, Opera, vol. 1, p. 61; Ibid., vol. 1, pp. 132–136. 17 Ibid., vol. 1, pp. 34 and 36. 18 Ibid., vol. 1, p. 168. 19 See Thoren, Lord of Uraniborg, pp. 79–84; Christianson, “Tycho Brahe’s German Treatise,” p. 114. 20 Tycho’s astrological techniques included a strong emphasis on lunar phases, fixed stars, and planetary configurations; a proposal to use eight instead of the usual twelve astrological houses; a different method to determine unequal hours; the transfer of the genethliacal technique of prorogations to the domain of mundane astrology; the derivation of more accurate astronomical data. See Brahe, Opera, vol. 1, pp. 35–42 and 75–130. 21 Brahe, Opera, vol. 1, p. 44.

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to reconnect astrological physics and judicial astrology.22 Unlike his Louvain predecessors, Tycho attracted sufficient attention from the Danish crown to warrant the expenditure of vast sums of money on this project over a period of twenty years (1577–1597).23 In the course of this adventure, Tycho furthered the previous Louvain experiences with reformed judicial astrology. In 1586, his printing press finished an Astrological and Meteorological Diary for that year. The Diary was based on Tycho’s finest work on weather observations and the recovery of ancient weather prediction, and was even introduced as a component of Tycho’s practice of astrological reform.24 However, his friends and peers failed to appreciate this pedigree. Henricus Brucaeus wrote: I am amazed that you, striving after preferable matters, allowed such trite and vulgar things to be published from your printing press. If someone sets out to predict weather changes through these, he exposes his ridicule to the entire world. Those books provide so many erroneous predictions, that they seem filled with jokes and lies. I don’t think there was anyone who predicted the softness and dryness of this [past] winter.25

Another close friend, Thaddaeus Hagecius, warned Tycho that “the common people cannot discern between gold and brass,” and condoned his decision to have the treatise published under the name of one of his pupils.26 The public reception of weather prediction had become difficult to control by the 1580s. Tycho’s correspondents unanimously linked this phenomenon to the popularisation of the genre; for the judgment of the populace had little concern for the astrologer’s appeal to the stochastic nature of his trade. Tycho drew his conclusions. In 1588, he publicly adopted a lukewarm attitude to the practice of weather prediction.27 22 Tycho’s well-known Paracelsian and alchemical interests led him to pursue knowledge of both celestial and terrestrial natures. See Brahe, Opera, vol. 1, p. 43. Compare with Clulee, “Astronomia inferior : Legacies of Johannes Trithemius and John Dee,” pp. 173–174. 23 Tycho’s astronomical observations need no further introduction. On the continuous collecting of weather observations at Hven, see Thoren, Lord of Uraniborg, p. 214. On Tycho’s alchemical investigations, see Thoren, Lord of Uraniborg, p. 211; Hannaway, “Laboratory Design and the Aim of Science,” as well as the indispensable reply by Shackelford, “Tycho Brahe, Laboratory Design, and the Aim of Science”; Segonds, “Tycho Brahe et l’Alchimie”; Figala, “Tycho Brahes Elixier.” 24 See Olaus, Diarium, fol. Bb[1]v. 25 Brahe, Opera, vol. 7, p. 91. 26 Ibid. vol. 7, p. 104. 27 Ibid., vol. 4, p. 113: “Viderint itaque ij qui Diarias Prognosticationes mutationum

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A similar shift can be discerned in Tycho’s practice of natal astrology. Tycho’s early works and correspondence contain frequent allusions to his investigations of birth charts. Astrology aided Tycho to explain the death of his father.28 The German astrologer Hieronymus Wolfius frequently consulted Tycho on genethliacal matters.29 By 1577, Tycho’s reputation reached the Danish court. In July 1577, Tycho offered a reading of the birth chart for the newborn Prince Christian to King Frederick ii. Two years later, a similar document was sent off on the occasion of Prince Ulrich’s birth. Yet another reading, this time for Prince Hans, followed in 1583.30 Tycho’s genethliacal reports were extremely well crafted pieces, continuing the revival of Ptolemaic prorogations that we previously witnessed at Louvain. But even these strategies could not preempt the dangers that followed from Tycho’s high position as a court advisor. In a private report, written after 1588, Tycho recalled persistent rumors around 1584/5 concerning predictions about the King’s imminent death, which caused the latter to summon him.31 The same report suggests that the death of King Frederick ii on 4 April 1588 problematized Tycho’s public expertise even more. Tycho expended considerable effort to show how astrological methods could capture this event.32 At the same time, he felt the need to meet questions surrounding his actual failure to predict the King’s death.33 Natal astrology had Aëris conscribunt, num differentia Longitudinis & Latitudinis tantilla in Orbe Terrae, schemata Syzygiarum Luminarium, & reliquorum Planetarum commixtiones, vnde suas depromunt praedictiones, tantum alterare possit, vt tam diuersam aurae mutationem in Bohemia, & hîc producat, quod vix eos etiamsi lynce oculatiores essent, deprehensuros existimo. Quare cum iudicio moderateque hanc Astrologiae partem tractandam censeo, ne vulgo relinquatur calumniandi occasio.” 28 Ibid., vol. 7, pp. 4, 6, 15–18, 47–48. 29 Ibid., vol. 7, p. 6. 30 For an edition of these three reports, see Brahe, Opera, vol. 1, pp. 181–280. 31 Brahe, Opera, vol. 1, p. 135. The dating of this report is based on Tycho’s reference to the Progymnasmata (written and published between 1588 and 1592) and to the death of Frederick ii on 4 April 1588. See Brahe, Opera, vol. 1, pp. 132 and 134. 32 As his primary explanations for the King’s death, Tycho advanced the Moon’s prorogation to a quartile aspect with Saturn, and the prorogation of the lunar eclipse on 13 March 1588 to opposition with Saturn. Interestingly, Tycho’s text situates the lunar eclipse ten days earlier than it actually happened, thus allowing him to deduce a perfect match with the King’s death on 4 April 1588. See Brahe, Opera, vol. 1, pp. 136–140. 33 Brahe, Opera, vol. 1, pp. 134–135. Tycho’s reply centered on two arguments. On the one hand, he emphasized the personal dangers, involved in predicting evil events to kings and princes. On the other hand, he pointed out frequent counter-indications in natal charts as a reason to consider carefully “to which extent something should

