Intelligibility of Nature: A William A. Wallace Reader 0813235944, 9780813235943

Citation preview

Intelligibility of Nature

Intelligibility of Nature A William A. Wallace Reader

Edited by

John P. Hittinger Michael W. Tkacz Daniel C. Wagner

The Catholic University of America Press  Washington, D.C.

Copyright © 2023 The Catholic University of America Press All rights reserved The paper used in this publication meets the minimum requirements of American National Standards for Information Science—Permanence of Paper for Printed Library Materials, ANSI Z 39.48-1984. Cataloging-in-Publication Data available from the Library of Congress Paperback ISBN: 9780813235943 | eBook ISBN 9780813235950

In Memoriam Gulielmi Augustini Wallace Ordinis Praedicatorum Doctori Eruditissimi Philosophiae Naturalis

Table of Contents

Contents

Table of Contents

ix

Preface

xiii

Acknowledgments

1

Introduction

Part I. The Intelligibility of Nature

1. The Intelligibility of Nature: A Neo-Aristotelian



2. A Place for Form in Science: The Modeling

11

View

37

of Nature

Part II. The Scientific Relevance of the Thomistic Tradition

3. St. Thomas Aquinas, Galileo, and Einstein

57



4. Thomism and the Quantum Enigma

79

Part III. From Aristotle to Galileo

5. Medieval and Renaissance Sources of Modern

Science: A Revision of Duhem’s Continuity

95

Thesis Based on Galileo’s Early Notebooks

6. Aquinas, Galileo, and Aristotle



7. The Certitude of Science in Late Medieval and

120 130

Renaissance Thought

Part IV. Nature and Her Creator

8. Newtonian Antinomies against the Prima Via

147



9. Metaphysics and the Existence of God

189

 

vii

viii Contents 10. The Cosmological Argument: A Reappraisal

193

11. Review of Anthony Kenny’s The Five Ways

213

12. The First Way: A Rejoinder

218

13. Immateriality and Its Surrogates in Modern Science

226

Part V. Concluding Thoughts 14. The Case for Developmental Thomism

243

Lifetime Bibliography of William A. Wallace, O.P.

263

Index

275

Preface Preface

Preface

The intelligibility of nature was a persistent theme of William A. Wallace, O.P., one of the most prolific Catholic scholars of the late twentieth century. The purpose of this volume is to make available a representative selection of his work in the history of science, natural philosophy, and theology illustrating his defense and development of this central theme. Wallace is among the most important Galileo scholars of the past fifty years and a key figure in the recent revival of scientific realism. Further, his long and productive scholarly career has been shaped by a continuous effort to bring the resources of the Aristotelian-Thomistic tradition to the solution of contemporary problems of philosophy and science. Through all of these contributions, Wallace has provided the foundation for a renewed confidence in the capacity of human knowers to attain understanding of the natural order. Consequently, the overall aim of this book is to provide contemporary readers with a distillation of Wallace’s intellectual achievements and to secure continued access to his scholarship for readers in the new millennium. This is hardly a simple task, if only because of Wallace’s vast scholarly output and the broad range of subjects he addressed. He was the author of some twenty books and more than three hundred articles. Much of this work constitutes his groundbreaking research on the early work of Galileo and its link with the Aristotelian tradition. Wallace also directed his attention to the recovery of medieval natural philosophy itself, contributing substantially to research on the medieval origins of experimental science. Yet, these contributions to the

ix

x Preface

history of science represent only a portion of Wallace’s intellectual production. He also did much to disclose the causal realism underlying modern scientific research. He used his studies in the history of science as a foundation for his own development of an account of scientific modeling, creating a new synthesis of traditional natural philosophy with a viable contemporary philosophy of science. In addition, Wallace addressed theologically-related issues such as the cogency of the cosmological argument and the problem of faith and reason. Any attempt to represent such a large and wide-ranging scholarly achievement in a limited selection of essays is bound to be inadequate. Nonetheless, some sense of the nature of Wallace’s contributions can be provided by a selection that is focused on certain issues related to his concern with the intelligibility of nature. This book contains fourteen previously published essays written by Wallace over a period of some forty years. Many of these essays are currently not readily accessible. They are arranged in five thematic groups, each representing a major subject area of Wallace’s scholarly interests. The first group is comprised of essays on making nature intelligible through the use of scientific models. The second group of essays investigates various ways in which the Aristotelian-Thomistic tradition is foundational to contemporary scientific research. Essays in the third group are historical studies on the origins of modern science. The fourth group of essays discuss the viability of the cosmological argument for the existence of God in light of natural science. In closing, an additional essay is included concerning the continued relevance of Thomism for the future of scientific research efforts to make nature intelligible. Together, these essays provide a representative sample of Wallace’s multifaceted contributions to scholarship. Following the selected essays, a lifetime bibliography of Fr. Wallace’s works is included for readers who wish to learn more about any aspect of his exemplary scholarly career. The bibliography is arranged chronologically, but entries are also categorized in a way to indicate

Preface 

xi

the various fields of study to which Wallace contributed. This bibliography is based on the list of Wallace’s publications that was appended to a book-length collection of philosophical and historical papers, Nature and Scientific Method, edited by Daniel O. Dahlstrom in 1991. The bibliography in the present volume has been updated to include work published by Wallace during the final phase of his career.

Acknowledgments

The editors are grateful to their graduate assistant Francisco Plaza and to John Martino of The Catholic University of America Press for their assistance in preparing this collection for publication. The editors also wish to thank the editors of various journals for permission to publish Fr. Wallace’s essays that first appeared in the following publications: 1 History of Philosophy Quarterly for “The Certitude of Science in Late Medieval and Renaissance Thought,” 1986. New Scholasticism for “Metaphysics and the Existence of God,” 1962. Proceedings of the American Catholic Philosophical Association for “A Place for Form in Science,” 1995; “Aquinas, Galileo and Aristotle,” 1983; “The Cosmological Argument: A Reappraisal,”1972; “Immateriality and Its Surrogates in Modern Science,” 1978; and “The Case for Developmental Thomism,” 1970. Proceedings of the Patristic, Medieval & Renaissance Conference for “Medieval and Renaissance Sources of Modern Science,” 1979. Review of Metaphysics for “The Intelligibility of Nature: A Neo-Aristotelian View,” 1984. The Thomist for “St. Thomas Aquinas, Galileo and Einstein,” 1964; “Thomism and the Quantum Enigma,” 1997; “Newtonian Antinomies against the Prima Via,” 1956; “Anthony Kenny’s The Five Ways,” and “The First Way: A Rejoinder,” 1975.

1. Full citation information is available in the bibliography of Wallace’s works at the end of this book.

xiii

Intelligibility of Nature

Introduction Introduction

Introduction A Scholarly Career Affirming the Intelligibility of Nature

In his first book-length study after completing his two doctoral dissertations, William A. Wallace undertook a massive project that stands as something of a manifesto expressing his conviction that nature is intelligible.1 This work, Causality and Scientific Explanation, is a twovolume historical study of the relationship between the search for the causes of natural phenomena and scientific explanation.2 Beginning with Aristotle’s multifaceted notion of real causality, Wallace traced the development of this notion through the work of natural philosophers in the medieval schools of Paris and Oxford, the Renaissance school of Padua, and the contributions of Galileo and other early modern scientists. He completed his study with a look at the relationship of causality and explanation in contemporary science. This historical survey presented the evidence that the search for underlying causes has characterized the activity of scientific research from the 1. Wallace’s first book publication was the dissertation he submitted for his doctorate in philosophy at the University of Freiberg (Switzerland) in 1959: The Scientific Methodology of Theodoric of Freiberg: A Case Study of the Relationship Between Science and Philosophy, Studia Friburgensia, n.s., 26 (Freiberg: The University Press, 1959). This was followed by the dissertation he submitted for a doctorate in sacred theology in 1962: The Role of Demonstration in Moral Theology: A Study of Methodology in St. Thomas Aquinas, Texts and Studies 2 (Washington, DC: The Thomist Press, 1962). 2. Vol. 1: Medieval and Early Classical Science (Ann Arbor: University of Michigan Press, 1972); vol. 2: Classical and Contemporary Science (Ann Arbor: University of Michigan Press, 1974).

1

2 Introduction

time of its origins in the medieval schools down to the present day. Wallace acknowledged that, throughout the history of science, this causal realism was frequently challenged by the positivism of mathematicians, philosophers, and theologians who relegated knowledge of nature to a saving of the appearances. Nonetheless, Wallace argued, scientific researchers never completely lost sight of the Aristotelian ideal of explanation through underlying causes. In the years following the publication of this book, Wallace devoted most of his scholarly efforts to research in the history of science, especially in Galileo studies. Yet, his focus remained on the notion of scientific explanation as the search for the productive causes of nature. In his primary historical study, Galileo and His Sources: The Heritage of the Collegio Romano in Galileo’s Science, Wallace demonstrated the influence of the scholastic natural philosophers of the sixteenthcentury Jesuit Roman College on Galileo’s methodology.3 This established Galileo’s scientific contributions as a development within the Aristotelian tradition rather than a complete departure from it. Wallace’s groundbreaking research showed that the Aristotelian conception of the intelligibility of nature was embraced by Galileo, whose observational and experimental innovations were aimed at disclosing the underlying causes of natural phenomena. Late in his career, Wallace returned to systematic work in the philosophy of science with the publication of his magisterial The Modeling of Nature: Philosophy of Science and the Philosophy of Nature in Synthesis.4 Concerned that the skepticism of modern philosophers had

3. This work, published by Princeton University Press in 1984, was preceded by more than a decade of Wallace’s previously published Galileo studies. Representative of this work is his Prelude to Galileo: Essays on Medieval and Sixteenth-Century Sources of Galileo’s Thought, Boston Studies in the Philosophy of Science, vol. 62 (Boston: D. Reidel Publishing, 1981). 4. While this book, published by The Catholic University of America Press in 1996, is the most influential work of the last decade of his scholarly productivity, Wallace continued his work in Galileo studies during this period. He published a translation of Galileo’s commentary on Aristotle’s Posterior Analytics; the accompanying study Galileo’s

Introduction 

3

failed to provide an epistemological foundation for scientific research, Wallace sought to reassert confidence in the intelligibility of nature. He saw this as especially important as the twentieth century was coming to a close with many philosophers reacting to the doubt and positivism of the modernists by taking refuge in conventionalism and pragmatism. The widely held conception of science as mere justified belief or, worse, rhetorical posturing had come to undermine the very notion of scientific progress and of scientific research as an activity aimed at truth and certainty. Wallace set out to remedy this situation by reestablishing traditional natural philosophy as foundational for a realist philosophy of science capable of vindicating the knowledge claims of scientific researchers. In order to accomplish this, he ingeniously employed the concept of theoretical modeling as a contemporary application of the classical notion of analogy. His aim was to show that iconic and sentential models can make underlying natures intelligible to the human investigator who is seeking an explanation of natural phenomena. These three magisterial books not only mark the major periods of Wallace’s wide-ranging scholarly career but witness to various aspects of his concern with the intelligibility of nature. When Wallace began his scholarly work during the postwar period, philosophical thinking about natural science was still dominated by two early modern challenges to Aristotelian natural philosophy. One of these was John Locke’s attack on the scholastic concept of substance and the other was David Hume’s rejection of real causality. Rather than being the potentially knowable cause explaining natural subjects, substance or nature had become simply a mental collation of perceived accidental properties. Substance itself had come to be considered as, at best,

Logic of Discovery and Proof: The Background, Content, and Use of His Appropriated Treatises on Aristotle’s Posterior Analytics, Boston Studies in the Philosophy of Science, vols. 137–38 (Boston: Kluwer Academic Publishers, 1992); thirteen new articles on various topics in the history and philosophy of science; and two volumes of previously published Galileo studies.

4 Introduction

an unknowable substrate or, at worse, a mental construct. Far from being the underlying source of the natural subject and its properties, cause became a psychological disposition to expect certain constant conjunctions in experience. The positivism that resulted from these challenges reduced scientific knowledge to mere description and prediction. Modern philosophers, as well as their contemporary philosophical heirs, had abandoned the Aristotelian ideal of scientific explanation as causal demonstration. In the face of such skepticism and reductionism, Wallace reasserted a robust conviction in the intelligibility of nature. The subjects of the natural sciences are susceptible to more than simply verified theoretical description, but are open to explanation in terms of the underlying causes that constitute the reasons for their perceived properties. Wallace argued that such causal explanation had been the goal of scientific researchers throughout the history of science and that contemporary research continues to understand explanation in terms of the search for productive causes. In addition, Wallace found this Aristotelian ideal of scientific explanation foundational to the historical origins of modern science as evidenced in the experimental innovations of Galileo. Wallace also provided a contemporary account of causal explanation in terms of the process of scientific modeling. His work stands as a vigorous response to the challenges of modernism, for his scholarly efforts demonstrated that neither the history of science nor contemporary research can be fully characterized by positivism. Further, Wallace provided an antidote to the skepticism and pragmatism of the postmodern critics of modernism by providing a viable alternative account of scientific knowledge grounded in the principles of Aristotelian natural philosophy. Wallace began his intellectual career as a hands-on researcher. After completing a degree in electrical engineering at Manhattan College in 1940, he went to work at the test laboratories of the Consolidated Edison Company of New York. As war approached in 1941, Wallace joined the U.S. Navy and was assigned to the research staff of the

Introduction 

5

Naval Ordinance Laboratory. There he did basic research in underwater acoustics in support of naval weapons development.5 After a distinguished wartime career in naval research and operations, Wallace resigned his commission in 1946 and entered the Dominican Order, taking solemn vows in 1950. During his early years as a friar, Wallace not only pursued his theological studies but also completed graduate work in physics at The Catholic University of America. After his ordination to the priesthood in 1953, Wallace did further graduate work in Europe, completing his Ph.D. in philosophy from the University of Freiberg (Switzerland) in 1959 and an S.T.D. in moral theology in 1962. It was during these years of graduate studies that Wallace began his distinctive work in developing a philosophy of science grounded in traditional natural philosophy. In addition to several studies in scientific demonstration, Wallace published the first of what was to become a series of important papers on the physical foundations of the cosmological argument. These studies, the first of which is included in this collection, were aimed at showing the scientific viability of traditional arguments for the existence of God in the face of the challenges of modernism.6 Notable among this work is Wallace’s “Newtonian Antinomies against the Prima Via,” which stands as a tour de force addressing the major objections to the unmoved first Mover argument arising from Newtonian physics. These early years of Wallace’s scholarly career, from 1955 to 1975, were remarkably productive. In addition to publishing his two doctoral dissertations, he completed some fifty scholarly articles on scientific methodology, the history of science, faith and science, and various 5. A paper coauthored with F. E. Fox and published after the war provides some idea of Wallace’s contributions to the science of acoustics: “Absorption of Finite Amplitude Sound Waves,” Journal of the Acoustical Society of America 26 (1954): 994–1006. Wallace’s work in support of wartime development in naval mining is summarized in E. A. Johnson and D. A. Katcher, Mines Against Japan (Silver Spring, M.D.: Naval Ordnance Laboratory, 1974). 6. “Newtonian Antinomies against the Prima Via,” The Thomist 19 (1956): 329–70; and “Metaphysics and the Existence of God,” New Scholasticism 36 (1962): 529–31.

6 Introduction

problems in the philosophy of science. As already noted, this work culminated in the publication of his two-volume Causality and Scientific Explanation in 1972–1974. During this period, Wallace also served as the philosophy editor of the fifteen-volume New Catholic Encyclopedia, writing thirty-one of the articles himself, and authored a reference work for philosophy and theology students.7 In 1979, Wallace issued a collection of his previously published essays in the philosophy of science for use in the courses he was teaching at The Catholic University of America, where he had held the rank of Ordinary Professor of philosophy and history since 1970.8 Despite the fact that this was a minor publication originally intended for student use, it took on a life of its own in the decades that followed as a commonly cited source for challenges to contemporary philosophy of science from the perspective of a neo-Aristotelian realism. It was during this period that Wallace also became seriously involved in Galileo studies. His first major contribution to this field was his translation with commentary of Galileo’s early notebooks on astronomy and physics, published in 1977.9 This was followed, in 1981, by a collection of studies on Galileo’s sources representative of Wallace’s research of the previous decade.10 It was a period of intense scholarly activity for Wallace as his growing reputation as a Galileo scholar resulted in a number of research appointments, including senior fellowships at the Folger Institute in Washington, D.C. (1975–1976), the Institute for Advanced Study at Princeton University (1976–1977), and the Woodrow Wilson International Center for Scholars (1984). He also 7. The Elements of Philosophy: A Compendium for Philosophers and Theologians (New York: Alba House, 1977). 8. From a Realist Point of View: Essays on the Philosophy of Science (Lanham: University Press of America, 1979; second edition, 1983). 9. Galileo’s Early Notebooks: The Physical Questions: A Translation from the Latin with Historical and Paleographical Commentary (Notre Dame: University of Notre Dame Press, 1977). 10. Prelude to Galileo: Essays on Medieval and Sixteenth-Century Sources of Galileo’s Thought, Boston Studies in the Philosophy of Science, vol. 62 (Boston: D. Reidel Publishing, 1981).

Introduction 

7

received four research grants from the National Science Foundation. As already mentioned, all this activity culminated in the publication of his Galileo and His Sources in 1984. Wallace continued his work on Galileo until the end of his publishing career. In addition to numerous essays published in journals and various collections, these later publications include a Latin edition of Galileo’s important commentaries on Aristotle’s logical treatises,11 an English translation of these treatises with commentary,12 a study of Galileo’s use of Aristotelian methodology,13 and two additional collections of his previously published Galileo essays.14 The final period of Wallace’s long and distinguished scholarly career began with his retirement from teaching at The Catholic University of America in 1989. Although he intermittently continued teaching as a member of the Committee on the History and Philosophy of Science at the University of Maryland, most of his efforts during this time were directed to scholarly projects. As already indicated, he continued his Galileo studies, publishing five books and numerous articles on Galileo and scholasticism. The articles included in the third part of this collection are representative of this later period of Wallace’s Galileo scholarship. Equally important during this period were Wallace’s efforts to synthesize the generally Aristotelian approach to issues in the philosophy of science he had developed throughout his career. Representative of this work are two essays included in this col11. Tractatio de Praecognitionibus et Praecognitis. Tractatio de Demonstratione. Transcription from the Latin Manuscript with Commentary and Notes (Padua: Editrice Antenore, 1988). 12. Galileo’s Logical Treatises: A Translation with Notes and Commentary, of His Appropriated Latin Questions on Aristotle’s Posterior Analytics, Boston Studies in the Philosophy of Science, vol. 138 (Boston: Kluwer Academic Publishers, 1992). 13. Galileo’s Logic of Discovery and Proof: The Background, Content and Use of His Appropriated Treatises on Aristotle’s Posterior Analytics, Boston Studies in the Philosophy of Science, vol. 137 (Boston: Kluwer Academic Publishers, 1992). 14. Galileo, the Jesuits and the Medieval Aristotle (Hampshire: Variorum Publishing, 1991) and Domingo de Soto and the Early Galileo: Essays on Intellectual History (Hampshire: Variorum Publishing, 2004).

8 Introduction

lection. One is a little-known review essay in which Wallace places the innovative interpretations of quantum anomalies of a contemporary physicist in the context of Aristotelian realism.15 The other is a plenary address to the American Catholic Philosophical Association in 1995 in which Wallace presented a preliminary study of scientific modeling for his book The Modeling of Nature, published the following year.16 Wallace continued his scholarly activity into the new millennium, publishing his final works eleven years before his death in 2015. This long, varied, and influential scholarly career stands witness to the centrality of nature as the subject of human intellectual efforts. Wallace’s lifelong concern with the openness of nature to causal explanation as well as with the means by which scientific research can accomplish this had done much to shape the issues of the philosophy of science for the new millennium. The essays gathered here provide a sample of his innovative contributions to human understanding of nature and scientific explanation. They also stand as a provocative affirmation of the intelligibility of nature, an affirmation that Wallace himself did so much to defend and promote. 15. “Thomism and the Quantum Enigma,” The Thomist 61 (1997): 455–67. 16. “A Place for Form in Science: The Modeling of Nature,” Proceedings of the American Catholic Philosophical Association 69 (1995): 35–46.

Part I

The Intelligibility of Nature

Chapter One The Intelligibility of Nature

Chapter One

The Intelligibility of Nature A Neo-Aristotelian View

One might characterize the late twentieth century as a period when men have become oblivious of nature. Not only is the concept of human nature under attack but the broader awareness of nature itself, of things that exist by nature as opposed to those that exist through other causes, is no longer part of our mental equipment. The ecological crisis and the near exhaustion of many natural resources bear eloquent witness to this state of affairs. The scientific and industrial revolutions have made us proficient at converting the objects that surround us into artifacts, at “manipulating nature,” if you will, but they have dulled our appreciation for the intelligibility of nature in its own right.1 As an example, I would cite the latest theme to attract attention in the philosophy of science, that of scientific revolutions and theory change, which has sought to substitute the notion of progress for that of truth. According to Thomas Kuhn and Larry Laudan, among others, science can no longer be said to be concerned with investigating the truth about the universe in which we live—another way of speaking 1. The process started with inanimate nature, following the proposals of Francis Bacon, but it extends now even to human nature, with genetic engineering being the latest innovation to attract public attention.

11

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Chapter One

about the truth of nature.2 Instead, the goal of science is seen by them to be progress, progress defined in terms of problem-solving effectiveness rather than as an approach to truth. In their view, rationality has ceased to have an extrinsic norm; men are rational to the extent that they can solve puzzles or problems, not to the extent that they can understand the world of nature that surrounds them.3 Millenia ago, in his Physics, Aristotle proposed to define nature “as a principle and cause of being moved or of rest in the thing to which it belongs primarily and in virtue of that thing, but not accidentally.”4 He thought it to be quite obvious that nature exists, for it was in the context of this definition that he made his celebrated complaint about those who fail to see the obvious. “To try to prove what is evident through what is not evident is the mark of a man who cannot judge what is known through itself from what is known not through itself.”5 Nature, and things that exist by nature and according to nature, possessed for him an intrinsic intelligibility that borders on the selfevident. And yet he was far from naive about the efforts men would require to uncover nature’s secrets in detail: the precise methodological prescriptions of the Posterior Analytics and their laborious application in the De caelo, De generatione, Meteorologica, and De animalibus show that he had no illusions in this regard.6 2. Kuhn implicitly questions whether science can ever attain the goal of truth in his The Structure of Scientific Revolution, 2nd enlarged ed. (Chicago: University of Chicago Press, 1970), 170; Laudan expressly repudiates such a goal in his Progress and Its Problems (Berkeley: University of California Press, 1977), 223–25. 3. For Kuhn, a major activity of science is “puzzle solving.” For Laudan, it is “problem solving,” which he sees as the best evidence available for man’s rationality. Rather than define human progress in terms of rationality, as has been done heretofore, Laudan in fact would define rationality in terms of progress. Both thinkers seem heavily indebted to the pragmatism of John Dewey for their positions. 4. Aristotle, Physics II, ch. 1 (191b21–23). 5. Physics II, ch. 1 (193a5–7). 6. Aristotelian scholars have generally neglected to explore the relationships between the Posterior Analytics and Aristotle’s more physical treatises, seeing the Analytics as setting the ideal to which mathematicians, rather than natural scientists, should aspire. Medieval thinkers, on the other hand—Albert the Great and Thomas Aquinas

The Intelligibility of Nature 

13

Still, the judgment of history would seem to be that he and his followers failed in their attempts to make nature intelligible to the human mind. The celestial spheres proved to be their undoing—a failure understandable enough, considering how remote the heavens are from human observation.7 But even with regard to the elemental bodies they made fatal errors: one could cite their overly facile identification of natural motions, and the four-element theory to which it led, as the stumbling block that prevented geocentrism from being abandoned for two thousand years.8 Not until Galileo would anyone be found who could rectify these errors and bring about the scientific revolution during which the new physics and the new chemistry would be born.9 It was the use of experiment and mathematical come immediately to mind—were quite aware of the ways in which Aristotle applied his logical methodology to uncover the secrets of nature. See, for example, the author’s “The Scientific Methodology of St. Albert the Great,” in Albertus Magnus Doctor Universalis, 1280–1980, ed. G. Meyer and A. Zimmerman (Mainz: Matthias Grünewald Verlag, 1980), 385–407; and “St. Thomas’ Conception of Natural Philosophy and Its Method,” in La Philosophie de la nature de Saint Thomas d’Aquin, ed. Leo Elders (Rome: Libreria Editrice Vaticana, 1982), 7–27. 7. Alexandre Koyré sketches some of the difficulties that had to be overcome in his From the Closed World to the Infinite Universe (Baltimore: Johns Hopkins University Press, 1957), as does Herbert Butterfield in his The Origins of Modern Science, rev. ed. (New York: The Free Press, 1965). 8. Aristotelians used the opposing contraries, hot-cold and wet-dry, together with the motive pair, gravity-levity, to show that four elements—fire, air, water and earth— are necessary and sufficient to account for the composition of natural substances. They were reinforced in this conclusion by a somewhat naive theory of knowledge, wherein they regarded easily perceived sensible qualities as the distinguishing characteristics of the primary constituents of the universe. See note 36 below. 9. Galileo’s perfection of the telescope and his use of this instrument to close the distance, as it were, between the heavens and the earth and then see how motions in both the celestial and terrestrial regions could be explained in terms of a common set of principles was certainly a prime mover in that revolution. The seventeenth-century attack on the problems of gravity and levity, starting with Galileo and culminating in the Principia of Sir Isaac Newton, marked the second major step. In the eighteenth century, the discovery of hydrogen and oxygen and the process of their combustion solved most of the remaining difficulties posed by fire, air, and water. It was left to the nineteenth and twentieth centuries to clear up details relating to the element earth, and so forge

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Chapter One

reasoning, after all, that enabled “the Father of Modern Science” to overturn the Aristotelian cosmos and replace it with the heliocentric worldview. Neither of these methodological devices is to be found in the Stagyrite’s Organon, and one wonders how nature could ever be made intelligible without them.10 It is precisely on this point that I would focus so as to advance a neo-Aristotelian view of the intelligibility of nature. Recent researches on Galileo lead to the surprising conclusion that the Pisan physicist was himself an Aristotelian malgré lui whose knowledge of the Posterior Analytics lay behind his most important discoveries.11 Galileo not only used nature as a principle to explain the acceleration of freelyfalling bodies; he also believed that nature was highly intelligible to the divine mind and could be made equally so to the human mind provided it reasoned correctly.12 Proper reasoning, for him, involved quantitative techniques and a method of causal proportionality that made careful use of models to lay bare the hidden mechanisms of nature.13 In Galileo’s view, the intelligibility of nature was assured through the modeling of nature, using a posteriori or effect-to-cause a unity between the physical, chemical, and biological sciences through the study of atomic and molecular structures. 10. Aristotle’s approach, as opposed to Plato’s, was empirical in the sense that it used observation and experience to rise to the level of intellect, but it was not experimental in the modern sense of control over nature and made minimal use of mathematical and measuring techniques in its investigations. 11. This thesis is developed, with full documentation, in the author’s Galileo and His Sources: The Heritage of the Collegio Romano in Galileo’s Science (Princeton: Princeton University Press, 1984). 12. The comparison between divine and human intelligence was one of the passages in Galileo’s Dialogue that attracted the attention of the Roman Inquisition. More specifically, on the Third Day of his Discorsi on the “Two New Sciences,” Galileo speaks of nature determining the way in which bodies fall; earlier, on the Second Day, he admires how nature designs the bones of birds to make them suitable for flight. For details, see Le Opere di Galileo Galilei, ed. Antonio Favaro (Florence: G. Barbera Editore, 1890–1909, reprinted 1968) 7.128–129, 8.186, 8.197–198, 19.327. 13. The expression “Galileo’s method of causal proportionality” I owe to Donald W. Mertz, “On Galileo’s Method of Causal Proportionality,” Studies in History and Philosophy of Science 11 (1980): 229–42.

The Intelligibility of Nature 

15

reasoning to penetrate beneath sense appearances to the underlying reality of the universe.14 Space does not permit an historical justification of these statements or a tracing of the arguments Galileo actually advanced to establish his nuova scienza.15 Instead I shall use the theme of the modeling of nature to illustrate how the natures of things and natural processes can be made intelligible to the human mind, and indeed have been so made, through the progress of recent science.16 I propose this theme as basically Aristotelian, though it was opposed by the Peripatetics, and especially the textual scholars, who were Galileo’s adversaries at the Universities of Pisa and Padua.17 The development itself grew out of the late sixteenth-century Aristotelianism of the Collegio Romano, Thomistic in inspiration, but owing much to nominalist and Averroist contributions within the late Middle Ages and the Renaissance.18 The realist mindset it embodied can be formulated in the following theses. These I envisage as reasserting nature’s

14. Galileo’s understanding (and endorsement) of a posteriori reasoning is contained in his autograph manuscript, long neglected, in the Galileiani font of the Biblioteca Nazionale Centrale at Florence, MS Gal. 27. For a description of its contents relating to effect-to-cause reasoning, see the author’s “The Problem of Causality in Galileo’s Science,” Review of Metaphysics 36 (1983): 607–32. 15. Fullest justification will be found in Galileo and His Sources (note 11 above); earlier studies include the author’s Prelude to Galileo: Essays on Medieval and SixteenthCentury Sources of Galileo’s Thought, Boston Studies in the Philosophy of Science 62 (Boston: D. Reidel Publishing Company, 1981); and Galileo’s Early Notebooks: The Physical Questions (Notre Dame: University of Notre Dame Press, 1977). 16. An extensive literature has developed around the subject of models and modeling in the philosophy of science. Two studies that are most pertinent to the subject of this essay are Rom Harré, The Principles of Scientific Thinking (Chicago: University of Chicago Press, 1970), especially chapter 2, and Mary B. Hesse, Models and Analogies in Science (Notre Dame: University of Notre Dame Press, 1966). 17. Galileo’s polemics against the Peripatetics of his day did much to exacerbate the tensions between his thought and that attributed to Aristotle. Yet, as Galileo saw it, Aristotle took his philosophy from nature and not from books, and if alive in the early seventeenth century would have agreed with him rather than his adversaries. See Opere di Galileo 7.75 and 18.248. 18. See the works referenced in note 15 above.

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Chapter One

intelligibility in terms that are essentially Aristotelian, yet modified to meet the needs of the present day. My expectation is that they can ground not only a philosophy of science and technology but also a study of human nature and how it must function in our complex social and political world.

Thesis 1  In a general way, and abstracting from points of specific detail, nature is evident to the human mind as embracing all that exists and functions independently of man’s activity and thus is available for his contemplation and study. As stated, this thesis asserts what I believe Aristotle had in mind concerning the self-evidence of nature in the statement already quoted from the second book of the Physics. It simply juxtaposes nature to art and says that, antecedent to any intervention on man’s part, animals and plants and minerals are characterized by fairly stable ways of acting that are representative of their types.19 Their stability and their activities are determined at least partially from within, and it is this intrinsic source that enables man to attribute natures to them and identify them as natural kinds.20 The existence of nature in this broad sense, and of the natural kinds that go to make up the world of nature, is what permits classifications within the animal, plant, and mineral kingdoms in terms of common elements (genera), differentiating characteristics (differentiae), and essential constituents (species). Such classifications, one might add, are the necessary background for any theory of evolution. Those who subscribe to the evolutionary worldview and hold that homo sapiens was a latecomer within the universe implicitly hold that natural speciation had already occurred on 19. The examples given by Aristotle here evidence his concern with differentiating natural entities from artifacts, i.e., from the products of τέχνη and not of φύσις. 20. A secondary concern of the definition is to preserve the distinction between the natural and the violent, i.e., between activities that have their source within a subject and those imposed on it from without. The Cartesian mentality, which has strongly influenced modern thought, regards all inorganic activity as completely determined by external agents and to this extent obliterates the required distinction.

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17

a grand scale—before the human mind could become aware of it and attempt to situate man with respect to pre-existent species.21

Thesis 2  Natural substances are essentially intelligible in their broader classifications within the various kingdoms on the basis of sense observation and ordinary experience. This second thesis merely explicates the content of the first to make the point that the apparatus of the modern scientist is not a prerequisite for all progress in the identification of natural kinds. Some classification of substances—and by substances here I mean the primary referents or instantiations of the term “nature”22—is possible on the basis of passive observation and simple interaction with the human environment. It is perhaps noteworthy that the Latin term experimentum (like the French expérience) does not have the connotation of disturbing or intervening in nature’s operation so as to gain knowledge of it; rather it designates what might be referred to as “ordinary experience,” the common-sense observation of the world that builds up a store of information in the memory and permits secure judgments and classifications to be made.23 It is in this way that birds and fishes and insects and reptiles are differentiated one from another, as are herbs and bushes and trees, and some progress is even made in classifying minerals on the basis of their distinctive colors and 21. The very title of Charles Darwin’s masterpiece, The Origin of Species, reveals his conviction that speciation took place, by a process of natural selection, long before the advent of homo sapiens. 22. Substance is here taken as opposed to accident, the latter having its existence in another and the former existing by itself. Aristotle is explicit that only substances possess a nature (Physics II, ch. 1 [192b33]), although he later goes on to explain that the primary referents of φύσις are protomatter, πρωτή ὕλη, and its distinctive form and quality, ἡ μορφὴ καὶ τὸ εἶδος (Physics II, ch. 1 [193a29 and 193b5]). 23. This process is described by Aristotle in the Posterior Analytics II, 19, when explaining how knowledge of the universal is attained through experience, ἐμπειρία (100a5), which Aquinas renders as experimentum in his Latin commentary. The modern concept of experiment arose in the late sixteenth century, though it was adumbrated in the Middle Ages with the investigations of Peter of Maricourt (1269) and Theodoric of Freiberg (circa 1304) on the magnet and the rainbow respectively.

18 

Chapter One

crystalline shapes.24 My claim here obviously is not for any detailed classification down to the infima species, but rather for the broad identifications that are most readily apparent to man and most intelligible to his mind, and so can serve as a base for more detailed specifications made through controlled experimentation and measurement in the modern sense.

Thesis 3:  The quantitative modalities of things are not the unique preserve of the mathematician or the mathematical physicist; they also provide the naturalist with an insight into natures, particularly those of the inorganic world. Here I broach a topic that became a cause célèbre with Galileo and his Peripatetic adversaries, who used two arguments to counter the advances he proposed under his apparently Platonic or neoPythagorean maxim that “the book of nature is written in the language of mathematics.”25 In the second book of the Physics, immediately after the statements I have already quoted, Aristotle shows how the consideration of the naturalist differs from that of the mathematician, thereby introducing a near dichotomy between the qualitative approach to nature distinctive of the former and the quantitative approach of the latter.26 Again, in his discussion of proper principles in the Posterior Analytics, Aristotle cautions against μετάβᾰσις or the importation of principles from another genus subject, such as mathematics, into the study of natural phenomena.27 Conservative Aristotelians, represented by Simplicio in Galileo’s 24. It was Aristotle’s taxonomic ability, perhaps more than any other qualification, that earned for him the title, “Father of Science in the West.” 25. In Il Saggiatore, his polemic is against the Jesuit Orazio Grassi, who oddly enough was a mathematician as well as an Aristotelian. See Opere di Galileo 6.322, and note 17 above. 26. Physics II, ch. 1 (193b22–36). 27. See Posterior Analytics I, 7 (75a37–b21). Here Aristotle cautions against using arithmetic to prove a geometrical proposition, but the same applies, mutatis mutandis, to using arithmetic or geometry to prove a conclusion in natural science.

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19

Dialogue on the Two World Systems, took these warnings seriously and proscribed any use of mathematics in natural science. Some were so anti-mathematical that they not only repudiated the scientiae mediae, i.e., sciences intermediate between mathematics and physics, but even denied all possibility of demonstrative proof or causal analysis to mathematics itself.28 Progressive Aristotelians, on the other hand, particularly those with Thomistic sympathies such as Christopher Clavius and his allies at the Collegio Romano, saw mathematics as an indispensable help for the astronomer and the student of local motion, with whose aid the most convincing demonstrations could be formulated in these difficult subject matters.29 Previously, St. Thomas had taught that quantity is a proper subject of consideration in three different sciences: in metaphysics as a mode of being, and thus pertaining to the study of ens ut ens est; in mathematics, whose genus subject is ens quantum anyway; and in natural philosophy, where it is a proper attribute of ens mobile, since motus can only occur in an extended magnitude.30 Quantitative attributes such as the shapes 28. Alessandro Piccolomini seems to have been the initiator of this “antimathematical” mentality; for details, see G. C. Giacobbe, “Il Commentarium de certitudine mathematicarum disciplinarum di Alessandro Piccolomini,” Physis 14 (1972): 162–93. 29. Not all Jesuit professors, even those at the Collegio Romano, were of one mind with Clavius on the validity and importance of mathematics. Benito Pereyra, for example, followed Piccolomini in his devaluation of the mathematical disciplines. The majority of those teaching in the late 1580s and 1590s, however, were more influenced by Clavius than they were by Pereyra. One of Clavius’s students, Giuseppe Biancani, while mathematics professor at Parma, wrote an especially strong defense of his discipline. See G. C. Giacobbe, “Epigone nel Seicento della ‘Quaestio de certitudine mathematicarum:’ Giuseppe Biancani,” Physis 18 (1976): 5–40; and “Un gesuita progressista nella ‘Quaestio de certitudine mathematicarum’ rinascimentale: Benito Pereyra,” Physis 19 (1977): 51–86; also, see the following note. 30. For the different ways quantity is studied by the mathematician and the natural philosopher, see Aquinas’s commentary on Aristotle’s Physics II, lect. 3, n. 5, and on the De caelo I, lect. 1, n. 2. Note also his observations about the necessity of a quantified body to serve as the subject of successive or local motion, Physics I, lect. 1, n. 4, and VI, lect. 5, n. 10. Biancani takes up Aquinas’s teaching and further elaborates it in his De mathematicarum natura dissertatio una cum clarorum mathematicorum chronologia (Bologna: Apud Bartholomaeum Cochium, 1615), 18–19.

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and sizes of bodies—the readily apparent outlines of elephants and giraffes and cows, to say nothing of grasshoppers and mosquitos—are primary indicators of natural kinds. They provide a quick insight into the natures of things that surround us, even before we begin to build up all the qualitative characteristics that serve to enrich our knowledge of them. Valuable as quantitative attributes are for preliminary classifications within the animal, plant, and mineral kingdoms, they prove indispensable for substantial progress in the study of local motion and the investigation of the larger reaches of the universe.31 It was on this point that conservative Aristotelians opposed Galileo and failed most miserably themselves; their error can be rectified in the following statement.

Thesis 4:  Precise quantitative knowledge of inorganic substance, and of the inanimate world of the stars and planets, requires experimentation and measurement; these do not falsify or impede the study of natures, but rather lead to an identification of natural motions and of the elemental bodies of the universe. The Thomistic adage agere sequitur esse reaffirms the basic Aristotelian insight that the natures of things can only be discerned from their distinctive activities.32 As a thing acts, so it is. But in the inorganic realm, where self-initiated activity is far from being the rule, the adage must be amplified to include reactivities as well.33 Here one 31. Following Aristotle, motion or κίνησις contains under it three species: local motion, or change of place; alteration, or change of quality; and augmentation, or change of quantity (Physics V, ch. 1 [225b8f]). In the present-day, alteration and augmentation are not commonly regarded as “motions,” whereas local motion is, so much so that the adjective “local” has come to be redundant in current usage. 32. As used by Aquinas in his Summa contra Gentiles III, ch. 69, the axiom reads Agere sequitur ad esse in actu, which affirms the priority of existence over action. In view of the related axiom Omne agens agit sibi simile (III, ch. 53), however, it is also taken to mean that a thing’s characteristic activities are the primary indicators of its nature. 33. Noteworthy is Galileo’s treatment of reactivity under the rubric of resistance in his early writings. See Galileo’s Early Notebooks, 243–51. For a discussion of the

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should rather say: as a thing acts and reacts, so it is. The systematic exploration of such reactivities, as we know, is what gave rise to modern chemistry with its elaborate methods of experimentation and measurement. Without them the construction of the periodic table, and its detailed classification of the naturally occurring elements, would have been impossible. The study of the reactions on which the periodic classifications are based I would regard as the study of natural motions—understanding motion in the sense of alteratio and the generatio-corruptio to which such qualitative changes lead, and which supply knowledge of the natures of the elements and compounds in which they terminate.34 Even more important, however, is the use of metrical and experimental techniques to investigate “naturally accelerated motions,” the type of local motion to whose study Galileo devoted much of his life.35 Nature causes bodies to move locally in distinctive ways, as Galileo was well aware. Aristotle and his predecessors had used an equivalent principle to differentiate the elemental bodies into four kinds—fire, air, water, and earth—which they then used to delineate the various regions of the sublunary universe and differentiate them from the celestial spheres.36 Their understanding of gravitas and levitas was indevelopment of the concepts of action and reaction, see J. L. Russell, “Action and Reaction Before Newton,” British Journal for the History of Science 9 (1976): 25–38. 34. Chemical reactions are dependent on the inner structures of the reagents that enter into them, and in turn yield a posteriori knowledge of those structures. To the extent that such reactions are determined from within, and are not only initiated but also come to completion on the basis of this determination, they are natural in the sense of Aristotle’s definition of nature. 35. “On naturally accelerated motion” was Galileo’s title for book 2 of the treatise De motu locali being discussed during the Third Day of the Two New Sciences, published in 1638 (Opere di Galileo 8.197), but it is noteworthy that he had begun studying the phenomenon fifty years earlier and recorded his researches in the De motu antiquiora manuscript (MS Gal. 71), generally dated around 1590. 36. The celestial spheres were characterized by circular motions whereas the terrestrial regions were characterized by motions up and down, traceable to two motive principles, levitas and gravitas respectively. Earth was thought to be absolutely heavy and thus gravitated to the center of the universe; fire was absolutely light and so went

22 

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deed rudimentary; the specific gravities of substances yet remained to be determined, as did the laws of motion that regulate their tendencies toward a center of gravity.37 It would be a long way from Galileo’s experiments with inclined planes and freely-falling bodies to Aston’s experiments with the mass spectograph, but the two techniques do go together.38 Four elements are not enough; we need all ninety-four elements of the periodic table, and their isotopes as well, if we are to have an adequate understanding of the elemental bodies of which the universe is composed. Aston’s conclusion was different from Aristotle’s, but the methodology through which he reached it was basically the same: a different terminus for an elemental body tending in a distinctive way toward its proper place in a physical environment must be a primary indicator of its being a different kind, and so having a different nature.39 That the heavenly bodies are themselves composites of elements

to its periphery, whereas water was only relatively heavy (going down in fire and air but up in earth) and air only relatively light (going up in earth and water but down in fire). If natural tendencies could be realized—de facto they were not—the four elements would end up in stratified concentric spheres arranged around the earth’s center in the ascending order, earth, water, air, and fire, beyond which the heavenly regions would begin. 37. Archimedes provided the basis for the study of specific gravities in the third century B.C., but the concept of specific gravity itself was not articulated until the end of the sixteenth century. Similarly, Aristotle formulated primitive rules for the motion of bodies in terms of the forces urging them and the resistances they would encounter from the medium through which they passed. These were much debated, and revised, in the late Middle Ages, culminating in Galileo’s discoveries in the early seventeenth century. 38. The concept of mass, introduced by Newton, is crucial to an understanding of the mass spectograph, which was perfected by F. W. Aston in the early twentieth century. For a preliminary study of this concept and how it may be related to the concept of nature, see the author’s “Measuring and Defining Sensible Qualities,” in From a Realist Point of View: Essays in the Philosophy of Science, 2nd edition (New York: University Press of America, 1983), 73–97. 39. Implicit here is the notion of natural place, first suggested by Aristotle in Physics IV, ch. 4 (211a4–7). The environment employed by Aston was artificially modified to permit measurements to be made, and his specification was based on the massiveness of nuclei rather than on electronic configurations, but his overall technique sufficed for the identification of isotopes of the naturally-occurring elements.

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and isotopes identifiable here on earth could not be known without the aid of the telescope and the spectroscope.40 The apparently circular motions of the spheres fitted sense observations over twenty centuries fairly well; only after the painstaking researches of Galileo, Kepler, and Newton could one be sure that the earth and the planets, the latter like earth possessing gravitas, move in elliptical orbits around the sun.41 The classification of star types would take an additional three centuries, and even now we do not know whether the observed galactic recession is the result of a primordial explosion (and to this extent is a violent motion),42 or an evidence of anti-gravity at work (which effectively reintroduces levitas as a cosmic principle of explanation).43 I mention this not to depreciate contemporary cosmological investigations but to illustrate how our knowledge of the natures of star systems and galaxies is dependent on the motions and changes we observe them to undergo—which continues to be an application of the basic Aristotelian principle of natural taxonomy.

Thesis 5:  Quidditative knowledge of non-living substances is attainable by modeling the structural arrangements of their elemental constituents, and this despite the fact that the model is not itself the nature that is being studied. 40. Pioneering discoveries with the telescope in 1609–1610 were Galileo’s singular achievement; similarly, studies of the sun’s spectrum by Joseph von Fraunhofer in the early nineteenth century gave birth to the science of spectroscopy. 41. Both Copernicus and Galileo used circular orbits in their planetary astronomy. It was Johann Kepler who discovered that planets move in elliptical orbits, and Newton who explained why they did so with his law of universal gravitation. 42. If falling motion is naturally accelerated, as Galileo and Newton believed, then the tendency of bodies to approach each other is natural and their recession from each other is opposed to nature and so is violent. This impression is also conveyed by the expression “Big Bang” to describe the origin of the universe. 43. If galactic recession is not violent but is proceeding from natural principles, as advocated in some “Steady State” theories, then the opposite of gravity, or levity, is effectively being invoked to explain the recession. It is noteworthy that Galileo vacillated over whether gravitas and levitas are both necessary to explain natural motion, or whether gravitas alone would suffice. This is apparent in successive drafts of the treatises contained in the De motu antiquiora manuscript (note 35 above).

24 

Chapter One Earlier, I mentioned Galileo’s use of models and a method of caus-

al proportionality to arrive at his revolutionary discoveries regarding the earth’s motion. His proportionality principle was deceptively simple: similar effects must be attributable to similar causes—elevated by Isaac Newton, interestingly enough, to the status of a regula philosophandi.44 The models Galileo constructed were not very sophisticated: a replica of the moon to illustrate how its illuminated appearance could be explained in terms of mountains on its surface;45 the ship’s mast experiment to show why bodies dropped from towers on earth are ineffective to reveal the earth’s motion;46 and the barge model to illustrate how the tides might originate from forces produced by the earth’s diurnal rotation on its axis and annual revolution around the sun.47 In each case, Galileo was able to study, in the model over which he had control, the relationship between a known effect and its known cause so that he could identify a similar effect in nature and then reason to its unknown cause as the missing element in the proportion. (Proportion here, I may observe, is the proper translation of the Greek ἀναλογία, early used by Aristotle to unmask the nature of ὕλη πρωτή or materia prima, the protomatter that underlies all natural changes, and later used by Aquinas to reason to the nature of God himself.)48 Not all of Galileo’s modeling techniques were effective, and yet he and his followers were able to propose a physical model of the known universe that marked a great advance over the mathematical system of Copernicus. Less successful was the atomism with which Galileo flirted in his middle years. But here too he made a start that has yield44. For the principle, see Mertz (note 13 above); Newton formulates it as rule 2 of his “Rules of Reasoning in Philosophy,” which he enumerates at the beginning of bk. 3 of the Principia and which reads: “. . . to the same natural effects we must, as far as possible, assign the same causes.” 45. In the Dialogue of 1632, Opere di Galileo 7.111–112. 46. Opere di Galileo 7.167–171. 47. Opere di Galileo 7.456. 48. Aristotle, Physics I, ch. 7 (191a8) “. . . κατ’ ἀναλογίαν.” Aquinas, Summa theologiae Ia, q. 13, a. 5, “. . . secundum analogiam, idest proportionem.”

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ed important results for our present day knowledge of the natures of elements, compounds, and inorganic substances generally.49 Within an Aristotelian-Thomistic framework, matter is usually regarded as the root of unintelligibility, so much so that entities immersed in matter are seen as opaque to the human intellect and thus as escaping quidditative understanding.50 Some would argue that man cannot grasp the nature of any being below himself on the Great Chain of Being and a fortiori can never know the quiddity of inorganic substances.51 As counter-arguments, however, consider the ways in which we presently classify the elements of the periodic table and define them in terms of their valencies and distinctive chemical activities. Even better, consider how the Bohr model of the atom has been used to represent structural arrangements of nuclei and orbital electrons to explain such valencies and the resulting bonding in the molecule. Yet again, look at how x-ray studies of the lattice structure of crystals provide the means whereby we now construct reliable models of non-living substances all the way from snowflakes and common salt to the highly complex DNA molecule. With such knowledge of material components and formal arrangements, would one wish to say in the late twentieth century that we know less about the nature of water and salt than we do about the nature of the being we define as animal rationale?52 49. See W. R. Shea, “Galileo’s Atomic Hypothesis,” Ambix 17 (1970): 13–27, and H. E. LeGrand, “Galileo’s Matter Theory,” in New Perspectives on Galileo, ed. R. E. Butts and J. C. Pitt (Boston: D. Reidel Publishing Company, 1978), 197–208. Recently Pietro Redondi has argued that Galileo’s atomic theory was more a factor in the condemnation by the Inquisition than a commitment to the Copernican system; see his Galileo Eretico (Turin: Einaudi, 1983). 50. For Aquinas’s view, see Summa contra Gentiles II, ch. 75: “quod repugnat intelligibilitati, est materialitas.” 51. This has been the teaching of many commentators on St. Thomas, including Jacques Maritain, who sees it as imposing an essential limitation on natural philosophy, requiring it to be replaced in large part by the empirio-metric and empirio-schematic sciences. 52. The proper object of the human intellect, in Aquinas’s view, is the quiddity of a material thing: “Intellectus . . . humani, qui est coniunctus corpori, proprium obiectum

26 

Chapter One In each of the cases cited, I would argue that scientists have suc-

cessfully modelled the natures of elements, compounds, and various minerals, and thus possess quidditative knowledge of these substances in terms of which they can demonstrate most of their properties. To maintain this I need not hold that the microstructure of NaCl or H20 is exactly the way it is portrayed in a model wherein miniature red spheres are used to represent electrons. The model is not itself the nature of the substance, and yet it gives us a proportional insight—an analogous understanding, if you will—into that nature and renders it intelligible to our minds.53 Aristotle may have been limited to the contraries heavy­light, hot-cold, and wet-dry to characterize the natures of the elements and the mixta generated from them, but we are under no such limitation if we continue to apply his methods of classification and definition within the world of the inorganic. This is not the place to digress on the subject of laws of nature, but it is precisely the type of understanding to which I have just made reference that enables one to explain such generalizations as “All emeralds are green” and “All copper expands when heated.”54 To make a est quidditas sive natura in materia corporali existens” (Summa theologiae Ia, q. 84, a. 7). Granted that man himself is the object most proportioned to his intellect, and therefore the object of which he can have the most detailed knowledge, this does not preclude the possibility of his attaining essential or quidditative knowledge of other material objects. Indeed, Aquinas maintains that knowledge of the nature of a material thing (natura materialis rei) is prerequisite to his coming to know his own intellect (Ia, q. 87, a. 3). 53. For Aristotle, a general knowledge of the substance of a thing constitutes the first step toward understanding its nature. In this respect his theory of knowledge was almost the direct opposite of Descartes’s, who held that the clear and distinct idea is the starting point for the attainment of truth. The movement from general (and confused) understanding to particular (and distinct) understanding can be mediated through modeling techniques, as strikingly illustrated in the history of modern chemistry. 54. Implicit here is the famous “problem of induction,” which continues to agitate philosophers of science who follow in the footsteps of David Hume. If one denies the possibility of discerning causal connections in nature, or of grasping by intellect the essential characteristics of things, one will never be able to move from the observation of singulars to the affirmation of universal propositions. The problem is clearly not one of formal logic, which perhaps explains why it remains refractory to solution through the use of logical techniques.

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27

law-like assertion of this type, one need only be assured that he has sufficient knowledge of the substance being discussed to be able to state: “Under conditions c, x will exhibit property p precisely because it possesses nature n, which is modelled by the structural arrangement its elemental constituents exhibit.”55 Here again the model that is proposed is not itself the nature, but it provides sufficient knowledge of that nature to enable one to understand the properties and characteristics of most natural substances.

Thesis 6:  By extension of the foregoing thesis, natures in the microcosm and those in the megacosm are intelligible to man to the extent that they too can be modelled on the basis of what he knows about the macrocosm, the world of ordinary experience. Before the invention of optical and other instrumentation, it was practically impossible for man to investigate the world of the very small, the microcosm, and that of the very large, the megacosm, both of which are remote from the macrocosm, the world of ordinary experience. But as distant objects are brought closer, it is possible to discern more and more of their defining characteristics, so that what is more known to us in sense experience gradually leads us to the intellectual knowledge of what is more known by nature and in itself.56 This is the basic technique we have just been discussing to arrive at an understanding of inorganic substance. Needless to say, it can readily be extended into the world of subatomic particles and to the remote regions of space to render intelligible aspects of the universe that were completely shut off not only to Renaissance Aristotelians but to Galileo, Newton, and the founders of modern science.57 55. For a similar formulation and its justification, see Harré, Principles of Scientific Thinking, 186–88; also the author’s Causality and Scientific Explanation, 2 vols. (Ann Arbor: University of Michigan Press, 1972–74; reprinted New York: University Press of America, 1981), 2.271–76. 56. Such is the methodological procedure outlined by Aristotle at the outset of the Physics I, ch. 1. 57. For example, telescopic observations and Newtonian mechanics enable us to

28 

Chapter One With regard to the subatomic, much work has been done on the

structure of the nucleus, with a variety of models being proposed to account for its properties. Elaborate classificatory schemes have been thought out for the particles, or wave-particles, of high energy physics, and the ways in which all of these may be constituted from “quarks” of different types.58 No less interesting is the progress made in investigating the natures of “quasars,” “pulsars,” and the “black holes” that possibly inhabit the depths of space. In such areas of research no one would make the claim that demonstrative science has been achieved, or that the entities discussed are such that they possess natures in a clear and unambiguous way. And yet it would be foolhardy to insist that these are all entia rationis with no counterpart outside the human mind.59 A dialectical knowledge of them, and a provisional sketch of their defining characteristics, prepares the way for the understanding of their natures—to the extent that they have natures—with the progress of science within the twenty-first century.

Thesis 7:  Human nature itself becomes more intelligible in terms of the models science is now able to provide for genetic materials and artificial intelligence. Here, with my reference to human nature, I come to a specific application of discourse on the intelligibility of nature generally. Many understand the structure of the solar system, but without spectroscopic study of redshift we would know nothing of galactic recession and the possibility of an expanding universe. Similarly, the use of artificial satellites and space probes may be expected to increase dramatically our knowledge of the “depths of space” in the immediate future. 58. The work of Murray Gell-Mann on the “eight-fold way” illustrates this procedure very well; for a philosophical analysis of this and similar investigations, see essays 8 and 9 of the author’s From a Realist Point of View, 2nd ed., 171–212. 59. An ens rationis, or being of reason, is something the mind makes up but has no extramental existence; an ens reale, or real being, on the other hand, exists outside the mind, although when known it also takes on an intentional mode of existence in the mind. For a fuller explanation of this distinction, see essay 3 in From a Realist Point of View, 45–69. The instrumentalist school in the philosophy of science generally regards all the concepts and constructs of recent science as entia rationis, whereas the realist school accords many of them the status of entia realia.

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29

philosophers find it difficult to comprehend natures below the level of the human, and yet they experience no difficulty with man himself. The human organism obviously lends itself to reflective awareness in ways that cannot be matched by other structures and composites. So vast are its capabilities that it invites us to extend our inquiry into the domain of Aristotle’s De anima (and related treatises), to investigate how cognitive natures can be better grasped through the application of modeling techniques. Having mentioned the DNA molecule, I would first cite advances in molecular biology for the insight they provide into human hereditary characteristics. The science of genetics has enhanced considerably our knowledge of reproductive biology, and with this growth of understanding of man’s early development we somehow feel that we have gained a better insight into human nature itself. Models presently available for the replication of genetic materials and the coding of particular traits provide a much better insight into the material substrate of human activity than anything heretofore available.60 Man is still the animal rationale, but we have a much more sophisticated knowledge of all that is implied in the animal part of that definition when we contemplate it in the light of recent biological research. With regard to the rationale part, this too can be better understood through the use of models. Here I direct attention to research within the past few decades into cybernetics and computer science, to the burgeoning field of AI or artificial intelligence. Artifacts are different from natural entities, but just as art imitates nature, so the artifacts we construct provide privileged insights into the hidden mechanisms of nature.61 Thanks to progress within the computer field we now have better comprehension of the nature of memory, perception, abstrac60. The discovery of the structure of the DNA molecule in 1953 by F. Crick and J. Watson has revolutionized genetics and brought genetic engineering, for good or for ill, into the realm of possibility (note 1 above). 61. A provocative study exploring ways in which this is done is Herbert A. Simon, The Sciences of the Artificial (Cambridge, Mass.: The M.I.T. Press, 1969); see also his Models of Man: Social and Rational (New York: John Wiley & Sons, Inc., 1957).

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tion, and the reasoning process itself. The modeling of mind is perhaps the most intriguing of all the developments I have mentioned, offering a striking example of how nature can be made more intelligible when we include human nature within its scope.62 But man is more than mind. He also has a will and emotional capabilities that are intimately linked with his rationality. These are extremely important, since they are the controlling factors behind his activity precisely as human. It is difficult to find counterparts for such powers in machine activity, and this makes their modeling more difficult than that of cognitive faculties. On the other hand, appetition is not completely refractory to human understanding: relationships between varieties of perception and the emotions they arouse, as well as the inverse effect of passion on cognition, have been investigated by psychologists for decades. With regard to the analogous relationship between intellect and will, philosophers have speculated on this subject since the time of Plato. The mentality of some behaviorists, who would regard these components of human nature as so many “black boxes” whose contents can never be unveiled, would negate such hard-won advances of Western Civilization. Much better to speculate about their contents, to use τέχνη to gain a fuller understanding of φύσις, and thus to model all the dimensions discoverable within the rational composite.63

Thesis 8:  Such speculative understanding of human nature is but a preliminary for the study of activity that is perfective of the individual, for the development of models that can be prescriptive for human behavior. 62. For a sampling of work in this field at the Philosophic Institute for Artificial Intelligence, University of Notre Dame, see K. M. Sayre and F. J. Crosson, ed., The Modeling of Mind: Computers and Intelligence (Notre Dame: University of Notre Dame Press, 1963); F. J. Crosson and K. M. Sayre, ed., Philosophy of Cybernetics (Notre Dame: University of Notre Dame Press, 1967); and F. J. Crosson, ed., Human and Artificial Intelligence (New York: Appleton-Century-Crofts, 1970). 63. A start in this direction has been made by the author in his “Computers and the Modeling of Man,” in From a Realist Paint of View, 245–71.

