Reductionism in the Philosophy of Science 9783110323320, 9783110322873

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Christian Sachse Reductionism in the Philosophy of Science

EPISTEMISCHE STUDIEN Schriften zur Erkenntnis- und Wissenschaftstheorie Herausgegeben von / Edited by Michael Esfeld • Stephan Hartmann • Albert Newen Band 11 / Volume 11

Christian Sachse

Reductionism in the Philosophy of Science

ontos verlag Frankfurt I Paris I Ebikon I Lancaster I New Brunswick

Table of contents Acknowledgements 0. i. ii. iii.

Overview of the general part of the thesis The approach The framework The motivation

7 10 12

I.

Ontological reductionism Preliminary remark and abstract

15

Framework Truth-maker realism The layered view of the world Compatibility of the framework

16 18 21

i. ii. iii.

Premises iv. Completeness of physics (premise one) v. Incompleteness of the special sciences vi. Redundancy of epiphenomena vii. Supervenience (premise two) viii. Status of supervenience Ontology of property tokens ix. Property discrimination by causal difference x. Identity by causal indifference xi. Causal efficacy of property tokens of the special sciences xii. Change dependency of property tokens of the special sciences xiii. Change determination by physics Argument for ontological reductionism xiv. Token-identity qua causal efficacy and completeness xv. Status of the token-identity argument xvi. Objection to the causal drainage argument Résumé and transition

24 29 31 33 36

41 45 48 49 50

51 56 58 61

Table of contents

II.

i. ii. iii. iv.

Epistemological reductionism Preliminary remark and abstract

63

Framework Concept of theories Concept of property types Concept of concepts Concept of explanation

64 65 68 71

Motivation and conditions for epistemological reductionism v. Supervenience of truth-values vi. Universality of physical concepts vii. Motivation for epistemological reductionism viii. Necessity of co-extensionality for epistemological reductionism

79 82 83 85

ix. x. xi. xii.

Models for epistemological reductionism Nigel’s model of reduction Kim’s model of reduction Functionally defined concepts Universality of functionally defined concepts

89 99 109 113

xiii. xiv. xv. xvi. xvii.

An argument against epistemological reductionism Argument of multiple realization Consequences for Nagel’s model Consequences for Kim’s model Implication of multiple realization Critique of the multiple realization argument

117 120 123 131 133

New strategy for epistemological reductionism xviii. Detectability of physical differences xix. Implication of detectability xx. Relationship between concept and sub-concepts xxi. Epistemological reductionism by means of sub-concepts

138 148 152 157

Résumé and transition

166

Table of contents

III.

i. ii. iii.

iv. v. vi.

Complete conservative reductionism Preliminary remark and abstract

167

Implication from ontological reductionism to epistemological reductionism Starting point ontological reductionism Implication of anti-reductionism Conclusion

168 169 172

Implication from epistemological reductionism to ontological reductionism Starting point epistemological reductionism Incompatibility of epistemological reductionism with property dualism Conclusion

Complete conservative reductionism vii. What complete reductionism means viii. What conservative reductionism means ix. The limits of the sub-concept strategy Résumé and transition to the biological part IV. i. ii. iii. V.

i. ii. iii. iv. v.

173 174 176

177 178 181 182

Overview of the biological part Historical framework Systematic framework The approach

183 192 199

Classical genetics Preliminary remark and abstract

207

Introduction to classical genetics The concept of supervenience applied to classical genetics The importance of the gene concept Functional characterization of the gene The explanatory limits of classical genetics

208 211 215 220 228

Table of contents

VI.

i. ii. iii. iv. v.

VII.

i. ii. iii. iv. v.

Molecular genetics Preliminary remark and abstract Introduction to molecular genetics Causal disposition of the DNA Relative completeness of molecular genetics Argument for the token-identity of genes and DNA Motivation for the reductionist approach to classical genetics

231 232 238 242 247 253

Reduction of classical genetics to molecular genetics Preliminary remark and abstract

257

Introduction to the relationship The multiple realization argument applied to genetics Construction of sub-concepts Reduction of classical genetics to molecular genetics Final remarks

258 262 269 289 297

References

307

Index

325

Acknowledgements Sometimes, there are single moments that turn out to be, in retrospective, the most important ones for the topic of a PhD thesis. For me, that moment is forever identified with the discussion of Jaegwon Kim’s “Mind in a physical world” in Michael Esfeld’s seminar in Cologne in 2001. Since then, I have never stopped thinking about the issues raised by Kim and Esfeld. In this context, no work is the product of a single person – at least, not in philosophy nowadays. I owe enormous philosophical debts to many people in addition to Michael Esfeld, who supported me and the progress of my PhD thesis. These include, especially, Jan Aengenvoort, Christian Bach, Christian Doppelgatz, Pacal Engel, Jens Harbecke, Vera Hoffman, Jaegwon Kim, Vincent Lam, Martine Nida-Rümelin, Michael Sollberger, Georg Sparber, David Stauffer, Bruno Strasser, Marcel Weber, Alain Zysset, and the participants of my courses at the University of Lausanne. I am also grateful to the Swiss National Science Foundation (SNF) for its financial support for my PhD thesis, including my visit to Jaegwon Kim at Brown University in spring 2006, and my participation of several congresses and workshops (grant no. 100011-105218/1). I would also like to thank Rafael Hüntelman and the Ontos Verlag for the publication of this work, and Roger Gathman for proofreading. Apart from this academic and financial support, no words could express my debt to my family and my friends in Cologne and Lausanne, especially Bianca, Ingrid, Gerhard, Maren, Alexander, Andrea, Yvonne, Martin and Marie.

University of Lausanne, February 2007 Christian Sachse

7

0.

Overview of the general part

i.

The approach

The main aim of the general part of this work is to make a case for the reductionist approach to the special sciences. I will be arguing for both ontological reductionism and epistemological reductionism, and furthermore, that they imply each other. But my argument supports conservative reductionism: the properties of the special sciences exist, and the theories of the special sciences are true and indispensable from a scientific point of view. Moreover, the argument for ontological reductionism will not seek to eliminate the property tokens of the special sciences, while epistemological reductionism, similarly, is constructed so as not to eliminate the theories of the special sciences. These property tokens and these theories will, instead, be integrated into the physical domain. Corresponding to these central issues, there are three chapters in which I shall consider ontological reductionism, epistemological reductionism, and complete conservative reductionism. I begin, in chapter one, with an argument for ontological reductionism. If we assume that there are property tokens of the special sciences out there in the world, then this raises questions about their relationship to physical property tokens. What is, for instance, the relationship between the biological properties of a certain flower and its physical properties? Is there any ontological difference between, on the one hand, physical property tokens, and, on the other hand, property tokens of the special sciences? In order to consider this issue, I shall argue for two premises: physics is causally complete, and the property tokens of the special sciences supervene on configurations of physical property tokens. This suggests that every causally efficacious property token of the special sciences is identical with a configuration of physical property tokens. As a case in point, once again, the biological property tokens of a flower are identical with certain configurations of physical property tokens. This is token-identity, which amounts to ontological reductionism. Chapter two is about epistemological reductionism. This is the reduction of concepts of the special sciences to their proper physical concepts in order to establish a systematic relationship between the special sciences and physics. My argument for epistemological reductionism will proceed as follows: assuming ontological reductionism, the special sciences are about the same entities (property tokens) that physics is about.

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Reductionism in the philosophy of science

Thus, there are different descriptions and explanations of the same entities. For instance, biology is about the biological property tokens of a flower of a certain type, and these biological property tokens are identical with certain configurations of physical property tokens. Hence, physicists may describe each of the flowers and the biological property tokens in question as, say, some complex molecular configuration. There are, thus, biological and physical concepts of the same entities. This fact invites questions about the relationship of the different concepts: is there any difference between physical concepts and concepts of the special sciences when they refer to the same entities? What is the epistemological difference between different scientific points of view? In fact, there are epistemological differences, and there is the well-known claim of the autonomy of the special sciences from physics. The justification for holding to this special epistemological domain is mainly based on the famous multiple realization argument. However, as I shall show, the main difference between the special sciences and physics is more or less a difference of the degree of abstraction. The autonomy of the special sciences from physics means its independence from physical details. Property types are concepts, and hence, multiply realized property types are concepts that abstract from details. The aim of chapter two is to provide a strategy to reduce nonetheless the concepts of the special sciences to the concepts of physics proper. In order to consider the argument from multiple realizability, I shall generally take biology as an exemplary case of a special science. However, the strategy is a general one. As I shall argue, the special sciences can consider more detailed functionally defined concepts. These concepts are co-extensional with physical concepts, and based on this coextensionality, it is possible to reduce the special sciences to physics. This is epistemological reductionism by means of more detailed functionally defined concepts, which I shall call sub-concepts. Chapter three is about the relationship between ontological and epistemological reductionism. It contains an argument against elimination. Provided that my argument for ontological and epistemological reductionism is cogent, one may raise questions about the relationship between ontological reductionism and epistemological reductionism. I shall argue that they imply each other. My argument proceeds as follows: on the one hand, epistemological reductionism implies that there is coextensionality between different concepts. However, functionally defined concepts are about the causal efficacy of property tokens. Property tokens are ontologically identical when they cannot be distinguished causally. Thus, functionally defined concepts that are co-extensional with physical

O. Overview of the general part

9

concepts have to be about the same causally efficacious property tokens as those physical concepts. This is the implication from epistemological reductionism to ontological reductionism. On the other hand, ontological reductionism implies epistemological reductionism as well. Given that there is ontological reductionism, the concepts of the special sciences are about the same entities as those ones that are described and completely explained by physical concepts. Given, too, the multiple realization argument, there must be concepts of the special sciences that are not coextensional with physical concepts. However, as I shall point out, the multiple realization argument as an anti-reductionist argument suggests the elimination of the special sciences – contrary to the intention of its authors. As I shall demonstrate, the scientific value of the special sciences can only be vindicated within a reductionist approach – an approach that is outlined in chapter two. This means, the deriving epistemological reductionism from ontological reductionism operates as the only valid argument against the elimination of the special sciences. Furthermore, ontological reductionism operates, similarly, as the only argument against the elimination of property tokens of the special sciences. Thus, ontological and epistemological reductionism are so related that one positions may not be endorsed without the other one. To put it another way, I shall take the multiple realization argument as an argument for the indispensable scientific character of the special sciences and embed this argument in a reductionist approach in order to vindicate the scientific value of the special sciences. In sum, one can conclude that there is a good argument for ontological reductionism (chapter one). Based on this, there is a good argument for epistemological reductionism (chapter two). Against this background, it follows (chapter three) that a complete but conservative reductionism is the only coherent position that respects both the causal completeness of physics and the indispensable scientific character of the special sciences. Having outlined my approach, there remain two issues to explain before moving on to chapter one. The first concerns my assumptions and framework, while the second is about the fundamental motivation of my work.

10

ii.

Reductionism in the philosophy of science

The framework

Both everyday experience and the sciences suggest that there are various entities out there in the world. There are, for instance, atoms, molecules, enzymes, cells, plants, animals, etc. Some may have a charge and a mass, while others may also have a metabolism or yellow blossoms. To put it in other terms, there are theories that attribute specific property tokens to certain entities. All there is in the world are entities. An entity that physicists describe as a possessor of certain physical property tokens may be called a ‘physical system’ as, for instance, a molecular configuration with certain physical property tokens such as mass and charge, while any entity that biologists describe as a possessor of certain biological property tokens may be called a ‘biological system’ as, for instance, a tree or a flowering plant with a metabolism and blossoms. In this sense, the difference between ‘system’ and ‘entity’ is the following: the term “system” refers to an entity in the world as described by a certain theory, whereas the term “entity” leaves open what is the appropriate description. The term “entity” is ontologically neutral, while “system” refers to a physical or biological system (possessor of physical or biological property tokens). With this distinction in mind, we can say that there are entities in the world that are, from a biological point of view, biological systems because of their biological property tokens. However, these biological systems, like a flower for instance, necessarily possess not only specific biological property tokens, but also physical property tokens. Therefore, biological systems are physical systems as well. Since a physicist can attribute to a flower physical property tokens, the flower is, from a physical point of view, a physical system. To put it in other terms, there is a flower possessing some biological property tokens and physical property tokens at the same time. This invites questions about the relationship of these property tokens. Before moving on, let us note the distinction between property tokens and types that will be reconsidered in detail in the first and second chapter (cf. especially ‘truth-maker realism’, chapter I, p. 16, and ‘concept of property types’, chapter II, p. 65). Property tokens are ontological, while property types are not. Property tokens exist in the world, while property types are concepts that describe property tokens. Nonetheless, property tokens can make up a natural kind because of salient similarities among them. These similarities are brought out by concepts. For instance, a gene type is a concept that brings out salient causal or dispositional similarities among certain gene tokens.

O. Overview of the general part

11

To put it another way, there are property tokens and concepts to describe them. Chapter one is about ontological reductionism. This position says that there is no ontological difference between a causally efficient property token of the special sciences and an appropriate configuration of physical property tokens. Gene tokens are identical with something physical. The underlying argument for this ontological reductionism is a causal one. For this reason, chapter one is mostly concerned with property tokens. Causation is a relation between property tokens. Against this background, chapter two is about epistemological reductionism which is about theories since they are our epistemic account of the world. Thus, chapter two is, above all, couched in terms of concepts about property tokens. For these chapters, as I have already mentioned, I shall make the assumption, which is by and large uncontroversial, that what really exists in the world are property tokens, while theories are our epistemological account of these property tokens by means of specific concepts. Therefore, the definite mass of an atom is a physical property token that comes under the physical concept “mass”, and likewise the definite phenotype of a flower at a specific time is a biological property token that comes under the biological concept “phenotype”. There are configurations of property tokens and concepts about them. There are property tokens that come under physical, or biological concepts. For instance, there are property tokens that come under the concepts “mass”, “charge”, “three-dimensional configuration”, “capacity for self-organization”, “capacity for reproduction”, “gene”, “phenotype”, “fitness”, etc. In more general terms, there are property tokens in the world that come under the same or under different concepts. There are both oak trees and flowers, just as there are single electrons and complex molecular configurations in the world. To put it simply, a molecular configuration is a physical system to which physicists attribute physical property tokens, and a flower is a biological system to which biologists attribute biological property tokens. However, one should bear in mind that a complex configuration of physical property tokens is itself, by conjunction, a physical property token. Thus, I shall call them ‘physical property tokens’ or ‘molecular configuration’ rather than ‘complex configurations of physical property tokens’ in order not to complicate the issue unnecessarily. I shall do the same for concepts. The physical concept about a certain molecular configuration is a complex conjunction of concepts about atoms, electrons, mass, etc. So in what follows, ‘molecular

12

Reductionism in the philosophy of science

configuration’ will often stand for the appropriate configuration of physical property tokens or its proper physical description. There is physics and there are the special sciences. On the one hand, there is physics with its concepts about specific systems and their property tokens. On the other hand, there are the special sciences like chemistry or biology with their concepts about specific systems and their property tokens. In order to examine the arguments for and against reductionism, it is not really feasible to take into account all the special science theories. But we can simplify by giving general arguments for and against a reductionist account that will make it unnecessary to compare all special sciences to physics. I shall provide a general argument and strategy for a reductionist approach, even though I am only going to consider biology and physics. In the context of the most compelling anti-reductionist argument, the multiple realization argument, I shall take biology as representative of the special sciences. I shall compare the concepts about systems and property tokens of the special sciences to physical concepts about these systems and property tokens by comparing biology to physics.

iii.

The motivation

Biological systems possess biological and physical property tokens. Our experience suggests that we can attribute to biological systems not only biological property tokens such as a certain phenotype, or a certain fitness, but physical property tokens as well. For a case in point, take some beautiful flower with yellow blossoms. We can assume that it also possesses physical property tokens in a manner I cannot spell out here. Let us say that, from a physical point of view, the flower is a molecular configuration. Given this characterization, one may ask questions about the relationship between these prima facie different property tokens. To put it in other terms, what is the relationship between the molecular configuration and the biological property tokens that the flower possesses at a specific time? Does the molecular configuration of a biological system determine its biological property tokens? Does the molecular configuration of the flower determine the occurrence of yellow blossoms? Does a change of a biological property token depend on an appropriate physical change? Is it possible for the yellow blossoms of the flower to drop without any appropriate physical change, such as a structural change of the molecular configuration? In fact, experience suggests that there is a relationship of determination and dependency. The physical property tokens of a

O. Overview of the general part

13

biological system determine its biological property tokens, and there is no biological change without an appropriate physical change. A physical duplicate of a flower is a biological duplicate of the flower as well, and the drop of the blossoms of a flower implies a change of its molecular configuration. This fact motivates the more detailed consideration of the relationship between prima facie different property tokens in chapter one. After all, physical and biological property tokens seem to be different property tokens. However, there is a causal argument for an identity of these prima facie different property tokens. The biological property tokens of the flower are identical with the physical property tokens of the molecular configuration (of the flower). To put it in general terms, any biological property token is identical with a configuration of physical property tokens. This is ontological reductionism. There is no ontological difference between a biological property token and its respective configuration of physical property tokens. As a consequence of the ontological reductionism considered in chapter one, there are property tokens that can be described by different theories. A biological property token, for instance, is an entity that comes under a physical concept as well. If a certain biological property token of some beautiful flower is identical with a molecular configuration, there are biological and physical concepts about the same entity. This fact leads to the following epistemological question: what is the relationship between different theories when they refer to the same entities (property tokens)? For example, what is the relationship between biology and physics when they describe one and the same property tokens (of some flower)? Theories are concerned with concepts that describe property tokens in the world. So, are there any dependencies or determinations between concepts of the different theories? What distinguishes physics from some theory of the special sciences like biology? What is meant by the famous autonomy claim of the special sciences? These questions motivate chapter two. Its aim is to argue for a reductionist approach, which claims that the concepts of the special sciences are, in principle, reducible to physics. The question of the relationship between ontological and epistemological reductionism locally arises against the background of the issues discussed in that chapter. Most philosophers agree with the argument for ontological reductionism as outlined in chapter one. The yellow blossoms are identical with a molecular configuration. However, many philosophers deny the possibility of epistemological reductionism. In chapter two, I shall demonstrate that this denial is unjustified. A reductionist approach to the special sciences will be provided. This raises

14

Reductionism in the philosophy of science

the question of whether ontological reductionism is independent of epistemological reductionism, and vice versa. In chapter three I shall argue that the one reductionist position implies the other one. Epistemological reductionism implies ontological reductionism. The concepts would be irreducible one to the other only if the concepts were about different ontological property tokens. And, since token-identity implies in principle co-extensionality, ontological reductionism implies epistemological reductionism as well. Thus, one can be either a complete reductionist or one has to reject any kind of reductionism.

15

I.

Ontological reductionism Preliminary remark In order to oppose a reductionist approach to property tokens of the special sciences, one would have to show how they could be causes in a physical world that is causally complete.

Abstract This chapter is about the causal argument for ontological reductionism. After providing an introductory framework, I shall consider the two central premises of the argument. These are, firstly, the completeness of physics, and secondly, the supervenience of property tokens of the special sciences on configurations of physical property tokens. For each of these premises I shall argue independently. Next, the implications of these premises for the ontology of property tokens will be considered. Lastly, foregrounded by the development of these themes, we will examine the argument for ontological reductionism and possible objections to it.

16

Reductionism in the philosophy of science

Framework i.

Truth-maker realism

There are property tokens in the world. If an application of a concept about something in the world is true, there is something in the world that makes it true.1 This suggests that there are physical property tokens as truth-makers for physical concepts, and property tokens of the special sciences as truth-makers for the concepts of the special sciences. These property tokens are in the world. Let us briefly consider this truth-maker realism about physical and biological property tokens as a framework for this and the subsequent chapters. First of all, I shall begin with truth-maker realism about a physical property token p. Let us suppose that some application of a physical concept “P” is true about an entity e in the world. Provided that the application is true, there is an entity e in the world that makes this application true. This is reason enough to justify realism about this entity e. This in turn entails realism about the appropriate physical property token p, as described by the concept “P”. There is the entity e that makes the application of “P” true, and this very entity e really is the physical property token p. A case in point is the following: if the application of the physical concepts “There are atoms of type P1 binding to atoms of type P2 that are …” is true about an entity e in the world, then this entity makes this application of concepts true. Moreover, this entity e then really is a token of a certain molecular configuration: 1. e (entity)

2.

e is p (physical property token)

↓ (makes true) “P” (physical concept) Secondly, let us consider truth-maker realism about some biological property token b. Assume that some application of a biological concept “B” is true about an entity e in the world. 1

Cf. Heil (2003, chapter 7, especially p. 61) who considers the truth-maker relation in detail.

I. Ontological reductionism

17

Provided that the application is true, there is an entity e in the world that makes this application true, which by itself justifies realism about this entity e. This entails realism about the appropriate biological property token b as described by the concept “B”. There is the entity e that makes the application of “B” true, and this very entity e really is the biological property token b. Take our example of a flower with some biological property token: if the application of the biological concept “This is a flower with yellow blossoms” is true about an entity e in the world, then this entity makes this application of the biological concept true. Moreover, this entity e really is a flower with yellow blossoms: “B” (biological concept) ↑ (makes true) 1. e (entity)

2.

e is b (biological property token)

Finally, let us consider the truth-maker realism in general terms. Realism about entities does not necessarily imply that a property corresponds to each concept.2 If we are realists about a physical property token p, then this does not mean that we subscribe to the claim that e really is exclusively as it is described by the physical concept “P”. If an entity e makes the application of “P” true, say “molecular configuration”, this does not necessarily imply that e is exclusively as physicists describe it in terms of molecular configurations. The argument is that there are entities in the world that make applications of different concepts true. There are entities that make physical and biological descriptions true. For instance, an entity e may make true both the physical description “There are atoms of type P1 binding to atoms of type P2 that are …”, and the biological description “This is a flower with yellow blossoms”:

2

Cf. Heil on the correspondence principle of the picture theory (2003, ch. 3).

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Reductionism in the philosophy of science

“B” (biological concept) ↑ (makes true) e is b (biological property token) 1. e (entity)

2. e is p (physical property token)

↓ (makes true) “P” (physical concept) Let us sum up and call this ‘truth-maker realism’. If a concept about a certain property token is made true by an entity in the world, the property token (the concept is about) is real. In this context, physical property tokens and property tokens of the special sciences are real provided that the concepts in question are made true. These entities are taken to be the appropriate property tokens that really exist. I shall follow John Heil and take property tokens as modes – as particularized, individualized ways systems are.3 Property tokens do not instantiate property types but make them true. To put it another way, property tokens are ontological and basic while property types are concepts that describe the modes, the property tokens. In this context, one and the same mode (property token) can make true different concepts. For instance, since a certain gene token can make true the biological concept “gene” as well as a physical description of that gene token, we can say that these property tokens (modes, truthmakers) are not exclusively as scientists describe them under one theory. One and the same property token can be described by means of different concepts.

ii.

The layered view of the world

There are levels of complexity, and there are different levels of description. To put it simply, there are less complex systems such as electrons and atoms that are described by physics, and there are more complex systems like cells and organisms that are generally described in terms of the special sciences. This means, there are different levels of description. In order to formulate an illustrative 3

Cf. Heil (2003, ch. 13).

I. Ontological reductionism

19

but ontologically neutral framework, let us briefly consider some points about the so-called layered view of the world. First of all, there are different levels of description. This means that there are, for instance, the special sciences and each of their theories describes only specific systems. Physics, however, is universal. In other words, physics generally describes systems such as electrons and atoms that make up the systems that are described by chemistry or biology. I shall reconsider this relation later on in more detail in terms of composition. In any case, chemistry generally describes systems like acids or enzymes, biology generally describes systems such as cells or organisms, etc. In this context it is generally accepted that there are different levels of description. Second, there are different levels of complexity. A system is complex if there are certain specific causal relations among its parts. This means, the way in which the parts of a system interact specifies the complexity of that system. In this context, the systems of the special sciences such as cells, organs, or organisms are complex systems compared to physical systems such as atoms or electrons – that is, systems that are considered only from the point of view of physics. As a case in point, organisms are capable of reproduction and adaptation, while single electrons are not. This criterion of complexity is a relative one. For instance, chemical systems such as enzymes are more complex than physical systems like atoms, but biological systems like organisms are more complex than enzymes. Furthermore, complexity is ontological complexity. If a system is relatively more complex than another system, then there is an ontological difference between these systems. For instance, a flower differs ontologically from a single electron or atom. This ontological difference is based on a causal difference (cf. ‘property difference by causal difference’, this chapter, p. 41). In this context, let us consider the criterion of complexity in terms of composition. Biological systems like organisms are complex systems because they are composed of chemical and physical systems such as enzymes and atoms. This means, biological systems are more complex than chemical and physical ones. Therefore, the description of a biological system such as an organism is very complex in terms of chemistry – and a physical description of that organism is even more complex, because it would take into account all the interactions among the parts. To conclude, biological

20

Reductionism in the philosophy of science

descriptions of complex systems are more abstract than chemical or physical descriptions of the system in question. Third, physics is the most fundamental level of description. Any biological system can be described in chemical and physical terms as well, and any chemical system can also be described by physics. Since biological and chemical systems are composed of physical systems, they can be described in terms of physics. Contrary to this, there are physical systems such as electrons or atoms that constitute complex systems, but these physical systems are not composed of chemical or biological systems. To put it simply, an enzyme is composed of atoms, but atoms themselves are not composed of chemical systems. As a result of this, physical systems cannot generally be described in terms of the special sciences. This is why there is an asymmetric relationship between physics and the special sciences. To put it in general terms, any system in the world can be described by physics, while only certain, generally complex, systems can be described by the special sciences.4 Therefore, we take physics to be the most fundamental level of description. The following scheme outlines this uncontroversial implication of the layered view of the world:

Biology Chemistry Physics

4

Cf. C. L. Morgan (1923) who considers the layered view of the world as a framework for his emergentism. Cf. Oppenheim & Putnam (1958) who consider the layered view of the world as a framework for their aim of a methodological reductionism and the unity of science. Cf. Kim (2002) who concentrates his criticism on the criterion of composition, and considers the problem of any ontological implication of the layered view of the world. Kim (2002) is, hence, a critic of C. L. Morgan (1923) and Oppenheim & Putnam (1958). Compare furthermore Stephan (1999) for a detailed analysis of emergent properties and levels of being.