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become a straining practice for Tycho.34 His Progymnasmata (1588– 1592) heavily criticized Leovitius’ practice of natal astrology and referred to the critique of Sixtus ab Hemminga.35 Once again, it was lack of social control (which obliterated the relevance of stochastic claims) that obstructed Tycho’s practice of reformed judicial astrology. Still, some elements of judicial astrology’s disciplinary matrix survived. When Tycho gradually published some of his results in practical astronomy, he encountered few Europeans with the ability and motive to question these results.36 The same can be said about Tycho’s successful exploitation of several celestial novelties. The supernova of 1572 played a crucial role in Tycho’s decision to pursue a program of celestial investigations. His careful analysis of the 1577 comet earned the young Dane a prominent place among European stargazers. Less has been written, however, on the teratological framework within which Tycho approached these phenomena. Strange celestial apparitions had been co-opted by different discourses since antiquity. A good example is the case of comets. Natural philosophers explained comets on the basis of Aristotle’s Meteorology (342b5–345a10). Churchmen situated comets in the economy of divine punishment and salvation by means of certain passages in the Old Testament and patristic commentaries.37 Mathematiciansastrologers approached comets as heralds of dynastic fates, applying elaborate interpretive rules to their mathematical and qualitative properties.38 Young Tycho faced considerable opposition from each of these camps.39 In response, he usually subverted available explanations of celestial “monsters” in favor of a pious but learned ignorance about their ultimate nature and causes.40 This was a crucial move, because

or should not be assigned to these [predictions]” (Brahe, Opera, vol. 1, p. 135). 34 See his comments on a previous prediction for the Wittenberg theologian Caspar Peucer: Brahe, Opera, vol. 7, p. 138. 35 Brahe, Opera, vol. 3, p. 224. 36 One exception was the Italian Giovanni Antonio Magini. See his letter to Tycho (1600) in: Brahe, Opera, vol. 8, pp. 250–254. 37 See Genuth, Comets, Popular Culture, and the Birth of Modern Cosmology, pp. 27–50. 38 Ptolemy, Tetrabiblos, ed./trans. Robbins, pp. 213–219. 39 On theological opposition to Tycho’s teratology, see Christianson, “Tycho’s Treatise on the 1577 Comet,” pp. 114–116; 119–120; 124–127. On Tycho’s strained relationship with both Aristotelian and Paracelsian natural philosophy, see Thoren, Lord of Uraniborg, pp. 56–57, 68; Segonds, “Tycho Brahe et l’alchimie,” pp. 372–375. 40 Brahe, Opera, vol. 1, p. 18.

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it allowed him to sidestep common expectations of precise predictions, which dominated mundane and natal astrology. Ultimately, the phenomenon remained a “great miracle.” But modest ignorance was never Tycho’s final position on celestial prodigies. Paradoxically, it served to introduce his claim to special expertise in decoding their divine messages. First, he presented his mathematical analysis of their exotic properties (superlunary position, rareness, size, motion) as the privileged key to their exotic semiotic value.41 On this basis, Tycho proceeded to negotiate moral trust in his astrological tools and expertise.42 If anything, it seems that Tycho fortified this strategy in his later career. A nice example appeared in part three of the Progymnasmata (1588–1592), where Tycho comments on alternative readings of the 1572 nova: [Cornelius Gemma] then compares this star to the nature of the planets, claiming that it has much affinity with the Sun and Jupiter; but since these are astrological matters, I will not touch upon them. In my third chapter, I have sufficiently indicated which planetary form and light it imitated. If someone wishes to infer that this star must therefore participate in these natures, let him do so.43

Consider Tycho’s use of the epithet “astrological.” While Cornelius Gemma’s speculations regarding the nova’s nature were classified as astrological, Tycho withdrew his own results on the nova’s form, size, and light from astrological interpretations. However, a more complex picture emerges when we turn to the conclusion of the Progymnasmata. There, Tycho used his “mathematical” results to introduce a “physical” consideration of the nova’s matter and manner of generation, which was then expanded into an “astrological” discussion of

41 Ibid., vol. 1, p. 30. Tycho repeated this move a few years later, when he analyzed the 1577 comet for King Frederick ii. See Christianson, “Tycho’s Treatise on the Comet of 1577,” p. 137: “They are in all manner such a great wonder of God and a miracle in the nature of the heavens that they also have greater deeds to accomplish than all other natural courses of the heavens.” 42 Translation taken from Christianson, “Tycho’s Treatise on the Comet of 1577,” p. 137. This strategy is equally fundamental to Tycho’s astrological discussion of the 1572 supernova. See Brahe, Opera, vol. 1, pp. 30–34, which ends with the suggestion that Tycho practices a prudent and secret astrology. 43 Brahe, Opera, vol. 3, p. 69. Tycho refers to Progymnasmata, part 2, chapter 3. See Brahe, Opera, vol. 2, pp. 308–310. For other statements of astrological disavowal in the Progymnasmata, see Brahe, Opera, vol. 2, p. 97; Brahe, Opera, vol. 3, pp. 42, 57, 79, 107, 216.