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The axiom agere sequitur esse has another meaning apart from that already referred to. Not only do activities reveal the natures from which they proceed, but natures themselves prescribe the types of activity conformable with them.64 For example, if man is an animal rationale, he can only manifest and fulfill his nature by acting reasonably; he cannot do so with irrational behavior. A principle such as this forms the basis for what has come to be called “natural law” morality. Centuries ago, Aquinas laid out the basic precepts that underlie its code of ethics: (1) in common with living things and all other beings, a human should do whatever is necessary to maintain life and continued existence; (2) in common with other animals, he should ensure continuation of the species by reproducing and caring for offspring; and (3) as properly human, he should pursue truth, exercise freedom, and cultivate virtue.65 Aquinas saw these precepts as providing rational justification for the “Thou shalt not’s” of the Decalogue, but he also saw them as extending much further to formulate ideals of conduct at which all humans should aim. Just as one can model a person’s rationality by showing the relationships and interactions between his powers and capabilities— between intellect and will; perception, imagination, etc., and the emotive reactions they evoke; and various sensory and motive powers—so one can model a person’s activity by indicating ways in which each of these faculties may be brought to perfection.66 The basic options for doing so were outlined by Aristotle in the Nicomachean Ethics in terms of the virtues and vices humans acquire through repeated activity.67 64. The movement here is analogous to that of resolution and composition as employed in the School of Padua at the end of the sixteenth century, which found fruitful application in the medical faculty there. One could “resolve” a particular (aberrant) phenomenon back to a series of underlying causes, and then by suitably “composing” the causes thus discovered could reconstruct the phenomenon in the way it was intended by nature. For details and references to the literature, see the author’s Causality and Scientific Explanation, 1.117–155. 65. Summa theologiae IaIIae, q. 94, a. 2. 66. See “Computers and the Modeling of Man, 265–69. 67. Especially in books 2 through 7 of that work; similar material is covered in

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Not only do people develop skills and personality traits, but they also develop character, and do so whether they consciously intend it or not. In a Christian setting, Aquinas integrated man’s moral and spiritual life into this Aristotelian schema, providing in the Secunda Pars of his Summa Theologiae an exhaustive analysis of human perfectibility at all levels of individual, communal, and religious life.68 The basic insight of both Aristotle and Aquinas was that virtues, or good habits of acting, can be acquired through repeated actions moderated by right reason. A person develops a good character by acquiring the cardinal virtues—prudence, justice, moderation, and courage. These become for him “second natures,” as it were, habituating him to act reasonably, i.e., to control his natural passions and to give to others their due. In this way the person himself becomes good, and so more fully human. The individual who fails to acquire virtue, on the other hand, and for example is repeatedly unjust in his dealings with others, inculcates a character defect and to this extent is stunted precisely as human.

Thesis 9:  Apart from this ethical dimension, man is further perfectible in the domain of social and political affairs, though here the development seems less determined by nature than is his personal perfectibility. A human being is never completely self-sufficient: he comes into the world dependent on parents, grows up within a family context, and requires the additional resources of the state to reach intellectual and moral maturity. Family and state, in some form or other, thus seem practically necessary for the development of a rational being; an animal rationale is by nature and instinct an animal sociale, and homo sapiens cannot help but also be homo politicus. Apart from these “quasi-necessary” societies, however, humans enter into innumerable communities and free associations that prove useful for promoting his Eudemian Ethics, books 2 through 6, and in the short compilation made within his school, On Virtues and Vices. 68. IiaIIae, qq. 1–170.

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the common good. These are less determined by human nature, as witnessed by the great variety of institutions found in successive stages of history and in different cultures. Even the agencies of government change endlessly—those regulating taxation, education, armed forces, criminal justice, to name but a few. The institutions required to foster and regulate economic activity offer perhaps even better illustrations of the variety of ways in which man’s rationality asserts itself. These and similar organizations are the concern of social and political scientists, who analyze their effectiveness and evaluate them in relation to the goals they aim to achieve. It is within the areas of such sciences that modeling techniques have received their greatest development to date. Thus far I have referred to models in their speculative functioning, as they provide an insight into the natures of entities remote from human understanding. Being an artifact, a model is more intelligible than the entity it models, for one normally has better understanding of something he has made than of something he discovers in the order of nature. But models are not limited to the speculative; they also prove useful in the practical sphere. They offer means of simplifying complex phenomena and testing quantitative relationships among elements that otherwise defy precise analysis.69 Just as models can make natural entities intelligible, so they can capture the essential characteristics of the institutions studied in the human sciences and suggest practical measures for their improvement. It is here too that their connection with nature, and especially with man’s nature, becomes important. One tends to think of these sciences as descriptive rather than prescriptive, despite the fact that their findings are proximately ordered to decision-making that affects the well-being if not the destiny of countless human beings.70 For Ar69. See, for example, Hubert Blalock, Causal Models in the Social Sciences (Chicago: Aldine Publishing Co., 1971). 70. In another way of characterizing it, their work may be seen as analytical, as resolving complex phenomena and situations to principles and elements that may serve

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istotle, politics was the architectonic science, even though for him it was concerned with the most contingent of subject matters and permitted the least certitude in its conclusions.71 Its most helpful adjunct was the art of rhetoric, whereby the head of the polis could persuasively urge courses of action that might cultivate virtue, peace, and well-being in its members. Today communications theory is preempting the field of rhetoric, but not always with the same concern for character development and the values that were generally acknowledged as the goal of political action in the Greek city state. Yet, in a period when drugs and alcoholism are on the rise, when the arms race threatens the destruction of the species, when pollution of the natural environment and depletion of its resources are a continuing problem, it would seem that normative studies, based on nature and on what it means to be truly human, should rank among the highest priorities. This would seem to exhaust the theme with which this essay began and the theses one might formulate in its support. Perhaps there is room for yet one more thesis, bringing them to an even ten, so let me formulate it as follows.

Thesis 10:  The Author of Nature, although most remote from human understanding, can also be modeled from a study of his handiwork—the world of nature that is his artifact—and thus made more comprehensible to man. This last thesis has more the nature of a corollary or a lemma that

to explain them, without attempting the task of recomposing in the sense of note 64 above. 71. Being an architectonic science, it was also for him a practical science, and thus concerned with putting rationality into things to be done. Aristotle saw the Politics as an extension of his Ethics into the domain of public affairs, but in his extant writings gave only the briefest indications as to how such an extension might be effected. Within a Thomistic context, the author has addressed this problem in his The Role of Demonstration in Moral Theology (Washington, D.C.: The Thomist Press, 1962); see also “Being Scientific in a Practice Discipline,” in From a Realist Point of View, 273–93, for applications to the health sciences.

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hints at further development than a statement capable of standing on its own. Obviously, it is not my intention to make an excursus into metaphysics or natural theology when speaking of the Author of Nature. I would simply stress that nature’s intelligibility is not so limited and impoverished as to keep our eyes forever fixed on its material dimensions. In a sense one could say that nature, properly understood, has a surplus of intelligibility that enables us to transcend matter and come to a knowledge of forms that exist in separation from it.72 Aristotle certainly thought this possible, and made a strong case for it at the end of his Physics.73 No less optimistic was Galileo, who saw his method of causal proportionality as shedding light on the way God could have put his world system in motion,74 and Newton, whose General Scholium at the end of the Principia extolled the Supreme Being who must be responsible for nature’s handiwork.75 But it was Aquinas, the acute student of analogy and causality, who developed to the fullest a “God-talk” based on the world of nature. The models he provided in his quinque viae and his two great Summae have stood among the loftiest achievements of the human mind, enabling the close student of nature, through their use, to catch a glimpse of divinity itself.76 With this I bring to a close what I have characterized as a neoAristotelian view of the intelligibility of nature. Its main lines, as I have argued, were charted by “the master of all who know,” but even he could not see how far the program he initiated would ultimately lead. Paradoxically, it was Galileo, one of the most loudly proclaimed opponents of the Stagyrite, who pointed the way around obstacles that had stalled the advance of knowledge for almost two millennia. 72. Even modern science preserves vestiges of immateriality in the concepts it employs, as sketched in the author’s “Immateriality and Its Surrogates in Modern Science,” in From a Realist Point of View, 297–307. 73. Physics VIII, ch. 5–10. 74. Opere di Galileo 8.283–284; compare 229. 75. In the second edition of that work, following book 3. 76. Summa theologiae Ia, q. 2–26; Summa contra Gentiles I.

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The modeling of nature, with a renewed appreciation of the role of mathematics and experimentation in that task, has turned out to be the key to its intelligibility. If we pursue the progressive Aristotelianism under whose aegis Galileo worked, perhaps unwittingly, we need have no fear that nature’s secrets will remain impenetrable to our minds. Natural entities—human beings and the institutions they devise to enhance their rationality included—are still the objects most proportioned to man’s intellect.77 Indeed, without knowledge of them, one can make little progress toward any ultimate truth.78

77. Summa theologiae Ia, q. 84–87. 78. A preliminary version of this essay was presented at the World Congress of Philosophy, Montreal, in August 1983; it has been considerably amplified and documented during the author’s residence at the Woodrow Wilson International Center for Scholars, Smithsonian Institution, Washington, D.C., in 1984.

Chapter Two A Place for Form in Science

Chapter Two

A Place for Form in Science The Modeling of Nature

It is commonly held that Aristotle’s teaching on substantial or natural form is in no way relevant to the physical or natural sciences as they have developed since the seventeenth century. In this paper I would like to counter that view and propose that form in general not only plays a critical role in twentieth-century science but that this role can now be extended to include even substancing or natural form. Indeed, such an extension is vital for advancing the cause of realism in science—a cause that has many advocates among philosophers of science, few of whom make a convincing case in its support. The twentieth-century developments on which I would focus are three: the current replacement of theories by models in all branches of science; the extraordinary growth of computer graphics that makes such models intelligible even for the non-scientist; and advances in cognitive science that provide tools for the simulation of life activities. Through innovations such as these, nature is rapidly being made intelligible to the human intellect in ways that could not even have been imagined by previous generations.1 1. The full development of my thesis will be found in The Modeling of Nature: Philosophy of Science and Philosophy of Nature in Synthesis (Washington, D.C.: The Catholic University of America Press, 1996), whence the title of this paper.

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Aristotle’s Terminology To make my case I shall presume knowledge of a few texts from the Physics and De anima of Aristotle that supply the foundations of my argument. First come the statements in the Physics that the term nature (φύσις), “the principle and cause of motion and of rest in that in which it is essentially and not merely incidentally,” can be applied both to the basic stuff of which things are constituted (πρωτή ὕλη or protomatter) and to the form that determines them to be the natural kinds they are (their εἶδος or οὐσία), what I shall henceforth refer to as natural form. Important here is Aristotle’s comment that, “as to this underlying nature [protomatter], it is knowable by analogy (κατ’ ἀναλογίαν),” his open invitation to the use of modeling techniques. Equally important is his constant use of the couplets δύνᾰμις and ἐνέργεια, potentiality and actuality, to explain the workings of nature. From the De anima we then have Aristotle’s definition of the soul or ψῡχή as “the form of a natural body having life potentially within it,” plus his further clarification that there are different grades of actuality. Soul is the first actuality of a living body—here using ἐντελέχεια, a synonym for ἐνέργεια, to characterize the kind of actuality this is. Soul is the actuality of a body in the sense that sight is to the eye and chopping to the axe, that is, the energizing of the tool to the tool itself. Then there are the various δυνάμεις or powers with which souls are endowed and which they exhibit in the manifold life activities found in the biosphere. These are obviously forms of a different type, power forms that are distinctive of natural kinds in the inorganic realm and in the plant and animal kingdoms. Other types of form are peculiar to animal organisms, where knowledge is first found in the universe— cognitional forms or intentional forms that inform their cognitive powers. When we consider human nature, yet another type of form turns out to be essential for understanding human activity, the habit or ἕξις that is the more proximate source of such activity, knowledge of which can be of help for determining the kinds of people we are.

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I shall range through all these types of form in my presentation, but my aim is to show that all are reducible ontologically to natural form, the correlate of protomatter, through which they ultimately become intelligible.

An Overview of the Modeling Project Since I propose to use the concept of model to explain how this intelligibility is manifested, let me briefly sketch the historical evolution of my own line of thought on this subject. It started in 1961 when I gave a lecture series at M.I.T. on Thomism and modern science.2 In those days, Norbert Wiener’s Cybernetics was popular and was being applied in cognitive science to develop the field of artificial intelligence. Block diagrams with feedback circuits abounded, so I used them to explain not only how robots work but also how cognitive and motive powers function in animals and humans. The starting point at the time was the stimulus-response model of the “black box” then favored by behaviorists. This was in effect replaced by a receptor-activator model, which preserved the S-R feature but differentiated two basic capabilities of the robot. The receptor, for example, might be a photocell and a tactile sensor, whereas the activator would be some type of motor mechanism. The next step further differentiated the receptor and activator capabilities by adding memory circuits to the receptor line, and then some programmed responses to the activator line that would permit the robot to respond selectively to incoming signals; these two functions might be called memory and motivator respectively. Both capabilities, when energized by the required circuitry, can be referred to as “powers.” Such powers are activated under appropriate stimuli, which then elicits a distinctive response from the automaton. Actually, with this we have the essential features for modeling an animal 2. Some of the ideas I developed in these lectures are explained in my “Cybernetics and a Christian Philosophy of Man,” in Philosophy in a Technological Culture, ed. G. F. McLean (Washington, D.C.: The Catholic University of America Press, 1964), 124–45.

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organism. Instead of electrical and mechanical sensors, an animal is equipped with various powers of sensation, corresponding to its outer senses; it also has sophisticated powers of perception in its inner senses that go far beyond electronic memory. These make up its receptor line. Corresponding to them in the activator line are motor and emotive powers respectively. For some of its activities motor responses are triggered directly by perception; for others they are mediated by an emotional response, which can be either impulsive or aggressive. Further explaining the human intellect and will to engineers, and particularly the human soul, presented more of a challenge. My first attempt simply added the two additional powers that are proper to human beings, intellect to complete the receptor line and will to complete the activator line. Then, to make provision for the complex of powers to control the development of the human organism—those of nourishment, growth, and reproduction—all of which animals have in common with plants, I inserted another block or “power” below the others to take care of vegetative activities. Finally, to explain the soul as an animating principle, since engineers would be expected to know that robots had to be energized in order to function, I used electromagnetic theory to explain this to them. I updated Aristotle’s analogy, namely, just as sight is to the eye, and chopping to the axe, so an energizing field is to soul: it is what enlivens the body and so is the first principle behind its vital activities. I marked a reference point at the lower left of the block diagram, and then drew a series of concentric dashed lines radiating from it.3 This suggests a field that serves to energize the entire network—the entity, whatever it is, that converts all of the boxes into functioning powers and makes the organism alive and fully human. The traditional name for it is the soul, the animating 3. This was first explained in an essay entitled “Cybernetics and the Modeling of Man” in my From a Realist Point of View: Essays on the Philosophy of Science (Washington, D.C.: University Press of America, 1979), 219–45; this essay was slightly revised and bore the new title “Computers and the Modeling of Man” in the second edition of that work (New York: University Press of America, 1983), 245–71.

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factor that enlivens man’s body and renders it capable of exercising its life activities. This learning device proved more successful than I anticipated, so much so that in 1970, when I began to teach philosophy of science to graduate nurses at Catholic University, I developed it into what I then called the “life-powers model.” The plan was simple: if one can identify life and a living body, one can understand the soul and its animating function. A live body is animated or besouled, a dead body is not. Just as the body functions through its various organs, so the soul functions through powers that animate these organs. The blind man cannot see because his visual organs are defective and his power of sight cannot work; a dead man cannot see because seeing is a vital operation. He is no longer animated, his soul has left his body, and an organ such as his eye can no longer function. Nursing students are very interested in the concept of health, and so for them I extended the “life-powers” model to show how health can be incorporated into it as an entitative habit or disposition associated with the various powers. To this point I had used rectangular blocks to represent powers; now I appended hexagons to the rectangles to indicate that the powers or the organ systems they activate are healthy in the way they function. Meanwhile, I had updated the vegetative powers to make them four in number, so as to provide for the modern notions of homeostasis and metabolism as well as the more traditional developmental and reproductive powers.4 Since the soul is a natural form and as such is a nature in Aristotle’s understanding, I often wondered how this simple model of human nature might be extended to explain not only animal and plant natures but inorganic natures as well. Not until 1984, when I had a sabbatical leave and a fellowship at the Woodrow Wilson International Center for Scholars, did I have the opportunity to work

4. Diagrams illustrating some of these new features are reproduced in the article cited in the following note.

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on that problem. There I finally puzzled out how protomatter and inorganic forms could be incorporated into the model. I then wrote up a synoptic view of my solution for The Thomist, and that appeared in 1985.5 Its appearance in that journal was quite appropriate, since the solution was practically “lifted” from St. Thomas’s treatment of the powers of the soul in the First Part of his Summa Theologiae. Shortly after its publication, which exhibited models of all four types of natures, I gave a paper to an interdisciplinary conference on philosophy and medicine at Georgetown University. By that time, my model was no longer a “life-powers model” but had become simply a “powers model,” one applicable to non-living natures as well. As such, it could be adapted to discussing the beginnings and endings of life. I used it at that conference to introduce the concept of transient natures and how these might relate to human beginnings, to what is called delayed hominization. The paper was published in 1989, when it appeared, with models now clearly illustrated, in a volume of Kluwer’s Philosophy and Medicine series.6 A year after that was published, in a lecture at Catholic University I made more emendations to the model to discuss its extension to the ending of life, to what is termed dehominization—brain death, dementia, and persistent vegetative state.7 My main preoccupation at the time was to bring to completion my lengthy researches into Galileo’s early Latin manuscripts, but I still 5. “Nature as Animating: The Soul in the Human Sciences,” The Thomist 49, no. 4 (1985): 612–48. The title mentions only the human sciences, but the article dealt not only with human nature but with other natures as well. Diagrams for inorganic natures are given on p. 620, those for plant natures on pp. 624 and 626, and those for human nature on pp. 630 and 632. The use of hexagons to represent healthy functioning is explained on pp. 634–36 and then diagrammed on p. 639. 6. “Nature and Human Nature as the Norm in Medical Ethics,” in Catholic Perspectives on Medical Morals: Foundational Issues, ed. E. D. Pellegrino, J. P. Langan, and John C. Harvey, Philosophy and Medicine 34 (Boston: Kluwer Academic Publishers, 1989), 23–53. This additionally supplies a model for animal natures, shown on p. 34. 7. Published four years later, this essay appeared as “Aquinas’s Legacy on Individuation, Cogitation, and Hominization,” in Thomas Aquinas and His Legacy, ed. David M. Gallagher, Studies in Philosophy and the History of Philosophy 28 (Washington, D.C.: The Catholic University of America Press, 1994), 173–93.

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continued to tune and retune the powers model of nature and natural kinds. Having done what I could for medical ethics, I was anxious to apply the model to problems in the philosophy of science.8

The Changing Scene in the Philosophy of Science During most of my academic career, the discipline known as the philosophy of science has been dominated by positivists and logical empiricists. Under the spell of David Hume, most of those working in the field have steadfastly denied any possibility of grasping a causal connection. Most also aligned themselves with Immanuel Kant in professing a radical agnosticism: the human mind is forever incapable of knowing things as they are in themselves. With dogmas such as these abroad, one could hardly expect a hearing when speaking of causality, or substance, or natures, or powers, to say nothing of materia prima and forma substantialis. Perhaps that explains why so few members of our Association conduct serious work in the philosophy of science. It is important, however, to note that the scene is now changing in that discipline. No longer are the positivists and empiricists in complete control. The field in fact has been in disarray for the past decade or two, and only recently has anything like a new consensus begun to emerge.9 Within that consensus, surprisingly enough, there are a few developments that might prepare for the recovery of form in the natural and human sciences. It is to these I now turn. The most striking change is the reintroduction of the concepts of natural kinds and causal efficacy into the current literature. “Natural kinds” comes from a most unexpected source, Willard Van Orman Quine, and “causal efficacy” from a similar source, Wesley Salmon—

8. It is this work that has culminated in the book referred to in note 1 above. 9. The outlines of such a consensus may be seen in a recent anthology, The Philosophy of Science, ed. R. Boyd, P. Gasper, and J. D. Trout (Cambridge, Mass.: The M.I.T. Press, 1991). Along similar lines is the Introduction to the Philosophy of Science, ed. Merilee Salmon et al. (Englewood Cliffs, N.J.: Prentice-Hall, 1992).

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both ranked among the highest authorities in the field. The idea of natural kinds or species is of course essential to evolution, as shown by work in the philosophy of biology by Ernst Mayr and others. Now Quine’s broader idea, that natural kinds are the givens in all areas of scientific investigation, that they are the basic causal features of the world, is becoming influential.10 Salmon, after doing an extended study of the covering-law model of scientific explanation over a forty-year period, has shown that the model really does not explain anything.11 Causality involves more than successions of events: it does have an ontological component that can be displayed by a proper analysis. Now, admitting natural kinds is not very far from admitting natures, and when these are coupled with causes actually causing, one is not far from the “causal powers” promoted for many years by Rom Harré and Edward Madden, yet largely ignored by authorities in the field.12

The Modeling of Mind A second development is the rapid growth of cognitive science as a specialty within the philosophy of psychology. This new field has delivered the death blow to behaviorism and the “black-box” mentality long dominant in psychological theorizing. Cognitive scientists have become convinced that, when modeling mental processes, they are not dealing with boxes that are empty or opaque to their understanding. They have joined forces with neuroscientists and computer specialists to show that knowing functions cannot be understood without representations of some type in the mind of the knower. To speak 10. See Quine’s contribution entitled “Natural Kinds” in the anthology The Philosophy of Science mentioned in the previous note, 159–70. 11. See his Four Decades of Scientific Explanation (Minneapolis: University of Minnesota Press, 1990). 12. See Rom Harré and Edward Madden, Causal Powers: A Theory of Natural Necessity (Oxford: Blackwell, 1975).

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of mental representations, of course, is to reopen the study of concepts, a necessary step toward showing how natures or natural kinds are known and can serve as starting points for scientific investigation. Related to the computer modeling of mind is the growing interest in models generally and the impact this is having on the role of theory in modern science. It is amazing how dominant theory was in the heyday of logical empiricism. This was caused by the interest in formal logic and the promotion of hypothetico-deductive reasoning as the “scientific method,” the type of reasoning most used by scientists. HD method, however, worked under severe limitations, and these became apparent in lengthy debates over “truth realism,” which in turn led to the notorious division between “realists” and “antirealists” within the philosophy of science movement. The proper focus, of course, should have been on “entity realism,” as Harré pointed out.13 The main tool of entity realism is the development of analogues that can be displayed through iconic models. Simply flipping through the pages of Scientific American will show how the computer simulation of phenomena and the electronic enhancement of data has revolutionized the way in which scientific knowledge is communicated. Models have replaced theory as providing the best insight into discoveries now being made at the frontiers of knowledge. Finally, connected with the demise of mathematical logic as the preferred tool of the philosopher, is recent work on logic as actually employed by scientists throughout history. The case on which I am best informed is Galileo’s appropriated Treatise on Demonstration, actually a commentary on Aristotle’s Posterior Analytics. Galileo had no interest in formal logic, but he was very much concerned with a content or material logic as explained in the Second Analytics. In two books published in 1992, I have shown how he used a logic of discovery and proof, one based on the demonstrative regressus of the Paduan Aristotelians, in turn transmitted to him via the Jesuits at the Col13. In Rom Harré, Varieties of Realism (Oxford: Blackwell, 1986).

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legio Romano, for his most important contributions.14 Similar work on Newton’s Trinity notebook shows that Newton was far from ignorant of Aristotle, and that his later search for “true causes” through a method of resolution and composition likewise bears the imprint of the Posterior Analytics. It is easy to forget that Newton’s Principia laid out the mathematical principles of natural philosophy, that he himself thought he was doing a philosophy of nature, even though he used mathematics for its proper elaboration.

Presenting the Powers Model to Scientists At this point, I would like to make some preliminary remarks about the modeling of forms and powers as relevant to the study of nature, since it is impossible for me to go into full detail in a presentation of this type. I have just mentioned iconic models. These are nothing more than pictorial representations, such as are seen in the Bohr model of the atom or the “space-filling” model of the DNA molecule. We can start with them, but our interest must go beyond pictures to what I term epistemic models or ontic models. These are best exemplified in the powers models I have been developing. An epistemic model uses an analogy or analogous reasoning to convey ideas or concepts that are not directly apparent in sense experience. Similarly, an ontic model displays causal factors or components or principles on which the being of an entity depends, and these likewise are not directly perceived by the senses. It is difficult, of course, to display protomatter and natural form by means of the flow charts or circuit diagrams that are commonly

14. The complete story will be found in six books, whose short titles are: Prelude to Galileo (Boston: Reidel, 1981); Galileo and His Sources (Princeton: Princeton University Press, 1984); Reinterpreting Galileo (Washington, D.C.: Catholic University of America Press, 1986); Galileo, the Jesuits, and the Medieval Aristotle (Hampshire: Variorum, 1991); Galileo’s Logical Treatises (Boston: Kluwer, 1992); and Galileo’s Logic of Discovery and Proof (Boston: Kluwer, 1992).

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displayed in computer graphics. In the present day, however, most people realize that there is more to matter than meets the eye. It has been said that matter has been “dematerialized” in our generation. What this means is that it can no longer be thought of ultimately as little hard chunks of stuff. Better to think of it as the matrix, the underlying principle from which all natural forms emerge, more like an indeterminate or potential energy that grounds every change going on in the universe. To convey this idea, I model it simply as a mathematical point, from which radiate a series of concentric circles that would suggest to scientists an energizing field.15 What that field does is “expand” the protomatter, as it were, and form it into a substance of a particular nature. The field itself stands for the nature or natural form of the particular substance—say, in the realm of the inorganic, the element sodium. In so doing it unifies the basic components of that element and makes of them a functioning whole. At once it is a unifying form, conferring a unity on the components; a specifying form, making those components be and react in a way characteristic of sodium; and a stabilizing form, preserving the identity of that element and maintaining the unity of its components under external influences to the extent possible. Within this field that symbolizes the natural form I arrange a number of blocks or squares; these stand for the powers that are proper to the generic form. For generalizing purposes, I divide natural forms into four types: inorganic, plant, animal, and human. In the case of inorganic natures such as that of sodium, four powers are sufficient, and I arrange them in a symmetrical pattern within the field (labeled NFi , for natural form, inorganic) surrounding the central point (labeled PM, for protomatter).16 In naming the four pow15. For fuller details, see “Nature as Animating,” 619–20, 625–29. 16. This is shown as Fig. 2.6 in The Modeling of Nature; the diagram there is essentially the same as Fig. 2 in “Nature, Human Nature, and Norms for Medical Ethics,” 32, except that the letters SF (for substantial form) in that essay have now been replaced by the letter NF (for natural form). The concept of “natural form” or “nature” seems easier

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ers I simply appropriate the four basic forces found in the physical universe: electromagnetic force, gravitational force, weak force, and strong force. From each of the boxes these powers represent, I show arrows pointing away from the block or toward the block. These indicate the actions and reactions that proceed from or are received into the corresponding power—all transient actions, in philosophical terminology. To this point we have an ontic model or an epistemic model of inorganic natures, ontic in the sense that it shows the principles on which the natures depend, epistemic in the sense that it becomes the means whereby we can know those natures scientifically. It is also a powers model, since powers play the most distinctive role in their understanding. But to grasp the natural form of an inorganic substance, say, sodium, we have to be more specific than that. We have to couple the powers model with an iconic model of the specific substance, here, for example, the Bohr-Sommerfeld model of the sodium atom. This provides a graphic understanding of how sodium enters into chemical combination with other substances and why it is that, when electrically energized, the sodium atom emits the bright yellow light of the sodium vapor lamp. That fleshes out our understanding of the electromagnetic power box and the way it initiates and receives transient activity. Were we modeling the nature of radium, on the other hand, other iconic models might help, such as the liquid-drop or the potential-well model of its nucleus to show the operation of the weak force and the strong force when explaining other properties, such as that element’s radioactivity. Furthermore if we wished to explain the functioning of the DNA molecule in replication, apart from the generic powers model, we might find a different type of iconic model useful, say, the “stick and ball” or the “ribbon” model rather than the “space-filling” model that is commonly seen.

for our contemporaries to comprehend than that of “substantial form,” with all its misunderstandings throughout the history of philosophy.

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Modeling Organic Natures Plant natures are obviously more complex than inorganic natures, since apart from atomic and molecular constituents they are organisms with their own systems and functions for which to account. Aristotle was aware that plant organs exercise three basic powers required for life processes, nutrition, growth, and reproduction. Modern biologists would add to these homeostasis, the power whereby an organism maintains its stability while adjusting to environmental conditions in ways optimal for its survival. These, then, are the four basic vegetative powers that have to be added to the four inorganic powers to provide the eight powers found in a plant form. The generic powers model for a plant also starts with a point source, labeled PM for protomatter, as heretofore, surrounded by an energizing field that radiates from it and constitutes the plant organism, now labeled NFp , for natural form, with the subscript “p” designating plant.17 Within that field, as before, I arrange the powers symmetrically, the inorganic in the lower hemisphere, the organic in the upper, with up and down arrows connecting the two and showing the interchanges between them. These designate immanent activities, those that remain in the plant and are perfective of it. Plants initiate transient activities also, through their homeostasis and reproductive powers, and these too have to be indicated on the powers model. As in the case of inorganic natures, the generic power form is insufficient of itself to model a specific plant nature. To this has to be added iconic models that portray in detail plant structure and functioning as found, for example, in algae, fungi, mosses, and vascular plants. Each of these phyla have different root, stem, and leaf systems, and they use them in various ways for transpiration and reproduction. These have been understood and sketched by biologists for cen17. This appears as Fig. 3.5 in The Modeling of Nature, which is essentially the same as Fig. 3 in “Nature, Human Nature, and Norms for Medical Ethics,” 33, except that the letters SF have again been replaced by the letters NF.

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turies, but with the development of biochemistry in recent decades, much more is now known about metabolism and replication. Graphic modeling techniques make these life processes interesting and intelligible even to those who have little formal education in the sciences that specialize in them. From this the basic idea of a generic powers model and the way it can be used with iconic models to gain an insight into natural forms in the organic and inorganic realms should be clear. As we move up the scale into the animal kingdom, the powers of the natural form become more complex.18 Animals differ from plants basically in their sentience and their movement, and these require four new series of powers, namely, those connected with the outer senses, the inner senses, the sense appetites, and the motor powers these activate. Animal organisms are initiators and receptors of transient action, and at the same time they manifest more immanent activity than plants. There are many more species of animals, of course, than there are of plants. The two major divisions are the invertebrates and the vertebrates, the latter including all the fishes, amphibians, reptiles, birds, and mammals we commonly call animals. All of these have distinctive organ systems for carrying out the activities they share with plants as well as those that are properly their own. Some of the most interesting computer modeling at the moment is that connected with invertebrates, insects we call multipedes, the “smart bugs” that occupy the attention of many cognitive scientists. A recent computer model of the American cockroach maps a large number of neural circuits that are used to account for various aspects of the cockroach’s behavior.19

18. A powers model of an animal nature is shown as Fig. 3.10 in The Modeling of Nature, essentially the same as Fig. 4. in “Nature, Human Nature and Norms for Medical Ethics,” 34, with the letters SF replaced by the letters NF. 19. For details, see R. D. Beer, H. J. Chiel, and L. S. Stirling, “An Artificial Insect,” American Scientist 79 (1991): 444–52.

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Human Nature and Its Perfectibility When we come to human nature, we open out into the traditional areas of philosophical psychology well known to members of this Association, with the many intentional forms that are necessary for understanding cognitional and volitional activities. Here I would mention but one additional type of form as of special interest, the habit, or ἕξις, which can modify a power and make it act like a “second nature.” In more advanced powers models I show these as hexagons added to the boxes or to the activity lines that emanate from them. If we count health among the entitative habits, we have already encountered this modification of a power in the plant and animal kingdoms, something well known to horticulturists and veterinarians, and of course it is the principal concern of the medical profession. But I have rather in mind the intellectual habits and the operational habits that control not the bodily life but the speculative and moral lives of human beings. These are all forms that pertain to the perfectibility of human nature, hexagons that can be added to the basic powers of intellect and will in almost unlimited number.20 When these considerations are taken into account, the full modeling of human nature to flesh out all the powers of the human soul presents itself as a daunting task, one that will not quite fit on a two-dimensional drawing.21 There is an alternative to the twodimensional approach, one that is incorporated into a computer graphics program called AutoCAD. This allows for models or schemata being prepared as layers that can be overlaid one on the other to specify in ever more detail the reality being modeled. In plans for a house, for example, the bottom layer might be the foundation, the

20. Again see the diagrams in “Nature as Animating,” 639, with the surrounding discussion, 638–43. 21. See Fig. 5.1 in The Modeling of Nature, which is essentially the same as Fig. 5 in “Nature, Human Nature, and Norms for Medical Ethics,” 35, except that the letters SF are replaced by the letters NF.

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second the floor plan, the third the plumbing plan, the fourth the wiring plan, the fifth the heating and cooling, and so on. The layers are like transparencies that can be shown individually, or superimposed one on the other, all together or in various combinations. Employing that technique, I would propose that in the modeling of human nature our bottom layer would have to be the basic model of protomatter (PM) being expanded out by natural form (NFh ) as an energizing field. Above that, the second layer would be the powers within that field proper to inorganic forms, the third those proper to plant forms, the fourth those proper to animal forms, all of which are virtually included in the human form. The fifth layer, finally, shows the two powers proper to the human form, those of intellect and will. But we do not have to stop there. We can go on in successive layers to model all the habitual modifications of the human intellect, perhaps splitting these into sublayers for different types of concepts and sciences, then continuing with the virtues and vices that can inform the human will, and so range out into all the matters covered in the logical, natural, ethical, and political disciplines of the present day.

The Primacy of Form Let me now conclude by rejoining briefly the language of the schools. I have talked about many forms in my presentation. What kind of forms have these been? For the most part they have been accidental forms— proper accidents such as powers, other accidents that are more adventitious, such as habits, intentional forms, virtues and vices. We have also talked about substantial forms, which I have more recently been calling natural forms. Are substantial forms difficult to understand? Their co-principle, protomatter, is indeed difficult to understand. One can surely wonder whether it is in any way intelligible. What about the substantial form, the natural form, say, of a horse? It is grasped immediately by anyone who knows what a horse is, who is able to look at a particular animal and say correctly, “That is a horse.”

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That is what Aristotle and Aquinas meant by saying that the proper object of the human intellect is the nature or quiddity that is abstracted from a material thing.22 Even a youth who does this has grasped the nature of a horse in a general way; granted, he does not know as much about that nature as a horse trainer or a veterinarian. In knowing what a horse is, he already knows implicitly what a mammal is, what an animal is, what an organism is, what a substance is, what a being is. In a word, he is at the basic level, the very first layer of my modeling of nature. He has started to be a philosopher and is ready to climb up through the overlays I have described ever so briefly, perhaps to arrive one day at a true science of nature.

22. Aristotle, De anima, III, ch. 7 (431a14–17); Thomas Aquinas, Summa Theologiae Ia, q. 84, art. 7.

Part II

The Scientific Relevance of the Thomistic Tradition

Chapter Three Thomas Aquinas, Galileo, and Einstein

Chapter Three

St. Thomas Aquinas, Galileo, and Einstein

It is frequently said of St. Thomas Aquinas that the man has been lost behind the voluminous quantity of his writing. Commenting further on this literary output of the Common Doctor, one could say that his valuable contributions to the development of physical science have been lost in the great mass of his writing on theology and philosophy. In this vein, it might not be amiss to bring out of the shadows cast by Aquinas’s more famous works a few specimens of his thought on the subject of scientific knowledge, contributions that, had they been those of a lesser genius, might have been appreciated the more by assessors of the medieval scientific tradition. To those who are friends and admirers of St. Thomas, no apology is needed for treating the question of his basic theory of physical knowledge. But even should the reader make no commitment whatsoever to Thomism, it could well be profitable to reconsider some of the perennial problems of the universe in the light of Aquinas’s conception of physical science. Such a consideration need not be anachronistic. As Burtt has pointed out in his Metaphysical Foundations of Modern Science, every age has its unconscious presuppositions, and these can sometimes be brought to light by setting off current views against those of an earlier period, when prevailing notions were not

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so commonly entertained.1 And if every age has its hidden presuppositions, it is also true that every age has its problems—not unconnected, possibly, with these same suppositions. We in America are now very much preoccupied with the study of the physical universe: on the surface, great progress is being made in science and technology, but at the heart of the matter, when scientists ask how much is really known about the world in which we live, there is a gnawing doubt that makes itself increasingly felt about our ability ever to reach any definitive answers. It is on such a problem of the validity of scientific knowledge that Thomas Aquinas may have something worthwhile to offer to the modern mind, and this proposal will therefore be the burden of our study.

St. Thomas Aquinas (1225–1274) The intellectual atmosphere that Aquinas breathed at the University of Paris in the mid-thirteenth century was not sympathetic to natural science; in fact, it was markedly hostile to the influx of Aristotelian and Arabian thought into Western Europe—an influx that brought with it much of the scientific learning of the ancient world. This attitude of hostility at Paris, however, was not apparent at the other great center of studies in medieval Christendom, Oxford University. There the discovery of Aristotle’s logical works, and particularly the translation of the Posterior Analytics (with commentary) by Robert Grosseteste, Bishop of Lincoln (1175–1253), had stimulated great interest in a type of mathematical physics which accented studies in optical science.2 This had resulted in what Baeumker has called a “metaphysics of light,” a philosophy immediately put to the service of theology to develop the Christian Platonism of the Oxford school.3 What is of 1. E. A. Burtt, Metaphysical Foundations of Modern Science (London: Routledge, 1932), 15–17. 2. A. C. Crombie, Robert Grosseteste and the Origins of Experimental Science (Oxford: Clarendon Press, 1953), 91–134. 3. C. Baeumker, “Der Platonismus im Mittelalter,” in Studien und Charakteristiken

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more importance, however, in this scientific revival at Oxford was its insistence on the role of mathematics in physical proof. In this school, a pure mathematical structure was commonly conceived as objectively existing in things, before their physical properties, and giving the only adequate explanation of observed reality. Possibly through Roger Bacon, the influence of Grosseteste’s work was gradually felt on the continent, and provoked a decided reaction from the pen of St. Albert the Great (1206–1280), the teacher of St. Thomas Aquinas. Albert himself, unique among the Paris Masters, had been sympathetic to the influx of Aristotelian thought, had done extensive observational and experimental work in biology, meteorology and alchemy, and had reconstructed a physical theory from Aristotle’s Physics that was opposed to the mathematical realism of the Oxford school.4 The young Aquinas then built upon Albert’s foundations, and elaborated this theory that was primarily physical, but at the same time allowed for a legitimate use of mathematics in obtaining strict physical explanation or proof.5 For Aquinas, as for Albert, mathematical structure is not imposed on reality by the mind, but rather is abstracted from reality by a mental process that leaves aside all the irregularities of matter and the flux of movement and time. More basic than this mathematical structure is the physical nature of the reality studied, which is determined to express itself in a certain figure—by which, for example, we can easily recognize a horse, and distinguish it from a cow. The quantitative characteristics that are thus expressive of a type are not themselves mathematical entities, but rather are physical ones, although originative sources of the idealized static structure studied by the mathematician. Thus, in Aquinas’s view, the insight afforded by mathematics zur Geschichte der Philosophie insbesondere des Mittelalters, Beiträge zur Geschichte der Philosophie des Mittelalters, bd. 25, 1–2 (Münster-i-W.: Aschendorff, 1927), 160 ff. 4. J. A. Weisheipl, OP, “Albertus Magnus and the Oxford Platonists,” Proceedings of the American Catholic Philosophical Association 32 (1958): 114–189. 5. J. A. Weisheipl, OP, The Development of Physical Theory in the Middle Ages (London: Sheed & Ward, 1959), 27–62.

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is not deeper—or more “divine,” as the Platonists would have it—but actually is more superficial than a physical insight. As a consequence, explanation through mathematics does not explain the physical nature, but it does accurately describe that nature, and it can help in discovering a physical explanation or proof.6 The help that mathematics gives to the physicist was conceived by Aquinas as being of two kinds, one which functions at the level of hypothesis to suggest possible physical explanations, the other which functions conjointly with physical reasoning to give conclusive explanation or proof.7 An example of the first would be the Thomistic evaluation of Ptolemy’s explanation of the motion of the heavens through eccentrics and epicycles. Viewed mathematically, Aquinas noted, the observed appearances of the stars result “either from the motion of the object seen or from the motion of the observer, . . . it makes no difference which is moving.”8 But as a physical explanation he showed considerable reserve towards the Ptolemaic hypotheses, noting that while they do account for the stellar appearances, “we must not say that they are thereby proved to be facts, because perhaps it would be possible to explain the apparent movements of the stars by some other method which men have not yet thought out.”9 His whole treatment of astronomical and meteorological problems, in fact, seems aimed at correcting a naive mathematicism among medieval Aristotelians, for he points out that Aristotle, in dealing with the heavenly spheres, had mistaken a suppositional theory for established fact.10 He himself is at pains to elaborate the reasons why we cannot have certain judgments about the heavenly bodies;11 yet, he observes, it is not stupid or necessarily precipitate to venture an ex6. See Thomas Aquinas, In I de Caelo, lect. 1, n. 2, and lect. 3, n. 6; In II Phys., lect. 3; Summa Theologiae, I, q. 1, a. 1, ad 2. 7. See Summa Theologiae, I, q. 32, a. 1, ad 2; In II Phys., lect. 3, n. 9. 8. In II de Caelo, lect. II, n. 2, and lect. 12, n. 4. 9. In II de Caelo, lect. 17, n. 2. 10. In II de Caelo, lect. 17, n. 2. 11. In II de Caelo, lect. 4, n. 3

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planation, for he holds that a theory or supposition that does not conflict with the facts is far better than no explanation at all.12 In addition to this first, or hypothetical use of mathematics in seeking a possible explanation, Aquinas also conceived of mathematics as functioning directly in physical argument to furnish a conclusive explanation or proof.13 This too can best be illustrated by an example.14 In discussing the shape of the earth, he notes that the latter can be proved to be a sphere merely by an analysis of measurements made on its surface—essentially a mathematical proof.15 But he regards as more conclusive for the physicist a proof which arises not simply from a mathematical description of the earth’s surface, but which leads to a knowledge of the physical causes that make the earth to be a sphere. Thus he observes, “all gravitating bodies . . . approach the earth at the same angle, that is, at a right angle . . . and not in parallel lines.”16 This universal mode of gravitation “is what makes the earth to be spherical by nature,” he says, because the spherical shape alone can satisfy the uniform tendency of all parts to a common center of gravity.17 “If the earth were naturally flat, as some have said,” he continues, “then bodies would not gravitate everywhere towards the earth at the same angle.”18 It should be noted in this proof that the physical cause Aquinas assigns need not make the earth a perfect sphere—“irregularities such as mountains and valleys arise,” he concedes, although “not of notable dimensions compared with those of the earth,” and he attributes them to “some other incidental cause.”19 Thus pure or perfect mathematical shape, for Aquinas, does not exist 12. In II de Caelo, lect. 7, nn. 4–5; In I Meteorologicorum, lect. 11, n. 1. 13. Thomas Aquinas, In I Post. Anal., lect. 25, nn. 5–6. 14. For other examples, together with some applications to modern science, see my “Some Demonstrations in the Science of Nature,” The Thomist Reader 1957 (Washington, D.C.: The Thomist Press, 1957), 90–118. 15. In II de Caelo, lect. 28, n. 4. 16. In II de Caelo, lect. 28, n. 1. 17. In II de Caelo, lect. 28, n. 1. 18. In II de Caelo, lect. 28, n. 1. 19. In II de Caelo, lect. 28, n. 1.

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in physical reality: it is only the human mind, abstracting from material irregularities such as mountains and valleys, that can conceive of the earth as a perfect sphere.20 But the earth does have a natural or physical shape which is approximately spherical, and this shape can reveal to the inquiring mind the physical reason which makes the earth to have this shape in the first place.21 Space does not permit even a sketch of the historical consequences of this theory of physical proof developed by Albert and Aquinas. It is indisputable, however, that this theory made clear, at a critical period of medieval thought, the distinction between hypothetical explanation and proven fact, while allowing for a legitimate use of mathematics in both types of reasoning. To this one might add that some recently edited texts can be used to argue to the existence of a “Dominican school” in optical science, beginning with encyclopedic collections of data by Thomas of Cantimpré, Vincent of Beauvais and Albert the Great, developing through the theoretical speculations of Thomas Aquinas, John of Paris and Peter of Alvernia, and culminating in the brilliant experimental researches and physico-mathematical theories of Theodoric of Freiburg.22 The historical import is not insignificant: in less than a century, this line of thought, quite independent of the Oxford school, furnished the first correct fundamental theory of the rainbow—and this more than three hundred years before the publication of Descartes’s Discours de la Methode and Les Meteores, where basically the same explanation of the rainbow is cited as one of the brilliant achievements of the new Cartesian methodology.23 20. In II Phys., lect. 3, nn. 4–6. 21. Summa Theologiae, I, q. 1, a. 1, ad 2; In I de Caelo, lect. 3, n. 6. 22. See my The Scientific Methodology of Theodoric of Freiburg, Studia Friburgensia, no. 26 (Fribourg: University Press, 1959), 132–249. Newly edited texts are contained in Appendix III, 305–76. 23. The full title of Descartes’s work on methodology reads: Discours de la Méthode pour bien conduire sa raison, et chercher la vérité dans les sciences. Plus la Dioptrique, les Météores, et la Géométrie, qui sont des essais de cette Méthode (Leyde: de l’imprimerie de Jan Maire, 1637). The explicit statement from Les Météores is contained in Descartes’s Oeuvres, ed. C. Adam and P. Tannery, vol. 6 (Paris: J. Vrin, 1897–1910), 281.

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Galileo Galilei (1564–1642) While not belittling the importance of Descartes’s influence on modern thought, we may turn now to one of his contemporaries, Galileo Galilei, to whom the accolade is commonly given for having procured the “downfall of Aristotle” and the beginning of a new era in science. Some might quibble on the phrase “downfall of Aristotle” and urge that this was more a downfall of a caricature of Aristotle drawn by third-rate scholastics,24 but without gainsaying the point, the effect was pretty much as popularly conceived. One of Galileo’s admirers, Fr. Paolo Sarpi, registered a not uncommon reaction when he said: “To give us the science of motion God and Nature have joined hands and created the intellect of Galileo.”25 In our own day, the popular image is that of an indefatigable experimenter climbing the leaning tower of Pisa to put the Aristotelians to rout with his measurements of falling bodies.26 Recent studies point more significantly to the Renaissance reaction to Galileo’s Message of the Stars. Thus Koyré summarizes: Mountains on the moon, new ‘planets’ in the sky, new fixed stars in tremendous numbers, things that no human eye had ever seen, and no human mind conceived before. And not only this . . . also the description of an astonishing invention . . . the first scientific instrument, the telescope, which made all these discoveries and enabled Galileo to transcend the limitation imposed by nature—or by God—on human senses and human knowledge.27

The experimental work of Galileo might easily—though falsely— be interpreted as the beginning of modern scientific method, with its accent on postulational procedures subsequently verified by experimental proof. Actually, Galileo’s method was more closely patterned 24. See G. de Santillana, The Crime of Galileo (Chicago: University of Chicago Press, 1955), 24, 56, 69. 25. Cited by Burtt, Metaphysical Foundations of Modern Science, 74. 26. But see L. Cooper, Aristotle, Galileo & the Tower of Pisa (New York: Cornell University Press, 1935); also E. A. Moody, “Galileo and Avempace: The Dynamics of the Leaning Tower Experiment,” Journal of the History of Ideas 12 (1951): 163–93, 375–422. 27. A. Koyré, From the Closed World to the Infinite Universe (New York: Harper, 1957), 90.

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on that of the late Aristotelians of the Paduan school,28 and its most significant aspect was not its insistence on experiment, but rather on the fact that “the book of nature” is written only in the language of mathematics.29 “This book is written in the mathematical language,” wrote Galileo, “and the symbols are triangles, circles, and other geometrical figures, without whose help it is impossible to comprehend a single word of it; without which one wanders in vain through a dark labyrinth.”30 Galileo was quite convinced of the absolute truth of the heliocentric theory, maintaining that it was not merely a possible explanation, a “saving of the appearances,” as Osiander had indicated in his preface to Copernicus’s work,31 but rather that it expressed a certain truth with which one could even contest traditional interpretations of Sacred Scripture. “Although [a theory that saves the appearances] satisfies an astronomer merely arithmetical,” he said, “it does not afford satisfaction or content to the astronomer philosophical.”32 His own metaphysical option, according to Burtt, was for a much refined Platonism that was actually a strict mathematical realism33—one could almost call it a revival of the Pythagorean doctrine of twenty centuries previous.34 Experiments had no probative value for Galileo; they were meant to appeal to the popular mind—those who knew mathematics really had no need of them. But the popular mind also needed convincing, and here Galileo’s genius for stirring 28. See J. H. Randall, Jr., “The Development of Scientific Method in the School at Padua,” Journal of the History of Ideas 1 (1940): 177–206; P. R. Wiener, “The Tradition Behind Galileo’s Methodology,” Osiris 1 (1936): 733 ff. 29. See, for example, J. Collins, A History of Modem European Philosophy (Milwaukee: Bruce Pub, 1954), 79–81. 30. Galileo, ll Saggiatore (Firenze: Società Editrice Fiorentina, 1842), 171. 31. For a detailed examination of the relations between Copernicus and Galileo, see P. Conway, “Aristotle, Copernicus and Galileo,” New Scholasticism 23 (1949): 38–61, 129–46. 32. Galileo, Dialogue on the Great World Systems, Third Day, ed. G. de Santillana (Chicago: University of Chicago Press, 1953), 349–50. 33. Burtt, Metaphysical Foundations of Modern Science, 82, 84; A. Koyré, “Galileo and Plato,” Journal of the History of Ideas 4 (1943): 400–428. 34. See G. de Santillana, The Crime of Galileo, 69.

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up trouble came to the fore. His wit and sarcasm in controversy are well known, and on hearing this brief excerpt from a letter, one can imagine the hot arguments he provoked. He writes: Oh, my dear Kepler, how I wish that we could have one hearty laugh together! Here at Padua is the principal professor of philosophy, whom I have repeatedly and urgently requested to look at the moon and planets through my telescope, which he pertinaciously refuses to do. Why are you not here? What shouts of laughter we should have at this glorious folly! And to hear the professor of philosophy at Pisa laboring before the Grand Duke with logical arguments, as if with magical incantations, to charm the new planets out of the sky!35

In sober fact, Galileo Galilei never did prove that the earth went around the sun, and not vice versa. Conclusive proof of the type Aquinas would have sanctioned, such as is found now, for instance, in our astronomy textbooks, had to wait two more centuries for the contributions of Foucault and Bessel.36 Galileo’s real “crime” had nothing to do with revealed religion: it consisted merely in this, that he saw proof too easily, and thus obscured (in his own mind, at least) the distinction between hypothetical explanation and proven fact already well known to Aquinas. Yet there was much that was good in his work—he had offered new evidence that should have been taken into account by the philosophers of his day. As de Santillana remarks, “Had there been in Rome, at the time of the first crisis of 1616, a youthful Aquinas . . . instead of an aged Bellarmine,” history might have been written differently.37 But “there was no Aquinas,”38 and well known is the unfortunate stand taken by those who were in Rome, to bring about what history will always regard as a tragic ending in a most unsatisfactory case. 35. Letter to Kepler, 1610; cited by Burtt, Metaphysical Foundations of Modern Science, 77. 36. See A. C. Crombie, “Galileo’s ‘Dialogues Concerning the Two Principal Systems of the World,’ ” Dominican Studies 3 (1950): 105–38. 37. Santillana, The Crime of Galileo, ix. 38. Santillana, The Crime of Galileo, ix.

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Albert Einstein (1879–1955) Crombie has suggested that the great genius of Albert Einstein, working three centuries after Galileo to elaborate the theory of relativity, consisted in his breaking away from the spell under which the great Italian had put mathematical physics from its inception. “Einstein was able to advance the theory of relativity,” Crombie writes, “because he acted on the principle that the object of physical science is to ‘save the appearances’ by mathematical abstractions postulated for no other purpose than to ‘save the appearances.’ ”39 Einstein seems to have had little hope of penetrating to the reality behind his equations, and there can be little doubt that recent revolutions in physics, traceable in large measure to Einstein, show a decided break with the Galilean concept of proof. In fact, with Einstein ends the naive optimism of a classical physics that saw the book of nature written in the language of mathematics.40 Proficiency in mathematics, it is true, enabled this modern scientist to achieve brilliant successes in theoretical physics, but the more he worked, the more he doubted the exact correspondence of pure mathematics to physical reality. “As far as the laws of mathematics refer to reality,” he says, “they are not certain; and as far as they are certain, they do not refer to reality.”41 In fact, Einstein would go even further; for him, fundamental principles cannot be “abstracted” from sensory experience—they are “free inventions of the human intellect.”42 Far from subscribing to the strict mathematical realism of Galileo, he oscillates between positivism and idealism, while ever leaving a provisional cast to his conclusions.43 “Our no39. A. C. Crombie, Augustine to Galileo (London: Falcon, 1952), 328 (italics added). 40. In writing this, we are aware that Niels Bohr and the Copenhagen school are even more radical in their renunciation of classical physics than Einstein, but the latter’s position is sufficiently representative for our purposes. 41. A. Einstein, Geometrie und Erfahrung, cited in Albert Einstein, Philosopher-Scientist, in Library of Living Philosophers, vol. 7 (Evanston: Library of Living Philosophers, 1949), 380. 42. Herbert Spencer Lecture, 1933, cited in Albert Einstein, Philosopher-Scientist, 273. 43. See P. G. Frank, “Einstein, Mach and Logical Positivism,” V. F. Lenzen, “Einstein’s

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tions of physical reality can never be final,” he states. “We must always be ready to change those notions . . . in order to do justice to perceived facts in the most logically perfect way.”44 Compared to the physical views of Aquinas and Galileo, those of Einstein stand in proper relief. Seven centuries ago, Aquinas saw the possibility of a mathematical physics that could provide both provisional explanation and conclusive proof, although he had no illusions about the difficulties involved in unveiling the ultimate secrets of the physical universe.45 Three centuries ago, flushed with his dramatic conquest over the popular mind, Galileo saw proof too easily in the mathematics he had learned to read in the book of nature; in his view, conclusive proof was quickly had—all one need do was study his new science of motion, and the Ptolemaic-Copernican controversy would perforce come to an end. In our own day, Einstein went to the other extreme, for where Galileo saw proof as too easy, he saw it as too difficult—hence an essential relativism in his physical theory which permits no final answers about the physical universe. Aquinas would look for the evidence of Bessel and Foucault to decide the Copernican controversy; Galileo would say that the mathematical simplicity of his laws had already decided it; Einstein would say that his general theory of relativity had made it forever undecidable.46

Theory of Knowledge,” and H. Margenau, “Einstein’s Conception of Reality,” in Albert Einstein, Philosopher-Scientist, 269–86, 355–84, 243–68. 44. “Clerk Maxwell’s Influence on the Idea of Physical Reality,” cited in Albert Einstein, Philosopher-Scientist, 248. 45. See Thomas Aquinas, In I Meteorologicorum, lect. 1, n. 9. 46. “The struggle, so violent in the early days of science, between the views of Ptolemy and Copernicus would then be quite meaningless. Either CS [coordinate system] could be used with equal justification. The two sentences, ‘the sun is at rest and the earth moves,’ or ‘the sun moves and the earth is at rest,’ would simply mean two different conventions concerning two different CS,” A. Einstein and L. Infeld, The Evolution of Physics (New York: Simon and Schuster, 1942), 224.

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The Problem This brings us to the problem that is vexing modern science, to the solution of which the physical theory of Aquinas might be able to register a contribution. In the popular mind, science is making great strides forward, finding out new truths every day that undermine traditional philosophies and even religious beliefs, supplying definitive answers to questions that have plagued men’s minds since the dawn of civilization. But within the scientific fraternity itself, there is no such optimism—at least not so far as the question of conclusive proof is concerned. “Proof,” writes Eddington, “is an idol before whom the pure mathematician tortures himself. In physics we are generally content to sacrifice before the lesser shrine of plausibility.”47 Relativity and quantum theories are now the standards against which scientific achievement is measured. One is not surprised that some now hold that whether the earth goes around the sun or vice versa depends strictly on one’s point of view, and cannot be proved one way or another. Not long ago, a methodologist told the writer that it was merely a theory that the earth is round! Today the whole world is talking of “molecules” and “atoms” and “electrons” and “cosmic rays”; even highschool children can tell us of “evolving galaxies” and the “expanding universe.” Has science proved that such things exist? Or are they merely “free inventions of the human mind”? Is the hard core of scientific fact softer than we think? Or is it possibly even an empty shell? Einstein, we may presume, would want to disabuse the modern mind of its confidence in the permanent achievements of science. Galileo, no doubt, would be tremendously surprised at the state of affairs that has arisen in the science that he fathered, but one may surmise that he would still champion the absolute power of mathematics to give certain truth. Aquinas, we can be sure, would temper the optimism of Galileo, but—realist that he was—he would also tem-

47. A. S. Eddington, The Nature of the Physical World (New York: Macmillan, 1928), 337.

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per the pessimism of Einstein by bridging the gap between science and common sense. While denying that mathematics is the skeleton key that opens all the doors of knowledge, he would say that it has a proper role to play in physical research, that it can lead to conclusive physical proof, that some final answers can be given about the world in which we live. Three divergent answers to a perennial question about the physical universe. Which is correct? While recognizing that the latter question would be regarded as unanswerable (if not meaningless, in Wittgenstein’s sense) by some philosophers of science, and while conceding that the extreme polarity between the positions of Galileo and Einstein is more by way of suggestion than by way of explicit commitment in the writings of these scientists, we should like to propose a somewhat novel evaluation of the three possible alternatives. It is this, namely, that Aquinas’s answer—the teaching of the analytical school to the contrary—is still the one implicitly subscribed to by the practicing scientist, and that the essential contribution of Einstein is to cancel out the excessive mathematical realism of Galileo, while still leaving open the possibility of a type of physical certainty and proof as conceived by Thomas Aquinas.