I. Ontological reductionism

21

Finally, the layered view of the world as outlined here is per se ontologically neutral. The usual criterion of composition of systems for the asymmetric relationship between different theories has no ontological implications. Ontological differences are generally founded in causal differences (cf. ‘property discrimination by causal differences’, this chapter, p. 41). Thus, the fact that a biological system like a flower, for instance, is composed of a complex configuration of physical systems does not imply any ontological difference between the flower and its physical composition per se. Any argument for an ontological difference has to be grounded in the causal differences between an organism as a biological system and its physical composition. Let us recap and term this ‘the layered view of the world’. The fact that there are different theories that usually describe systems of different complexity motivates our ascription of them to different levels of descriptions. Thereby, the criterion of composition establishes an asymmetric relationship between the different theories. However, this criterion has no ontological implications per se. Therefore, I shall take the layered view as meaning that there are different levels of complexity and description.

iii.

Compatibility of the framework

‘Truth-maker realism’ and ‘the layered view of the world’ are ontologically neutral. They are compatible with a wide range of ontological positions. Suppose an entity e makes an application of a concept about this entity true. This suggests that this entity e really exists and is a specific property token (cf. ‘truth-maker realism’, this chapter, p. 16). This excludes neither ontological reductionism, nor property dualism (as the main ontological positions). From this it follows that we can take ‘truth-maker realism’ as an ontologically neutral framework for this work. In addition to this, ‘the layered view of the world’ is ontologically neutral as well because it does neither imply nor exclude levels of ontology (cf. ‘the layered view of the world’, this chapter, p. 18). Let us briefly outline both the ways ontological reductionism and property dualism may be combined with ‘truth-maker realism’ and ‘the layered view of the world’. Firstly, let us consider ontological reductionism. This position claims that any property token of the special sciences is identical

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Reductionism in the philosophy of science

with a configuration of physical property tokens. We should bear in mind that any configuration of physical property tokens is by conjugation itself a physical property token. However, the tokenidentity claimed by this reductionist position is compatible with the truth-maker relation. There are entities in the world that may make different concepts true, as, for instance, in the case of an entity e making true both the physical description “There are atoms of type P1 binding to atoms of type P2 that are …” and the biological description “This is a flower with yellow blossoms”. Thus, the entity e makes a physical and a biological concept true. Suppose a flower with yellow blossoms is identical with a molecular configuration of physical property tokens. This is ontological reduction. However, this claim about the real existence of the flower with the yellow blossoms and the molecular configuration simply means that there is an entity e that makes the application of the corresponding concepts true. Nothing changes if, as in this case, the truth-maker is one and the same entity e (cf. ‘concept of property types’, chapter two, p. 65). In addition to this, ontological reductionism is compatible with ‘the layered view of the world’ as well. Because of the token-identity, there are no ontological differences. Since any biological property token is identical with an appropriate physical property token, there are no levels of being. There are only levels of complexity and descriptions. Against this background, I shall take ontological reductionism as compatible with both ‘truth-maker realism’ and ‘the layered view of the world’. Secondly, we must consider the ontological claims of property dualism, which posits that there are property tokens of the special sciences not identical to configurations of physical property tokens. However, ontological differences are compatible with ‘truth-maker realism’. There are entities in the world that make applications of physical concepts true. And either these or other entities make applications of concepts about ontologically different property tokens true. To illustrate this point, let us again use the example of the flower with yellow blossoms and its molecular configuration. Suppose the flower with its biological property tokens differs ontologically from the molecular configuration with its physical property tokens. This would mean in a causal theory of properties, that the flower possesses a biological causal power that is not a physical causal power. This idea lies at the heart of the argument for

I. Ontological reductionism

23

an ontological difference between the flower and its molecular configuration. Property tokens are ontologically discriminated by different causal powers (cf. ‘property discrimination by causal difference’, this chapter, p. 41). This is property dualism. The flower with its yellow blossoms and its molecular configuration really exists (provided that there is in each case an entity that makes the application of the corresponding concept true) in any case. Nothing changes if, as here, there is the same entity (the flower) as truthmaker for concepts of different property tokens. In addition to this, property dualism is compatible with ‘the layered view of the world’ as well, reading to that view to mean that there are different ontological levels because of causal, and thus ontological, differences. This means that there are different ontological levels. There are not only levels of complexity in physical composition and description, but there are furthermore purely physical and purely biological levels of being. Thus, property dualism is compatible with both ‘truth-maker realism’, and ‘the layered view of the world’. Let us recapitulate what we will term the ‘compatibility of the framework’. The validity of truth-maker realism is unaffected by whether ontological reductionism or property dualism turns out to be true, being neutral with respect to these positions. In addition to this, more or less any ontological position is compatible with ‘the layered view of the world’. It is only the ontological position per se that commits us to a certain interpretation of levels. The argument for ontological reductionism commits us to an interpretation according to which there are no levels of being. There are only levels of complexity and description. In the case of property dualism, the layered view has merely to be interpreted in a different way, such that, there are different levels of being. In any case, a layered view as such does not favour any ontological position. For that reason, I shall take both ‘truth-maker realism’, and ‘the layered view of the world’ as an ontologically neutral framework for the following considerations.

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Premises iv.

Completeness of physics (premise one)

The success of physics motivates the completeness claim that physics should be taken to be complete in every causal, nomological, and explanatory respect. This completeness claim holds for physics relative to the special sciences. At least, physicists take this completeness for granted.5 Let us consider these three types of completeness and their mutual dependencies. First, let us consider the causal completeness of physics. This is the claim that for any physical property token p 2 that can be described by physics, insofar as p2 has a cause, it has a complete physical cause (say p1): p1

p2

(complete cause)

In our claim, ‘complete’ means physicists would never have to go beyond physical causation, with our ‘insofar’ clause inserted just in case physical causation might be probabilistic, or uncaused physical changes might be possible.6 Nonetheless, physicists always search for causes within physics. To put it another way, there are no non-physical causes that could fill in any of the gaps that there may be in physical causation. Suppose that causal relations are probabilistic; physics, e.g. quantum physics, still completely 5

Cf. Papineau (1993, p. 14, 2001, pp. 6-9, and 2002, appendix) where he formulates an argument for the causal completeness of physics. Furthermore, compare Crane and Mellor (1990) who criticize the connected topic of ontological reductionism by means of a critique of the completeness of physics. However, Pettit (1993), Papineau (1993) and Loewer (2001) refute their critique, and I shall reconsider their point later on (cf. ‘status of token-identity argument’, p. 56). See further the second part of this work, where I argue in a concrete case for a completeness claim (cf. ‘relative completeness of molecular genetics’, ch. VI, p. 242). 6 Cf. Hasker (1999, p. 60) who maintains that uncaused events are possible.

I. Ontological reductionism

25

determines the probabilities by which we can quantify the chance that any physical property tokens occurs, since these are fully determined by the prior occurrences of physical property tokens and physical laws. Leaving aside uncaused changes, physics furthermore provides the best explanation of physical causal relations. To illustrate one case in point, physicists, considering the changes of a molecular configuration’s structure or its motion, will always seek a complete cause within physics. There might be, for instance, some causal influence by physical property tokens of another molecular configuration or some waves of light. Whatever the case, physicists would never go beyond a physical explanation. Second, let us consider the nomological completeness of physics. Insofar as there are laws that apply to p2, there are physical laws under which p2 completely comes: p1

p2

(complete cause, and causal law)

In this claim, ‘completely’ means that physicists would never have to go beyond physical laws and the secondary clause starting with ‘insofar’ signifies that the physical laws applying to p2 might be probabilistic, or even that it might turn out that no laws apply to p2. In any case, physicists always search for laws under which p2 comes within physics. If there were no physical laws under which p2 comes, there would be no special sciences laws either. That is what physical experience suggests. To illustrate, let us again consider a molecular configuration with some physical property tokens. Say, there is a molecular configuration p1 that changes into a structurally different molecular configuration p2. In order to explain this change (or the occurrence of p2), physicists search for laws under which this change from p1 to p 2 comes about. To explain what happens when the molecular configuration p1 changes its structure to p2, physicists seek only for a complete cause within physics that comes under a physical law. If there is a complete physical cause for this change, there will be a complete physical law as well. This implication from causal to nomological completeness arises from the following assumption: any relation between two property tokens that suffices to allow us to speak of a causal relation

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Reductionism in the philosophy of science

between them also suffices to allow us to speak of a law-like relation between the property tokens in question. Therefore, any nomological completeness claim is mainly based on the argument for the causal completeness. However, if physical law were not complete, there would not be a law of the special sciences either. This implication is based on the following assumption: there couldn’t be a law of the special sciences that fills any nomological gap of physics since the causal completeness of physics forbids it. For any change of physical property tokens, there is a complete physical cause, and hence, a complete physical law under which this change comes about. Suppose there were some law of the special sciences about a physical change without there being within physics a law under which the physical change in question comes about – this would mean that either physics is causally not complete, or the law of the special sciences is about non-causal property tokens. In order to claim the first possibility, one would have to argue against the causal completeness of physics. In order to maintain the second possibility, one would have to argue for laws of the special sciences that are about causally redundant physical property tokens (epiphenomena). Since the general redundancy of epiphenomena will be considered later (cf. ‘redundancy of epiphenomena’, this chapter, p. 31), we can leave that possibility aside at this point. However, suppose physics turned out to be incomplete in causal respects. Since laws are considered to be causal laws, physics would be incomplete in nomological respects as well, which would mean that there would be physical property tokens with causal powers that do not come under a physical law. For instance, some structural change of a molecular configuration would have nonphysical causes. Since I shall focus on causal issues, let us take ‘law’ as an abbreviation for ‘causal law’. Any law under which an entity comes into being invokes causes of the entity in question. If there is no physical cause of an entity, there is consequently no physical law under which the entity could come. In this sense, nomological completeness depends on causal completeness. If physics were causally incomplete, physics would not completely determine the probabilities of physical causal relations. In such a case, the probabilities of a structural change of a molecular configuration would have to be traced back to non-physical causes. Therefore, this causal change would not come under a physical law, and one would

I. Ontological reductionism

27

have to go beyond physics and might be obliged to have recourse to laws of the special sciences in order to account for physical changes. Finally, let us outline the explanatory completeness of physics in more detail. This means that insofar as there is an explanation of p2, there is a complete explanation of p2 in terms of physics: p1

p2

(complete cause, causal law, and causal explanation)

Again, ‘complete’ means that in order to explain given property token, p2, physicists will never need to go beyond the physical concepts embedded in physical theories. Physicists always search for explanations of p 2 within physics; and if there is no physical explanation of p2, no explanation will be forthcoming in terms of the special sciences either. Let us once again consider a molecular configuration with some physical property tokens. Assume once again that there is a molecular configuration p 2. In order to explain p 2, physicists search for a physical cause, p 1, and the appropriate laws under which this causal relation from p1 to p 2 comes. To explain the molecular configuration p2, we always seek for a complete cause and the appropriate laws within physics. If there is a complete physical cause, there will be a complete physical law as well. If there is a complete physical law, there will be a complete physical explanation as well. This implication from nomological to explanatory completeness is based on the following assumption: any metaphysical consideration of two property tokens that suffices to speak of a causal relation between them suffices to speak of a lawlike relation between the property tokens in question as well (cf. ‘concept of explanation’, chapter II, p. 71). This is all that is needed to give an explanation. Therefore, any explanatory completeness claim is mainly based on the argument for the causal completeness that implies a nomological completeness. However, if there were no complete physical explanation, there would not be an explanation in terms of the special sciences either. This implication is based on the following assumption: there couldn’t be an explanation in terms of the special sciences that fills any explanatory gap of physics, since the causal completeness of physics

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Reductionism in the philosophy of science

implies nomological completeness. For any causal change of physical property tokens, there is a complete physical cause, and hence, a complete physical law under which this change comes about. This is sufficient for an explanation. If we suppose there were an explanation in terms of the special sciences without there being a physical explanation of some physical property token, then either physics is causally (and thus explanatorily) incomplete, or the explanation of the special sciences is about non-causal physical property tokens. In order to claim the first possibility, one would have to argue against the causal completeness of physics. In order to claim the second possibility, one would have to argue for laws of the special sciences that are about causally redundant physical property tokens (epiphenomena). After all, the explanation of the special science in question would in this case be about non-causal property tokens. Since the general redundancy of epiphenomena will be considered later we can leave this possibility aside at this point (cf. ‘redundancy of epiphenomena’, this chapter, p. 31). Taking up the first possibility, then, let us suppose physics turned out to be incomplete in causal respects. As a result of this, physics would then be incomplete in nomological and explanatory respects as well. There would be physical property tokens with causal powers that do not come under physical laws and that are inexplicable in physical terms. For instance, some structural change of a molecular configuration would neither come under a physical law, nor could it explained by physics because its causes were nonphysical. Since I shall focus on causal issues, I shall take ‘explanation’ as an abbreviation for ‘causal explanation’ here (cf. ‘concept of explanation’, chapter II, p. 71). As any explanation of an entity invokes the causes of the entity in question, a physical explanation of a molecular configuration is necessarily a causal explanation. More precisely, the most detailed true description that physics is able to provide about the causal aspects of the entity in question is, in virtue of being embedded in a physical theory, a physical explanation. In this sense, explanatory completeness depends on causal completeness. If physics were causally incomplete, physics would not completely determine the probabilities of physical causal relations. In such a case, the probabilities of a structural change of a molecular configuration would have non-physical causes. Thus, in order to explain this

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change, a physical explanation would not be sufficient, and one would have to go beyond physics and might be obliged to have recourse to concepts and explanations of the special sciences. This is what we mean by the ‘completeness of physics’. Physics is complete in causal, nomological, and explanatory respects relative to the special sciences like biology. To put it simply, if there is a change of a molecular configuration, there is a complete physical cause for this change insofar as this change has a cause at all. If there is a complete physical cause for this change, there is a complete physical law under which this causal change comes, and there is a complete physical explanation of the case in question as well, and vice versa.

v.

Incompleteness of the special sciences

The special sciences are not complete in causal, nomological, and explanatory respects. Relative to physics, the special sciences are incomplete. However, within the special sciences, certain theories are complete with respect to other theories. For instance, chemistry is incomplete relative to physics, but it is complete relative to biology. Let us consider these two points in more detail. First of all, let us consider the incompleteness of the special sciences relative to physics. For instance, let us consider the incompleteness of chemistry: given any chemical property token c that can be described by chemistry, insofar as c has a cause, it does not always have a (complete) chemical cause. This means that in order to describe a complete cause (cf. ‘completeness of physics’, this chapter, p. 24) chemists often have to go beyond chemical causation. It is often not possible that chemists determine the complete cause of some chemical property token c only in terms of chemistry. The modifying ‘insofar’ leaves open cases where there might be purely physical causes, or there might even be no causes at all. Therefore, it might turn out that neither physicists nor chemists can describe the cause of c. To put it in other terms, the prior occurrences of chemical property tokens and chemical laws do not fully and/or always determine the chance for every change of chemical property tokens. Leaving aside uncaused changes,

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Reductionism in the philosophy of science

chemistry furthermore does not always provide the best explanation of chemical causal relations. For example, chemists may, in considering the chemical property tokens of an enzyme, need to have recourse to physical concepts like ‘charge’, or ‘proton’ to explain what happens when this enzyme changes its activity relative to the molecular environment. There is often a causal influence by such purely physical property tokens. Such a causal incompleteness of chemistry implies, going through the same logical steps we applied to talk about ‘completeness of physics’ (this chapter, p. 24). Second, let us consider possible completeness claims within the special sciences. For instance, let us consider once again chemistry: for any chemical property token c that can be described by chemistry, insofar as c has a cause, it does not always have a complete chemical cause. However, this incompleteness relative to physics does not imply an incompleteness relative to other theories of the special sciences. It is possible that chemistry is complete relative to biology, for instance. ‘Complete’ means, in order to give a complete cause, chemists would not be obliged to have recourse to biological causation. It is always possible that chemists figure out the complete cause of some chemical property token c only in terms of chemistry (and physics). ‘Insofar’, here again, to hedge against the possibility that there are purely physical causes, or no causes at all. It might turn out that neither physicists nor chemists can describe the cause of c. Still, in these cases, there are no biological causes of c that fill in the possible gaps in the chain of chemical causation (those that are not filled by physical causation). The chances of all changes of chemical property tokens are fully determined by prior occurrences of chemical and physical property tokens and chemical and physical laws. Leaving aside uncaused changes, chemistry together with physics always provides the best explanation of chemical causal relations. Returning to the example of an enzyme, we note that chemists might be obliged to have recourse to physical concepts like ‘charge’, or ‘proton’ to explain what happens when the enzyme changes its activity, but will never be obliged to have recourse to biological concepts. There is often a causal influence by purely physical property tokens, but biological property tokens do not fill any gap in chemistry that is not filled by physical property tokens. In any case, chemists often have to take into account a physical explanation, but

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never any biological explanation. Such relative causal completeness of chemistry implies an appropriate nomological, and explanatory completeness, on the previously explained model of the ‘completeness of physics’ (this chapter, p. 24). This is what is meant by the ‘incompleteness of the special sciences’. The special sciences are incomplete relative to physics because they are often obliged to have recourse to physical causation, laws and explanations. However, within the special sciences there are theories that are relatively complete. For instance, chemistry is complete relative to biology.

vi.

Redundancy of epiphenomena

Any epiphenomenon is redundant in causal, nomological, and explanatory respects; and if some property token is taken to be causally redundant, it will be redundant in nomological and explanatory respects as well. Let us demonstrate this implication. In the first place, any epiphenomenon is, by definition, a causally powerless entity, something that may have causes, but cannot cause anything. It is not easy to give an uncontroversial example, but for the sake of the argument, let us image the following case: a certain illness causes both organic damages that cannot be easily detected because they do not result in any pain, and the illness causes a colour change of the skin. Per se, the colour change does not cause any harm. It is a symptom of that illness that does not have any biological effects apart from indicating the illness. In this context, the colour change is an epiphenomenon of the illness in question. In the second place, and subsequent to the causal redundancy, any epiphenomenon is redundant in nomological respects. Any role of epiphenomena in laws is redundant. This nomological redundancy is based on the causal redundancy of epiphenomena. Laws are connected to causal efficacy. Laws are mainly causal laws. Indeed, if there is any causal connection, there is a law-like connection as well. By contrast, if epiphenomena do not have any effects, they are not pertinent to laws either. In fact, if there is no causal connection from an epiphenomenon to any effect, say p 2, there is not a law-like connection from that epiphenomenon to p 2 either. That is why epiphenomena are nomologically redundant, and this nomological redundancy follows from their causal redundancy.

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However, one may raise the following objection: suppose some physical property token p1 causes another physical property token p2. In addition to this, some epiphenomenon epi is either caused by p1, or supervenes on p1 (cf. ‘supervenience’, this chapter, p. 33): epi p1

p2 (causes)

Because there seems to be a parallel between the causal relation between p1 and p2, which establishes a law-like connection between them, and the causal relation (or supervenience relation) between p1 and epi, which also establishes a law-like connection, one may imagine that there is a law-like connection between epi and p2. After all, whenever an epiphenomenon of the same type as epi occurs, a property token of the same type as p2 will follow. However, such a law-like connection between epi and p2 is not based on a causal relation between the entities in question. It is moreover based on the ‘underlying’ causal relation between p1 and p2 (while epi is either caused by p1, or supervenes on it). As a result of this, the nomological role of epi can be eliminated in favour of the nomological role of p1. An example is any symptomatic side effect of an illness that only indicates the type of illness. Thus, one may diagnose an illness by means of the observed symptoms such as the colour change of the skin. Therefore, there seem to be law-like connections between these symptoms and the illness. However, there are many symptoms that do not have any causal impact on the illness in question. Consequently, such law-like connections are redundant, and hence, can be eliminated in favour of the ‘underlying’ nomological relations. In fact, there is only a law-like connection from the cause p 1 of an epiphenomenon epi to just this epiphenomenon epi. Finally, any epiphenomenon is redundant in explanatory respects. This means, the occurrence of an epiphenomenon never adds anything explanatory. This explanatory redundancy is the consequence of the causal and nomological redundancy (cf. ‘completeness of physics’, this chapter, p. 24). If there is a causal

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connection, there will be a law-like connection as well, and these in turn will provide scientific explanations. These explanations are based on laws, and laws are based on causal relations. As I have pointed out, however, since epiphenomena lack causal efficacy, they are not pertinent to laws, which also means that they cannot possess any explanatory importance. Suppose the colour change of an illness were an epiphenomenon. Then, nothing could be explained by reference to it. To sum up, epiphenomena are, by definition, causally powerless, and are thus disqualified to play any explanatory role insofar as these are based on nomological roles that are based on causal relations. From this, it follows that epiphenomena are redundant in all these three respects. Consequently, the scientific import of epiphenomena – if they have any at all – must be based on other aspects than some putative role in the causal, nomological, or explanatory dimensions. For that reason, epiphenomena are taken to be redundant in what follows in this work.

vii. Supervenience (premise two) Any property token of the special sciences supervenes on a physical property token or a configuration of physical property tokens. This is a determination/dependency relation that is suggested by our experience and that is standard in the recent literature.7 What is the core of this relationship? Let us first consider in what sense physical property tokens determine property tokens of the special sciences. Then, secondly, let us outline in what sense property tokens of the special sciences depend on physical property tokens. The first point, about the determination relation, can be spelled out as follows: any physical duplicate of our world is a duplicate simpliciter of our world:

7

Cf. Jackson (1998, p. 12) whose formulation will be considered in the following section ‘status of supervenience’ (p. 36) in more detail. Cf. furthermore Chalmers (1996, pp. 32-41). Both these conceptualisations are standard in the recent literature.

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Special sciences world 

Duplicate of spec. science world ↑

(supervenes on)

1. Physical world

2.

(determines)

Duplicate of the physical world

The term ‘physical duplicate’ means a duplicate of any physical property token in space-time. Such physical duplicates of our world preserve, we presume, all the properties of the special sciences as well. For instance, we can envision duplicates of digestive enzymes, and flowers with yellow blossoms. To put it in other terms, the physical property tokens in the world determine what property tokens of the special sciences occur in the world. The physical property tokens fix all the rest of the world. Let us go into more detail and distinguish two kinds of arguments in favour of this determination relation. We require some kind of explanation of historical existence determinations. On the one hand, physics tell us something about the history of our universe. Details are not important here. On the other hand, biology tells us something about the evolution on our earth. Details are again not important. The point I want to make here is that, in translating the story of the beginning of the universe into our physical property tokens language, we find, initially, only physical property tokens, and no entities that make applications of biological concepts true. However, at one time, physical tokens were in certain particular configurations. Subsequent to this, biological property tokens occurred. ‘Subsequent’ means, given a duplicate of the whole physical history of our universe, the history of the special sciences would either be the same or, if there were a difference in the biological history of two worlds, there would also be a corresponding physical difference in the histories of the worlds. For instance, two worlds may be indistinguishable until t1, but differ physically after t1. In any case, it is suggested that physical conditions determine the occurrence of biological property tokens. When certain configurations of physical property tokens are given, biological property tokens occur as well. To put it in other terms, physical property tokens determine the existence and the character of the property tokens of the special sciences. There were no property

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tokens of the special sciences until certain configurations of physical property tokens occurred. Some kind of duplicate determination is suggested. Our experience suggests this. Whenever we duplicate something physically, we expect to duplicate it in all other respects, an ideal we can abstract from, say, the mass production of bulk goods. For two flowers that are indiscernible from a physical point of view, this suggests that they possess the same biological property tokens (at least if there are the same environmental conditions). To put it in general terms, the same property tokens of the special sciences occur whenever the same physical property tokens are configured in the same structure. Even emergentists would not claim that certain emergent property tokens emerge from some specific physical conditions but fail to emerge when these physical conditions occur again. 8 The second point is about a dependency relation that can be spelled out as follows: a change of property tokens of the special sciences is possible only if there is an appropriate change of physical property tokens; and vice versa, no change of a property token of the special sciences occurs without a change of physical property tokens. Let us compare a biological change with regard to physics: 1.