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the nova’s future effects.44 Interestingly, we find that Tycho’s “physical” study of the nova is largely based on his alchemical knowledge. As early as 1573, Tycho had publicly assigned an essential role to alchemy in the rebuilding of astrological physics.45 This suggests that the Progymnasmata still interacted with the foundations of astrological reform that Tycho had set out in his youth. Even in his later career, Tycho linked his astronomical observations of celestial prodigies with judicial astrology. However, this connection was no longer negotiated through moral trust in his mathematical expertise, but mediated through alchemy and astrological physics.46 Tycho turned away from prognostications, weather predictions, and natal charts by the end of the 1580s. In doing so, he contributed to a trend that we have traced back to the late fifteenth century. At the same time, Tycho remained committed to the practice of astrological reform, the results of which were mainly implemented in his teratological work. This commitment stimulated high expectations related to a better mathematical grasp of the heavens, which were realized with the integration of astronomy and natural philosophy by Kepler, Galileo, and Newton. This book suggests that a thorough grasp of the crisis of Renaissance astrology is necessary to understand the emergence of these hallmarks of the “scientific revolution.” As Eugenio Garin reminded us, this process did not involve a rigorous separation between astronomy and astrology, between reason and superstition, between Athens and Alexandria.47 Instead, the crisis began and unfolded in a mutual adjustment of traditional cultural elements. This adjustment might be viewed as a triangulation. One corner of the triangle was constituted by the increased need for political and religious predictions in Renaissance Europe. This provoked a conflict between the old stochastic claims and novel social impact of astrology. Another angle emerged from Renaissance astrology’s transformation as an object of public patronage. The third point of contact was formed by the astrological practitioner’s need to establish individual expertise. Since this basic pattern did not end with the new philosophy, much

44

Brahe, Opera, vol. 3, pp. 304–310. Ibid., vol. 1, p. 43. 46 Tycho’s former assistant Kepler imitated this tripartite (mathematical astronomy, physics, and astrology) narrative in his famous analysis of the 1607 and 1618 comets. See Simon, Kepler astronome astrologue, pp. 55–57; Caspar, Kepler, trans. Hellman, pp. 302–303. 47 Garin, The Zodiac of Life, pp. xi and 4. 45

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more remains to be done.48 But is this not worth the effort when, paraphrasing Aby Warburg, we seek to rescue Athens and Alexandria?49

48 For instance, Newton exposed comets as permanent objects, moving without impediment in free space around the Sun, between 1681 and 1686. This discovery was part of Newton’s broader project for the restoration of a prisca sapientia in natural philosophy. All this “changed the practice which should deal with comets from popular divination to theologically oriented natural philosophy, giving comets a profound but scarcely less dramatic function and prophetic meaning. They would cause the Deluge, terminate and restore life on Earth and rejuvenate the Sun and the stars” (Schaffer, “Newton’s Comets,” p. 243). 49 Gertrud Bing mentions Warburg’s remark that “Athens needs to be rescued from Alexandria over and over again” in: Warburg, La rinascita del paganesimo antico, p. xxxi.

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INDEX OF PERSONS Abano, Pietro d’, 13, 18 Abelard, Peter, 9–10 Abenragel, Haly, 22, 46, 95–96, 206, 237, 240 Achillini, Alessandro, 48 Adrian vi, 43, 139 Afinius, Henricus, 48, 52 Agrippa, Cornelius, 145 Ailly, Pierre d’, 8, 11, 47–48, 53, 60–61, 92, 95, 99, 159 Alardus of Amsterdam, 119 Alba, Duke of, 222–223 Albategnius, 75 Albert of Hohenzollern, 204 Albertus Magnus, 46, 48, 92, 95 Al-Biruni, 12 Albohali, 22 Albumasar, 14–15, 22, 60–61, 75, 88, 91–92, 95–96, 141, 145, 199 Alcabitius, 18, 22, 46, 95 Alderotti, Taddeo, 13 Aleander, Jerome, 139 Alfonso x, 164 Alfraganus, 180 Algoet, Livinus, 120 Alhazen, 177–178 Al-Kindi, 11, 22, 72, 77, 170, 207, 211 Almansor, 105 Alpetragius, 166 Angelo, Jacopo d’, 114 Angelus, Joannes, 11, 48 Apian, Petrus, 117, 121, 123, 126–127, 186 Aquinas, Thomas, 10, 19, 21, 58–59 Arias Montanus, Benito, 223 Aristotle, 8, 20–21, 23–26, 46, 50–51, 59, 67–71, 88, 96,