A Thomistic Proposal The justification for this view may perhaps be seen if we analyze the scientific evidence commonly adduced to prove (1) that the earth rotates on its axis, and (2) that its shape is approximately that of an oblate spheroid. In the interests of rigor, and to facilitate discussion of the central issue, we shall frame both arguments in the form of a syllogism, then answer an objection that is commonly encountered against each argument, and with that draw some inferences about the current status of physical proof in modern science. The first argument may be stated as follows:

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Chapter Three A body on which a freely swinging pendulum deviates at the rate of one revolution per twenty-four hours at the poles, decreasing according to the sine of the latitude to zero deviation at the equator is rotating on its polar axis once every twenty-four hours. Therefore the earth is rotating on its polar axis once every twentyfour hours.

The second argument then reads: A body on which a freely swinging pendulum of fixed length has periods of oscillation which increase slightly with increasing latitude from the equator to both poles is an oblate spheroid slightly flattened at the poles. Therefore the earth is an oblate spheroid slightly flattened at the poles (and here we add parenthetically—although this does not follow logically—the flattening being caused by the centrifugal force of its daily rotation).

Here, then, are two demonstrations which conclude to some predication about the earth, namely, (1) that it is an oblate spheroid, and (2) that it rotates on its axis of symmetry once every twenty-four hours, both arguments using as the middle term some aspect of the behavior of a pendulum on the earth’s surface, which is discovered to be caused by the shape and rotation of the earth itself. Some will object against the second argument—the one concluding to the shape of the earth—that this was regarded as valid in the pre-Einstein period, when it was thought that Euclidean geometry was uniquely applicable to the physical universe. But in the present day, when non-Euclidean geometries have proved to be remarkably fruitful in explaining physical phenomena, one cannot say for sure that the earth is a sphere or an oblate spheroid; in another geometry it might be another mathematical figure, and thus the argument no longer truly demonstrates. To this objection we answer that, if relativity theory has shown anything, it has shown that the geometry used by the physicist to describe the shape of the earth is basically immaterial. For dimensions as small as those of the earth, it is of no physical importance

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whatsoever whether the geometry is Euclidean, or Riemannian, or Lobatchewskian. But the very objection reveals one thing that is quite important, namely, that the objector is a mathematical realist who conceives pure mathematical form as objectively existing in, and determining, the universe to a particular geometry. As has been shown earlier, this is not the Thomistic concept: physical quantity is much too irregular, it is much too perturbed by physical factors—such as matter and motion and time, and their means of measurement—to yield pure geometrical form, except through a process of mathematical abstraction. Thus, when the physicist says that the earth is an oblate spheroid, just as he prescinds from the mountains and valleys and other physical irregularities, so he prescinds from the slight differences associated with alternative pure geometries, to say something that is physically meaningful about the shape of the earth. The first argument also seems to be vulnerable—this time to an objection drawn from the general theory of relativity. We have argued that it is possible to demonstrate that the earth is actually rotating on its axis once every twenty-four hours. Now Einstein, and before him the great German physicist, Ernst Mach—who undoubtedly gave inspiration to Einstein’s new theories—have held that it is impossible to detect an absolute rotation in the universe. Thus they would argue that the cause assigned above for the deviation of the pendulum on the earth’s surface (or for the bulge at the equator) need not be the rotation of the earth: the same effect can be correlated mathematically with the apparent motion of the “fixed” stars, and thus one cannot be absolutely sure that the earth’s rotation is causing the pendulum phenomena or the bulge at the center, since these might be caused by other forces connected with the diurnal motion of the stars.48 A Thomistic answer to this difficulty is suggested by that of the

48. For a fuller statement of this position, see H. Reichenbach, Modern Philosophy of Science (New York: Routledge, 1959), 12.

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English astronomer and commentator on general relativity theory, Sir A. S. Eddington, who writes in this connection: I doubt whether anyone will persuade himself that the stars have anything to do with the phenomenon. We do not believe that if the heavenly bodies were all annihilated it would upset the gyrocompass. In any case, precise calculation shows that the centrifugal force could not be produced by the motion of the stars, so far as they are known.49

As for the search for some unknown force that might explain the phenomenon, Eddington becomes more caustic: As we go further into space to look for a cause, the centrifugal force becomes greater and greater, so that the more we defer the debt the heavier the payment demanded in the end. Our present theory is like the debtor who does not mind how big an obligation accumulates, satisfied that he can always put off the payment. It chases the cause away to infinity, content that the laws of nature . . . are satisfied all the way.50

In this matter, Thomas Aquinas, we may be reasonably sure, would be content with a physical explanation of the motion of the pendulum or of the bulge at the equator in terms of known causes, and would be quite unhappy with an explanation, or a methodology, that would remove a hypothetical cause to infinity. As to the mathematical correlation with the fixed stars mentioned by Mach and Einstein, this would not disturb him: he would say, as has already been pointed out, that mathematically it makes no difference whether either one, the earth or the fixed stars, is conceived as moving. But once he saw the physical evidence available today to show that the plane of oscillation of a pendulum is independent of the motion of its support and is determined uniquely by its point of suspension, the center of gravity of its bob and the center of gravity of the local region, or once he convinced himself that there are centrifugal forces connected with every rotation that we initiate, he would look no further for a causal 49. A. S. Eddington, Space, Time and Gravitation (Cambridge: Cambridge University Press, 1920), 158. 50. Eddington, Space, Time and Gravitation, 158.

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explanation in the remote depths of space to account for the deviation of a pendulum on the earth’s surface, or for the observed bulge in the earth’s contour at the equator. He would conclude, as do most modern scientists, that these are caused by the rotation of the earth, and that the earth therefore is actually spinning on its axis.51 This conclusion, it should be noted, does not commit the Thomist to the Newtonian conception of a subsistent absolute space (or absolute time) in which such spinning motion is executed. The notion of absolute space is again an extreme of mathematical realism which attributes static, extra-mental existence to an extension that has been abstracted by the mind from bodies in motion. Space, for St. Thomas, does not exist apart from bodies that are extended and in motion; itself based on the relation of distance between bodies, it is rather a relative thing, not an absolute. More properly, it is a mathematical concept that abstracts from matter and motion, and as such is conceived statically by us. This need not, therefore, be interpreted to mean that it also exists statically outside the mind as an independent subsistent reality.52 A similar observation might be made about the existence of privileged frames of reference or inertial systems which correspond, in the language of relativity, to the absolute space of Newton. Motions within the solar system—or in any local region, for that matter—can be investigated without referring them, in a larger context, to the motions of other systems. The difficulty arises only when space (or the space-time continuum) is hypostasized to be a subsistent background, sometimes conceived physically as an “aether,” against which 51. This argument can be stated more technically by referring the motion of the pendulum to the local inertial axes of the Copernican coordinate system. Thus our analysis accords with the view of Whittaker, recently taken up by Polanyi: “Sir Edmund Whittaker (‘Obituary Notice on Einstein,’ Biogr. Mem. Royal Society [1955]: 48) points out that, contrary to widespread opinion, the physical significance of Copernicanism is not impaired by relativity. For the Copernican axes are inertial, while the Ptolemaic are not, and the earth rotates with respect to the local inertial axes,” M. Polanyi, Personal Knowledge (Chicago: University of Chicago Press, 1958), 147n1. 52. See J. A. Weisheipl, “Space and Gravitation,” New Scholasticism 29 (1955): 175–223.

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the frames of reference of various systems are actually moving. Operating with such a supposition, the question can be raised as to which system is “really” at rest, or what is the privileged frame of reference in terms of which “absolute” motion and rest in the universe can be detected. It is to the merit of Einstein that his theories of relativity make clear how such a question, if raised, is unanswerable in terms of the data available to the physicist in any system. The Thomistic position would rather seem to be that the question should not be asked in the first place, because of the uncritical supposition on which it is based.

Physical Proof It is interesting that the view of St. Thomas that has been urged in this paper, namely, that there can be some “final answers” in physical science, is once again finding support from scientists. Heisenberg, for example, who seemed to shake traditional thought to its foundations when he enunciated his “principle of uncertainty,” has written in a recent work: With respect to the finality of the results, we must remind the reader that in the realm of the exact sciences there have always been final solutions for certain limited domains of experience. Thus, for instance, the questions posed by Newton’s concept of mechanics found an answer valid for all time in Newton’s law and in its mathematical consequences. . . . In the exact sciences the word ‘final’ obviously means that there are always self-contained, mathematically representable, systems of concepts and laws applicable to certain realms of experience, in which realms they are always valid for the entire cosmos and cannot be changed or improved. Obviously, however, we cannot expect these concepts and laws to be suitable for the subsequent description of new realms of experience.53

With this we think St. Thomas would heartily agree. In a very real sense, in physical research one never knows what the morrow will 53. W. Heisenberg, The Physicist’s Conception of Nature (London: Hutchinson, 1958), trans. A. J. Pomerans of Das Naturbild der heutigin Physik (Hamburg: Rowohlt, 1955), 26–27 (italics added).

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bring, but the scientist can know that if he does his work well, and does not read into his results more than the evidence warrants, he can gain new knowledge without thereby destroying the science he has previously acquired. This view, we would maintain, is the one implicitly held by the practicing scientist.54 Yet there remains the difficulty, continually raised by logical empiricists, that such a position—no matter how commonly it may be accepted—is still naive and a priori, that it does not make sufficient allowance for future discoveries, and in effect represents a nineteenth-century attitude of mind which is unprepared for revolutionary developments that may further advance scientific thought. They would argue that to maintain anything as certain or final is to close the mind to new knowledge, that the very possibility of someone’s making a new discovery forces the scientist to be hesitant about ever saying the “last word,” or to despair even of proposing a “final answer” in the area of his investigations. Aquinas’s concept of physical proof, surprisingly enough, is not vulnerable to this objection, and in fact might even be said to have anticipated difficulties of this type that await anyone who would claim too facile a “final explanation” of physical phenomena. For one thing, St. Thomas insisted that the logical procedure that most characterizes physical science is not a priori, but is rather a posteriori, based on a patient study of the world of nature, not starting with any preconceived knowledge of essences, but rather arguing from effect to 54. It has also been stated explicitly by Oppenheimer, in his third Reich lecture, as reported by Hall: “In its [science’s] progress since 1800 the later discoveries have always embraced the earlier: Newton was not proved wrong by Einstein, nor Lavoisier by Rutherford. The formulation of a scientific proposition may be modified, and limitations to its applicability recognized, without affecting its propriety in the context to which it was originally found appropriate. We do not need sledge-hammers to crack nuts; we do not need the Principle of Indeterminacy in calculating the future position of the moon: ‘the old knowledge, as the very means of coming upon the new, must in its old realm be left intact; only when we have left that realm can it be transcended’ (J. R. Oppenheimer),” A. R. Hall, The Scientific Revolution, 1500–1800: The Formation of the Modern Scientific Attitude (Boston: Beacon Press, 1954), xiii.

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cause solely on the basis of observed facts.55 In this matter, he was insistent that a basic and irreconcilable difference exists between the canons for physical proof and those for mathematical proof. He was aware that the mathematician could have absolute certitude, and that the very abstractness and necessity of his subject matter permit him to proceed a priori and with the most exacting standards of proof. The certitude he ascribed to physical science, on the other hand, was somewhat circumscribed: he referred to it as a “suppositional certitude,” and gave detailed instructions for attaining it when working with the contingent or non-necessary matter of the physical world.56 His methodological precisions need not concern us here, but certainly one of its suppositions was entirely consistent with Heisenberg’s proviso, namely, that results are valid only for the realm of experience from which they are derived. Thomas, as a matter of fact, would go even further than Heisenberg, and maintain that, even within this realm, final explanations can only be expected, and are only valid, for events that happen “regularly or for the most part,” for these alone are sufficient to manifest some type of dependence on the antecedents which produce them, and thus induce a causal necessity into the proof.57 Implicit in Aquinas’s treatment is also allowance for the acquisition of new knowledge, either by way of refinement within an existing realm of experience, or by revolutionary extension to completely new realms, and both without jeopardizing explanations that have already been conclusively established in science. An example of the first type is the proof already discussed for the sphericity of the earth. Thomas argues that the earth is approximately a sphere because this shape is caused by the uniform action of the gravitational forces of 55. See In II de Anima, lect. 3, n. 245; for a full treatment, see M. A. Glutz, C.P., The Manner of Demonstrating in Natural Philosophy (River Forest, IL: Dissertation, 1956), 84–102. 56. Thomas Aquinas, In II Post Anal., lect. 7, nn. 2–3; In II Phys., lect. 15, nn. 2, 5 and 6. 57. The details of such a methodology, as applied to the late medieval theory of the rainbow, will be found in my The Scientific Methodology of Theodoric of Freiburg, 237–45.

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its components; at the same time, he admits that other causes are at work that further modify this shape from that of a perfect sphere. In his day, science had not advanced sufficiently to detect the earth’s rotation or the resultant bulge at the equator; yet this advance in knowledge does not nullify his reasoning or his basic explanation. Modern science holds that the earth is an oblate spheroid, and assigns this modification of the spherical shape to rotational forces which are superadded to the gravitational forces, but which do not replace them. And both Aquinas and the modern scientist would presumably be open-minded to the discovery of further irregularities in the observed shape of the earth’s surface, which might be traceable to yet unknown causes still awaiting our investigation, but would not force us to reopen our minds again to the possibility that the earth is flat. With regard to revolutionary knowledge applicable to completely new realms of experience, we can only surmise how Aquinas would proceed because of the very rudimentary state of science in his day. A not too far-fetched example may perhaps be taken from his generalization, derived from empirical data, that material objects tend in a straight line towards a center of gravity, elaborated mathematically by Newton, over four centuries later, into the law of universal gravitational attraction. It is possible, on the basis of this generalization, to say that all matter is ponderable or massive, a statement not inconsistent with the definition frequently found in science textbooks to the effect that matter is what ever has mass and occupies space. Yet such a definition does not close the physicist’s mind to other possibilities: in theoretical cosmology, for instance, he will speculate about “anti­gravitation” as accounting for the recession of galaxies, while in fundamental particle theory he will speak of “anti-matter” (or antiterrestrial matter) as having properties radically different from the matter we observe macroscopically. The very fact that he assigns new terms to such entities is evidence that he regards the phenomena on which their existence is based as constituting, in Heisenberg’s phrase, a “new realm of experience,” about which he can freely speculate,

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and for which he can even seek hyper-generalizations, without relinquishing a single theorem in classical mechanics. And St. Thomas’s willingness to countenance such a procedure is at least implicit in his recognition that celestial matter might be radically different from terrestrial matter, while allowing for some common features and a diversity in the laws applicable to each—although there is no doubt that he was mistaken on many details clarified by subsequent investigators. It would thus seem that the essentially philosophical suggestion of Einstein, taken up by logical positivists, to the effect that “our notions of physical reality can never be final,” performs too radical a surgery on the corpus of scientific knowledge. Some surgery was undoubtedly necessary after nineteenth-century excesses in mechanism had pushed to further extremes the mathematical realism sponsored by Galileo in the seventeenth century. But scientific agnosticism is also an extreme, and it can do more harm in the long run than an over-accelerated mathematical or mechanist development, for it eliminates the very possibility of organic growth within science itself. Heisenberg’s reaction is thus an encouraging one: it stresses the continuity of science, the assimilation of the new to the old, while insisting on a rigorous methodology that would not over-assert the objective value of mathematical theorizing in recent science. To those who appreciate the essential contribution of Albert and Thomas to medieval science, the parallel between their correctives to the mathematicism of Grosseteste and Heisenberg’s emendations to the idealism of Einstein is as interesting as it is unexpected. Einstein does have a message for the modern mind, and it is this, namely, that the mathematical realism of a Galileo, or the space-time absolutism of a Newton, are antiquated notions that can no longer function fruitfully for the modern scientist. We propose that the same cannot be said for the theory of physical proof proposed seven centuries ago by St. Thomas Aquinas.

Chapter Four Thomism and the Quantum Enigma

Chapter Four

Thomism and the Quantum Enigma

The recent publication of Wolfgang Smith’s The Quantum Enigma: Finding the Hidden Key1 has done more than propose a novel interpretation of quantum theory. It has also reopened a train of thought that has been somewhat muted in recent decades, namely, that of the relevance of the thought of St. Thomas Aquinas to solving problems raised by modern physics. What I have in mind are books published in the 1950s and 1960s by Jesuit professors at the Gregorian University in Rome2 and by Vincent Edward Smith in the United States,3 plus my own writings on the subject before I became heavily involved in the history of science.4 Now, out of the blue, as it were, Aquinas’s name is once again being invoked in the context of modern science, 1. Peru, Ill.: Sherwood Sugden & Company, Publishers, 1995, iii + 140 pp., with an appendix, a glossary, and an index of names. 2. Especially the following, all published by the Gregorian University Press, Rome: Peter Hoenen, S.J., Cosmologia, 5th ed. (1956); and his De noetica geometriae (1954); Philip Soccorsi, S.J., De physica quantica (1956); and his De vi cognitionis humanae in scientia physica (1958); and De geometriis et spatiis non-Euclideis (1960). 3. Notably, Vincent Edward Smith, Philosophical Physics (New York: Harper & Brothers, 1950); and Footnotes for the Atom (Milwaukee: Bruce Publishing Co., 1951). 4. “Newtonian Antinomies Against the Prima Via,” The Thomist 19 (1956): 151–92; “The Reality of Elementary Particles,” Proceedings of the American Catholic Philosophical Association 38 (1964): 154–66; “St. Thomas and the Pull of Gravity,” in Science and the Liberal Concept (West Hartford, Conn.: St. Joseph College, 1964), 143–65; and “Elementarity and Reality in Particle Physics,” Boston Studies in the Philosophy of Science 3 (1968): 236–71.

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this time as originating concepts that provide a “hidden key” to the solution of the quantum enigma. The author of this startling claim, a professor of mathematics at Oregon State University and apparently no relation to Vincent Edward Smith, surely deserves a hearing in these pages. Wolfgang Smith’s thesis is set out in six chapters: the first two, “Rediscovering the Corporeal World” and “What is the Physical Universe?,” establish the terms of discourse; the next two, “Microworld and Indeterminacy” and “Materia Signata Quantitate,” propose Smith’s solution, which basically consists in explaining the significance of state vector collapse in quantum theory; and the last two, “On Whether ‘God Plays Dice?’ ” and “In the Beginning,” draw out metaphysical implications of this teaching. An appendix provides a brief mathematical introduction to quantum theory so that the reader can appreciate what is meant by state vector collapse and other technical terms. A glossary gives a handy index of such terms and where they occur in the text. In Smith’s view, the devil that needs to be exorcised from contemporary physics is the bifurcationism that took its origin from René Descartes, then was reinforced by a succession of philosophers from John Locke to Immanuel Kant (ch. 1). This is the split between res extensa and res cogitans, the first denuding the world of sensible qualities and the second creating the impression that all such qualities (and the nature that underlies them, das Ding an sich) are projected into the universe by the observer. The mindset such bifurcationism puts into physicists is so strong, and has been reinforced in so many ways by their education and culture, that it is almost impossible for them to recognize it, let alone work at eradicating it. But eradicate it they must if they would solve the enigmas of quantum theory. And the only way they can do so, Smith argues, is by rediscovering the corporeal world. What this means is that they must learn what it is to perceive the world as it presents itself in sense experience, to expe-

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rience in their own lives the “miracle” of sense perception (16).5 The apple is outside us, but we perceive it nonetheless, with its colors and its other attributes, which are as real as we sense them to be (1–20). What, then, is the actual universe of the physicist? Obviously it is different from the corporeal world (ch. 2). It is accessed, not through perception, but through measurements and the artificial instruments that yield them. But more than measurements are required; they must be complemented by theories and the models these invariably suggest. Such modes of knowing result in “representations” (somewhat analogous to sensible images) through which physicists know what Smith calls “physical objects,” the entities that populate their universe and so are different from the “corporeal objects” of sense experience (23). The precise relationships between the two sorts of “objects” may be understood as follows. Every corporeal object X can be subjected to measuring procedures that will yield an “associated physical object” SX. X and SX are not the same thing, for X is perceptible whereas SX is not (25–26). Yet there is a similarity, a “resemblance,” between the two, and this consists essentially in the likeness of a mathematical form, of an abstract structure.6 Yet an asymmetry is found here also, in that one can always go from a corporeal to a physical object by metrical procedures, whereas one cannot always go the other way round. In the event that one can, the physical object is the SX of a corporeal object X, and X is referred to as a “presentation” of SX. Smith uses this asymmetry to divide “physical objects” into two further classes: physical objects that admit of presentation he refers to as “subcorporeal objects,” whereas those that do not admit of presentation he calls “transcorporeal objects” (27). The requirement of pre5. Numbers in the text refer to the page numbers of The Quantum Enigma. 6. Other connections between the two are that X and SX “occupy exactly the same region of space” and that they are also in “temporal continuity.” Geometrical continuity, Smith further explains, entails that “every decomposition of a corporeal object X into corporeal parts corresponds to a congruent or geometrically isomorphic decomposition of SX” (31–32).

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sentation is essential, Smith insists, if there is ever to be intellectual knowledge of entities in the physical world (31, 21–42). With this language presupposed, Smith moves on to consider problems of the microworld and indeterminacy (ch. 3). He first clears the ground by distinguishing a “generic physical object” from a “specific physical object,” since it is only the latter with which the physicist actually comes to deal. Its distinguishing note is that some type of observational contact has to already have been made with the object and in this sense can serve to “specify” it.7 Precisely how this specification of a physical object is achieved can be rather complex, but for Smith it usually involves conceiving the object in terms of an abstract or mathematical representation, what he terms a “physical system” (23n., 45). It is this system that defines the observables, that is, quantities that can in principle be determined by physical means. And it is here that the problem of determinacy and indeterminacy in quantum theory has to be addressed. Can the physical universe be divided into two subdomains, the macroworld and the microworld, and is the microworld really a “strange” world, different from that of ordinary experience? Smith’s answer to the latter question is that the microworld is indeed strange in the sense that it can be neither perceived nor imagined, but it is not “quantum strange” as it is commonly thought to be. “For example,” he goes on, “it is by no means the case that the electron is sometimes a particle and sometimes a wave, or that it is somehow particle and wave at once, or that it ‘jumps’ erratically from point to point, and so on” (48). This kind of talk “results from an uncritical and spurious 7. Smith’s example of a generic physical object would be “the electromagnetic field,” which exists only “in some abstract, idealized or purely mathematical sense;” his example of a specific subcorporeal object would be the planet Pluto, with which we already have some type of observational contact. Furthermore, there can be specification of a transcorporeal object, such as an elementary particle, but this must come about in two stages: the object must first interact with a subcorporeal entity, and then the latter must be observed (or rendered observable) through presentation as already described (43–44).

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realism—a realism which in effect confounds the physical and the corporeal planes.” What is happening here is that the microsystem and its observables are being confused, and the observables are being treated as classical attributes of the electron, “which they are not, and cannot be.” But this does not mean that Smith rejects realism itself. He is explicit on this: “the microworld is objectively real—as real, indeed, as the physical world at large, with which in fact it coincides” (49). What then to do about the Heisenberg uncertainty principle, the common source of talk about indeterminism? In Smith’s view that principle does not refer to the microworld as such. It refers to the result of measurements, and thus to the transition that takes place in passing from the physical to the corporeal plane. In the microworld itself, Smith maintains, there is no such thing as the Heisenberg principle. What is known about the electron, for example, is not its position or its momentum, but rather the state vector of the physical system in which it is being specified. In holding this Smith is not denying that a measurement performed on a physical system can cause the so-called collapse of the state vector (51). His point is rather that quantum mechanical systems still behave in a deterministic way, provided the type of determinism involved is properly understood: Obviously enough, this quantum mechanical determinism is a far cry from the classical. However, what has been forfeited is not so much determinism as it is reductionism: the classical supposition, namely, that the corporeal world is “nothing but” the physical. It is this axiom that has in effect become outmoded through the quantum mechanical separation of the physical system and its observables. Quantum physics, as we have seen, operates perforce on two planes: the physical and the empirical; or better said, the physical and the corporeal, for it must be recalled that measurement and display terminate necessarily on the corporeal plane. There are, then, two ontological planes, and there is a transition from the physical to the corporeal resulting in the collapse of the state vector. The collapse, one could say, betokens—not an indeterminism on the physical level—but a discontinuity, precisely, between the physical and the corporeal planes. (52)

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the former’s teaching, one on which he expatiates throughout the rest of the book. This is Heisenberg’s invoking of the Aristotelian notion of potentia when he suggests that microphysical systems constitute a kind of potency in relation to the actual world. From here on, the discussion becomes more technical and is not easily summarized. Since our interests here are more ontological than mathematical, perhaps this brief excerpt from Smith will convey the flavor of the exposition: Measurement . . . is the actualization of a certain potency. Now the potency in question is represented by the (uncollapsed) state vector, which contains within itself, as we have seen, the full spectrum of possibilities to be realized through measurement. To measure is thus to determine; and this determination, moreover, is realized on the corporeal plane: in the state of a corporeal instrument, to be exact. Below the corporeal level we are dealing with possibilities or potentia, whereas the actualization of these potentiae is achieved on the corporeal plane. We do not know how this transition comes about. Somehow a determination—a choice of one particular outcome from a spectrum of possibilities—is effected. We know not whether this happens by chance or by design; what we know is that somehow the die is cast. And this “casting of the die” constitutes indeed the decisive act: it is thus that the physical system fulfills its role as a potency in relation to the corporeal domain. (56–57)8

An additional point may now be made on the subject of determinism in relation to the electron. Smith had earlier noted that dynamic attributes such as position and momentum are not attributes of the electron. Now he clarifies his position on the electron’s so-called static attributes, such as mass, charge, and spin. These quantities do belong to the electron as such, and they are measurable with stupendous accuracy. “Of all the things, in fact, with which physics has to deal, there is nothing more sharply defined and accurately known than the electron” (60). 8. In this citation a footnote is inserted at the end of the sentence that reads, “We do not know how this transition comes about.” The note states: “We shall return to this question in chapters 5 and 6,” that is, in the last two chapters, which address more metaphysical issues.

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There can be no doubt that Smith takes inspiration from Heisenberg, and yet he is not in agreement with every element of Heisenberg’s teaching. The German physicist obviously considered himself a member of the Copenhagen school, even though he offered a distinctive interpretation of its doctrine. The distinctive element in that teaching, for Smith, was Heisenberg’s realist view of the microworld based on the Aristotelian concept of potency. It was this that allowed Heisenberg to maintain that there are two ontological domains in the discourse of physicists. There is a gap between the two domains, and physicists manage to bridge it by a measurement process. With this much Smith agrees. But he faults Heisenberg for making “no sharp distinction between the physical universe on a macroscopic scale and the corporeal world, properly so called” (63). Smith’s own view is that the “macroscopic objects of classical physics are every bit as ‘potential’ as are atoms and subatomic particles,” (64) a possibility Heisenberg fails to take into account.9 At this point we come upon Aquinas’s famous expression, materia signata quantitate, “matter signed with quantity,” which Smith makes the title of his fourth chapter. Here he uses the concept of nature as invoked by Heisenberg to explain the fundamentals of hylomorphic doctrine. Heisenberg’s “nature,” for Smith, touches a deeper level of reality than that represented in the corporeal and physical planes, a reality that points beyond the space-time continuum and suggests a way of dealing with “Bell’s interconnectedness theorem” (68–69). The structure of this new reality, which Smith refers to as “metaphysical,”10 is explained by Aristotle and Aquinas in terms of ὕλη (matter) 9. The precise difficulty is explained in more technical detail on pp. 62–64. This concerns, as I suggest, the problem of where one should situate the “potency” to which Heisenberg refers. Smith sees his distinction between X and SX as crucial in this matter. Smith is explicit that “SX exists as a potency, whereas X exists as a ‘thing or fact.’ ” Heisenberg, on the other hand, “appears in effect to identify SX and X” (64). 10. By his use of the expression “metaphysical realities” (73) Smith intends to designate realities that lie beneath the appearances, which is a common use of the term “metaphysical” today. This is not St. Thomas’s usage, however, for he reserved the term

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and μορφή (form), whence comes the English term “hylomorphic.” ὕλη designates a pure substrate unintelligible in itself; μορφή, its correlative knowable principle which renders natures intelligible to the human mind. Aligned with the former, the material principle is the accident of quantity, and aligned with the latter, the formal principle is the accident of quality. Smith then goes on to explain Heisenberg’s “nature” as a materia secunda in relation to the physical and corporeal planes: As materia, thus, it stands “beneath” the spatio-temporal domain in an ontological sense, as the carrier or receptacle, that is, of its formal content. And yet it owns a form which it passes on to the universe at large as a universal law or principle of order; as the least common denominator, so to speak, of the sum total of manifested forms. Nature, thus, turns out to be a materia quantitate signata (a materia “marked by quantity”), if it be permitted to adopt this excellent Thomistic phrase. (78)11

Here Smith’s explanation of the role of form is cryptic, but he clarifies it somewhat in his subsequent exposition. Qualities, he maintains, are ubiquitous on the corporeal plane, but they are missing completely on the physical plane. In his view “physical objects prove ultimately to be . . . [only] ‘potencies’ in relation to the corporeal world” (79). It is quality, as opposed to quantity, that betokens the “essence” of a corporeal entity (80). How Smith then sees the two as going together may be gleaned from the following: for a science of “being as such,” which he differentiated from “physics,” the science that treats of material or changeable being and whose principles are ὕλη and μορφή. 11. Here Smith adds a footnote in which he disavows any claim that the meaning he assigns to this phrase coincides with its original Thomistic connotation, for obviously “the Angelic Doctor was not thinking of quantum field theory.” Actually, St. Thomas uses this expression to explain how natural substances, or “natures,” are individuated within a species, and thus it is commonly referred to as his “principle of individuation.” For Aquinas, forma in the sense of natural form or substantial form is a specifying principle, whereas materia, along with the quantitas that serves to put “part outside of part,” is what differentiates one substance from another, despite their being the same in kind. Precisely how such individuation takes place is difficult to understand, and it is much disputed among Thomistic commentators. For a concise overview of the problem, see J. R. Rosenberg, “Individuation,” The New Catholic Encyclopedia 7:475–478.

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Quantity and mathematical structure . . . refer to materia, or more precisely, to the material aspect of things. The concrete object is made up . . . of matter and form; and this ontological polarity is reflected on the plane of manifestation. The existent object bears witness, so to speak, to the principles by which it is constituted; to both the paternal and maternal principles, if you will. And that is the reason, finally, why there are both qualities and quantities in the corporeal domain: the one indicative of essence, the other of the material substrate. (81)

Once one understands this, it is easy to see why “the only thing about a corporeal object that one is able to understand in terms of physics are its quantitative attributes” (82). SX is all that physics perceives. And that is no doubt the reason why physicists have been able to convince themselves (and the rest of the educated world!) that the corporeal object as such does not exist; or to put it the other way round: that X is “nothing but” SX. It is the reason why corporeal entities are thought to be “made of” atoms or subatomic particles, and why the qualities are held to be “merely subjective.” (82)

These excerpts from The Quantum Enigma, unsatisfying as they may be, will have to suffice for our present purposes. In the penultimate chapter, “On Whether God Plays Dice,” Smith takes up problems of causality and determinism and “hidden variable” theories, and makes use of the concepts of natura naturans and natura naturata to resolve the apparent impasses that are discussed in the literature. In his view, the significance of quantum discontinuity as seen in state vector collapse is that it betokens an action of natura naturans, not natura naturata (85–97). And in the final chapter, “In the Beginning,” he discusses the so-called big-bang theory and shows how it too involves a singularity and thus, like state vector collapse, gives witness to some type of “creative act” that lies well beyond the pale of the physical sciences (112, 99–113). By a remarkable coincidence, The Quantum Enigma came into my hands just as I was putting the finishing touches on the manuscript for a book, one that may lay the groundwork for understanding theses such as that advanced by Smith. This work has just been published

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with the title The Modeling of Nature: Philosophy of Science and Philosophy of Nature in Synthesis.12 In it I give some consideration to the quantum theory of the atom but I do not take up problems associated with quantum anomalies. Since I had the opportunity to insert a reference to Smith’s book before mine went to press, I added a footnote that now appears on p. 414 and reads as follows: No attempt has been made in this study to address the subject of quantum anomalies, since these presume technical competence beyond what can reasonably be expected of the general reader. A recent work that takes account of such knowledge and offers solutions that are consonant with the Aristotelian-Thomistic perspective here adopted is that of Wolfgang Smith, The Quantum Enigma: Finding the Hidden Key, Peru, Illinois: Sherwood Sugden & Company, 1995.

Having introduced that note, in the context of this discussion article I now feel it incumbent on me to reflect further on Smith’s work and its relationship to my own. Although the two books are concerned with different problems and addressed to different audiences, there are a number of points they have in common and on which they mutually support each other. These are the strong realism both endorse with respect to the corporeal object (X), the unequivocal rejection of Cartesianism and Kantianism (along with the mindset they introduce into modern physics), the need to address the status of the physical object (SX) and how one can make the transit from it to the corporeal world, the endorsement of Heisenberg’s use of the Aristotelian concept of potentia and the hylomorphism this involves, and, in general, the replacement of logical positivism by an Aristotelian-Thomism that opens out to a metaphysics for the eventual solution of problems now arising at the 12. Washington, D.C.: The Catholic University of America Press, 1996, xx + 450 pp., with illustrations and an index of names. What lies behind the subtitle is the fact that I have spent over forty years teaching both philosophy of science and philosophy of nature at the graduate and undergraduate levels. Much of my interest throughout that period has focused on Aquinas’s commentaries on the Physics and the Posterior Analytics of Aristotle.

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frontiers of physics. (The reader is not to think that X and SX and other technical terms introduced by Smith will be found in my book; of course, they will not. But their rough equivalents will be found there, although conceptualized in a different way.) The major difference between our two approaches is that Smith begins with a philosophy of science and works his way to a philosophy of nature at the end, whereas I do the reverse, beginning with the concept of nature and then ending with a philosophy of science based on that concept. His work addresses a very specific problem, the enigma posed by state vector collapse in quantum theory, whereas mine has the broadest possible scope, that of relating all of the modern sciences (physical, life, and human, including even ethics and politics) to the one concept of nature. And whereas Smith uses Aristotle and Aquinas mainly for their teachings on potencies and materia signata quantitate, I expand generally on the way analogia underlies the work of both thinkers, taking analogy as a synonym for “model” and exploiting the use of models in all these areas of inquiry. Although I nowhere mention this in my book, what is implicit in my treatment is the following idea. Aquinas, having been taught by Albert the Great, had an excellent grasp of Aristotle’s science of nature. He upgraded the knowledge this gave him to organize, as it were, a science of supernature (that of revealed theology), making use of analogy and the Aristotelian concept of a “mixed science,” combining propositions established by reason with propositions assented to by faith. My project would be to do something similar: to take knowledge we possess from ordinary experience of nature to organize the special type of knowing we call modern science, making use of analogy or modeling techniques and the “mixed science” of mathematical physics, which combines propositions established through the observation of nature with those of mathematics. Here I rely on a teaching that is distinctive of Thomism, in contrast to other Scholastic systems of thought, namely, that analogical middle terms are sufficient for a valid demonstration, no less in mathematical physics than in the sci-

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ence of sacred theology. Such terms, and the models they frequently employ, can provide us with insights into the microworld and the megacosm that are not unlike those Aquinas offered his contemporaries into the spirit world of the immaterial and the incorporeal. Another premise I owe to Arthur Fine, who proposed to mediate between “realists” and “anti-realists” by having both sides of their ongoing dispute adopt a “natural ontological attitude,” one that gives scientists the benefit of the doubt.13 This entails taking the certified results of science as knowledge claims on a par with the findings of common sense. Working with the leverage such an attitude provides, I explain first the concepts of ὕλη and μορφή, then how both of these were regarded as “nature” by Aristotle, and how they constitute the “inner dimension” of all natural bodies. I go on to instantiate this teaching by modeling, in sequence, inorganic natures, plant natures, animal natures, and human nature, inserting between the last two a treatment of the modeling of mind. In common experience, natures are grasped intuitively. My conviction is that, in the present day, people have a quasi-intuitive knowledge of the microworld and the megacosm based on the ways in which these are pictured for them in school and through mass media, particularly television. Indeed, they know more about natures than they give themselves credit for, once they are told what to look for and how to integrate what they see into their existing body of knowledge. Generally I bypass both quantum and relativity theories because of the mathematics they require for proper understanding. I do make use, however, of the Bohr-Sommerfeld model of the sodium atom, and this in fact is illustrated on the cover of the volume. The point I make is that the quantum “jump” of electrons that can be pictured in that model illustrates very well how “form” (μορφή) functions as an energizing and stabilizing principle in an inorganic nature. (Not

13. See Fine’s The Shaky Game: Einstein, Realism, and the Quantum Theory (Chicago and London: The University of Chicago Press, 1986), 112–35.

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that electrons really “jump,” as Smith makes clear.) The models I employ are for the most part iconic or pictorial models, and they suffice to give some sense of the “miracles” nature performs not only here but at all levels of being. I steer clear of mathematical models, mainly because they might prove opaque to many readers. Smith, of course, is expert with them. He uses precisely such a model to explain state vector collapse, and that is the strength of his book. Here I would only remark on how well he explains that model in the appendix. He starts with the double-slit experiment; then he gives a carefully crafted exposition of finite-dimensional Hilbert spaces, complex numbers, and state vectors; he next applies this geometry to the Heisenberg uncertainty principle, Schrödinger’s wave equation (having earlier discussed “Schrödinger’s cat,” 58), and the wave function of a particle; and he ends by going back to the double-slit experiment to show how matrix mechanics explains its findings precisely (115–36). With regard to technical details, there is little I would disagree with in Smith’s thesis. Although I too invoke Heisenberg in defending my models, and despite the fact that the latter has expressed qualified support for my views,14 I endorse Smith’s correctives to Heisenberg’s teaching on the relevance of potency to macroscopic objects as well as to atoms and subatomic particles (64). I also think he is on the right track in his insights employing the concept of esse, but that is an area of Thomistic metaphysics on which much has been written and is beyond the scope of this brief essay.15

14. See The Modeling of Nature, 414 and esp. n. 39. 15. I wish to thank Professor Smith for having read this essay in advance of publication and assuring me of the accuracy of my presentation of his thesis.

Part III

From Aristotle to Galileo

Chapter Five Medieval, Renaissance Sources of Science

Chapter Five

Medieval and Renaissance Sources of Modern Science A Revision of Duhem’s Continuity Thesis Based on Galileo’s Early Notebooks

The pioneers of the history of science movement, with an important exception, were not much interested in the Middle Ages.1 One can read George Sarton, William Dampier, and Alexandre Koyré, to name but three, and not generate any great excitement for the medieval period.2 Such historians may not have referred to these as the 1. Earlier versions of this paper were given at the University Seminar in Medieval Studies, Columbia University, New York, and at the Institute for Advanced Study, Princeton, New Jersey. The research on which it is based has been supported by the National Science Foundation, whose assistance is gratefully acknowledged. 2. Sarton’s evaluation of St. Thomas Aquinas, for example, is revealing in this regard. He states of Aquinas: “Though interested in science, he utterly failed to understand its true spirit and methods, and no scientific contribution can be credited to him. Indeed his mind was far too dogmatic to be capable of disinterested scientific curiosity.” Introduction to the History of Science, vol 2, pt. 2 (Baltimore: The Williams & Wilkins Company, 1931), 914. Such a statement obviously says more about Sarton than it does about Aquinas. For Dampier’s view, see the following note. Koyré’s attitude is sketched accurately by Edward Grant in his Physical Science in the Middle Ages (New York: Cambridge University Press, 1971), 114, where he gives references that substantiate Koyré’s belief in an “essential discontinuity between medieval physical science and the achievements of Galileo and the scientific revolution of the seventeenth century.”

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“Dark Ages,” but one gets the impression from them that they were pretty murky times—an uninteresting interlude between the close of classical antiquity and the rebirth of learning at the end of the Renaissance,3 which would lead directly to the seventeenth century and its “Scientific Revolution,” so graphically portrayed by Herbert Butterfield.4 The important exception was Pierre Duhem, who first wrote his fascinating essay on “Sozein ta phainomena: An Essay on the Notion of Physical Theory from Plato to Galileo,” then produced his three-volume study on Leonardo da Vinci, subtitled “Those Whom He Read and Those Who Read Him,” and finally his monumental ten volumes on Le Système du monde.5 In all these works the Middle Ages got their fair share of attention. Moreover, in the course of their writing, Duhem the scientist and the philosopher became Duhem the medievalist, a man passionately in love with the Middle Ages. And out of this research Duhem was emboldened to propose a daring two-part thesis: (1) that the condemnations of 1277 marked the origin of modern science, the decisive break with Aristotle and the beginning of new, imaginative cosmologies to replace his;6 and (2) that the fourteenth-century development following the condemnations gave birth to important new concepts, such as impetus and uniformly dif3. As Dampier puts it, “To us [historians of science], then, the Middle Ages have their old significance—the thousand years that passed between the fall of the ancient learning and the rise of that of the Renaissance: the dark valley across which mankind, after descending from the heights of Greek thought and Roman dominion, had to struggle towards the upward slopes of modern knowledge. In religion, and in social and political structure, we are still akin to the Middle Ages from which we have so recently emerged; but in science we are nearer to the ancient world. As we look back across the mist-filled hollow, we see the hills behind more clearly than the nearer intervening ground.” A History of Science, 4th ed. (Cambridge: Cambridge University Press, 1968), 60–61. 4. H. Butterfield, The Origins of Modern Science, rev. ed. (New York: Free Press, 1967). 5. The essay appeared in French in 1908 in the Annales de philosophie chretienne; it has been translated into English by E. Doland and C. Maschler with the title To Save the Phenomena (Chicago: University of Chicago Press, 1969). The other volumes remain in their original language: Études sur Léonard de Vinci, 3 vols. (Paris: A. Hermann, 1906– 1913), and Le Système du monde, 10 vols. (Paris: A. Hermann, 1913–1959). 6. See vol. 6 of Le Système du monde, which bears the title “Le Reflux de l’Aristotélisme: Les condemnations de 1277.”

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form motion, whose proponents, the Doctores Parisienses, were the precursors of Galileo.7 This is what is meant by “Duhem’s continuity thesis” in our title; it advocates a bond of continuity between medieval and modern science, but in such a way as to invite critical appraisal and revision in what follows. To put the matter somewhat differently, historians of science who, following Duhem, have addressed the continuity of thought between the Middle Ages and the modern era usually speak of the transition from the late medieval to early modern science.8 Here the expression “late medieval science” designates that following 1277 and elaborated throughout the fourteenth and fifteenth centuries—the science of the Oxford Mertonians, the Paris terminists, and the Paduan Averroists, all regarded, initially through the efforts of Duhem and then through the emendations of Anneliese Maier, Ernest Moody, John Herman Randall, Jr., Marshall Clagett, and others, as the “medieval precursors of Galileo.”9 The revised thesis to be defended in this essay is that the late medieval period was not the only one that contributed to the rise of modern science; more important, perhaps, was what we shall refer to as “high medieval science,” the science developed mainly by thirteenth-century thinkers, such as Robert Grosseteste at Oxford and Albertus Magnus, Thomas Aquinas, and Giles of Rome at Paris, all of whom did their work before the condemnations of 1277, or in essential independence of them.10 Our contention will be that this earli7. See vol. 3 of Études sur Léonard de Vinci, titled “Les Precurseurs parisiens de Galilee.” 8. Anneliese Maier, for example, entitled her five-volume series pursuing and revising Duhem’s theme in Studien zur Naturphilosophie der Spätscholastik (Rome: Edizioni di Storia e Letteratura, 1949–1955). 9. For Maier, see the previous note; E. Moody, Studies in Medieval Philosophy, Science, and Logic: Collected Papers 1933–1969 (Berkeley: University of California Press, 1975); J. H. Randall, Jr., The School of Padua and the Emergence of Modern Science (Padua: Editrice Antenore, 1961); M. Clagett, The Science of Mechanics in the Middle Ages (Madison: University of Wisconsin Press, 1959); also, the writings of Clagett’s students John Murdoch and Edward Grant. 10. A. C. Crombie has already supplied considerable background evidence in support of this theme; see his Medieval and Early Modern Science, 2 vols. (New York: Double-

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er group was just as influential in the birth of Galileo’s nuova scienza as was the later group; indeed, it was only when the ideas of both were put in juxtaposition that the elements were at hand for Galileo’s genius to become operative. Our procedure will be to start with the corpus of Galileo’s writings, with a special emphasis on his early notebooks, and to show how the ideas that were seminal in these and later guided Galileo’s mature works derive in a fairly direct line from both “high medieval science” and “late medieval science.” Thus we too are advancing the continuity thesis first proposed by Pierre Duhem, only enhancing it now to show a fuller dependence on medieval thought than has hitherto been proposed by historians of science. That much said, there will be three parts to the presentation: (1) a brief topology of medieval science, explaining “high” and “late” science, and indicating somewhat schematically the role of the condemnations of 1277 in their differentiation; (2) a description of Galileo’s early notebooks, their contents, the authorities cited in them, and their sources, and (3) an analysis of the ideas that were seminal for Galileo’s more mature thought, to ascertain his debt to his predecessors, first to those of the sixteenth century, and then, working back through the three previous centuries, to those of the high medieval period.

Topology of Medieval Science For our purposes, medieval science may be divided into three chronological periods, corresponding to the generally accepted division of scholasticism into early, high, and late:11

day Anchor Books, 1959); and Robert Grosseteste and the Origins of Experimental Science (Oxford: Clarendon Press, 1953). 11. This general parallelism is indicated in the author’s essay, “The Philosophical Setting of Medieval Science,” in David C. Lindberg, ed., Science in the Middle Ages (Chicago: University of Chicago Press, 1978), 91–119.

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“Early” medieval science.  This is the science of the twelfth century and before. During this period there was very little by way of accomplishment; it saw the recovery of some nature studies and of some Aristotle, but little else. From a methodological point of view, the analysis of this material requires a historiography unlike that used for later periods. Brian Stock’s Myth and Science in the Twelfth Century 12 is about the best anyone has done with it thus far, apart from encyclopedic accounts of individuals and their writings. We mention this period only to exclude it; it will not be of interest or of relevance to our general thesis.

“High” medieval science.  The span envisaged here covers the entire thirteenth century, extending perhaps into the first decade of the fourteenth, so as to include the magnificent researches of Theo­ doric of Freiberg on the rainbow.13 The distinctive characteristic of this period was the complete recovery of Aristotle, including the Posterior Analytics, the Physics, the De caelo, etc., with commentaries such as those of Simplicius and Averroës. Central to it was Grosseteste’s rediscovery of the distinction between knowledge “of the fact” (quia) and knowledge “of the reasoned fact” (propter quid), and his recognition that mathematics can supply “reasoned” or propter quid explanations for many physical phenomena.14 The contributions were mainly in optics, but some thought was given to astronomy also. This period was pronouncedly realist in orientation; “science” was understood in 12. B. Stock, Myth and Science in the Twelfth Century (Princeton: Princeton University Press, 1972). 13. These researches are sketched in the author’s article on Theodoric in the Dictionary of Scientific Biography (New York: Scribner, 1971), 92–95; see also his translation of portions of Theodoric’s treatise on the rainbow in Edward Grant, ed., A Source Book in Medieval Science (Cambridge, Mass.: Harvard University Press, 1974), 435–41. 14. See Crombie, Robert Grosseteste and the Origins of Experimental Science; also the author’s Causality and Scientific Explanation, vol. 1 (Ann Arbor: University of Michigan Press, 1972); and “Experimental Science and Mechanics in the Middle Ages,” in Dictionary of the History of Ideas, vol. 2 (New York: Scribner, 1973), 196–205.

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the hard sense of scientia, true and certain knowledge of the physical universe that could not be otherwise, though requiring special methodological techniques for its attainment, such as Aquinas’s refinement of the procedures for ex suppositione reasoning, already implicit in Aristotle.15 The most severe blow this period received was that of the condemnations of 1277.16 These were directed by the bishops of Paris and Oxford against the Averroists and, incidentally, against Aquinas and Giles of Rome, but they had the general effect of weakening knowledge claims, especially in the area of Aristotelian natural philosophy. Their occasion was a growing rationalism in the arts faculties that seemed to menace traditional teachings of Catholic theology. Faced with this threat, the bishops in some ways anticipated Immanuel Kant, who, as is well known, later found it necessary to deny knowledge to make room for faith.17 The knowledge the bishops denied was effectively Aristotle’s science of nature; they struck at its “true and certain” character, emphasized its fallibility, and so opened the door to the possibility of alternative explanations of the universe God had made.

“Late” medieval science  This is the science of almost all the fourteenth century and continuing through the fifteenth, centered, as already indicated, at Oxford, Paris, and Padua. Throughout this period the characteristic movement was nominalism, itself a type of skepticism compatible with the condemnations, and its chief proponent 15. For a detailed account, see the author’s Causality and Scientific Explanation; also the author’s “Aquinas on the Temporal Relation Between Cause and Effect,” Review of Metaphysics 27 (1974): 569–84; and “Buridan, Ockham, Aquinas: Science in the Middle Ages,” The Thomist 40 (1976): 475–83. 16. A general description of the condemnations is given in E. Gilson, History of Christian Philosophy in the Middle Ages (London: Random House, 1955); significant excerpts from the condemnations are translated into English in Grant’s Source Book (cited above), 45–50. 17. Immanuel Kant’s Critique of Pure Reason, trans. N. K. Smith (London: Macmillan, 1929), 29.

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was William of Ockham.18 The emphasis was still mathematical, but the focus shifted toward the logical, toward dubitabilia and sophismata, especially at Oxford. The language of quantification grew and calculatory techniques were devised for discussing all types of imaginary motions, involving infinities and even foreshadowing infinitesimals. Thomas Bradwardine, William Heytesbury, and Richard Swineshead laid the foundations for a new kinematics, but it all concerned points and imaginary bodies moving in empty space with little or no concern for the world of nature. At Paris, Jean Buridan, Albert of Saxony, and Nicole Oresme, the so-called Doctores Parisienses, are usually known as nominalists, but they were actually more realist in their interests, at least in the sense that they applied the calculatory techniques of the Mertonians to some motions found in nature.19 They developed the concept of impetus, and sought examples of motions in the universe that were uniformiter difformis (one would now say “uniformly accelerated”), but they failed to identify this as the characteristic motion of freely falling bodies. Still intimidated by the condemnation of the bishop of Paris, they too shied away from strong knowledge claims; their science was not as hardheaded as that of Grosseteste, Albert, and Aquinas. Apparently, they were surer of their logic than of their physics and on this account are aligned—in standard histories of philosophy—more with Ockham than with the realists of the thirteenth century.20 Finally, at Padua, in the early fifteenth century, Paul of Venice brought the calculationes back from Oxford and Paris, and trained his students in their use. Generally, the northern Italians combined the realist interests of the high scholastic period with the nominalist methods, although the nominalism was inhibited somewhat by the 18. See J. A. Weisheipl, The Development of Physical Theory in the Middle Ages (New York: Sheed and Ward, 1959) for an account of how the fourteenth-century development differed from that of the thirteenth. 19. This theme is developed in the author’s “Mechanics from Bradwardine to Gali­ leo,” Journal of the History of Ideas 32 (1971): 15–28. 20. By Gilson, for example, in his History of Christian Philosophy in the Middle Ages, 511–20.

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strong attraction of Averroës.21 A representative thinker was Gaetano da Thiene, who studied under Paul of Venice. There were many others, however, who developed techniques proposed by Aristotle in the Posterior Analytics to put the science of nature on firmer ground.22 Isolated from, and unaffected by, the condemnations that had been in effect at Oxford and Paris, they could still maintain the ideal of scientia, and in this sense, at least, were in essential continuity with the high medieval period. So much, then, for a quick topology of medieval science.

Galileo’s Early Notebooks Let us turn now to the questions of how much Galileo knew of these contributions and how they may have influenced his own scientific development. If we subscribe to William Shea’s characterization of Galileo’s intellectual life, we may divide this into an early, a middle, and a late period.23 The first extends from about 1580 to 1610 and embraces Galileo’s career as a student and later a teacher at Pisa, plus his professorship at Padua. The middle period extends from 1610 to 1632 and was centered mainly in Florence and Rome where Galileo was embroiled in his long disputes over the truth of the Copernican system, leading to his trial and condemnation after the publication in 1632 of the Dialogue on the Two Chief World Systems. The third period, finally, comprises the last ten years of his life, from the condemnation to 1642, spent largely in Arcetri, outside Florence, where he concentrated on mechanics, wrote his Discourses on the Two New Sciences, and thereby laid the foundation for what is now known as “modern science.” Recent research on Galileo has shown that the long middle 21. See the author’s “Mechanics from Bradwardine to Galileo” for more details. 22. Randall concentrates on this development in his The School of Padua and the Emergence of Modern Science. 23. This is indicated in his title, Galileo’s Intellectual Revolution: Middle Period 1610– 1632 (New York: Neale Watson Academic Publications, 1972).

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period devoted principally to astronomy represents something of a detour in the genesis of the “new science.”24 The early and late periods, on the other hand, are seen now as in essential continuity; in fact, evidence is available to show that practically all of the experimental and theoretical work necessary for the writing of the Two New Sciences had already been done by 1609, at which time Galileo perfected the telescope and set out to prove the truth of the heliocentric system.25 In light of this new information, Galileo’s early period, which has hitherto been somewhat neglected, is now being studied with care as of seminal importance for his later thought. The researches reported in this essay have concentrated on the first part of that period, the time Galileo spent in Pisa preparatory to his professorship at Padua when it apparently all began. While at Pisa, and probably in conjunction with his teaching there or in immediate preparation for it, Galileo wrote, in Latin, three sets of notes, or, to simplify somewhat, three notebooks.26 These notes are scholastic in inspiration, and they treat questions or difficulties raised by the text of Aristotle’s Posterior Analytics, Physics, De caelo, and De generatione. The first set, now contained in MS 27 of the Galileo Collection in Florence, we shall refer to as the logical questions; it contains treatises on demonstration and on the foreknowledge required for its attainment.27 The second set, that of MS 46, we shall call the physical 24. For a full documentation, see the monograph by W. L. Wisan, “The New Science of Motion: A Study of Galileo’s De motu locali,” Archive for the History of Exact Sciences 13 (1974): 103–306. 25. Some of this evidence is set out in the author’s “Three Classics of Science: Galileo, Two New Sciences, etc.,” in The Great Ideas Today (Chicago: Encyclopedia Britannica, 1974), 211–72. 26. These are not notebooks in the sense of quaderni, but more like looseleaf notes relating to a distinct subject matter that were subsequently bound together by others; thus the ordering of the folios is not necessarily chronological. 27. A description of these is given by A. C. Crombie, “Sources of Galileo’s Early Natural Philosophy,” in Reason, Experiment, and Mysticism in the Scientific Revolution, ed. M. L. Righini-Bonelli and W. R. Shea (New York, Watson Publishing International, 1975), 157–75.

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questions; it has lengthy disputations on the universe, the heavens, qualitative changes, and the elements.28 Finally, the third set, that of MS 71, contains drafts of several essays, including a dialogue, on the subject of motion.29 Only the latter notebook has received any attention from scholars, and this because of its obvious relation to the tract on motion in the Two New Sciences; all agree that it was composed “around 1590,” when Galileo was already teaching mathematics at Pisa.30 The logical and physical questions, on the other hand, have not been taken seriously, possibly because of their more pronounced scholastic style. Antonio Favaro, the editor of the National Edition of Galileo’s works, labeled them Juvenilia, or youthful writings, and saw them as dating from 1584, when Galileo was still a medical student at Pisa.31 Favaro further accorded to Galileo only the role of an amanuensis in their composition, suggesting that they were copied from the lectures of one of his professors at Pisa, Francesco Buonamici.32 Now, in a number of recent articles,33 and in a documented study entitled Galileo’s Early Notebooks: The Physical Questions,34 we ques28. See below at note 34. 29. These materials are described by R. Fredette, “Galileo’s De motu antiquiora,” Physis 14 (1972): 321–48. 30. Substantial portions of this notebook have been translated into English in Galileo Galilei, On Motion and On Mechanics, trans. and ed. I. E. Drabkin and S. Drake (Madison: University of Wisconsin Press, 1960); here the 1590 date is assigned to its composition. Additional portions are to be found in Mechanics in Sixteenth-Century Italy, trans. S. Drake and I. E. Drabkin (Madison: University of Wisconsin Press, 1969). 31. Antonio Favaro, ed., Le Opere di Galileo Galilei, vol. 21 (Florence: Tip. di G. Barbèra, 1890–1909; repr., 1968), 1.12 (henceforth cited as Opere). 32. Opere 1.12. 33. “Galileo and the Thomists,” in St. Thomas Aquinas Commemorative Studies 1274– 1974 (Toronto: PIMS, 1974), 2.293–339; “Galileo and Reasoning Ex suppositione: The Methodology of the Two New Sciences,” in R. S. Cohen et al., Proceedings of the Biennial Meeting of the Philosophy of Science Association (Boston: Springer, 1976), 79–104; “Galileo Galilei and the Doctores Parisienses,” in New Perspectives on Galileo, ed. R. E. Butts and J. C. Pitt (Boston: Springer, 1978), 87–138; and “Galileo’s Knowledge of the Scotistic Tradition,” in Regnum Hominis et Regnum Dei, ed. Camille Bérubé (Rome: Societas Internationalis Scotistica, 1978), 2.313–20. 34. Galileo, Galileo’s Early Notebooks: The Physical Questions. A Translation from

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tion Favaro’s use of the label Juvenilia and the dating on which it is based. New evidence is offered, moreover, to show that all of these notes derive from roughly the same sources and that they probably date in their entirety from the same period. It is also noteworthy that the present numbering of the manuscripts, i.e., 27, 46, and 71, follows Favaro’s system of cataloguing, which is by subject matter rather than by chronology. In the original collection of Galileo’s manuscripts, made by his student Vincenzio Viviani, all three notebooks were put in successive volumes;35 again, the curator had clearly written on the second notebook that this was Galileo’s examination of Aristotle’s De caelo made “around 1590.”36 If such be true, then all the notes would represent the work of Galileo’s head as well as his hand, either while he was a young professor at Pisa, 1589–1591, or at the earliest while he was aspiring to a teaching position in the year or so immediately preceding.37 Galileo’s citations of authorities in these notebooks will be of interest to this conference, for they reveal his rather extensive debt to authors of classical antiquity, the patristic period, the Middle Ages, and the Renaissance.38 Among classical Greek authors, in the three notebooks Galileo has over 200 references to Aristotle, many favorable but a goodly number critical of his thought, and scores to Aristotle’s Greek commentators, including 31 citations of Simplicius, 29 of John Philoponus, and 19 each of Alexander of Aphrodisias and Themistius. He further cites Plato 23 times, Ptolemy 20 times, Galen the Latin with Historical and Paleographical Commentary, ed. William A. Wallace (Notre Dame: University of Notre Dame Press, 1977). 35. We are indebted to Dr. Fredette for this information; more details are contained in his unpublished paper, “Bringing to Light the Order of Composition of Galileo Galilei’s De motu antiquiora,” as well as in his “Galileo’s De motu antiquiora.” 36. Opere 1.9. 37. This point was developed at length in a lecture delivered by the author at the Folger Institute, Washington, D.C., on October 15, 1975, entitled “The Dating of Galileo’s Pisan Manuscript: The Notes of a Reluctant Scholar? Or Those of an Aspiring Professor?” 38. A listing of such authors is given in the author’s “Galileo Galilei and the Doctores Parisienses.”