Biological change  (supervenes on) Physical change

2.

Biological change ↓ (implies) Physical change

To illustrate this point, let us consider a flower. There is no biological change of the flower, say developing yellow blossoms, without there being a change of some physical property tokens. In a simplified and local manner, the molecular configuration of the blossom cells changes whenever the blossoms turn to yellow. One can also compare two flowers from a biological point of view. Say there is one flower with yellow blossoms, and another flower with red blossoms: their biological difference depends on an appropriate physical difference between these two flowers so that it would not be 8

Cf. Stephan (1998) for a detailed analysis of emergence.

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possible for the flowers to exhibit in biological differences but fail to differ from a physical point of view. That is what experience suggests. Let us term this ‘supervenience’. Any property token of the special sciences is determined by physical property tokens, and it depends on them. However, supervenience is an asymmetric relation in spite of this determination and dependency, since it does not imply that every physical change or difference implies a change or difference of property tokens of the special sciences as well. It is possible that two entities differ from a physical point of view, say they are different molecular configurations. Nonetheless, the two molecular configurations may come under one and the same biological concept that does not take into account the physical differences in question.

viii. Status of supervenience There are different concepts of supervenience. First of all, there is socalled global supervenience, which compares to so-called local supervenience. And within theories of local supervenience, one distinguishes between so-called weak supervenience, and so-called strong supervenience. Let us consider these different concepts of supervenience in more detail. As before, I shall begin with a defining introduction, then move on to illustrate this definition by biological examples and consider the motivation for the concept of supervenience in question, and finally I will summarize each of the concepts of supervenience by outlining its status with reference to the issues of necessity and contingency.9 First of all, let us consider global supervenience. This means the following: the property tokens of the special sciences supervene globally on physical property tokens if and only if duplicates of our physical world are duplicates simpliciter.10

9

Cf. Kim (1984) who considers the main concepts of supervenience. Cf. Jackson (1998, chapter one, especially p. 12). In order to consider the contingency that our world belongs to the set of worlds in which supervenience obtains, I shall apply his formulation of global supervenience to all the versions of supervenience. 10

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Cases like the following ones motivate such a global supervenience: the special sciences are often about property tokens that are extrinsically defined. This means that there are systems that possess property tokens only under certain environmental conditions. The fact that they possess a certain property token depends on their chemical, biological, etc. environment. For instance, the degree of fitness of a flower depends on the biological (and chemical and physical) environment. Whether or not a certain flower is well adapted to its environment, has a high rate of offspring and a high resistance against enemies, etc. depends on the environment in which it occurs. It is therefore not possible to attribute degrees of fitness to a flower without taking into account its environment. This is why extrinsically defined property tokens like that of fitness do not supervene locally on physical property tokens. The supervenience base of such property tokens has to include the physical environment as well. Since it is often difficult to limit the environment in order to conceive a definite supervenience base, extrinsically defined property tokens of the special sciences supervene at least globally on the distribution of the physical property tokens. Global supervenience is defined by metaphysical necessity. This means: assuming that biological property tokens globally supervene on physical property tokens in our world. Consequently, and necessarily, given a physical duplicate of our world, this duplicate will be a biological duplicate of our world as well. There will be trees, flowers, and animals like in our world. However, one may argue that there are possible worlds in which such a supervenience relation does not hold: worlds whose physical duplicates are not duplicates simpliciter. It is a contingent fact that our world belongs to the set of worlds in which supervenience holds. For that reason, it is appropriate to formulate the claim of global supervenience in the following manner: any physical duplicate of our world is a duplicate simpliciter of our world. 11 This takes into account the contingency that our world belongs to the worlds in which supervenience holds:

11

Cf. Jackson (1998, p. 12).

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1. Contingent that supervenience holds in our world. 2. Since supervenience holds in our world, it is necessary that: Duplicate of special sciences world ↑ (determines) Duplicate of our physical world Second, let us consider local supervenience. This means: the property tokens of the special sciences supervene locally on physical property tokens if for any physical system in our world a physical duplicate of that system is a duplicate simpliciter of that very system. Local supervenience is motivated by cases like in which it is possible to limit the physical supervenience base for property tokens of the special sciences, and thus possible to localize the physical supervenience base. For instance, one may take a molecular configuration plus its narrow molecular context as the physical supervenience base for chemical properties of enzymes or biological properties of cells or cellular components. Even if such property tokens of the special sciences are extrinsically defined, it is often the case that there is a limited or localized physical supervenience base. It is therefore not necessary to take into account the w h o l e distribution of physical property tokens in the world. The environmental conditions are limited that play any role for the property tokens in question. However, there are two different concepts of local supervenience: weak and strong. Weak supervenience means that the property tokens of the special sciences supervene on physical property tokens if and only if, for any physical system in our world, a physical duplicate of that system is a duplicate simpliciter of that very system. In contrast, strong supervenience signifies that the property tokens of the special sciences supervene on physical property tokens if and only if, for any physical system in our world, a physical duplicate of that system in any possible world is a duplicate simpliciter of that very system. Weak supervenience does not exclude cases of possible worlds in which there are physical duplicates of systems of our world that

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are not duplicates simpliciter. For instance, there are possible worlds in which there are physical duplicates of the physical configurations that make up chemical and biological systems such as enzymes, cells, and flowers in our world, but that lack the chemical or biological properties that define enzymes, cells, and flowers. In effect, these physical duplicates of systems are in worlds in which there are no enzymes, cells, and flowers. The status of weak supervenience is of necessity limited to one single world. There is no metaphysical necessity, meaning that duplicates of physical systems across possible worlds are not necessarily duplicates simpliciter. Thus, if in our world biological property tokens weakly supervene on physical property tokens, and, consequently, and necessarily, it is the case that a physical duplicate of our world is a biological duplicate as well, this comparison does not hold across possible worlds. To put it in other terms, weak supervenience in one world has no implications for other possible worlds: 1. Biological property token b 1 2. Duplicate of b1 does not  (supervenes weakly on)

occur in some worlds where

Physical property token p1

duplicates of p1 occur.

in our world Strong supervenience, on the other hand, excludes cases like the following: there are worlds possible in which there are physical duplicates of systems of our world, but these physical duplicates are not duplicates simpliciter. Consequently, any physical duplicate of an enzyme, a cell, or a flower of our world is as well an enzyme, a cell, or a flower in any other possible world. Strong supervenience is defined by metaphysical necessity. This means that when biological property tokens strongly supervene on physical property tokens in our world, a physical duplicate of a biological system in our world is a biological system in any possible world as well. The comparison across possible worlds is therefore implied by the concept of strong supervenience. To put it in other

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Reductionism in the philosophy of science

terms, strong supervenience in one world has metaphysical implications for any other possible world: 1. Biological property token b1

2. Duplicate of b1 occurs

 (supervenes strongly on)

in any in other possible

Physical property token p1

world where duplicate

in our world

of p1 occurs.

Let us sum up this discussion about the ‘status of supervenience’. I shall be taking global supervenience as a starting point, on the basis of which I am enabled to limit/localize the proper physical supervenience base of property tokens of the special sciences. Moreover, I shall accept strong supervenience because weak supervenience ends up in epiphenomenalism as I shall argue later on in more detail (cf. ‘status of the token-identity argument’, this chapter, p. 56). However, there is one important point to add. I shall take ‘supervenience’ foremost as an ontological concept without any semantic or conceptual implication. The effect of this is that any implications for the meaning of concepts of the special sciences compared to the meaning of physical concepts are not excluded from the scope of this work, being unnecessary for the development of the of ontological reductionism – and un necessary, too, for epistemological reductionism.

I. Ontological reductionism

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Ontology of property tokens ix.

Property discrimination by causal difference

Leaving epiphenomena aside, any ontological difference between entities implies a causal difference between them. Any criterion to discriminate ontologically property tokens by different concepts is based on a causal difference between the property tokens in question. However, this discrimination does not depend on any specific theory of causation. If there is any criterion to discriminate ontologically one property token from another one, there will be a causal difference as well. Before I shall consider the criteria of compositionally, functionally, and extrinsically discriminated property tokens, compared to a causal discrimination, let us repeat what I have outlined in the beginning of this chapter (cf. ‘truth-maker realism’, this chapter, p. 16), namely that I shall taking property tokens as modes – particularized ways systems are. They are basic, and they are the truth-makers for physical concepts and concepts of the special sciences. Such concepts bring out salient similarities among the property tokens (modes) in question. Keeping this first specification in mind, let’s overview possible criteria to discriminate property tokens. First, let us consider the criterion of composition to discriminate property tokens by different concepts. Configurations of property tokens can differ in their composition. For instance, we can imagine two molecular configurations that differ with regard to their atomic composition. This difference in composition enables us to discriminate them. This means that we can refer to them by different concepts (cf. ‘concept of concepts’, chapter II, p. 68). So to speak, they differ in property type, which means that they are to be referred to by different concepts. I shall take synonymously ‘property type’, ‘property concept’ and ‘concept about property tokens’ (cf. ‘concept of property types, chapter II, p. 65). Configurations of physical property tokens, for instance, are often discriminated by a criterion of composition. In general, a property type brings out salient similarities between property tokens – in this case, a certain salient composition. To put it simply, each token of a certain type of molecule is

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Reductionism in the philosophy of science

composed of certain atom tokens of certain types. An atom token of a certain type of atom is composed of a certain quantity of certain subatomic particle tokens of certain types, like electrons, neutrons, protons, etc. However, a different composition also implies a causal difference. If property tokens or configurations of property tokens are discriminated by different compositions, they can be discriminated by causal difference as well, because, as experience suggests, there is no difference in composition without causal difference. For instance, physically different molecular configurations will also differ in their causal interaction with other molecular configurations, or at least in their disposition to interact differently with the physical property tokens in their environment. One molecular configuration token p1 may have the disposition to attract px in a certain manner, while some other molecular configuration token p2 does not possess this disposition to attract property tokens of the type of px. And this difference in attraction depends on sub-atomic particle tokens. The parts of the composition always have a certain causal power, which emerges in the fact that if there is a difference in composition, there is a corresponding difference in the causal power of the composition as well: different compositions always possess different dispositions in the way in which they can react to the environment.12 Let us move on to the second criterion, the criterion of different function. A function is a relational property that is defined by some characteristic cause(s) and effect(s). Property tokens may differ functionally, that is to say, they differ with respect to one or more causes and/or one or more effects. This functional difference between property tokens provides us with a criterion to discriminate them. So to speak, they are of a different functionally defined property types. This means to be described by different concepts. These concepts are about the causal relations that define the property tokens as one of a functionally defined property type. Biological property types, for instance, are often discriminated functionally. Let us bear in mind that a property type brings out salient similarities among property tokens – in this case, a certain salient function (cf. ‘concept of property types’, chapter II, p. 65). A commonly referenced instance is that of genes that are functionally defined, for 12

Cf. Kim (1999, pp. 17-18), and Shoemaker (1980).

I. Ontological reductionism

43

instance to produce certain phenotypic effects like blossoms, the colour of the hair, etc. As implied in our definition of the functional criteria, differences in function imply causal differences. If property tokens are discriminated functionally, they can be discriminated by a causal difference as well. There is no different function without a causal difference because of the causal definition of a function. Suppose, for instance, that there are different types of genes that are functionally defined. Let us say, there are genes for red blossoms, and there are genes for yellow blossoms. This functional difference is thus based on a causal difference. The causal relation between a gene and its phenotypic effect of red blossoms is different from the causal relation between another gene and its phenotypic effect of yellow blossoms. Of course, the functional properties can be more narrowly or a more widely defined. For instance, a gene type may be defined by all its possible causal effects like the disposition to attract birds or insects in a certain manner depending on the colour of the blossoms. Thirdly, let us consider the criterion of external discrimination and its causal implication. The application of concepts to property tokens may depend on external factors. This means a true application of a concept depends on facts like history, environment, social community, etc. Since we know about differences in such external facts, this knowledge enables us to discriminate the property tokens in question by referring to them by different concepts. While they are of a different property type, however, here, too, as with our functional criteria, discrimination by means of different external facts implies possible different causal descriptions. There is no difference in an external discrimination without causal differences. Experience suggests this implication from an external discrimination to the possibility of a causal discrimination. Let us illustrate this point by the following claim: suppose there are two types of organs that can be discriminated by their different origins in history. Organ tokens of one type of organ, say of type B1, are developed naturally in the evolution, while organ tokens of another type of organ, say of type B2, are artificially developed by scientists. However, the tokens of the two types of organs may be physical duplicates at a certain time. Thus, they have different causal histories but no causal differences at this time. A difference in causal history does not imply causal differences at every instance of their

44

Reductionism in the philosophy of science

historical paths. This is the factor that motivates the following claim: property discrimination by external factors does not imply that there is always a possible local causal discrimination. Nonetheless, it is in principle possible to discriminate physically tokens of the two different types of organs in a proper way. After all, each token of an organ has its specific physical history. Therefore, they can be causally discriminated with respect to their history, although not with respect to their future effects. Naturally developed organs have a different causal past compared to synthetically developed organs. The problem of the possibility, from a physical point of view, of referring to them by one single concept does not constitute any obstacle to our discriminatory efforts here. Let us call such a single concept a ‘narrow’ physical concept that only includes in its scope something like the actual causal power. But it is in principle possible to take into account something like the ‘broader’ causal past that enables us to make a proper discrimination. To put my argument in different terms, the truth-maker for some ‘narrow’ physical concept is not identical with the truth-maker for the biological external concept. Assuming that a true application of “synthetically developed organ” depends on some specific origin in some laboratory, this truth-maker makes the application of a ‘broader’ physical concept true. To conclude, the crucial difference at this point between the extrinsically discriminated property tokens (in terms of the special sciences) and purely causal discriminations of property tokens (in terms of physics) is the following: it is sometimes possible that the special sciences can discriminate property tokens that are indiscernible from an isolated (non-historical, non-external) physical point of view. However, there is always the possibility of making a proper causal-historical discrimination in terms of physics. Furthermore, I shall assume that ‘supervenience’ holds, at least in a global manner. Therefore, one has always to consider the complete supervenience base of some extrinsically discriminated property token. If two molecular configurations that are physical duplicates are correlated with two different property tokens of the special sciences, then the molecular configurations are in fact not sufficient to count as the supervenience base of the property tokens of the special sciences in question. One has to extend the supervenience base from the molecular configuration to its molecular environment,

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its causal past, or, in the last resort, to the global causal history of the world. Let us recapitulate and term this ‘property discrimination by causal difference’. Compositional, functional, or external discrimination between property tokens is often feasible even if there is no causal difference at a certain time between the systems in question. However, if there is a compositionally, functionally, or extrinsically defined difference between property tokens, we can count on finding a causal difference in a broad sense as well. At least, such a causal discrimination in terms of physics is in principle possible – if one takes into account the causal pasts of the systems in question in which they differ. Thus, there is always a causal criterion to refer to entities by the same or different concepts. Entities are property tokens of the same type (they can be referred to by one concept) if there is no causal difference between them; and, inversely, entities must be property tokens of different types if there are causal differences between them.

x.

Identity by causal indifference

From the above it is evident that two property tokens are ontologically identical if there is no causal difference between them. This means that two concepts about one entity are about the same ontological aspects of that entity if these concepts refer to aspects of that entity that cannot be causally discriminated. For instance, a certain gene is identical with a certain molecular configuration if they cannot be causally discriminated. Both the gene and the molecular configuration have the same causes and effect(s). Tokenidentity can be based on the causal indifference of prima facie different property tokens. ‘Prima facie’ because the entity in question is referred to by concepts of different theories, like the concept “gene” and the concept “molecular configuration”. However, tokenidentity is ontological reduction. Let us articulate the four chief logical points that shape this argument. In the first place, there must always be a causal difference between different property tokens such that, if there is any difference between property tokens, there will be then a causal difference as well. Since, as we have seen, any difference in composition, function, or external discrimination implies a causal difference as

46

Reductionism in the philosophy of science

well (cf. ‘property discrimination by causal difference’, this chapter, p. 41), if these property tokens are causally indiscernible (unless they are epiphenomena), it is not possible that concepts of different theories refer to different ontological property tokens of one entity. In the second place, token-identity implies causal identity. If a biological property tokens b is identical with a configuration of physical property tokens, say p, then the causal efficacy of the one entity that is described in biological terms is identical with the causal efficacy that is described in physical terms. Even more precisely, there is no causal efficacy described in biological terms beyond the causal efficacy that is described in physical terms. After all, the physical description is more detailed and complete with respect to the biological description. This means that the causal aspects of e to which the biological concept of entity e refers are also captured in the appropriate physical concept about e. Third, let us consider the link from causal indiscrimination to ontological indiscrimination. It is a matter of ontological simplicity to identify property tokens that are causally not to discriminate. Assume an entity e that is described in biological and physical terms – for instance, an entity described by the biological concept “gene” and physical concept “molecular configuration”. As we have established in our first point, both descriptions bring out the same causal efficacy of that entity e. Both the gene and the molecular configuration have the same effects, and stand in the same causal relations with the environment. It is therefore an argument of ontological parsimony to say that what possesses the same causal efficacy is one and the same entity. This parsimony suggests that the ontological aspects of the entity e that are described by “gene” and “molecular configuration” are one and the same. To conclude, there is one and the same entity that is only described by means of different concepts. Causal indiscrimination suggests token-identity. Finally, let us consider the issue of the diachronic identity of systems. Under the assumption that there are no causal differences, one may raise the following question: is an object identical with itself if its parts change over time? For instance, can a flower be the same one if its physical parts have been exchanged? Let us consider a flower that is, at t 1, composed of a certain molecular structure. Now, imagine, that this molecular structure is changed at t2 in the following way: there are some C-atoms that are replaced by other C-atoms, and

I. Ontological reductionism

47

there are some H-atoms that are replaced by other H-atoms. Is the flower at t1 identical with the flower at t2? After all, the molecular structures are not identical. If one argues that these two flowers are not identical, one may draw the general consequence that property tokens or objects can be causally not distinguished without being identical. This would mean that causal indiscrimination would not be sufficient for identity in the context I have considered. However, this objection does not occur in the context of four-dimensionalism. This means, an object or a property token is its history in space-time. It is a process or a fourdimensional entity that has spatial as well as temporal parts. The flower therefore has parts at certain points in space-time that may differ in their physical composition compared to other points in space-time. Nonetheless, it is possible to identify the flower with such a process (as a four-dimensional entity) in order to distinguish it from other flowers. In this context, the molecular composition of the flower from t1 to t2 is a part of the flower as a four-dimensional object, while the molecular composition of the flower from t2 to tn is another part of the same flower. To put it another way, the flower as a whole exists a certain time, and the different molecular configurations are temporal parts of it. Nonetheless, it is one and the same object/flower in space-time.13 Let us rerun this ‘identity by causal indiscrimination’. Property tokens that are causally not to discriminate are identical. One the one hand, causal differences between property tokens imply ontological differences between them. For instance, biological property tokens of a certain gene differ causally from certain atoms or electrons. On the other hand, an ontological identity implies causal identity. For instance, let us assume that a certain gene token is identical with a certain configuration of physical property tokens. This implies that there are no causal difference between that gene token and that configuration of physical property tokens. After all, they are one and the same entity. Against this background, it is the argument of ontological parsimony to take property tokens that are causally not discriminant as ontologically identical. If, for instance, a certain gene token is causally indiscrimininant from a certain configuration of physical property tokens, by ontological parsimony that gene token and the molecular configuration in question have token-identity. 13

Cf. Sider (2001, ch. 5).

48

xi.

Reductionism in the philosophy of science

Causal efficacy of property tokens of the special sciences

It is evident that not only physical property tokens have effects, but that there are also property tokens of the special sciences that are causally efficacious. Let us then consider physical and biological property tokens with respect to their causal efficacy. First of all, uncontroversially, physical property tokens are causally efficacious. For instance, as suggested by physical experience, the negative charge of a molecular configuration (p 1) causes the attraction of some positively charged molecular configuration (p2). The causal efficacy of physical property tokens is necessary for the true application of physical concepts, like the concepts of charge, momentum, gravitation, etc: p2

p1 (causes)

Second, biological property tokens are causally efficacious as well. A case in point is that genes (b1) cause phenotypic effects like yellow blossoms (b 2); more generally, flowers grow, biological systems cause changes in their environments, etc. That is what experience suggests. Causal efficacy is also necessary for the true application of biological concepts, like the concepts of fitness, selforganization, autotrophy, etc: b1

b2 (causes)

Let us call this the ‘causal efficacy of property tokens of the special sciences’. Thus, property tokens of the special sciences are causally efficacious in the world as well as physical property tokens. This causal efficacy is important for any explanatory role of their proper concepts. To put it another way, explanatory relevance of concepts can be only based on the causal efficacy of the referents (of the concept) in question (cf. ‘redundancy of epiphenomena’, this

I. Ontological reductionism

49

chapter, p. 31, and furthermore ‘concept of explanation’, chapter II, p. 71).

xii. Change dependency of property tokens of the special sciences Any change in the world necessarily implies a physical change. Any change of property tokens of the special sciences thus necessarily implies a change of physical property tokens as well. Let us consider this dependency of biological changes in more detail. The implication can be spelled out as follow: if there is a biological change, there is also an appropriate physical change. For instance, take a change from some biological property token b1, say a flower of having no blossoms, to some other biological property token b2, say the same flower having yellow blossoms. There must then be an appropriate physical change as well, say of the molecular configuration of the flower. So, there are two appropriate molecular configurations, say p 1 (when b 1 occurs) and p 2 (when b 2 occurs). ‘Supervenience’ implies this corresponding physical change. Biological property tokens supervene on configurations of physical property tokens. Therefore, different biological property tokens require different subvenient physical property tokens. Whenever there is any biological difference, there has to be a physical difference as well: 1. Difference between: (supervenes on)

b1 and b2 (Biology) 



(supervenes on)

2. Implies difference between: p1 and p2 (Physics) We will call this the ‘change dependency of property tokens of the special sciences’. To sum up, every change in the world depends on an appropriate physical change. Whenever there is a change of property tokens of the special sciences, there is an appropriate change of physical property tokens. This is what experience suggests, and what ‘supervenience’ implies. To put it in the context of the

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Reductionism in the philosophy of science

previous section, the causal efficacy of property tokens of the special sciences implies physical changes in the world. It is not possible that some biological property tokens cause something without an appropriate physical change in the world.

xiii. Change determination by physics A physical change in the world is always sufficient to account for any other change. Changes of physical property tokens are sufficient to determine changes of property tokens of the special sciences. Let us consider this determination with respect to biological property tokens. Physical changes determine biological changes. Suppose some physical property token (p1) determines some biological property token (b 1) to occur (because of ‘supervenience’). In the same way, some p2 determines some b2 to occur. However, if p1 determines b1 to occur and p2 determines b2 to occur, then a physical change from p1 to p2 is sufficient to determine the biological change from b1 to b2. To extend our example form the previous section, let us once again consider a flower without any blossoms (b1). On the one hand, if the molecular configuration p1 is given, (b1) will be given as well. On the other hand, if the molecular configuration p2 is given, the flower will possess yellow blossoms (b2) as well. Consequently, the molecular configuration changes from p 1 to p 2 will determine the plant’s flowering into yellow blossoms (b2): Change from:

b1

to b2

is determined by





change from:

p1 to p2

(Biology) (supervenes on)

(Physics)

Let us rerun this ‘change determination by physics’. Changes of physical property tokens are sufficient to determine changes of all other property tokens in the world that supervene on them.

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Argument for ontological reductionism xiv. Token-identity qua causal efficacy and completeness Since any causally efficacious property token is identical with a physical property token, any causally efficacious property token of the special sciences is identical with a proper physical property token. This is ontological reduction. We will advance through the argument in five consequent steps.14 First of all, we assume a biological property token that is causally efficacious. This is what is generally taken for granted. The property tokens of the special sciences are causally efficacious. For instance, there is some gene token b1 that causes yellow blossoms b2: b1

b2 (causes)

Second, let us take the physical supervenience base of b1 and b2. There are two different molecular configurations, say p1 and p2, of which p1 forms the supervenience base for the gene (b1), and some physically different molecular configuration p 2 forms the supervenience base for the yellow blossoms (b2):

(supervenes on)

b1

b2





p1

p2

(Biology) (supervenes on)

(Physics)

Third, by our rule of ‘change determination by physics’ (this chapter, p. 50), any change in the physical domain is sufficient to determine changes of all other property tokens in the world that 14

Cf. Kim (2005, chapter 2).