165–167, 171, 173, 212–213, 259, 267 Arnaut of Zwolle, Henry, 34 Arsenius, Gualterus, 241, 263 Augustine, 8, 50, 101, 217–220 Avenrodoan, Haly, 22, 76, 93, 174–177 Aventinus, Joannes, 203 Avicenna, 67 Bacherius, Petrus, 223 Bacon, Roger, 61, 72, 99, 171, 173, 177 Baers, Sebastian, 187 Baius, Michael, 224 Barbaro Ermolao, 81 Barlandus, Adrianus, 117, 194 Barlandus, Hubertus, 193–194 Bate, Henricus, 92 Bazelius, Nicolaus, 159–160 Beausard, Petrus, 124, 130, 192 Becker, Jan, 194 Bellanti, Lucio, 13, 17, 24–27, 56, 79, 253–254 Beneventanus, Marcus, 85 Bergagne, Antoine-Marie, 174 Berghen, Adriaan van, 97 Bessarion, Cardinal, 51, 240 Biem, Martin, 203 Biesius, Nicolaus, 195 Block, Joannes, 42 Bodier, Thomas, 254 Bodin, Jean, 223 Boethius, 40, 110–111, 124 Boileau de Buillon, 186 Bollaert, Roeland, 114, 117–118 Bonatti, Guido, 8, 45, 105, 256 Bovelles, Charles de, 110 Brahe, Tycho, 4, 212, 257, 263– 269

306

index of persons

Brederode, Ludovicus, 231 Brucaeus, Henricus, 265 Bylica, Martin, 238 Caesar, Julius, 85 Camerarius, Joachim, 141, 204, 239, 248 Campanus of Novara, 130, 179– 180, 240 Campensis, Joannes, 117, 134 Cardano, Girolamo, 156– 157, 175, 191, 195, 202, 209, 230–233, 242, 246, 249 Carello, Giovanni Battista, 160 Carondelet, Jean, 114, 118 Carvaialus, Aloysius, 231 Celestino, Claudio, 171 Celsus, 194–195 Champier, Symphorien, 111 Charles v, 99, 113, 119, 122, 136, 141, 149, 153–154, 157, 160, 190 Charles v (France), 15 Charles viii, 10–11, 63 Charles ix, 252–253 Charles the Bold, 32, 35–36, 39–40 Charles of Guelre, 154 Chastellain, Georges, 35 Chaucer, Geoffrey, 16, 18 Cheke, John, 253 Christian ii, 98, 102, 118, 141– 142 Cicero, 8, 21, 71, 74, 100, 107, 191, 200 Clement vi, 87 Clement vii, 86 Clichthove, Josse, 98, 102, 110 Colonna, Antonio, 85 Copernicus, Nicolaus, 3, 118, 147–183, 261 Coppin, Nicolas, 94–95 Cornelius van Weldam, 190 Craenevelt, Franciscus, 101, 116 Curtius, Petrus, 116

Dantiscus, Joannes, 118–120, 134–136, 141–142, 147, 149, 166 Dee, John, 135, 168–178, 181, 206–212, 255, 262–264 Despauterius, Joannes, 116 Dionysius Areopagiticus, 110 Dorotheus of Sidon, 75 Dorpius, Martinus, 116 Driedo, Joannes, 117 Driutius, Michael, 116 Dubois, Jean (Joannes Sylvius), 191 Echelpoel, Walter, 191 Edward vi, 232–234, 246, 253 Elizabeth i, 170, 252–253 Ephorinus, Anselm, 126 Erard de la Marck, 103 Erasmus, 48, 81, 101, 116, 119– 120, 126, 194 Ericsen, Godschalck, 98, 101 Essler, Joannes, 90 Estienne, Henri, 85 Euclid, 40, 121, 168, 212, 249 Eudoxus, 201 Farnese, Alessandro, 252 Ferdinand i of Habsburg, 141 Fernandez de Cordoba, Pedro, 153–154 Fernel, Jean, 216 Fevyn, Joannes, 101, 116 Ficino, 56, 64, 67, 71, 107, 218, 225 Filelfo, Francesco, 81 Finé, Oronce, 236, 239 Firmicus Maternus, 11, 22, 105, 130, 145, 242, 249, 256 Florimonte, Galeazzo, 85, 89 Fracastoro, Girolamo, 166 Franciscus Monachus, 113–115, 118, 121, 229 François i, 85, 113, 137, 139, 255 François ii, 252–253 François d’Anjou, 252–253 Frederick ii, 264, 266, 268

index of persons Frederick iii, Emperor, 62 Froben, Joannes, 126 Gaditano, Ramiro, 133, 154 Galen, 14, 44, 193–194, 216 ps.-Galen, 44–45 Gaphar, 106 Gattinara, Mercurio, 119, 134 Gaurico, Luca, 83, 140 Gazul, Gin, 236–237, 238–241 Gemma Frisius, 115–118, 121– 122, 124, 127–130, 134–136, 147–183, 186, 191, 196, 198, 227, 229, 241–245, 252, 254–255, 260, 263 Gemma, Cornelius, 159, 180, 186–191, 195–196, 212–226, 231, 252, 262–263, 268 Geoffroy de Méaux, 45 George of Trebizond, 122 Gerard of Cremona, 180 Gerson, Jean, 11 Giuntini, Francesco, 162 Glareanus, Henricus, 124 Goclenius, Conrad, 116–119 Gogava, Antonius, 135, 161, 168, 175, 177–178, 181, 248–249 Gompel, Godefridus, 42 Gonzaga, Vespasiano da, 161 Goorle, Petrus de, 159–160 Grave, Bartholomeus de, 119 Gregory of Nazianze, 110 Grosseteste, Robert, 170–171, 177 Guarimberto, Matteo, 239–240 Guido d’Urbino, 64 Hagecius, Thaddaeus, 265 Haller, Wolfgang, 121 Haschaert, Pieter, 174 Heems, Joannes, 116 Helmont, Henricus de, 41 Hemminga, Sixtus ab, 113, 135, 137, 229, 252–256, 267 Henri ii, 252–253 Henri iii, 252 Henry viii, 99, 139, 253 Henry of Langenstein, 72