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15 times, and Archimedes and Hipparchus 6 times each. There are 31 citations of the Church Fathers, with St. Augustine being referenced most frequently, 8 times, St. Basil 4 times, Gregory of Nyssa 3 times, and Ambrose, Bede, Chrysostom, Damascene, and Jerome twice each. Among medieval authors, there are 65 references to Averroës, 14 to Avicenna, and 3 to Avempace, to name but three Arabs; Robert Grosseteste is cited only once, from his commentary on the Posterior Analytics; but Aquinas is cited 54 times, Albert the Great 21 times, Giles of Rome 14 times, Scotus 11 times, Ockham 6, and so on. Finally, there is a very extensive citation of Renaissance authors, including many Aristotelians teaching at the universities of northern Italy, some Neoplatonists, and a goodly number of scholastic commentators in the traditions of the various Schools. A study of such citations first alerted us to the fact that Galileo, in his use of medieval authors, relied much more heavily on those of the high scholastic period than on those of the late period, itself a reason for suspecting the accuracy of the Duhem thesis. A few years ago, in an article entitled “Galileo and the Thomists,”39 we called attention to Galileo’s particularly good knowledge of the Thomistic tradition; he made intelligent reference, for example to the writings of Capreolus, Cajetan, Soncinas, Ferrariensis, Hervaeus Natalis, Domingo de Soto, and Chrysostom Javelli. When one totals all of these, there are about 80 references to Aquinas and the Thomistic school, which would make these authors the most frequently cited after Aristotle himself. Now, that is a surprising and somewhat unexpected result, for if these notebooks have any bearing on Galileo’s intellectual development, and particularly if they contain materials that are in continuity with the writings of Galileo’s later life, one would have to admit that the high medieval period was by no means a factor that can be neglected when assessing Galileo’s debt to ages past. One may well wonder about the source of all these citations, and whether Galileo himself had a firsthand knowledge of the authors he 39. See note 33 above.

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cites—over 150 in all. A partial answer to this question is suggested by the circumstance that the earlier of the notebooks, those containing the logical and the physical questions, show considerable evidence of copying, or at least of being based on other sources.40 This indication notwithstanding, it has proved remarkably difficult to identify the books or manuscripts Galileo might have used in their composition. Owing to the researches of myself and others, however, we now have the answer to the puzzle.41 Practically all of this material, with its very erudite citation of authors, derives from textbooks and lecture notes that were being used at the Collegio Romano, the prestigious Jesuit university in Rome, from the 1570s through the 1590s. A full documentation of this statement with respect to the physical questions will be found in Galileo’s Early Notebooks.42 In its light, of course, it becomes a simple matter to understand the broad citation of writers, the humanist knowledge of classical antiquity, and especially the detailed scholarship relating to the patristic, medieval, and Renaissance periods. Galileo may have studied at Pisa, but in no sense do his notebooks derive from the meager philosophical instruction available at that university. No, when writing his notes, he went to the most scholarly sources he could find, to some of the most learned professors of his day, and from them derived his understanding of Aristotle’s Organon and his natural philosophy.

Galileo’s Debt to his Predecessors Our previous publications discussing Galileo’s use of these Jesuit sources have concentrated on topics in logic and in Aristotle’s De caelo 40. Favaro has noted this fact in his introduction to the so-called Juvenialia, Opere, 1.9–13, and in his brief remarks on the manuscript containing the logical questions, Opere, 9.279–282. 41. Alistair Crombie and Adriano Carugo have paralleled our investigations; their preliminary results are reported in Crombie’s “Sources of Galileo’s Early Natural Philosophy.” 42. Galileo’s Early Notebooks: The Physical Questions, 12–24, 253–303 passim.

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and De generatione—the matter of the first two notebooks—to show their continuity with the high medieval tradition.43 The focus of interest in this essay will be topics in the third notebook, that relating to motion, to make essentially the same point. Now the standard account of the origin of this third set of notes, sometimes called the De motu antiquiora to distinguish it from the treatise on motion in the Two New Sciences, is that they were prompted by Galileo’s interest in mathematics, and were not associated in any way with his pursuit of natural philosophy.44 Archimedes has been thought to be their inspiration more than Aristotle, and Galileo is said to have become interested in Archimedes’s work through the mathematician Ostilio Ricci, who had studied under Niccolò Tartaglia and is known to have privately tutored Galileo in mathematics. The concepts that characterize the third set of notes, moreover, are not those to be found in the third book of Aristotle’s Physics, where a philosophical account of motion is given in terms of potency and act. Galileo never discusses the Aristotelian definition, but prefers rather to discourse on the nature of heavy and light; the role of the medium in falling motion, the way in which rate of fall is determined by the buoyancy of the medium, and so is better related to the specific gravity of the falling object than to its absolute weight; the possibility of there being “neutral” motions, i.e., neither toward nor away from a center of gravity; what it is that causes the motion of projectiles after they have left the hand of the thrower, with a detailed explanation of a theory of impetus; the way in which impetus itself can be used to explain changes in the speed of fall of bodies; and so on. Galileo’s discussion of all these topics is unlike that found in books then available in northern Italy, and since his citation of sources in the third notebook is much sparser than in

43. See the papers cited in note 33 above; see also the author’s “Buridan, Ockham, Aquinas.” 44. This is the view of Stillman Drake, for example, and it is also that set out by Ludovico Geymonat in Galileo Galilei: A Biography and Inquiry into his Philosophy of Science, trans. Stillman Drake (New York: McGraw-Hill, 1965), 5–16.

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the previous two, scholars have rightly been puzzled as to the sources from which this composition derives. Girolamo Borro, who taught at Pisa while Galileo was a student there, and who is cited in this notebook, and also Francesco Buonamici and Giovanni Battista Benedetti, who are not cited but who touch on some of these matters in their treatises, have been mentioned as possible sources, but the details are vague and the problem is generally regarded as unsolved.45 It is our contention that the key concepts to be found in the third notebook derive, like those in the first two, from reportationes of lectures given by Jesuit professors at the Collegio Romano. These professors, although teaching the course in natural philosophy, were more sympathetic to mathematical approaches to physical problems than were the Aristotelians at Padua and elsewhere. Their openness in this regard is probably traceable to the influence of Christopher Clavius, also a Jesuit at the Collegio and the pre-eminent mathematician of the sixteenth century, who had stressed the importance of training in mathematics for anyone who would be proficient in the physical sciences.46 Most of this mathematics, it is true, focused on Euclid’s Elements and on the geometrical astronomy contained in Clavius’s own commentary on the Sphere of Sacrobosco. But the newer types of mathematical reasoning introduced by the fourteenth-century calculatores for dealing with problems of motion—and here we have in mind the Mertonians, the Parisian doctores, and the fifteenth-century Paduans—were not unknown to Clavius and his fellow Jesuits. Rather than treat these problems in the commentary on the third book of the Physics, however, as was the practice in the early part of the sixteenth 45. The treatises referred to are Girolamo Borro, De motu gravium et levium (Florence, 1576); Francesco Buonamici, De motu libri decem (Florence, 1591); and Giovanni Battista Benedetti, Demonstratio proportionum motuum localium (Venice, 1554). 46. Some details are given in the author’s “Galileo Galilei and the Doctores Parisienses; for a fuller account, see Guiseppe Cosentino, “L’insegnamento delle Matematiche nei Collegi Gesuitici nell’Italia settentrionale,” Physis 13 (1971): 205–17, and “Le mathematiche nella ‘Ratio Studiorum’ della Compagnia di Gesù,” Miscellanea Storica Ligure 2 (1970): 171–213.

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century at Paris,47 they reserved such treatises for the latter part of the course in natural philosophy, when they had been through the Physics and had already covered the doctrine of the elements in the De caelo and the De generatione. The motion of heavy and light bodies, De motu gravium et levium, was thus delayed until the students had studied the motions of the heavens and had a general qualitative knowledge of the elements and their properties. When one searches in the latter part of the course in natural philosophy given at the Collegio, therefore, one finds precisely the topics discussed by Galileo. To date, no evidence of direct copying on Galileo’s part has been found,48 but the similarity is there, and it is no difficult matter to trace the few changes Galileo could have made to produce the De motu antiquiora and then proceed from this on to the more systematic account he was to give in the Two New Sciences. In what follows, we shall discuss several of the topics treated in Galileo’s third notebook, as these are found in reportationes given by three Jesuits, by name Paolo Valla, Muzio Vitelleschi, and Ludovico Rugerio. All of these men taught “around 1590,” and upon their courses much of the material contained in Galileo’s first two notebooks is quite clearly based.49 The key concept of the De motu antiquiora is what later generations would refer to as “specific gravity.” Galileo does not use this expression, but speaks rather of gravitas propria, which has been translated into English as “essential heaviness.”50 It is this concept that ties Galileo’s analysis to Archimedes, and that permits him to introduce hydrostatic considerations into the discussion of bodies falling through a medium, where their effective weight will be determined by the me47. See the author’s “The ‘Calculatores’ in Early Sixteenth-Century Physics,” The British Journal for the History of Science 4 (1969): 221–32. 48. Many of the topics touched on by Galileo in his Memoranda on Motion, translated in Mechanics in Sixteenth-Century Italy, 378–87, are very much like those in the Jesuit reportationes, and could have been culled from these or similar sources. 49. For particulars on these three authors see Galileo’s Early Notebooks, 17–20. 50. By Drabkin, Galileo’s On Motion, 13.

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dium’s buoyancy. Now in a related text, when treating of weight or gravitas, Valla, Vitelleschi, and Rugerio all make explicit reference to Archimedes.51 Vitelleschi has the fullest discussion, cites Archimedes’ treatment of both weights (De ponderibus) and bodies that float in water (De iis quae aqua invehuntur), and makes a distinction similar to Galileo’s and on which the latter’s could have been based. Vitelleschi notes that different weights will produce different velocities of fall, but that one must be careful as to how he reckons gravity in order to compute this. In his mind, one gravity can be greater than another in two ways, either intensively or extensively. Gravity considered intensive respects the intensity or degree of weight proper to the material, whereas gravity considered extensive takes into account the size of the body and the number of its parts. To calculate velocity, he says, one must consider gravity both intensive and extensive, because though the intensity is the primary determiner of the motion, the extent of the body also affects the resistance it encounters from the medium and so limits its rate of fall.52 In this context Vitelleschi mentions Bradwardine’s treatise De proportione motuum and also Jean Taisnier’s work on the same subject, which gives all the mathematics necessary for calculation.53 And Taisnier’s book, as is well known, was plagiarized from Benedetti’s treatise on the ratios of motion, which, as has already been remarked, bears a strong similarity to Galileo’s own account.54 A related topic on which Galileo discourses at length is the cause 51. Valla, Tractatus quintus de elementis, disputatio secunda, quaestio ultima, conclusio secunda, Archivum Pontificiae Universitatis Gregorianae, Fondo Curia (henceforth APUG/FC), Cod. 1710, no foliation; Vitelleschi, Lectiones in octo libros Physicorum et quatuor De caelo, Staatsbibliothek Bamberg (henceforth SB), Cod. 70. H. J. VI. 21, fol. 370r–71r; Rugerio, Quaestiones in quatuor libros Aristotelis De caelo, SB Cod. 62. H. J. VI. 9, 79. 52. SB Cod. 70, fol. 363v–66r. 53. SB Cod. 70, fol. 365r. Vitelleschi simply states: “Legendum est Thomas Bradwardinus in sua tratatione de proportione motuum, et Ioannes Thaisnerus in tractatione de eadem rei . . .” The latter treatise, according to Drake and Drabkin (see following note), is contained in Taisnier’s Opusculum perpetua memoria dignissimum (Cologne, 1562). 54. See Mechanics in Sixteenth-Century Italy, 402.

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of speed in natural motions, i.e., what determines how fast a body falls. Consistent with his discussion of specific gravities, he assigns the cause to the weight of the medium as well as to the weight of the falling body, and exemplifies this with the classical case of the bladder filled with air, whose motion varies in different media.55 The same cases are discussed by Vitelleschi, and analogous conclusions drawn. Paralleling the criticisms contained in Taisnier’s (actually Benedetti’s) treatise, which rejects the rules of speed formulated by Aristotle in the fourth and seventh books of the Physics, Vitelleschi likewise questions their validity.56 Galileo’s rejection of them has frequently been seen as an innovation on his part, whereas these were far from being accepted dogma, save among the more conservative Averroist Paduans, who, unlike the Jesuits and other scholastics, searched for their philosophy in the text of Aristotle and there alone. Rugerio also rejects Aristotle’s rules of speed and refers the reader to the elaborate treatise on this subject written by Domingo de Soto and further expanded by Francesco Toledo, who had studied under Soto at Salamanca.57 And Soto, as we have documented elsewhere, was the author who thoroughly understood the uniformiter difformis doctrine of the calculatores and who was the first to apply it to the case of free fall.58 A third point Galileo makes, which again puts him in opposition to Aristotle, is his contention that air cannot have weight in its natural place, or put otherwise, that air has no weight when itself surrounded by air.59 Such a conclusion clearly follows from the application of Archimedean principles, but not from the texts of Aristotle found in the De caelo. It is noteworthy that Valla, Vitelleschi, and Rugerio all discuss these texts, as well as the many opinions of commentators, the experiments that have been adduced for and against Aristotle’s position, 55. On Motion, 23–38. 56. SB Cod. 70, fol. 365v. 57. SB Cod. 62, 215–16. 58. See the author’s “The Enigma of Domingo de Soto: Uniformiter difformis and Falling Bodies in Late Medieval Physics,” Isis 59 (1968): 384–401. 59. On Motion, 50–55.

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and the arguments based on Archimedes.60 Their conclusions, again, are quite consistent with the teachings contained in Galileo’s third notebook. Both Vitelleschi and Rugerio, moreover, cite the account of Girolamo Borro in his De motu gravium at levium, which describes experiments with falling bodies similar to those apparently performed by Galileo, and thus could be the source of the latter’s mention of Borro in the same notebook. Another topic taken up by Galileo that has proved particularly difficult to locate in previous writers is his mention of a third or intermediate type of local motion that is neither natural nor violent—the only two types hitherto allowed by Aristotle and the peripatetics.61 This is also commonly thought to have been Galileo’s innovation, found first in his early treatises on motion, and then later developed by him into the concept of circular inertia. Now it may be of interest that in the second notebook, the one containing the physical questions, Galileo has already adumbrated that concept, a fact completely overlooked by scholars. The topic comes up in his treatise on the heavens, when he is inquiring whether the heavens are made of a separate element and whether they are really incorruptible.62 Fire, according to the accepted doctrine of the time, was the lightest earthly element, and thus the one whose natural place would be closest to the lowest of the heavens, i.e., the orb of the moon. Galileo observes that when flame rises to the top of a furnace, its motion there becomes circular, and on this basis the motion of the fire in contact with the orb of the moon would also appear to be circular, that is neither up nor down, but remaining always at the same distance from the center of the earth. The question he proposes is whether such circular motion would be natural for fire in these circumstances, and his answer is in the negative. Then later, returning to the same phenomenon, he inquires whether this kind of 60. See note 51: Valla’s discussion is in his last question (no foliation), whereas Vitelleschi’s is on folios 369r–73r and Rugerio’s, 178–83. 61. On Motion, 72–76. 62. Galileo’s Early Notebooks, 81–102, esp. §§ I 2, 17, and §§ I 37–38.

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motion could be called violent, and that too he answers in the negative.63 Now, if a particular motion occurring in the universe is neither natural nor violent, then in some sense it has to be “neutral,” or intermediate between the two. As might be expected, these portions of Galileo’s treatise on the heavens have counterparts in lectures given at the Collegio Romano.64 Moreover, when one searches through the reportationes deriving from Vitelleschi and Rugerio, one finds in them explicit discussions of motions that are intermediate between the natural and the violent.65 Vitelleschi explains this in a way that is quite consonant with Galileo’s later development. A motion is violent, he says, if it is imposed from without and the object acted upon contributes no force at all. But for a motion to be violent in the strict sense, he continues, the action from without must be opposed to the natural inclination of the object. Should the body be acted upon in a way that does not oppose the body’s natural inclination, then the resulting motion is actually intermediate between the natural and the violent, and so may be regarded as natural, i.e., as beyond nature but neither according to it nor contrary to it. Vitelleschi goes on to observe that the generally accepted statement that no unnatural motion can be perpetual must be understood of the violent only in the strict sense, for it is this type that takes away the force of nature and so depletes the body’s source of motion.66 Implicit in this statement, of course, is the admission that a motion such as the circular motion of fire around the earth’s center, not being opposed to fire’s natural inclination, could go on forever—itself an adumbration of circular inertia.67 Another characteristic of Galileo’s third notebook is the use there of the medieval concept of impetus; he regards impetus as the agent 63. Galileo’s Early Notebooks, 97, § J16. 64. See the commentary on questions I and J, Galileo’s Early Notebooks, 266–70. 65. See note 51; Vitelleschi’s discussion is on fols. 275r–59r, Rugerio’s, 209–11. 66. SB, fol. 259r. 67. For a discussion of this concept and the controversies surrounding it, see S. Drake, Galileo Studies: Personality, Tradition, and Revolution (Ann Arbor: The University of Michigan Press, 1970), 240–78.

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in projectile motion and maintains that it continually weakens after the projectile motion has begun.68 Such a theory of “self-expending impetus,” as it is called, is usually traced to Buonamici, who is thought to have been the source of Galileo’s teaching.69 A careful check of Buonamici’s De motu, however, shows that, although he gives an account of impetus theory, he himself rejects it;70 thus it is difficult to see how Buonamici could be the source of its adoption by Galileo. Vitelleschi, on the other hand, is more open to impetus theory,71 and Paolo Valla, his immediate predecessor in the chair of natural philosophy at the Collegio, has a thorough explanation and justification of precisely the theory Galileo adopts.72 Thus again the Jesuits appear as a likely key to the doctrines contained in the De motu antiquiora. As a final point, we would cite Galileo’s celebrated explanation there as to why a body accelerates during the course of falling motion.73 Some years ago, in a much-cited article entitled “Galileo and Avempace,” Ernest Moody traced Galileo’s explanation to the teaching of the Arab philosopher Avempace, who held that the velocity of any motion results from an excess of the motive force over the resistance it encounters, and so the velocity of fall increases as the resistance grows less.74 Galileo’s explanation employs this principle, but the mechanism he adopts is actually that of the Greek thinker Hipparchus, who conceived of the resistance that must be overcome as a residual lightness or impetus previously impressed on the body, which is gradually dissipated during the fall.75 Now, it is interest68. On Motion, 76–85. 69. Alexandre Koyré is the source of this teaching in his celebrated Études galilèennes 1 (Paris: Hermann & C, 1939) 18–41. 70. Buonamici, De motu libri decem, 503–12. 71. For a discussion of Vitelleschi’s views on this subject, see the author’s “Causes and Forces in Sixteenth-Century Physics,” Isis 69 (1978): 400–12. 72. APUG/FC Cod. 1710, Tractatus quintus, disputatio prima, pars quinta, quaestio sexta: “A quo moveantur proiecta?” 73. On Motion, 85–94. 74. The article is reprinted in Moody, Studies in Medieval Philosophy, Science, and Logic, 203–86. 75. On Motion, 90.

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ing that Vitelleschi formulates the same principle also, mentions the teachings of both Avempace and Hipparchus, and gives a more sophisticated explanation than Galileo for the mechanisms involved in acceleration.76 Far from this being a novel contribution, this too is a matter about which the Jesuits were speculating “around 1590,” which stands in rather clear relation to the central theses of Galileo’s third notebook.

“High” vs. “Late” Medieval Science It is time now to take account of the significance of these new findings and how they relate to Duhem’s two-pronged thesis about the continuity between medieval and early modern thought. Obviously, it is not our intention to negate Duhem’s conclusions entirely, for it should be clear from what has been said that Galileo remains in considerable debt to late medieval thought as well as to that of the High Middle Ages. Our point is that even late medieval thought was transmitted to Galileo by sixteenth-century writers, who themselves modified the distinctive theses of their immediate predecessors, incorporated elements from high scholasticism as well as from a mathematical tradition that was beginning to emerge during that period, and so contributed substantially to the new synthesis Galileo himself was to elaborate in his later writings. A fuller account would thus see Galileo’s ideas originating in progressive, somewhat eclectic, scholastic Aristotelianism, otherwise quite Thomistic, which unlike the Aristotelianism in the Italian universities under Averroist influences, was sufficiently open-ended to incorporate the techniques of the calculatores and the Archimedean ideal of physio-mathematical reasoning applied to the world of nature. To spell out more clearly how the Duhem continuity thesis might

76. This too is explained in detail in the author’s “Causes and Forces in SixteenthCentury Physics.”

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be revised on this basis, we must refer back to its two parts as set out at the beginning of this study. The first part saw the condemnations of 1277 as marking the birth date of modern science. This has been roundly criticized by intellectual historians, mainly because these condemnations, being themselves a repressive tactic, were hardly compatible with the spirit of free inquiry that should characterize scientific investigation, and resulted in no recognizable spurt in scientific activity after they were pronounced.77 Such criticism notwithstanding, however, Duhem still had a valuable point to make. This point is that Aristotelianism, particularly when conceived as defending the text of Aristotle and that alone, did constitute an impediment to scientific inquiry. Aristotle had to be approached with a “critical temper,” to use John Murdoch’s expression,78 if progress was to be made in the true understanding of nature. But such a critical temper did not have to await the edict of Etienne Tempier for its genesis. It was already present in the Christian philosophers of the High Middle Ages, in Grosseteste and Albert and Aquinas and Giles of Rome, who were far from being disposed to seeing Aristotle as a god.79 The same mentality, quite obviously, is apparent in the reportationes of the philosophers of the Collegio Romano. They were teaching natural philosophy in its entirety, but they were also preparing students to be theologians, and they could not afford to be uncritical in evaluating Aristotelian doctrine. The same unfortunately cannot be said of the Averroists at Padua and elsewhere, so much extolled by John Herman Randall, Jr., for their role in the genesis of Galileo’s methodology.80

77. See Grant, Physical Science, 34–35, 83–90. 78. In his essay “The Development of a Critical Temper: New Approaches and Modes of Analysis in Fourteenth-Century Philosophy, Science, and Theology,” Medieval and Renaissance Studies 7 (1975): 51–79. 79. So Albert the Great could write: “Whoever believes that Aristotle was a god, must also believe that he never erred. But if one thinks that he was human, then doubtless he was liable to error just as we are.” Liber VIII Physicorum, tractatus primus, cap. 14, Omnia opera, ed. A. Borgnet (Paris, 1890–1899), 3.553. 80. In his School of Padua.

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No, it was these secular professors, not the clerics, who turned out to be the slaves to Aristotle. They were the ones who refused to look through Galileo’s telescope, against whom he could direct the barbed criticism that he was the true heir of Aristotle, and not those who called themselves by his name.81 The second part of Duhem’s thesis we would also revise, and this because of its excessive commitment to nominalism as the only philosophy consistent with the scientific enterprise. As is well known, Duhem was a positivist.82 His ideal of scientific explanation was merely “to save the appearances,” and this is all he felt his nominalist heroes were concerned to do.83 Whatever one wishes to say about that evaluation of fourteenth-century physicists, and this subject would bear much fuller investigation, there can be no doubt that such was never the mentality of Galileo in his early, his middle, or his late periods. As a philosopher Galileo was a realist through and through. He knew that the Ptolemaic system could “save the appearances,” and yet he fought to go beyond this to ascertain the actual structure of the universe. He knew that Aristotelian “rules of speed” could give a rough phenomenological account of falling motion, but he wanted a “new science” of motion, one that could demonstrate properties of motions that are found in nature. Whenever Galileo spoke of science and demonstration, as we have indicated elsewhere, his was the heard-headed notion of scientia found in thirteenth-century writers, not the weakened account that is attributed to those of the fourteenth and fifteenth centuries.84 If we wish, therefore, to do justice to the orientation Galileo received at the outset of his intellectual life, we do well to credit prop-

81. See Geymonat, Galileo Galilei, 192–97. 82. This is apparent in his The Aim and Structure of Physical Theory, trans. P. P. Wiener (Princeton: Princeton University Press, 1954). 83. The historical basis for this thesis is to be found Duhem’s To Save the Phenomena. 84. For documentation, see the author’s “Galileo and Ex suppositione Reasoning” and “Buridan, Ockham, Aquinas.”

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erly the scholastic (should we say Thomistic?) Aristotelians on whose thought his three notebooks are obviously based. When we do so, we can readily discern a continuity between early modern science and that of the High Middle Ages. Galileo stands in debt not only to the fourteenth and fifteenth centuries, but to the thirteenth century as well.85 He took his beginning from sixteenth-century writings that were progressive and open-ended, that were knowledgeable in the extreme, and that incorporated the best to be found in the three preceding centuries. To neglect this fact is to fail to understand what Galileo’s writings, both early and late, are all about, and how he could make the contributions that merit for him the title “Father of Modern Science.” 85. Moody himself signaled this conclusion when he noted, in the “Galileo and Avempace” article, that “Galileo’s Pisan dialogue seems to move wholly within the framework of the thirteenth century formulations of the problem of motion,” and that its sources “are to be sought elsewhere than in the tradition of fourteenth century Oxford or Paris or than in the tradition of fifteenth century Padua.” Studies in Medieval Philosophy, Science, and Logic, 274.

Chapter Six Aquinas, Galileo, and Aristotle

Chapter Six

Aquinas, Galileo, and Aristotle

Some fifty years ago George Sarton, the principal founder and promoter of history of science in the United States, could dismiss Thomas Aquinas in a single sentence. “Though interested in science,” wrote Sarton, “he utterly failed to understand its true spirit and methods, and no scientific contribution can be credited to him.”1 Were I receiving the Sarton Medal from the History of Science Society this evening, rather than the Aquinas Medal from the American Catholic Philosophical Association, I would be considerably embarrassed by that statement. Here, on this occasion, I have no embarrassment whatever. Sarton was dead wrong: he did not know his Aquinas very well, nor, as it turns out, did he know his history of science. So, as I complete my sixty-fifth year, with more than half my life devoted to the study of Aquinas and to parallel work in history of science, I take this opportunity to set the record straight. My title, “Aquinas, Galileo, and Aristotle,” groups together the three thinkers about whom I know the most, whose juxtaposition can put Sarton’s assertion to the test, and, at the same time, I trust, carry a strong message of philosophical interest to the members of this Association. About Galileo and Aristotle, the two latter members of my triad, I presume that most of you already have your minds made up. It is 1. George Sarton, Introduction to the History of Science, vol 2, pt. 2 (Baltimore: The Williams & Wilkins Company, 1931), 914.

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common knowledge, after all, that the “Father of Modern Science” set the Western World on its present course by overturning Aristotle and the twenty-century-long tradition he had imposed on antiquity and the Middle Ages. With regard to Aquinas you are perhaps more innocent. If you take your Thomism from approved sources, you may think that the Angelic Doctor spent his life meditating on the distinction between essence and existence or on biblical texts such as “I Am Who Am,” and had little time for the world of nature. Perhaps all three men stand out for you as representatives of three distinct disciplines—science, philosophy, and theology—categories of thought so disparate as to have almost nothing in common. If these are your impressions, then they stand in need of substantial correction. My thesis, indeed, attempts to show just the opposite: that Galileo stood in considerable debt to Aristotle for his science; and that this debt was mediated to him through a progressive Aristotelianism coming directly from Thomas Aquinas, without which modern science—science as we know it—would not be the reality it now is.

Galileo Let us start then with Galileo. In the middle of last month, at Pisa, Padua, Venice, and Florence, an International Galileo Congress was attended by historians, scientists, and philosophers from all over the world. It celebrated the 350th anniversary of the famous trial that took place in Rome, wherein Galileo’s avowed heliocentrism was condemned by the Inquisition. The last time anything approaching the proportions of this Congress was held in Italy was in 1964, almost twenty years ago, at which event the fourth centenary of Galileo’s birth was celebrated with fitting pomp and ceremony. There was a difference between the papers read at the two Congresses, however, as noted by Professor I. Bernard Cohen of Harvard University in his comments at the concluding Round Table on March 26th. Whereas in 1964 the themes that emerged were Galileo and Platonism, the role

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of “thought experiments” in science, and the structure of the masterworks of the great Italian physicist, this time the focus had changed entirely. Now it was Galileo and Aristotle who received the attention, not “thought experiments” but real experiments recorded on manuscripts long neglected, not masterworks but notebooks written in Latin wherein Galileo put down his early thoughts on the subject of physical science and its methodology. No longer was it amateur historians trained as scientists who were intent on reconstructing Galileo in their own image, but professional scholars examining all the evidence impartially and coming to quite different conclusions about the genesis of modern science. Here is not the place to rehearse these latest findings in Galileo scholarship. Suffice it to mention a key piece of evidence, Galileo’s commentary (or, more properly, questionary) on the Posterior Analytics of Aristotle, now known to date from his first teaching post at the University of Pisa. In it, Galileo manifests a sophisticated knowledge of the requirements for demonstration in the science of nature, as well as of matters that must be foreknown, including the suppositiones on which reasonable argument will be based, if one is to come to new knowledge about the physical universe. Especially noteworthy is his understanding of cause and effect, of the various types of cause, essential and accidental, that function in natural phenomena, and of the many impedimenti and accidenti that can subvert one’s efforts to uncover valid explanations through their use. Also important is Galileo’s awareness of the ways in which mathematics qualifies as a strict scientia in its own right, and so can be used with profit in the scientiae mediae subalternated to it when investigating nature in its quantitative aspects. In his notebooks devoted to more physical questions—such as the constitution of the heavens, the elements and their qualities, and the study of motion—Galileo’s main concentration is on the concept of nature and how this is related to motive powers such as gravitas, levitas, and resistentia. Building on the distinction between the nat-

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ural and the violent, he investigated the possibility of a local motion that would be intermediate between the two, and thus, once initiated, might continue unimpeded for as long as one would wish. Ideas such as these, coupled with the concept of impetus developed by medieval Aristotelians, brought him to the notion of a “circular inertia,” with which he made his early attempts to bridge the gap between terrestrial and celestial physics. The notebooks to which I have reference were probably completed by 1591, when Galileo relinquished his post at Pisa and began his long teaching career at the University of Padua. Hitherto unnoticed, no one had thought of tracing their terminology and conceptual development throughout his later writings. Now the surprising discovery has been made that the Aristotelian influences recorded in the notebooks are present in all of Galileo’s scientific treatises, from his early investigations of floating bodies to his masterworks dealing with the Two World Systems and the Two New Sciences. The mature science of Galileo turns out to be in essential continuity with his first attempt to sketch a mathematical physics of motion and mechanics, with key ideas drawn from the Posterior Analytics, the Physics, the De caelo and De generatione, and the Quaestiones mechanicae exerting a regulative influence throughout his entire scientific career.

Aristotle But, you say, how can this be? Is it conceivable that anyone who launched so many diatribes against the Peripatetics of his day could actually stand in debt to Aristotle? A good question, this. Yet its answer is not to be found in a hidden admission of indebtedness on Galileo’s part, but rather in the polemics and the controversies that surrounded him throughout his career. As a professor at Pisa and Padua, his battles were much like our own—rarely noticed outside the confines of the classroom or of the university in which he lectured. But after his discoveries with the telescope, after he secured his ap-

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pointment as philosopher and mathematician to the Grand Duke of Tuscany, Galileo became a public figure who stood in an adversary relationship with the academic establishment of his day. His were not staid scientific treatises that laid out the facts impartially for the learned world to read. No, his style of writing became that of the humanist: letters and dialogues wherein rhetorical skills could embellish arguments and take maximum advantage over unwary adversaries. And the Aristotelians of Galileo’s day, as typified by Cesare Cremonini—his favorite antagonist at the University of Padua—lent themselves admirably to this type of tactic. Those of us accustomed to the medieval Aristotle find it difficult to grasp properly the context in which Galileo worked. Our Aristotle, after all, is one who patently needed correction, many of whose teachings were in conflict with the faith, whose ideas could be appropriated selectively and then used to erect a synthesis incorporating findings never known in Greek antiquity. Not so the Aristotle of the Renaissance, that of a Cremonini or of the humanists and Averroists who taught in Galileo’s day. These were textual scholars, philologists if you like, who found their philosophy not in nature but in the writings of their master. Reactionary to an extreme, they fought any idea that was not explicit in the Greek text, that departed ever so slightly from the thought of the Stagyrite. The medieval doctrine of impetus, and of the possibility of motion through a void, are typical of the teachings they rejected. The Doctores Parisienses and Thomistic commentators such as Domingo de Soto had no difficulty assimilating, within a progressive Aristotelianism, innovations such as these. After all, they were more in accord with the facts as ascertained in rudimentary experiments, and they provided a simple way of updating the Aristotelian corpus. Much the same could be said of Aristotle’s rules for calculating the velocities of motions and the ratios to be found among them. From the fourteenth through the sixteenth centuries great progress had been made in such revisionary studies, but these were all lost on the Peripatetics of early

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seventeenth-century Italy. They saw them only as perversions introduced into the canonical texts by the “Latins,” and thus as opposed to the authentic teachings of Aristotle. A related development that helps explain the bitterness of Galileo’s attacks on the Aristotelians was the dispute over disciplinary domains that became acute in his lifetime. Mathematicians and philosophers at that time found themselves at cross purposes in their investigations. Then, as now, there were not lacking partisans of the one discipline who spared no pains to discredit the other. Alessandro Piccolomini is of special interest in that regard. He searched through all of Aristotle’s references to mathematics and came up with a strong case to show that mathematics could never be an ἐπιστήμη or scientia, that it could not uncover causes, that it could not provide strict demonstrations, and, in any event, that it lacked any relevance to the real world. Others concentrated on Aristotle’s teaching in Book Alpha of the Posterior Analytics where he seems to rule out μετάβᾰσις in strictly scientific reasoning. μετάβᾰσις would be the transfer or transformation of principles from one science to another. Taken in all rigor, it would prohibit the use of mathematical principles in the study of nature. Stated otherwise, μετάβᾰσις would make a mathematical physics impossible, and would frustrate completely Galileo’s attempts to develop his “new sciences” of motion and mechanics.

Aquinas So much, then, for Galileo and Aristotle—the Aristotle taught in the universities of the time, whose followers were the constant butt of Galileo’s jibes. Now, where does Aquinas come in to this picture? How could a thirteenth-century theologian and metaphysician possibly mediate a dispute of such proportions as was forming between the youthful scientist and the reigning philosophers in the Schools? The answer will never be found if one concentrates on Thomas’s theology or existential metaphysics alone. It can be found if one goes

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back a few decades before Galileo began his studies, to the famous Dominican of Salamanca, to Domingo de Soto. Soto then faced the almost impossible task of teaching theology to students who knew no logic or natural philosophy whatever. His solution was the straightforward one of composing commentaries and questionaries on the principal Aristotelian texts, bringing them up to date with revisions from the Oxford and Paris schools. His progressive Aristotelianism, his developmental Thomism if you wish, gave his students an advanced knowledge of nature and of the methods to be used in investigating its secrets. It did so at precisely the moment when Europe was pregnant with the new knowledge that would usher in the modern era. But Soto lived in western Spain, far from Pisa and Padua. How could he have exerted an influence on the young Galileo? Here my story takes on an air of the incredible, but it is a story I must tell nonetheless. We know that Soto’s favored disciple at Salamanca, Francesco Toletus, played a key role in the story. Yet he was not alone. Perhaps an even greater role was played by an emerging German scholar, Christopher Clavius, then finishing his studies under the mathematical realist Pedro Nunez at the University of Coimbra. Both of these men, Toletus and Clavius, you see, were members of the newly founded Society of Jesus. Soon they were sent from the Iberian Peninsula to the Eternal City, to form the nucleus around which Ignatius could build his famous Collegio Romano. And it was through the Collegio Romano that Aquinas, and Soto, ultimately put their imprint on the mind of a struggling mathematical physicist at the University of Pisa, Galileo Galilei. This brings me back to the subject of Galileo’s Latin notebooks, mentioned earlier in this paper. The dating and provenance of those notebooks have eluded scholars for centuries. Now the last pieces of the jigsaw puzzle are almost in place, and we have a clear idea of where the notebooks came from. Essentially, they were copied from lectures at the Collegio Romano by a small group of Jesuits, under the inspiration of Toletus and Clavius, who laid the groundwork on which

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a valid mathematical approach to the world of nature could be based. How Galileo made use of these lectures could be the subject of more than one book, and would take us far afield were we to attempt even a brief account. The key idea was clearly expressed by Aquinas: quantity can be studied by both the mathematician and the metaphysician, but it is a proper subject of investigation for the natural philosopher as well. Intelligible matter is not completely alien to the world of sensible matter. In fact, the quantifiable aspects of natural phenomena render them especially intelligible to the human mind. Rather than deprecate mathematics as a science, or underestimate the importance of the scientiae mediae in the study of nature, as the Peripatetics in the Italian universities were then doing, this progressive Aristotelianism saw mathematical reasoning as the most certain of which the human mind was capable, and welcomed its assistance in plumbing the secrets of the physical universe. One of Galileo’s main teachings, traceable to his Jesuit sources, concerns the role of suppositiones in scientific demonstrations. A mathematical physics is impossible if one does not know the proper suppositiones to employ in its reasoning processes, or how to go about establishing their truth. If based on purely hypothetical and fictive premises, mathematical physics can never be more than a scientia ex suppositione, a scientia secundum quid. It was Galileo’s great achievement to show that his scientia media did not have to labor under this limitation. Under proper conditions, and particularly when one could verify one’s suppositiones through a posteriori demonstration to the required degree of accuracy, the impasse posed by μετάβᾰσις could be overcome and mathematical physics could achieve the status of a scientia simpliciter. This was the point of all Galileo’s experimentation and use of precise measuring techniques, finally uncovered in manuscripts that have rested unexamined for centuries. The accuracy of his results was not 100 percent, to be sure, but deviations from calculation were insensibile—the very term he used—and that was all he needed in the study of sensible matter. Therefore, his could be a nuova scienza

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based on dimostrazioni, as he repeatedly claimed. But its canons were those of Aristotle’s Posterior Analytics read with the eyes of Aquinas, and appropriated by him from the Jesuits of the Collegio Romano.

Implications So we come to the message behind this brief excursus into the history of science. Modern philosophy, as you are well aware, took its warrant from the Scientific Revolution and the purported repudiation of Aristotle on which that revolution seemed based. Take away the claimed repudiation, and see what remains of modern philosophy. Descartes, simplistically, thought he could get by without the concept of nature. Hume thought he could do away with causal reasoning and the necessary connections on which it was based. Kant, seduced by his reconstruction of Newtonian physics, went the route of agnosticism when faced with all the “great problems” of traditional philosophy. Now Galileo was fond of taunting his Peripatetic adversaries with the thought that, if Aristotle were alive in the early seventeenth century, the “Master of All Who Know” would be in agreement with him and his methods, and not with those who paraded under his name. I wonder what, mutatis mutandis, Galileo would have to say were he to come alive today. Would he, the great realist, unafraid of advancing truth claims about the physical universe even at risk of his life, capitulate so readily before the problem of knowledge as did the “moderns”? I think not. Were it a case of ranging himself with the skeptics such as Hume and Kant, on the one hand, or with Aristotle, on the other, I have no doubt where Galileo would be found. The “Father of Modern Science” would be solidly alongside Aristotle and Aquinas, with the long tradition that has continued to develop their thought in the light of the discoveries he was the first to proclaim. Look now at contemporary philosophy, and particularly at philosophy on the American scene. The American Philosophical Association and the Philosophy of Science Association are in complete disarray.

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The logical positivist and analytical movements have shown themselves bankrupt, and attempts to replace them by one or other form of Continental idealism have exacerbated the situation only further. The “great problems” of traditional philosophy remain unaddressed. Gimmickry continues unabated, example and counter-example are still the stock in trade, and the best hope for an American philosopher, to use Richard Rorty’s expression, is “that we shall all be superstars for approximately fifteen minutes apiece.” The “superstars,” let us not be deceived, are created by the establishment, and their glowing half-life will probably never be documented in any serious attempt to write a history of philosophy for our era. In philosophy of science the problem of induction is nowhere near a solution, nor is that of verification or confirmation. Truth claims themselves are slowly being discarded. They are giving way to a Kuhnian relativism that sacrifices truth on the altar of progress—yet another way of reformulating the worn-out doctrine of pragmatism. This situation is known to all of you, for it well explains the existence of an association such as our own. But I am afraid we have not learned the lessons we might from the case of Galileo, and the watershed he apparently provided for the rise of modern thought. Not unlike George Sarton, the great Thomists of our century, Jacques Maritain and Etienne Gilson, were unappreciative of natural philosophy and of the contributions Aquinas made to the development of that discipline. It is time that we return to the full heritage that is ours, a heritage that no other philosophical association can boast. Know your Aristotle. Master your Aquinas. Study the world of nature. Examine the methodology that must be employed to unveil its secrets. Only then will you have firm ground on which to build your epistemology, your metaphysics, your natural theology. Encourage your students to acquire Latin, even to learn the intricacies of medieval paleography. The historical record lies there, just waiting to be rediscovered. It is time that that record be set straight, for it has enormous implications for the future of our profession.

Chapter Seven Certitude of Science in Renaissance Thought

Chapter Seven

The Certitude of Science in  Late Medieval and Renaissance Thought

In a recent study entitled Probability and Certainty in SeventeenthCentury England, Barbara Shapiro points to the erosion of the traditional Aristotelian concepts of science and certitude as giving new direction to the work of English intellectuals in the seventeenth century.1 Without denying that such an identifiable change may have taken place there and then, in this essay I would like to sketch a broader panorama of changing attitudes toward the certitude of science— focusing on Western Europe from the thirteenth to the seventeenth century. And rather than analyze the work of one scientist or of a small group, I shall draw on a number of themes in my previous writings to accent the complexity of this issue when addressed over four centuries of scientists and scientific growth. It is difficult to make generalizations over such a long period, and yet I shall argue that discernible patterns emerge. Put somewhat schematically, the period prior to the Condemnation of 1277 saw the greatest confidence in the certitude of science; after that, the rise of nominalism led to an erosion of that confidence, terminating in the eclectic pluralism of the late fifteenth 1. The book’s subtitle reads: A Study of the Relationships between Natural Science, Religion, History, Law, and Literature (Princeton: Princeton University Press, 1983).

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and early sixteenth centuries; the Renaissance and “Second Scholasticism” contributed to such erosion with disputes over disciplinary domains between philosophers and mathematicians and the probabilist controversies of theologians; but Galileo reasserted that confidence with the demonstrations of his “new science,” which were to inspire not only Descartes and Newton but a host of scientists down to John Herschel in the nineteenth century. So my thesis is that certitude was not seriously claimed for natural science during the late Middle Ages and the early Renaissance, but that it began to be claimed again in Italy in the early seventeenth century, precisely when Shapiro says it was being rejected in England.

Science in the High Middle Ages The ideals of scientia, or certain knowledge reasoned to from evident first principles by causal analysis, were well understood in the High Middle Ages. The recent studies of Steven Marrone on William of Auvergne and Robert Grosseteste and of David Lindberg on Roger Bacon, plus earlier works on Grosseteste, Albertus Magnus, and Thomas Aquinas, portray how these investigators rediscovered Aristotle’s Organon and applied it assiduously to uncovering the secrets of nature.2 All had confidence that truth and certitude could be attained in a general way using the Aristotelian canons, even though there were many matters—about the heavenly bodies, for example—on which doubts could be and were expressed.3 Because of Grosseteste’s and Bacon’s 2. Steven Marrone, William of Auvergne and Robert Grosseteste (Princeton: Princeton University Press, 1983); David Lindberg, Roger Bacon’s Philosophy of Nature (Oxford: Clarendon Press, 1982); James McEvoy, The Philosophy of Robert Grosseteste (Oxford: Clarendon Press, 1982); J. A. Weisheipl, ed., Albertus Magnus and the Sciences (Toronto: Pontifical Institute of Mediaeval Studies, 1980); and Leo Elders, ed., La Philosophie de la nature de Saint Thomas d’Aquin (Rome: Editrice Vaticana, 1982). 3. R. C. Dales, “The De-Animation of the Heavens in the Middle Ages,” Journal of the History of Ideas 41 (1980): 531–50; Edward Grant, “Celestial Matter: A Medieval and Galilean Cosmological Problem,” Journal of Medieval and Renaissance Studies 13 (1983): 157–86.

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concern with light, I should note the strong attraction exerted by mathematics in their optical treatises, so much so that one might say that these English writers pursued the ideal of a “mixed science” (or a scientia media intermediate between mathematics and physics) rather than a “pure physics” in the Aristotelian sense. Albertus Magnus, on the other hand, in attempting to develop all the sciences contained in the libri naturales of the Arabs as well as in Aristotle’s writings, saw more of the difficulty involved in natural science as such. Indeed, he cites several times a statement of Ptolemy to the effect that naturalists always disagree over their science and are not like mathematicians in this regard, so that perhaps mathematics alone can lay claim to being a strict science in the sense of attaining certitude.4 The use of eccentrics and epicycles to account for the heavenly motions was one of the matters on which Albertus, like his student Aquinas, had doubts. And yet, as I have argued elsewhere, Albertus also analyzed carefully the suppositional necessity that characterizes nature’s operations, and explained how one might have strict demonstrations, in the Aristotelian sense, if one could formulate a demonstration ἐξ ὑποθέσεως, as Aristotle himself puts it, or ex suppositione finis, in the Latin terminology of Albertus and Aquinas.5 It was Aquinas who best explained this suppositional methodology in his commentaries on the Physics and the Posterior Analytics.6 The problem arises because the world of nature is contingent and defectible: nature acts for an end, but it does not achieve that end infallibly and invariably, mainly because its agencies work across time and with matter that can prove to be defective. If one observes the regularity of its operation, however, since it does achieve ends regularly and 4. W. A. Wallace, “The Scientific Methodology of St. Albert the Great,” in Albertus Magnus Doctor Universalis 1280–1980, ed. G. Meyer and A. Zimmerman (Mainz: Matthias Grünewald Verlag, 1980), 385–407. 5. W. A. Wallace, “Albertus Magnus on Suppositional Necessity in the Natural Sciences,” in Albertus Magnus and the Sciences, 102–28. 6. W. A. Wallace, “Aquinas on the Temporal Relation Between Cause and Effect,” Review of Metaphysics 27 (1974): 569–84.

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for the most part, one can reason ex suppositione finis, that is, from the supposition of an end being attained, to the antecedent causes that are necessary for its attainment. In this way causal analysis can yield truths about nature that are certain, even though these do not have the absolute necessity that is found in mathematics and metaphysics. This doctrine on necessity and demonstration ex suppositione is not stressed in any of Averroës’s commentaries, to my knowledge, and it does not seem to have been part of the intellectual equipment of the Latin Averroists.7 It certainly was not appreciated by Etienne Tempier, who construed the natural philosophy of the Paris Aristotelians as a type of metaphysics that was incompatible with the Catholic faith. He struck forcibly at the alleged truth and certainty of many theses of the Averroists concerning man and the physical universe in the famous Condemnations of 1270 and 1277.8 As is well known, Aquinas (and Albertus implicitly) came under a shadow at Paris and Oxford as a result of the Condemnations, and the Franciscans quickly challenged the Dominicans on the grounds of their orthodoxy at those centers of learning.

Late Medieval Science Let us take 1277, then, as the point of demarcation for the late Middle Ages. The characteristic note in philosophy and theology for that period, as found in both Scotus and Ockham (though in different ways), was the accent on will as opposed to intellect, which led to a

7. John Case, in fact, in his In universam dialecticam Aristotelis (London: Thomas Vautrollerius typographus, 1584), 178, reproves Averroës himself for not allowing the possibility that the human mind can achieve demonstrative knowledge of any subject matter. Oddly enough, Shapiro does not even mention Case in her study, although he surely was a proponent of certitude for science in the century preceding that of her research. For fuller details, see C. B. Schmitt, John Case and Aristotelianism in Renaissance England (Montreal: McGill-Queen’s University Press, 1983). 8. Edward Grant, ed., A Source Book in Medieval Science (Cambridge, Mass.: Harvard University Press, 1974), 45–50.

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predominance of voluntarism over the intellectualism that had hitherto prevailed. For those interested in late medieval science, Ockham exerted the definitive influence, and so his views merit brief examination. As he saw it, reality itself is a collection of absolute singulars, the distinguishable units of which are substances and qualities. Such singulars depend for their being on the will of God, and the will of God can accomplish anything that does not imply a contradiction. This being so, it is always possible to have one singular without the other. Since an effect is different from its cause, it is likewise possible for God to sustain the effect without its proper cause. The theory of divine omnipotence based on what God can will without contradiction therefore implied a universe radically contingent on the divine will, even to the natures of things themselves. And man’s knowledge of that universe, in that nominalist perspective, could never be more than a de facto association of many singulars. This led inevitably to the questioning of the validity of causal reasoning, and thus of the certitude of demonstration in the Aristotelian mode. In a universe where there is no necessity, and where relations have no reality independent of things themselves, it becomes impossible to establish the truth of causal propositions. Although Ockham wrote a treatise De demonstratione, he did not conceive demonstration as an apodeictic form of reasoning. In the sciences of nature, as a consequence, the best one could hope for would be a highly probable proposition.9 In England, where Ockham’s ideas early took root, “that uncertain feeling” became quite pervasive. Logic, to be sure, flourished, and all the modes of consequentiae and of hypothetical reasoning were investigated in exhaustive detail. But natural philosophy would never yield a conclusion that could give the ecclesiastical authorities cause for alarm. Sophismata and dubitabilia became the stock in trade of those pursuing the science of nature. Working secundum imaginationem,

9. W. A. Wallace, Prelude to Galileo, Boston Studies in the Philosophy of Science, vol. 62 (Dordrecht-Boston: D. Reidel Publishing Company, 1981), 341–48.

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investigators at Merton College, Oxford, explored many of the kinematic properties of moving bodies.10 Yet the extent to which their analyses might be applied to the world of nature was never fully appreciated. Richard Swineshead’s study of the place of an element, De loco elementi, and the various factors that would affect an extended body as its center approached, and then passed, the center of gravity of the universe, is typical in this regard. Indeed, it has been remarked that his calculations of elemental movement were made primarily to show that mathematical techniques are themselves inapplicable to the very motions they were designed to study.11 The nominalism that was pursued at the University of Paris in the fourteenth century owed much to Ockham and the Mertonians. Still, there are two important particulars in which its partisans, Jean Buridan and those associated with him, departed from Ockham and his via moderna. The first was in their understanding of motion and the causality involved in its production, and the second was in their estimation of the truth and certitude to be found in the science of nature.12 Ockham, with a sweep of his mythical razor, had denied that motion was an absolute entity and thus taught that it was not a reality distinct from the body being moved. Since it could not be a new effect, to be consistent with his philosophy it would not require a cause.13 Buridan rejected this line of reasoning, and so initiated a school of thought wherein the causes and effects of local motion were studied, and wherein medieval dynamics, with its doctrine of impetus and its analyses of the forces and resistances affecting the motions of bodies, received its highest state of development. 10. C. A. Wilson, William Heytesbury: Medieval Logic and the Rise of Mathematical Physics (Madison: University of Wisconsin Press, 1960), 25. 11. M. A. Hoskin and A. G. Molland, “Swineshead on Falling Bodies: An Example of Fourteenth-Century Physics,” British Journal for the History of Science 3 (1966): 150–82, esp. 154. 12. Wallace, Prelude to Galileo, 54–55, 344–46. 13. Herman Shapiro, Motion, Time and Place According to William Ockham (St. Bonaventure, N.Y.: Franciscan Institute Publications, 1957), 53.

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attempt to invalidate a science of nature on the basis of “cases that are supernaturally possible,” namely, those invoked in the Condemnation of 1277. Here Buridan returned to the earlier teaching of Albertus Magnus and Aquinas and argued that truth and certitude are attainable in the study of natural things provided demonstrations are made there ex suppositione. The nuance added by Buridan is that such demonstrations presuppose an order of nature that has been willed by God, wherein regularity and order prevail, and wherein a natural truth and certitude are to be found.14 Buridan’s ex suppositione naturae may be seen as a refinement of Aquinas’s ex suppositione finis, for it already is implicit in Aquinas’s writings. Ernest Moody misread Buridan when he saw the expression ex suppositione in his writing and argued that after Buridan “an ineradicable element of hypothesis [was] introduced into the science of nature.”15 Suppositio and hypothesis admittedly mean the same thing, but Ockham used hypothesis to mean that scientific reasoning could achieve no more than probability, whereas Aquinas and Buridan invoked suppositiones precisely to safeguard the truth and certitude of science’s conclusions. It is difficult to assess the overall effect of Buridan’s correctives to Ockham on subsequent commitments to certitude in late medieval science. From what I have read in Nicole Oresme, I sense that he had a sophisticated view of the problem, that he allowed for many possibilities of error and falsehood, but that overall he subscribed to Buridan’s more Thomistic analysis rather than Ockham’s. Perhaps, however, the tactics of Albert of Saxony are more representative of the ways in which later fourteenth-century thinkers got around the problem. In Albert’s time the question whether local motion is something distinct from the object moved and from its place was much discussed, and it 14. Johannes Buridanus, In metaphysicen Aristotelis quaestiones (Paris: Badius, 1518; repr., Frankfurt am Main: Minerva, 1964), fol. 9r. 15. E. A. Moody, Studies in Medieval Philosophy, Science, and Logic (Berkeley: University of California Press, 1975), 156; Wallace, Prelude to Galileo, 230–31, 341–48.

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was customary for nominalists to answer it in the negative and realists in the affirmative. Marsilius of Inghen clearly took the nominalist stance, whereas Buridan took the realist. When Albert came to take up the difficulty in his questions on the Physics, Book III, he straddled the fence in the following way. In Question 6, considering the problem logically, he concluded in favor of the nominalists, while in Question 7, wherein he further admitted “divine cases,” i.e., those that are supernaturally possible, he concluded with the realists. Following logic alone, therefore, he turned out to be a nominalist, whereas “according to truth and to the faith” he professed himself a realist.16 The proliferation of treatises during the fourteenth and fifteenth centuries wherein authors argued theses both secundum viam nominalium and secundum viam realium must have had a disconcerting effect for proponents of the certitude of science. One might interpret it as a continuation of the Averroist notion of “double truth,” but it could equally be regarded as a dilution of the very idea of truth and the substitution of alternative defensible opinions instead. As the fifteenth century wore on, with the invention of printing and the publication of the opera omnia of medieval doctors such as Aquinas and Scotus, the situation was exacerbated even more. Religious orders exerted their influence in the universities, and soon there were not only nominalist chairs but Thomistic and Scotistic chairs as well. With the beginning of the sixteenth century, Jean Mair’s scholastic revival at the University of Paris reflected this eclectic and pluralist situation.17 Augustinians and Franciscans and Dominicans vied with each other in the preparation of manuals. The secular master, Juan de Celaya, who was to exert a marked influence on Domingo de Soto, added a subtitle to most of his treatises, explaining that his questions were

16. Albertus de Saxonia, Acutissime questiones super libros de physica auscultatione (Venice: Domini Octaviani Scoti Modoetiensis, 1516), fols. 36vb–38ra; Wallace, Prelude to Galileo, 68. 17. Hubert Elie, “Quelques maitres de l’université de Paris vers l‘an 1500,” Archives d’histoire doctrinale et littéraire du moyen âge 18 (1950–51): 193–243.

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being presented secundum triplicem viam: beati Thomae, realium, et nominalium.18 Others added to these the realissimi and the variations among the nominalists— the Ockhamists and the followers of Gregory of Rimini. Each school, to be sure, could see its distinctive positions as true and certain, but the overall impression was unmistakable. On many important issues in natural philosophy there was no universal agreement, and thus one could not be certain about any of the propositions being taught.

The Renaissance and Second Scholasticism The dividing line between late medieval and Renaissance science is difficult to draw. With the rediscovery and publication of Greek commentaries on Aristotle, however, one could say that there was a rebirth of learning even in natural philosophy. This, unfortunately, only succeeded in adding another voice to the many already clamoring at the end of the Middle Ages, that, namely, of the Peripatetics who took their truth straight from “the Master of All Who Know.” A more decisive influence came from the mathematicians, and particularly from the Polish astronomer Nicholas Copernicus. The Pythagorean alternative to a geocentric universe, and some of the simplifications it introduced into theories involving eccentrics and epicycles, diverted attention to mathematics as a possible source of truth and certitude regarding the physical universe. Here the disputes between schools overflowed into a larger argument over disciplinary domains: who was better equipped to yield a certain conclusion about the heavens, the philosopher or the mathematician? (I pass over the theologian here, but everyone knew after 1277 that one did so at one’s peril!) The conventional wisdom then was that the mathematical astronomer could do no more than “save the appearances;” it was the philosoph18. E.g., Ioannes de Celaya, Expositio in octo libros phisicorum Aristotelis, cum questionibus . . . secundum triplicem viam beati Thome, realium, et nominalium (Paris: Impressa arte J. de prato et J. le messier, 1517); Wallace, Prelude to Galileo, 71.