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Reductionism in the philosophy of science

supervene on them. Therefore, if there were a causal relation from p1 to p 2, this would be sufficient to determine the biological change from b1 (gene) to b2 (yellow blossoms): Change from:

b1

is determined by



change from:

p1

to

b2 

to

p2

(Biology) (supervenes on)

(Physics)

Fourth, by ‘completeness of physics’ (this chapter, p. 24), for any physical property token p 2 that can be described by physics, insofar as p2 has a cause, it has a complete physical cause. To put it simply, one may take the molecular configuration p1 as the complete physical cause of the subsequent molecular configuration p2. It is at least suggested that the complete physical cause of p 2 contains p1. Nothing changes for the argument if there is some p1 + p1* that is the complete physical cause of p 2. The point is that there is some complete physical cause: b1

b2

(Biology)

(causes) (supervenes on)





p1

p2

(supervenes on)

(Physics)

(complete cause, causal law, and explanation)

Our fifth and final point derives from a comparison of biological property tokens – as, for example, b1 with their physical supervenience base – as, for example, p1. The gene (b 1) is taken to cause yellow flowers (b2) (step one). Both the gene (b 1), and the yellow flowers (b 2) supervene on molecular configurations (p1 and p2) (step two). Given that there is a causal relation between molecular configurations p1 and p2, the occurrence of the yellow flowers (b2) is sufficiently determined by the occurrence of the molecular configuration p2 (step three). In fact, the completeness of physics implies this. Thus, p1 is taken to be the sufficient cause of p2 on which the yellow blossoms (b2) supervene (step four). As a result of

I. Ontological reductionism

53

this, both b1 and p 1 seem to be sufficient for the occurrence of the yellow blossoms (b2). The gene (b 1) is taken to cause the yellow blossoms (b2), while p 1 is taken to cause the supervenience base of the yellow blossoms (b2) (i.e., p2). Against this background, there are three main possible relationships between b1 and p1 and b2 and p2: First of all, there is systematic overdetermination. This means that both b1 and p 1 are sufficient and not identical causes of b 2 (p 1 causes b2 via causing its supervenience base p2). However, there are several arguments against this possible relationship.15 Let us consider one of these arguments: the gene (b1) is no independent cause of the yellow blossoms (b2) because the gene supervenes on p1 that is taken to be the ‘competitive’ cause of b2. The gene (b1), cannot be independent from p 1 since there is the supervenience relation by ‘supervenience’ (this chapter, p. 33). The gene (b1) supervenes on the molecular configuration (p1), which is itself sufficient for the occurrence of yellow blossoms (b2) by causing their supervenience base p2. However, if b1 is not independent from p1, and p1 is causally sufficient for the occurrence of the yellow blossoms (b2), the assumption that b1 causes anything drops away: b1 merely indicates that there is an underlying base p1 that causes something. Hence, physics by itself is entirely sufficient, for every property tokens that occurs in the world. Furthermore, causation is linked to laws, and there are exceptionless laws only in physics but not in biology. In order to put the problem for the causal efficacy of biological property tokens in general terms, let us consider a physical duplicate (say w 2) of our world (say w 1). In addition to this, let us assume that genes are epiphenomena in w2. Since w2 is a physical duplicate of our world in which molecular configurations (like p1) are sufficient causes for yellow blossoms (like b 2) by causing their supervenience base p 2, there is no criterion to distinguish the causal efficacy of genes in our world from the epiphenomenal genes in w 2. This is why overdetermination leads to epiphenomenalism, which, as we have shown, is redundant (cf. ‘redundancy of epiphenomena’, this chapter, p. 31). Accordingly, I shall leave aside the possibility of overdetermination in what follows. Second, there is parallelism, or that claim that both the causal relation between b1 and b2, and the causal relation between p1 and p2 15

Cf. Kim (2005, pp. 46-52).

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exist and obtain on different levels. It is the case that the b1 causes b2, while p1 causes p 2 that is sufficient (qua supervenience) for b 2. The difference in the levels might incline one to say that the molecular configuration p1 does not directly cause the yellow blossoms b 2. However, the gene (b1) supervenes on the molecular configuration (p1), which is itself sufficient for the occurrence of yellow blossoms (b2). Consequently, if b1 is not independent of p1, and if p1 is causally sufficient for the occurrence of the yellow blossoms (b 2) (even if only qua supervenience of b 2 on p 2), there is no basis for the assumption that itself causes anything: b1 merely indicates that there is an underlying base p1 that causes something. Physics by itself is sufficient (qua supervenience). After all, causation is linked to laws, and there are exceptionless laws only in physics but not in biology. Parallelism would be a plausible option only if the special sciences were complete in the same manner as is physics. In order to put the problem for the causal efficacy of biological property tokens in general terms, let us consider once again a physical duplicate (say w2) of our world (say w1, in which I assume parallelism for the sake of the argument). In addition to this, let us assume that genes are epiphenomena in w2. Since w2 is a physical duplicate of our world in which molecular configurations (like p1) are sufficient causes for yellow blossoms (like b2) by causing their supervenience base (p2), there is no criterion to distinguish the causal efficacy of genes in our world from the epiphenomenal genes in w2. This is why parallelism leads to epiphenomenalism, which, by our ‘redundancy of epiphenomena’ thesis, is no feasible ontological position. In addition to this, there is one more consequence of parallelism: no property tokens of chemistry, biology, etc. would be causally efficient in the physical domain. This is contrary to what experience suggests. As a result of this, I shall leave aside the possibility of parallelism in what follows. Third and finally, we must consider token-identity, which is the position that the gene b 1 as identical with its subvenient molecular configuration, the physical property token p1. The argument proceeds as follows: ‘Supervenience’ (p. 33) implies that the biological property token b1 supervenes on a physical property token p1. In the same manner, ‘supervenience’ implies that b2 supervenes on p2. The gene (b 1) supervenes on molecular configuration (p1), and likewise the yellow blossoms (b2) supervene on molecular configuration (p2).

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However, if there is a biological change (from b1 to b2), there is also, by ‘change dependency of the special sciences’ (p. 49), an appropriate physical change (from p1 to p 2). To put it simply, the molecular configurations have to be physically different. Supposing that the gene (b1) is the cause of the yellow blossoms (b2), one may raise questions about whether there is also a sufficient physical condition for the biological change from b 1 to b 2. Indeed, ‘change determination by physics’ (p. 50) implies that the physical change from p1 to p 2 determines the biological change. There is a physical change that determines the biological change from the occurrence of the gene (b 1) to the occurrence of the yellow blossoms (b 2). Furthermore, the ‘completeness of physics’ (p. 24) implies that p2 has a complete physical cause. This is p1. Against this background, the gene (b1) and its subvenient molecular configuration (p 1) are not distinguishable in a causal manner. In fact, p1 causes p2, and p 2 determines b 2 to occur. The molecular configuration (p 1) is a sufficient cause for the occurrence of the yellow blossoms (b 2) as well. Therefore, ‘identity by causal indifference’ (p. 45) suggests taking p1 and b1 to be identical. After all, ‘property discrimination by causal difference’ (p. 41) implies that any other difference between the gene (b1) and the molecular configuration (p1) are rooted in the causal differences between them, and this is evidently not the case. They cannot be causally discriminated. Consequently, there is a strong causal argument for the ontological reduction of b1 to p1. The gene (b 1) is identical with its subvenient molecular configuration (p1). Since the argument can be also applied to the yellow blossoms (b2), they are taken to be identical with their subvenient molecular configuration (p2) as well:

(identical with)

b1  p1

(causes)

b2  p2

(identical with)

Let us term this the ‘token-identity qua causal efficacy and completeness’ argument. In any world in which global supervenience and the completeness of physics hold, all property tokens of the special sciences are identical with configurations of physical property tokens. To put it in other terms, since the two premises ‘completeness of physics’ and ‘supervenience’ are cogent, there is

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ontological reduction of any causally efficacious property token of the special sciences. To the contrary, if there were no token-identity, any causal efficacy of property tokens of the special sciences would be put into question. After all, overdetermination and parallelism are not feasible options. Thus, token-identity is the only way to take property tokens of the special sciences as causally efficacious. This token-identity is ontological reductionism because any property token in the world is a physical property token (or configuration of them), and only some configurations of physical property tokens are property tokens of the special sciences.

xv.

Status of the token-identity argument

In tandem, causal completeness of physics and any supervenience relation form a convincing argument for token-identity in our world. This yields ontological reduction in our world. However, those who still doubt the case for ontological reduction can point out, here, at the different strengths of the supervenience relation (cf. ‘status of supervenience’, this chapter, p. 36), firstly, and secondly, at the fact that our current physics is not unified. Let us take these objections in order. Firstly, we have claimed that local supervenience obtains in our world. However, let us consider the consequences of weak supervenience. Imagine that in our world (w1), there is a gene (b 1) that only weakly supervenes on a molecular configuration (p1), and there are yellow blossoms (b2) that weakly supervene on some other molecular configuration (p2). The molecular configuration (p1) causes the molecular configuration (p2). Furthermore, let us take for granted the common assumption that the gene (b1) causes the yellow blossoms (b2) in w1. Let us now consider a physical duplicate of our world, say w2. This means, there is a molecular configuration (p 1) that causes another molecular configuration (p2) in w2. Let us furthermore image that a gene (b 1) supervenes weakly on the molecular configuration (p1) in w2, but that there are no yellow blossoms (b2) in w2. Cases like this one are suggested by weak supervenience, since weak supervenience does not apply across different possible worlds.

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Consequently, in this case, the gene (b1) is an epiphenomenon in w2. In that world, the gene (b1) does not cause yellow blossoms, since there are no yellow blossoms (b2). Let us now compare the two worlds. From a physical point of view, there are no differences: in both worlds, the molecular configuration (p1) causes the molecular configuration (p2). But, if we compare the two worlds from a biological point of view, there are differences: in w2, the gene (b1) does not cause yellow blossoms (b2). This suggests taking the gene (b 1) in w 1 as an epiphenomenon as well, because (b1) in w1 and (b1) in w 2 are identical from a biological point of view, and in w 1, there is a sufficient condition for the existence of (b2) in supposing that b2 weakly supervenes on p2. This is why weak supervenience leads to epiphenomenalism, which, as we have pointed out, is not a feasible ontological position. For this reason, I shall leave aside the possibility of weak supervenience in what follows, and take strong supervenience to obtain in our world. This suffices for the argument for ontological reductionism in our world. After all, it is sufficient for the dependency of all the property tokens of the special sciences on physical property tokens, and it suffices for a determination by the later ones. Therefore, strong supervenience implies a ‘change dependency of the special sciences’ (p. 49) and a ‘change determination by physics’ (p. 50) in our world. This is sufficient for ontological reductionism in our world. As a result of this, I shall take the supervenience premise of the token-identity argument as generally well founded. Secondly, current physics is complete enough for the tokenidentity argument. Even if current physical laws and explanations are not ideally complete or accurate (unified in one physical theory), physics is taken to be causally complete in the following sense: physics is complete with respect to the special sciences. No current physical theory has to take into account concepts, law-like generalizations, or explanations of the special sciences in order to describe or explain a certain entity, its causal efficacy or the laws under which the entity in question comes. To put it another way, any physical change suggests that there is a complete physical cause. This causal completeness suffices for ‘identity by causal indifference’ (p. 45). There is no causal difference between a property token of the special sciences and its subvenient physical

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property token.16 For instance, a gene token and its molecular configuration token cannot be discriminated with respect to their effects, namely, in causing the flowering of some yellow blossoms. Inasmuch as ‘change dependency of property tokens of the special sciences’ (p. 49) and ‘change determination by physics’ (p. 50) obtain, and any physical change suggests a complete physical cause, the token-identity argument is well founded. Physics only has to be complete with respect to the special sciences for the token-identity argument to hold. Since there is always a physical cause that is complete relative to the special sciences, there is no causal power of property tokens of the special sciences beyond their physical causal power. This suffices for ‘identity by causal indifference’ (p. 45). Let us call this the ‘status of the token-identity’ argument. The combination of strong supervenience and a relative causal completeness of physics gives us a useful argument for ontological reduction in our world and physical duplicates of it. These two premises are sufficient for the argument because overdetermination and parallelism lead to epiphenomenalism. Since weak supervenience leads to epiphenomenalism as well, causally efficacious property tokens of the special sciences strongly supervene on physical property tokens (premise two). In addition to this, a complete physical cause is always available for physical changes insofar as they have a cause at all (premise one). Therefore, ontological reduction obtains in our world and any physical duplicate of it.

xvi. Objection to the causal drainage argument17 ‘Token-identity qua causal efficacy and completeness’ obtains even if there is no fundamental level of physics. There could be tokenidentity without an absolutely fundamental level. Let us consider the argument in three subsequent steps: First, ‘supervenience’ (p. 33) is independent from the presence or absence of a fundamental level. Whether there is a fundamental 16

This argument is in the spirit of Papineau (1993, ch. 1) and Loewer (2001). Cf. Block (2003) to whom the causal drainage argument can be traced back. Compare furthermore the objection of Kim (2003). 17

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level in physics, experience suggests that property tokens of the special sciences supervene on physical property tokens. However, let us set this point aside and consider the special sciences themselves. Experience suggests that biological property tokens often supervene on chemical property tokens. A case in point is the familiar example of genes supervening on DNA molecules plus their molecular environment that is expressed more or less in chemical terms. However, chemistry is not fundamental in an absolute sense. Physics is more fundamental. Thus, ‘supervenience’ obtains even if there were no fundamental level in physics. Second, physics has to be only complete with respect to the special sciences. It is not necessary that physics be something like an absolutely fundamental theory. A relative fundamental level, that is, a relatively complete level, is sufficient for the token-identity argument. Since there is a physical cause that is complete relative to the special sciences, there is no causal power of property tokens of the special sciences beyond physical causal power. Whether physics is an absolutely fundamental theory has no implication for the argument. Thus, a relative completeness of physics suffices for ‘identity by causal indifference’ (p. 45). Third and finally, any causally efficacious property token of the special sciences is identical with a physical property token. Let us consider this in more detail: ‘Supervenience’ (p. 33) implies that the biological property token b1 supervenes on a physical property token p1. In the same manner, ‘supervenience’ implies that b2 supervenes on p2. The gene (b 1) supervenes on a molecular configuration (p1), and likewise the yellow blossoms (b 2) supervene on a molecular configuration (p2). Whether the physical property tokens are on an absolutely fundamental level has no bearing on this relationship. If there is a biological change (from b1 to b2), there is also an appropriate physical change (from p1 to p2). ‘Change dependency of the special sciences’ (p. 49) implies this appropriate physical change from p1 to p 2. To put it simply, the molecular configurations have to be physically different. Supposing that the gene (b 1) is the cause of the yellow blossoms (b 2), one may raise questions about whether there is also a sufficient physical condition for the biological change from b 1 to b 2. Indeed, by the ‘change determination by physics’ argument (p. 50) there is a physical change that determines the biological change from the occurrence of the gene (b 1) to the

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occurrence of the yellow blossoms (b 2). Furthermore, the ‘completeness of physics’ (p. 24) implies that p 2 has a complete physical cause. This is p 1. Once again, whether physics is fundamental in an absolute sense, or only relatively compared to the special sciences, has no bearing on the logic, here. Against this background, the gene (b1) and its subvenient molecular configuration (p1) cannot be distinguished. In fact, p 1 causes p 2, while p 2 determinates b 2 to occur. The molecular configuration (p1) is a sufficient cause for the occurrence of the yellow blossoms (b 2) as well. Therefore, ‘identity by causal indifference’ (p. 45) suggests taking p1 and b 1 as identical. After all, ‘property discrimination by causal difference’ (p. 41) outlines that any other difference between the gene (b 1) and the molecular configuration (p 1) would imply causal differences between them. This is not the case. They are not to discriminate in having the same effect b 2. Consequently, there is a strong causal argument for the ontological reduction of b1 to p1. The gene (b 1) is identical with its subvenient molecular configuration (p1). This is ontological reduction of b1 to p 1, and issues of the fundamental level of physics are irrelevant, as is the possibility that physics is only complete with respect to the special sciences. Let us term this the ‘objection to the causal drainage argument’. The argument for token-identity implies a supervenience relation and a completeness within the domain of the supervenience base. However, the non-existence of a fundamental level rules out neither the required supervenience relation nor a sufficient relative completeness of physics. Thus, the argument for ontological reductionism stands.

I. Ontological reductionism

Résumé and transition This chapter was, above all, a causal argument for ontological reductionism. Given the two premises, the completeness of physics, and the supervenience of property tokens of the special sciences on configurations of physical property tokens, ontological reductionism turns out to be a well-founded position. Ontological reductionism implies that the special sciences are about the same entities (property tokens) that physics is about. Thus, there are different descriptions of the same entities. Biology is about the biological property tokens of a flower of a certain type, and these biological property tokens are identical with certain configurations of physical property tokens. Thus, physicists describe each of the flowers and their biological property tokens in question, say as some complex molecular configuration. There are, hence, biological and physical concepts about the same entities. This invites questions about the relationship of the different concepts: is there any difference between physical concepts and concepts of the special sciences when they refer to the same entities? What is the epistemological difference between different scientific points of view? I shall consider these questions in what follows.

61

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Epistemological reductionism Preliminary remark A necessary prerequisite to applying a reductionist approach to the special sciences I to demonstrate that what remains in principle is not deducible and inexplicable from a physical point of view.

Abstract This chapter presents an argument for epistemological reductionism. After an introductory framework about theories, concepts, and explanations, I shall consider the motivation and condition for epistemological reductionism. In this context, I will examine the two main reductionist strategies: the first, associated with Ernest Nagel, is a reductionist strategy towards the special sciences by means of the famous bridge-principles. The second is the so-called functional model that is developed in detail by Jaegwon Kim. However, the argument from multiple realization presents a strong argument against these models as they stand. In response to this criticism, I shall construct a new reductionist strategy that takes up elements from both Nagel’s and Kim’s models. The core of this strategy is based on the possibility of conceiving functionally defined sub-concepts of the special sciences that are co-extensional with physical concepts. By means of these sub-concepts, the special sciences can be epistemologically reduced to physics in a conservative manner that avoids their elimination and preserves their character as indispensable scientific theories.

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Framework i.

Concept of theories

Theories are our epistemological account of the world. In what follows in this section, I will briefly consider the ‘complete’ account of any entity in the world in terms of physics, the ‘incomplete’ account of specific entities in the world in terms of biology as a special science, and a general definition of a theory. First, let us begin with the complete account of the world in terms of physics. According to physicists, any entity, e, which is taken to be causally efficacious in the world can be described by physics. This ability to explain any causally efficacious entity is based on supervenience and the completeness of physics leading to ontological reductionism (cf. ‘token-identity qua causal efficacy and completeness’, chapter I, p. 51, and ‘completeness of physics’, chapter I, p. 24). As we have seen, any causally efficacious property token of the special sciences is identical with a configuration of physical property tokens that can be completely explained in terms of physics. I shall consider explanations later on in more detail (cf. ‘concept of explanation, this chapter, p. 71). For instance, let us assume that an entity can be truly described by means of the physical concept “molecular configuration”. This means, from a physical point of view, there is a certain molecular configuration in the world, and physicists can explain this molecular configuration in a complete manner. To put it simply, there is a complete physical cause for any change; and furthermore, when there is a complete physical cause for this change, there is a complete physical law under which this causal change comes, and a physical explanation of the case in question as well, and vice versa: Physics can provide a complete description of any entity e. Second, let us consider the incomplete account of the world or parts of it in terms of a special science such as biology. According to biologists, there are specific entities in the world that can be described in biological terms. Biology does not apply to every entity in the world – biology considers only specific entities. For instance, from a biological point of view, there are cells, organs, and organisms out there in the world. Each of these systems possesses biological property tokens such as a metabolic

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activity, a certain fitness, and so on. This is the biological world that exists. Assume as a case in point that the concept “gene that produces yellow blossoms” truly applies to an entity. This means, there is a certain gene token for yellow blossoms. Contrary to a physical explanation of an entity, the biological explanation of this entity is i n c o m p l e t e (cf. ‘incompleteness of the special sciences’, chapter I, p. 29). The biological explanation of the gene that produces yellow blossoms always depends on normal environmental conditions that cannot be captured in purely biological terms. One often needs to have recourse to physical concepts, law-like generalizations, and explanations in order to explain the gene that produces yellow blossoms: Any explanation of an entity e in terms of the special sciences is incomplete. Finally, let us sketch out my conception of a theory. Any theory is a certain connection of concepts that aims to explain entities of a certain type or the connection of entities of certain types. I shall consider “types” in the following section in more detail (cf. ‘concept of property types’, this chapter, p. 65). For instance, biology aims to explain the relationship between genes of a certain type and phenotypes of a certain type. In this context, a theory about genes of a certain type takes into account other concepts than the gene concept per se. The biological concept “gene that produces yellow blossoms” is defined by a certain function – to cause yellow blossoms. However, let us bear in mind that one and the same entity can often be described in terms of different theories. Taking ontological reductionism for granted, any property token that is described in terms of a special science can be described in terms of physics as well. We will term this ‘concept of theories’. Theories are connections of concepts that aim to explain the world, or parts of it. Thus, theories provide our epistemological account of the world. Furthermore, a physical explanation applies to any entity in the world and this explanation is complete. Contrary to this, the concepts of the special sciences apply only to specific entities and their explanations are incomplete.

ii.

Concept of property types

A property type is a concept that describes a certain set of property tokens. Property types are theoretical classifications, and thus concepts. Let us consider two arguments, ontological reductionism and multiple realization,

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the first of which suggests to take property types as concepts, the second of which excludes taking property types as ontological types. Nonetheless, there are natural kinds. Property tokens form natural kinds in virtue of salient similarities among them. Property types (concepts) can express natural kinds – bring out the salient similarities among property tokens. While the more detailed examination of the multiple realization argument will wait for later in this chapter (cf. ‘argument of multiple realization’, this chapter, p. 117), I shall outline the themes relating to property types in order to sketch out the framework of this chapter. First, let us consider property types in the context of ontological reductionism. Let us imagine a molecular configuration as an example of a physical property token p of type P, although not necessarily exclusively of type P. If an entity e is a property token of a certain type, this does not necessarily imply that e is exclusively of that type. Taking ontological reductionism for granted, any biological property token b is identical with a configuration of physical property tokens. Therefore, any biological property token b such as a gene token for yellow blossoms is of two types – of the biological type in question, say B, and of the physical type P. This suggests that the property type in question describes a certain set of entities from a specific scientific point of view. One and the same entity is described by means of both a biological, and a physical type. The following argument strengthens this suggestion. Second, let us consider the consequence of taking the multiple realization position on property types as concepts. Based on the argument for ontological reductionism of chapter one, any property token of the special sciences is identical with a configuration of physical property tokens. For instance, each gene token for yellow blossoms is identical with a certain molecular configuration:

(identical with)

b1  p1

(gene token of a certain gene type) (molecular configuration of a certain type)

Furthermore, under the assumption that property types are ontological types, any property type of the special sciences has to be identical with a physical property type. Let us now assume two biological property tokens of one gene type such as ‘gene that produces yellow blossoms’. In addition to this, let us assume that these gene tokens for yellow blossoms physically differ. Such a physical difference, we will see, is claimed by the argument of multiple realization (cf. ‘argument of

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multiple realization’, this chapter, p. 117). This means, it is possible that two gene tokens for yellow blossoms are of different physical types. There are physical differences between the gene tokens that do not impinge upon the claim that these gene tokens are of one and the same type: Multiple realization of a biological type, for instance ‘gene that produces yellow blossoms’: ‘gene that produces yellow blossoms’  gene tokens: mol. conf.:

(are of one single gene type)

b1 b2   p1 p2

(identical with)



(are of different physical types)

‘mol. conf. of type P1’



‘mol. conf. of type P2’

As a result of this possibility, the biological property type ‘gene that produces yellow blossoms’ cannot be something ontological beyond any of the physical types. Ontological reductionism excludes such a possibility. Each of the two gene tokens for yellow blossoms is identical with a certain molecular configuration. However, these two molecular configurations are of different types. Therefore, the biological type (such as a type of genes) and the physical types (such as types about molecular configurations) can only be concepts that truly apply to certain sets of property tokens. This is the consequence of multiple realization together with ontological reductionism, and a strong argument for taking a property type as a concept. Any property type is taken to be a concept that describes sets of entities. Entities belong to a certain set because of certain similarities among them. I shall take the term “property type” as such in what follows:

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B

(biological property type) =

“B”

(biological concept)

(makes true)





(comes under concept)





e1

e2 (entity)

e1

e2

(entity)









(comes under concept)

P1

P2 (physical property types) = “P1” “P2” (physical concepts)

(makes true)

Against this background, let us finally consider natural kinds. Natural kinds are something ontological. Concepts are not. However, concepts bring out salient ontological similarities among property tokens. I shall consider this point in the next section in more detail. This means, natural kinds are based on salient similarities among property tokens. These similarities are brought out by concepts. So, for instance, the gene as a natural kind consists in ontological similarities among certain property tokens. This is why the property tokens in question make true one and the same concept (“gene”). Let us call this the ‘concept of property types’. Since any property token coming under a certain type of the special sciences is identical with a configuration of property tokens coming under a certain physical type as well, we cannot take the entities in question to be exclusively of one type. Furthermore, it follows from ontological reductionism and the possibility of multiple realization that property types cannot be something ontological. The property types of the special sciences cannot be identical with physical property types. Therefore, property types are concepts about certain sets of entities. In this context, natural kinds consist in salient similarities among property tokens, the similarities of which are brought out by concepts.

iii.