307

Hermes, 88, 145 Hesiod, 78 Hessels, Joannes, 224 Heyden, Gaspar van der, 118, 120, 168 Hipparchus, 74, 240 Hippocrates, 44, 193, 195, 209 ps.-Hippocrates, 44–45 Hoefmans, Gerardus, 41 Holbein, Hans, 118 Hooft, Pieter Cornelisz.; 223 Howard, Henry, 174 Hugh of St Victor, 9 Hulst, Frans van der, 103 Hyginus, 101 Iamblichus, 107 Ibn Ezra, Abraham, 46, 75–76, 88, 92, 95, 105, 246–247 Isidore of Seville, 9, 11 Jan iv of Brabant, 29 Jean ii of Bourbon, 10 Jean de Hornes, 37–40, 91 Joannes Damascenus, 110 Joannes de Brugis, 47 Joannes de Los, 39 Joannes de Marliano, 13 Joannes de Muris, 40 John of Seville, 75, 95 Joubert, Laurent, 200–201 Justinus of Nassau, 234 Kepler, Joannes, 4, 182, 257, 269 Keyser, Martinus de, 114 Kratzer, Nicolaus, 98 Laet, Gaspar, 37, 82, 91–95, 114, 137–140, 143–144 Laet, Gaspar jr., 144–146, 158 Laet, Joannes, 36–40, 49, 52–53, 82, 91–94, 114, 140, 143, 258 Laet, Ptolemeus, 144 Lamoral, Egmont, 223 Laurinus, Marcus, 116, 120 Lefèvre d’Etaples, Jacques, 81, 98, 110–111, 142

308

index of persons

Lemnius, Levinus, 187, 190–191, 195 Lens, Arnold de, 125 Leo x, 139 Leoniceno, Niccolo, 202 Leopold of Austria, 45–46, 48 Leovitius, Cyprianus, 242, 255, 267 Lewis, Matthias de, 41–42 Lichtenberger, Johannes, 62–64 Louis xi, 35, 40 Louis de Bourbon, 37–40, 49 Louise de Savoie, 86

Molanus, Joannes, 39, 125, 191, 214–215, 223 Montis, Thomas, 45, 52, 94–97, 105 Montulmo, Antonius de, 48 More, Thomas, 98 Moulin de Rochefort, François du, 85

Magini, Giovanni Antonio, 32, 267 Magninus Mediolanensis, 44–45 Mainardi, Giovanni, 55, 194 Manfredis, Hieronymus de, 39 Margaret of Austria, 113–114 Margaret of Parma, 223 Marstaller, Gervais, 17 Martens, Dirk, 47, 81, 100 Martin v, 29 Mary of Burgundy, 40 Mary i Tudor, 241, 253 Mathias i Corvinus, 235, 238, 257 Maximilian of Austria, 40, 139 Maximilian of Egmond, 161 Maynus de Maineriis, 45 Medici, Catherine de’, 252 Medici, Lorenzo de’, 63, 78 Medici, Piero de’, 63 Mela, Pomponius, 101, 125–126 Melanchthon, Philipp, 141, 166, 186, 248–249 Mercator, Bartholomeus, 178 Mercator, Gerard, 121, 130– 133, 135, 154–155, 168– 169, 178, 181–182, 208, 210–212, 223, 225, 260, 262–264 Mercurio da Corregio, Giovanni, 62 Merle, William, 203 Merode, Bernard de, 253, 255 Messahala, 22, 75, 88, 92, 95 Milichius, Jacob, 186

Offusius, Jofrancus, 170 Olah, Nicolaus, 120 Omar Tiberiadis, 22, 230 Oresme, Nicole, 20, 72–73, 171 Ortelius, Abraham, 223 Oxe, Peder, 264

Neesen, Willem, 125 Neve, Joannes de, 116 Newton, Isaac, 270 Nifo, Agostino, 87, 89, 94, 99, 105

Pafraet, Richard, 81 Pantinus, Willem, 194–195 Paul iii, 162 Paul of Middelburg, 48, 61–65, 79, 92 Peletier, Jacques, 240, 246–251, 255 Petri, Suffridus, 115, 121, 136, 252 Peucer, Caspar, 165–166, 226, 267 Peurbach, Georg, 160, 180, 204, 235 Pflaum, Jakob, 82–83 Phares, Simon de, 10–11, 33, 47, 53, 138 Philip the Good, 31, 34–36 Philip ii, 123, 162, 229, 241 Pico della Mirandola, Gianfrancesco, 55 Pico della Mirandola, Giovanni, 2, 20, 24, 55–80, 81, 88–89, 99, 104, 132, 140, 146, 149, 168, 171–175, 179–181, 194, 211, 222, 232, 238, 244–245, 253–254, 256, 259, 264 Piemontese, Alessandro, 186–187