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ical astronomer who would have to pass on the natures of the heavenly bodies and the physical causes of their motions.19 Mathematical theories pertained at best to a scientia media and thus could be regarded only as scientia secundum quid, one incapable of generating certitude in the domain of physics.20 An interesting development then took place in the latter part of the sixteenth century, when Peripatetics reacted against the mathematicism of the day in the person of Alessandro Piccolomini. Piccolomini and his disciples wrote a number of treatises on the certitude of the mathematical disciplines (De certitudine mathematicarum disciplinarium) in which they attacked not only the certitude of applied mathematics but that of pure mathematics as well.21 Their contention was that all mathematics failed to meet the rigorous canons of Aristotle’s Posterior Analytics, that it did not demonstrate strictly, that it had no knowledge of causes, and that its conclusions were therefore not certain. This discredited the mathematicians still more in Renaissance Italy, and perhaps explains why much of their work was done outside the universities rather than in collaboration with philosophers who shared their common concerns. Having mentioned the theologians, let me now add a final complicating factor bearing on scientific certitude. The Protestant Reformation by this time was in full flower, and the Catholic CounterReformation had already begun its course. The scholastic revival initiated in Paris at the onset of the sixteenth century now flourished as Second Scholasticism in Italy and on the Iberian Peninsula. Thomistic and Scotistic and nominalist rivalries were as pervasive in theology as they had been in philosophy, only now a more powerful faction was coming into power, the newly established Society of Jesus. Thom19. Pierre Duhem, To Save the Phenomena, trans. E. Doland and C. Maschler (Chicago: University of Chicago Press, 1969). 20. W. A. Wallace, “The Problem of Causality in Galileo’s Science,” Review of Metaphysics 36 (1983): 607–32, esp. 624–25; Prelude to Galileo, 233. 21. G. C. Giacobbe, “Il Commentarium de certitudine mathematicarum disciplinarum di Alessandro Piccolomini, Physis 14 (1972): 162–93. 

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ism had been endorsed by its founder, Ignatius Loyola, but soon that disintegrated into competing schools: Suàrezianism, Molinism, Bañezianism. The Congregatio de auxiliis tried to mediate the disputes between the Dominicans and the Jesuits, and ended by allowing each order to teach its distinctive doctrines on grace and free will without accusing the other of heresy. Thus there had to be some latitude in the certitude accorded to the teachings of dogmatic theology. In moral theology the emerging problems were even more difficult. Probabilism was countenanced in many areas, and rigorous solutions given up in this most delicate field of Catholic teaching.22 All of this could not help but have some influence on the certitude to be expected in Renaissance science. The Jesuit professors at the Collegio Romano, on whose class notes Galileo drew for his own early Latin compositions, present an interesting case history in this regard.23 Disciplinary domains were as jealously guarded at the Collegio as elsewhere, despite the fact that the mathematicians and the philosophers were all Jesuits, while at the same time both sides were aware of the probabilist reasonings of the theologians. The principal mathematician at the Collegio was Christopher Clavius, whose commentary on the Sphere of Sacrobosco was the main text used for teaching astronomy. This work first appeared in 1570 and was revised in 1581, after which there were many more editions and reprintings. Between 1570 and 1581 an important astronomical event occurred— the nova of 1572. Clavius studied the nova carefully, and on its basis introduced two changes into his text that are noteworthy for our purposes. First, after discussing the nova and its position in detail, Clavius remarks in the second edition that the Peripatetics will now have to see how Aristotle’s opinion on the matter of the heavens can be saved.

22. Benjamin Nelson, “The Quest for Certitude and the Books of Scripture, Nature, and Conscience,” in The Nature of Scientific Discovery, ed. Owen Gingerich (Washington, D.C.: Smithsonian Institution Press, 1975), 355–72, followed by a discussion, 372–91. 23. W. A. Wallace, Galileo and His Sources: The Heritage of the Collegio Romano in Galileo’s Science (Princeton: Princeton University Press, 1984), 3–96.

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He goes on to speculate that this is not a fifth essence but rather matter that is changeable, though not as readily changeable as that found in terrestrial bodies. Second, when discussing the order of the heavenly spheres in the 1570 edition, he states simply that the Ptolemaic order assigned by Sacrobosco is true (verum) and that none of the alternative orderings accord with observations. In the second edition he qualifies the statement to read that the Ptolemaic order is truer than the others (veriorem) and more in conformity with the findings of experienced astronomers.24 These statements are cautious, to be sure, but they indicate a changing attitude toward the Aristotelian cosmos that was quickly reflected in the lectures on the De caelo being given by the Jesuit philosophers at the Collegio. They too were aware of the nova of 1572 and admitted that its position beyond the sphere of the moon had been demonstrated.25 What were the resulting implications for teachings on the incorruptibility of the heavens and the matter of which they were composed? Antonius Menu, who taught the De caelo late in the 1570’s, wrote simply: “It seems more probable and according to truth that the heavens are incorruptible by nature, although the contrary does not lack probability because of the authority of its proponents.”26 This is the peripatetic view, only stated now in degrees of probability rather than with certitude. Ludovicus Rugerius, who covered the same matter in 1591, gave a more nuanced response in three conclusions: (1) “It is not yet completely improbable that the heavens are generable and corruptible through mutual transformation with lower bodies”; (2) “Much more probable is it that the heavens are generable and corruptible, but only through substantial transformation with other celestial parts”; and (3) “It is most probable . . . that the heavens 24. W. A. Wallace, “Galileo’s Early Arguments for Geocentrism and His Later Rejection of Them,” in Novita Celesti e Crisi del Sapere, ed. Paolo Galluzzi (Florence: Istituto e Museo di Storia della Scienza, 1983), 31–40. 25. W. A. Wallace, Galileo’s Early Notebooks: The Physical Questions (Notre Dame: University of Notre Dame Press, 1977), 269. 26. Wallace, Galileo’s Early Notebooks, 268.

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are ingenerable and incorruptible, though this cannot be positively demonstrated.”27 Note here the probabilist language of the theologians cutting into the certitude of a conclusion universally accepted by the Peripatetics in the universities of northern Italy. Similar statements can be found in both Menu and Rugerius when discussing the matter of which the heavens are composed. Even on the question of impetus the opposition between the nominalists and the Peripatetics was softened. Menu’s teaching is somewhat representative: it is probable that projectiles are moved by the media through which they pass, he wrote, but it is also probable, and indeed more probable, that projectiles are moved not only by the medium but also by some quality such as a virtus impressa that inheres in them. Good arguments could be offered on both sides, and so one did not need to claim certitude for the nominalists here, even though Menu found their position preferable to that of the Peripatetics.28 A similar reserve characterizes Galileo’s notes on the De caelo, which seem to be based on the lectures of a Jesuit who taught between Menu and Rugerius—probably those of Paulus Valla, the most likely source also of Galileo’s logical questions. On the corruptibility of the heavens Galileo has only two conclusions, though both are supported by elaborate arguments. The first is this: if we speak of the heavens according to nature (and he adds other qualifications also), it is probable that they are corruptible. The second then reads simply: it is more probable that the heavens are incorruptible by nature. 29 Analogous probabilities characterize the ways in which Galileo sees the intelligences to be related to the heavenly bodies of which they were thought to be the movers.30 With this mention of Galileo we come to the threshold of the seventeenth century and the origins of modern science. It goes without 27. Galileo’s Early Notebooks, 268–69. 28. Wallace, Prelude to Galileo, 325–30. 29. Wallace, Galileo’s Early Notebooks, 96 30. Galileo’s Early Notebooks, 97.

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saying that Galileo continued in his later writings to question the certitude of the conclusions presented in Aristotle’s De caelo. But up to the time of his discoveries with the telescope he really had no alternative to put in their place. When he wrote his Letter to Christina of 1615, however, he was already making claims for necessary demonstrations based on evident sense experience as support for the Copernican world system.31 And the new science of motion he proposed in Discorsi of 1638 was one erected on the model of Euclid and Archimedes, wherein scientific certitude was claimed for all its demonstrated propositions. How Galileo came to reassert the truth and certitude of his mathematical physics is more than I can explain in this essay. Elsewhere I have argued that he did so through a rediscovery of the suppositional necessity explained by Albertus and Aquinas in the late thirteenth century.32 This doctrine was preserved, and developed, in Jesuit commentaries on Aristotle’s Posterior Analytics. Especially the teaching on suppositio, and how a demonstration made ex suppositione could yield a certain truth, seems to have appealed to the young Galileo. Other mathematicians of his day, influenced by Piccolomini, were prepared to reject Archimedes’s proof of the law of the balance because it was based on a suppositio that was not rigorously true, namely, that perpendiculars drawn from the ends of the balance would be parallel, whereas they would actually converge at the earth’s center. Commandino, Benedetti, and Guidobaldo del Monte all subscribed to that view. Galileo departed from them, arguing that the suppositio that the lines are parallel need not affect the certitude of the demonstration. Most of his research on motion, in fact, was concerned with experimentally validating the suppositiones on which the principles of uniform

31. J. D. Moss, “Galileo’s Letter to Christina: Some Rhetorical Considerations,” Renaissance Quarterly 36 (1983): 547–76. 32. W. A. Wallace, “Aristotle and Galileo: The Uses of Hupothesis (Suppositio) in Scientific Reasoning,” in Studies in Aristotle, ed. Dominic O’Meara (Washington, D.C.: The Catholic University of America Press, 1981), 47–77.

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motion and of uniformly accelerated motion could be based, so that he could have demonstrations in the science of dynamics paralleling those already worked out by Archimedes in his science of statics.33 In the second volume of my Causality and Scientific Explanation I have attempted to show how Galileo’s ideal, perfected by Descartes, Kepler, and Newton, led to classical mechanics, and its associated planetary astronomy, becoming the science par excellence that would serve as the paradigm for true and certain reasoning down to the end of the nineteenth century.34 If I am correct, the seventeenth century—pace Barbara Shapiro35—was the period during which the certitude of science came to be vigorously asserted. A similar claim, in my view, cannot be made for the science that was practiced in the late Middle Ages and the Renaissance.36 33. Wallace, Galileo and His Sources, 230–61, 284–91, 322–38. 34. W. A. Wallace, Causality and Scientific Explanation (Ann Arbor: University of Michigan Press, 1972–74), 3–128. 35. This does not mean that I deny all validity to her thesis; for a fuller appraisal, see my review of her work in Review of Metaphysics 39 (1985–86): 374–77. 36. This paper was presented at the Annual Meeting of the History of Science Society, held in Norwalk, Connecticut, October 28, 1983.

Part IV

Nature and Her Creator

Chapter Eight Newtonian Antinomies against the Prima Via

Chapter Eight

Newtonian Antinomies against  the  Prima  Via

The proof of God’s existence from motion in the universe, as originally proposed by Aristotle1 and as later presented by St. Thomas,2 was intended to be understood by physical scientists. The terms in which it was couched were technical terms with clearly defined meanings, and their application was straightforward and rigorous. Yet the proof, for all its technical elegance, no longer convinces the scientific mind. By and large, its terminology is unintelligible to modern scientists, and as a consequence the argument is now commonly rejected as having no scientific importance or validity. There are many possible explanations for this enigma, most of them reducible to the patent equivocation in the use of the word “science” through the past three centuries. Prior to the seventeenth century, science was commonly understood as a body of certain and evident knowledge known to be true through causes. Physical or natural science was further considered as having two main parts: a fundamental or generalized part, dealing with the common features of natural things presupposed to other studies, and a specialized part in which detailed investigation was made of the various types of natu-

1. Aristotle, Physics VII. 2. Thomas Aquinas, Summa Theologiae Ia, q. 2, a. 3.

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ral things. The Galilean-Newtonian revolution drastically affected this understanding; it placed the accent on intensive, specialized investigation, minimized the search for causes, and in its place substituted a methodology based largely on mathematical correlations.3 From that time until the present day, the meaning of the term “science” has still not crystallized, but the prevailing modern opinion places the emphasis on specialized investigation using a uniform postulational procedure that engenders only probable knowledge. Thus causality, certitude, and truth are no longer the hallmark of science. Moreover, there is no fundamental or generalized study of physical reality prior to detailed experimental work. Such considerations, if they are thought of at all, are usually relegated to the broad field of philosophy, and they are not regarded as essential to the intellectual equipment of the scientist. The prima via, or the proof of God’s existence from motion, is refractory to the modern mind simply because it is based upon these fundamental, generalized concepts that are no longer considered a part of science and hence are not taught to scientists. And the situation is further complicated by the fact that modern specialized terminology frequently employs the same terms as pre-Galilean science but with more restricted meanings than these terms enjoyed in the traditional fundamental understanding. Thus the modern scientist finds considerable ambiguity in the classical statement of the demonstration, and this constitutes an almost insurmountable barrier to his acceptance of its conclusion. Yet there is a ray of hope for one who would reinstate the prima via to its rightful place as a classical scientific demonstration. Oddly enough, this springs from the very man whose genius distracted later generations from becoming interested in the fundamental science of nature that rigorously establishes the demonstration, namely, Sir Isaac Newton. Being at the beginning of a new line of thought,

3. E. F. Caldin, “Science and the Map of Knowledge,” Blackfriars 36 (1955): 563–69.

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Newton appreciated the terminology of his predecessors and properly formulated his own contribution so as not to be misunderstood by his contemporaries. But, as frequently happens, the scientists who are now most indebted to Newton are generally unacquainted with his original works, and thus have lost contact with this valuable part of his writings. They miss the point of the very title of his main contribution, the Mathematical Principles of Natural Philosophy, possibly because they are unaware of any other principles with which Newton might be contrasting the ones he there proposes. Even worse, in some instances they misrepresent his teachings and use their own misconceptions to argue against the premises of the prima via. This situation has given rise to the so-called Newtonian antinomies against the prima via.4 They are not Newton’s arguments against this classical demonstration, but rather are difficulties that present themselves to those who are acquainted with Newton’s laws of motion and cannot see how these can be reconciled with the analysis of motion presupposed to the proof for God’s existence. Although these antinomies appeal immediately to anyone who has only a rudimentary knowledge of Newtonian mechanics, moreover, they are quite difficult to resolve, and have proved extremely bothersome to philosophers and theologians who teach the prima via to students of modern science. The present study is an attempt to remove these difficulties at their source by evaluating them in the light of Newton’s original doctrine. It aims to rediscover, for those acquainted with the terminology of modern Newtonian physics, the physical import of the celebrated Principia, to show how this work presupposes a fundamental science of nature based on generalized physical principles, and how in the light of these presuppositions answers can still be given to the ba4. R. Garrigou-Lagrange has already considered one such antinomy in an appendix to God: His Existence and His Nature (London: B. Herder. 1986), 2.447–452. More recently, E. T. Whittaker has invoked a Newtonian antinomy to reject the prima via in his Space and Spirit (London: Thomas Nelson and Sons, 1946).

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sic problems Newton raised about the physical world. And in thus removing the apparent difficulties now contained in the Newtonian antinomies, it proposes to insinuate, at least, that the prima via still remains a classical demonstration for scientists, that it is in fact the monumental achievement of physical science for anyone who can learn the generalized concepts on which it is based and rigorously apply them to all he knows with certitude about the physical world. The three antinomies selected for resolution are based upon each of Newton’s three laws of motion. They are directed not only against the conclusion of the prima via, but also against its two basic premises, namely, the motor causality principle which states that whatever is moved is moved by another, and the regress principle which rules out either an infinite series or a re-entrant series of corporeal movers. Thus the first law of motion, which enunciates the principle of inertia, would seem to affirm that the inertia of a body is the sufficient explanation of that body’s motion, and therefore invalidates the principle that whatever is moved is moved by another. Again, one consequent of the second law, which itself seems to be an operational definition of force, mass and acceleration, is the inverse-square law of gravitational attraction. This law would seem to affirm that mutually attracting bodies are the sufficient explanation of gravitational motion, and thus they invalidate the regress principle by invoking a closed chain of moved movers. And finally, the third law of motion, stressing the universality of action and reaction between movers and the moved, would seem to exclude the very possibility of an unmoved incorporeal Mover as being the first cause of motion. More complex antinomies may have occurred to some readers, and others could undoubtedly be excogitated with little effort, but it is believed that the basic difficulties are contained in these three. These also have the advantage that they can be solved to an appreciable extent by reference to Newton’s original writings. From the viewpoint of textual analysis, it matters little in which order these be considered. Their resolution can best be accomplished, however, by first answer-

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ing the antinomy arising from the law of gravitational attraction, then using the concepts developed therein to reply to the antinomy based on the principle of inertia, and finally by resolving the action-reaction antinomy.

FIRST ANTINOMY   In gravitational motion, all bodies mutually attract each other with a force given by the inverse-square law. But this force adequately accounts for gravitational motion without the presence of an extrinsic mover. Therefore the two or more bodies are the mutual cause of each other’s motion, and they form a closed system in which no extrinsic mover is needed, let alone a first unmoved Mover. This antinomy obviously presupposes the reality of gravitational attraction as a physical force that exists outside the mind and is actually the cause of the falling motion otherwise identified as gravitational. Most scientists today will accept this presupposition, for they commonly refer to the pull of gravity as if it were something real, and some even discuss quite seriously the problem of shielding gravitational attraction in some way analogous to that in which magnetic and electrical fields are shielded.5 Whether or not this is a true presupposition, however, is another question. In fact, whether Newton would subscribe to such an understanding of the attraction concept he proposed presents an even more interesting problem, and one that will be fruitful to investigate at the outset in order to prepare for the resolution of this antinomy. Newton’s conception of gravitational attraction can best be understood in terms of the distinction that he made between physical and mathematical principles at the very beginning of his Principia. In the first sentence he states: “I have in this treatise cultivated mathematics as far as it relates to philosophy.”6 He then goes on to outline the 5. The Gravity Research Foundation, New Boston, N.H., has repeatedly offered prizes for the best essay on this subject. 6. I. Newton, Mathematical Principles of Natural Philosophy (Chicago: Encyclopedia Britannica Inc., 1952), 1.

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entire content of the work, and stresses the role that mathematical demonstration will play in the science he is presenting: I consider philosophy rather than arts and write not concerning manual but natural powers, and consider chiefly those things which relate to gravity, levity, elastic force, the resistance of fluids and the like forces, whether attractive or impulsive; and therefore I offer this work as the mathematical principles of philosophy, for the whole burden of philosophy seems to consist in this—from the phenomena of motions to investigate the forces of nature, and then from these forces to demonstrate the other phenomena; and to this end the general propositions in the first and second Books are directed. In the third Book I give an example of this in the explication of the System of the World; for, by the propositions mathematically demonstrated in the former Books, in the third I derive from the celestial phenomena the forces of gravity with which bodies tend to the sun and the several planets. Then, from these forces, by other propositions which are also mathematical I deduce the motions of the planets, the comets, the moon, and the sea.7

Newton’s use here of the term “philosophy” is to be understood in the sense of the term “physics,” as they were used interchangeably in his time. He is quite clear in pointing out that he is concerned with natural phenomena, and not merely with calculations that respect artifacts, such as levers and the like, which were treated mathematically by the ancients. And his mathematical principles are not the abstract principles of pure mathematics; they have an intimate connection with physical reality and are primarily ordered to explaining that reality. He stresses this again in the introduction to the third Book, where he says: In the preceding Books I have laid down the principles of philosophy, principles not philosophical but mathematical: such, namely, as we may build our reasonings upon in philosophical inquiries. These principles are the laws and conditions of certain motions, and powers or forces, which chiefly have respect to philosophy. . . . [It] remains that, from the same principles, I now demonstrate the frame of the System of the World.8 7. Newton, Mathematical Principles of Natural Philosophy, 1–2. 8. Mathematical Principles of Natural Philosophy, 269.

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Thus Newton’s approach to physical reality was not completely physical, nor was it completely mathematical, but it was rather a mixture of the two, and so it would be more proper to designate it as physico-mathematical. Moreover, in his development of this new science, which has with good reason come to be known as mathematical physics, he is not always concerned with purely physical considerations. Since we are interested now in his attitude towards “gravitational attraction,” it will be well to trace here his development of the inverse-square law in an attempt to identify the physical and mathematical elements present in his reasoning process. After stating his definitions and laws of motion, Newton begins immediately to treat of the motions of bodies, and the whole of Book I is devoted to this subject. He begins this treatment, however, not with one body attracting another body in any physical sense, but with the notion of one body alone tending to a mathematical center. The first ten sections are thus devoted to theorems which describe mathematically the motion of such a body, and no reference is made whatsoever to any attracting body that might be regarded as the physical cause of the motion. Then, in the eleventh section, he takes up the motions of bodies tending to each other, and it is only in the twelfth section, where he considers the attractive forces of spherical bodies, that he derives the inverse-square law in the second proposition. It should be obvious from Newton’s procedure that he considered the mathematical aspects of gravitational motion as something that could be derived while abstracting completely from the physical causes of the motion, for otherwise he could not possibly have followed this method of derivation. But the question arises whether he himself actually thought that the “attracting” body was a necessary physical presupposition, or whether the entire derivation could be made rigorously while remaining quite indifferent as to what might be the physical cause of the motion. Or, to put it somewhat more generally, could his new science be developed without necessary reference to physical causes as they might exist in the real world, as long as they

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did not contravene the mathematical principles that successfully describe such motion? Reference to Newton’s original text will again throw light on the matter. At the very outset, in his comments on Definition VIII, he makes quite clear what he intends by the “quantities of forces” to which he will have reference throughout the three Books: These quantities of forces, we may, for the sake of brevity, call by the names of motive, accelerative, and absolute forces; and, for the sake of distinction, consider them with respect to the bodies that tend to the center, to the places of those bodies, and to the center of force to which they tend; that is to say, I refer the motive force to the body as an endeavor or propensity of the whole towards a center, arising from the propensities of the several parts taken together; the accelerative force to the place of the body, as a certain power diffused from the center to all places around that move the bodies that are in them; and the absolute force to the center, as endued with some cause, without which those motive forces would not be propagated through the spaces round about it; whether that cause be some central body . . . or anything else that does not yet appear. For I here design to give only a mathematical notion of those forces, without considering their physical causes and seats.9

The last sentence of the citation gives express indication that Newton himself was abstracting from physical factors involved in all types of motion attributable to such forces. That he also had in mind gravitational “attraction” is beyond all doubt, for he goes on to say: I likewise call attractions and impulses, in the same sense, accelerative and motive; and use the words attraction, impulse or propensity of any sort towards a center, promiscuously, and indifferently, one for another; considering those forces not physically, but mathematically; wherefore the reader is not to imagine that by those words I anywhere take upon me to define the kind, or the manner of any action, the causes or the physical reason thereof, or that I attribute forces, in a true and physical sense, to certain centers (which are only mathematical points); when at any time I happen to speak of centers as attracting, or as endued with attractive powers.10 9. Mathematical Principles of Natural Philosophy, 7. 10. Mathematical Principles of Natural Philosophy, 8.

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This makes it quite clear that centripetal “attraction,” for Newton, was simply a mathematical way of looking at the phenomenon, which in no way was intimately connected with any physical presupposition as to why the phenomenon took place. And he recurs to this theme immediately after deriving the inverse-square law, where he again points out: I here use the word attraction in general for any endeavor whatsoever, made by bodies to approach to each other, whether that endeavor arise from the action of the bodies themselves, as tending to each other or agitating each other by spirits emitted; or whether it arises from the action of the ether or of the air, or of any medium whatever, whether corporeal or incorporeal, in any manner impelling bodies placed therein towards each other. In the same general sense I use the word impulse, not defining in this treatise the species or physical qualities of forces, but investigating the quantities and mathematical proportions of them.11

This was a point that was evidently misunderstood in Newton’s own day, so when he came to write the Optics some years after the Principia, he returned again to the question of gravitational “attraction” at the end of the tract on light, and tried to make his position yet more explicit: How these attractions may be performed I do not here consider. What I call attraction may be performed by impulse, or by some other means unknown to me. I use that word here to signify only in general any force by which bodies tend towards one another, whatsoever be the cause.12

Thus an unprejudiced study of Newton’s presentation of mathematical physics indicates that he thought it quite valid to discuss the mathematical laws and properties of motion, while abstracting completely from the physical factors that are the adequate cause of such motion. Does this mean that in Newton’s mind there were no proper physical causes for the motion, or that these were out of the ambit of scientific consideration?

11. Mathematical Principles of Natural Philosophy, 130–31. 12. I. Newton, Optics (Chicago: Encyclopedia Britannica, 1952), 531.

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least to place it in the realm of meaningless questions? Far from committing himself to such an attitude, Newton frankly states that there must be a cause for gravitational motion; indeed, he should like very much to know what it is, but he has never been able to answer the problem to his own satisfaction, and he does not want to venture an explanation that is purely hypothetical. Thus he states at the end of the Principia, in the General Scholium where he summarizes his views on the physical universe: Hitherto we have explained the phenomena of the heavens and of our sea by the power of gravity, but have not yet assigned the cause of this power. This is certain, that it must proceed from a cause. . . . But hitherto I have not been able to discover the cause of those properties of gravity from phenomena, and I frame no hypotheses.13

The last words cited, hypotheses non fingo, have often been quoted as Newton’s great contribution over that of the scholastic thinkers, but its context seems completely forgotten in the minds of many moderns. The more one studies Newton’s works, the more one becomes convinced that Newton used the “attraction theory” only as a convenient mathematical device for deriving his laws and equations of motion, but that he inclined to the opinion that there was an inherent power in the bodies themselves that caused them to gravitate, and not to be pulled by something outside. This would seem to be confirmed by his method of derivation in the first ten sections of Book I mentioned above, where he starts off initially with the notion of bodies tending towards a center. There are also express indications in his writings that he favored the impulse concept when he was speaking physically, as opposed to mathematically, as witness his statement at the beginning of Section XI of Book I: I shall therefore at present go on to treat of the motion of bodies attracting each other; considering the centripetal forces as attractions; though

13. Newton, Mathematical Principles of Natural Philosophy, 371.

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perhaps in a physical strictness they may more truly be called impulses. But these propositions are to be considered as purely mathematical; and therefore, laying aside all physical considerations, I make use of a familiar way of speaking, to make myself the more easily understood by a mathematical reader.14

Further, when he comes to mention various causes at the physical level, he first names the action of bodies themselves before considering other possibilities.15 He also defines motive force “as an endeavor or propensity of the whole towards a center.”16 Later, when speaking of the motions of planets, he prefers to speak actively rather than passively and mentions, “That all the planets gravitate one towards another, we have proved before.”17 These are not absolutely convincing in themselves, but when we consider them with some comments Newton made in a letter to Professor Bentley in which he expressly rejects the “attraction” concept, it seems that they give the best explanation consistent with his other statements. For Newton wrote to Bentley after the first edition of the Principia: That gravity should be innate, inherent, and essential to matter, so that one body may act upon another at a distance through a vacuum, without the mediation of anything else, by and through which their action and force may be conveyed from one to another, is to me so great an absurdity, that I believe no man, who has in philosophical matters a competent faculty of thinking, can ever fall into it.18

It is true that Newton’s reasoning here is based on his abhorrence of a void, but the overall argument has cogency today in view of the rejection of a Newtonian “ether” on the basis of the Michelson-Morley experiment. The only difficulty in Newton’s mind about attributing to bodies 14. Mathematical Principles of Natural Philosophy, 111. 15. Mathematical Principles of Natural Philosophy, 130. 16. Mathematical Principles of Natural Philosophy, 7. 17. Mathematical Principles of Natural Philosophy, 281. 18. I. Newton, Letter to Bentley, 1692/3, in Correspondence of Sir Isaac Newton and Professor Cotes, ed. J. Edleston (London: J. W. Parker, 1850), 159.

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an inherent power which caused them to gravitate was that such a power, from all the evidence he possessed, was occult, and he had no predilection whatsoever for occult powers. It is interesting in this connection to read Roger Cotes’s implicit answer to this difficulty when he wrote, at Newton’s invitation, the Preface to the second edition of the Principia. He there makes this statement: But shall gravity be therefore called an occult cause, and thrown out of philosophy, because the cause of gravity is occult and not yet discovered? Those who affirm this, should be careful not to fall into an absurdity that may overturn the foundations of philosophy. For causes usually proceed in a continued chain from those that are more compounded to those that are more simple; when we have arrived at the most simple cause we can go no farther. Therefore no mechanical account or explanation of the most simple cause is to be expected or given; for if it could be given, the cause were not the most simple. These most simple causes will you then call occult, and reject them? Then you must reject those that immediately depend upon them, and those which depend upon these last, till philosophy is quite cleared and disencumbered of all causes.19

Cotes here gives implicit preference for the natural impulse explanation for gravitational motion. And this explanation being quite consistent with Newton’s various remarks on the subject, we have excellent reason to reject the “attraction” notion as of mathematical utility but of little physical significance, and to look, therefore, for a proper physical cause for gravitational motion. The foregoing analysis of Newton’s work centers attention on the fact that the use of mathematics in this science can well obscure factors that pertain to physical causality. It is well to insist on this, and to make quite clear what the contribution of mathematics is for Newtonian science, for otherwise there is danger in replacing its physical aspects by an all-consuming mathematicism that confers great exactness and rigor on a description, but is not at all sure about what reality is ultimately described. 19. R. Cotes, preface to Mathematical Principles, 2nd ed. (Chicago: Henry Regnery Co., 1951), xviii.

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The most significant word in the vocabulary of the mathematician is the term “equation.” The use of mathematics in a physical science is immediately directed towards the writing of equations that describe particular classes of phenomena. And this in turn makes it necessary to equate quantities. The only difference between mathematical physics and pure mathematics from the point of view of these quantities is that the former is concerned with quantities that are the result of measurements performable on various physical bodies and their qualities, while the latter is concerned with quantities that are pure numbers. The former considers numbers with a dimensional tag attached, while the latter considers numbers alone. The dimensional specification introduces an additional step into the calculations of the mathematical physicist, for he not only has to be sure that his equations are numerically correct but also that they equate on the score of dimensional analysis. But he still must equate. If mathematics applied to physical problems can produce no equations, it is sterile and does not generate mathematical physics. It is only in terms of equations that the hybrid science becomes intelligible. Now, the peculiar thing about an equation is this: if it does not express a tautology, then the only way it can equal two things that are not identical is by abstracting from certain features that are not common to both. In fact, abstraction must be made from everything that would either disturb the equality, or does not enter into it essentially. An equation that is not a tautology, by the very fact that it is an equation, must of necessity give only a partial account of physical reality. This is not to say that such a partial account may not be an important one; it may well be extremely fruitful and useful in describing the properties and relations that obtain between particular phenomena. But it must abstract from some physical considerations—whether they be known or unknown in the mind of the mathematical physicist is immaterial at this point—it must equate parts, and thus of its nature it gives only a partial account of the physical world. When Newton’s second law is given mathematical formulation,

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for instance, there are only three things that enter the equation: force, mass, and acceleration. Whatever be the physical situation to which it is applied, every physical aspect other than those which can be ascertained by these three measurements is unimportant. More than that, every other aspect must be neglected at the price of disturbing the equality. A boy pulling a sled cannot be equated to the sled. There is no doubt that he is the physical cause of the sled’s motion, and yet there is no way of showing this in the Newtonian equation. All that the equation can say is F equals ma. Granted the motion, whatever be its physical cause, the relation between certain measurable aspects of the bodies involved will be expressed accurately by the equation. But the price of the very writing of the equation is the neglect of some factors that are physically necessary to an understanding of the phenomenon. The question of physical causality is bypassed at the point where mathematical physics begins. If this were all that could be said for modern physics and its knowledge of the physical universe, however, the prima via would be a quite hopeless undertaking. The fact is that recent years have shed light on the inadequacy of a mathematical physics that equates quantities numerically and dimensionally, and then stops at that. Modern scientists are returning to the concept of a mathematical physics that uses its equations as a tool, as a starting point to ask questions about the physical reality that lies beneath the description, which Newton clearly espoused.20 One sign of this is the tendency, in certain quarters, to distinguish between mathematical physics and theoretical physics. According to this conception, the mathematical physicist may well restrict himself to writing equations, to investigating the consequents of certain pos20. Newton, Mathematical Principles of Natural Philosophy, 131: “In mathematics we are to investigate the quantities of forces with their proportions consequent upon any conditions supposed; then, when we enter upon physics, we compare those proportions with the phenomena of Nature, that we may know what conditions of those forces answer to the several kinds of attractive bodies. And this preparation being made, we argue more safely concerning the physical species, causes, and proportions of the forces.”

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tulates and the mathematical formulation of hypothetical constructions, and yet be withal divorced from questions immediately respecting the physical world. He may be two steps closer to that world than the pure mathematician, and one step closer than the applied mathematician who “tailors” equations for him, but he still refrains from passing judgment on the physical reality that lies behind his final results. Not so the theoretical physicist. He now is approaching the classical conception of the integral physicist. He not only knows the final results of the mathematical physicist, but he knows what they mean in terms of the physical world. Mathematics is one of his most powerful tools, but it is only a tool; there are still physical questions that can be asked, and it is his business to find the answers.21 It is to such a theoretical physics, developed in the light of the principles of a generalized physical science already known to Aristotle and St. Thomas, that the solution of the problem of gravitational attraction must be referred.22 The inverse-square law, on the face of it, is powerless to say what is the cause of gravitational motion. Recourse must be had to physical concepts to find the answer, and since Newton himself seems to have inclined to the natural impulse explanation, it offers a convenient concept with which to begin the search. Nature, taken in a strict technical sense, is a principle of motion that exists within a primary unit.23 It is the source from which proceed all movements that are called “natural,” and thus such movements are conceived as originating in some way within the moving body, and not imposed on it completely from without. Natural motions are therefore different from compulsory motions, which are the result solely of extrinsic agents acting on the body.24 21. See W. H. Kane, B. M. Ashley, J. D. Corcoran, R. J. Nogar, Science in Synthesis (River Forest, IL: Albertus Magnus Lyceum for Natural Science, 1953), 36, 37. 22. See Pope Pius XII, “Science and Philosophy,” The Pope Speaks 2 (1955): 113–20. 23. Thomas Aquinas, In II Physicorum Aristotelis, lect. 1; Aristotle, Physics II, ch. 1 (192b22). 24. Compulsory motion is also called violent motion. See Thomas Aquinas, In IV Physicorum Aristotelis, lect. 12; Physics IV, ch. 8 (214b33).

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living things, there is no great difficulty in recognizing a natural motion and distinguishing it from a compulsory motion. If a fish is taken and thrown into a bucket, there cannot be much question that its motion, as it flies in a graceful arc through the air, is not natural for a fish; “thrown” motion is compulsory motion, and it matters little whether the thing thrown be a fish or a baseball, because the cause of the motion is quite clearly from without. And if the fish be seen swimming in an aquarium, there is also no great difficulty in identifying this motion as natural. That is one of the ways you go about identifying fishes and various species of living things; their characteristic motions manifest their natures, and thus have a primary claim to being termed natural.25 Somewhat the same thing may also be said for the motions that proceed from inorganic primary units, particularly when the motions considered are alterations and fundamental changes. For instance, it is natural for radium to break down to lead by radioactive disintegration. The very fact that such a phenomenon is referred to as natural radioactivity is a tacit admission of the validity of this view. But when the problem is raised about the local motion of inorganic bodies, and particularly about gravitational motion, the answer is not so obvious. Is gravitational motion a compulsory motion, something imposed on the body completely from without, or is it a natural motion that proceeds in some way from within the falling body itself? This is the basic issue at stake in the question of gravitational attraction; it must be faced squarely if an answer is to be given in terms of fundamental physical principles. The most simple way to solve the difficulty, of course, is to enumerate the various features of natural motions that are found in more obvious cases, and then to apply them to the case under consideration. If all can be verified of gravitational motion, then there is strong reason for holding that the latter is a natural motion. If, on the 25. See W. H. Kane, “Comment on Dr. Foley’s Paper,” Proceedings of the American Catholic Philosophical Association 26 (1952): 144–46.

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other hand, this motion has nothing in common with other motions that are known to be natural, then the presupposition that it is only a compulsory motion should be favored, and the search started for the compelling agent or the physical causes that properly produce the compulsion. Natural motion can be identified from these conditions that accompany the work of nature: it is from within,26 “spontaneous, uniform in its action,27 and always directed to a definite goal or term.28 Furthermore, the term to which it is directed is characteristic of the particular primary unit having that nature. Moreover, all these conditions are verified in gravitational motion, and thus it should be regarded as a natural motion. Gravitational motion is from within. No matter what extrinsic factors may affect the motion, the single most important cause of the motion is the characteristic of the body that makes it ponderable. We refer to this as its gravity, and measure it by the various operational procedures for determining weight or mass. But there is something within the body that we are measuring, and this is the most fundamental source of its motion. Further, because gravitational motion is from within, it is spontaneous. As soon as the props are taken out from under a heavy object, it immediately and spontaneously falls to the ground. As soon as any massive body is left to its own devices, it immediately and spontaneously seeks its proper place in the physical environment in which it happens to be. There is no sluggishness, no indifference as far as the manifestation of the tendency is concerned. All that is required is the removal of the impediments restraining the tendency, and the material body will unhesitatingly seek a physical place compatible with its nature.

26. See Aquinas, In II Physicorum Aristotelis, lect. 14; Physics II, ch. 8 (199b26). 27. Thomas Aquinas, In VIII Physicorum Aristotelis, lect. 15; Physics VIII, ch. 7 (260a20). 28. Aquinas, In II Physicorum Aristotelis, lect. 4 and 12; Physics II, ch. 8 (198b10).

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of any particular chemical element, to make the case simple, will follow exactly the same path, will fall with exactly the same velocity in a given medium as they seek their natural place. If this were not the case, all of Newtonian physics would have to be rejected immediately. Obviously, the particular details describing the motion will vary for different chemical elements, for different chemical compositions that might characterize various bodies, but given the same type of body it will always follow a characteristic path. Nature acts uniformly unless it is impeded by an outside agent, and this is also seen to be the case in gravitational motion. Finally, gravitational motion is always directed to a definite goal or term that is characteristic of the falling body. This is not to say that every body has an absolute point in empty space to which it tends. The term referred to here is not a mathematical entity, but rather a term that is understood in a physical context. If a gas chamber contained atoms of all the elements in the periodic table, and the atoms were allowed to reach equilibrium at a given temperature, all of them would seek definite levels of stratification characteristic of their particular natures. In fact, that would be one way of sorting out the various elements and classifying them, and has been so used by Aston in his mass spectrograph. Similarly, bodies composed of various elements would seek definite places in any physical environment determined by the proportions of the elements of which they were composed. The term sought in any particular environment is the natural place of the body, and when it is attained, the body comes to rest. This, too, is characteristic of natural motions, for nature is the principle of motion and rest, as has been clearly asserted by Aristotle.29 Thus gravitational motion gives all the indications of being a natural motion. It might be objected at this point that these arguments are convincing enough, but they do not prove that gravitational motion is a 29. Aquinas, In II Physicorum Aristotelis, lect. 1; Physics II, ch. 1 (192b22).

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natural motion in the sense that they remove all doubt, nor do they completely exclude the hypothesis of another body or a corporeal medium acting outside the falling body and causing its motion. The objection is valid, but there is a twofold difficulty involved in it that needs elucidation. First of all, to say that a motion is a natural motion is not to eliminate the need for an efficient cause of that motion. Nature is a principle of motion within the body undergoing motion, but it is a principle in the order of formal or material causality, not in the order of efficient causality. Thus, even a body that is naturally in motion must have an efficient cause of that motion; it must be moved by an agent distinct from itself. This is no less true of motions that proceed from active principles within living organisms than it is of nonliving things having only a passive principle of motion within them. But the mover in the case of a natural motion has to be one that can move the body naturally, i.e., in accordance with its nature. It cannot be a violent agent that leaves no determination to the thing moved by pushing it or pulling it from without in haphazard fashion. Secondly, the identification of the efficient cause of a natural motion is a problem that is considerably more difficult than recognizing that particular motion as natural. But it does not require proof of the naturalness of a motion before it can be discussed. In fact, that any motion is natural cannot be proved in a strict sense; it can only be discovered. Nature is itself such a fundamental principle that there is nothing more fundamental in terms of which it can be demonstrated, and the same thing is true of natural motions. In general, however, when nature is known to be the first principle of motion that proceeds from within a body, the first question that should be asked about any motion is whether or not it can be properly explained by this principle. Hypothetical conjectures about extrinsic movers are all right in their place, but they have no place obscuring the proper order of investigation into the world of nature. That any motion is natural cannot be demonstrated, but it can be recognized, and when the

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available evidence is in its favor, it is quite unscientific to overlook this evidence for a hypothetical mechanical explanation that neglects the most obvious features of the motion.30 Yet for those who remain unconvinced that gravitational motion is a natural motion, it is still possible to argue against this antinomy by questioning the physical reality of gravitational attraction, for this is something that has never been proved. One of the best indications of this is that Newton, who first used the concept, over and over again explains that it is only a mathematical device, to which he sees no reason for assigning a physical reality. If he thought that its physical existence could not be proved, and repeatedly warned against accepting it as a reality, it is foolhardy for his students to urge such a “reality” against the prima via. Moreover, as far as the antinomy itself is concerned, Newton and the founders of mathematical physics would never have subscribed to it. Far from being convinced that the inverse-square law made God unnecessary, they were quite convinced that gravitational motion could only be explained by ultimate reference to God. As one Newtonian scholar has written: He [Newton] points to the necessary existence of some active principle of force which would conserve and compensate lost motion. Newton did not take very seriously the attempt to explain this conservation mechanically, as has been noted above from his letters to Bentley, saying that gravitation must be caused by an agent following certain laws. He is willing to have Cotes refer to the fact that it is the Creator who by his will produces gravitational action. The same references are to be found in the words written by Newton himself, and in the writings of Newton’s best defenders; also Samuel Hosley, the editor of Newton’s Opera, says that the originator and sustainer of gravity is not material but divine and that Newton did not explain his laws of motion in terms of repulsion but in terms of immaterial causes, not perceivable to the sense but manifested to the spirit and effect of God.31 30. Aquinas, In II Physicorum Aristotelis, lect. 1; Physics II, ch. 1 (193a2). 31. A. J. Snow, Matter and Gravity in Newton’s Physical Philosophy (London: Oxford University Press, 1926), 162–63.

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A confirmatory argument in the rejection of gravitational attraction, and one of particular appeal to those who favor facts over the endless multiplication of hypothetical constructions, is the fact that such an attraction has never been shielded. It is all well and good to speak of magnetic and electrical attraction, for these have physical meaning; the influence of a magnet or a charged body can be and has been shielded many times over in the laboratory. This gives indisputable evidence of the physical existence of such attraction. But the remarkable thing is that for all the advances that have been made in every field of physical research in the two and a half centuries since Newton’s Principia first appeared, not the slightest evidence has been obtained of gravitation ever being shielded. This may be due to our appalling ignorance of facts concerning the physical world, it is true, but it is certainly no less likely that it is due to a fundamental misconception of gravitation itself. Further, if any additional proof be needed for those who would identify mathematical concepts with the physical reality they so accurately describe, new developments in theoretical physics also disregard the theory of gravitational attraction. For instance, “least action” concepts as developed by Hamilton can be used to give a very elegant treatment of gravitational phenomena, with no mention of attractive forces. One of Hamilton’s basic notions is that all bodies try to reach a place of least potential energy, and in so doing, seek the path that involves the least work. This is the principle of least action, which Bertrand Russell has named the “law of cosmic laziness.” When the energy equations are written and calculations are made of the paths of falling bodies, for instance, exactly the same results are attained by Hamilton’s method as by the use of Newtonian equations.32 This again reveals the superfluous character of attraction concepts. Another development along the same line, perhaps more startling

32. See A. G. Van Melsen, The Philosophy of Nature (Pittsburgh: Duquesne University Press, 1953), 161.

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in its experimental confirmations, is Einstein’s theory of General Relativity. This theory does not regard gravitational motion as something initiated by a pull extrinsic to the body itself, but rather conceives the whole motion as an “event” in the space-time continuum. A physical evaluation of this theory will not be attempted here; it suffices to note only that its mathematical formulation is made without reference to any attractive forces. And yet calculations made with Einstein’s equations give results that not only approximate Newton’s predictions, but in three now classical experiments give a more accurate description of phenomena.33 The solution to the first antinomy should thus be clear. It is based on a false, or at best, an arbitrarily taken supposition, namely, that gravitational motion is a violent or compulsory motion caused solely by the mechanical pull of another body. A more penetrating analysis of all that is involved in this type of motion reveals that it is properly a natural motion, proceeding from an intrinsic principle within the body. And like all other natural motions, it requires physical premotion by the Author of Nature, either directly or at least through an intrinsically subordinated chain of moved movers, at each instant of its motion.34 It is possible that this causality be exercised instrumentally through some corporeal medium, or even through surrounding physical bodies. But these can never be the adequate efficient cause of gravitational motion, any more than a baseball bat, of and by itself, can be the adequate efficient cause of the motion of a baseball. Moreover, there can be no conflict between this explanation and the methods used by Newton to derive the inverse-square law. This 33. The three experimental verifications offered by Einstein were: (1) the advance of the perihelion of the planet Mercury, (2) the deflection of a beam of light passing the limb of the sun, and (3) the shift of spectral lines in the gravitational field of the sun. See G. Rainich, The Mathematics of Relativity (New York: John Wiley, 1950), 159–67. 34. The details of this proof constitute the positive exposition of the prima via, which can be illustrated and understood on its own merits, quite apart from the peculiar difficulties associated with gravitational motion. See Aquinas, Summa Theologiae Ia, q. 2, a. 3; Summa contra Gentiles I, ch. 13; In VII et VIII Physicorum Aristotelis.

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particular law, as a physico-mathematical relation between various measurable properties following on gravitational motion, abstracts completely from an efficient mover.35 It does not deny the existence of such a mover; it does not reject one mover or even a system of movers. It merely states an equality that is found to obtain when the resulting motion is described mathematically. Therefore, it does not follow that a mutual “attractive force” gives an adequate physical explanation of gravitational motion. The inverse-square law does not dispense with a single mover in an intrinsically subordinated chain, let alone manifest the superfluity of God, and anyone who would speak as though it did is only creating for himself an apparent difficulty.

SECOND ANTINOMY:   According to Newton’s first law of motion, a body in uniform rectilinear motion will continue in that motion indefinitely unless acted upon by an external force. But such a body is sufficiently moved by its own inertia and does not require an external mover. Therefore, it is not true that whatever is moved must be moved by another, and thus the proof for God’s existence based on this principle must be rejected.36 This antinomy is built around the concept of inertia in much the same way as the first antinomy employed the concept of gravitational attraction. In a sense, however, it presents a more straightforward argument. The force of the objection would seem to follow directly from the principle of inertia, enunciated as the first law of motion, and not from a particular interpretation of an equation such as the inverse-square relation. Further, since no equation is mentioned explicitly, it would appear that the distinction between physical and 35. See J. A. Weisheipl, “Natural and Compulsory Movement,” New Scholasticism 29 (1955): 80; also, the two other excellent articles by the same author: “The Concept of Nature,” New Scholasticism 28 (1954): 377–408; and “Space and Gravitation,” New Scholasticism 29 (1955): 175–223. 36. This is basically Whittaker’s rejection of the prima via. See Space and Spirit, 47.

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mathematical principles invoked in the solution of the first antinomy cannot be applied in this case. Finally, the first law of motion is simply stated by Newton at the beginning of his technical exposition of the Principia, with no detailed derivation and with no extended argumentation in its justification. Thus it would appear that he thought it sufficiently obvious and self-evident to be accepted immediately at the beginning of the tract. Therefore, the arguments that were used in the solution of the first antinomy drawn from Newton’s own admissions would not seem to be applicable in this case. These observations highlight the additional difficulties present in the second antinomy, and at the same time point out the main problems that have to be solved before the antinomy can be resolved. As in the preceding solution, the textual approach will serve as a good introduction to these problems, so it will be convenient to begin with a discussion of the first law of motion and the position it occupies in Newton’s Principia. Newton entitled his work, as will be recalled, the Mathematical Principles of Natural Philosophy. Yet he did not write it as a modern textbook with a long list of equations functioning in each derivation. Rather he started out with a few definitions of basic concepts, then stated the three laws of motion and their corollaries, and immediately launched into the various propositions that could be deduced reasonably from these principles and their consequents. Some propositions functioned for him as theorems and lemmas, and others were introduced merely as problems. But all propositions were stated in words; except for an occasional proportion, all his derivations are described in the expositive form of an essay without the mathematical derivations that characterize present-day treatises on mechanics. The point is of historical interest, but it also accents a significant detail. The absence of an explicit mathematical equation does not indicate the absence of a mathematical principle. Because a principle or law is stated in words does not indicate that it is not basically mathematical, or at least founded on mathematical presuppositions.

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Newton stated the first law of motion, which was the very first of his “Mathematical Principles,” in these words: Law I: Every body continues in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed upon it.37

On face value, there is nothing in this statement that would seem to imply that it is a mathematical principle. It should be noted, however, that this law has been preceded in Newton’s text by eight Definitions and one Scholium, though of all the terms mentioned in the law, only one is considered in the definitions, that is, “forces.” Yet this may be of some significance, for Newton does state in Definition VIII: “I here design only to give a mathematical notion of those forces, without considering their physical causes and seats.”38 This may be a clue to the solution, but at best it is only a clue, for the term “forces” does not seem to enter essentially into the statement of the first law. It plays only a negative or accidental role. What the first law states is that without these forces, even mathematically considered, a body will continue in its state of rest or of uniform motion in a right line. The real problem is the first part of the principle of inertia. How is this to be conceived? Is it physico-mathematical or purely physical, and if the former, in what precise sense does mathematics enter into it? This is the key problem involved in the principle of inertia from the viewpoint of a foundational physics, and quite fundamental to the solution of the second antinomy. There can be no doubt that the principle of inertia, as we shall henceforth designate the first law of motion, is not a physico-mathematical principle in the sense that it will ever enter explicitly into an equation of mathematical physics. There is no way of writing it in the form of an equation, and it does not seem to express an equality that could be of any use in any other equation. At best, it tells what can 37. Newton, Mathematical Principles of Natural Philosophy, 14. 38. Mathematical Principles of Natural Philosophy, 8.

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be left out of another equation, and this is hardly a positive contribution. As far as the positive, formal principles that bear directly on the derivation of conclusions of mathematical physics are concerned, the principle of inertia should not be included among them. Yet, the principle itself has some positive content. Moreover, it states what obtains in a limiting case, and thus presupposes the use of a limit concept in its derivation. And since such limit concepts pertain more to mathematical modes of reasoning than to physical ones, the principle of inertia is more physico-mathematical than it is physical. Thus Newton was justified in enumerating it first among the mathematical principles of natural philosophy. As a matter of fact, the concept of a body proceeding in a uniform motion in a straight line to infinity is mentioned by Newton in his explanation of Definition V even before he states it in the first law. In the discussion following this definition, which defines a centripetal force as that by which bodies tend towards a point as to a center, he also gives clear indication of the reasoning which led to the statement of the principle of inertia. He says in part: That force . . . by which the sling continually draws back the stone towards the hand, and retains it in its orbit because it is directed to the hand as the center of the orbit, I call the centripetal force. And the same thing is to be understood of all bodies, revolved in any orbits. They all endeavor to recede from the centers of their orbits; and were it not for the opposition of a contrary force which restrains them to, and detains them in their orbits, which I therefore call centripetal, would fly off in right lines, with an uniform motion. A projectile, if it were not for the force of gravity, would not deviate towards the earth, but would go off from it in a right line and that with an uniform motion, if the resistance of the air was taken away. It is by its gravity that it is drawn aside continually from its rectilinear course, and made to deviate towards the earth more or less, according to the force of its gravity, and the velocity of its motion. The less the gravity is, or the quantity of its matter, or the greater the velocity with which it is projected, the less will it deviate from a rectilinear course, and the farther will it go.39 39. Mathematical Principles of Natural Philosophy, 6.

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Before giving the rest of this citation, it will be well to point out that the last sentence states the empirical basis for the first law, for it states something that can be observed experimentally. It also shows how this empirical basis is to be used in reaching a limit concept, insofar as the approach to the limit is stated as a proportion. The less the gravity or the greater the velocity, Newton notes, the less the deviation from rectilinearity and the farther the projectile will go. This is a true observation as far as it goes, and it sets up the conceptual framework for approaching the limit. Newton continues: If a leaden ball, projected from the top of a mountain by the force of gunpowder, with a given velocity, and in a direction parallel to the horizon, is carried in a curved line to the distance of two miles before it falls to the ground; the same, if the resistance of the air were taken away, with a double or decuple velocity, would fly twice or ten times as far. And by increasing the velocity, we may at pleasure increase the distance to which it might be projected, and diminish the curvature of the line which it might describe, till at last it should fall at the distance of 10, 30 or 90 degrees, or even might go quite round the whole earth before it falls; or lastly, so that it might never fall to the earth, but go forwards into the celestial spaces, and proceed in its motion ad infinitum.40

Here he continues to apply the proportion, increases the velocity at pleasure and at the same time allows the air resistance to go to zero, and thus concludes to the limiting case: the projectile will proceed in its motion in infinitum. This reasoning process is not completely original with Newton; Galileo, in his Discourses on Two New Sciences, had discussed similar situations and had shown how limit concepts could lead to interesting conclusions.41 But Newton’s genius consisted in this: he did not restrict himself to the mathematical proportion involved in approaching the limit, but rather concentrated on the limiting case itself. He stated the limiting case as a general principle for all local motion when he formulated the first law. 40. Mathematical Principles of Natural Philosophy, 6. 41. For example, Galileo, Discourses on Two New Sciences, Third Day, prob. 9, prop. 23, scholium.

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actually a conclusion, an inference drawn from a physico-mathematical approach to a limit, and for this reason is not a purely physical principle but is itself physico-mathematical. A more rigorous statement of the approach to the limit that is actually involved would be this: the distance a projectile will travel in a resistive medium under a given impulse is an inverse function of the resistance of the medium. Similarly, the limiting case might be stated: as the resistance of the medium goes to zero, the distance travelled goes to infinity. Examining the principle of inertia in the light of this analysis, then, it can be seen that it is neither a self-evident principle nor demonstrable. The reason why it is not self-evident is simple enough. It is never found in ordinary experience that a body in uniform motion continues in such motion indefinitely. All the bodies met with in ordinary experience encounter resistive forces in their travel, and sooner or later come to rest. Nor does refined experimentation and research supply any instances where such resistive forces are absent. The best vacuums attainable in well-equipped laboratories are still quite gross, and present-day information about so-called “empty” interstellar space indicates that the rarest matter density that can be expected there is one nuclear particle per cubic centimeter. So it would appear that resistive media are a quite universal phenomenon. But it might be objected that this is to overlook the second half of the principle enunciated explicitly by Newton, that is, “unless it is compelled to change that state (uniform motion) by forces impressed upon it.” When this is taken into account, although it might be conceded that the first part is not evident to sense experience or to laboratory measurement, the entire principle seems evident to reason, to rational analysis. Unfortunately, however, this type of self-evidence must be rejected too. The second half of the statement cannot be taken as confirmatory of the first half, even when rationally considered. When the first half is considered in the light of the second half, all that is left is the statement, made notorious by Eddington, that “every par-

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ticle continues in its state of rest or uniform motion in a straight line, except insofar as it doesn’t.”42 Literally correct, no doubt, but hardly a first principle on which to build a mathematical physics. The principle of inertia is not self-evident, then; furthermore, it cannot be demonstrated, for there is no way of proving that it is true. Another way of saying the same thing is that the principle of inertia is a dialectical principle, and this by reason of the limit concept involved in its verification. The principle, as has already been noted, is an inference from observational data by means of a limit concept. The observational data are certainly true, but the only way in which it may be maintained that the limiting case is also true would be by maintaining that what is verified in the approach to a limit is also verified at the limit itself. The latter statement, however, cannot be maintained, because it is not universally true. There are many instances in mathematics where it is known to be violated. One illustration is the approach of polygon to circle as the number of sides is increased indefinitely. All through the approach to the limit, assuming the simple case where all figures are inscribed in the limiting circle, every figure constructed that has a finite number of sides is a polygon. The limiting case is a figure of a different species; it is no longer a polygon, but a circle. It is not true to say that a polygon is a circle; the difference is as basic and irreducible as that between the discrete and the continuous. In this case, what is verified in the approach to the limit (polygon), is not verified at the limit itself (circle). Now if it is not always true that what is verified during the approach is necessarily verified at the limit, and indeed there are excellent arguments to show that it can never be true,43 then the fact that the observational base for the principle of inertia is true cannot be used to prove, or demonstrate, that the limiting case stated in the principle is also true. Thus it remains that the first law as stated by 42. A. Eddington, The Nature of the Physical World (New York: The Macmillan Company, 1987), 124. 43. See J. Lalor, “The Concept of Limit” (doctoral dissertation, Université Laval, n.d.).

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Newton is neither self-evident nor demonstrable, and as such is not certainly verifiable of physical phenomena in the real world.44 But this does not necessarily derogate from the utility of the principle of inertia as a physico-mathematical principle. What it does indicate is that this principle does not have the broad applicability of a generalized physical principle that would be universally verified in all real motions. Rather, it gives an idealized account of local motion that abstracts from extrinsic factors present in the real world and affecting such motion. And since it abstracts from extrinsic factors acting on real bodies moving in a physical environment, it should not be surprising that it also abstracts from efficient causality influencing the body in its motion. In point of fact, in all observable cases in the real world, an extrinsic mover is needed in order to have a motion that is exactly uniform. The reason is obvious from what has been said above about resistance being present throughout the known universe, and therefore the need for such a mover is quite consistent with the statement of the first law. Resistance is always encountered from objects extrinsic to the thing moved, and to overcome the decelerating effect of this, an extrinsic force will have to continue to be applied to the object being moved. Of course, it is possible to abstract from this resistance, and conceive of a body moving uniformly without reference to its external physical situation. But when one does this, it is very analogous to conceiving of a body at some arbitrary temperature in the real world that maintains this temperature indefinitely despite any changes of temperature occurring around it. It is all well and good to conceive of insulators that suppositionally isolate it from the real world, but all physicists know that such insulators do not exist in practice. Making the supposition eliminates the problem of a heat source to maintain the body at the given temperature, but it does this only in the mind of the physicist. The same thing goes, mutatis mutandis, for idealized local motion.