Concept of concepts

In order to describe entities that are out there in the world, we use concepts. This means that in order to describe certain entities, say e1, and e2, physicists apply physical concepts such as “charge” or “molecular configuration”, chemists apply chemical concepts like ”enzyme” or “acid”, biologists apply biological concepts such as “flower” or “gene”, and so on. Thereby, concepts are always embedded in a theory such that the application of concepts distinguishes entities and brings out what the

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entities in question have in common. In this section we will consider the general aim of any certain science to describe entities, the function of concepts to bring out what entities have in common, the function of concepts to distinguish entities, and the extension of concepts. First, let us take the general aim of a science to describe entities. In order to describe these entities, we must use concepts that are embedded in the context of other concepts. This is what it means to describe an entity in the world: applying a certain concept to the entity in question. Thereby, the concept in question stands in the context of other concepts of the theory in question. Suppose we describe entities in the world in terms of physics. Our descriptions apply concepts from physics’ specific or proper concepts. For instance, the physical concept “charge” is what physicists tell us about the entities the concept “charge” truly applies to. Physical concepts are different from the concepts of the special sciences, for instance the biological concept “gene”. However, the purpose of any concept is to apply itself to the accurate description of its target entity, so that, for instance, to describe an entity e1 in the world is to apply a concept to e 1, which is embedded in the context of other concepts. In order to simplify the issue, let us take a ‘concept about an entity’ as an abbreviation for a ‘true application of the concept about an entity’ or ‘description of an entity in terms of the theory in question’. Second, let us examine the function of concepts to bring out what entities have in common. If two entities are indistinguishable from a certain theoretical point of view, they are described by the same concept of the theory in question. For instance, if the entities e1 and e 2 are indistinguishable from a physical point of view, the corresponding physical description will be by the same concept, say “atom” or “molecular configuration of type P”. In this context, physicists refer to the charge of atom tokens always by the concept “charge”. Thus, in order to bring out what entities have in common under a certain aspect we use the same concept, so that we can assume, if two entities are described by means of the same concept, the concept brings out what the entities in question have in common. There is no difference between the two entities as described by the concept in question: Concepts bring out what entities have in common. Third, let us consider the function of concepts to distinguish entities. If two entities can be distinguished from a certain theoretical point of view, they are described by different concepts of the theory in question.

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For instance, physicists refer to the negative charge of an electron, which differentiates it from the positive charge of a proton, by the application of the concept “negative charge” instead of “positive charge”. Thus, in order to distinguish entities from a certain theoretical point of view, we use different concepts: Entities are distinguished by means of different concepts. Finally, the extension of a concept, say the “gene that produces yellow blossoms”, consists of all and only the entities out there in the world that make an application of the concept in question true. Naturally, as truth makers of the same concept, there a certain similarities among these entities: and in virtue of these similarities, they can be grouped together and regarded as forming a certain set characterized by making true the same concept. For instance, each entity that causes yellow blossoms makes the application of the concept “gene that produces yellow blossoms” true such that this entity belongs to the extension of the concept in question: 1.

“B” ↑

(biological concept)

2. e1, e2, … en = extension of “B”

(make true)

e1, e2, … en (entities) We term this the ‘concept of concepts’. The general aim of the sciences is to use concepts to describe entities in the world. In practice, this implicitly brings out what entities have in common and what distinguishes them. Entities that come under the same concept are indistinguishable as being described in the same way. Contrary to this, entities that are described by means of different concepts (of one science) are distinguished with respect to the applied concepts. Thereby, the extension of a concept is all and only the entities that make the application of the concept in question true.

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Concept of explanation

Explanations have been constructed differently by philosophers, depending on whether they are using the deductive-nomological model of explanation, in which the description of an entity is deduced from appropriate law-like generalizations, or the causal model, which refers to the existence of an entity in terms of its causes. In the context of epistemological reductionism, I shall prefer causal explanations in order to explain the existence of certain property tokens, bearing in mind that causation is linked to laws. Against this background, the prominent model in the sciences – the concept of reductive explanations – will be introduced. Furthermore, I shall consider homogeneous explanations and indicate the indispensability of the special sciences in the context of causal explanations. We will firstly consider explanations in general terms, for which we need to overview the development of the debate about explanations, and then compare the two main models.18 Then we will consider two other models, the reductive and the homogeneous. An explanation of a property token is based on an appropriate law-like generalization and is expressed in the vocabulary of a theory. For instance, the explanation of a token of yellow blossoms is expressed in biological terms, or the explanation of a certain molecular configuration is expressed in physical terms. This means, there is a biological law-like generalization under which the token of yellow blossom comes, or there is a physical law or law-like generalization under which the molecular configuration in question comes. This general approach to explanations takes into account the continuing debate that started in the 1950s and 1960s with the introduction of the deductive-nomological approach to scientific explanations by Carl Gustav Hempel and Paul Oppenheim.19 I shall come back to this model later on in this section. Let us just note here that this first-prevailing model as proposed by Hempel and Oppenheim in 1948 contained several shortcomings. Among which, we note the lack of accounting for scientific understanding that is reached by explanations that satisfy the criteria of the model. In other words, according to Hempel and Oppenheim, explanation is prediction. However, to predict, for instance, the change of the weather by means of a barometer change does not increase our understanding of 18

For a general consideration of the development of the debate, see Woodward (2003). In order to consider especially the deductive-nomological and the causalmechanical model in the context of laws and causality, cf. Psillos (2002). 19 Cf. Hempel & Oppenheim (1948) and Hempel (1962, and 1965).

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the change of the weather. In this context, the barometer only indicates something without being relevant for a genuine explanation. The original deductive-nomological model of Hempel and Oppenheim failed to account for this fact. This is why philosophers such as Michael Friedman and Philip Kitcher have tried to modify the deductive-nomological model.20 To put it another way, they took the deductive-nomological model as a necessary condition for scientific explanation, and proposed strategic changes that would account for scientific understanding. This is the so-called unificationist approach – scientific explanation by means of unification. According to Friedman, unification is about reducing the number of independent theories that are needed in order to explain the entities in question. For instance, Newton’s theory of motion increases the scientific understanding of many entities that were beforehand explained by a conjunction of different theories or laws (Kepler’s law, Boyle-Charles law, etc.) because it is only one theory that is needed in order to explain. Another similar unificationist approach proposed by Kitcher posited that the distinguishing characteristic of the scientific understanding of the explananda was the fact that one and the same argument pattern is used again and again. For instance, if one and the same law or theory applies to many (different) objects. This, to use our Newton example, favours Newtonian theory to the other mentioned laws because Newton’s theory can describe, and thus, explain many divers entities. To put it another way, the extension of Newton’s theory is bigger than the extension of each of the other laws. By means of this, unificationists sought tried to avoid the shortcomings of the deductive-nomological model. I will come back to Kitcher’s approach later on, in the biological part of this work (cf. ‘the approach’, ch. IV, p. 199). The rise of functionalism in the philosophy of science witnessed the use of another explanatory model, the causal-mechanical one, which has become predominant. While both the deductive-nomological and the unificationist model are not committed to a purely causal approach to the explanandum (what one intends to explain), philosophers such as, most currently, Wesley Salmon proposed that an emphasis on causality was

20

Cf. Friedman (1974) who was the first to consider the unificationist approach. Let us note that Friedman gives a good overview of the development of the debate from Hempel and Oppenheim (1948) to the debate in the 1970s. Compare furthermore Kitcher (1981) who criticises Friedman’s approach and provides another unificationist model of scientific explanation.

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indeed the mark of scientific explanation.21 This causal approach tries to identify the scientific understanding of the explandum in question with an understanding of the causal features of a given event. Let us briefly compare the deductive-nomological and the causal-mechanical models in order to bring out features of explanation that are relevant to the larger project of reductionism in more detail. Deductive-nomological explanations, as we have seen, deduce the description of a particular property token that is to be explained from a law-like generalization in which the concept that describes the property token in question figures: that deduction is carried out by means of auxiliary premises describing the circumstances in which the property token in question occurs. This is the general schema of a deductivenomological explanation within a theory. One can apply this schema also to the relationship between theories of different sciences. One may take, for instance, physical law-like generalizations into account in order to deduce biological law-like generalizations, and thus also explain, biological laws. This means, the biological deductive-nomological explanation of a biological property token will be embedded in a more general, physical, deductive-nomological explanation. In other words, the description of some given biological property token can be deduced from a biological law-like generalization. This is an explanation of a particular entity by means of a general law-like generalization. This law-like generalization can, in turn, be deduced from a more general law-like generalization. In this context, the biological law-like generalization that applies only to biological property tokens can be deduced from physical law-like generalizations that apply also to non-biological property tokens. How this deduction proceeds will be considered later on in more detail (cf. ‘Nagel’s model of reduction’, this chapter, p. 89). To conclude, the explanation of a particular biological property token by means of a biological law-like generalization can be deduced from a physical law-like generalization that is more general than the biological law-like generalization. Ontological reductionism suggests this possibility of deducing lawlike generalizations of the special sciences from physical law-like generalizations. After all, any property token of the special sciences is identical with a certain configuration of physical property tokens. Furthermore, because of the completeness of physics, there is a complete nomological description of, say, the yellow blossom token in question in terms of physics. This fact suggests the possibility of deducing the 21

Cf. Salmon (1998) who outlines in detail a causal conception of explanation.

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biological law-like generalizations under which the property token in question comes from physics. In other words, the deductive-nomological model aims to deduce the biological law-like generalizations from the physical complete nomological description of biological property tokens; and, on the basis of this deduction of law-like generalizations, it aims to deduce the biological explanation of an entity from the appropriate physical explanation of that entity. Now consider the quite procedure given to us by the aim of the causal explanation of an entity, which aims to explain the existence of some given entity. This difference is important even if causation is tied to laws. As I shall show later on, the deductive-nomological model can be combined with the model of causal explanation. In general, causal explanations aim to explain the occurrence of a certain entity. In order to explain the existence of an entity, one explains it causally.22 Even more precise, in order to explain the existence of an entity, one has to explain the causation of the entity in question. If an entity e 1 causes an entity e2, this causation by e 1 enables us to explain the occurrence of e 2. For instance, the occurrence of yellow blossoms can be explained by a token of a certain gene type (for yellow blossoms) that causes yellow blossoms. The occurrence and causal efficacy of this gene token explains the existence of yellow blossoms. Why entity e2 occurs is, hence, explained by the causal efficacy of e 1. A concept that considers the causal relation between e1 and e 2 explains the occurrence of e2. This explanation is based on a causal law or law-like generalization that connects entities of the type of e1 with entities of the type of e2. Such an explanation of the existence of an entity is generally not accessible by means of a deductive-nomological explanation. To come under a biological law-like generalization or a physical law-like generalization does nothing to explain the existence of a certain property token. It only takes away what is mysterious or astonishing about the property token in question because the description of that property token can be deduced from a general regularity. However, to deduce a biological law-like generalization under which an entity such as a certain token of yellow blossoms comes from a physical law-like generalization does not as such explain the existence of those yellow blossoms. As long as the deduced biological law-like generalization about the yellow blossoms does not include a causal explanation of those yellow blossoms, the existence of the yellow blossoms is not explained by means of that deductivenomological strategy. I shall therefore focus on causal explanations. 22

Cf. Chalmers (1996, p. 44), and Lewis (1986, p. 217).

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Nonetheless, our comparison should intimate that the way in which the deductive-nomological model of explanation can be combined with the causal model of explanation, capturing all important dimensions of scientific explanation. If for instance a biological causal explanation of yellow blossoms can be deduced from causal physical law-like like generalizations under which the yellow blossoms come, this deduction figures in a causal explanation of the existence of the entity in question. Thereby, the term ‘explanation of an entity’ can be taken as an abbreviation for ‘causal explanation of an entity’. To put it in general terms, to explain an entity is to apply a concept that considers the causes of the entity in question (cf. ‘Kim’s model of reduction’, this chapter, p. 99, and ‘functionally defined concepts’, this chapter, p. 109). The cause of an entity explains that entity: A causal explanation of an entity explains the existence of the entity in question. For instance, the biological causal explanation of the property token b2 explains the existence of b2 in terms of its cause, namely b1 “B”

(causal explanation in terms of biology)



(explains the existence of b2)

b1

b2 (causes)

Second, let us consider reductive explanations. A reductive explanation is a causal explanation of property tokens of a certain special science in terms of a science that is relatively complete and more general compared to the special science in question. It is in the last resort a physical explanation. In general, a reductive explanation is a causal explanation that is specified by three criteria.23 In order to illustrate these three criteria, let us consider a biological property token like a gene token for yellow blossoms. A) The gene token for yellow blossoms comes under a biological concept that is defined by a causal task. This means, a property token comes under that concept if it fulfils the causal task in question. I shall consider this point later on in more detail (cf. ‘Kim’s model of reduction’, this chapter, p. 99). For instance, a property token comes under the 23

Cf. Chalmers (1996, pp. 42-51) and Kim (2005, pp. 108-120).

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concept “gene that produces yellow blossoms” if it possesses the causal disposition that defines genes for yellow blossoms – to produce yellow blossoms. B) The reductive explanation of this gene token for yellow blossoms is a causal explanation in terms of a science that is more general than biology. Such a science contains concepts that belong to the supervenience basis for the truth-values of biological concepts. I shall consider this point in more detail in the next section (cf. ‘supervenience of truth-values’, this chapter, p. 79). A more general science than biology is a science that is relatively complete with respect to biology (cf. ‘incompleteness of the special sciences’, chapter I, p. 29). In this context, the truth-values of the applications of biological concepts supervene on appropriate physical descriptions, and physics is relatively complete with respect to biology, which means that physics is a more general science than biology. Since we focus on the relationship between the special sciences and physics, a reductive explanation generally is a physical explanation. C) A reductive explanation of the gene token for yellow blossoms explains why the property token in question comes under the concept “gene that produces yellow blossoms”. To put it another way, the gene token for yellow blossoms comes under the concept “gene blossoms” if it fulfils the causal task that defines the concept “gene” (first criterion). If physics explains how the gene token causes yellow blossoms, this physical explanation is a reductive explanation of the gene token in question. To put it simply, physics explains how a gene token causes yellow blossoms – and this causation defines the gene token to come under the concept “gene that produces yellow blossoms”. I shall reconsider these issues later on in more detail (cf. ‘Kim’s model of reduction’, this chapter, p. 99, and ‘functionally defined concepts’, this chapter, p. 109). A reductive explanation of a property token of the special sciences is, hence, a physical causal explanation that explains why the token in question satisfies the causal task defining the relevant concept of the special science for a given property token. It is a causal explanation of a property token of the special sciences in terms of physics – thus, it is a causal explanation across theories:

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Three conditions for “P” to be a reductive explanation of the biological token b2:

“B” (“gene that produces yellow blossoms”) (concept defined by causal task) 

1. b1

(b1 comes under concept “B” because it fulfils the causal task)

b2 (causes)



2.

(“P” applies to b2; is of a more general science than “B”)

“P” (physical concept embedded in physics) 

3. p1

(“P” about causal task of p1 to p2; and b1 = p1, b2 = p2)

p2 (causes)

Third and finally, let us turn to homogeneous explanations. In general, two explanations are homogeneous if they are applications of the same concept. For instance, the biological explanations of e2x and e 2y are homogeneous if both these entities are explained by an application of one and the same concept, say “B”, which means that the two entities e2x and e2y are biologically explained in the same way. To explain entities in a homogeneous manner is of epistemological interest because it is of scientific value to bring out what entities have causally in common – to explain entities causally in a homogeneous way. This is important for, as we will show later on, this capability that makes the special sciences indispensable from a scientific point of view. They can explain certain entities in a homogeneous manner while physics cannot explain the same entities in a homogeneous manner. In the context of causal explanations, the special sciences can focus on salient causal relations in a way physics is not able to do – physics often provide only so-called heterogeneous explanations (cf. ‘multiple realization argument’, this chapter, p. 117):

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Condition for homogeneous and heterogeneous explanation: “B”

(biological concept) (homogeneous biological explanation of e2x and e2y)





(come under one single concept)

e2x

e2y

(entities)





(come under different concepts)

“P2x” “P2y”

(physical concepts) (heterogeneous physical explanations of e2x and e2y)

Our above discussion gives a meaning to the term ‘concept of explanation’. Explanations are expressed by concepts embedded in theories. Furthermore, to explain the existence of an entity is to give a causal explanation. In addition to this, physical causal explanations that explain why certain entities fulfil the causal tasks that define concepts of the special sciences are called ‘reductive’ explanations. Finally, we generally seek for homogeneous explanations. Entities are homogeneously explained provided that they come under the same concept (in one science).

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Motivation and conditions for epistemological reductionism v.

Supervenience of truth-values

The truth-value of all special science descriptions supervenes on a complete physical description of the world. The truth-value of the application of a concept of the special sciences to an entity supervenes on the truth-value of an appropriate application of physical concepts to that entity. Let us outline some general points and examine the determination and dependency relation of supervenience in the context of concepts. First, let us consider the starting point for the supervenience of truthvalues and clarify some terminology. Any causally efficacious property token of the special sciences is identical with a certain configuration of physical property tokens (cf. ‘token-identity qua causal efficacy and completeness‘, chapter I, p. 51). Therefore, one and the same property token can make applications of different concepts true (cf. ‘truth-maker realism‘, chapter I, p. 16). For instance, let us imagine that a token of a flower with its biological property tokens such as yellow blossoms is identical with a certain molecular configuration with its physical property tokens. Thus, there is one entity that makes both the biological concept of the flower in question, and a physical description true: this entity makes the application of both a biological concept, say “B”, and a complete physical description, say “P”, true. In this context, let us use ‘complete physical description of an entity’ as an abbreviation for ‘the application of every physical concept that the entity in question makes true’. To take a complete physical description is important because the truth-values of concepts of the special sciences do not supervene on the truth-values of single physical concepts. For instance, the truth-value of “this is a flower with yellow blossoms” does not supervene on the truth-value of “this has a certain mass” but, rather, on a more expanded physical description. After all, the flower with yellow blossoms is identical with a molecular configuration that possesses also other physical property tokens than a certain mass. Second, let us consider the determination relation of supervenience. A complete physical description of the world determines the truth-value of any concept of the special sciences about the world. The completeness of physics and the argument for ontological reductionism suggest this determination relation. After all, if the property tokens of the special

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sciences globally supervene on configurations of physical property tokens, a complete physical description of the world determines which concepts of the special sciences are true about the world as well. Moreover, since the argument for ontological reductionism is cogent, it is possible to consider the determination of truth-values also in a more local context: a complete physical description of an entity (plus its environment) determines the truth-value of any concept of the special sciences about the same entity. Let us consider such a case in more detail. Suppose an entity e 1 is, from a biological point of view, a flower with yellow blossoms. This entity makes true both a complete physical description, “this is a molecular configuration of type P1” (“P1”), and “this is a flower with yellow blossoms” (“B1”). Let us bear in mind that types are concepts such that the concept “molecular configuration of type P1” is a physical concept about molecular configurations that are within the scope of the extension of the concept “P1”. In this context, a complete physical description by means of the concept “P1” cannot be true about another entity e 2 (plus its environment) without the biological concept “B1” being true as well about that entity. For instance, if there is another token of a molecular configuration of type P1, this will be a flower with yellow blossoms as well. Thus, a true complete physical description of an entity determines the truth-value of any biological concept about the same entity: Truth-value of a biological description about an entity 

(supervenes on)

1. Truth-value of complete physical description of the entity in question

Truth-value of any biological description about the entity in question ↑

(determines)

2. True complete physical description of an entity

Finally, let us consider the dependency relation of supervenience. If the application of one concept of the special sciences is true about one entity but false about another entity, this difference in the truth-values of the application of the same concept depends on a corresponding difference between the truth-values of the complete physical descriptions of the entities in question. To put it another way, the differentiation of entities in terms of the special sciences is made possible only by appropriate differences in the physical description of these entities. In order to

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illustrate this point, let us consider once again a flower with yellow blossoms. An entity e1 makes true both a complete physical description, say “molecular configuration of type P1”, and a biological description, say “flower with yellow blossoms”. From a physical point of view, the entity e1 is a molecular configuration of type P1, and for biologists, the entity is a flower with yellow blossoms. However, let us suppose that the biological concept “flower with yellow blossoms” is false about some other entity, say a flower with red blossoms, which we will call e2. Then, the complete physical description of the entity e2 cannot come under the concept “molecular configuration of type P1”. “This is a molecular configuration of type P1” must be false likewise about e2. If “this is a flower with yellow blossoms” is wrong about e2, “this is a molecular configuration of type P1” will be wrong as well (because e 2 is a molecular configuration of a different type). Therefore, a change or difference of the truth-value of a concept of a special science depends on an analogous change or difference of the truth-value of the corresponding complete physical description: 1. Truth-value of a biological description about an entity 

(supervenes on)

Complete physical description of the entity in question

2. Change of the truth-value of the biological description about an entity ↓

(implies)

Change of the truth-value of the complete physical description of the entity in question

Summing up, we will call this ‘supervenience of truth-values‘. A complete physical description of an entity determines how to describe this entity in terms of the special sciences. Furthermore, any difference in the description in terms of concepts of the special sciences depends on an appropriate difference of the physical description. Taking the argument for ontological reductionism for granted, I shall apply the concept of supervenience only to truth-values of concepts in what follows. After all, property tokens of the special sciences are identical with configurations of physical property tokens and token-identity is a stronger relation than the supervenience relation.

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Universality of physical concepts

Physics can refer to any causally efficacious property token, even those of the special sciences. Let us consider an implication of ontological reductionism and the completeness of physics, and examine this implication in the context of the ‘concept of concepts’. First, let us summarize the previously given argument for ontological reductionism and the completeness of physics in relation to physical descriptions. Any causally efficacious property token of the special sciences is identical with a certain physical property token (cf. ‘token-identity qua causal efficacy and completeness’, chapter I, p. 51). As a result of this, physics can describe every causally efficacious property token of the special sciences. Moreover, it is not possible for there not to be a complete physical description of any causally efficacious property token of the special sciences. As per ‘completeness of physics’ (chapter I, p. 24) for any change of a causally efficacious property token that is considered in terms of the special sciences, there is a complete physical cause for this change as well. If there is a complete physical cause for this change, there is a complete physical law under which this causal change comes, and there is a complete physical explanation of the case in question as well. Strictly speaking, physics can of course also describe any physical property token that is only considered in terms of physics – property tokens that are not identical with some property token of a special science. After all, there are also entities that are just electrons or atoms, but are not parts of configurations of physical property tokens that are chemical or biological property tokens. However, since I focus on the relationship between physics and the special sciences, I shall consider only configurations of physical property tokens that are also property tokens of the special sciences. The interesting questions in this chapter are concerned with the relationship between concepts of different sciences when these concepts apply to one and the same entity. To put it simply, what is the relationship between a biological description of a gene or of a flower and the complete physical descriptions of these entities? Second, concepts bring out what each and all the entities of their extension have in common, and distinguish these entities from each and all the entities that are not within their extension. In this sense, physics outlines what entities, say e1 and e 2, have physically in common with the corresponding physical descriptions of the same type – say, using the same concept “P” (cf. ‘concept of concepts’, this chapter, p. 68). As a result of this and the previous points, physics outlines what causally efficacious

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property tokens of the special sciences have physically in common if the same physical concepts apply to them. Whenever two causally efficacious property tokens in the world have something physical in common, physics can outline what they have in common. We will call this the ‘universality of physical concepts’, defining it as the claim that any causally efficacious property token that can be described by the special sciences can be described by physics as well. Moreover, the description and explanation of property tokens of the special sciences in terms of physics is complete. In addition to this, physics reveals what causally efficacious property tokens of the special sciences have physically in common.

vii. Motivation for epistemological reductionism The aim of epistemological reductionism is to link systematically the special sciences with physics such that any causal explanation (via lawlike generalizations) of the special sciences can be deduced from physical (reductive) explanations and law-like generalizations. In order to reach such reductive explanations and deductions of law-like generalizations, any reductionist model is committed to establishing a co-extensionality of physical concepts with concepts of the special sciences. We shall later examine the two prominent reductionist strategies and the necessity of coextensionality for epistemological reductionism in more detail (cf. ‘necessity of co-extensionality for epistemological reductionism’, this chapter, p. 85, ‘Nagel’s model of reduction’, this chapter, p. 89, and ‘Kim’s model of reduction’, this chapter, p. 99). In this section, let us focus on a suggestion for understanding the role played by this coextensionality of concepts of the special sciences with physical concepts, and the aim of epistemological reductionism. First, let us recall our arguments that together suggest that any concept of the special sciences is co-extensional with a physical concept. There are three main points that motivate this conclusion. A) Physics is taken to give a complete explanation of any causally efficacious property token in the world. This reflects our knowledge of physics and takes into account ontological reductionism (cf. ‘completeness of physics’, chapter I, p. 24, ‘token-identity qua causal efficacy and completeness’, chapter I, p. 51, and ‘universality of physical concepts’, this chapter, p. 82).