index of persons Pietramellara, Andrea, 137, 206 Pigghe, Albert, 83, 85–91, 95, 99– 100, 106, 114, 117, 137–141, 143–144, 146, 187, 199 Pirez, Diego, 127 Pius ii, 36 Pius v, 224 Plantin, Christophe, 132–133, 252 Plato, 7, 55, 108 Plato Tiburtinus, 93 Pliny the Elder, 193, 201–202 Pliny the Younger, 100 Poliziano, Angelo, 56, 79, 81 Pontano, Giovanni, 243 Porphyry, 55, 74, 107 Praet, Charles van, 102 Praetorius, Joannes, 165 Pratensis, Joannes, 264 Proclus, 55 Ptolemy, 3, 12–15, 18, 19, 59, 70–71, 74–75, 77, 85, 88–91, 96, 106, 114, 126, 130, 133, 144–145, 155, 160–161, 167, 171, 175–177, 179, 185, 187–189, 191, 199, 204–205, 221, 227–251, 255, 259–260, 262, 266 ps.-Ptolemy, 14, 35, 46, 59, 77, 92–93, 107, 204, 219, 228, 231, 242, 249 Pynnock, Louis, 40 Pynson, Richard, 91 Pythagoras, 107–109 Rabanus Maurus, 9 Rançonnet, Aimar, 246 Ravestein, Judocus, 224 Raymond of Marseille, 10, 93 Regiomontanus, Joannes, 106, 129–130, 145, 148, 177, 204, 230, 235–247, 256–257 Reinhold, Erasmus, 160, 164, 166, 180, 192 René de Châlon, 113, 229–231, 247 Rescius, Rutger, 116–117 Resendius, Andreas, 120

309

Rheticus, Joachim, 136, 147, 149, 156, 166 Ringelberg, Joachim Sterck, 127 Rivo, Petrus de, 40, 48–53 Robert de Bergues, 192 Robert "Perscrutator" of York, 95 Rockocx, Nicolas, 160 Rojas, Juan de, 121–122, 135 Rollin, Nicolas, 35 Roussel, Gerard, 98, 110–111, 142 Ruffaut, Jerome, 123 Rupert of Deutz, 9 Sacrobosco, Joannes de, 40, 123–124 Savonarola, Girolamo, 78–80 Scepper, Cornelius Duplicius de, 84, 97–111, 118–120, 132–133, 134, 136, 141–143, 147, 149, 180, 196, 254 Schevez, William, 37 Schöner, Joannes, 118, 132, 204–205, 228, 242–244, 251, 256 Schreckenfuchs, Erasmus, 160, 202 Schuute [Scut], Cornelis, 158–159 Schylander, Cornelis, 187 Sforza, Francesco, 46 Snouckaert, Maarten, 122 Spierinck, Joannes, 30–31, 34, 37, 43, 45 Stadius, Hieronymus, 162 Stadius, Joannes, 113, 125, 135, 137, 151, 157–160, 162–168, 191–203, 229–231, 233–234, 245–251, 255, 262–263 Stadius, Petrus, 200–201 Steenwijck, Berthold, 42 Stöffler, Johann, 82–83, 151–153, 194 Strabo, 126 Sucquet, Joannes, 43 Tapper, Ruard, 224 Tasso, Torquato, 63 Thenaud, Jean, 86–87

310

index of persons

Thibault, Jean, 101, 144–145 Thomas “Philologus” of Ravenna, 105 Thou, Jacques-Auguste de, 223 Thriverus, Hieremias Brachelius, 136, 194–196 Tricasso da Cerasari, Patricio, 243 Valerius, Cornelius, 124, 154 Valla, Giorgio, 155 Varro, 193 Vekenstyl, Henry Baers, 120–121 Velsius, Justus, 122 Vettere, Ludovicus de, 34, 43 Vesalius, Andreas, 30, 135 Vesalius, Joannes, 30–36, 41, 43, 45, 96 Vesalius, Paulus, 30

Virdung, Joannes, 94, 105 Virgil, 78, 100, 193 Vives, Juan Luis, 81, 100–101, 103, 116, 125–126, 194 Vossenholen, Adrianus van, 159 Waen, Joannes, 123 Walther, Bernard, 152, 204 Werner, Joannes, 186, 231 Westfalen, Jan van, 36–40, 48 William of England, 45 William of Orange, 213, 223, 229, 234 Withagen, Joannes, 186 Wolfius, Hieronymus, 266 Zael, 22 Zomeren, Henricus van, 50–53

INDEX OF PLACES Amboise, 85 Antwerp, 48, 82, 91, 94, 97–98, 100, 103, 113, 127, 132–133, 144–146, 158–160, 163, 191–192, 223, 252–253 Arras, 35 Artois, 35 Augsburg, 119–120

Fossombrone, 63 Frisia, 115, 134, 253

Basel, 101 Bologna, 2, 8, 14–15, 32, 46, 48, 61, 96, 137, 206 Bruges, 120, 158, 194 Brussels, 30, 32, 35, 46, 119, 136, 149, 163, 192 Burgos, 119 Byzantium, 156

Istanbul, 141 Italy, 24–27, 32, 46, 55–80, 83, 119, 140, 190, 194

Cambridge, 2, 168 Canary Islands, 98 Cassel, 98 Cleves, Duchy of, 30 Cologne, 30, 51, 97, 157, 192 Constantinople, 35 Copenhagen, 4, 264 Cracow, 15, 92, 151, 157, 203 Deventer, 81 Dokkum, 115 Douai, 29 Düren, 154 Duisburg, 169, 178, 216 Dutch Republic, 29 Egypt, 172 Erfurt, 92 Feria, 153 Ferrara, 14 Florence, 55–56, 63, 69

Ghent, 213, 234 Grave, 161 Groningen, 115 Hoogstraten, 191

Kampen, 85 Leiden, 29, 252 Leipzig, 90, 92, 263 Loenhout, 191 Lyon, 10 Maastricht, 46 Madrid, 118, 161 Mantua, 161 Mechlin, 113–114, 186 Melun, 171 Mesopotamia, 22 Milan, 35, 46 Modena, 62 Montpellier, 144, 194 Munich, 203 Namur, 194 Naples, 63 Nieuwpoort, 97 Nijmegen, 223 Nuremberg, 203, 204, 232, 239 Oxford, 2, 15–16, 203 Padua, 2, 14–15, 46, 48, 161, 219