44. See Weisheipl, “Natural and Compulsory Movement,” 72.

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If one makes a supposition that eliminates thinking about extrinsic movers, then for him they do not exist, but that does not eliminate their necessity in the real world. It might be objected that what has been said here is true enough if one wishes to be a rigorist and speak of motions that are exactly uniform. However, it would seem that Newtonian physics does not attempt to give an exact account of the physical universe, but only an approximate account. Therefore, if the motions of stars and planets are considered, or of projectiles in very rare media, they will actually decelerate slightly, but the resistance is so small that in practice it can be neglected. Thus the motion that is in practice referred to as uniform, though in fact slightly decelerated, does not require an extrinsic mover but is sufficiently accounted for by the inertia of the moving body. The answer to this further difficulty, like the basic answer to the difficulty of gravitational attraction, must be given in terms of a generalized science of nature such as that developed by Aristotle and St. Thomas. In fact, there is a marked similarity between the two cases, as will become apparent in the development below. But there is also a considerable difference and it will be well to make this clear at the outset. Inertial motion is universally taken as opposed to gravitational motion. The latter is usually referred to as “free” or natural motion, while the former is “forced” or compulsory motion. In the strict understanding of natural motion, it is called such because it proceeds from the nature of the body itself, it proceeds in some way from within the body undergoing the motion. Compulsory motion, on the other hand, is imposed from without; it is violent, it is contrary to the natural inclination of the body being moved. The reason why it is recognized as not being a natural motion is that it does not fulfill the conditions mentioned above as associated with all natural motions, that is, it is not from within, nor spontaneous, nor is it uniform in its action, nor does it always tend to the same term characteristic of the particular body. Obviously, if a motion is a composite of gravitational

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and inertial components, care will have to be taken to isolate what comes from nature from what is imposed from without. But assuming, in the spirit of the difficulty that has been proposed, an inertial or compulsory motion in which gravitational tendencies can be neglected, these conditions will also be lacking. The inertial motion does not originate from within, but rather from without. It is not spontaneous, but is initially forced and sluggish. It is not uniform in its action for any particular body, for the same projectile may be thrown fast or slow, it may be rolled or spun, it may be juggled back and forth. And it is not directed to a place determined by the particular body and its physical environment, for it may be directed now up, now down, now in any direction conceivable for a three-dimensional vector. Thus inertial motion is not natural motion. Yet there seems to be something about inertial motion that is similar to natural motion. When a projectile is thrown, it appears that an impulse is imparted to it by the thrower, and impulse further appears to be in some way the source of its motion. Again, once initiated, the motion proceeds in a uniform fashion for that particular impulse, and moreover, it proceeds in a very determined direction. It is true that it does not seek a compatible place in a particular physical environment, but there does not seem to be any doubt of an inherent tendency in a particular direction. And this direction is not necessarily that intended in the mind of the thrower, but appears to be objectively realized in the thing thrown; otherwise, it is extremely difficult to understand how there can be such a thing as poor marksmanship. What is objectively realized does not have the perfectly determined tendency of a nature, but it nonetheless has an inherent tendency sufficient to make the physicist realize that momentum is a vector. These reasons impel us to argue that there is associated with inertial motion an impulse that is analogous to the impulse of gravity found in natural gravitational motion.45 In a sense, this impulse is a 45. See Dominico de Soto, Super octo libros Physicorum Aristotelis Quaestiones (Salamanca: Andreas à Portonariis, 1551), VIII, q. 3, fol. 104v–5v.

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sort of “second nature.” It is not natural as coming from within the body itself. Rather, it is more like a behavior pattern induced in animals from without by training or by continued application of certain stimuli. Still it is different from this, because all material bodies have an immediate susceptibility for the impulse of inertial motion. And further, once it has been imparted to a body, there appears to be no reason to believe that it would not perdure endlessly, unless overcome by something extrinsic encountered in the course of its motion which however is always the case in our experience.46 Now, granted the existence of such an impulse associated with inertial motion, it is important to realize that even this impulse needs an extrinsic mover in order to sustain the motion efficiently. The reason is basically the same as that advanced for an extrinsic mover in natural gravitational motion. Just as the nature itself requires an extrinsic mover, so the “second nature” which is a modification of the nature must be actuated from without. Both are principles in the order of formal or material causality, and both therefore require actuation in the order of efficient causality in order to be continually operative.47 When abstraction is made from such an efficient agent, of course, it is possible to conceive of the impulse itself as an inertia, as some type of explanation of the compulsory motion, and it is possible to speak also of measures of this, such as momentum. Such measures will be useful in accounting for the apparent uniformity of the motion, for estimating the potentiality of the thing moved in originating other motions, etc. But neither inertia nor momentum sufficiently accounts for the entire motion any more than a body’s gravity can completely account for its fall. 46. The precise entitative status of this impulse is disputed among Thomists, as is the subject of its inherence, some maintaining that it is in the medium surrounding the projectile, others that it is in the projectile itself. For a summary of opinions, see A. Rozwadowski, “De malus localis causa proxima secundum principia S. Thomae,” Divus Thomas Piacenza 16 (1989): l04–14; P. Hoenen, Cosmologia, 4th ed. (Rome: Aedes Pontificalis Universitate Gregorianae, 1949), 482–501. Father Weisheipl has a good evaluation of these opinions in “Natural and Compulsory Movement,” 52–61. 47. See Weisheipl, “The Concept of Nature,” 377–408.

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of God, the more one tries to verify this principle, the more one is led to affirm the existence of an infinite Mover. If all the idealized concepts that have been discussed be granted, and the idealized case be considered as physically real, then not only is some extrinsic mover required, but also one of infinite power, and this can only be God. The reason for this is based on the proportionality that must exist between cause and effect. If it be maintained that a finite impulse can impart a motion that will perdure ad infinitum, this is to hold that an infinite effect can proceed from a finite cause.48 Since such a position is untenable, if the principle of inertia in this understanding is to be maintained, it must be held that the cause is finite from the part of the formal cause (the impulse), but infinite from the part of the efficient mover that sustains the motion. And such an infinite efficient mover would be none other than God. Thus the principle itself, taken in the most realistic sense possible, leads to the postulation of a first unmoved Mover. Now, it may come as a surprise to the modern physicist, but this explanation that has been offered is quite consistent with what Newton himself thought about inertial motion. It is true that he does not explicitly mention an extrinsic principle for such motion in his discussions throughout the Principia, apart from what he says generally about God as the universal Mover and to which we will refer in the solution of the third antinomy. But in his animadversions on mechanics that occur at the end of the Optics, he does explicitly clear up any misunderstanding that might exist about his position on inertial motion, quite apart from his reservations on gravitational motion. He states: The vis inertiae is a passive principle by which bodies persist in their motion or rest, receive motion in proportion to the force impressing it, and resist as much as they are resisted. By this principle alone there never 48. See R. Garrigou-Lagrange, God: His Existence and His Nature (London: B. Herder, 1988), 2.447–452.

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could be any motion in the world. Some other principle was necessary for putting bodies into motion; and now they are in motion, some other principle is necessary for conserving the motion.49

A clearer statement could not be made about the necessity of an extrinsic mover, not only at the beginning of inertial motion, but also at every instant throughout that motion. The evidence is thus indisputable that Newton would not have rejected the fundamental principle, “whatever is moved is moved by another,” on the basis of the law he was first to enunciate. The solution to the second antinomy should therefore be clear. The first law of motion and the concept of inertia that it involves state only partial truths. They are not verified of an entire physical reality, but rather abstract from efficient causality and its relation to compulsory motion. Although not explicitly mathematical, they nevertheless are based on a physico-mathematical reasoning process and invoke a limit concept in their verification. Because of the dialectical aspect of the approach to the limit, the principle of inertia cannot be proved to be true in a complete and self-sufficient sense. Nor is it evident either to experiment or to reason. Consequently, it cannot be invoked as a certain argument against the validity of the foundational principle: whatever is moved must be moved by another. Further, looking at the truth contained in the first law from the vantage point we have now attained, it can be seen that the former attains its full stature and most intelligent justification when understood as requiring the continued application of an extrinsic mover. The latter mover’s influence may not be directly measurable, but it is knowable. Although it is not known to modern physicists, moreover, it was known to Newton, the father of their science, who knew better than they the limitations of the principles he first formulated. Far from undermining the motor causality principle, it furnishes yet another instance of its universal verification. The principle still stands, 49. Newton, Optics, 540.

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and along with it the proof for God’s existence from motion in the universe—motion both gravitational, and inertial.

THIRD ANTINOMY  To every action, there must correspond an equal and opposite reaction. But there can be no such interaction between any body and an incorporeal mover. Therefore, it is impossible that motion proceed from an incorporeal mover, and any proof that would terminate with such a mover must be rejected. The third antinomy does not contain difficulties of the magnitude of those presented by the first two. It is not, like them, directed at the fundamental principles which function as the premises of the prima via. Rather, it raises a question about the term of the proof, and this in a general way. It proposes that there can be no such thing as an incorporeal mover, and thus jeopardizes the proof by maintaining that it reaches a nonsensical conclusion.50 The answer to this antinomy, as to the preceding ones, is suggested by Newton’s treatment of the problem in his development of the Principia. Actually, he does not state the action-reaction principle in the very broad and general way in which it is employed in the antinomy, but restricts it specifically to actions where two bodies are involved. His original statement of the third law is this: Law III: To every action there is always opposed an equal reaction: or, the mutual actions of two bodies upon each other are always equal, and directed to contrary parts.51

His explanation of the law also makes clear that he is excepting the case of incorporeal movers from its ambit, for the only illustrations he furnishes in justification of the action-reaction principle involve corporeal movers. Thus he states:

50. The attitude of mind underlying this objection is characteristic of logical positivism and operationalism, both of which would categorize an incorporeal mover as a “meaningless concept.” 51. Newton, Mathematical Principles of Natural Philosophy, 14.

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Whatever draws or presses another is as much drawn or pressed by the other. If you press a stone with your finger, the finger is also pressed by the stone. If a horse draws a stone tied to a rope, the horse (if I may so say) will be equally drawn back towards the stone; for the distended rope, by the same endeavor to relax or unbend itself, will draw the horse as much towards the stone as it does the stone towards the horse, and will obstruct the progress of the one as much as it advances that of the other. If a body impinge upon another, and by its force change the motion of the other, that body also (because of the equality of the mutual pressure) will undergo an equal change, in its own motion, towards the contrary part.52

It is interesting to note here that of the three instances that Newton uses for exemplification of the principle, two concern cases where bodies are in physical contact, and the third is clearly an instance of an intrinsically subordinated instrumental motion, that is, the case of the horse pulling a stone by means of a rope. We shall have occasion to return to this later, but for the moment it will suffice to note that all are concerned with corporeal movers. Now, it may be maintained that Newton restricts himself to corporeal movers in this principle because he is convinced that these are the only type or movers that exist, and so it would be nonsensical to refer to incorporeal movers in his Principia. Or the possibility suggests itself that he himself might have believed in incorporeal movers, but that he did not think they had any place in physical science, and therefore left them out of consideration. Both of these hypotheses, however, are untenable in the light of explicit citations from the great scientist. As to the existence of incorporeal and immaterial entities in the physical universe, he takes the general position that such things do exist. For instance, in discussing his meaning of attraction in one of the texts already referred to, he states: “I here use the word attraction in general for any endeavor whatever . . . whether it arises from the action or the ether or of the air, or of any medium whatever, whether 52. Mathematical Principles of Natural Philosophy, 14.

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corporeal or incorporeal.”53 Again, in a letter to Bentley after the first edition of the Principia had appeared, he mentions: “Gravity must be caused by an agent acting constantly according to certain laws; but whether this agent be material or immaterial, I have left to the consideration of my readers.”54 A person who was convinced that material movers were the only type that existed would never make the allowances explicit in these statements. Beyond this, it is further evident that Newton attributed actual dominion to the supreme Being over all the workings of the physical universe, and this for him also included motion. Insofar as God was the mover and governor or the universe, He also pertained to the realm of physical science. Newton makes these ideas explicit in the General Scholium which he wrote at the end of the third Book of the Principia, where he is at pains to exclude the type of interpretation of his opus which is at the root of the antinomy now under discussion. Some citations which bear this out are the following: It is not to be conceived that mere mechanical causes could give birth to so many regular motions . . . This most beautiful system of the sun, planets, and comets, could only proceed from the counsel and dominion of an intelligent and powerful Being.55 He (God) is utterly void of all body and bodily figure, and can therefore neither be seen, nor heard, nor touched . . . We have ideas of his attributes, but what the real substance of anything is we know not . . . all our notions of God are taken from the ways of mankind by a certain similitude, which, though not perfect, has some likeness, however. And thus much concerning God, to discourse of whom from the appearances of things, does certainly belong to Natural Philosophy.56

The very last sentence indicates the relevance of God to physical science in Newton’s estimation, for his use of the term “natural philosophy” was equivalent to our understanding of physics and astronomy. 53. Mathematical Principles of Natural Philosophy, 130. 54. Newton, Correspondence of Sir Isaac Newton and Professor Cotes, 159. 55.Newton, Mathematical Principles of Natural Philosophy, 369. 56. Mathematical Principles of Natural Philosophy, 370.

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And the citation stating that God moves all things, “yet neither affects the other: God suffers nothing from the motion or bodies, etc.,” supplies his direct answer to the third antinomy. As should be clear now from the distinctions that have been made in the solution of the previous difficulties, the action-reaction principle is a physico-mathematical relation that holds only between quantified bodies that are already being moved by some physical agent. It merely stresses the mathematical symmetry involved in the transmission of mechanical impulses, and this is wholly consistent with what one would expect in terms of more fundamental principles. If bodies are in contact and an impulse is being transmitted, obviously its metrical aspects are the same whether it be looked at from the viewpoint of the transmitter or the receptor. And the same thing is true if a physical case is being considered where a motion is being transmitted by a series of connected instruments. Here, as can be seen on a moment’s reflection, there is specifically only one motion involved. One should therefore not be surprised if its metrical aspects will be the same in each of the transmitting instruments. It is further true that the action-reaction principle, precisely as physico-mathematical, can also be extended to the two-body problem in the case of gravitational motion. For instance, if two bodies in a given physical environment approach each other in seeking their natural places in accordance with the inverse-square law, there is a certain mathematical symmetry about the phenomenon. As far as the mathematics is concerned, it makes no difference whether one is conceived at rest while the other approaches, or the second is at rest while the first approaches, or both approach each other. And if either of the first two cases are to be conceived in terms of “attractive forces,” evidently the latter will manifest the same equality as the motions. Thus the action-reaction principle can be applied to “attractive forces” in gravitational motion, and it will be found to be operationally verifiable. But while this is a valid principle of mathematical physics, it is not true when the total reality is considered; it cannot be taken as

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a strict physical principle of universal validity. The reason is simple enough. If there is a strict equality between agent and receptor, there can be no motion. Nothing dynamically new can proceed from strict equality. One rope, of and by itself, cannot pull another rope. That is the reason Newton, in explaining the third law as cited above, makes a slight excuse for the example of the horse drawing a stone by a rope. He says, “. . . the horse (if I may so say) will be equally drawn back towards the stone . . .” The reason he inserts “if I may so say” is that there is a big difference between the horse and the rope and the stone when all three are considered physically. A rope, of and by itself, cannot pull a horse, but a horse can pull not only the rope but also something tied to it. If abstraction is to be made from this fact for the purposes of noting physico-mathematical equalities, all well and good. But the physical reality contains much more than the physico-mathematical equality. The obvious answer to the third antinomy, then, is that it is based on a misunderstanding of the third law of motion. The physicomathematical character of the action-reaction principle accents the fact that it abstracts from efficient movers considered in their physical totality. It neglects all movers except bodies already in local motion, and then only seeks an equality that is verified of the moving parts. It abstracts from the movers that form the subject matter of the prima via, but it does not reject them. Indeed, it presupposes them, for Newton’s third law of motion, like his other two, has its only solid foundation and ultimate justification in the physical movers which lead their discoverer inexorably to the existence of God. This completes the resolution of the three Newtonian antinomies. Apart from their utility in penetrating the prima via through a more thorough understanding of local motion, they also contain a message for the modern physicist. For it should be clear now that the scope and intent of the science Newton proposed never was clearly grasped by his successors. The many generations of physicists who now are referred to as “classical physicists” concentrated on the physico-

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mathematical aspects of his Principia, to the neglect of the further ordination that Newton made of the new science to discovering true physical causes. Flushed by early successes in predicting the details of many macroscopic phenomena, they saw the physico-mathematical technique for the powerful tool that it was, and then forgot that it was only a tool. Not possessing the traditional foundation in which Newton himself was grounded, they read too much into the father of their science. They took his mathematical principles as the total explanation of physical reality, and were content to stop where he had begun. Needless to say, such men were not prepared for the rise of the new physics. Having slipped into the error of mathematicism, not appreciating the methodological use of mathematics in physical science, their illusions of a facile explanation for the entire gamut of physical experience were quickly dashed to the ground. Later generations of physicists seemingly profited by their mistake, and so began anew. But the pendulum did not swing to center; its momentum carried it to the other extreme. The philosophers of the new physics still failed to grasp the importance of a generalized physical science which could give true and certain knowledge of the universe; they claimed now that nothing could be certain or absolute. They were content to settle for a provisional explanation of reality; hypothetical constructions and mathematical models were the “ultimate” they were willing to concede. Their concern became manifest when the rapid multiplication of postulational systems soon involved them in contradictions, and so they turned to the problem of logical consistency. Here the logical positivists began to have their day, for a super-mathematicism has become the vogue, and this in turn is nothing more than logicism. Amid present confusions as to what is logic and what is mathematics, there are very few scientists who have intelligent notions on the basic question of what is physics. But the question has been raised anew, and there is hope that the present generation of physicists may start to work on the answer. Of all the attempts made so far, the foundational physics of Aristotle and St. Thomas alone gives

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full meaning to the term “physical,” as opposed to “mathematical” and “physico-mathematical.” Newton had sufficient knowledge of this to orient his new science properly at the outset. His sons would do well to return to where he began. Not only will they find there the answer to the nature of their science, but they will learn how such science can lead them to their God.

Chapter Nine Metaphysics and the Existence of God

Chapter Nine

Metaphysics and the Existence  of God

Philosophy thrives on controversy, provided the subject of controversy is clearly defined and permits a direct confrontation of issues. Now, Fr. T. C. O’Brien’s recent book, Metaphysics and the Existence of God (Washington, D.C., 1960), is undoubtedly concerned with a controverted subject in modern scholasticism. In it, the author takes a forthright and unambiguous stand on the place of God in metaphysics, arguing against a number of current positions, among which he enumerates that of Fr. Joseph Owens. Reviewing Fr. O’Brien’s book in the April issue of this journal (pages 250–53), Fr. Owens, it appears to me, misrepresents Fr. O’Brien’s stand on several key points and then fails to take issue with him. I should like to summarize the resulting state of the question, in the hope of provoking further discussion and subsequent clarification. The misrepresentations I detect in Fr. Owens’s review concern the use that Fr. O’Brien makes of a “principle of extension” and a “principle of limitation” in delineating the place of God in metaphysical inquiry, and, connected with this, the latter’s characterization of the subject of metaphysics as being “precisively separated” from matter. Regarding Fr. O’Brien’s “principle of extension,” Fr. Owens interprets Fr. O’Brien to mean that God cannot be considered by this metaphysician except at the very end of his science, or by somehow “extend189

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ing” the metaphysical inquiry to include the principle of its subject. Fr. Owens opposes this by suggesting that the first task of a science should be to investigate the principle of its subject, and then carry out its entire development in light of this principle. Even granted that Fr. O’Brien’s “principle of extension” may be arbitrarily contrived by its author, it does not have the meaning attributed it by Fr. Owens. Fr. O’Brien’s point is merely this: that the metaphysician must first delineate his subject (being, precisively separated), and then use this knowledge to demonstrate the existence and attributes of its principle (God) as a normal part of its scientific elaboration, not as a terminal or extraneous inquiry. The “principle of limitation” utilized by Fr. O’Brien is intimately connected with this point. As he formulates it, metaphysics “considers God not as subject, but as the principle of its subject” (102). Since God, for him, is not the subject, he is at great pains to delineate what he considers the subject to be, namely, being as “precisively separated,” adopting the latter terminology not from St. Thomas’s usage but “for the sake of convenience of expression” (124n60). Fr. Owens, apparently distracted by the terminology, thinks that Fr. O’Brien’s precisive separation of being should mean a complete exclusion of matter and ultimately “the subsistent nature of being.” This is not Fr. O’Brien’s meaning, nor does it square with St. Thomas’s understanding of separatio in his In Boeth. de Trin. IV, 3. For Fr. O’Brien, precisive separation from matter is not exclusion from matter but rather a consideration of being without reference to matter precisely because the former can exist without matter. This, it should be pointed out, has nothing to do with the esse tantum of De Ente, c. 5, with which Fr. Owens tries to connect it. Nor is it a principle of limitation that merely limits “what can be reached by natural philosophy,” as Fr. Owens represents it. Fr. O’Brien, in fact, elaborates in great detail the difference between the natural philosopher’s abstractive treatment and the metaphysician’s separative analysis in his own exposition of the principle and its intended meaning (158–65).

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Possibly because of his difficulty with these two “principles,” Fr. Owens sees a confusion in Fr. O’Brien’s work over the notion of being itself, and suggests two extreme possibilities as to his meaning. First, he attributes to Fr. O’Brien the doctrine that the metaphysician attains being initially “as a kind of supreme universal.” Fr. O’Brien uses this expression, it is true, but not to designate the metaphysician’s view of being; this he rather identifies as the common conception of being first known to all men (165). Then, Fr. Owens suggests a rather complicated alternative in which Fr. O’Brien conceives of being as something in which “an esse existentiae is superadded to an esse essentiae.” This position is likewise mentioned by Fr. O’Brien, only to be expressly repudiated by him when he argues against the peculiar interpretation this gives to the prima via as expounded by Fr. Gerard Smith and Fr. Owens himself (255–59). Fr. O’Brien’s masterly exposition of St. Thomas’s Quodl. IX, 2, 2 and related texts, in this connection, would appear to leave little doubt that his notion of being is not only profound but quite Thomistic. Fr. Owens’s distortion of these elements in Fr. O’Brien’s work has two serious consequences. One is that it misrepresents Fr. O’Brien’s teaching, and thus gives a biased and unfair view of his book to those who read the review. The other is that it obscures the basic issue at stake in the controversy. The Gilsonian school has insisted that the subject of metaphysics is existential being, immediately grasped by judgment as the act of sensible things, caused by God as ipsum esse, and therefore only to be understood in the light of God as its principle (“I am Who am”). Fr. O’Brien, analyzing scholastic teaching from the earliest commentators of St. Thomas to the present, argues that this is not the metaphysical doctrine of St. Thomas. According to Fr. O’Brien, being as existential act, immediately grasped by judgment, is not the subject of Thomistic metaphysics; therefore, there is no way of attaining ipsum esse as the principle of that subject directly through the quinque viae. The latter, moreover, do not uniformly attain God as ipsum esse

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subsistens, and thus the Gilsonian position errs on two counts: it misconstrues not only the subject of metaphysics but also the particular relationship of the existence of God to a scientific elaboration of that subject. This seems to me to be the basic issue. Fr. Owens, however, does not deign to discuss it. He surprisingly disavows that the Gilsonian school is “a school of particular doctrinal interpretation,” defending it merely as one whose preoccupation is “to analyze each text in its proper setting.” Yet Fr. O’Brien has attacked Gilson and his followers precisely on this point, citing their misuse of the following Thomistic texts: Summa cont. Gent. II, 6 (83); De Pot. III, 3 (201–4); Comp. Theol., 68 (250); In IX Meta., 3, nn. 1805–1806 (252); De Pot. III, 5; and Comp. Theol., 3, 6, 11 (253). Is Fr. Owens’s failure to respond to such criticism merely an oversight, or may it be interpreted as a tacit admission of defeat? Or is the issue adequately resolved by Fr. Owens’s extolling Gilson as “the master of the historical approach to philosophical texts” and denigrating Fr. O’Brien as being somewhat “dogmatic” in his exposition? I do not presume to answer these questions. I merely suggest the possibility that Fr. O’Brien may have given the scholarly world a definitive treatment of the particular problem on which he wrote. If such be the case, then Fr. Owens’s dismissal of the book as a “travail d’approche” does more than an injustice to Fr. O’Brien. It obscures an issue on which many Thomistic scholars would like to be further enlightened.

Chapter Ten The Cosmological Argument: A Reappraisal

Chapter Ten

The Cosmological Argument A Reappraisal

Philosophers have always been interested in what may be referred to as “theistic proofs,” i.e., rational arguments for the existence of God. This interest continues in the present day, but whereas in the past it was accompanied by an acceptance and, at times, by an energetic defense of the validity of such proofs, in the present the interest has turned to skeptical refutation, if not to morbid interment as a part of the “Death of God” ritual. Wallace Matson’s The Existence of God1 is such a vicious attack that one may well ponder over the militancy of his atheism, but Anthony Kenny’s recent work, The Five Ways,2 seems to have a different inspiration entirely. This is the work of a man who regards belief in a divine revelation as reasonable only if knowledge of God’s existence is possible, who has sought such rational justification for faith in the five ways of Aquinas, but who rejects all of these as lacking in probative value. Kenny’s argument is involved and worked out in detail for the five proofs individually, but in essence it reduces to this, that the proofs are too embedded in a cosmology that is medieval and cannot withstand modern critique.

1. Wallace Matson, The Existence of God (Ithaca: Cornell University Press, 1965). 2. Anthony Kenny, The Five Ways (London: Routledge & Keegan Paul, 1969).

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that seems to have inspired Anthony Kenny’s book. There are many usages of the term “cosmological argument,” and I do not intend to discuss all of them here.3 For one, I am not interested in the Kantian usage, which exhibits much the a priori character of an ontological argument. Rather, I am concerned with demonstrations that purport to proceed a posteriori, from effects that are manifest or discernible in the cosmos, to a transcendent cause. Even here, however, I must be more limited in my approach, for of the five ways of Aquinas only four are generally termed “cosmological,” and of these the major part of what I say will be concerned with the first, or prima via, the argument, namely, from motion. In the proof ex motu, the major difficulty is that offered by the motor causality principle, omne quod movetur ab aliquo movetur, on which a considerable literature has recently developed.4 The more popular justification of this principle among scholastics is that used by Aquinas in his Summa Theologiae, where he employs the act-potency dichotomy in its proof.5 While metaphysical in character, and of the widest possible extension for theological purposes, this particular proof does little to illumine the causality involved in local motion, a type of motion which perforce holds the greatest interest for cosmologists. Moreover, when philosophers of science permit themselves to speak of the causes of local motion, they commonly think in terms of forces, or energy, or mass-energy, and the ontological referents of these terms prove quite difficult to identify. Indeed, Max Jammer concludes his scholarly Concepts of Force on the note that force concepts are commonly employed in physics to cover up a basic ignorance of 3. For details, see Donald R. Burrill, ed., The Cosmological Arguments: A Spectrum of Opinion (New York: Doubleday Anchor, 1967). 4. See Solomon Pines, “Omne quod movetur necesse est ab aliquo moveri: A Refutation of Galen by Alexander of Aphrodisias and the Theory of Motion,” Isis 52 (1961): 21–54; J. A. Weisheipl, “The Principle Omne quod movetur ab alio movetur in Medieval Physics,” Isis 56 (1965): 26–45; Nikolaus Lobkowicz, “Quidquid Movetur ab Alia Movetur,” New Scholasticism 42 (1968): 401–21, and the reply to this by J. A. Weisheipl, 422–32. 5. Thomas Aquinas, Summa Theologiae, Ia, q. 2, a. 3.

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mechanical processes, that they are similar to logical entities, like the middle terms of syllogisms that cancel out in the final conclusion.6 If one explains this difficulty of modern scientists with force concepts in terms of the Humean critique of causality, the omne quod movetur principle becomes even more difficult to justify and the argument from motion appears quite untenable in the light of modern science.

The Argument in Physics VII, 1 There is, however, another move open to those who read Aquinas in search of a justification for the motor causality principle, particularly in the context of the need for a mover in cases involving local motion. This consists in examining Aquinas’s commentary on the seventh book of Aristotle’s Physics, where Aristotle gives his own cosmological proof of the motor causality principle—a proof that Aquinas employs explicitly in the Summa contra Gentiles and implicitly in the Compendium theologiae, with the understanding that this is the most obvious and efficacious, one that cannot be withstood.7 And while he maintains that the overall thrust of the argument ex motu is still a posteriori, Aquinas asserts that Aristotle’s proof in the seventh book of the Physics of the disputed premise, omne quod movetur, is actually a demonstration propter quid. It is because of this remarkable statement that I will devote the major portion of this paper to an examination of this argument in Physics VII. I shall attempt to establish that Aquinas is correct in his assessment, that the demonstration is truly propter quid, and that oddly enough it is made not through efficient causality but rather through material causality. If these points can be established, some interesting consequences follow that shed light on the cosmological argument, and particularly on the criticisms that have been advanced in the light of modern science. 6. Max Jammer, Concepts of Force (Cambridge, Mass.: Harvard University Press, 1957), 241–64. 7. Thomas Aquinas, Summa contra Gentiles I, ch. 13; Compendium theologiae I, ch. 3–4.

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rized as follows.8 It seems obvious that everything in motion is necessarily moved by something. Yet there are cases where the source of motion seems to be within the object moved, and thus the possibility arises that the object moves itself. If it can be shown, however, that the object rests because some other thing rests, this will count as evidence that the object is not moved primarily and essentially by itself, but is being moved by another thing. So, let the object moved be a body, AB, and since as a body it is divisible, let it be divided at C. Now assume that the part CB rests, and then the whole AB must rest also. If AB does not rest, then assume that it is in motion. In this case, if part CB continues to rest it is possible that part AC be in motion. Should this be so, however, AB could not be in motion primarily and essentially, although it might be moved through a part or only accidentally. Since what is of concern here, however, is an object that is in motion primarily and essentially, in this respect it must be held that the whole AB rests at the rest of another, namely, its part CB. Therefore, it is being moved by another. It should be noted that the argument is perfectly general, since every body that is in motion is divisible, and if a part is resting, then the whole must be resting too. Therefore, everything in local motion is necessarily moved by something. This argument is analyzed briefly by Anthony Kenny, and he rejects it as having no probative force whatever.9 He is not alone in this, however, since the argument has proved troublesome to practically all commentators and through the centuries has provoked a whole series of arguments and counter-arguments in its refutation and defense. Since these prove more illuminating than Kenny’s somewhat abrupt dismissal of the demonstration, let us now turn to their examination.

8. Aristotle, Physics VII, ch. 1 (241b24–242b19); the best English translation is that of H. G. Apostle, Aristotle’s Physics (Bloomington: Indiana University Press, 1969), 127–28. 9. Kenny, The Five Ways, 19.

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Evaluations of the Early Commentators The first to attack this Aristotelian proof was Galen of Pergamon, the great physician, who was generally sympathetic to Aristotle and his methodology but diverged from him on several important matters.10 This particular proof is one. Galen agrees with Aristotle in considering the case of an object AB that is in motion essentially, where the source of motion is within the thing, and where it is not being moved by one part moving the other. Galen understands these conditions as applicable only to one of the first simple bodies, or elements, where all the parts are similar and not other than the whole.11 In such an understanding, Aristotle’s proof is based on an impossibility, since one cannot even conceive that the whole move and a part be at rest. This would be equivalent, for Galen, to the whole moving and not moving at the same time. Therefore, Galen concludes, the proof is to be rejected as “most ignorant and remote from what is correct to a degree unimaginable.”12 The exact nature of this refutation by Galen has been unknown for centuries, but has recently come to light through the discovery of two Arabic manuscripts whose English translations became available in 1961 and 1969.13 When pieced together, they enable us to reconstruct Galen’s argument accurately, although not precisely in the form in which he first presented it. The source turns out to be a treatise composed by a man who studied Aristotle with Galen under a common teacher, Herminus, and who is no other than Alexander of 10. See Nicholas Rescher and Michael E. Marmura, The Refutation by Alexander of Aphrodisias of Galen’s ‘Treatise on the Theory of Motion,’ translated from the medieval Arabic version, with an introduction, notes, and an edition of the Arabic text (Islamabad, Pakistan: Islamic Research Institute, [1969]). Rescher and Marmura reconstruct Galen’s arguments from explicit citations of his text by Alexander of Aphrodisias. 11. Rescher and Marmura, The Refutation by Alexander of Aphrodisias, 34. 12. The Refutation by Alexander of Aphrodisias, 18. 13. The first manuscript is analyzed by Solomon Pines in the article cited in note 4 above; the second manuscript, and how it relates to the first, is described by Rescher and Marmura, The Refutation by Alexander of Aphrodisias, 3–6.

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Aphrodisias. The treatise seems not to be a part of Alexander’s lost commentary on the Physics of Aristotle but rather a polemical work directed specifically against Galen, and devoted to a lengthy discussion of the proof in question.14 Alexander defends Aristotle’s argumentation, although he presents it as dialectical and not as strictly demonstrative for all the cases to which it might be applied. In Alexander’s analysis, it is not Aristotle but Galen who is ignorant, because he failed to understand the argument in the first place. An object AB, according to Alexander, can be in motion essentially (per se) whether it is moved by a source outside of it or by a source within itself. In the latter case, the source within may be viewed as a motive force, and then it is “something else” apart from the object moved. The two simplest cases are an elemental body, which is moved by an inclination within, its heaviness, and an animal, which is moved by its soul.15 In the broader context furnished by these examples, Alexander proceeds to explain the sense of Aristotle’s dictum that everything in motion is necessarily moved by another thing. The understanding of “another thing” in this statement must be different for the various cases enumerated. When the source of motion is outside the object that moves, then the “another thing” is clearly the cause of the motion of the object, and if the object moves, both the whole object and all of its parts move with it; if it rests, both whole and parts rest at the same time. In the case where the source of motion is within, however, the “another thing” to which Aristotle has reference is the cause of the object’s motion, correctly enough, but this is not the part that happens either to move or be at rest while the object itself moves. Galen is wrong in identifying the part with the whole or the whole with the part, and in trying to interpret the part as the active source, or cause, of the motion. Not every part of an animal stops when the animal

14. Rescher and Marmura, The Refutation by Alexander of Aphrodisias, 1–14. 15. The Refutation by Alexander of Aphrodisias, 15–16.

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stops essentially (per se), nor does every part move necessarily when the whole moves. Thus it is possible to speak of the whole stopping when some “other thing” stops, and to understand this “other thing” as a part of the whole. So understood, Aristotle’s argument is quite valid. As long as an object has parts, it cannot be moved primarily and essentially by itself, but must be moved by another thing. The alternate motion and rest of its parts are not necessary concomitants of its own motion, but their very separability from the motion of the whole indicates to us that the object is not moved primarily and essentially by itself. The object AB, is moved by “another thing,” which is not, as Galen thought, the part CB, but rather a “motive force” or a “soul,” and this is not to be identified with either CB or AB.16 Alexander’s point is made in the context of Aristotle’s dictum, “Everything in motion is necessarily moved by something,” but it is more readily seen in his explanation of the principle Aristotle uses to manifest this, namely, “If an object stops because some other thing stops, it is being moved by another thing.” In this latter statement, the two similar expressions, “other thing” and “another thing,” have the same referent when the source of the motion is outside the object moved, and in this case it is the cause of the motion, whereas they have different referents when the source of the motion is within. Thus, in the cases just explained, “other thing” refers to a part of the whole, whereas “another thing” refers to the cause or source of the movement. For objects moved from within, therefore, Alexander understands this statement to mean that when a whole object comes to rest because a part comes to rest, the whole is being moved, not by the part, but by the soul in the case of an animal and by heaviness in the case of the elemental body. Therefore, for him, each of the following statements is true: (1) a whole is not moved essentially if it is moved by a part; (2) a whole can be moved essentially if the mover is not a part but is external to the body in some way; and (3) a whole stops essentially 16. The Refutation by Alexander of Aphrodisias, 19–21, 26–28.

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when a part stops, which is itself an indication that it is moved either by a soul or by a motive force such as gravity.17 Alexander’s argument is diffuse and repetitive, and even when available to later commentators did not elicit complete assent. Themistius, for example, apparently found the argument difficult to understand and bypassed it completely. Simplicius, on the other hand, while noting Themistius’s tactic, has too great a respect for both Aristotle and Alexander to gloss over their words without comment.18 He does note, however, that for Alexander the argument is essentially dialectical, and with this he agrees, but because Alexander’s argument is “obscure and involved,” he proceeds to exhibit his own “understanding of this for those who are seekers after truth.”19 This attempt, however, proves disappointing, for while Simplicius is definitely opposed to “that wearisome man,” Galen, he does little more than reformulate Alexander’s argument in stricter logical form.20 The next commentator whose evaluation of the argument we shall consider is Avicenna, who treats it briefly in his Sufficientia.21 More heterodox in his Aristotelianism than his predecessors, Avicenna favors Galen over his adversaries and stresses the element of impossibility involved in the conditions with which Aristotle surrounds his argument. In essence, as Avicenna understands it, Aristotle is using an impossible antecedent to deduce an impossible consequent. He himself feels that arguments of this type must be established from the way things actually are in nature, and therefore, while conceding a logical force to the argument, denies it any physical validity in establishing the motor causality principle.22 17. The Refutation by Alexander of Aphrodisias, 49–51. 18. Simplicius, Commentaria in octo libros Aristotelis . . . de physico auditu . . . (Venice: Hieronymus Scotus, 1546), VII, comm. 2, fol. 38. 19. Simplicius, Commentaria in octo libros, fol. 38rb. 20. Commentaria in octo libros, fol. 38ra. 21. Avicenna, Auicene perhypatetici philosophi . . . Sufficientia (Venice: Bonetus Locatellus, 1508), II, ch. 1, fol. 23v–24v. 22. This interpretation is followed by W. D. Ross, Aristotle’s Physics (Oxford: Clarendon Press, 1936), 669, and by Kenny, The Five Ways, 19; neither, however, mentions Avicenna.

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At this point the score is evened up. Alexander of Aphrodisias and Simplicius regard Aristotle’s proof as valid but dialectical, whereas Galen and Avicenna regard it as invalid altogether. With this state of affairs, it is somewhat surprising that the next three commentators we will consider, Averroës, Aquinas, and Nifo, all treating the argument at great length, come to the conclusion that it is a true demonstration, and in the case of Aquinas and Nifo, that it may even be regarded as a demonstration propter quid.

Demonstrative Character of the Proof Averroës’s commentary on this passage is important on two counts: first, it examines the modes of impossibility that are associated with the argument, extending the example to the more difficult case of celestial movements in addition to terrestrial movements, and showing how even in this context Galen and Avicenna have missed the point of the proof; and second, it examines the probative force of the argument and concludes that it is a demonstration signi though not simpliciter and propter quid.23 The significance of the move to the heavenly bodies, as noted in the first count, is that for Averroës the souls of animals are divisible, or have parts in a certain way, whereas the soul of the heavens, conceived after the fashion of Plato’s anima mundi, is completely indivisible and thus has no parts whatsoever. When one applies to celestial movements Aristotle’s argument that if the whole stops because some part stops it must be moved by another thing, and understands the term “whole” to refer to the heavens, then the argument is involved in a multitude of impossibilities. One cannot say that the heavenly body as a whole comes to rest, since for Aristotle this is impossible, nor can one speak of the “rest of a part,” 23. Averroës, Physica cum commentario Averrois (Padua: Laurentius Canozius, 1472– 1475), VII, comm. 1–3. For John of St. Thomas’s explanation of Averroës’s terminology, see The Material Logic of John of St. Thomas: Basic Treatises, trans. Y. Simon, J. J. Glanville, and G. D. Hollen Horst (Chicago: University of Chicago Press, 1955), 495–500.

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for this cannot be a part of the heavens, which as has just been said never rest, nor can it be a part of Plato’s anima mundi, because this is indivisible and has no part. Nonetheless, even though antecedent and consequent are impossible, the consequence or illation between them is not impossible, and since this is what carries the burden of the argument in a hypothetical reductio ad absurdum, Aristotle’s argument is still valid. As Averroës sees it, the consequence is similar to that in the statement, “If a stone flies, it has wings”; although it is impossible that a stone fly, or that it have wings, there is nothing wrong with the illation between these statements, being that of what we now call a counterfactual conditional.24 With regard to the second count, relating to the character of the proof, Averroës is not completely clear as to why the argument is only signi, but his reason is probably that pointed out by Nifo in his exposition of Averroës’s text.25 The argument proves a cause of motion from the rest of a part in the object moved, or conversely, it argues from the rest of the whole to the cause of the motion of a part. Now rest is not the cause of motion, nor is motion the cause of rest. Therefore, the argument does not proceed on the basis of causal analysis but rather on the basis of certain signs that indicate a cause being at work. In this understanding, “cause” is taken to mean an efficient cause, and in this sense the argument is not even a priori, not to say propter quid. Like Averroës, Thomas Aquinas has a lengthy commentary on this argument, where he manifests an acquaintance with the objections of Galen and Avicenna, and gives his own support to the resolutions offered by Averroës.26 The latter, according to Aquinas, holds “that a conditional can be true when the antecedent is impossible and the consequent is impossible.” This is correct, and Aquinas goes on to explain why: 24. Averroës, Physica cum commentario Averrois, comm. 2. 25. Augustinus Niphus, Aristotelis physicarum acroasum . . . (Venice: Bonetus Locatellus, 1508), VII, fol. 185vb. 26. Thomas Aquinas, In octo libros physicorum Aristotelis expositio (Rome: Marietti, 1954), VII, lect. 1, 449–51.

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For example, if man is an ass he is an irrational animal. It must be granted, therefore, that if a mobile object moves itself, it is impossible for either the whole or a part to be at rest, just as it is impossible that fire is not hot because it is the cause of its own heat. Hence this conditional is true: “If a part of a mobile object that moves itself is at rest, then the whole is at rest.” Moreover, if Aristotle’s words are weighed carefully, he never uses the resting of a part except in an expression having the force of a conditional proposition. For he does not say, “CB is at rest.” Rather he says, “If CB is at rest, then AB must be at rest.” And again, “When a part is at rest, the whole is at rest.” And from this true conditional, Aristotle demonstrates the proposition.27

While agreeing thus far with Averroës, Aquinas chooses to depart from the commentator on his evaluation of the force of the argument. He continues: But Averroës says that this demonstration is not simpliciter but that it is a demonstration signi or demonstration quia wherein such conditionals are used. This answer is reliable insofar as Averroës is speaking about the truth of the conditional. But it seems that it must be said that the demonstration is not quia but propter quid. For it contains the reason why it is impossible for a mobile object to move itself.28 To see this it must be understood that a thing’s moving of itself is nothing other than its being the cause of its own motion. That which is itself the cause of something must possess that something primarily. For that which is primary in any genus is the cause of the things that come afterward. Thus fire, which is the cause of heat for itself and for others, is the primary hot object. However, Aristotle has shown in Book Six that there is no primary, or first, in motion, whether this be taken on the part of time, or of magnitude, or of the mobile object itself, because of their divisibility. Therefore there cannot be discovered anything primary whose motion does not depend on something prior. For the motion of a whole depends on the motion of its parts and is divided into them, as was proved in Book Six. Therefore, Aristotle thus shows the reason why no mobile object moves itself. For there cannot be a first mobile object 27. Aquinas, In octo libros physicorum Aristotelis, VII, lect. 1, 451n889; the English translation in Commentary on Aristotle’s Physics, ed. R. J. Blackwell et al. (New Haven: Yale University Press, 1963), 424, is defective because the translation of the Latin conditionalis is given as “condition,” whereas it should be rendered as “conditional.” 28. In octo libros physicorum Aristotelis, VII, lect. 1, 451n889.

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whose motion does not depend on its parts; just as if I were to show that a divisible thing cannot be the first being because the being of whatever is divisible depends on its parts. And thus this conditional is true: “If a part is not moved, the whole is not moved,” just as this conditional is true, “If a part is not, the whole is not.”29

It is obvious from this text that Aquinas discerns in Aristotle’s reasoning a causal argument, but this argument is not made through efficient causality. Rather, it is based on a necessity that arises when the parts are considered in relation to the whole, and since in this case the parts are really the matter of the whole, the causality involved is that of a material cause.30 This point, as we shall indicate shortly, is of some importance in evaluating present-day forms of the cosmological argument, for it seems to be completely over­looked in all contemporary analyses. Before proceeding to this, however, brief notice should be given to the commentary of Agostino Nifo on this difficult passage in Aristotle.31 As was his custom, Nifo comments not only on Aristotle but on Averroës’s commentary as well, and takes into account also the commentaries of Aquinas and others. His, therefore, is one of the most complete expositions of this text, and worthy of close examination. Space does not permit that here, however, and thus we must be content with a single observation. Nifo notes that in the original text Aristotle first proposes a whole AB whose source of motion may be inside it or outside it, and that it is only the former case that presents difficulty, for here it seems that AB could move itself. To analyze this more troublesome case, Aristotle ceases to talk for the moment about a whole AB that is divided at C, and speaks instead of another whole, presumably that of an animal, which he designates DEF. In this example, Nifo understands F to be the body of the animal, E to be its heart, and D to be its soul. Then the animal is moved by a part, i.e., the 29. In octo libros physicorum Aristotelis, VII, lect. 1, 451n889. 30. In octo libros physicorum Aristotelis, II, lect. 5, 93n183. 31. Niphus, Aristotelis physicarum acroasum . . . , fol. 184v–86r.

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remainder of the body is moved by the heart, and that part is moved in turn by something else, i.e., by another part, the soul.32 There is a difference, however, between part E (the heart) and part D (the soul), because while E is a quantitative part and thus is integrally involved in the movement of the whole, D is more properly said to be a qualitative part, and does not enter into the movement of the whole in the same fashion. This interpretation enables Nifo to make sense out of Aristotle’s statement, “If the whole stops because some other thing,” namely, a part, “stops, it must be moved by some other thing,” also a part, but not the same part. In other words, if the whole stops because a quantitative part stops, this can be an indication that the whole is moved by another part, i.e., a qualitative part such as a soul. In this case it cannot move itself primarily and essentially.33

Contemporary Applications Recent authors, with one exception that I know of, either ignore or reject the line of reasoning we have been examining thus far, and so pass over this prototype of the cosmological argument or reject it as invalid in a modern thought context. The exception is Michael Buckley, who in his recent work, Motion and Motion’s God,34 correctly identifies the argument as the culmination of Aristotle’s Physics and thus central to any cosmological argument worked out in an Aristotelian context. It is not the Aristotelian, however, but the modern thought context that offers difficulty, so let us now proceed to the contemporary application of the historical material we have just reviewed. Why do we have difficulty in understanding the type of justification for the motor causality principle offered by Aristotle in Book Seven of the Physics? Is it merely because we are somewhat rusty on 32. Aristotelis physicarum acroasum . . . , fol. 184vb–85rb. 33. Aristotelis physicarum acroasum . . . , fol. l 85rb–vb. 34. Michael Buckley, Motion and Motion’s God (Princeton: Princeton University Press, 1971); originally a dissertation written under the direction of Richard McKeon.

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the materials covered in Books Five and Six of that same work? That may be part of the difficulty, but I suspect that its deeper root lies in the cosmology in which it is imbedded. And whether or not we have been able to supply an alternate cosmology that is more viable in the present day, we are prone to regard the problem as already solved in such a way as no longer to require a motor causality principle. We are disposed to do this, I maintain, because we absorb motor causality into technical terms such as force, mass, and energy, and thus effectively terminate the argument before it can be started or so insulate it from philosophical inquiry as to nullify its value as a starting point in any search for transcendence. Let me illustrate this by taking object AB, a divisible body, and instantiating it in three different ways: (1) as a block of wood; (2) as a mechanical mouse; and (3) as a live mouse. In each case I am interested in the local motion of body AB, a translational motion from here to there. The first case, though the simplest to visualize, turns out to be conceptually the most difficult, for I wish to explain the motor causality involved when the block of wood moves, and again in three different ways: (a) when I push it; (b) when I throw it; and (c) when I allow it to fall to the ground. The instances of the mouse, whether mechanical or live, are less difficult, because the mouse rather obviously moves itself, whereas the block of wood’s claim to being a self-mover is not at all obvious. Let us start, therefore, with the mouse, and inquire into how its motion can enlighten us on the principle, “Everything that is in motion is moved by something.” The live mouse may be regarded as made up of parts D, E, and F: F denominates the part or parts that seem to move as a whole, and E the quantitative parts that do the moving when the whole moves. I do not intend to enter into the physiology of mice, and will be content to identify E as the brain, the heart, the muscles, and the legs, to all of which we ascribe the mouse’s motor activity. Aside from these parts, however, followers of Aristotle will insist on yet another mover, identified by Nifo as a qualitative part, and in the case of the live mouse

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called the mouse’s soul. To the extent that the soul is not a quantitative part, and to the extent that it is separable from the mouse’s body, and upon separation results in a dead, or inert, or unmoved mouse, one can say in this instance that the soul is other than the mouse’s body, and therefore that the body’s movement illustrates the principle, “Whatever is in motion is moved by another thing.” For those who have difficulty with the soul concept, let us consider now the mechanical mouse, and for the sake of simplicity, let us conceive it as merely a block of wood, AB, moved by a wheel, which is itself made to rotate by a coiled spring or a stretched rubber band. Wind up this mechanical mouse, place it on a smooth surface, and it too seems to move itself. The case is not dissimilar to that of the live mouse, so let me label the moved part, the block of wood, F, and the moving part, the wheel, E. Perhaps I should include with the wheel the spring and the rubber band, for a further condition is needed for the wheel to move the block of wood. The spring must be coiled, or the rubber band must be stretched, and although coiling and stretching may introduce a quantitative change in the object coiled or stretched, the resulting modification is more qualitative than it is quantitative. It is difficult to name this qualitative part, which I shall denominate D, but common parlance will probably countenance the terms force and energy. We say D moves E and E moves F in the sense that the force moves the wheel and the wheel moves the mouse, or we say that the mechanical mouse moves as long as there is energy in the spring or in the rubber band, and this energy moves the wheel, which in turn moves the mouse. Note how, in this explanation, the concepts of force and energy play the same role as the concept of soul, and if one were to inquire whether the case of the mechanical mouse instantiates the motor causality principle, he would have to reply that, to the extent that the force and the energy are different from the body AB, to that extent “Whatever is in motion is moved by another thing.” These cases have illustrative value, but it seems to me that neither is precisely what Aristotle has in mind when he speaks of a body AB

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moving primarily and essentially, for both can be traced down to motion “through a part,” and per partem is usually opposed to per se. The simple block of wood, however, unadorned with wheel and spring, can move primo and per se, and so let us now turn our attention to the simple block. Let us first imagine the block on a plane surface, and examine the case where it moves because I push it. In such a case there is no doubt that whatever is moved is moved by another, and I am that other. Note here, however, that even I can be replaced by the force concept, for we can conceive my push on the body as a mechanical force, and then we say the block of wood is moved by a force. Whether it is accelerated in its motion or uniform will, of course, requires a different understanding of the force concept, but let us merely note this in passing and possibly return to it later. Second case: instead of my merely pushing the block of wood along a surface, let me now throw it through the air. Consider the thrown block in simple translational motion, and then the whole block and each of its parts move with the same velocity. Now, does this case instantiate the motor causality principle? I threw the block— let there be no doubt about that—and thus it would seem that I am the mover. In a general way that suffices for an answer, but it does not seem to explain how I actually move the block after it has left my hand, and so various “other movers” are excogitated.35 For example, I impressed a force, or an impetus, or a momentum on the block of wood, and these serve to explain its motion. Notice that, as in the case of the mechanical mouse, these explainers are essentially qualitative, although they are associated in some way with the quantitative parts of the wood. In the example, E and F, as quantitative parts, are differently conceived than D, the qualitative part, which we call force, energy, or more properly momentum (mathematically equivalent to mass times velocity). Some of you may feel comfortable thinking of 35. Niphus, Aristotelis physicarum acroasum . . . , fol. l 84vb.

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me as the mover of the thrown block, but I suspect that more of you would prefer to say that it is being moved by a force, or by a momentum (something associated with its mass), and this is the only sense in which it can be said actually to be moved by some other thing. Finally, let us consider the case where I do not throw the block of wood but simply drop it. The block of wood moves, and clearly I do not move it in any essential way, and so again it seems to move itself. But is this actually the case? Many educated people will answer “No,” it is being moved by the force of gravity, or by potential energy. And if they think in terms of the motor causality principle, their explanation of its movement will not be appreciably different from the way in which they explain that of the mechanical mouse or the thrown object. On such a supposition, let us examine at this point the mechanism they may employ in the explanation. To do this it will be convenient now to return to a problem discussed by Avicenna, Averroës, and Nifo in their commentaries on Aristotle’s argument, but which I passed over in my historical exposition.36 When a heavy object falls, are all parts of the object completely homogeneous with the whole, or are there some parts that are “first moveds,” in virtue of whose moving the other parts are made to move? Averroës and Nifo identify such “first moveds” as the minimal parts of the object, usually referred to as minima naturalia, and their question makes sense in the Aristotelian context of whether the whole is moved by parts, on whose motion or rest the motion of the whole depends. To locate their query in a modern thought context, let us ask whether the block of wood falls because all of its parts are attracted to the earth or because only certain parts, or parts of those parts, are so attracted? Is it only the massive nuclei of the constituent atoms and molecules that explain the fall of the block of wood, or does the block fall as a whole, and in equal virtue of each and every one of its parts? We cannot explore the answers to these questions 36. Aristotelis physicarum acroasum . . . , fol. 185v.

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now, but let me simply note that one who prefers an answer in terms of atomic and molecular nuclei has equivalently opted for a DEF type of explanation, where F are the remaining quantitative parts, E are the nuclei as moving quantitative parts, and D is what Nifo would call a qualitative part, now variously understood as force, mass, or energy. So even in this case we have justified Aristotle’s motor causality principle, and it still remains true that “Whatever is in motion is moved by something else.”

Efficient vs. Material Causality It is not my intention, however, to dwell on this justification but rather to draw attention to the extreme difficulty of tracing lines of efficient causality in directions indicated by terms such as force and energy, and the value, on the other hand, of concentrating on material causality in the early stages of the cosmological proof. Did we have space, it would be most interesting to trace in detail the way in which force concepts have baffled the greatest of classical philosophers in their attempts to account for efficient causality. I refer the reader to my forthcoming book, Causality and Scientific Explanation, for a full treatment of this fascinating topic.37 Suffice it to mention here only the following highlights Isaac Newton, the founder of classical mechanics, probably went deeper than any other man into an understanding of the concept of force, and particularly the so-called “force of gravity,” and yet he ran into an impasse in every search for its efficient cause. His own personal view was that this had to be immaterial, that such an immaterial principle was necessary not only to explain gravitating motion but even the uniform motion of bodies, and that, ultimately, it must be identified with God. David Hume was more explicitly agnostic when dealing with causality, but his own positive exposition is so laden 37. In two volumes: vol. 1, Medieval and Early Classical Science (Ann Arbor: University of Michigan Press, 1972); vol. 2, Classical and Contemporary Science, to appear in 1973.

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with inconsistencies as to have only suggestive value for other philosophers such as Berkeley and Kant. George Berkeley was quite willing to admit, with Hume, that the Newtonian scientist could not detect causes. His was the frontal attack on the force concept, for in his view it had the same ontological status as the epicycles of the medievals. Berkeley has been hailed on this account as the first instrumentalist among philosophers of science, but his own metaphysical views were not unlike that of Newton. If the physicist could not discover causes, the metaphysician could, and these were nothing more than God’s immediate operation in the physical universe. Leibniz changed the emphasis somewhat as he entered into the long debate with Newton via Samuel Clarke, but he too traced motion back to God, although his understanding of force was far different from that of Berkeley. And finally, Immanuel Kant, so convinced of the truth of Newtonian science that he would use it as a tribunal to condemn classical metaphysics as a transcendental illusion, jeopardizes his entire Critique of Pure Reason as he vainly sought to build his Metaphysical Foundations of Natural Science on the very concept of force. My point is simply this: the cosmological argument needs reappraisal in the present day. The problems of local motion are not insoluble, but they require attack not only in terms of the principles of final and efficient causality but according to the demands of formal and material causality as well.38 The proof of motor causality through 38. One can interpret Einstein’s theory of general relativity along lines favorable to this thesis; see A. S. Eddington, Space, Time and Gravitation (Cambridge: Cambridge University Press, 1920), 95–96; and Max Jammer, Concepts of Space (Cambridge, Mass.: Harvard University Press, 1954), 20. For a general exposition of the role of matter in Aristotle’s theory of demonstration, see the latter part of Robert Sokolowski, “Scientific and Hermeneutic Questions in Aristotle,” Philosophy and Rhetoric 4 (1971): 242–61. My own emphasis on material causality is obviously not meant to exclude the traditional arguments through efficient causality, and in fact points the way to such arguments. Thus my procedure is very much like that of William Harvey, who first demonstrated the circulation of the blood using a material cause, i.e., the quantity of the blood (or matter) involved, and then sought the efficient cause of the circulation in the pumping action of the heart.

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the material cause, as explained by Aquinas in his commentary on the seventh book of the Physics, leaves full room for an understanding of the sheer inertness and passivity of the material object as such. Discourse about such an object in terms of force, and mass, and energy brings efficiency and activity into the corporeal substrate and already begins to intimate that elements of the divine may be found in matter. This is not to deny such elements; in fact, it is their very presence in matter that makes the cosmological argument so interesting to begin with. This is not to deny also that a full analysis of motion in terms of act and potency, and a careful metaphysical assessment of all facets of the infinite regress problem, are essential for the completion of the cosmological argument. But the starting point of the argument, more than anything else, requires reappraisal in the present day, and to this task the proof from the divisibility of the movable object can still make a distinctive and noteworthy contribution.