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B) Any concept that figures in explanations reveals what the referents of its applications have causally in common (cf. ‘concept of concepts’, this chapter, p. 68, and furthermore ‘concept of explanation’, this chapter, p. 71). C) Any ontological difference is based on a causal difference, and ontological identity is based on causal indiscrimination (cf. ‘property discrimination by causal difference’, chapter I, p. 41, and ‘identity by causal indifference’, chapter I, p. 45). From this it follows that explanations of the special sciences cannot refer to something ontological out there in the world that is not identical with a physical property token. There is nothing causally efficacious out there in the world, even in the special sciences, beyond what is captured by physical explanations and thus physical concepts. If there were, the principle of the completeness of physics would be false. Assume that the argument for the completeness of physics is compelling and that the explanations of the special sciences are causal explanations as well. Consequently, there is a systematic relationship between the physical explanations and the explanations of the special sciences. This relationship suggests that any concept of the special sciences is co-extensional with a physical concept. More precisely, this relationship suggests that it is possible to construct physical concepts that are co-extensional with concepts of the special sciences. Later on, examining Nagel and Kim’s positions, I will examined the construction of physical concepts in order to establish co-extensionality later on in more detail (cf. ‘Nagel’s model of reduction’, this chapter, p. 89, and ‘Kim’s model of reduction’, this chapter, p. 99). Second, let us consider the aim of epistemological reductionism. Reductionist models aim to link systematically the special sciences with physics such that any explanation and law-like generalization of the special sciences can be deduced from physical (reductive) explanations and law-like generalizations. In other words, epistemological reductionism aims in the last resort at explaining physically what concepts (embedded in a theory of the special sciences) can only explain in an incomplete manner. Thus, explanations in the special sciences will often recourse to, in the last resort, physical concepts, without the reverse being the case. Thus, since physics is complete, and any concept of the special sciences is coextensional with some physical concept, epistemological reductionism is well motivated – it functions to reduce incomplete explanations of the special sciences to complete explanations of physics. More precisely, the incompleteness of the special sciences, the completeness of physics and

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the argument for ontological reductionism suggest what characterizes epistemological reductionism: the deduction of incomplete law-like generalizations of the special sciences from complete physical law-like generalizations and homogeneous reductive explanations of property tokens that are only incompletely explained in terms of the special sciences. Note that, since our focus is on the prevailing conception of causal explanations, we shall only consider law-like generalizations that are about causal relations among property tokens. We call this the ‘motivation for epistemological reductionism’ argument. The aim of epistemological reductionism is to link systematically the special sciences with physics such that any explanation and law-like generalization of the special sciences can be deduced from physical (reductive) explanations and law-like generalizations. For instance, any reductionist model aims to correlate a certain biological concept, such as “gene that produces yellow blossoms”, with a certain physical concept. Assuming that there are causal relations between gene tokens for yellow blossoms and yellow blossoms, one can in an oversimplified manner say that there is a law-like generalization describing such gene tokens and their phenotypic effect of yellow blossoms. Given ontological reductionism and the completeness of physics, we conclude that these gene tokens and yellow blossoms also come under a physical law-like generalization. Epistemological reductionism now aims to deduce the biological law-like generalization about gene tokens for yellow blossoms from physical law-like generalizations. The completeness of physics and the incompleteness of biology together motivates this aim. Based on this deduction of law-like generalizations it is possible to provide systematically reductive explanations of gene tokens for yellow blossoms that are only incompletely explained in terms of biology.

viii. Necessity of co-extensionality for epistemological reductionism The co-extensionality of concepts is necessary for epistemological reductionism. Only on the basis of the co-extensionality between concepts of different sciences is it possible to deduce law-like generalizations of the special sciences from physical law-like generalizations. We will next argue for the necessity of the co-extensionality between concepts of

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different sciences for homogeneous reductive explanations, given the role of co-extensionality for the deduction of law-like generalizations. First, let us outline the deduction of law-like generalizations of the special sciences from physical law-like generalizations. This means that for instance a biological law-like generalization can be deduced from a physical law-like generalization. Take the biological concepts, “gene that produces yellow blossoms” and “yellow blossoms”. Assume as a simplified but illustrative case that there is a biological law-like generalization which holds between these concepts such that any property token that comes under the concept “gene that produces yellow blossoms” will cause, given favouring circumstances, a property token that comes under the concept “yellow blossoms”. Let us furthermore assume that for each of these two biological concepts there is a co-extensional physical concept, say “molecular configuration of type P1” and “molecular configuration of type P2”, and, in addition to this, these two physical concepts are analogously linked by a physical law-like generalization. Based on this, the truth of the biological law-like generalization about the genes for yellow blossoms and their causal effects of yellow blossoms can be deduced from the truth of the physical law-like generalization couched in terms of the concepts of these molecular configurations. The justification for such a deduction will be examined later in more detail (cf. ‘Nagel’s model of reduction’, this chapter, p. 89). Our point here is the co-extensionality of the concepts serves as a necessary requirement for the deduction of law-like generalizations. It is not possible to deduce a biological law-like generalization from a physical law-like generalization if the biological and physical concepts are not co-extensional. There are two cases that have to be distinguished: On the one hand, it is possible to deduce the truth of the biological law-like generalization in any case in which the application of the physical law-like generalization is true. To put it simply, in any case in which a molecular configuration token of type P1 causes a molecular configuration token of type P2, the application of the biological law-like generalization is true as well. This point is uncontroversial. After all, the truth of any concept of the special sciences supervenes on the truth-value of physical concepts (cf. ‘supervenience of truth-values’, this chapter, p. 79). But, on the other hand, in case the biological and physical concepts in question are not co-extensional, there are truth-makers for the biological concept “gene that produces yellow blossoms” and “yellow blossoms” that do not come under the above mentioned physical concepts. The possibility for such cases is claimed by

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the multiple realization argument that will be examined later on in more detail (cf. ‘argument of multiple realization’, this chapter, p. 117). Thus, in this case, the biological law-like generalization cannot be deduced from the physical law-like generalization, or, to put it more formally, the claim that “all entities coming under P1 that cause an entity to come under P2” does not imply the claim, “all entities coming under B1 cause an entity coming under B2”. Other physical law-like generalizations necessary in order to deduce the truth of the biological law-like generalization. There is, hence, a disjunction of physical law-like generalizations that is necessary and sufficient to deduce the biological law-like generalization. I shall consider this issue later on in more detail (cf. ´critique of the multiple realization argument´, this chapter, p. 133). In any case, we take ontological reductionism for granted, and, in this case, it seems that there is no systematic link with physics that is causally, nomologically, and explanatory complete. To conclude, provided that biological concepts are not co-extensional with physical concepts, the generality of biological law-like generalizations cannot be deduced from a single physical law-like generalization. Second, let us consider the consequence of non-co-extensionality in the context of homogeneous reductive explanations. If there is not a single physical law-like generalization sufficient to deduce the mentioned biological law-like generalization, but a disjunction of physical law-like generalizations must necessarily be posited, it is not possible to provide homogeneous reductive explanations of the causal relation between gene tokens for yellow blossoms and their phenotypic effect of yellow blossoms. The property tokens that all come under one biological law-like generalization come under different physical law-like generalizations. As a result of this, there are different reductive explanations of the causal relation between the gene tokens for yellow blossoms and the yellow blossoms. This means, it is only biology that provides homogeneous explanations of that causal relation – but it is not possible to provide such homogeneous explanations in terms of physics. This is why the special sciences seem to be indispensable from a scientific point of view. This argument will be expanded later on in reference to the multiple realization argument, its critique, and my proposed reductionist strategy (cf. ‘argument of multiple realization’, this chapter, p. 117, ‘critique of the multiple realization argument’, this chapter, p. 133, and ‘epistemological reductionism by means of sub-concepts’, this chapter, p. 157). Finally, let us consider homogeneous reductive explanations in the context of epistemological reductionism in more detail. In general, two

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explanations are co-extensional if they are applicable to the same set of entities in the world. The two explanations have, hence, the same extension. For the sake of the argument, let us assume that the biological concept “gene that produces yellow blossoms” has the same extension as the physical concept “molecular configuration of type P1”, and the biological concept “yellow blossoms” has the same extension as the physical concept “molecular configuration of type P2”. Therefore, any entity in the world that is described as a gene that produces yellow blossoms is a molecular configuration of type P1 and causes yellow blossoms that come under the concept “molecular configuration of type P2”. Only in such cases, the biological property tokens that are homogeneously explained in terms of biology can be homogeneously explained in terms of physics as well. Given such a homogeneous reductive explanation, the biological concepts “gene for yellow blossoms” and “yellow blossoms” and the mentioned law-like generalization can be systematically linked with physics. In such cases, it is obvious that the epistemological reduction of biology to physics is possible. But, on the other hand, such bi-conditional correlations of any concepts of the special sciences with physical concepts suggest the dispensability of the special sciences as I shall argue later on in more detail (cf. ‘what conservative reductionism means’, chapter II, p. 178, and ‘the limits of the sub-concept strategy’, chapter III, p. 181). Let us recap and call this the ‘necessity of co-extensionality for epistemological reductionism’, by which we mean that epistemological reductionism aims to deduce law-like generalizations of the special sciences from physical law-like generalizations in order to provide reductive explanations and to justify the scientific quality of law-like generalizations of the special sciences. This is only possible provided the concepts of different sciences are co-extensional. In this case, the epistemological reduction of the special sciences is unproblematic because the explanations of the special sciences are systematically linked with physics.

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Models for epistemological reductionism ix.

Nagel’s model of reduction24

Nagel’s model of reduction is designed to reduce scientific theories. For instance, it can be applied to reduce genetics to molecular biology. In general, Nagel’s strategy proceeds as follows: in order to reduce a theory T2 to a usually more basic theory T1 one has to deduce the laws of T2 from the laws of T1; and in order to be able to deduce the laws, it is necessary and sufficient to find within T1 concepts that are co-extensional with the concepts that figure in the laws of T2. So-called bridge-principles establish this co-extensionality between concepts of T2 and T1. For instance, assume that genetics is expressed in certain law-like generalizations such that there is a genetic law-like generalization that relates genotype and phenotype.25 To put it simply, the genetic law-like generalization LGen means: “genes cause phenotypes”. In order to deduce this genetic law-like generalization LGen from molecular biology it is necessary and sufficient to find coextensional molecular concepts for the genetic concepts “gene” and “phenotype”. This match of extension will be achieved by means of bridge-principles that correlate the genetic concepts with concepts of molecular biology. Provided that any genetic concept can be systematically correlated with a concept of molecular biology, any genetic law-like generalization can be deduced from molecular biology. Genetics can thus be reduced to molecular biology. In general terms, a systematic correlation of concepts of one theory into co-extensional concepts of another theory is sufficient to deduce lawlike generalizations of the one theory from law-like generalizations of the other theory. According to Nagel, such a deduction of law-like generalizations is sufficient to reduce T2 to T1. Nagel aims to establish the co-extensionality between concepts of different theories by means of bridge-principles. Given the co-extensionality between the concepts of the 24

Cf. Nagel (1961). See part II for a detailed consideration of the reduction of genetics. The examples of laws and concepts of genetics and physics given here are of course oversimplifications. Nonetheless, there is a causal relation between genotype and phenotype that can be considered in a law-like definition of genes (cf. ‘functionally defined concepts’, p. 109, and ‘functional definition of the gene’, chapter V, p. 220), and physics can consider these issues as well (see below). 25

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special sciences and physics, the law-like generalizations of the special sciences can be deduced in the last resort from physical law-like generalizations. Once such a deduction of law-like generalizations is achieved, the special sciences are epistemologically reduced to physics. Whether or not such a deduction of law-like generalizations is sufficient in order to establish epistemological reductionism will be considered in the context of Kim’s model of reduction where I shall compare both model’s of reduction (cf. ‘Kim’s model of reduction’, this chapter, p. 99). In this section, let us focus on the core of this reductionist model in the context of the relationship between the special sciences and physics, examine the status of bridge-principles and recent developments of Nagel’s strategy. First of all, let us consider the core of Nagel’s model of reduction in the context of biology and physics. For the sake of the argument, let us once again imagine a biological law-like generalization LBio that is about two sets of property tokens. For instance, property tokens that come under the biological concept “gene that produces yellow blossoms” cause property tokens that come under another biological concept “yellow blossoms” (“LBio”: “Ceteris paribus, any property token that comes under the concept ‘gene that produces yellow blossoms’ causes a property token that comes under the concept ‘yellow blossoms’”): LBio: Property tokens that come under “gene that produces …” cause property tokens that come under “yellow blossoms” “gene that produces …” (come under concept) 

“yellow blossoms” 

b1x, b1y,…

(come under concept)

b2x, b2y, … (cause)

Taking this as a starting point, we now need auxiliary principles in the form of bridge-principles that establish the co-extensionality of the biological concepts with physical concepts. For instance, we need auxiliary principles in the form of bridge-principles that correlate the biological concepts “gene that produces yellow blossoms” and “yellow blossoms” with co-extensional physical concepts such as “molecular configuration of type P1” and “molecular configuration of type P2”. Taking ontological reductionism for granted, these bridge-principles will not be additional laws of nature because they only correlate concepts that are

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about the same entities. They do not link different property tokens as laws in the sciences. Let us assume the bridge-principle “BP1” that correlates the biological concept “gene that produces yellow blossoms” with the physical concept “molecular configuration of type P1”. Let us also assume another bridge-principle “BP2” that correlates the biological concept “yellow blossoms” with the physical concept “molecular configuration of type P2”. Thus, these are the physical concepts that are correlated with the biological concepts by means of the bridge-principles “BP1” and “BP2” such that there is a co-extensionality between the concepts of the different theories in question: LBio: Property tokens that come under “gene that produces yellow blossoms” cause property tokens that come under “yellow blossoms” “BP1”: any property token that comes under the concept “gene that produces yellow blossoms” comes under the physical concept “molecular configuration of type P1” as well (“B1”  “P1”) “BP2”: any property token that comes under the concept “yellow blossoms” comes under the physical concept “molecular configuration of type P2” as well (“B2”  “P2”) “BP1”: “gene that produces …” (come under concept) 

b1x, b1y, … (come under concept) 

“molecular conf. of type P1”

“BP2”: “yellow blossoms”  (come under concept) b2x, b2y, …  (come under concept) “molecular conf. of type P2”

One may object that there are no physical concepts that are coextensional with biological concepts. After all, physics is generally about atoms and relative simple molecular configurations, but not about genes, cells or organisms. At least, there seem to be no physical concepts of those molecular configurations that are a gene, a cell or an organism. However,

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taking ontological reductionism for granted, any biological property token is identical with a configuration of physical tokens. Therefore, it is in principle possible to describe any biological property token in physical terms. For any configuration of physical property tokens it is possible to construct a physical concept in order to reach the co-extensionality that is necessary for epistemological reductionism.26 Such a constructed concept is embedded in physics that generally considers entities like atoms or electrons and not entities that come under concepts of the special sciences. I shall take such constructed physical concepts as the reduction base for biological concepts and laws in what follows: LPhy: Property tokens that come under “molecular configuration of type P1” cause property tokens that come under “molecular configuration of type P2” “molecular conf. of type P1” (come under concept)



“molecular conf. of type P2 

p1x, p1y, …

(come under concept)

p2x, p2y, … (cause)

In this context, two possibilities present themselves for deducing the biological law-like generalization “LBio” from physics. Either, first, there is already a physical law-like generalization, say “LPhy”, that connects property tokens that come under the physical concept “molecular configuration of type P1” with property tokens that come under the physical concept “molecular configuration of type P2”: “molecular conf. of type P1” 

Physics

26

(concept about a certain mol. conf.) (embedded in / construction out of)

(concepts about atoms, electrons, etc.)

Cf. Hooker (1981, pp. 49-52) who outlines in detail how to construct co-extensional physical concepts in order to reduce concepts, laws, and theories. My consideration of reductionist models bears in mind Hooker’s development of Nagel’s model in what follows.

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In such a case, the biological law-like generalization “LBio” can be directly deduced from the physical law-like generalization “LPhy” because each of the biological concepts can be correlated with the co-extensional physical concepts that figure in the physical law-like generalization “LPhy”. There are auxiliary bridge-principles “BP1” and “BP2” that correlate the biological concepts “gene that produces yellow blossoms” and “yellow blossoms” with the physical concepts “molecular configuration of type P1” and “molecular configuration of type P2” in order to secure their coextensionality. Therefore, by means of these bridge-principles, the biological law-like generalization “LBio” can be deduced from the physical law-like generalization “LPhy”: Deduction of LBio from LPhy: LBio: Property tokens that come under “gene that produces yellow blossoms” cause property tokens that come under “yellow blossoms” (cause)

b1x, b1x, …

b2x, b2y, …

(come under concept) 



“gene that produces …” (“BP1”)

(come under concept)

“yellow blossoms”

↕

↕

(“BP2”)

“molecular conf. of type P1” “molecular conf. of type P2” (come under concept) 



p1x, p1y, …

(come under concept)

p2x, p2y, … (cause)

LPhy: Property tokens that come under “molecular configuration of type P1” cause property tokens that come under “molecular configuration of type P2” Or, secondly, there is no such law-like generalization “LPhy” in physics. This means, there is no such law-like generalization in current

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physics that connects all and only the property tokens that come under the physical concept “molecular configuration of type P1” with all and only the property tokens that come under the physical concept “molecular configuration of type P2”. Since physics is more general than biology, it has no particular interest in just those configurations of physical property tokens that come under biological concepts. As already said, physics is about atoms in general and about relatively simple molecular configurations, but not about molecular configurations that are genes, cells, or organisms in particular. However, since the biological law-like generalization “LBio” is true, the completeness of physics implies the possibility to construct within physics a law-like generalization from which it is possible to deduce the biological law-like generalization. This possibility is derived from the fact that we can construct physical concepts that apply to all and only those configurations of physical property tokens that come under biological concepts. Of course, physics is generally about entities such as atoms and relatively simple molecular configurations and not about entities that are biological property tokens in particular. But it is not possible that a special science such as biology is about causal relations that are beyond physics (cf. ‘completeness of physics’, chapter I, p. 24). As a result of this, any causal relation that comes under a biological law-like generalization can be considered in terms of physics as well. It is possible in principle to construct physical law-like generalizations from which those law-like generalizations can be deduced. This means, we can deduce from the universal physical laws the law-like generalization LPhy that is couched in terms of physical concepts such as “molecular configuration of type P1” and “molecular configuration of type P2”. Provided that the bridge-laws secure the co-extensionality between “gene that produces yellow blossoms” with “molecular configuration of type P1”, and “yellow blossoms” with “molecular configuration of type P2”, we can then deduce the biological law-like generalization LBio from the constructed physical law-like generalization LPhy. Finally, even if “LPhy” does not figure in current physics, it can be constructed as an intermediate step in order to deduce the biological law-like generalization from general laws of physics that do apply to molecular configurations such as molecular configurations of type P1 and of type P2 (gene tokens for yellow blossoms and tokens of yellow blossoms):

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1.

Construction of the law-like generalization “LPhy” by means of construction of the concepts “molecular configuration of type P1” and “molecular configuration of type P2” within physics and the application of general physical laws to the components of the two types of molecular configurations in question.

2.

Deduction of LBio from LPhy via the bridge-principles “BP1” and “BP2”: LBio: Property tokens that come under “gene that produces …” cause property tokens that come under “yellow blossoms”. (cause)

b1x, b1y, …

b2x, b2y, …

(come under concept) 



“gene that produces …” (“BP1”)

“yellow blossoms”

↕

↕

“molecular conf. of type P1”

(come under concept)

(“BP2”)

“molecular conf. of type P2”

(come under concept) 



p1x, p1y, …

(come under concept)

p2x, p2y, … (cause)

LPhy: Property tokens that come under “molecular configuration of type P1” cause property tokens that come under “molecular configuration of type P2” Second, let us consider the logical status of bridge-principles. Bridge-principles have to be bi-conditionals in order to secure the coextensionality of the connected concepts. The argument proceeds as follows: co-extensionality between concepts is necessary for epistemological reductionism (cf. ‘necessity of co-extensionality for epistemological reductionism’, this chapter, p. 85). In order to establish co-extensionality between concepts, a symmetric relation (correlation) of

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the concepts in question is required. It is necessary to exclude cases in which the application of the one of these concepts is true about some entity while the application of the other concept is false about the same entity. Since only a bi-conditional relation between two concepts excludes the mentioned cases, the bridge-principles of Nagel’s model of reduction need the logical status of bi-conditionals. To conclude, only bi-conditional bridge-laws fulfil the requirement to establish co-extensionality between concepts. Let us go into more detail at this point and consider one-way conditionals.27 Contrary to bi-conditionals, one-way conditionals do not suffice to establish co-extensionality. For instance, a one-way conditional linking the biological concept “gene that produces yellow blossoms” with the physical concept “molecular configuration of type P1” (“gene that produces yellow blossoms”  “molecular configuration of type P1”) does not exclude the possibility that the physical concept is true about an entity while the biological concept is false about the same entity. In the same way, a one-way conditional linking the physical concept “molecular configuration of type P1” with the biological concept “gene that produces yellow blossoms” (“molecular configuration of type P1”  “gene that produces yellow blossoms”) does not exclude the possibility that the biological concept is true about an entity while the physical concept is false about the entity in question. Therefore, one-way conditionals are not sufficient in order to establish the necessary co-extensionality between concepts. However, I should note that the crucial point of epistemological reductionism is to establish a conditional that goes from biological concepts to physical concepts (cf. ‘argument of multiple realization’, this chapter, p. 117). Given the supervenience of the truth-values of the concepts of the special sciences (cf. ‘supervenience of truth-values’, this chapter, p. 79), one-way conditionals that go from physical concepts to biological concepts are already established by means of this supervenience relation. A true application of a physical concept about an entity determines which biological concept (if any) is true about the entity in question. Thus, together with a one-way conditional that goes from biological concepts to physical concepts, the required bi-conditional form would be established. 27

Cf. Nagel (1961, p. 355, note 5) where he maintains that the bi-conditional form of the bridge-principles is not necessary in order to deduce laws and reduce theories. However, as I shall argue, bi-conditionals are required in order to establish the necessary co-extensionality of concepts of different theories.

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Keeping this in mind, let us focus on the argument for the biconditional bridge-principles. Since bridge-principles correlate physical concepts with concepts of other sciences, bridge-principles cannot be expressed only in physical terms. They are principles that connect concepts of different sciences. As mentioned above, one can construct concepts within physics of which it is presumed that they are coextensional with biological concepts. If this presumption is confirmed in concrete cases, we have gained a bridge-principle. This bridge-principle is law-like and thus nomological necessary. The argument for this nomological necessity proceeds as follows: first assume a biological law-like generalization “LBio” that connects those property tokens that come under the biological concepts “gene that produces yellow blossoms” and “yellow blossoms”. Second, let us assume that it is possible to construct co-extensional physical concepts. The constructed physical concept “molecular configuration of type P1” is coextensional with the biological concept “gene that produces yellow blossoms”, and “molecular configuration of type P2” is co-extensional with “yellow blossoms”. Third, since the completeness of physics holds, the relation between “molecular configuration of type P1” and “molecular configuration of type P2” has to be law-like as well. If causation implies laws and if the causal relation in question is law-like as described in terms of “gene that produces yellow blossoms” and “yellow blossoms”, then the completeness of physics entails that there also is a law-like physical description of the cause and the effect in question. That is to say, the relation between the physical concepts “molecular configuration of type P1” and “molecular configuration of type P2” is law-like as well. This, finally, suggests that the bridge-principle that correlates the biological concepts with the constructed physical concepts is law-like, too. To the contrary, let us suppose that the co-extensionality between the biological and the constructed physical concepts were only accidental. As a result of this, the completeness of physics would be false. In such a case, the biological concept “gene that produces yellow blossoms” together with the law-like generalization that connects that concept with the concept “yellow blossoms” would provide a completely sufficient causal explanation of the yellow blossoms. But, since we take ontological reductionism for granted, the constructed physical concept “molecular configuration of type P1” together with the physical law-like generalization would be incomplete in order to capture this causal relation. There would be something about that causal relation between gene tokens for yellow blossoms and yellow blossoms that would not be captured in

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terms of physics. Consequently, ontological reductionism would be false. To put it another way, the relata of the biological law-like generalization are not nomologically connected with the relata that figure in that physical law-like generalization. This is why it is not possible that biological concepts that figure in biological law-like generalizations are coextensional with physical concepts that figure in law-like generalizations, but that this co-extensionality is accidental. Therefore, bridge-principles are law-like. In relation to this conclusion, let us consider the reason that biconditional bridge-principles are not simply definitions. Nagel’s model does not reduce the meaning of concepts. There are three points I would like to mention: first, concepts of different sciences generally differ in meaning. For instance, the biological concept “gene that produces yellow” possesses a different meaning compared to its co-extensional physical concept about a certain molecular configuration. This difference in meaning holds for probably any case where concepts of the special sciences are co-extensional with physical concepts. Second, it is not the aim of epistemological reductionism to reduce the meaning of concepts. Epistemological reductionism does not aim at providing a physical definition of concepts of the special sciences, but rather to establish coextensionality between concepts of different sciences in order to deduce the law-like generalizations of the special sciences from physical law-like generalization in such a way that the special sciences will be systematically embedded in physics. But, as our third point, let us imagine the consequence if there were a definition of, for instance, biological concepts by means of physical concepts. This would entail the possibility, at the very least, of fully eliminating biological concepts: biological concepts would simply be replaced by physical concepts. I shall consider the topic of elimination later on in the context of the so-called new wave reductionism (cf. ‘critique of the multiple realization argument’, this chapter, p. 133). Let us call this ‘Nagel’s model of reduction’. In order to reduce the special sciences, it is necessary that the bridge-principles are biconditionals in order to establish a co-extensionality between concepts of different theories. One-way conditionals are not sufficient in order to establish this co-extensionality between the concepts of different theories. Provided that the bridge-principles secure the required co-extensionality, Nagel’s model of reduction achieves the embedding of the law-like generalizations of the special sciences in physics. According to him and recent developments of his model, this embedding and deduction of law-

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like generalizations of the special sciences from physical law-like generalizations amounts to the reduction of the special sciences. I shall note that the physical concepts and the physical law-like generalizations that figure in this model of reduction are constructed ones that do not appear in current physics, but that can nonetheless constructed within physics. Such a construction can be traced back to Hooker28, and will be taken up in the following section and used later on in relating to our consideration of the new wave reductionism (cf. ‘critique of the multiple realization argument’, this chapter, p. 133).

x.