312

index of places

Paris, 2, 10–11, 13, 15, 33, 81, 85, 98, 110, 138, 168, 194, 250 Parma, 239 Pavia, 13, 30, 113, 137, 255 Perugia, 61 Picardie, 35 Poland, 118–120, 134

Tournai, 33 Tübingen, 194 Turin, 191

Rhineland, 62 Rome, 62, 139, 156–157

Venice, 36, 61, 161 Venlo, 154 Vienna, 15–16, 33, 235

Salamanca, 2, 15, 133 Seville, 9 Siena, 13, 24–27 Somme, 35 Spain, 118–119 Tourinnes-la-Grosse, 191

Urbino, 61 Utopia, 98 Utrecht, 153

Wittenberg, 165 Worms, 84, 103 Yucatan, 98 Zierikzee, 190

INDEX OF SUBJECTS Alchemy, 265, 269 Almanacs, 29, 30–32, 187, 258 (see also Astronomy, ephemerides and Prognostications) Aspects, 11, 18, 32, 139, 145–146, 188, 247–248, 200, 205, 207, 239, 244, 247, 266 Astrology antiquity, 73–74, 88, 192 astrological physics, 18–21, 57–58, 65–73, 75–76, 89, 95–97, 131, 143, 145, 168, 171–174, 175–180, 185, 189–190, 201–203, 205–206, 211–212, 261, 265, 269 (see also Natural philosophy) – and astronomy, 7–8, 12– 13, 16–17 (see also Astronomy) chorography, 46, 78, 189 chronocrators, 230 consulting, 33–36, 38–40, 43, 142–143, 156, 257 contradictions, 74–77 – and cosmography, 129–133, 260 criticism, 55–80, 232, 245, 253–256, 259 decans, 106 definition, 12–17 exaltations, 18 faces, 18, 106 horary astrology, 13 houses, 11–12, 18, 121, 129–130, 236–251, 264 lunar mansions, 106 medical, 13, 31–32, 43– 46, 78, 120, 145, 187, 193–196

melothesia, 44 mundane, 13, 19, 30–33, 36–40, 60–65, 81–111, 143–146, 156–160, 185–226, 262 natal, 13, 19, 34, 37–38, 75, 86, 113, 139–142, 227–256, 262, 266–267 (see also Christ, horoscope of ) – and optics, see Optical model position semi-circles, 235–236 profections, 228, 230 propaganda, 34–40, 84, 103, 139, 213–214, 222–223, 226, 259 prorogation, 75, 129–130, 142, 227–241, 243–246, 252–256, 262, 264, 266 public/private, 142–143, 148–149, 154–160, 234, 261, 263–264 revolutions, 37, 129, 228 as science, 25–26 subdivisions, 19 tacuinus, 32 – and teratology, 220–222 terms, 18 theoretical/practical, 13–14, 16–17, 26–27, 90, 132, 142–143, 185–186, 189–190, 208–212, 261 transits, 231 triplicities, 33, 47–48, 104, 159, 205 Astronomy, 144–146, 188, 192, 264 Alfonsine, 90, 147–148, 150–153, 155, 164, 166, 180

314

index of subjects celestial motion, 4, 66 Copernican, 147–183, 261 – and cosmography, 127–128, 150 eccentricity, 192 eclipses, 48, 83, 88, 92, 152, 158–160, 185, 189, 221–222, 264, 266 ephemerides, 31, 82, 106, 145, 160, 186–190, 206, 208, 221, 257, 258 (see also Almanacs and Prognostications) fixed stars, 147–148, 154– 158, 176, 180, 188, 192, 201–203 homocentric, 166 models, 90, 149, 164–168, 179–183 planetary distances, 71–73, 164–168, 175–176, 179–183 planetary positions, 147–148, 150–151 planetary sizes, 71–73, 147–148, 158, 16, 175–176 precession, 128, 147–148, 156–157, 166, 177, 202 realism/instrumentalism, 181–183

Botany, 198 Calendar reform, 48, 147–148, 192 Censorship, 39, 143, 187, 223 Change, sublunary, 19–21, 66–71, 172 Christ, horoscope of, 47–48, 60–61, 99, 159 Comets, 32–33, 35, 45–47, 212–213, 267–268, 270 Competition, among practitioners, 138, 143–146, 158–160, 199–201, 214–215, 222, 247, 264

Conjunctions, planetary, 32–33, 35, 47, 60–63, 81–111, 138– 139, 144, 148, 152–153, 220, 258–259 Cosmography, 113–136, 150, 163, 169 Courts Burgundy, 30–40, 258 Danish, 97–111, 118–119, 263–269 English, 33, 91, 98, 232–234, 241 French, 10, 33, 85–91, 138–141, 252 Habsburg, 33, 101–102, 113– 115, 118–121, 136–137, 149, 153–154, 157–158, 162–163, 229–231, 241 Hungary, 238–239, 257 Liège, 36–40, 91, 103, 192, 198, 258 Demons, 79, 107–109 Demonstration, 14–15, 26, 51–53, 165 (see also Epistemology) Didactic poems, 78–193 Disputation, 48–50, 58–59, 94–97 Dreams, 98–100, 221 Earth, motion of, 165–168, 179–183 Epistemology, 13, 25–27, 50–53 (see also Demonstration) Experience, universal/particular, 13, 25–26, 90–91, 198, 205– 206, 210–211, 231–232, 249–251, 253–256 Expertise, 38–39, 92–94, 197–201, 229–234, 245–256 Explanatory autonomy, 20–21 Flood, Biblical, 48, 53, 61, 74, 81–111, 137 Four empires, 156–157 Free will, 9–12, 56 Future contingents, 49–53