Chapter Eleven Review of Anthony Kenny’s The Five Ways

Chapter Eleven

Review of Anthony Kenny’s The  Five  Ways

With the renewal of interest in natural theology prompted by the publication of Flew and McIntyre’s New Essays in Philosophical Theology (1955), attention has been directed once again to rational arguments for God’s existence. The ontological argument was the first to benefit from this resurgence of interest, but in the two books under review cosmological argumentation and its various formulations come in for their share of attention. Kenny’s work, which shows more the negative influence of Flew, stresses the difficulty involved in separating Aquinas’s five ways from the medieval cosmology in which he sees them as imbedded. Reichenbach’s work is more positive in spirit, the author’s major concern being to reformulate St. Thomas’s first three ways so as to meet the objections of Hume and Kant and contemporary critics in the analytical tradition. Both works merit a brief exposition and critique, if only because they consider much the same subject matter and yet come to contrary conclusions. After a brief introduction wherein he allows that “the criticisms of Kant are certainly still the most effective obstacle any rational theism has to meet” (3), Kenny devotes a chapter each to the five proofs for God’s existence offered by Aquinas in Summa Theologiae I, q. 2 a. 3. In the case of each via he attempts a rather complete exegesis of the text, supplementing this with St. Thomas’s arguments in parallel 213

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places and with elucidations supplied by commentators, mainly recent, including Roberto Masi, Joseph Owens, and Peter Geach. In each instance Kenny raises objections drawn from modern science and from Humean, Kantian, and more recent philosophies to show not only that the ipsa verba of St. Thomas are unacceptable to the modern mind but also that “scholastic modernizations” must share the same fate (cf. 4). With regards to the prima via, Kenny experiences special difficulty with the principle “omne quod movetur ab alio movetur” and so sides with Suárez’s evaluation of the proof that it is impotent “to prove that there is anything immaterial in reality, let alone that there is a first and uncreated substance” (33). The chapter has some interesting material on the chains of movers involved in inertial and gravitational motion, particularly when the author attempts to explain these in terms of Newtonian and Einsteinian mechanics, but unfortunately his discussion here comes to no conclusive results. Kenny’s examination of the secunda via focuses on the principle of efficient causation, which he formulates in mathematical logic following Salamucha and others. His difficulty here is with essentially subordinated series of causes, which he sees as intelligible in terms of medieval astrology, as thus based on an “archaic fiction” (44), and hence unacceptable in the light of modern science. The discussion of the tertia via, admittedly one of the most difficult proofs to make sense of, permits Kenny to range through contemporary discussions of possibility, necessity, and contingency. His evaluation is that the proof concludes as well to the “everlasting existence of matter with a natural indestructibility” (69) as it does to God’s eternal existence. In analyzing the quarta via the author dwells at some length on Platonic Forms, predicates, and existence, using Geach as a foil for much of the discussion; his own conclusion, predictably, is that “the notion of Ipsum Esse Subsistens, . . . so far from being a profound metaphysical analysis of the divine nature, turns out to be the Platonic Idea of a predicate which is at best uninformative and at worst unintelligible” (95). His critique of the quinta

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via, finally, allows Kenny to discourse on contemporary problems relating to teleological explanation and the philosophy of mind, again coming to the negative result that the argument from design has no more claim to validity than the other theistic arguments. Kenny’s book is clear and well written, and for advanced students is an excellent problem text against which to measure their understanding of Aquinas’s arguments and their ability to cope with the agnosticism and skepticism that characterize so much of contemporary philosophy. This reviewer agrees with Kenny that substantial work is required to recast the traditional five ways in a terminology and conceptual setting that will make sense to the modern mind. To do this, however, requires a complete review and reconstruction of the concept of causality and how this relates to scientific explanation, and until this is forthcoming it would be fruitless to attempt a step-by-step refutation of the objectionable points in Kenny’s treatment.1 In the interim, however, a counterbalancing assessment of the cosmological argument has become available, and this too deserves our attention. Bruce R. Reichenbach’s The Cosmological Argument takes off from the same point of departure as Kenny’s book, that is, Flew and McIntyre’s New Essays, and covers much the same ground as does Kenny, though in somewhat more elementary fashion and coming, as already noted, to quite opposite results. Reichenbach restricts himself to Aquinas’s first three ways and seeks a general form of cosmological argumentation that will serve to structure each of these. He hits upon 1. A noticeable defect of Kenny’s book is the lack of detailed historical scholarship, particularly of Aristotelian and Thomistic commentators in the centuries before our own. For example, Kenny dismisses rather summarily Aristotle’s and St. Thomas’s cosmological proof of the “omne quod movetur” principle (19), while manifesting little or no acquaintance with substantial commentators such as Simplicius, Averroës, and Nifo, who have explained the proof in intelligible and convincing fashion. For details, see the reviewer’s “The Cosmological Argument: A Reappraisal,” to appear in the Proceedings of the American Catholic Philosophical Association for 1972. For further background, see also the reviewer’s Causality and Scientific Explanation, soon forthcoming in two volumes from the University of Michigan Press.

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the notion of contingency as the most plausible and arguable instance of St. Thomas’s type of proof, and formulates his argument as follows: A contingent being exists; this contingent being depends on something else for its existence; this something else, as a cause, is either another contingent being or is non-contingent (necessary); if contingent, it in turn cannot be caused by an infinite series of contingent beings; therefore, a necessary being exists.

The explanation and articulation of the various components of this general argument occupies the whole of Chapter 1. Chapters 2 and 3 are concerned respectively with causation and with the principles of causation and of sufficient reason. Reichenbach’s main target throughout these chapters is Hume’s analysis of causation as constant conjunction and his critique of the causal principle; he argues also against Braithwaite’s covering-law analysis of causation and against Camus’s objection that the universe is absurd and thus it is vain to employ any principle of intelligibility such as that of sufficient reason. In Chapter 4 Reichenbach establishes that there is no repugnance in a proposition’s being informative and necessary at the same time, distinguishing between logical and real necessity, and showing how the Kantian account of necessity can indeed lead to a regulative principle for unifying man’s experience but not to knowledge of a real cause operative in the universe. Chapter 5 is addressed to Bertrand Russell’s objection that the notion of causality cannot be applied to contingent beings considered as a totality, and it shows how this may be a valid criticism of the Scotistic way of conceiving causal series (used by Copleston in his famous debate with Russell), but that it has no force against the Thomistic way of so conceiving them. Chapter 6 takes up the problem of necessity in the conclusion of the proof and argues that this is not merely a logical necessity, as J. J. C. Smart and Paul Edwards have maintained, but is better characterized as a conditional necessity leading to knowledge of a being that is necessarily existent. In Chapter 7 Reichenbach returns to Kant to disprove the latter’s thesis that the cosmological argument is

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dependent on the ontological argument. Then, in the eighth and final chapter, the author takes up the question of the identification of God with the necessary being that terminates the cosmological argument and explains why this being cannot be matter or a material universe necessarily existing. While maintaining that the identification with the divine is actually extrinsic to the argument itself, Reichenbach urges the plausibility of such an identification. He concludes with some reflections suggested by this on the relationships between faith and reason, arguing, contrary to Kierkegaard, that a faith grounded in reason is superior to a commitment that is based on the improbable, the absurd, and the irrational. Reichenbach’s book is not as scholarly as Kenny’s and at times the author’s use of rhetoric impedes rather than advances his argument. Also, he takes no notice whatever of Kenny’s work, which seemingly is unknown to him; this is unfortunate, since his own exposition would have benefitted by attempting to meet Kenny’s objections, which are more pointed than those he actually considers. Again, Thomists will not be too happy with Reichenbach’s attempt to reduce the prima and secunda viae to the tertia via, or with his implicit contention that the third way underlies and is more fundamental than the first two. These criticisms notwithstanding, however, Reichenbach’s work is still an intelligent and worthwhile exposition of a difficult subject matter, and one that is more suited for beginning philosophy students than is Kenny’s. The fact that these two books come to such disparate results, of course, is an indication that much serious work yet remains to be done on the cosmological argument.

Chapter Twelve The First Way: A Rejoinder

Chapter Twelve

The First Way A Rejoinder

In the preceding article, Professor John King-Farlow has raised a number of intriguing questions relating to the prima via of St. Thomas Aquinas—questions, indeed, that cannot be answered with any measure of completeness in a brief reply. The queries he raises, however, do present the opportunity to offer some further observations on the traditional understanding of the proof and on its validity in the light of modern science, and these will be the focus of this rejoinder. The prima via, it would seem, is a clear instance of a cosmological argument for the existence of God. It starts from an observable aspect of the cosmos, i.e., the motion or movement or change that is sensibly observable in it, reasons a posteriori from this to an ultimate cause, and so concludes to the existence of a first unmoved Mover who is incorporeal, immaterial, infinite in power, etc., and who in the sequel can be identified with the God of Revelation. Although in its later stages the proof makes use of metaphysical reasoning, its beginnings actually pertain to natural philosophy. (Indeed, as most Thomists hold, if the natural philosopher could not prove the existence of some type of being that really exists and is neither material nor in motion, there would be no need for metaphysics as a discipline, since its subject

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matter would be essentially the same as that of natural philosophy.) The natural philosopher, moreover, abstracts from certain features of the physical world in elaborating his discipline; this abstractive process is found in all sciences, although some abstract in ways different from others, and their manner of abstracting can unfortunately have a restrictive influence on the types of arguments and proofs they are able to elaborate.1 On this understanding, the prima via is only one of several possible cosmological arguments, all of which, precisely as cosmological, operate at the same “degree” of abstraction. Thus the secunda via, the tertia via, and the quinta via may be viewed as different proofs,2 complementary in some respects, following the same basic logic or methodology, each of equal abstractness, and yet each capable of independent formulation and justification.3 Moreover, insofar as these proofs focus attention successively on particular aspects of the cosmos, it is admittedly quite legitimate to say that each one “abstracts from” other aspects of the same cosmos. Such a use of the notion of “abstraction,” however, is different from the way in which the abstractive process may be said to differentiate the sciences. King-Farlow calls attention to my frequent use of the terms “abstract” and “abstraction” and makes a play on these expressions in urging his own interpretation of the prima via—one essentially at variance with that given it in the Thomistic tradition. The difference between his use of “abstraction” and mine is that he gives the term the rather broad, precisive meaning just illustrated, whereas I use it in the technical 1. For a succinct account of Thomistic teaching on abstraction and its relation to the classification of the sciences, see the articles by E. D. Simmons entitled “Abstraction” and “Sciences, Classification of” in the New Catholic Encyclopedia, 16 vols. (New York: McGraw-Hill and Publishers Guild, Inc., 1967, 1974), 1:56–59, and 12:1220–1224. 2. Here the quarta via is consciously omitted as being more metaphysical in character than the other four ways. 3. My affirmation of the partly complementary character of the proofs is shared by King-Farlow in his books Reason and Religion and Faith and the Life of Reason. He would stress, however, that the proofs are only collectively valid, whereas I am further claiming their individual validity. See notes 4 and 13, infra.

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Aristotelian-Thomistic way employed to differentiate the various sciences.4 To be more specific, the overriding concern in my articles cited by King-Farlow has been with mathematical reasoning and the mathematical physics this generates, which Thomists commonly think of as operating (at least partially) at the “second degree” of abstraction, i.e., an abstraction that leaves aside sensible matter and motion and concentrates exclusively on the quantifiable aspects of natural phenomena, which aspects are refractory to analysis in terms of efficient and final causality. The natural philosopher, as opposed to this, operates at the “first degree” of abstraction, i.e., one that leaves aside only the individual aspects of natural phenomena so as to consider them universally, but still as involving sensible matter and motion in their definition, and for this reason open to the discovery of agents and ends. All cosmological arguments, to the extent that they are cosmological and in this sense pertain in some way to natural philosophy, may be seen as functioning (at least in their initial stages) at this first degree of abstraction. It is preferable, on this account, not to speak of the ways in which the various cosmological proofs differ among themselves as differences of “abstraction” or of “abstractness.” Here the Thomistic tradition appears to be at odds with King­Farlow, who in the foregoing article speaks first of the prima via “in physical space” and then of the same proof “in moral space.” Seemingly, he regards the latter consideration as less “abstract” than the former and as more appealing, on that account, to the Christian theist because of its open4. Correspondence with King-Farlow shows that we agree to disagree on this matter of “abstractness” thus. A description D1 is a more abstract description of the world W than is description D2, when D1 covers fewer sets of predicates required for indicating the most important features of W. It is Aquinas’s claim and mine that the existence of a physical universe to which predicates of the natural sciences, N1 , N2 , . . . Nn , are truly applied offers sufficient reason to affirm the existence of a Being to whom related predicates can be assigned and who is identifiable with the God of Revelation. It is King-Farlow’s view that some ethical predicates, E1 , etc., as well as N1 , etc., must he applicable if sufficient reason is to be given. This accents, in a different way, our basic difference over the merely collective validity as opposed to the individual and collective validity of the proofs.

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ness to moral and personal values. In the traditional view, neither of these considerations is more “abstract” than the other; what is important is that they are precisive of different aspects of the world of nature and thus may provide the basis for different cosmological proofs. So, when King-Farlow speaks of “the prima via in physical space,” most of what he says is unexceptional, for he is talking about the prima via as Thomists have generally understood it; when he speaks of the same proof “in moral space,” on the other hand, it is somewhat difficult to follow his argument. In this second manner of speaking he may well be on the track of a valid proof for God’s existence, but if so, one would not wish to call this new proof the prima via. Perhaps what he is proposing there is a nuanced version of the quinta via, or alternatively, he may be working out a sexta via, or a septima via, etc. In my published writings, as opposed to this, I have dealt exclusively with the prima via in its traditional understanding and resist being drawn into a related area of discourse, however enlightening this might be to the Christian theist, particularly when much yet remains to be done in the domain of “physical space”—as King-Farlow himself has effectively shown. To concentrate, then, on the first part of the foregoing article, the question of the finitude of physical space or of physical movers and things moved is certainly integral to both Aristotle’s and Aquinas’s arguments for the existence of a first unmoved Mover. The difference between the arguments lies in the fact, as is well known, that Aristotle was convinced of the infinite duration of the universe whereas Aquinas believed in its creation in time and thus in its temporal finitude; for purposes of argument, however, Aquinas was willing to admit the theoretical possibility of an infinite temporal regress, and so his argument does not develop in a way essentially different from Aristotle’s.5 Both thinkers, moreover, thought of the hierarchy of movers and moveds in the context of what is now referred to as a Ptolemaic 5. A fuller exposition of Aquinas’s view on the temporal finitude of the universe is given in my article, “Aquinas on Creation: Science, Theology, and Matters of Fact,” The Thomist 38 (1974): 485–523.

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universe, i.e., a closed world of finite dimensions and composed of a finite number of concentric spheres. In such a universe no physical body can be actually infinite, although, as King-Farlow rightly discerns, physical bodies can be thought of as made up of a potentially infinite number of parts when they are either divided into, or addition is made to them by means of, proportional parts—the type of geometrical progression favored by Peripatetics and illustrated so well in King-Farlow’s article.6 For the cosmologist of the present day, of course, the context is quite different and so the problematic must also be stated differently. It is precisely his awareness of this situation that has led Anthony Kenny to reject the Five Ways as hopelessly imbedded in a medieval cosmology.7 One need not agree with Kenny’s pessimistic evaluation,8 however, and in fact one can be quite sympathetic to King-Farlow’s analysis above, for the concept of potential infinity may well prove adequate to handle objections arising from modern mathematical theories of the universe. This adequacy cannot be assumed, however, and requires more detailed argument and substantiation than could possibly be given in this rejoinder. Apart from the problem of the finitude of the physical universe, there are other special difficulties associated with the prima via that arise in the context of modern physics and that perforce could not have been considered by either Aquinas or Aristotle. The thorniest problem would seem to be that posed by inertial motion and the way in which this threatens the general applicability of the AristotelianThomistic thesis on the simultaneity of cause and effect (or of mover and thing moved) to the elimination of the infinite regress possi6. Some aspects of King-Farlow’s exposition, it may be noted, are adumbrated in late medieval and scholastic discussions of infinity. See especially Domingo de Soto, Super octo libros physicorum Aristotelis questiones, 2nd ed. (Salamanca: Andrea a Portonariis, 1555), fols. 52r–58r. 7. Anthony Kenny, The Five Ways: St. Thomas Aquinas’ Proofs of God’s Existence (London: Routledge & Kegan Paul, 1969), 3. 8. See my review of this in The Thomist 36 (1972): 721–24, as well as the article cited by King-Farlow, “The Cosmological Argument: A Reappraisal,” Proceedings of the American Catholic Philosophical Association 46 (1972): 43–57.

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bility. Some aspects of this problem have been examined in the article on Newtonian antinomies cited by King-Farlow, but one of my more recent publications also takes note of a number of texts where Aquinas admits the possibility of antecedent (i.e., non-simultaneous) causality in physical processes.9 To my knowledge Aquinas nowhere resolves the enigmas that such an admission creates for the prima via, although a resolution appears generally possible and needs only to be worked out in detail for types of causal regress that interest the modern physicist. In fairness to Kenny, moreover, it should be admitted that contemporary Thomists have not adequately answered the questions he raises relating to the motor-causality principle and the infinite regress as applicable to cases that have arisen in recent science. This failure would seem to be traceable in no small part to the proclivity of Thomistic metaphysicians to answer every objection to theistic proofs in terms of being and the act of existing, and to their failure, as a consequence, to take a close look at the world of nature. If they pretend to offer cosmological arguments at all, unfortunately they do so in terms of what the late R. J. Nogar referred to as a “cosmology without a cosmos,”10 one that is clearly at variance with both the spirit and the letter of Aquinas himself. On this account, it is refreshing to see King-Farlow addressing himself to these concrete cosmological problems—for it is only by solving them that one can promote acceptance of the prima via by the modern mind.11 With regard to the apparently abrupt dismissal of the second part of King-Farlow’s article, the following clarification may now be in order. The introduction of a moral dimension into discussions of 9. W. A. Wallace, “Aquinas and the Temporal Relation Between Cause and Effect,” Review of Metaphysics, 27 (1974): 569–84. 10. See his essay of that title in From an Abundant Spring, The Walter Farrell Memorial Volume of The Thomist (New York: P. J. Kenedy, 1952), 363–91. 11. I also endorse King-Farlow’s view that, if modern commentators like Copleston and Kenny present Aquinas over-sympathetically in failing to stress Aristotle’s pertinent view on the finitude of space, then they offend fewer modern physicists, but they seriously misrepresent St. Thomas’s own reasoning. Now is a good time for us both to stress this.

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the prima via is particularly distasteful to me because it inadvertently concedes too much to the two philosophers who have made the prima via unappealing to our contemporaries, namely, David Hume and Immanuel Kant. As argued in my second volume on Causality and Scientific Explanation,12 neither Hume nor Kant was consistent in his understanding of causality, and each effectively adopted a subjectivist approach to knowledge reached through causal analysis. For Hume causality became nothing more than a psychological projection into reality, a matter of “feeling” or of human anticipation, whereas for Kant it became an a priori category of the understanding that would serve to organize phenomena but could yield no knowledge of any reality behind the appearances. For both, therefore, a posteriori demonstration became an impossibility, as did any science of nature in the epistemic (as opposed to the empiriological) sense, and cosmological proofs for God’s existence could lead at best to transcendental illusion. Thus, for them, the way to God through the intellect and its understanding of the universe was effectively blocked, and if one wished to assent to God’s existence he would have to do so on moral or affective grounds. (This is not to deny, of course, the validity of theistic proofs based on such ethical and valuational grounds, but it does oppose reducing all proofs to this kind, and particularly the prima via.)13 12. W. A. Wallace, Causality and Scientific Explanation, vol. 2, Classical and Contemporary Science (Ann Arbor: The University of Michigan Press, 1974), 38–51, 60–75. 13. The fundamental difference between myself and King-Farlow on this point has been well put by him in our correspondence, as follows: “You take the Five Ways to be complementary and individually adequate; I take them to be complementary and collectively imposing. You think of deductively sound demonstrations; I think in terms of ‘Good Reasons’ arguments which wise people can come to find overwhelming. Hume and Kant may have sometimes thought that reasoning with normative premises is the soft underbelly of philosophical theology as they understood it. But the enthymematic premise that some arguments are good and some are bad, some wise, some foolish, etc., then becomes the soft underbelly of all intelligent reasoning, including Hume’s and Kant’s. As I argue in Faith and the Life of Reason, the ‘positivist’ attack on the ethical dimension of what we seem to experience generalizes itself into an attack on all normative dimensions. But this could only be sound if it is unsound—that is, if we know some reasoning to be good, bad, worthy of attention, dishonest, etc.”

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As noted in the recently published supplement to the New Catholic Encyclopedia,14 both Hume and Kant tried to elaborate philosophies of science, but they did so only in a context provided by classical mechanics, and their efforts have proved singularly sterile for evaluating realist claims arising from high-energy physics. The discovery of vast numbers of so-called “elementary particles,” with non-classical properties that render them unobservable even in principle, suggests that scientists are now (contra Hume and Kant) de facto employing causal reasoning to transcend sense experience and to arrive at deeper ontological explanations of the physical universe. Such scientists, rather than recent philosophers of empiricist and analytical bent, are the thinkers who are developing canons of demonstrative inference that can be used to establish the existence and attributes of entities unlike those falling under sense observation. In this they have much in common with Aquinas and with the type of reasoning he employed to elaborate the quinque viae. The obvious task awaiting those of us who are interested in defending cosmological proofs for God’s existence is to refine and complement their methodology and show how it can sustain a plausible inference to such a transcendent cause. And, as has been suggested in the same supplement,15 such an enterprise must be directed, not to the “religious” person who regards his commitment to God as an affair of his heart or will and not of his intellect but rather to the hard-headed thinker who uses his mind to study the world of nature in objective fashion and so to penetrate to its underlying causes. This is not to say, of course, that King-Farlow would be unsympathetic to such a program. But he will probably agree that it would have to avoid pursuing some of the leads he suggests in the second part of his article so as to devote full time to clearing up the difficulties he raises in the first. 14. In my article entitled “Cosmological Argument,” New Catholic Encyclopedia, 16:105–8. 15. “Cosmological Argument,” New Catholic Encyclopedia, 16:107–8.

Chapter Thirteen Immateriality and Surrogates in Science

Chapter Thirteen

Immateriality and Its Surrogates  in Modern Science

The word “matter,” it has been remarked, has passed out of the language of science, while more technical terms such as “mass” have largely taken its place.1 This being so, one should not be surprised if other words with long histories and profound philosophical significance, such as “substance,” “nature,” and “cause,” have had similar fates in the scientific vocabulary. Nor should one be surprised if the concept of immateriality should appear foreign to the concerns of scientist and philosopher of science alike. Admittedly, the word “immateriality” is of rare occurrence in scientific discourse, but this is no clear indication that the concept itself has been eliminated, or that its meaning is not reflected in other terms that enjoy greater currency. The subtle difference, in fact, between the meaning of immateriality and its verbal expression, long recognized by philosophers in our tradition, is the focal point of this paper. The title refers to these alternate expressions that capture the notion of immateriality in whole or in part as its surrogates. Here we adapt the Latin subrogare, “to seek in place of,” to our particular purpose. For whatever reason, but most 1. For a lengthy discussion of this terminological usage, see Ernan McMullin’s introduction to The Concept of Matter, ed. E. McMullin (Notre Dame: Notre Dame University Press, 1963), 1–41.

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probably because of the empiricist bent of their discipline, scientists have sought to replace, or find a substitute for, the immaterial whenever this intrudes itself into their consideration. The surrogates obviously do not dispense with the concept; they merely attest to its pervasive character and to its radical uneliminability from scientific discourse.

Surrogate Concepts In his Philosophy of Natural Science, a distinguished philosopher of science, Carl Hempel, gives witness to the type of subrogation I have in mind. When discussing theoretical explanation, Hempel speaks of entities and processes that lie beneath or behind the phenomena; he is willing to admit these into scientific discourse, he says, if they have specific implications concerning the phenomena they are offered to explain. This requirement does not entail, in his view, the automatic rejection of what he refers to as “non-material agencies,” provided these have some empirical import.2 The examples he gives of such non-material agencies are revealing: vital forces, as these are used to explain teleological processes in nature; and gravitational forces, as these are used to explain the regularity of planetary motions in Newton’s theory of the solar system. Here the concept of force, in Hempel’s mind, is non-material. Its status is somewhat ambiguous, for he sees gravitational force as having empirical import but vital force as not. Should we restrict ourselves to the physical sciences, however, we need no great jump of the imagination to include the concepts of field, energy, and even mass-energy under his general rubric of nonmaterial entities. Immateriality, in this sense, is opposed to the material in things, to the matter within them, as this is conceived in a commonsense way. 2. Carl Hempel, Philosophy of Natural Science (Englewood Cliffs, N.J.: Prentice Hall, Inc., 1966), 72.

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To use Michael Faraday’s apt expression, “matter cannot act where it is not,”3 and since a body’s gravitational force appears to do just that, it is patently non­material. A fuller delineation of the characteristics of matter that are negated when one ordinarily speaks of the nonmaterial would, of course, have to include more than this. I propose the following notes. Matter somehow refers to the stuff of which a thing is made, to its parts or components, without regard to the particular structure or arrangement that might be imposed upon them. Structure or arrangement is more frequently regarded as the correlative of matter, namely, form. Structure is seen as apt to be shared in a large number of things with the same form, whereas the matter of the thing is thought to be peculiarly its own. This suggests another characteristic of matter, namely, that it is a type of individuating principle: it separates one thing off from another, makes it different in number if not in kind, and serves to localize it in space and in time. Yet another characteristic of the stuff we call matter is its tendency to persist throughout change. Whereas things that contain matter have a transient mode of existence, in the sense that they take on new appearances or actualities, the stuff within them persists and is thought of as a more or less permanent substratum that endures beneath the changing appearances. Finally, possibly because of the note of emergence or actualization that is associated with a new appearance, matter is usually thought of as potential and inert, as the passive component of things which makes them determinable in various ways but does not actively contribute to this determination.4 Each one of these characteristics of matter, we shall argue, is negated by one or another concept that plays a significant role in the thinking of modern scientists. The reasons for such negations become 3. In a letter of 1844 published in the Philosophical Magazine, cited by Mary Hesse, “Action at a Distance,” in McMullin, The Concept of Matter, 379. 4. This paragraph has been summarized from H. J. Johnson, “Changing Concepts of Matter from Antiquity to Newton,” Dictionary of the History of Ideas 3 (1973): 185–96.

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clear from a survey of science’s history, and we propose that they can all be associated with the more or less thoroughgoing mathematization of nature that was instituted as part of the Scientific Revolution of the seventeenth century. As a consequence, moreover, it would appear that immateriality continues to reassert itself in a new guise with each scientific advance. This may be regarded as a desirable outcome, but it is not an unmixed blessing, for many of the non-material concepts employed in the natural sciences seem to impede our understanding of vital and mental processes, to say nothing of evidences of God’s existence, that may be discernable from a study of the cosmos. It is to these problems that we would direct attention, after having surveyed a few concepts that serve as present-day surrogates for immateriality. To start with the concept of force already mentioned, this has a history almost as long as that of matter, which need not be traced here in any detail.5 The medievals used it to explain a wide range of phenomena, natural as well as violent, inorganic as well as organic, as is exemplified in terms they employed such as vis motrix and vis resistiva. Sixteenth-century scientists, possibly influenced by Latin translations of John Philoponus’s commentary on Aristotle’s Physics, saw nature as a force diffused through bodies that accounted for all of their characteristic motions. Galileo subscribed to this view, as did Kepler, who was the first to attempt to quantify vis and use it to explain the revolutions of the planets.6 By the time of Newton, forces had come to be pervasive in the universe and were seen to be characteristic of matter. The vis insita, the vis inertiae, the vis gravitates he could conceive mathematically to provide the basis for all the mechanical prop5. See my “Causes and Forces in Sixteenth-Century Physics,” Isis 69 (1978): 400–412. 6. For a history of the concept, see Max Jammer, Concepts of Force (Cambridge, Mass.: Harvard University Press, 1957); also my essay, “Some Sixteenth-Century Views of Nature and Its Causality,” to be published in the proceedings of the Tenth Annual Conference of the Center for Medieval and Early Renaissance Studies, SUNY Binghamton, which discusses Galileo’s views on this subject.

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erties of the universe. For Newton they were nature’s causes, its verae causae, even though he had to remain agnostic as to their more ultimate causes and seats. In virtue of them, matter was endowed with an order and an activity that reflected the intelligence and dominion of a Supreme Being.7 No longer passive and inert, no longer the sluggish earth of the Aristotelians, matter could find its way unerringly to a center of gravity according to the most complex of mathematical calculations. We need not push on to the modern developments, where force is regarded as a vector quantity or as a parameter that can be translated into space-time curvature with the aid of tensor mechanics, to see all that the Newtonian achievement implies. Henceforth matter was no longer delimited and localized: every particle in the universe influenced every other, and its very materiality was the means whereby it reached beyond itself to the farthest bounds of the universe. These considerations lead naturally to the next concept devised by modern science to explain the strange immateriality whereby matter comes to act where it is not. I refer to the concept of field, a concept invented precisely to rid science of embarrassing problems associated with action at a distance.8 Medievals were wary of attributing any causal activities to remote bodies, though they did countenance the possibility of influences or influentiae, which they viewed as occult forces, as vires occultae. The great success of the Newtonian concept of attractive force, however, and its refinement by Boscovich and Faraday reinforced the field concept and prepared for its acceptance by scientists as even more fundamental than matter.9 Still, the price of this acceptance was high: all forces were thought to be reducible to field activity, and yet the substrate that underlay such activity defied adequate description. What happened, in effect, was that the “mate7. See Alexandre Koyré, Newtonian Studies (Cambridge, Mass.: Harvard University Press, 1965); see also my Causality and Scientific Explanation, vol. l (Ann Arbor: University of Michigan Press, 1972), 205–10. 8. Thus Mary Hesse subtitles her Force and Fields (New York: Philosophical Library, 1962) “The Concept of Action at a Distance in the History of Physics.” 9. For details, see Hesse, “Action at a Distance,” 372–90.

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rial” came to be more and more “immaterial,” and practically all of the characteristics ascribed to matter earlier in this paper came to be negated, with the sole exception of its being a substrate bereft of all definable form and best thought of as a mathematical entity alone. Fields are regarded by modern physicists as carriers of energy, and thus they lead to another concept associated with immateriality, that of energy, and finally to a related concept, that of mass, with which we must conclude our survey. First used to study motion, then heat, and finally the activity of animal organisms, energy came in the eighteenth century to be recognized as a conservation principle that could serve to connect and synthesize all of nature’s operations.10 The Naturphilosophen and other nineteenth-century thinkers went on to conceive the roots of such connection to lie in spiritual and immaterial entities, and on this ground were prepared to rid the universe of matter entirely. Such a rejection of matter in favor of energy would not have been serious in itself had there not been a corresponding evolution in the concept of mass,11 enabling the latter to be linked with energy by Albert Einstein in a famous paper written at the beginning of the twentieth century.12 Energy had its start as a measure concept, as a way of reckoning the quantity of motion. Mass had a similar origin, though closer to our purposes, for it was to designate the quantity of matter conserved in various changes. As a consequence of Einstein’s statement of mass-energy equivalence in 1905, and the graphic demonstration of its applicability to the bodies of ordinary experience at Almagordo, Hiroshima, and Nagasaki forty years later, matter came to be yet more immaterialized. Energy itself had a somewhat evanescent 10. See Max Jammer, “Energy,” in New Catholic Encyclopedia, 15 vols. (New York: McGraw-Hill, 1967), 5:343–46. 11. The best treatment of this subject is Max Jammer, Concepts of Mass (Cambridge, Mass.: Harvard University Press, 1961), which he supplements with his article “Mass,” in New Catholic Encyclopedia, 9:412–13. 12. The original paper is reprinted in a collection entitled The Principle of Relativity by A. Einstein et al. (New York: Dover Publications, 1952), 67–71.

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and rootless character, and mass, initially conceived to designate the measure of matter in all its sluggishness, was soon found to be hyperactive and just as ephemeral as energy. The two, linked together, became the conservation principle that governs all interactions, from those between elementary particles to those occurring within exploding galaxies in the remote depths of space. The character of the substrate or matrix that provides the extramental basis for such activity, and from which new entities in their bewildering variety emerge and into which they again disappear, has endlessly perplexed atomic physicists. Throughout their probing into the microstructure of the real, as the late Norwood Russell Hanson has reported it, matter has been ultimately de-materialized. It is no longer observable or even picturable; it is bereft even of the normal kinematic and geometrical properties we assign to the bodies with which we daily come in contact.13 Thus, we have gone from immateriality to dematerialization. These remarks would not be complete, however, if they did not note current speculation about anti-matter, the polar opposite of the dematerialized stuff at which we have finally arrived, and which we have endowed with all kinds of characteristics. The matter that disappeared from the scientist’s vocabulary, as we said earlier, again reappears, but now with the prefix “anti-” to designate yet another way in which matter can be negated, and yet still employed, in the speculations of the modern physicist.

Philosophical Reflections A host of problems can here engage the Catholic philosopher, particularly one interested in the concept of immateriality. One might expect, of course, that philosophers of science would have dealt with these problems in great depth, and so would have much to contribute to-

13. Norwood Russell Hanson, “The Dematerialization of Matter,” in The Concept of Matter, 549–61.

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ward their solution. As it turns out, however, not much assistance can be expected from them, particularly by way of clarifying the ontological import of scientific concepts in which we might be interested. Like much recent philosophy, philosophy of science is heavily influenced by the analytical tradition. Its practitioners see themselves as filling a therapeutic function, dissolving traditional puzzles and paradoxes by showing how they arise from a misuse of language—in their case scientific, as opposed to ordinary language. As a consequence, few philosophers of science on the current scene would take on the task of specifying any ontological basis for concepts such as force, field, mass, and energy. Their preference would rather be to treat these after the fashion of theoretical terms that have no independent meaning but require interpretation through the entire conceptual system of which they form a part.14 When such concepts are left thus embedded in a logical superstructure, as it were, they can be safely used in an instrumentalist way without calling for any realist interpretation whatever. This saves the average philosopher of science from much embarrassment, for in all probability he has no philosophy of nature to provide a backdrop for philosophizing about science. Lacking the basic tools for a realist account of nature in all its complexity, he perforce cannot make connections between such an account and current scientific terminology. The only avenue for doing so that might lie open to him would be the route through history, but this again often proves to be terra incognita for those trained in this specialty.15 The magnitude of the problem this creates for the Catholic philosopher is accented when one considers how matter has hitherto functioned in Aristotelian Thomism to reveal the bases for its own transcendence. One could delineate at least three areas where im-

14. This is well explained by Ernan McMullin in his philosophical analysis of this concept in the New Catholic Encyclopedia, 5:346–49. 15. Historians of science have made substantial contributions in this area. See, for example, M. P. Crosland, ed., The Science of Matter (Baltimore: Penguin Books, 1971); and S. Toulmin and J. Goodfield, The Architecture of Matter (London: Hutchison, 1962).

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materiality has traditionally been cognizable from a study of nature, wherein the examination of material beings provides a clue for one’s rising above the limitation of matter. The first is in the study of the living, where the concept of soul is initially encountered, and where some degree of eminence over the passivity and inertness of matter itself is readily experienced. The second area is the study of knowledge, where one becomes aware of the presence of forms that are not physically united to matter, but somehow exist in it in an intentional or immaterial way. The third area is the study of the first cause of motion or change in the world of nature, which leads one to an awareness of incorporeal or immaterial being, and ultimately to the Author of Nature, God himself. The theme thus far has been that the concept of immateriality has not been eliminated from scientific thought, even though the word itself may rarely appear in its literature. Now it may be noted that the ways in which immateriality reenters into the thoughts of scientists are not particularly helpful for advancing any of the three moves to transcendence just mentioned: indeed more often they can prove to be a hindrance rather than a help in their direction. The point may be illustrated by a brief appraisal of each of these levels of immateriality in order to show how opaque they become to our understanding when we attempt to reach them from their surrogates in modern scientific discourse. Let us begin with the last, the argument for the existence of an incorporeal or immaterial being based on a study of the cosmos, which usually is referred to as a cosmological argument. Aquinas’s clearest proof for the motor causality principle, “Whatever is moved is moved by another,” was based on the divisibility of the material body that is in motion, and was seen by him as a propter quid demonstration. In a previous study the author has sketched the history of this proof from the earliest Greek commentators down to Agostino Nifo, and shown how the ontological thrust of this proof is still intelligible to us in the present day, except that we interpret the motor causality that it im-

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plies in terms of the concept of force, mass, and energy.16 When we have understood Aquinas’s proof of the motor principle through material causality, we gain a full appreciation of the sheer inertness and passivity of the material object as such. Moreover, when we discourse about such an object in terms of force, mass, and energy, we are able to introduce an element of efficiency and activity into the corporeal substrate. Thus we already have grounds for suspecting that elements of the divine may actually be found in matter.17 When we totally absorb motor causality into these scientific terms, however, and allow them to be regarded as technical constructs that have no reference to the real world apart from some theoretical system of which they are a part, then we effectively suppress whatever intimations of transcendence are to be found in the movements of material objects. That is why, for many of our contemporaries, the cosmological argument can be terminated before it is started, or can be so insulated from philosophical inquiry as to nullify its value as a starting point in any search for transcendence.18 A somewhat similar fate awaits the approach to immateriality through intentionality, that is, through an analysis of the requirements of knowledge. In the extensive literature on the mind-body problem, one finds that many philosophers who identify themselves as realists, such as Wilfred Sellars and J. J. C. Smart, feel that mind states are adequately explained in terms of neurons and other forms of biophysical and biochemical energy.19 The development of transistors, solid-state circuitry, and the entire computer industry has done much to buttress this conviction. Knowledge is now proposed 16. William Wallace, “The Cosmological Argument: A Reappraisal,” Proceedings of the American Catholic Philosophical Association 46 (1972): 43–57. 17. Wallace, “The Cosmological Argument: A Reappraisal,” 55. 18. “The Cosmological Argument: A Reappraisal,” 51. 19. Sellers adumbrated his position in his paper “Being and Being Known,” Proceedings of the American Catholic Philosophical Association 34 (1960): 28–49, and has developed it in subsequent publications. See also J. J. C. Smart, Philosophy and Scientific Realism (New York: Humanities Press, 1963).

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as equivalent to information, and this can be transmitted by energy pulses of various types, then stored, classified, translated, and disseminated, all by the operation of computers. So activities that at one time seemed to require a peculiar type of soul, or power of the soul, to transcend matter, now seem explicable in terms of the material substrate alone, endowed as it is with new and hidden sources of energy.20 At the level of life, or of soul, the pattern is the same. Here the growth of molecular biology, particularly research on the DNA molecule and its modes of replication, seem to provide the biologist with all the principles he needs to explain his subject matter. Many philosophers of science think that they can now dispense with teleology and replace it by teleonomy, which effectively would explain all goaldirected behavior in terms of programming that has been engrained in the organism’s genetic material.21 Again the sources of vitality, of immanent activities that were once seen to transcend the inorganic, are apparently reducible to biochemistry: matter seems sufficient of itself to explain them, without recourse to any life principle.

Programmatic Postscript Earlier, it was said that philosophers of science are not particularly helpful for restoring matter to its rightful place in a realist philosophy. This refers to the mainstream of thought in the movement that developed in the United States under the influence of Rudolf Carnap, Hans Reichenbach, and the members of the Wiener Kreis who emigrated to this country in the 1930s.22 In conclusion I should like to 20. It is perhaps noteworthy that the French Jesuit Teilhard de Chardin seized on the energy concept as being capable of bridging the gap between the noosphere, the biosphere, and the lithosphere, but his price for doing this was to insist that all energy is psychical in principle. For the appropriate references and a critique, see my “The Cosmogony of Teilhard de Chardin,” New Scholasticism 36 (1962): 361–76. 21. For a brief discussion, see my Causality and Scientific Explanation, vol. 2 (Ann Arbor: The University of Michigan Press, 1974), 204–5, 213, 312. 22. Representative readings are given in B. A. Brody, ed., Readings in the Philosophy of Science (Englewood Cliffs, N.J.: Prentice-Hall, Inc), 1970.

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suggest a direction this discipline might take to bring itself more in line with a philosophy of nature. Such a move would offer promise for a reinstatement of helpful realist categories: it would also make the concept of immateriality more accessible from within the framework of the philosophy of science. In essence, the development suggested would capitalize on recent discussions of the inadequacy of the “observation-theoretical” dichotomy by showing that many so-called theoretical terms are reducible to the observational, and thus have at least indirect ontological significance.23 In effect, therefore, I advocate that we go about a systematic “unpacking” of the concepts discussed in this paper, to reveal the constructional aspect associated with their mathematical formulation, and to disengage this aspect from the reference they inevitably entail to such traditional concepts as power, nature, matter, and substance.24 A convenient starting point is the concept of force, particularly when this is seen as related to nature as intimated by Galileo and earlier as incorporated into the definition of nature by John Philoponus. The history of the use of force concepts shows that they can be applied indifferently to the force imposed on a material object to move it from without, and to the force exerted by a heavy object as it tends downward toward the earth. Both of these instantiations of force can be sensed directly, and thus pertain to the order of observation. The empirical concept of force builds on this observational base by specifying a metric, or a process of measurement, that permits a quantity to be assigned, say, to the vis gravitatis. The important thing to note in such a transition from the observational to the metrical term, however, is that what is being measured is effectively a power, a vis or virtus associated with the nature of the real entity that is subjected to measurement. This leads to an obvious corollary, namely, that it is 23. See the selections in Brody, Readings in the Philosophy of Science, under “The Observational-Theoretical Distinction,” 224–50. 24. The general background for this proposal is sketched in my “Philosophy of the Physical Sciences: Some New Perspectives,” in Philosophy and Contemporary Man, ed. G. F. McLean (Washington, D.C.: The Catholic University of America Press, 1968), 50–64.

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only when the concept of causal power is reintroduced into the philosophy of science, along lines recently suggested by Rom Harré and Edward Madden, that contact can be re-established with the natural necessities of the real world on which scientific thinking is ultimately based.25 Elsewhere, I have outlined procedures to be employed in this project for the measurement and definition of sensible qualities.26 The key problem is that of assigning dimensional units to qualities of various types: by this I mean motive and resistive powers as well as qualities that are directly sensible to sight and hearing. The technique I advocate uses the concept of weight as a bridge between the concept of force and that of mass. As already intimated, there are many problems associated with mass as it is employed in recent physics. Nevertheless, the basic meanings of gravitational and inertial mass can readily be discerned from the history of their development, and these present no insuperable difficulties. Here we must take courage from Ernst Mach’s reminder that “one can never lose one’s way, or come into collision with facts, if one always keeps in view the path by which one has come.”27 Pursuing this path, it is possible to associate mass, no less than force, with the specific natures or substances of bodies, through the wide range of powers, activities, and reactivities, that lend themselves to experimental inquiry.28 The concepts of energy and field present more difficulty, and in this area additional work needs to be done. As already suggested, the field concept may have more validity as a mathematical construct than as a physical entity, and thus in itself may lack direct physical 25. See R. Harré and E. H. Madden, Causal Powers: A Theory of Natural Necessity (Oxford: Basil Blackwell, 1975); see also Harré’s The Principles of Scientific Thinking (Chicago: The University of Chicago Press, 1970). 26. William Wallace, “The Measurement and Definition of Sensible Qualities,” New Scholasticism 39 (1965): 1–25. 27. Ernst Mach, The History and Root of the Principle of the Conservation of Energy, trans. P. E. Jourdain (Chicago: Open Court, 1911), 17. 28. See Wallace, “The Measurement and Definition of Sensible Qualities,” 11–14.

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reference.29 The concept of energy, on the other hand, seems amenable to treatment along lines similar to those just indicated for the concept of mass. Paul Durbin has already made a promising start in this direction by building on earlier discussions that regard energy essentially as a theoretical construct, and by linking it with the concept of nature, giving it an Aristotelian interpretation.30 If this program can be successfully implemented, and there is no reason why it cannot, a path will be reopened for connecting what many regard as theoretical terms hopelessly embedded in formal system31 with the more readily validated concepts of the philosophy of nature, such as those of substance, nature, and cause. In the context of these latter concepts matter can be understood in its ultimate reality, and ways can be indicated for its authentic transcendence.32 This paper has attempted to show that scientists themselves have already provided many clues for such a project. Those who work unceasingly with matter sooner or later seem to see that it cannot serve as an ad29. Some thinkers, however, attribute a fundamental physical significance to the field concept; see Harré and Madden, Causal Powers, 161–85, and Mendel Sachs, The Field Concept in Contemporary Science (Springfield, Ill.: Charles C. Thomas, 1973). For a benign interpretation of this position, see my Causality and Scientific Explanation, 2:303–7. 30. Paul Durbin, Philosophy of Science: An Introduction (New York: McGraw-Hill Book Co., 1968), 207–14. 31. On theories as partially interpreted formal systems, see the essay by Rudolf Carnap reprinted in Readings in the Philosophy of Science, 190–99, together with the essays immediately following, to 293. 32. We would question, therefore, the attempts made by existential and transcendental metaphysicians to rely on the concept of esse so exclusively as to dispense with matter entirely in their search for transcendence. The German Jesuit, Karl Rahner, for example, sees material reality as conceivable “only and precisely as an essential aspect of spirit,” or “simply as a kind of restricted, in a certain sense, ‘solidified,’ spirit.” Here he employs the term “spirit” as a translation of Aquinas’s esse or existential act. (See his “The Unity of Spirit and Matter,” in Man Before God: Toward a Theology of Man, ed. Juan Alfaro et al. [New York: P. J. Kenedy and Sons, 1966], 41.) For Rahner, Aquinas’s materia prima has no positive meaning in itself, but signifies real negativity and limitation alone. Effectively, therefore, he denies the positive reality of matter and so uses spirit as the preferred starting point for his philosophizing. In our view, American Catholics, living as they do in a materialist culture that is heavily influenced by science, must face up to the reality of the matter if they are ever to point the way to authentic transcendence.

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equate explanatory principle, even for the range of phenomena that come under their scientific purview, to say nothing of man’s total experience of the fully human and divine. Much remains to be done, however, if we are to understand all that their surrogates imply, and to use this to deepen and refine an acceptable content for the concept of immateriality.33 33. A fuller version of this paper appears in the author’s From a Realist Point of View: Essays on the Philosophy of Science (Washington, D.C.: University Press of America, 1979), 287–312.

Part V

Concluding Thoughts

Chapter Fourteen The Case for Developmental Thomism

Chapter Fourteen

The Case for Developmental Thomism

Thomas Aquinas is dead, and surely no one can dispute that. Less factual, and consequently more difficult to answer, is the question whether Thomism is dead. Personally, I regard this as a question of no little importance, one intimately associated with the theme of this convention, whose answer vitally affects the future of our Association. I shall not essay a direct answer. Let me instead be indirect and present a case, a case for what I shall call developmental Thomism. Your attitude to the case I shall present will, I feel, provide your answer to the question whether Thomism is dead. It may also serve to polarize your thoughts on a matter that has caused concern among our membership increasingly in recent years, that of the name and aim of our Association.1 By developmental Thomism I mean Thomism as this developed after the death of St. Thomas; let us oppose it to historical Thomism,

1. A special Committee on Aims and Names of the Association has been studying this matter for several years. A detailed report of their conclusions was presented to the Executive Council meeting on April 7, 1969, at the Forty-Third Annual Convention in New York, at which time it was decided “that no change should be made at present.” Proceedings of the American Catholic Philosophical Association 43 (1969): 233. Since the question continues to be raised, I have appointed a new committee to investigate proposals (235).

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the Thomism of the thirteenth century.2 I am not presenting a case for historical Thomism, not that I am opposed to it, but simply because I feel that such a case has already been argued persuasively.3 And when I say developmental Thomism, I do not intend this in a monolithic, singular sense; I allow the possibility of a plurality of developmental Thomisms, taking the expression in the sense of a genus that allows for considerable specific differentiation.4 With this understood, the case I would present reduces essentially to this: 2. It is always difficult to determine how an “ism” is to be applied to the thought of a philosopher or theologian. After years of prolonged contact with the problem as philosophy editor of the New Catholic Encyclopedia, I prefer to restrict the “ism” to what others have made of the man’s thought: thus “Kantianism” would be the development of the thought of Kant after his death. The immediate exposition and systematization of Thomas’s thought would then be the “historical Thomism” of the thirteenth century; all else would be “developmental Thomism.” 3. Notably by the disciples of Étienne Gilson at the Pontifical Institute of Mediaeval Studies in Toronto; see the fortieth Presidential Address by Joseph Owens, “Scholasticism—Then and Now,” Proceedings of the American Catholic Philosophical Association 40 (1966): 1–16. 4. Inevitably, there will be certain traits that will characterize the genus, and these will be differently listed by various authorities; for a start, see the themes outlined by J. A. Weisheipl, “Thomism,” New Catholic Encyclopedia, (New York: McGraw-Hill, 1967) 14:126–35. The case for pluralism within this genus has been well argued by Ralph M. McInerny, Thomism in an Age of Renewal (New York: Doubleday, 1966), 198–99, as follows: “It should be safe to predict that what we will move toward is not Thomism but Thomisms, any number of ways of truly and philosophically profiting from the study of Aquinas. This plurality of Thomisms will not simply be a function of diversity of talent; it will also be the result of the unavoidable division of philosophical labor. . . . It goes without saying that many questions which occupy Catholic philosophers were undreamt of by Aquinas or were posed by him in a different or more limited fashion. Thomistic positions will doubtless be altered by being put into relation with other views, later views, different vantage points. But of course the task of the philosopher who has learned some things from his study of Aquinas is not to show that he can learn nothing from anyone else. I suspect that Catholic philosophers of the future, all of whom may be called Thomists in some meaningful sense of the term, will bear only a family resemblance to one another . . . As we move away from the baleful influence of the suggestion that there is a substantively orthodox Catholic philosophy, as our philosophizing becomes livelier and, while in continuity with what Aquinas learned, yet distant from what he achieved, we will be on our way toward the Thomism envisaged by Aeterni patris.” See also G. McCool, “Philosophical Pluralism and an Evolving Thomism,” Continuum 2 (1964): 3–16.

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1. Thanks to the revival of Leo XIII, contemporary Thomists, or those who have been trained in its tradition, have entered into dialogue with every philosophical current of interest to the Christian theologian.5 This has stimulated much original thought—new answers have been given to old questions, with the result that there has been a true renewal in Catholic thought.6 This renewal is so deep and so profound that it has produced, among some, a sense of crisis, even of alarm. 2. Yet, viewed against the background of the Church’s long history, this is not an isolated phenomenon; it has been going on for centuries.7 And each major renewal within Catholic thought since the thirteenth century, paradoxically, has prompted a return to the original Thomas. As a result, over the course of history, a certain sustained directedness has appeared. This has resulted in what some call a Thomistic philosophia perennis, not in any sense an eclectic consensus, but rather a sense of recurring intellectual convictions that have stood the test of time and of criticism.8 The vitality of Thomas’s thought appears to be such that, when rethought by others, it is seen 5. No history has as yet been written of this revival of Thomism, begun in the late nineteenth century and continuing through the twentieth. Although there were antecedents, the most easily identifiable starting point was the encyclical of Pope Leo III, Aeterni patris, of August 4, 1879, followed quickly by his founding of the Roman Academy of St. Thomas, of the Leonine Commission to edit the critical text of all Thomas’s writings, and of the Institut Supérieur de Philosophie at Louvain “as a center of studies for promulgating the doctrines of St. Thomas.” 6. Much of the recent impetus has come from the Second Vatican Council, and yet the council itself grew out of the need to bring Catholics in contact with the modern world and its thought, forcibly expressed by prominent Thomists such as M. D. Chenu and Yves Congar. 7. The strongest antidote to any sense of alarm in the present day is a careful study of the history of Catholic thought, especially the evolution of dogma and of theology itself. See the masterful treatises of Yves Congar, Tradition and Traditions, trans. M. Naseby and T. Rainborough (New York: Macmillan, 1967); and A History of Theology, trans. H. Guthrie (New York: Doubleday, 1968), the second of which suffers in English translation. 8. J. A. Weisheipl, Thomism as a Perennial Philosophy (Chicago: The Cardinal Stritch College, 1965).

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to contain virtualities that become more meaningful in the developing course of history. 3. A parallel situation appears in Catholic theology. The future of Catholic theology emerges from its present through a rethinking of its past. So it is, to paraphrase Ernst Mach, that Catholic theology can never lose its way, nor can it come in conflict with the hard data of its sources, if it continues to retrace the path over which it has come.9 But this path is one that has been illuminated often by Thomas; in some special cases, even the hard data provided by the Church’s magisterium have been phrased in his terminology.10 Philosophers who have served the Church and its theology have never been ignorant of this fact. Catholic philosophers who have laid strong claim to the adjective “Catholic” have left the way open to contact with Thomas; they have refused to let others burn the bridges over which the faith has come in its search for understanding. 4. It is this latter effort, consciously or unconsciously pursued by our predecessors, that has given rise to developmental Thomism. To abandon this effort, to make of Thomism something truly dead, a mere historical Thomism that is of antiquarian interest alone, might well be the greatest disservice the Catholic philosopher could do his Church in the present hour of renewal or of crisis.11 9. Mach’s statement, of course, was made not in the context of Catholic theology but in that of the development of modern mechanics when this science was faced with cataclysmic upheavals: “One can never lose one’s footing, or come into collision with facts, if one always keeps in view the path by which one has come.” The History and Root of the Principle of the Conservation of Energy, trans. P. E. Jourdain (Chicago: Open Court, 1911), 17. 10. An extraordinary case was the condemnation of the errors of Peter John Olivi by the Council of Vienne for holding that the rational or intellective soul is not vere ac per se the form of the human body. See Heinrich Denzinger and Adolf Schönmetzer, ed., Enchiridion symbolorum (Barcinone: Herder, 1963), 902. Another is the condemnation of Averroist Aristotelians by the Fifth Lateran Council, likewise for their teachings on the human soul (Denzinger-Schönmetzer, 1440). Many of the decrees of the Council of Trent, of course, followed closely the wording and teaching of Aquinas, especially those concerning justification, the sacraments, and the Eucharist. See the discussion below on transubstantiatio and creatio ex nihilo. 11. Whether this is renewal or crisis depends on one’s viewpoint; the more optimistic view the present situation as renewal, the more pessimistic as crisis.

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This is the case I wish to argue. I realize that it is not a popular one, and possibly I would not venture it were I not a Dominican deeply attached to my brother Thomas, and, more important, one versed in both theology and philosophy. Speaking uniquely as a theologian or uniquely as a philosopher, I doubt that I could even present what I have in mind.12 But since many of you are not only philosophers, but Catholic philosophers as well, and since Divine Providence, in the guise of the ballot box, as it were, has presented you with a philosopher-theologian as president, I ask your kind indulgence.

Contemporary Problematic and Crisis-Renewal I have said that Thomists or those trained in the Thomistic tradition have entered into dialogue with every philosophical current of interest to the Christian theologian. The adequate documentation of that statement alone would require at least a book; I must be content merely with pointing out to you the remarkable diversity and scope of the papers being read at this convention.13 And by way of complementing these, I propose now to touch on a few themes associated with the renewal in Christian theology. I can do this most simply under the rubric of “God-talk,” for this will permit me to embrace developments in analysis and process thought as well as in phenomenology and existentialism. The problem of “God-talk” may be stated as follows.14 Human 12. I say this because of the existential situation in American philosophy and American theology. In philosophy, Catholic thinkers have made it a point never to discuss theological issues; whereas in theology, Catholics seem to have made it a point to avoid philosophy—one of the reasons for adopting the theme of the present convention. 13. This is not to imply that all contributors are Thomists, although many have been educated in the Thomistic tradition. About three papers were rejected for every one accepted, and among those rejected (so as to make room for more stimulating and controversial papers) many were on traditional topics. 14. The topic is obviously suggested by John Macquarrie’s God-Talk (New York: Harper and Row, 1967); see the critical review of this by W. J. Hill, The Thomist 32 (1968): 116–26. In preparing the paragraphs immediately following in the text of my address, I must acknowledge a special debt to Fr. Hill, who is my colleague at the Dominican

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language vocalizes man’s intellectual activity and in one way or another signifies his concepts. Now, if God cannot be embraced in a human concept, what possible ontological value attaches to man’s conceptual activity when God is the subject of his thought and consequently of his talk? The traditional Thomistic answer to this question, as provided, for example, by Cajetan, may be characterized as representational realism.15 According to this answer, all human intellection is basically conceptual, and concepts are representative of things. God can then be known through these creaturely concepts by a process known as analogy: this provides knowledge of God that is not merely negative, saying what God is not, nor merely relative, showing how He is related to all things as their cause, but knowledge that is actually positive and formal, predicating perfections that are known to be in God in a realistic and objective sense. This view of “God-talk,” needless to say, has been strongly contested in recent times. Protestants, true to their intellectual tradition with its distrust of metaphysics and tendency toward agnosticism, have rejected it out of hand.16 For Barth, God is “wholly other,” transcendent and completely opaque to the human intellect.17 For Bultmann, House of Studies, Washington, D.C. Some of the points I touch on and utilize for the purposes of this address are worked out with great care and elaborate documentation in a different context by Fr. Hill in his forthcoming volume, Knowing the Unknown God: An Essay in Theological Epistemology Exploring the Concept of God, to be published by Philosophical Library, New York. 15. Tommaso de Vio Cardinal Cajetan, O.P. (1469–1534); his theory of knowledge is exposed in The Analogy of Names, trans. E. Bushinksi and H. Koren (Pittsburgh: Duquesne University Press, 1959) and in Cajetan: Commentary on Being and Essence, trans. L. H. Kendzierski and F. C. Wade (Milwaukee: Marquette University Press, 1964), as well as in his detailed commentary on the Prima Pars of Aquinas’s Summa Theologiae. 16. The philosophy of Protestantism has been strongly influenced by Kant, who effectively denied the possibility of metaphysics and made God a postulate of the moral order; he denied knowledge “in order to make room for faith.” Representative of contemporary Protestant views are Macquarrie, God-Talk and L. Gilkey, Naming the Worldwind: The Renewal of God-Language (New York: Bobbs-Merrill, 1969). 17. For an introduction to Karl Barth’s thought, see his Dogmatics in Outline (New

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religious truths cannot be objectivized like those of human science, and so whenever revelation is expressed in so-called “objective” terminology, it must be demythologized.18 Brunner, too, stresses the powerlessness of autonomous reason to grasp authentic knowledge of God.19 Tillich alone would concede any power to analogical argument, and for him this extends only to God as Being Itself ; all else is mere symbol.20 So, effectively, Cajetan’s analogical realism is rejected by contemporary Protestantism and in its place is advocated, at best, a symbolic relativism that approaches metaphor more than analogy in the proper sense.21 Yet Protestants are not the only ones who have questioned this traditional understanding. Among the first of the recent Thomists to do so was Sertillanges, who as early as 1906 voiced his preference for agnosticism over anthropomorphism in this matter of “God-talk.”22 And, as is well known, Cajetan’s views on analogy have been subjected to searching criticism as a distortion of Thomas’s original teaching.23 Interesting developments these, but neither has proved nearly so fruitful as the ongoing dialogue with Kantianism and transcendental philosophy that has opened up new vistas in the cognitive evaluation of man’s language about God.