Kim’s model of reduction

Nagel’s model of reduction in 1961 began a still ongoing debate on reductionist models in the philosophy of science and the philosophy of mind. There are several main strands I would like to mention here to provide us with a context for discussing Kim’s approach in more detail. First of all, there are the modifications and developments that are more or less in the tradition of Nagel’s model, especially the modifications of Kenneth Schaffner29, and the developments of Clifford Hooker30 that I have already mentioned in the previous section. Based on this, John Bickle31 developed an eliminativist strategy with respect to the special sciences – the so-called ‘new wave reductionism’ about which we have more to say later on (cf. ‘critique of the multiple realization argument’, this chapter, p. 133), noting here merely that it says that the theories of the special sciences can be replaced by constructed physical theories that match the reference objects of the special science theories in question. In the context of eliminativist reductionism, let us mention a more extreme eliminativist position that is associated with Paul and Patricia Churchland.32 They mainly claim that there really are no property tokens of the special sciences. There is nothing but physical property tokens in the world, and the only reason for the special sciences, that are, by the way, provisional, is their pragmatic value. Going beyond John Bickle’s position, the Churchlands can be read as claiming that the concepts of the special sciences do not have any reference object in the world. 28

Hooker (1981). Schaffner (especially 1967, 1969a, and 1974). 30 Hooker (especially 1981). 31 Bickle (1998, especially ch. 2, and 2003). 32 Cf. especially Churchland (1981). 29

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Contrary to this, let us briefly note another position – the so-called ‘a priori physicalism’ of, most influentially, Frank Jackson and David Chalmers, which holds that, if we had a complete description of the distribution of the physical property tokens, an a priori deduction of any description in terms of the special sciences would be in principle possible.33 Although the truth-value of any description of the special sciences supervenes on appropriate physical descriptions (cf. ‘supervenience of truth-values’, this chapter, p. 79), we conceive of the reductionist approach to the special sciences as an empirical issue.34 Furthermore, we take for granted that the property tokens of the special sciences exist and the special sciences are true and indispensable from a scientific point of view. Kim’s model of reduction is designed to explain what is essential to properties of the special sciences. We will give a short overview of his strategy, here: first, he functionally defines any concept of the special sciences in terms of a causal task. On this basis, secondly, it is possible to discover so-called physical realizers of that causal task. Each configuration of physical property tokens that fulfils the causal task in question will be called a ‘realizer’ of the functionally defined concept in question. Finally, since each realizer comes under a (constructed) physical concept, it is possible to explain in physical terms why the causal task is fulfilled in the case in question. Therefore, physics explains why there are entities that fulfil the causal tasks that characterize the functionally defined concepts of the special sciences. Furthermore, Kim’s model of reduction may provide a strategy of epistemological reductionism. Under the condition that the physical realizers of the causal task (that defines a concept of the special sciences) will also come under one (constructed) physical concept, the coextensionality between concepts is established: the functionally defined concept of the special science is co-extensional with the (constructed) physical concept of the realizers. In this context, Kim’s model implicitly provides reductive explanations. In this case, this model fulfils the necessary condition for an epistemological reductionism (cf. ‘necessity of co-extensionality for epistemological reductionism’, this chapter, p. 85). In addition to this, in this case Kim’s model suffices to provide homogeneous physical explanations: since the correlation between the 33

Jackson (1998, especially ch. 2) and Chalmers & Jackson (2001). Cf. Laurence & Margolis (2003), Marras (2005), and Melnyk (2003, pp. 254-255) who criticize Jackson’s claim for an a priori conceptual analysis to support tokenidentity and to deduce, a priori, the concepts of the special sciences from physics. 34

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concepts of the special sciences with (constructed) physical concepts is based on the causal task in question and its physical realizers, homogeneous causal explanations will be provided. Keep in mind that physics can explain the causal task in a complete manner by the ‘completeness of physics’ argument (chapter I, p. 24), while the special sciences can explain the causal task only, as shown in chapter one (p. 29), in an incomplete manner. Let us, then, examine Kim’s explanatory strategy with its three subsequent steps, and consider this strategy in the context of epistemological reductionism and the model of Nagel. The starting point of Kim’s strategy is a functionalization of property types of the special sciences35. This assigns a functional characterization to each concept of a special science. A functional definition of a concept is a definition by means of its causal task. A ‘causal task’ is a causal relation. In the following, I shall take the term ‘concept of a special science’ as an abbreviation of ‘functionally defined concept’, and ‘biological concept’ as ‘functionally defined biological concept’. For instance, the causal task that the biological concept “gene that produces yellow blossoms” carries out is to cause yellow blossoms (cf. ‘functionally defined concepts’, this chapter, p. 109). This means, any property token that causes yellow blossoms comes under the concept “gene that produces yellow blossoms”: Functionalization of a biological concept, for instance “gene that produces yellow blossoms”: “gene that produces …” “yellow blossoms” (come under concept) 

b1x, b1y, …



(come under concept)

b2x, b2y, …

(causal task that defines the gene concept)

The second step of Kim’s strategy is concerned with physical realizers and the process of discovering them. Just to bear in mind, a realizer is a configuration of physical property tokens that fulfils a certain causal task – the causal task that defines a certain concept of the special sciences. Even more precise, a configuration of physical property tokens is

35

Cf. Kim (2005, pp. 101-102).

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a realizer in virtue of fulfilling the causal task that defines the concept in question. However, here I would like to add two points. The first point concerns an argument to the effect that there always is a physical realizer. Given that the argument for ontological reductionism is cogent (cf. ‘token-identity qua causal efficacy and completeness’, chapter I, p. 51), any biological property token is identical with a molecular configuration. Since this argument is a causal argument, it follows that the molecular configuration in question is the realizer we are seeking for in Kim’s strategy. For instance, a biological property token that comes under the concept “gene that produces yellow blossoms” is identical with a molecular configuration that comes under a physical concept, say once again “molecular configuration of type P1”. Furthermore, the biological property token comes under the concept “gene that produces yellow blossoms” because it fulfils the causal task that defines this concept. Therefore, the molecular configuration in question is a realizer of the gene that produces yellow blossoms. After all, the molecular configuration is identical with the gene token in question. Secondly, let us consider a general strategy to discover a realizer.36 Even if this strategy is quite similar to the argument that there always is a physical realizer, it constitutes a strategy that emphasizes the essential issue of any discovery of realizers. Let us once again compare biology with physics. The starting point is the functional definition of a biological concept (cf. ‘functionally defined concepts’, this chapter, p. 109). For instance, a property token comes under the biological concept “gene that produces yellow blossoms” if it causes a property token that comes under the biological concept “yellow blossoms”. In general, a property token comes under a certain functionally defined concept if it causes a property token that comes under a specific other concept. This causal relation is essential for the functional definition of the gene concept. However, the biological property token that comes under the concept “yellow blossoms” is identical with a molecular configuration. Let us now assume that this molecular configuration of the yellow blossoms is known. This molecular configuration has a certain physical cause. That physical cause fulfils the task of causing the yellow blossoms. It is therefore the realizer of the gene in question. Of course, much empirical research may be needed in order to find out which molecular configuration has the effect that defines the causal task in question. The point of this strategy is to find a specific realizer using only the criterion of the role that the entity in question fulfils. However, I would like to emphasize the following point: since it is 36

This strategy can be traced back to Lewis (1970, pp. 81-82).

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a causal relation that defines the biological concepts, this strategy to discover realizers does not differ essentially from the argument that there always is a realizer of a biological property token (previous paragraph). The point is that the term ‘realizer’ is essentially linked to the causal task that defines a concept of the special sciences. To put it simply, it is just a specific causal relation that makes a molecular configuration a realizer. Any other causal relations in which the molecular configuration in question stands are redundant at this stage of the argument. I shall reconsider this point in what follows in more detail. Discovery of the realizers of a functionally defined biological concept, for instance “gene that produces yellow blossoms”: “gene that produces …” “yellow blossoms” (come under concept) 

Realizers:



p1x, p1y, …

(come under concept)

p1x, p1y, …

(causal task that defines the gene concept) (come under concept) 

concept about the realizers 

(embedded in / constructed out of)

Physics The third step of Kim’s strategy concerns the explanatory ascent from physics to the special sciences. I take an explanation to be a causal explanation (cf. ‘concept of explanation’, this chapter, p. 71). For that reason, an explanatory ascent from physics to the special sciences proceeds as follows: physics explains the causal relations that define a certain functionally defined concept of the special sciences. To put it another way, physics explains by means of the realizers, say of the “molecular configuration of type P”, the causal task that defines the biological concept “gene of type B”. In order to explain this causal task, one must take into account the components of the realizers. The realizers are composed of physical systems. To put it simply, there are atoms of certain types that makes up to the molecular configuration. Each of these

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components can be causally described in terms of physics. After all, this is what physicists generally are concerned with. Through this step from the molecular configuration in question (realizer) to the causal description of each component, it is possible to provide a detailed causal description of the realizer. Consequently, the causal task that is fulfilled by the realizer can be described in a complex way – by means of the causal description of each of the physical components of the realizer in question. Let us reconsider this step to the framework of explanations. Again, we take an explanation to function as an application of concepts that are embedded in a theory. Since any property token of the special sciences is identical with a configuration of physical property tokens, any biological property token, such as a gene token, comes under a (constructed) physical concept. Thus, for instance, the realizer of a gene that produces yellow blossoms comes under a constructed physical concept such as “molecular configuration of type P1”. It follows from the completeness of physics that a physical explanation of biological property tokens is both complete, and obviously more detailed than a biological explanation. This means, the physical explanation of the molecular configuration of type P1 by means of an explanation of its physical components is complete. The explanation how a realizer fulfils the causal task in question is articulated in completely physical terms. This is a reductive explanation of the gene token in question (cf. ‘concept of explanation’, this chapter, p. 71). Physics explains, by means of constructed concepts, how a property token fulfils the causal task that characterizes the functionally defined concept in question. Though, physics is complete relative to the special sciences, and physics is in principle able to provide the most detailed explanation of any property token the aim of epistemological reductionism is not to require that one should always give as detailed an explanation as possible. Rather the aim of epistemological reduction is to explain in physical terms what is essential to a biological property token. This is why a physical explanation should focus on the causal tasks that define biological concepts. It is not necessary to explain details of a molecular configuration beyond those fulfilling the causal task that makes a molecular configuration a realizer of a biological property. Let us consider this point in more detail. A gene token that causes yellow blossoms has, from a physical point of view, more causal effects than just the one to cause yellow blossoms. There are for instance interactions with other molecular configurations that are not essential to

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causing of yellow blossoms. There might be a resistance against ultraviolet light that is not taken into account in the concept “gene that produces yellow blossoms”. Whenever we focus on realizers, we focus on a characteristic causal relation – and not on any causal relation – of the molecular configuration in question. This means that the physical explanation of the realizer is the (essential) explanation of a biological property token we are seeking for in a reductionist approach. This is why one focuses on the realizers in order to provide reductive explanations that are the aim of epistemological reductionism. Such a reductive explanations are constructed for philosophical purpose. After all, physics generally considers atoms or relatively simple molecular configurations, and not the causal task that defines a molecular configuration as a realizer of a gene in particular. But since the causal argument for ontological reductionism, as well as the principle of the completeness of physics are true, it is always possible to construct such physical explanations of realizers. On this basis, it may be possible to reduce concepts of the special sciences as well. Let us once again consider the biological concept “gene that produces yellow blossoms”. Provided that the realizers of this gene concept come under one (constructed) physical concept, it is possible to correlate the biological concept “gene that produces yellow blossoms” with an appropriate (constructed) physical concept such as “molecular configuration of type P1”. As a result of this, it is possible to explain any gene token for yellow blossoms homogeneously by means of the physical concept “molecular configuration of type P1” (embedded in a physical theory). This means explaining the causal task of any gene token for yellow blossoms by the same physical concepts. And it is the homogeneous physical explanation of property tokens that come under o n e concept of the special sciences which is our goal in epistemological reductionism:

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Reductive explanation of a functionally defined biological concept, for instance “gene that produces yellow blossoms”: “gene that produces …”

“yellow blossoms”

(come under concept) 

Realizers:



p1x, p1y, …

(come under concept)

p2x, p2y, …

(causal task that defines the gene concept) (come under concept) 

“molecular configuration of type P1” 

(embedded in / constructed out of)

Physics Reductive explanation of the genes for yellow blossoms by means of “molecular configuration of type P1”: - focuses on the causal task that defines the gene that produces yellow blossoms - is embedded in physics which provides complete causal explanations of the components of the molecular configuration of type P1 Against this background, let us make several points about Kim’s reductionist model in connection to epistemological reductionism and in comparison to Nagel’s model. My claim is that there is no essential difference between Nagel’s and Kim’s strategies for epistemological reductionism. The main issue of epistemological reductionism is to establish the co-extensionality between concepts of different sciences. Nagel’s model establishes this co-extensionality by means of bridgeprinciples, while Kim’s model establish this co-extensionality by means of functionalization and discovery of realizers. Given that, for instance, the functionally defined biological concept “gene that produces yellow blossoms” is co-extensional with the (constructed) physical concept of the realizers of the gene type in question, this correlation of the concepts is nomological. Any gene token is identical with a certain molecular configuration. The configuration is, by definition, a realizer of the gene

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type in question (comes under the gene concept in question). In addition to this, the realizers come under one (constructed) physical concept. I should mention that we nonetheless only assume that the realizers come under one (constructed) physical concept. In this context, Kim’s model also requires bridge-principles in order to correlate nomologically the concepts of the special sciences with physical concepts. I shall reconsider this issue later on (cf. ‘argument of multiple realization’, this chapter, p. 117, and ‘consequences for Kim’s model’, this chapter, p. 123). However, Nagel’s model is based on an equivalent assumption. In his model, provided that concepts of different sciences are co-extensional, the correlation of these concepts is nomological. In this context, I shall conclude that Kim’s and Nagel’s model of reduction do not differ essentially. The strategies how to discover co-extensionality may differ, but in the last resort, the two strategies try to establish nomological correlation between concepts of different sciences. Kim’s model establishes some kind of bridge-principles, although his strategy works even if it is only possible to establish one-way conditionals.37 We shall leave that issue aside at this point because, firstly, co-extensionality is necessary for epistemological reductionism (cf. ‘necessity of coextensionality for epistemological reductionism’, this chapter, p. 85), and secondly, we will be reconsidering Kim’s model after examining the famous multiple realization argument later (cf. ‘consequences for Kim’s model’, this chapter, p. 123). Here, we want to point out a clear advantage Kim’s model of reduction has over Nagel’s. Kim’s model implicitly provides reductive explanations because his strategy is based on the causal task that defines concepts of the special sciences and the physical explanation of the realizers of such causal tasks (cf. ‘concept of explanation’, this chapter, p.71). To put it another way, Kim’s model provides causal explanations of what defines concepts of the special sciences. Contrary to this, Nagel’s model does not imply such reductive explanations. Bridge-principles provide the necessary conditions for homogeneous physical explanations, but bridge-principles are not explanatory per se. A case in point is the following: by means of Kim’s model of reduction, it can be explained why certain entities come under the functionally defined biological concept “gene that produces yellow blossoms”. His strategy explains the causation of yellow blossoms by means of the physical concepts (embedded in a physical theory) by which we group the appropriate realizers. This is a reductive explanation of biological property tokens such as gene tokens. 37

Cf. Marras (2002).

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Contrary to this, Nagel’s model provides a different kind of explanation. It provides explanation by means of deduction of explanatory concepts, but these concepts are neither necessarily functionally defined concepts, nor does this deduction provide causal explanations. Having grounded a correlation of, for instance, “gene that produces yellow blossoms” with “molecular configuration of type P1”, it is possible to deduce a physical explanation. After all, the physical concept “molecular configuration of type P1” is embedded in a theory of physics. Therefore, it is an explanatory concept. This explanatory concept can be applied to each property token that comes under the concept “gene that produces yellow blossoms”. However, this deduction of physical explanations does not necessarily imply a causal/reductive explanation accounting for why a certain entity comes under the concept “gene that produces yellow blossoms”. Finally, let us consider so-called cross-categorical classifications as an argument against epistemological reductionism. Cross-categorical classifications mean that entities that come under a realizer concept do not always come under the functionally defined concept. It claims that molecular configurations of type P1 are not always genes for yellow blossoms. It is possible that such molecular configurations are not genes at all. Therefore, it is not possible to establish co-extensional correlations between concepts of different sciences in order to provide epistemological reductionism. However, I shall exclude such cross-categorical classifications for the following reason: taking ontological reductionism for granted, cross-categorical classifications only indicate that the choice of physical realizer was too narrow. The molecular configuration with which a property token of the special sciences is identical is always a sufficient condition for the occurrence of the property token in question. After all, a physical duplicate of a gene token for yellow blossoms is a gene token for yellow blossoms. This means, given normal conditions and a certain realizer of a gene token for yellow blossoms, the gene token for yellow blossoms occurs. Cross-categorical classifications are excluded because a realizer is understood as the molecular configuration that is identical with the property token of the special science in question. Assuming that a gene token for yellow blossoms fails to occur given a certain molecular configuration, then either the environmental conditions are not right, or the molecular configuration is not the molecular configuration with which the gene token for yellow blossoms is identical. Again, ‘Kim’s model of reduction’ contains three main steps. First of all, any concept of the special sciences is functionally defined by a

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causal task. On this basis, secondly, it is possible to discover so-called physical realizers of that causal task. Finally, each realizer comes under a (constructed) physical concept, and therefore, it is possible to provide reductive explanations. Kim’s model has the advantage over Nagel’s that it explains why there are entities in the world that come under functionally defined concepts of the special sciences. Thus, our next task is to look more closely at the functionalization of concepts of the special sciences.

xi.

Functionally defined concepts

Entities can be described by functionally defined concepts. To describe the concept of a given entity by its characteristic causes and effects is to define the corresponding concept functionally. The concept is about characteristic causes and effects of the corresponding entity. Let us consider characteristic causes, characteristic effects, and functionally defined concepts in more detail. First, let us consider characteristic causes. The term ‘characteristic cause’ signifies a cause that comes under a certain concept or set of concepts. Let us suppose that each property token that comes under a certain concept, say “B1”, is usually caused by a property token that comes under another concept, say “B0”. Thus, property tokens of B0 are the characteristic causes of property tokens of “B1”. This causation of property tokens of B1 by property tokens of B0 is a criterion to formulate the concept about B1 – a concept about property tokens that have characteristic causes. The property token corresponding to concept “B1” is based on the causation by a property token that comes under the concept “B0”. For instance, that property token of a flower possessing a gene of a certain type (B1) is characteristically caused by the sexual reproduction / the genetic combination of genes of its parents (B0). Leaving aside once again the biological details at this point, there is a causal connection from the genotype of the parents to the genotype of the offspring:

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Characteristic causes of property tokens that come under the biological concept “B1”: “B0” (come under concept) 

b0x, b0y, …

“B1” 

(come under concept)

b1x, b1y, …

(characteristic causes of)

Second, there are characteristic effects. This signifies an effect that comes under a certain concept or set of concepts. Let us suppose that each property token that comes under a certain concept, say “B1”, usually causes a property token that comes under another concept, say “B2”. Thus, property tokens of B2 are the characteristic effects of property tokens of B1. This causation of property tokens of B2 by property tokens of B1 allow us to formulate the concept “B1” – a concept about property tokens that have characteristic effects. To be a property token of B1 means to cause a property token of B2. For instance, to possess a gene of a certain type characteristically causes yellow blossoms. Leaving aside the collateral biological details, there is a causal chain running from genes to yellow blossoms. Say, there is a gene that causes characteristically yellow blossoms. The yellow blossoms are the characteristic effects of genes that come under the concept “B1”: Characteristic effects of property tokens that come under the biological concept “B2”: “B1” (come under concept) 

b1x, b1y, …

“B2” 

(come under concept)

b2x, b2y, … (characteristic effects)

Third, let us consider characteristic causes and effects in general. Since in philosophy it is more usual to define a functional concept about property tokens by their characteristic effects, I shall adopt this position in what follows. Any example of a functionally defined concept about

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property tokens will be about their characteristic effects. I shall cover the debate about biological functions in the second part of this work (cf. ‘functional definition of the gene’, chapter V, p. 220). In this chapter, I shall take genes to be defined by their phenotypic effects such as yellow blossoms. Certainly, the genes of a certain organism are caused by the genotype of the parents of that organism. However, this implication is not explicit in the concept “gene that produces yellow blossoms”. Finally, let us consider functionally defined concepts in general. The term ´characteristic´ signifies salient causes and effects. In simple cases, like in the example of genes that cause yellow blossoms, there are genes that are defined by their effects of yellow blossoms. To put it in general terms, there is a link between two concepts – one concept for the genes linked to their characteristic effects, which comes under another single concept, that of yellow blossoms. Here we need four additional points to make. First, property tokens that come under a functionally defined concept usually have characteristic effects that come under more than one concept. For instance, the genes that cause yellow blossoms may also be (with or without other genes or cellular components) causally efficacious for other phenotypic effects. Most single genes have multiple effects – this is the socalled pleiotropy of genes (Greek ‘pleion’, more). Therefore, the functional definition of a certain type of gene may take into account several characteristic effects. To put in general terms, a functional definition is an open list. Such a list generally is organized around only the most relevant (and known) characteristic effects. Second, it is not necessary to formulate a complete list, a complete functional definition. A functional definition aims to distinguish a set of property tokens from another set of property tokens. As soon as two sets of property tokens are sufficiently separated due to two different sets of characteristic effects, the two functional definitions may be sufficiently specific. For instance, as long as the genes for yellow blossoms are sufficiently distinguished from genes for red blossoms, one may argue that the concept about the genes for yellow blossoms is sufficiently specific. After all, concepts bring out what entities have in common and what distinguishes them from one another (cf. ´concept of property types´, this chapter, p. 65). Of course, as mentioned above, a functional definition is open for more details and precision. Third, one may consider in a functional definition not only the direct effects, but furthermore effects that are brought about by the characteristic effects in question. For instance, one may functionally define genes not

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only by means of their direct phenotypic effects like colour or shape of blossoms, but furthermore by means of the functionality of the colour or shape of the blossoms. Given a certain environment, yellow blossoms may attract certain insects. This can be taken into account in the functional definition of the gene. We will formulate more detailed functionally defined concepts later on in more detail (cf. ‘implication of detectability’, this chapter, p. 148). Finally, a functional definition is formulated in terms of dispositions to bring about certain effects.38 The argument for this coincidence is based on the argument for ontological reductionism and the truth of dispositional talk about entities. Suppose for instance that there are normal environmental conditions for a gene token to produce yellow blossoms. Let us assume that there are enough sun, water and nutrition at springtime such that the gene token in question actually causes yellow blossoms. This is reason enough for this gene token to come under the functionally defined concept “gene that produces yellow blossoms”. To put it another way, there is the molecular configuration of type P1 that realizes this gene that produces yellow blossoms in the flower in question. Contrary to this, let us assume unfavourable weather in springtime or even more illustrative some snowy winter. In addition to this, let us consider the same flower token still alive – but of course without the yellow blossoms. In such a case, the dispositional talk about the flower seems to be true. The flower possesses the disposition to bring out yellow blossoms. If we now acknowledge that this dispositional talk is made true by the molecular configuration of type P1, this is reason enough to take a functional definition as co-extensional with a dispositional definition. To conclude, whenever a biological system possesses a molecular configuration of type P1, the system in question possesses the gene that produces yellow blossoms, which is simply a shorter way of saying it possesses the disposition to cause yellow blossoms under normal environmental conditions. We will term this ‘functionally defined concepts’, which refers to the identity between describing entities in terms of their causes and effects defining the corresponding concept functionally. The concept is about causes and effects of the corresponding entities. However, it is more usual in philosophy of science to define a functional concept by means of the characteristic effects of the property tokens in question. In this context, a 38

Cf. Prior, Pargetter, Jackson (1982) and Mumford (1998, chapter 9) for the link between functional and dispositional concepts. Cf. also Heil (2003, chapter 11) who argues for the identity of a disposition with its categorical basis.