index of subjects Generation, 20–21, 23, 68–70, 171–172 Golden Fleece, order of, 36, 153–154 Heat, celestial, 66–73, 171–172, 207–208, 216 Horoscope collections, 230–232 Humanism, 77, 81–111, 119–121, 125–127, 248–249, 259–260, 264 Collegium Trilingue, 116–117, 119–121, 127 Lily, pedagogy of the, 115– 116 – and scholasticism, 82, 87, 99–100, 260 Influence, 4 Instruments, 74, 240 armillary sphere, 119–120 astrolabe, 14, 121, 155, 240–241 astrological, 120, 129–133 astronomical ring, 263 clocks, 34 cross staff, 150, 154–155, 263 globes, 114, 119–120, 127– 133, 155, 239–240, 263 Letter writing, 81, 161–163, 169 Light, celestial, 4, 66, 69, 71–73, 89, 170–172, 177–178, 192, 211 Lots, doctrine of, 144, 199–201 Mathematics mixed, 26, 198, 211 and natural philosophy, 203– 212, 182–183, 207–212, 268–269 Medicine, 13–14, 30–37, 67, 90, 134–136, 144, 163, 186, 193, 207, 218, 257, 263 (see also Astrology, medical)

315

Natural philosophy, 14, 19–22, 45–46, 66–71, 131, 143, 162, 164–165, 169, 171–172, 179, 181–183, 186, 200–201, 259 Neoplatonism, 67–69, 105, 107–110, 215–220, 225 New star (1572), 212–215, 263–264, 267 Number theory, 108–110, 142– 143 Optical model, 71–73, 170–171, 175–181, 209–210 Parapegmata, 192–193 (see also Astronomy, fixed stars) Patronage, 169, 185 (see also Courts) Planetary virtues, 18, 23, 175–176 Preternatural, 218–221 Printing, 36–40, 140, 142–143, 145, 258 Prognostications, annual, 32, 36– 40, 62–65, 81–97, 137–141, 143–146, 185, 187–190, 195, 258 (see also Almanacs and Astronomy, ephemerides) Prophecy, 50–52, 62–65, 93, 141, 259 Qualities celestial, 19 manifest, 18, 20–21, 171–173, 188, 207 occult, 24, 170, 173, 216 Secrecy, 139–143 epistemic, 21–22, 24, 56, 66, 91 epistemological, 22–24 – and openness, 38–39 social, 36–40, 185, 264, 268 Soul and spiritus, 67–71, 171–172, 215–217, 219 Species, propagation of, 170 Supernatural, 60, 104, 214, 218 Surveying, 127

316

index of subjects

Teaching astrology, 12–16, 40–46, 133–134 astronomy, 14, 121, 124 cosmography, 121, 123–125, 150, 163 dialectic, 122 familia, 135, 149, 161–163, 174 mathematics, 40–43, 121– 125, 192 private, 16, 121–122, 125, 163 Teratology, 220–226, 267–268 (see also New star (1572) and Comets)

Theology, 9–12, 16, 46–53, 60– 61, 74, 95, 109–111, 187, 214–220, 223–225, 258, 264 Weather observations, 196–198, 201–202, 203–208, 220, 231, 264–265 Weather predictions, 77–78, 105–106, 185–191, 198–201, 221, 263, 265 Zodiacal signs, 9, 12, 18, 44, 72, 75–77, 104–106, 110, 191, 201–202, 205, 243– 244

MEDIEVAL AND EARLY MODERN SCIENCE Editors JOHANNES M.M.H. THIJSSEN CHRISTOPH LÜTHY

Medieval and Early Modern Science is the first book series to be dedicated totally to the investigation of scientific thought between 1200 and 1700, the period that saw the birth of modern scientific method and the origins of the scientific world view. It covers not only the Aristotelian paradigm of scholastic natural philosophy, but also rivalling Renaissance and seventeenth-century conceptions of physics. A broad-based and distinguished panel of editors and international advisors have made a careful selection of the best new research emerging in a vibrant field examining this formative period of European scientific thought. Medieval and Early Modern Science contains contributions from an international cast of experienced scholars and looks for highest standards of scholarship in work that is thought-provoking, insightful, and at the forefront of contemporary discussion. It includes commented editions of crucial texts, monographs of important thinkers, and diachronic analyses of particular themes. Accessible, attractively written articles and monographs will open up the latest trends and developments in the field to a wide range of teachers and students in further and higher education.

1. Lüthy, C, J.E. Murdoch & W.R. Newman (eds.). Late Medieval and Early Modern Corpuscular Matter Theories. 2001. ISBN 90 04 11516 1 2. Thijssen, J.M.M.H. & J. Zupko. The Metaphysics and Natural Philosophy of John Buridan. 2001. ISBN 90 04 11514 5 3. Leijenhorst, C. The Mechanisation of Aristotelianism. The late Aristotelian Setting of Thomas Hobbes’ Natural Philosophy. 2002. ISBN 90 04 11729 6 4. Broecke, S. Vanden. The Limits of Influence. Pico, Louvain, and the Crisis of Renaissance Astrology. 2003. ISBN 90 04 13169 8