York: Philosophical Library, 1949); for a Catholic appreciation, consult J. Hamer, Karl Barth, trans. D. Maruca (Westminster, Md.: Newman Press, 1962). 18. These themes are exposed in Rudolph Bultmann, Jesus Christ and Mythology (New York: Scribners, 1958); and Existence and Faith, ed. and trans. S. Ogden (New York: Meridian, 1960). 19. Emil Brunner, Revelation and Reason, trans. O. Wyon (Philadelphia: Westminster, 1946); and Dogmatics, vol. 1, The Christian Doctrine of God, trans. O. Wyon (Philadelphia: Westminster, 1950). 20. Paul Tillich’s major work is Systematic Theology, 3 vols. (Chicago: University of Chicago Press, 1951, 1957, 1952); he is best known for his analogia entis, but his use of symbol has been variously interpreted and much argued. 21. This is not to take metaphor in its poetic sense but rather in Cajetan’s sense of improper proportionality. 22. See A. D. Sertillanges, O.P., Agnosticisme ou anthropomorphisme (Paris: Bloud, 1908), a reprint of two articles that appeared in Revue de philosophie (1906). 23. Chiefly by Gilson, C. Fabro, J. H. Nicolas, A. Hayen, B. Mondin and G. P. Klubertanz.

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The movement to which I refer is that of transcendental Thomism, which traces its origin to the scholarly studies on Kant by Joseph Maréchal.24 Maréchal conceded to Kant the subjectivity of human knowing but attempted to overcome this by attributing a dynamism to the knowing subject that ultimately demands an affirmation of Absolute Being. By its native thrust toward the real, Maréchal sees man’s intelligence as led to affirm reality without knowing it in a conceptual way.25 Karl Rahner similarly has urged that the object of metaphysics is not reached by abstraction or by separation but by a transcendental reflection on the activity of understanding itself.26 Influenced by Heidegger, he sees Spirit as in dynamic orientation to unrestricted Being. For Rahner, God is the Absolute who is intelligently present without being objectively seen.27 A related line of thought has been advanced by Emerich Coreth, whose “presuppositionless” metaphysics, centered on establishing the conditions of the possibility of questioning itself, has allowed him to make the passage from the conditioned to the Unconditioned, from finite to Infinite Being.28 Others who can easily be assimilated to this transcendental movement are Bernard Lonergan and Edward Schillebeeckx. Lonergan’s “moving point of view” breaks down the previous static categories of scholastic philosophy.29 For him, reflection precedes judgment,

24. Particularly Joseph Maréchal, Le Point de départ de la métaphysique, cahier 5, Le Thomisme devant la philosophic critique (Paris: Desclee de Brouwer, 1926; 2nd ed. 1949). 25. Maréchal, Le Thomisme, 459, 526, 554. 26. Karl Rahner, Spirit in the World, trans. W. Dych (New York: Herder and Herder, 1968), especially part 2, chaps. 2–4. 27. Karl Rahner, Hearers of the Word, trans. M. Richards (New York: Herder and Herder, 1969), 83; see also C. N. Bent, Interpreting the Word of God (New York: Paulist Press, 1969), 157. 28. Emerich Coreth, Metaphysik (Innsbruck: Tyrolia, 1961), 571; for a summary of Coreth’s thought, see H. J. John, The Thomist Spectrum (New York: Fordham University Press, 1966), 180–192. 29. The main source is Lonergan’s Insight: A Study of Human Understanding (New York: Philosophical Library, 1957, 1965); see also E. MacKinnon, “Understanding According to Bernard J. F. Lonergan, S.J.,” The Thomist 28 (1964): 97–122.

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understanding precedes conceptualization, and new elements are constantly being grasped in spontaneous eruptions of “insight.” Subjectivism is truly present in knowing since every affirmation is also a self-affirmation.30 For Schillebeeckx, too, human knowledge is an unfolding of self-awareness, but in place of Maréchal’s subjective projection of self he proposes a type of objective dynamism.31 All knowledge has a dual aspect in that it is both intuitive and conceptual. The conceptual part is truly objective and, when applied to God, permits the use of an analogy of intrinsic attribution; yet, by virtue of the continuing role of intuition, all conceptualization of God is necessarily developmental.32 This brief sketch of transcendental Thomism may serve to explain how Cajetan’s representational realism has gradually been replaced by several varieties of intuitionalism, all of which have moved Catholic thought closer to the Protestant dialectic. Both speculatively and ecumenically it has led to a renewal of Catholic theology. But even these so-called advances have not gone unchallenged.33 Those working in the Anglo-Saxon analytical tradition and in process philosophy have also been examining the problem of analogy and its use in theological discourse.34 Owing to this current, proposals stemming from Kantian and phenomenological schools have been restated on more empirical and linguistic grounds. Some interpretations, such as those of Leslie Dewart, have been so extreme as to reject analogy

30. Lonergan, Insight, 322. 31. Edward Schillebeeckx, “Faith and Self-Understanding,” The Word in History, ed. T. P. Burke (New York: Sheed and Ward, 1966), 47; also Revelation and Theology, trans. N. D. Smith, 2 vols. (New York: Sheed and Ward, 1967–1968). 32. Schillebeeckx, “Faith and Self-Understanding,” 56; consult also the appendix in vol. 2 of Revelation and Theology, “The Non-Conceptual Intellectual Dimension in Our Knowledge of God According to Aquinas,” 157–206. 33. A penetrating study and critique is J. B. Reichmann, “The Transcendental Method and the Psychogenesis of Being,” Thomist 32 (1968): 449–508; this concentrates mainly on the theories of Rahner and Coreth, with major attention to the latter. 34. By C. Hartshorne, F. Ferré, and J. F. Ross among others.

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completely and to question the objectivity of all dogmatic formulation even on the part of the Church’s magisterium.35 The implications of this proposal for conciliar hermeneutics are vast, since it involves a demythologizing of the entire depositum fidei—a replacement of the message of revelation, previously believed to be handed down unchanged from generation to generation, by ever new interpretations of the Church’s day-to-day lived experience.36 It is understandable why such developments have led some to maintain that Catholic theology is in a state of crisis. The more balanced view, however, would be that such extremes are always found in times of renewal. I would maintain that the current renewal is such that it will once again turn us back to our sources, and that this will sooner or later involve a return to Thomas.

Renewal and Return to Thomas Why this is so may perhaps be seen by a quick glance backward at Second Thomism. We have already mentioned Cajetan, and perhaps with him we can now include all the so-called “Thomists of the Strict Observance,” the favorite whipping boys of recent polemicists.37 Cajetan, like many another thinker who gave impetus to Second Scholasticism, was a developmental Thomism in the best sense of the term. He was alert and finely attuned to the essentialism Scotus had introduced into scholasticism, as he was aware of the empirical turn given it by nominalism.38 Educated at Padua, he came into close contact 35. Leslie Dewart, The Future of Belief: Theism in a World Come of Age (New York: Herder and Herder, 1966). 36. Dewart, The Future of Belief, 8, 49, and passim. 37. Some of the more common epithets are listed by McInerny, Thomism in an Age of Renewal, 16; Sr. Helen James takes R. Garrigou-Lagrange to be representative of “Strict Observance Thomism,” The Thomist Spectrum, 3–15. 38. In this respect, Cajetan differed markedly from his Dominican predecessors, such as John Capreolus (1380–1444), and contemporaries, such as Conrad Koellin (1476– 1536), who exposed and defended Aquinas’s thought but did little to develop it through dialogue and cross-fertilization with other thinkers.

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with Averroism and with the various strains of Renaissance humanism. He entered into prolonged and skillful debate with Pico della Mirandola and with Martin Luther. Even more, he was an assiduous student of Sacred Scripture, accomplished in ancient languages, and an innovator with regard to the biblical hermeneutics of his day.39 The Thomism of Cardinal Cajetan, and this is the point I wish to make, was subjected to so many influences undreamt of by the Angelic Doctor that one should not be surprised that his Thomism is quite different from that of Thomas. What could be more predictable than that such a scholar would not merely rephrase Aquinas, not merely translate him into the idiom of his day, but would rethink and develop the thought of his master in the light of new knowledge? But then the key questions: Did Cajetan’s prolonged contact with his Scotistic adversaries actually corrupt him?40 Did he become too essentialistic, too univocal in his predications? Such might be the judgment passed on him by the existential metaphysicians of recent years.41 The same point can be made with Spanish Thomists in the generation immediately after Cajetan. Let me single out only Francisco de Vitoria and Domingo de Soto. Vitoria is well known for his pioneering work in international law; less known perhaps is Soto’s extraordinary contributions to physical science.42 My own recent researches have been in Soto’s mechanics, and it is truly remarkable how this Salamancan professor went far beyond Aristotle’s physics, steering 39. For details, see J. F. Groner, Kardinal Cajetan (Fribourg: University Press, 1951); also P. O. Kristeller, Le Thomisme et la pensée italienne de la renaissance (Montreal: Institut d’Études Médiévales, 1967). 40. The Franciscan Antonio Trombetta (1436–1517) was one of Cajetan’s principal targets at Padua; he is singled out for attack in Cajetan’s commentary on the De ente et essentia. 41. E.g., G. P. Klubertanz, St. Thomas Aquinas on Analogy (Chicago: Loyola University Press, 1960). 42. Francisco de Vitoria (1483–1546) taught at Saint-Jacques in Paris in the early decades of the sixteenth century; one of his auditors there was his countryman, Francisco de Soto (1494–1560), who became a convert to Thomism through Vitoria’s efforts and later entered the Dominican Order, taking the name of Domingo.

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a middle path between the nominalists and the ultra-realists of his time, to adumbrate the law of falling bodies some ninety years before Galileo.43 But were Vitoria and Soto pure Thomists? Were they not infected with nominalism, just as Cajetan was infected with ultrarealism? Of course they were.44 They were developmental Thomists, and the brand of Thomism they evolved proved new, and exciting, and provocative in its day.45 Need I go on? Vitoria and Soto were followed at Salamanca by the Toledos and by the Suárezes,46 and then, in only a few short years, by a whole host of Cartesian and Wolffian scholastics, who incorporated, and modernized, and systematized, and gave form to the philosophia perennis that has come to be so widely caricatured on the contemporary scene.47 But while this went on, there were those who continued to cast an eye back on Thomas.48 In the light of the new knowledge, they were able to read his writings in a different way, and they could find new meanings that answered the pressing intellectual problems that 43. W. A. Wallace, “The Concept of Motion in the Sixteenth Century,” Proceedings of the American Catholic Philosophical Association 41 (1967): 184–95; “The Enigma of Domingo de Soto: Uniformiter difformis and Falling Bodies in Late Medieval Physics,” Isis 59 (1968): 384–401; and “The ‘Calculatores’ in Early Sixteenth-Century Physics,” British Journal of the History of Science 4 (1969): 221–32. 44. For an extended analysis, see M. Solana, Historia de la Filosofía Española: Epoca del Renacimiento (Siglo 16), 3 vols. (Madrid: Consejo Superior de Investigaciones Científicas, 1941). 45. As attested, for example, by Soto’s election to the vespertinal chair of theology at Salamanca by student acclamation; see V. Beltrán de Heredia, Domingo de Soto, O.P., Estudio biográfico documentado (Salamanca: Biblioteca de Teologos Españoles, 1960), 68–77. 46. Francisco de Toledo, S.J., (1532–1596) studied theology under Soto at Salamanca; Francisco Suárez, S.J., (1548–1617) composed his Disputationes Metaphysicae while teaching there. 47. During this period, scholasticism became a variation of rationalism; see J. E. Gurr, The Principle of Sufficient Reason in Some Scholastic Systems, 1750–1900 (Milwaukee: Marquette University Press, 1959). 48. Worthy of mention here is Salvatore Roselli (d. 1784), Vicenzo Buzzetti (1777– 1824), Serafino Sordi (1793–1865), Domenico Sordi (1790–1880), and Gaetano Sanseverino (1811–1865).

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continued to arise. Thus it was that, late in the nineteenth century, the movement sometimes referred to as Third Thomism got under way.49 Third Thomism was developmental Thomism in a far more explicit sense than was Second Thomism. I have already touched on the work done at Louvain in dialogue with Kant; I would also mention the equally profound contributions of Garrigou-Lagrange and Maritain in dialogue with Bergson,50 of those who searched Blondel and personalist and existentialist philosophers for new insights into Christian philosophy.51 There were still others—and the names of Gilson and Geiger and Fabro come immediately to mind—who were prompted by this very development to revert to the original Thomas.52 Here, too, more was found in the original text than earlier centuries had been able to find there. So it is that the most interesting themes in the Thomistic corpus, such as ipsum esse and ipsum intelligere, are only now being subjected to searching analysis for the light they can shed on the contemporary problematic.53

The Evolution of Catholic Theology Why this cyclical return to Thomas seems to occur is not easy to answer, and I cannot attempt that here. On the intrinsic merits of Thom-

49. In its earlier stages, because of the influence of Maurice De Wulf, Scholasticism Old and New, trans. P. Coffey (New York: Benziger, 1907), this movement was referred to as Neo-Scholasticism; later historical studies showed that there was no single, consistent body of thought that characterized the High Middle Ages, and the term Neo-Thomism began to supplant Neo-Scholasticism. Then, because the prefix “neo” seemed to negate true Thomism, this too was gradually abandoned. 50. For a brief sketch of this dialogue, see John, The Thomist Spectrum, 3–31. 51. E.g., Pierre Rousselot, Joseph de Finance, André Hayen, and Maurice Nédoncelle. 52. Much of this activity was concentrated on clarifying the notions of existence and participation; for a summary, see John, The Thomist Spectrum, 32–51 (Gilson), 87–107 (Fabro), and 108–22 (Geiger). 53. The first has received extensive attention from Gilson and his disciples at Toronto and from Fabro, while the second has become a focal point for Lonergan and his disciples.

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as’s thought alone, possibly it is because First Thomism stood at a watershed in intellectual history, that it made a most viable synthesis of Aristotelianism and Platonism, and thus included all of the basic options that were to be explored in the centuries to come.54 If I be allowed to take into account extrinsic factors, there can be no denying that the affinity of Thomas’s synthesis with Christian revelation explains its perennial attraction to those who would philosophize in a Christian context, and who would place their thought at the service of theology.55 Mention of this last point allows me to return to an earlier theme—the proximity of Thomas’s thought to the sources of revelation, and particularly to the terminology of the magisterium. This will lead me into a brief examination of the problem of hermeneutics, and especially of conciliar hermeneutics, a major source of alarm in contemporary Catholic circles. Here two paradigms that are readily available for discussion are the teaching of the Council of Trent on transubstantiation and the teaching of the First Vatican Council on creation. The Council of Trent was intent on clarifying Catholic belief in the real presence of Christ in the Eucharist and spoke of this in terms of transubstantiation,56 a concept readily understood in the Thomistic tradition.57 Recent theologizing, under the influence of phenomenology, has attempted a reexamination of the notion of real presence and has restated the doctrine of transubstantiation in other terms such 54. On this see Cornelio Fabro, “Platonism, Neo-Platonism and Thomism: Convergencies and Divergencies,” The New Scholasticism 44 (1970): 69–100; other insights are provided in Fernand van Steenberghen, Le Retour à saint Thomas a-t-il encore un sens aujourd’hui? (Montreal: Institut d’Études Médiévales, 1967). 55. Papal approval, of course, has done much to enhance Aquinas’s attraction; see Santiago Ramírez, “The Authority of St. Thomas Aquinas,” The Thomist 15 (1952): 1–109. The classical source is J. J. Berthier, Sanctus Thomas Aquinas “Doctor Communis” Ecclesiae (Rome: Editrice Nazionale, 1914). 56. Denzinger-Schönmetzer, Enchiridion symbolorum, 1642, 1652. 57. Thomas Aquinas, Summa Theologiae III, q. 75, aa. 4, 8; In IV Sent., dist. 8, q. 2, a. 1; q. 1, a. 3, ad unum.

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as transignification and transfinalization.58 In the analysis of Schillebeeckx, for example, the Tridentine conciliar Fathers thought that real presence necessarily implied substantial change, being unaware that their decrees were finalized in a time-conditioned language and thought-form.59 Stating the doctrine in more contemporary terms, Schillebeeckx would have Christ’s presence in the Eucharist per modum substantiae actually mean that he is present in an extraordinary way, in a “spiritual” way, as opposed to the corporal presence that people ordinarily experience. From this, Schillebeeckx argues that there is no physical change at transubstantiation.60 Rather, the reality that was bread becomes “the substantial sign” of the presence of Christ. This, in Schillebeeckx’s terminology, is “ontic” change without being physical; it can explain the “real presence” of Christ in the Eucharist without having to invoke an archaic concept such as transubstantiation.61 Consider an analogous problem in attempting to update the teaching of Vatican I on creation from nothing, at the beginning of time, and so forth, with contemporary developments in process theology and evolution.62 Or, to take a simpler case, the problem of hominization, where Catholic theology has always acknowledged a “breach in continuity,” explainable by the immediate and direct action of God

58. For a survey, see J. M. Powers, Eucharistic Theology (New York: Herder and Herder, 1967); earlier surveys are those of Cyril Vollert, “The Eucharist: Controversy on Transubstantiation,” Theological Studies 22 (1961): 391–425; and J. T. Clark, “Physics, Philosophy, Transubstantiation, Theology,” Theological Studies 12 (1951): 24–51. 59. In articles in Flemish that appeared in 1965 and 1966, summarized in Powers, 139–53; see also Schillebeeckx’s “Transubstantiation, Transfinalization, Transfiguration,” Worship 40 (1966): 324–38. 60. Remarks following a paper by S. Trooster, S.J., in 1962; summarized in Powers, Eucharistic Theology, 129–31. 61. Powers, Eucharistic Theology, 130–31; Schillebeeckx does not reject transubstantiation, but attempts to explain Trent’s formulation in more phenomenological terms. 62. Particularly parts of the dogmatic constitution Dei Filius (Denzinger-Schönmetzer, Enchiridion symbolorum, 3000–3002), restating the decree Firmiter of the Fourth Lateran Council (Denzinger-Schönmetzer, Enchiridion symbolorum, 800).

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in creating the human soul.63 Contemporary theologizing on this by Rahner, under the influence of Heidegger, has produced the concept of “active self-transcendence” to explain how the higher can emerge from the lower, presupposing God’s causality as the ground of all being.64 This Rahner sees as giving a fuller understanding of a truth touched upon by St. Thomas in his distinctive teaching on divine causality.65 So we have transignification and active self-transcendence giving us a better and more accurate understanding of real presence and God’s creative activity than transubstantiatio and creatio ex nihilo. Now, as a philosopher of science who is interested in Catholic theology, does it make sense for me to ask: When I talk about physical substances such as bread and wine, how can there be an ontic change that is truly real but is in no way physical?66 Or, if the so-called creation of the human soul involves nothing more than active selftranscendence on the part of the parents, why say that this requires any more direct and immediate action of God than other phenomena of nature in process of evolution?67 And now let me rejoin my earlier exposition of “God-talk.” If man can in no way know Absolute 63. The expression “breaches of continuity” is used by Pierre Teilhard de Chardin in the Preface to The Phenomenon of Man (New York: Harper, 1959) to introduce his theological footnotes: “At most I am confident that, on the plane of experience, I have identified with some accuracy the combined movement towards unity, and have marked the places where philosophical and religious thinkers, in pursuing the matter further, would be entitled, for reasons of a higher order, to look for breaches of continuity” (29). See also 169n1, where Teilhard makes the application to creation of the human soul. 64. Karl Rahner, Hominisation: The Evolutionary Origin of Man as a Theological Problem (New York: Herder and Herder, 1965), 62–101. 65. In this context, special note is given of Aquinas’s teaching on physical premotion, Rahner, Hominisation, 74, 77–80. 66. Paul VI’s encyclical Mysterium fidei stressed that the bread and wine, after the words of consecration, contain a new reality that is properly called ontological (“novam continent realitatem, quam merito ontologicam dicimus”), Acta Apostolicae Sedis 57 (1965): 753–74, esp. 764; English translation in The Pope Speaks 10 (1965): 309–28. 67. Robert North reasons in this fashion in his Teilhard and the Creation of the Soul (Milwaukee: Bruce, 1967), 228–60. Rahner rightfully rejects North’s interpretation of his thought in an introduction to North’s book, ix–xii.

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Being by his intellect, but requires the dynamism of his will or some spontaneous intuition or a living experience for its affirmation, how can there be a true conceptual development in any discourse about God?68 Can theology even be a “science,” in any sense of that term acceptable to our contemporaries?69

The Task of the Catholic Philosopher My concern here is a serious one. Could it be that our theologians, in their attempt to find new meanings in old dogmatic formulas, have underestimated the perennial ability of human reason to grasp the fundamental certitudes on which a science such as theology must be based? I wonder if a new fideism is not now actually under way.70 It is truly remarkable to me that present-day theologians are voicing the opinion that philosophers should give up their search for certitude, for final answers, and begin to elaborate imaginative systems that will serve as vehicles for ever new theologies.71 If philosophers do this, who will keep these same theologians honest? Who will check their 68. See Reichmann, “The Transcendental Method”; and A. J. Kelly, “To Know the Mystery: The Theologian in the Presence of the Revealed God,” The Thomist 32 (1968): 1–66, 171–200. 69. There is a tendency, of course, to reduce all of science to mere dialectics; this has been abetted in some circles by the favorable reception of T. S. Kuhn, The Structure of Scientific Revolutions (Chicago: University of Chicago Press, 1962). Kuhn’s thesis, if not properly understood, could easily lead to complete relativism; on this, see Ian Barbour, Issues in Science and Religion (Englewood Cliffs, N.J.: Prentice Hall, 1966), 153–56; and Dudley Shapere, Philosophical Problems of Natural Science (New York: Macmillan, 1965), 17–19. 70. By fideism I mean the denial to the human intellect of the capacity to attain any certitudes, leaving these entirely as matters of faith. If faith has no reasonable basis, its credibility must rely on subjective factors, and this leads inevitably to relativism. 71. A Protestant expression of this view is that of Frederick Sontag: “When philosophy regains its rightful place, . . . it becomes less certain but also more flexible so that theology can once again utilize its support. Theology is in need of such philosophy because its basic principles and procedures are not fixed but must be worked out openly in the face of a variety of alternatives.” The Future of Theology: A Philosophical Basis for Contemporary Protestant Thought (Philadelphia: Westminster, 1969), 24.

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intuitions, who will argue as to where reason stops and faith begins, if reason is never able to establish its basic claims, to which all human sciences, theology included, must ultimately conform?72 So I return to my original question. Is Thomism really dead? Perhaps we should admit that Second Thomism died in the Schoolmen’s vain attempt to assimilate Descartes, and Leibniz, and Wolff into a viable synthesis.73 Possibly a like fate awaits Third Thomism in its effort to do the same for Kant, and Hegel, and Husserl, and Heidegger.74 The very notion of a developmental Thomism implies that possibility. But then even the “developers” have to be kept honest; their insights and intuitions have to stand to reason. So enter here the philosophers, particularly those interested and zealous philosophers who just happen to be Catholic. I must admit to difficulty with the “Christian philosophers,” particularly when the “Christian” exerts an overriding influence on the “philosophy.”75 Surely, however, there is 72. Here the theologian is at a disadvantage precisely because of his faith commitment. Possibly the same could be said for the philosopher who works on insight and intuition; how can he be sure that his is not a privileged insight not shared by the majority of men? It is here that analytical philosophy can offer a valuable antidote to phenomenology and existentialism, as was pointed out by Ernan McMullin in the forty-first Presidential Address: “The ‘analytic’ approach to philosophy, as it has been called, is still not much represented among us. But if ever we needed it, to my mind, it is now. One of our major tasks in the next decade will undoubtedly be to keep our theologians honest, to keep asking them what they mean and how they propose to support it.” Proceedings of the American Catholic Philosophical Association 41 (1967): 13. I would further maintain that one of the precise advantages of developmental Thomism is that it is able to mediate between analysis and existential phenomenology; see my “Thomism and Modern Science: Relationships Past, Present, and Future,” The Thomist 32 (1968): 67–83, esp. 81. 73. It was not the rise of modern science that brought about the demise of Second Scholasticism but rather the rationalistic interpretation of seventeenth-century science, owing to its early success with mathematical methods, which gradually worked its way into philosophy and theology. 74. “Indiscriminate mixing of Husserl or Heidegger or Whitehead or Russell or Wittgenstein with the Scholastic notions will have the same disastrous effects as the earlier Neoscholastic attempts to incorporate Descartes or Wolff or Kant.” Owens, “Scholasticism—Then and Now,” 10. 75. By “Christian philosophy” I do not mean the historical interpretation given this expression by Gilson but rather the Blondelian sense of a philosophy that takes explicit

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a role here for dispassionate, hard-headed thinkers, who are willing to examine topics of interest to Catholics but who will be critical of any too facile attempt to exploit reason or to prostitute it, even for such a noble cause. It is to such an aim, among others, that I believe this Association is dedicated.76 I submit that we will achieve that aim well if we can always find our way back to Thomas and, in his light, vindicate the rights of reason in the service of our faith.77 account of the fact of Christianity and conducts its inquiry in such a way as to be open to, and even make appeal to, values that transcend the order of nature. See M. Nédoncelle, Is There a Christian Philosophy?, trans. I. Threthowan (New York: Hawthorn Press, 1960). 76. This need not even be the primary aim of the Association, nor need it coincide with the principal intention of its founders; in the present day, however, it offers a forceful argument for Catholics to continue to associate, as a group, in the philosophical enterprise. 77. If our Thomism is developmental, again to revert to Ernst Mach, we should have no difficulty retracing the path along which we have come; when we get back to Thomas, we will be with a man who was kept honest, in theological matters, by the pagan Aristotle, with whose thought he daily wrestled, and by the Latin Averroists who allowed him no liberties in the benign interpretation of his master.

Bibliography of William A. Wallace, O.P. Bibliography of William A. Wallace, O.P.

Lifetime Bibliography of William A. Wallace, O.P.

This bibliography draws upon and updates the list of publications provided in Nature and Scientific Method, edited by Daniel O. Dahlstrom, Studies in Philosophy and the History of Philosophy, vol. 22 (Washington, D.C.: The Catholic University of America Press, 1991). It is arranged chronologically according to the major periods of Wallace’s scholarly career.

Wartime Research (1941–1946) “Subsurface Pressure Changes Caused by Waves.” Mine Unit Report 365 (November 1941). Washington, D.C.: Naval Ordnance Laboratory, 1941. “Pressure Fields Beneath the U.S.S. North Carolina.” Mine Unit Report 387 (December 1941). Washington, D.C.: Naval Ordnance Laboratory, 1941. “Pressure Background in Relation to Mine Design.” Naval Ordnance Laboratory Report 451 (March 1942). Washington, D.C.: Naval Ordnance Laboratory, 1942. “Study of Ships’ Hull Vibration and Associated Low Frequency Pressure Fields.” Naval Ordnance Laboratory Report 509 (May 1942). Washington, D.C.: Naval Ordnance Laboratory, 1942. “Preliminary Study of Subsonic Background.” Naval Ordnance Laboratory Report 540 (August 1942). Washington, D.C.: Naval Ordnance Laboratory, 1942. “Maximum Rates of Change of Tides in Various Parts of the World.” Naval Ordnance Laboratory Monograph 2159 (August 1942). Washington, D.C.: Naval Ordnance Laboratory, 1942. “Subsurface Pressure Variations at Kahului Harbor.” Naval Ordnance Laboratory Report 596 (December 1942). Washington, D.C.: Naval Ordnance Laboratory, 1942. “Special Mining Report.” Coauthored with Ellis A. Johnson in 1944 and

263

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described in Samuel Eliot Morison, History of United States Naval Operations in World War II. Boston: Little Brown and Company, 1947–1962. “Tactics of Inner Zone Mining Campaign Against Japan: Operation Starvation.” Report of the 20th U.S. Air Force (August 1945). Summarized in Ellis A. Johnson and David A. Katcher, Mines Against Japan. White Oak, M.D.: Naval Ordnance Laboratory, 1974. “Offensive Mining Campaign Against Japan.” U.S. Strategic Bombing Survey (1946). Summarized in Ellis A. Johnson and David A. Katcher, Mines Against Japan. White Oak, Maryland: Naval Ordnance Laboratory, 1974.

Graduate Studies & Early Scholarship (1952–1962) “The Origin of the Universe.” Coauthored with M. J. Davis. Dominicana 37, no. 1 (1952): 25–38, 181–95. “Absorption of Finite Amplitude Sound Waves.” Coauthored with F. E. Fox. Journal of the Acoustical Society of America 26, no. 6 (1954): 994–1006. Physics and God: A Statement and Defense of the Prima Via in Light of Modern Science. Lector of Sacred Theology diss., Pontifical Faculty of the Immaculate Conception, 1954. “Newtonian Antinomies Against the Prima Via.” The Thomist 19, no. 2 (1956): 151–92. “Some Demonstrations in the Science of Nature.” In The Thomist Reader, edited by the Dominicans of St. Joseph Province, 90–118. Washington, D.C.: The Thomist Press, 1957. The Scientific Methodology of Theodoric of Freiberg: A Case Study of the Relationship between Science and Philosophy. PhD diss., University of Freiberg. Studia Friburgensia, n.s., 26. Fribourg: University Press, 1959. “St. Thomas Aquinas, Galileo, and Einstein.” The Thomist 24, no. 1 (1961): 1–22. “Gravitational Motion According to Theodoric of Freiberg.” The Thomist 24, nos. 2–4 (1961): 327–52. “Theology and the Natural Sciences.” In Theology in the Catholic College, edited by R. Masterson, 167–204. Dubuque, Iowa: Priory Press, 1961. The Role of Demonstration in Moral Theology: A Study of Methodology in St. Thomas Aquinas. Doctor of Sacred Theology diss., Pontifical Faculty of the Immaculate Conception. Texts and Studies 2. Washington, D.C.: The Thomist Press, 1962. “The Cosmogony of Teilhard de Chardin.” New Scholasticism 36, no. 3 (1962): 353–67. “Science and Religion in the Twentieth Century.” Homiletic and Pastoral Review 63, no. 1 (1962): 23–31.

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“The Place of Science in Liberal Arts Curriculum.” Catholic Educational Review 60, no. 6 (1962): 361–76. “Metaphysics and the Existence of God.” New Scholasticism 36, no. 4 (1962): 529–31. “Natural Philosophy and the Physical Sciences.” In Philosophy and the Integration of Contemporary Catholic Education, edited by G. F. McLean, 130–57, 292–97. Washington, D.C.: The Catholic University of America Press, 1962.

Studies in Faith, Philosophy & Science (1963–1975) Einstein, Galileo and Aquinas: Three Views of Scientific Method. Washington, D.C.: The Thomist Press, 1963. “Modern Science: A Challenge to Faith?” Proceedings of the Society of Catholic College Teachers of Sacred Doctrine 9 (1963): 96–117. “The Thomistic Order of Development in Natural Philosophy.” In Teaching Thomism Today, edited by G. F. McLean, 247–70. Washington, D.C.: The Catholic University of America Press, 1963. “Nuclear Weapons, Morality, and the Future.” Dominicana 48, no. 1 (1963): 7–21. “Radiation and Social Ethics.” America 108 (June 22, 1963): 880–83. “The Reality of Elementary Particles.” Proceedings of the American Catholic Philosophical Association 38 (1964): 154–66. “Theodoric of Freiberg on the Structure of Matter.” In Proceedings of the Tenth International Congress of the History of Science, edited by Henry Guerlac, 1:591–97. Paris: Hermann, 1964. “St. Thomas and the Pull of Gravity.” In Science and the Liberal Concept, edited by Frederick D. Rossini, William A. Wallace, and James A. Shannon, 143–65. West Hartford, Conn.: St. Joseph College, 1964. “Cybernetics and a Christian Philosophy of Man.” In Philosophy in a Technological Culture, edited by G. F. McLean, 124–45. Washington, D.C.: The Catholic University of America Press, 1964. “The Measurement and Definition of Sensible Qualities.” New Scholasticism 39, no. 1 (1965): 1–25. “Some Moral and Religious Aspects of Nuclear Technology.” Journal of the Washington Academy of Sciences 55, no. 4 (1965): 85–91. Cosmogony [St. Thomas Aquinas, Summa Theologiae, vol. 10 (Ia, qq. 65–74)]. Edited and translated with commentaries. New York: McGraw-Hill, 1967.

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New Catholic Encyclopedia, 15 vols. Staff editor for philosophy and author of 31 articles. New York: McGraw-Hill, 1967 “The Concept of Motion in the Sixteenth Century.” Proceedings of the American Catholic Philosophical Association 41 (1967): 184–95. “Il tomismo e la scienza moderna: passato, presente e future.” Sapienza 20 (1967): 429–43. “The Enigma of Domingo de Soto: Uniformiter difformis and Falling Bodies in Late Medieval Physics.” Isis 59, no. 4 (1968): 384–401. “Elementarity and Reality in Particle Physics.” In Proceedings of the Boston Colloquium for the Philosophy of Science, edited by R. S. Cohen and M. W. Wartofsky, 236–71. Boston Studies in the Philosophy of Science 3. Boston: D. Reidel Publishing, 1968. “Toward a Definition of the Philosophy of Science.” In Mélanges à la mémorie de Charles de Koninck, 465–85. Quebec: Les Presses de l’Université Laval, 1968. “Philosophy of the Physical Sciences.” In Philosophy and Contemporary Man, edited by G. F. McLean, 50–64. Washington, D.C.: The Catholic University of America Press, 1968. “Thomism and Modern Science: Relationships Past, Present, and Future.” The Thomist 32, no. 1 (1968): 67–83. “The ‘Calculatores’ in Early Sixteenth-Century Physics,” British Journal for the History of Science 4, no. 3 (1969): 221–32. “The Case for Developmental Thomism.” Proceedings of the American Catholic Philosophical Association 44 (1970): 1–16. “Mechanics from Bradwardine to Galileo.” Journal of the History of Ideas 32, no. 1 (1971): 15–28. Causality and Scientific Explanation. Vol. 1, Medieval and Early Classical Science. Ann Arbor: University of Michigan Press, 1972. “The Cosmological Argument:A Reappraisal.” Proceedings of the American Catholic Philosophical Association 46 (1972): 43–57. “Review of Anthony Kenny’s The Five Ways.” The Thomist 36, no. 4 (1972): 721–24. “Experimental Science and Mechanics in the Middle Ages.” In Dictionary of the History of Ideas, edited by Philip P. Wiener, 2:196–205. New York: Charles Scribner’s Sons, 1973. Causality and Scientific Explanation. Vol. 2, Classical and Contemporary Science. Ann Arbor: University of Michigan Press, 1974. “Three Classics of Science.” In The Great Ideas Today, edited by John Van Doren, 211–72. Chicago: Encyclopaedia Britannica, 1974.

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“Theodoric of Freiberg: On the Rainbow.” In A Source Book in Medieval Science, edited by Edward Grant, 435–41. Cambridge, Mass.: Harvard University Press, 1974. “Galileo and the Thomists.” In St. Thomas Aquinas Commemorative Studies 1274–1974, edited by Armand Maurer, 2:293–330. Toronto: Pontifical Institute of Mediaeval Studies, 1974. “Aquinas on the Temporal Relation between Cause and Effect.” Review of Metaphysics 27, no. 3 (1974): 569–84. “Aquinas on Creation: Science, Theology, and Matters of Fact.” The Thomist 38, no. 3 (1974): 485–523. “Ellis A. Johnson, 1906–1973.” Coauthored with T. Page and G. S. Pettee. Operations Research 22, no. 6 (1974): 1141–55. “Cosmological Argument.” In New Catholic Encyclopedia. Vol. 16, Supplement 1967–1974, 105–8. New York: Publishers Guild, 1974. “Contemporary Philosophers.” In New Catholic Encyclopedia. Vol. 16, Supplement, 1967–1974, 341–48. New York: Publishers Guild, 1974. “Recent Developments in Philosophy.” In New Catholic Encyclopedia. Vol. 16, Supplement, 1967–1974, 348–51. New York: Publishers Guild, 1974. “The First Way: A Rejoinder.” The Thomist 39, no. 2 (1975): 375–82.

Galileo Research & Studies in the History & Philosophy of Science (1976–1993) “Galileo and Reasoning Ex suppositione: The Methodology of the Two New Sciences.” In Proceedings of the 4th Biennial Meeting of the Philosophy of Science Association, edited by R. S. Cohen, C. A. Hooker, A. C. Michalos, and J. W. van Evra, 79–104. Boston Studies in the Philosophy of Science 32. Boston: D. Reidel Publishing, 1976. “Buridan, Ockham, Aquinas: Science in the Middle Ages.” The Thomist 40, no. 3 (1976): 475–83. “El enigma de Domingo de Soto: Uniformiter difformis y la caida de los cuerpos en la tardia fisica medieval.” Studium 16 (1976): 343–67. The Elements of Philosophy: A Compendium for Philosophers and Theologians. New York: Alba House, 1977. Galileo’s Early Notebooks: The Physical Questions: A Translation from the Latin with Historical and Paleographical Commentary. Notre Dame: University of Notre Dame Press, 1977. “Galileo Galilei and the Doctores Parisienses.” In New Perspectives on Galileo,

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edited by R. E. Butts and J. C. Pitt, 87–138. Dordrecht:D. Reidel Publishing, 1978. “The Philosophical Setting of Medieval Science.” In Science in the Middle Ages, edited by David C. Lindberg, 91–119. Chicago: University of Chicago Press, 1978. “Causality, Analogy, and the Growth of Scientific Knowledge.” In vol. 9 of Tommaso d’Aquino nel suo settimo centenario, 26–40. Naples: Edizioni Domenicane Italiane, 1978. “Galileo’s Knowledge of the Scotistic Tradition.” In vol. 2 of Regnum Hominis et Regnum Dei, edited by Camille Bérubé, 313–20. Rome: Societas Internationalis Scotistica, 1978. “Causes and Forces in Sixteenth-Century Physics.” Isis 69, no. 3 (1978): 400–12. “El concepto de movimiento en el siglo XVI.” Studium 18 (1978): 91–106. “Immateriality and Its Surrogates in Modern Science.” Proceedings of the American Catholic Philosophical Association 52 (1978): 28–83. From a Realist Point of View: Essays on the Philosophy of Science. Washington, D.C.: University Press of America, 1979. Rev. ed. 1983. “Medieval and Renaissance Sources of Modern Science.” Proceedings of the Patristic Medieval & Renaissance Studies Conference 2 (1979): 1–17. “Philosophical Pluralism.” In New Catholic Encyclopedia, vol. 17, supplement 1979, 510–12. New York: Publishers Guild, 1979. “Thomism.” In New Catholic Encyclopedia, vol. 17, supplement 1979, 665–66. New York: Publishers Guild, 1979. “The Scientific Methodology of St. Albert the Great.” In Albertus Magnus Doctor Universalis 1280–1980, edited by G. Meyer and A. Zimmerman, 385–407. Mainz: Matthias Grünewald Verlag, 1980. “Albertus Magnus on Suppositional Necessity in the Natural Sciences.” In Albertus Magnus and the Sciences, edited by James A. Weisheipl, 103–28. Toronto: Pontifical Institute of Mediaeval Studies, 1980. “Galileo’s Citations of Albert the Great.” In Albert the Great:Commemorative Essays, edited by F. J. Kovach and R. W. Shahan, 261–83. Norman, Okla.: University of Oklahoma Press, 1980. In Dictionary of Scientific Biography, edited by C. C. Gillispie. New York: Charles Scribner’s Sons, 1970–80. “Albertus Magnus,” 1:99–103. “Thomas Aquinas.” 1:196–200 “Bernard of Le Treille.” 2:20–21. “Theodoric Borgognoni of Lucca.” 2:314–15.

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“Francesco Buonamici.” 2:590–91. “Juan de Celaya.” 3:171–72. “Pedro Ciruelo.” 3:280. “Luis Nuñez Coronel.” 3:420–21. “Dietrich von Freiberg.” 4:92–95. “Jean Dullaert of Ghent.” 4:237–38. “Gerard of Silteo.” 5:361. “Giles (Aegidius) of Lessines.” 5:401–2. “Gaspar Lax.” 8:100. “John Major.” 9:32–33. “Domingo de Soto.” 12:547–48. “Alvaro Thomaz.” 13:349–50. “Ulrich of Strassburg.” 13:534. “Vincent of Beauvais.” 14:34–36. “William of Auvergne.” 14:388–89. “Maritain and the Notion of Scientific Progress.” Notes et Documents (International Maritain Institute, Rome) 19 (1980): 21–26, and 20 (1980): 28–35. Prelude to Galileo: Essays on Medieval and Sixteenth-Century Sources of Galileo’s Thought. Boston Studies in the Philosophy of Science 62. Boston: D. Reidel Publishing, 1981. “Galileo and Scholastic Theories of Impetus.” In Studi sul XIV secolo in memoria de Anneliese Maier, edited by A. Maieru and A. Paravicini Bagliani, 275–97. Rome: Edizioni di Storia e Letteratura, 1981. “Aristotle and Galileo: The Uses of Hupothesis (Suppositio) in Scientific Reasoning.” In Studies in Aristotle, edited by D. J. O’Meara, 47–77. Studies in Philosophy and the History of Philosophy 9. Washington, D.C.: The Catholic University of America Press, 1981. Religion and Science: Must There be Conflict? Third Annual Moreau Lecture. Wilkes-Barre, Penn.: King’s College, 1982. “St. Thomas’s Conception of Natural Philosophy and Its Method.” In La Philosophie de la nature de Saint Thomas d’Aquin, edited by Leo Elders, 7–27. Studi Tomistici, 18. Rome: Libreria Editrice Vaticana, 1982. “Aristotle in the Middle Ages.” In vol. 1 of Dictionary of the Middle Ages, edited by J. R. Strayer, 456–69. New York: Charles Scribner’s Sons, 1982. “Comment on James A. Weisheipl’s ‘Avicenna and Aquinas.’ ” In Approaches to Nature in the Middle Ages, edited by L. D. Roberts, 161–69. Binghamton, N.Y.: Center for Medieval and Early Renaissance Studies, 1982. “Aristotelian Influences on Galileo’s Thought.” In vol. 1 of Aristotelismo Vene-

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to e Scienza Moderna, edited by Luigi Olivieri, 349–78. Padua: Editrice Antenore, 1983. “Influssi aristotelici sul pensiero di Galileo.” In vol. 1 of Aristotelismo Veneto e Scienza Moderna, edited by Luigi Olivieri, 379–403. Padua: Editrice Antenore, 1983. “The Problem of Causality in Galileo’s Science.” Review of Metaphysics 36, no. 3 (1983): 607–32. “Galileo’s Early Arguments for Geocentrism and His Later Rejection of Them.” In Novita Celesti e Crisi del Sapere, edited by Paolo Galluzzi, 31–40. Florence: Istituto e Museo di Storia della Scienza, 1983. “Galileo and Aristotle in the Dialogo.” Angelicum 60, no. 3 (1983): 311–32. “Galilée et les professeurs jésuites du College romain à la fin du xvi siècle.” In Galileo Galilei: 350 ans d’histoire 1633–1983, edited by P. Poupard, 75–97. Tournai: Desclée International, 1983. “Galileo’s Science and the Trial of 1633.” Wilson Quarterly 7, no. 3 (1983): 154–64. “Aquinas, Galileo and Aristotle.” Proceedings of the American Catholic Philosophical Association 57 (1983): 17–24. Galileo and His Sources: The Heritage of the Collegio Romano in Galileo’s Science. Princeton: Princeton University Press, 1984. “The Intelligibility of Nature: A Neo-Aristotelian View.” Review of Metaphysics 38, no. 1 (1984): 33–56. “Galileo and the Continuity Thesis.” Philosophy of Science 51, no. 3 (1984): 504–10. “The Philosophical Formation of Dominicans.” Angelicum 61, no. 1 (1984): 96–122. “Galileo e i Professori del Collegio Romano alla fine del secolo XVI.” In Galileo Galilei: 350 ans d’histoire 1633–1983, edited by P. Poupard, 76–97. Tournai: Desclée International, 1984. “Galileo’s Concept of Science: Recent Manuscript Evidence.” In The Galileo Affair: A Meeting of Faith and Science, edited by G. V. Coyne, M. Heller and J. Zycinski, 15–35. Vatican City: Vatican Observatory, 1985. “Nature as Animating: The Soul in the Human Sciences.” The Thomist 49, no. 4 (1985): 612–48. De miscibilibus in mixto (critical edition of Latin text). In Dietrich von Freiberg Opera Omnia, Tomus 4: Schriften zur Naturwissenschaft, edited by Maria Rita Pagnoni-Sturlese, 27–47. Hamburg: Felix Meiner Verlag, 1985. “Eloge: James Athanasius Weisheipl, O.P. 3 July 1923–30 December 1984.” Isis 76, no. 4 (1985): 566–67.

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Index Index

Index

accelerated motion, 21, 150, 154, 160 action at a distance, 157 action-reaction principle, 182–86 actuality, 38 Albert of Saxony, 101, 136 Albertus Magnus, 59–62, 78, 89, 97, 101, 106, 117, 131–33, 136, 143 Alexander of Aphrodisias, 105, 197–200, 201 Ambrose of Milan, 106 analogy. See causal proportionality; modeling Aquinas. See Thomas Aquinas Archimedes, 106, 108, 110–11, 113, 143 Aristotelianism, 11–36, 58–62, 64, 85–86, 88–90, 121, 122–23, 123–25, 256 Aristotle, 12–14, 16, 29, 31–32, 33–34, 35, 45, 49, 53, 58, 63, 99–100, 103, 105, 107–8, 112–13, 117–18, 120–21, 122, 123–25, 128–29, 138, 140, 143, 164, 177 cosmological argument, 147, 195–205, 207, 221, 222 elements, 21, 26 hylomorphism, 38, 85–86 nature and mathematics, 18, 132, 139, 161, 187–86 artificial intelligence, 29, 39 Aston, Francis, 22, 164 Augustine, 106 Avempace, 106, 116 Averroes, 99, 102, 106, 133, 201–4, 209 Avicenna, 106, 200, 201, 202, 209 Baeumker, Clemens, 58 Barth, Karl, 248 Basil the Great, 106

Bede, 106 Bell, John, 85 Bellarmine, Robert, 65 Benedetti, Giovanni Battista, 109, 143 Bentley, Richard, 157, 166, 184 Bergson, Henri, 255 Berkeley, George, 211 Bessel, Friedrich, 65, 67 bifurcationism, 80–83 Blondel, Maurice, 255 Bohr model of atom, 25, 46 Bohr-Sommerfeld model, 48, 90 Borro, Girolamo, 109, 113 Boscovich, Ruder, 230 Bradwardine, Thomas, 101, 111 Braithwaite, Richard, 216 Brunner, Emil, 249 Buckley, Michael, 205 Bultmann, Rudolph, 248–49 Buonamici, Francesco, 104, 109, 115 Buridan, Jean, 101, 135–36 Burtt, Edwin, 57, 64 Butterfield, Herbert, 96 Cajetan, Thomas, 106, 248–49, 252–54 Calculatores Oxonienses. See Oxford Mertonians Camus, Albert, 216 Capreolus, John, 106 Carnap, Rudolf, 236 Carugo, Adriano, 107 causality, 12, 14, 24, 43–44, 46, 87, 122, 165 celestial motion, 13, 22–23, 113 Clagett, Marshall, 97 Clark, Samuel, 211

275

276 Index Clavius, Christopher, 19, 109, 126–27, 140–41 Cohen, Bernard, 121 Collegio Romano, 15, 19, 45–46, 107, 126–28, 140–42 Commandino, Frederico, 143 Condemnation of 1277, 96–98, 100, 130, 133, 136 Copernicus, Nicholas, 24, 64, 67, 102, 138 Copleston, Frederick, 216 Coreth, Emerich, 250 corporeal objects, 81–82 cosmological argument, 34–35, 147–88, 189–92, 193–212, 213–17, 218–25, 234–35 Cotes, Roger, 158, 166 Cremonini, Cesare, 124 Crombie, Alistair, 66, 107 Dampier, William, 95 delayed hominization, 42, 257–58 Descartes, Rene, 63, 80, 88, 128, 131, 144, 260 Dewart, Leslie, 251 DNA molecule, 25, 29, 46, 48 Doctores Parisienses. See Paris Terminists Domingo de Soto, 106, 112, 124, 126, 137, 153–54 dualism. See bifurcationism Duhem, Pierre, 95–119 Duns Scotus, 106, 133, 137, 216, 252 Durbin, Paul, 239 Eddington, Arthur, 68, 72, 174–75 Edwards, Paul, 216 Einstein, Albert, 66–67, 68–69, 71, 72, 78, 168, 214, 231 elementary particles, 82–83, 87, 232 elements, 13, 21–23, 122 energy, 227, 231–32, 238–39 essence, 86 Euclid, 109 evolution, 16 experiment, 17–18, 21–22, 91, 122, 124, 127

Fabro, Cornelio, 255 Faraday, Michael, 228, 230 Favaro, Antonio, 104–5 Ferrariensis (Francesco Silvestri), 106 field force, 231, 238–39 final cause. See teleology; teleonomy Fine, Arthur, 90 Flew, Antony, 213, 215 force, 150, 152–55, 157, 160, 169, 171–72, 174, 177, 180–81, 194–95, 227, 229–30, 237–38 form 37–53, 85–86, 228. See also substantial form; natural kinds Foucault, Léon, 65, 67 Francisco de Vitoria, 253 Gaetano da Thiene, 102 Galen of Pergamon, 105, 197–202 Galileo Galilei, 14–15, 18–20, 21–22, 27, 42–43, 45–46, 63–65, 68, 78, 95–119, 120–29, 131, 140, 142–44, 173, 229, 237, 254 Copernician controversy, 13–14, 24 modeling, 24–25, 35–35 Garrigou-Lagrange, Reginald, 255 Geach, Peter, 214 Geiger, Louis, 255 genetics, 25 geocentricism, 13–14 Giles of Rome, 97, 100, 106, 117 Gilson, Etienne, 129, 191–92, 255 God, 34–35, 147, 166–69, 180–82, 184–85, 186, 188, 189–92, 193, 205, 210–11, 213–17, 218–25, 229, 230, 239–40, 257–58 God-talk, 35, 247–52, 258–59 gravity, 21–22, 108, 110–16, 122–23, 177– 78, 209, 210, 227, 229, 237, 238 inverse-square law, 150, 151–69 Gregory of Nyssa, 106 Gregory of Rimini, 138 Grosseteste. See Robert Grosseteste Guidobaldo del Monte, 143 Hamilton, William, 167 Hanson, Norwood Russell, 232

Index  Harré, Rom, 44, 45, 238 Hegel, Georg, 260 Heidegger, Martin, 250, 258, 260 Heisenberg, Werner, 74, 76, 77–78, 83–85, 88, 91 heliocentricism, 14, 102, 121 Hempel, Carl, 227 Herschel, John, 131 Heytesbury, William, 101 Hipparchus, 106, 116 Hoenen, Peter, 79 Hosley, Samuel, 166 human nature, 28–32 Hume, David, 43, 128, 210, 213, 216, 224–25 Husserl, Edmund, 260 hylomorphism, 85–86, 88, 90 hypothetico-deductive method, 45 Ignatius Loyola, 126, 140 immateriality, 90, 226–40 impetus, 96–97, 101, 108, 114–15, 123 inertia, 113–14, 123, 150, 169–82, 214, 222, 229, 238 infinite regress, 221–22 indeterminism, 82–83, 87 intermediate sciences, 18–20, 89, 122, 125, 126–28, 131–32 inverse-square law of gravity. See gravity ipsum esse subsistem, 191–92, 214 Jammer, Max, 194–95 Javelli, Chrysostom, 106 Jerome, 106 Jesuit Roman College. See Collegio Romano John Chrysostom, 106 John Damascene, 106 John of Paris, 62 John Philoponus, 105 Juan de Celaya, 137 Kant, Immanuel, 43, 80, 88, 100, 128, 211, 213, 216–17, 224–25, 250, 255, 260 Kenny, Anthony, 193, 196, 213–17, 222–23

277

Kepler, Johannus, 23, 65, 144, 229 Kierkegaard, Soren, 217 King-Farlow, John, 218–25 Koyré, Alexandre, 63, 95 Kuhn, Thomas, 11, 129 Latin Averroists, 133. See also Paduan Averroists Lauden, Larry, 11 Leibniz, Gottfried, 211, 260 Leo XIII, Pope, 245 Leonardo da Vinci, 96 levity, 21–23, 110, 122 life-powers model, 39–43 Lindberg, David, 131 Locke, John, 80 logical empiricism, 43, 45, 75 logical positivism. See positivism Lonergan, Bernard, 250 Luther, Martin, 253 Mach, Ernst, 71, 238, 246 Madden, Edward, 44, 238 Maier, Anneliese, 97 Mair, Jean, 137 Marechal, Joseph, 250 Maritain, Jacques, 129, 255 Marrone, Steven, 131 Marsilinus of Inghen, 137 Masi, Roberto, 214 mass, 150, 160, 227, 231–32, 238 mathematical physics, 152–61, 166–67, 168–69, 169–82, 186–88 mathematicism, 186–88 Matson, Wallace, 193 materia signata quantitatae, 85–87, 89 matter, 85–87, 227–32 Mayr, Ernst, 44 McIntyre, Alasdair, 213, 215 measurement, 18, 20–23, 81, 83–85, 127 medieval science, 78, 95–102, 131–38 Menu, Antonius, 141–42 metaphysics, 189–92, 214, 218 minima naturalia, 209 modeling, 14–15, 23–36, 37–53 Moody, Ernest, 97, 115

278 Index motion, natural and violent, 113–14, 122–23, 162–69, 176–82, 229 motor causality principle, 150, 180–82, 194–212, 234–35 Murdoch, John, 117 Natalis, Hérvaeus, 106 natural form, See substantial form natural kinds, 16–17, 38, 43–44 natural law ethics, 30–32 nature, 11–36, 37, 85–86, 87, 89–90, 165 Newton, Isaac, 23, 24, 27, 35, 46, 73, 77, 131, 144, 227, 229 cosmological argument, 147–88, 210, 214 Nifo, Agostino, 202, 204–5, 206, 209, 234 Nogar, Raymond, 223 nominalism, 100–1, 118 Nunez, Pedro, 126 O’Brien, Thomas, 189–92 Ockham. See William of Ockham ontological argument, 194, 213, 216–17 Oresme, Nicole, 101, 136 Osiander, Andreas, 64 Owens, Joseph, 189–92, 214 Oxford Mertonians, 97, 101–2, 109 Paduan Averroists, 15, 18–19, 45, 64, 97, 117, 124, 252–53 Paris Terminists, 97, 101, 124 Paul of Venice, 102 Peripateticism. See Aristotelianism Peter of Alvernia, 62 Philoponus. See John Philoponus philosophia perennis, 245 physical objects, 81–83 Piccolomini, Alessandro, 125, 139, 143 Pico della Mirandola, 253 Plato, 30, 96 Platonism, 18, 58–60, 64, 121, 214, 256 political nature, 32–34 positivism, 43, 78, 88, 118, 138–39, 187 potentiality, 38, 84–85, 88, 91 powers model, 39–43 pragmatism, 129 prima via. See cosmological argument

prime matter. See protomatter protomatter, 24, 38, 43, 46–47, 49, 52 Ptolemy, 60, 105, 132 Pythagoreanism, 18, 64, 138 quantum physics, 79–91 Quine, Willard Van Orman, 43–44 Rahner, Karl, 250, 258 Randall, John Herman, Jr., 97, 117 realism, 16–17, 45, 82–83, 88–91, 99–100, 101–02, 118, 128 receptor-activator model, 39–41 regula philosophandi, 24 Reichenbach, Bruce, 213, 215–17 Reichenbach, Hans, 236 Renaissance scholasticism. See second scholasticism Ricci, Ostilio, 108 Robert Grosseteste, 58–59, 78, 97, 99, 101, 106, 117, 131–32 Rorty, Richard, 129 Rugerio, Ludovico, 141–42 Russell, Bertrand, 167, 216 Sacrobosco, 109, 140 Salamucha, Jan, 214 Salmon, Wesley, 43–44 Santillana, Giorgio, 65 Sarpi, Paolo, 63 Sarton, George, 95, 120, 129 saving the appearances. See positivism Schillebeechx, Edward, 250–51, 257 Schrödinger, Erwin, 91 scientiae mediae. See intermediate sciences scientific revolution, 13, 95–96, 128, 142–43 second scholasticism, 138–44, 252–55, 260 Sellers, Wilfred, 235 sensible qualities, 80–81 separatio, 190 Sertillanges, Antonin, 249 Shapiro, Barbara, 130–31, 144 Shea, William, 102 Simplicius, 99, 105, 200–01

Index 

279

Smart, John Jamieson, 235 Smith, Gerard, 191 Smith, Vincent, 79 Smith, Wolfgang, 79–91 Soccorsi, Philip, 79 Soncinas, Paul (Paulus Barbus), 106 soul, 38–43, 205, 234, 236 state vector collapse, 80, 83, 89, 91 Stock, Brian, 99 Suarez, Francisco, 214, 254 subcorporeal objects, 81 substantial form, 37, 43, 47, 49, 52–53, 86–87. See also form; natural kinds suppositional reasoning, 100, 122, 127, 132–33, 136, 143–44 Swineshead, Richard, 101, 135

cosmological argument, 35, 147, 161, 177, 187–88, 190, 191–92, 193–94, 201, 202–4, 212, 213–17, 218, 221–23, 225, 234–35 virtues, 31, 32 Thomism, 15, 19, 25, 69–74, 85–86, 106, 116, 118–19, 126, 139–40, 218–25, 233–34, 243–61 Thomas of Cantimpre, 62 Tillich, Paul, 249 Toledo, Francesco, 112, 126, 254 transcorporeal objects, 81 transubstantiation, 256–57

Taisnier, Jean, 111 Tartaglia, Niccolò, 108 teleology, 215, 227, 236 teleonomy, 236 Tempier, Etienne, 117, 133 Themistius, 105, 200 Theodoric of Freiberg, 62, 99 Thomas Aquinas, 19, 53, 57–62, 65, 67, 68–69, 72, 73, 74, 75–78, 79, 85–86, 89, 97, 100, 101, 106, 117, 120–29, 131–33, 136, 137–38, 143, 243, 255–56, 258, 261

Valla, Paolo, 110–16, 142 verification, 129 Vienna Circle, 236 Vincent of Beauvais, 62 virtue, 30–32 Vitelleschi, Muzio, 110–16 Viviani, Vincenzio, 105

uncertainity principle. See indeterminism uniformiter difformis, 96–97, 101, 112

Wiener, Norbert, 39 William of Auvergne, 131 William of Ockham, 100–1, 106, 133–38 Wolff, Christian, 260

Intelligibility of Nature: A William A. Wallace Reader was designed in Frutiger Serif and composed by Kachergis Book Design of Pittsboro, North Carolina. It was printed on 55-pound Natural Offset and bound by Maple Press of York, Pennsylvania.