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functional definition is a definition in terms of dispositions to bring about certain effects. I shall use the term ‘functionally defined concept’ only for concepts of the special sciences and note that the constructed physical concepts that are supposed to be co-extensional with the functional concepts are defined by composition (cf. ‘Kim’s model of reduction’, this chapter, p. 99). Hence, we have a contrast between functional concepts of the special sciences, and constructed physical concepts about the realizers that are defined by physical composition.

xii. Universality of functionally defined concepts Any concept of the special sciences can be functionally defined. For instance, any biological concept can be functionally defined. In this section, we will examine the underlying argument for this, and its consequences. First, any difference between property tokens leads to a causal difference (cf. ‘property discrimination by causal difference’, chapter I, p.41). Thus, whenever two property tokens are distinguished by two different concepts (of one science), there is a causal difference between the property tokens in question as well. Second, let us consider the consequence of causal differences. Any causal difference enables us to establish an appropriate functional definition. It is possible to reformulate the two appropriate concepts so that they are determined by the causal difference in question. For instance, genes that differ in their effects can be considered by different functionally defined concepts. Whenever there is a causal difference, this enables us to distinguish the property tokens by different functionally defined concepts. Third, let us consider the relationship between functionally defined concepts of the special sciences and physical concepts. There is no conceptual distinction in the special sciences without an appropriate distinction in physics. Every criterion used to distinguish property tokens implies a causal difference (first point). Every causal distinction can be sorted by means of a functional definition (second point). However, every functional difference that is captured by concepts of the special sciences can be considered by physical concepts as well insofar as (a) physics is causally, nomologically, and explanatory complete, (b), the truth-value of any concept of the special sciences supervenes on the truth-value of physical concepts.

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Let us bear in mind that the constructed physical concepts that capture the realizers of a functional concept of the special sciences are usually defined by composition. The constructed physical concepts about the realizers of, for instance, genes of a certain type, are usually defined in terms of composition. The constructed physical concept, say, “P1” is about molecular configurations that are identical or similar in their composition. There are two ways of arguing for this difference between concepts of the special sciences (which I shall take to be functionally defined) and physical constructed concepts about realizers that are defined by composition. The first argument is that a functional definition of physical concepts about realizers would be (almost) indistinguishable from the coextensional functionally defined concepts in terms of the special sciences. For instance, the functionally defined concept “gene that produces yellow blossoms” would be very similar to the constructed physical concept “molecular configuration of type P1” provided that the latter concept could be functionally defined as well. Such a functionally defined concept about molecular configurations of type P1 would be extremely close to the biological concept about “gene that produces yellow blossoms” because it would be about the causal task of the same set of entities that are generally considered only from a biological point of view. Since such a physical concept would not be a concept for configurations, I shall leave this point aside in this chapter. The second argument is based on the concept of a function and the difference between causal and reductive explanations (cf. ‘concept of explanations’, this chapter, p. 71). A functionally defined concept which groups together certain property tokens causally explains the existence of the effects of the property token in question. However, this causal task is not reductively explained by the functionally defined concept per se. The concept of a gene token for yellow blossoms causally explains the occurrence of yellow blossoms, but it is the physical description of the composition of the realizer that provides a reductive explanation of this causal task. Under the assumption that the molecular configuration of type P1 would be functionally defined, it would not be possible to provide a reductive explanation of the causal task of the gene that produces yellow blossoms. Of course, it would be a more detailed causal explanation, but there is a conceptual difference between a functionally defined concept and a concept that is defined in terms of a composition. A reductive explanation can only be provided in connection with a concept that is defined in terms of composition. In addition to this, a function

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conceptually requires realizers such that a functionally defined molecular configuration of type P1 would require realizers as well. Since we take configurations of physical property tokens as the fundamental realizers of any functionally defined property in the world, at some point we must consider the molecular configurations in terms of concepts that are defined by composition. Nonetheless, the constituents of such configurations, atoms or electrons for instance, are per se causally defined, thus functional properties. In this context, let us bear in mind that a functional definition of the molecular configurations of type P1 is a biological concept. Therefore, we should focus on a concept about these configurations in terms of composition. After all, this is all we need in order to consider strategies of epistemological reductionism in this chapter. Finally, let us consider differences that are not captured by a functional definition. Suppose there were a conceptual distinction in terms of the special sciences that could not be considered by a causal, and hence, functional distinction. Thus, there were no functionally defined concepts that could capture these differences. This is possible but these differences are then causally redundant. The differences are about epiphenomena that are redundant with respect to law-like generalizations and causal explanations By redundancy of epiphenomena, we can ignore this possibility: Different concepts and reductive explanation: Functionally defined concept: (defined by a causal task)

“gene that produces yellow blossoms” (to produce yellow blossoms)

Concept of a realizer:

“mol. conf. of type P1y”

(defined by composition)

(composition of type P1y)

Concept of a physical system:

“electron”

(causal definition)

(to attract positive charges)

Reductive explanation of the causal task of a functionally defined concept by means of a concept of realizer. In this context, a causal task requires a realizer while a causal definition, because it is more general, does not. The concept of realizer takes into account the causal interaction of the fundamental physical systems that are the components of the relevant realizer configuration so that we can explain why the configuration fulfils the causal task in question.

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To sum up: let us call this ‘universality of functionally defined concepts’. Any causally efficacious property token out there in the world can be captured by a functionally defined concept. In addition to this, for any causal difference that is considered in terms of the special sciences, there is a proper distinction in terms of physics as well. It is not possible that the special sciences can take into account causal differences unknown to physics. However, only concepts of the special sciences are generally considered as functionally defined ones while the constructed physical concepts about types of realizers are necessarily defined by composition in order to provide reductive explanations.

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An argument against epistemological reductionism xiii. Argument of multiple realization The multiple realization argument is directed against epistemological reductionism.39 It is an argument for the possibility that co-extensional concepts of different sciences are unattainable. But the co-extensionality of concepts (of different sciences) is necessary for epistemological reductionism. This is why the multiple realization argument speaks against epistemological reductionism. Let us regard the argument in terms of explanations and not in terms of law-like generalizations, although it was originally formulated in relation to laws. I shall focus mainly on explanations because the relationship between laws and explanations has already been outlined in previous sections. The consequences of the multiple realization argument amount to the impossibility to provide homogeneous reductive explanations (cf. ‘concept of explanation’, this chapter, p. 71, and ‘necessity of co-extensionality for epistemological reductionism’, this chapter, p. 85). The context of law-like generalizations will be considered in the context of Nagel’s model of reduction subsequent to this section (cf. ‘consequence for Nagel’s model’, this chapter, p. 120). First, how does the multiple realization argument work? Let us assume that there are property tokens that come under one functionally defined concept of the special sciences. However, these property tokens may be physically different. This means, they are of a different physical composition. For that reason, the property tokens come under different physical concepts. The argument claims that there are physical differences possible that do not exclude that the property tokens come under the same concept from the point of view of the special sciences. For instance, imagine property tokens that come under a biological functionally defined concept such as “gene that produces yellow blossoms”. There are several gene tokens. Provided that the argument for ontological reductionism is true, each of these property tokens is identical with a molecular configuration. However, this does not imply that there are no physical differences between the gene tokens. Indeed, as I shall outline later on in 39

Cf. Putnam (1975) and Fodor (1974, pp. 97-115, and 1997) who generalized Putnam’s argument in order to argue against the reduction of the special sciences to physics.

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more detail, there are physical differences possible between these molecular configurations.40 For that reason, they come under different physical concepts, say “molecular configuration of type P1x” and “molecular configuration of type P1y”. These physical differences do not prevent being grouped under the single biological concept “gene that produces yellow blossoms”: Multiple realization of a biological type, for instance “gene that produces yellow blossoms”: “gene that produces yellow blossoms”  Realizers:

(come under one single concept)

p1x, p1y, … (fulfil causal task that defines the gene concept)   (come under different concepts)

“mol. conf. of type P1x” “mol. conf. of type P1y” Second, let us consider the anti-reductionist consequences. The multiple realization argument implies that the appropriate concepts are not co-extensional. It is not possible to correlate (constructed) physical concepts with the functionally defined concepts of the special sciences. To put it in terms of the truth-maker relation, there are entities that make one concept of the special sciences true. For instance, they make true the biological concept “gene that produces yellow blossoms”. However, these entities make different physical concepts true, say either “molecular configuration of type P1x” or “molecular configuration of type P1y”. As a result of this, there exist concepts of the special sciences that are not coextensional with the relevant physical concepts. For instance, the biological concept “gene that produces yellow blossoms” is not necessarily co-extensive with one of the physical concepts “molecular configuration of type P1x” or “molecular configuration of type P1y”. Therefore, there is no homogeneous reductive explanation of the gene tokens in terms of physics possible (cf. ‘concept of explanation’, this chapter, p. 71). There are thus sets of property tokens that are 40

Cf. Hull (1974, chapter one) and Rosenberg (1978 and 1985) who examine the multiple realization argument in the philosophy of biology.

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homogeneously explained only by means of biological concepts (embedded in biology): Consequences of multiple realization of a biological type, for instance “gene that produces yellow blossoms”: “gene that produces yellow blossoms”  Realizers:

(homogeneous expl. by one single concept)

e1, e2, … (fulfil causal task that defines the gene concept)  

(heterogeneous expl. by different concepts)

“mol. conf. of type P1x” “mol. conf. of type P1y” 1. No correlation of the concept “gene that produces yellow blossoms” with one physical concept possible. The concepts are not coextensional. 2. No homogeneous reductive explanations of genes for yellow blossoms possible. Third, let us consider a concrete case that supports the multiple realization argument: that of genes. Genes cause phenotypic effects that emerge in virtue of the causing of the synthesis of enzymes. Genes are generally taken to be the exemplary case of an entity multiply realized by different molecular configurations. For instance, take a gene that may cause the synthesis of a certain enzyme that in turn causes the yellow blossoms of a flowering plant. However, the gene tokens for yellow blossoms can be identical with different molecular configurations (different sequences of DNA bases). This is possible because differences in the sequences of DNA bases may nonetheless lead to the synthesis of the same enzyme (same sequences of amino acids). Therefore, the physically different gene tokens may develop the same yellow blossoms. Thus, there is a physical difference, but this difference does not exclude that the gene tokens come under the same functional biological concept. Examples like this one suggest that concepts of the special sciences are not epistemologically reducible to physics, an issue we will enlarge upon later (cf. ‘the multiple realization argument applied to genetics’, chapter VII, p.262).

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Finally, let us reconsider the argument of multiple realization as it relates to ontological reductionism. Multiple realization is multiple description. Given ontological reductionism, any causally efficient property token is identical with a configuration of physical property tokens. Property types are concepts (cf. ‘concept of property types’, this chapter, p. 79). A property type is a concept that points out what certain entities have in common. Thus, a property type of the special sciences is a concept under which certain property tokens come in virtue of some salient similarity. In this context, a multiply realized property type is a concept of the special sciences that applies to property tokens that come under different physical concepts. To put it in terms of Kim’s model of reduction, the so-called physical ‘realizers’ come under different (constructed) physical concepts. From a physical point of view, they are differently described. Consequently, for each of the tokens of one type of the special sciences there is a reductive explanation but not the same reductive explanation for all of them. This is why ‘multiple realization’ is taken to be multiple description, or multiple explanation. There are multiple physical descriptions (explanations) of property tokens that are homogeneously described (explained) by a special science. Summing up: the ‘multiple realization argument’ claims that the coextensional concepts of different sciences, which depend on the truth making quality of the property tokens of the concepts of the special sciences being made true by the relevant physical concepts, are, in fact, made true by physically different molecular configurations. In other words, physically different molecular configurations can be grouped under single concepts of the special sciences. If the argument is sound, it is a general and strong argument against epistemological reductionism. After all, in order to reduce a theory of the special science epistemologically to physics, any concept of the theory in question has to be co-extensional with a (constructed) physical concept.

xiv. Consequences for Nagel’s model The argument of multiple realizations suggests the failure of Nagel’s model of reduction as it stands. Taking this argument for granted, most (if not all) of the concepts of the special sciences are not co-extensional with (constructed) physical concepts. Consequently, it is not possible to correlate these concepts of different sciences by means of bi-conditional bridge-principles. It is therefore not possible to deduce the truth of a certain law-like generalization of the special sciences from the truth of a

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certain physical law-like generalization. Consequently, the special sciences cannot be embedded in physics. Thus, it is not possible to reduce epistemologically theories of the special sciences to physics by means of Nagel’s model. His strategy can be only applied to concepts of different sciences that are co-extensional. The globally destructing power of the multiple realizability argument requires that we consider the consequences of it in more detail. First of all, let us consider the scope of the effects of the multiple realization argument. Taking the argument for granted, most (if not all) of the concepts of the special sciences are not co-extensional with (constructed) physical concepts. For instance, the biological concept “gene that produces yellow blossoms” is not co-extensional with the constructed physical concept “molecular configuration of type P1x” because there are gene tokens for yellow blossoms that come under the physical concept “molecular configuration of type P1y”. Second, given these effects, we can conclude as to the impossibility of deducing law-like generalizations of the special sciences from physical law-like generalizations by means of bi-conditional bridge-principles. Since most (if not all) of the concepts of the special sciences are not coextensional with (constructed) physical concepts, it is not possible to correlate these concepts by means of bi-conditional bridge-principles. As a result of this, it is not possible to deduce a law-like generalization of the special sciences from one single law-like generalization of physics. In the physical domain, the constructed concepts “molecular configuration of type P1x” (“P1x”) and “molecular configuration of type P1y” (“P1y”) do not enter into a single law-like generalization. Taking the multiple realization argument for granted, there are different realizer types for the yellow blossoms. For the sake of simplicity, let us assume that there are two different types of realizers that are described by the constructed physical concepts “P2x” and “P2y”. Like “P1x” and “P1y”, the concepts “P2x” and “P2y” do not enter into a single law-like generalization. In addition to this, molecular configurations that come under the concept “P1x” cause molecular configurations that come under the concept “P2x”, and molecular configurations that come under the concept “P1y” cause molecular configurations that come under the concept “P2y”. However, the crucial point is the following: there is no single lawlike generalization that connects realizers of the genes for yellow blossoms with realizers of the yellow blossoms. In the case in point, there are two law-like generalizations – one for each realizer type. As a result of this, it

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is not possible to construct one physical law-like generalization from which the biological law-like generalizations can be deduced by means of bi-conditional bridge-principles.41 Third, let us measure the consequences resulting from the impossibility of deducing a law-like generalization of the special sciences from a physical law-like generalization. Given this impossibility, it is not possible to apply the deductive-nomological strategy in order to provide homogeneous explanations of the theories of the special sciences in terms of physics. I shall leave aside at this point the insufficiency of Nagel’s model – compared to Kim’s model – to provide reductive explanations (cf. ‘Kim’s model of reduction’, this chapter, p. 99). Nonetheless, by Nagel’s model alone it turns out to be impossible to embed biology in physics, violating the very aim of Nagel’s model of reduction. What fatally hampers reduction, here, is the necessity that for each single biological law-like generalization, it be possible to construct a single physical lawlike generalization. To conclude, the multiple realization argument refutes Nagel’s model of reduction as it stands: Consequences of multiple realization for Nagel’s model of reduction: 1. No correlation of the concepts in question by means of bridgeprinciples is possible. The concepts are not co-extensional. 2. Therefore, no deduction of a law-like generalization of the special sciences from a single physical law-like generalization is possible. 3. Thus, no theory-embedding of theories of the special science in physics is possible. Summarizing, what we call the ‘consequence for Nagel’s model’ is that, by the multiple realization argument, Nagel’s model fails to provide a successful reductionist strategy. The bridge-principles are indispensable for Nagel’s model, and taking the multiple realization argument for granted, it is not possible to establish such bridge-principles in order to deduce law-like generalizations of the special sciences from physical lawlike generalizations. Consequently, deductive-nomological explanations cannot be provided, the special sciences cannot be embedded in physics, and hence, Nagel’s model fail to be a reductionist strategy as it stands.

41

Cf. Fodor (1974, pp. 97-115).

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The argument of multiple realization does not, in contrast, lead to a total failure of Kim’s model of reduction. After all, Kim established his model in order to take the multiple realization argument into account. In any case of multiple realization, it remains nonetheless possible to provide so-called local reductions of property tokens. However, local reductions do not establish homogeneous reductive explanations of sets of property tokens that come under concepts of the special sciences. Therefore, Kim’s model does not suffice for epistemological reductionism, as the following argument will show. First of all, remember that, by the multiple realization argument, most (if not all) of the concepts of the special sciences are not coextensional with (constructed) physical concepts. For instance, the biological concept “gene that produces yellow blossoms” is not coextensional with the constructed physical concept “molecular configuration of type P1x” because there are gene tokens for yellow blossoms that come under the different physical concept “molecular configuration of type P1y”. So, secondly, let us introduce Kim’s strategy of so-called local reductions.42 It is possible to apply Kim’s model of reduction to the property tokens of the special sciences taken individually. Let us once again consider the gene that produces yellow blossoms. Property tokens come under the functionally defined concept “gene that produces yellow blossoms” if they fulfil the causal task that characterizes the concept in question. This causal task is physically realized. This means, there are molecular configurations that fulfil the causal task defined by the concept “gene that produces yellow blossoms”. Since each realizer comes under a (constructed) physical concept, physics can explain why there are molecular configurations that come under the concept “gene that produces yellow blossoms”. More specifically, the physical explanation of a realizer token of the gene that produces yellow blossoms is a reductive explanation of the gene token in question (cf. ‘concept of explanation’, this chapter, p.71). This implies that it is theoretically possible to provide reductive explanations of each single gene token. This important point bears repeating: any configuration of property tokens comes under a functionally defined concept of a special science if it fulfils the causal task that characterizes the concept in question. Subsequent to this, it is possible to 42

Cf. in particular Kim (1998, pp. 93–95; and 2005, p. 25). This strategy can be traced back to Lewis (1980).

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discover physical realizers of the causal task in question. These realizers are described in terms of physics, and since any physical realizer token in question can be physically explained in a complete manner, physics provides reductive explanations of any property token that comes under a functionally defined concept of the special sciences: Consequences of multiple realization for Kim’s model of reduction: 1. No correlation of the concept “gene that produces yellow blossoms” with one physical concept is possible. The concepts are not coextensional. 2. No homogeneous reductive explanation of genes for yellow blossoms is possible. “gene that produces yellow blossoms”  Realizers:

(homogeneous expl. by one single concept)

e1, e2, … (fulfil causal task that defines the gene concept) 



(heterogeneous expl. by different concepts)

“mol. conf. of type P1x” “mol. conf. of type P1y” 



(embedded in / constructed out of)

Physics Local reduction provides reductive explanation of each gene token for yellow blossoms taken individually by means of one-way conditionals such as “If there is a molecular configuration of type P1x, then there is a gene that produces yellow blossoms”. The physical concept “molecular configuration of type P1x” - explains why a property token fulfils the causal task that defines the concept “gene that produces yellow blossoms” - is embedded in physics, thereby providing complete causal explanations of the components of the molecular configuration in question. Thus, anything that comes under this physical concept is a gene that produces yellow blossoms.

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Let us reconsider this local reduction in the context of conditionals between the concepts of different sciences. Reductive explanations by means of local reductions are not based on bi-conditional correlations between concepts of different sciences. One-way conditionals are sufficient. Taking ontological reductionism for granted, any property token of the special sciences is identical with a physical realizer. In the context of the completeness of physics, any physical realizer comes under a (constructed) physical concept that, embedded in a theory of physics, provides a reductive explanation of the property token in question. For instance, any gene token for yellow blossoms is identical with a certain molecular configuration, say either of type P1x or of type P1y. Consequently, any configuration of physical property tokens that comes under the (constructed) concept “molecular configuration of type P1x” comes under the concept “gene that produces yellow blossoms” as well. There exists a one-way conditional connecting a physical concept of a realizer type with the appropriate biological concept of the realized gene type. If a configuration of physical property tokens comes under the concept “molecular configuration of type P1x”, this configuration is a property token that comes under the concept “gene that produces yellow blossoms”: ∀x (P1xx ⇒ Bx) For instance: P1x: coming under the concept “molecular configuration of type P1x” B: coming under the concept “gene that produces yellow blossoms” Implicit in local reduction of property tokens is the possible extension to the property token sets of the special sciences. Over and above the reductive explanation of individual property tokens, there might be sets of property tokens that can be homogeneously, reductively explained by means of one-way conditionals from physical concepts to concepts of the special sciences. In general, any gene token for yellow blossoms that comes under the one physical concept about the realizer is reductively explained in a homogeneous manner. After all, the physical concept “molecular configuration of type P1x” leads to a reductive explanation of why the property tokens come under the concept “gene that produces yellow blossoms”. Let us assume, for instance, that the gene token for yellow blossoms of one flower is physically indiscernible from

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the gene token for yellow blossoms of its progenitor and its offspring. For that reason, it is possible to provide a homogeneous reductive explanation of the gene that produces yellow blossoms of these three gene tokens. Let us take these three gene tokens as a sub-set of the hole set of gene tokens for yellow blossoms. In the case of this sub-set, the causal task that defines the concept “gene that produces yellow blossoms” can be explained by means of the same (constructed) physical concept. For this homogeneous reductive explanation, a one-way conditional from the physical concept in question to parts of the extension of the concept “gene that produces yellow blossoms” is sufficient. Since it may be the case that the causal task that defines a concept of the special sciences is homogeneously realized within a single species, the local reduction can be a species/structure-specific reduction. In order to illustrate such cases, let us assume that there are only two species of flowers that possess genes for yellow blossoms. In addition to this, let us assume that the molecular configurations of type P1x realize the gene that produces yellow blossoms in the flowers of the one species, while the molecular configurations of type P1y realize the gene that produces yellow blossoms in the flowers of the other species. This means, the property tokens coming under the concept “gene that produces yellow blossoms” form two sub-sets each of which comes under one physical realizer concept. On this basis, a species/structure-specific homogeneous reductive explanation is possible. The concept “molecular configuration of type P1x” embedded in physics reductively explains in a homogeneous manner why property tokens that come under the concept “gene that produces yellow blossoms” in the one species, and under the concept “molecular configuration of type P1y”, will provide a homogeneous reductive explanation responding to the question of why property tokens come under the concept “gene that produces yellow blossoms” in the other species:

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Local reduction extended to species/structure-specific reduction: 1. Provided that biological types such as genes for yellow blossoms are uniformly realized within a certain species/structure, it is possible to construct a correlation of the concept “gene that produces yellow blossoms” in one species/structure with one physical concept about the realizers. 2. The homogeneous reductive explanation of genes for yellow blossoms in one species/structure is possible. The physical concept explains why the property tokens of the relevant species/structure fulfil the causal task that defines the concept “gene that produces yellow blossoms”. In other words, the realizer concept is embedded in physics and provides a complete causal explanation of the components of the molecular configuration in question. “gene that produces yellow blossoms”  “gene in species A” 



(species/structure-specific application of the gene concept)

“gene in species B”  (homogeneous reductive explanations)

“mol. conf. of type P1x” “mol. conf. of type P1y” 

 (embedded in / constructed out of)

Physics On this basis, third, let us compare this local reduction to Nagel’s model of reduction. Reductive explanations by means of local reductions are not based on bi-conditional correlations between concepts of different sciences. Taking for granted the multiple realization argument, property tokens come under concepts (of different sciences) that are not coextensional. Nonetheless, reductive explanations are possible because Kim’s model of reduction is based on one-way conditionals. This favourably compares to what we have seen of Nagel’s model, which requires bi-conditional bridge-principles, which is the same as coextensionality between relevant concepts.

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Fourth, we need to look at the limits of Kim’s local reduction. First of all, given that only sub-sets of property tokens that come under one concept of the special sciences can be reductively explained in a homogeneous way, Kim’s model of reduction does not suffice for epistemological reductionism. As we have seen, for a complete theory reduction, the co-extensionality of concepts (of different sciences) is required (cf. ‘necessity of co-extensionality for epistemological reductionism’, this chapter, p. 85). Second, let us assume that Kim’s local reduction can be extended to species/structure-specific sub-sets of property tokens. This means, there are species/structure-specific sub-sets of property tokens that can be homogeneously reductively explained in terms of physics. For instance, there are sub-sets of gene tokens for yellow blossoms of one type of flower that can be reductively explained in a homogeneous way by means of one (constructed) physical concept (embedded in a physical theory). This is as close as we can come towards epistemological reductionism in Kim’s model of functional reduction. But, third, the problem is the following one: the species/structure-specific subsets of property tokens come under one physical concept but not under one functionally defined concept of the special sciences. Kim’s model does not provide a functional criterion to construct (species/structure-specific) subsets in terms of the special sciences. For instance, as we saw with our example, the fact that three gene tokens for yellow blossoms are indiscernible as far as their physical composition is concerned does not give us a functional criterion to distinguish them from other gene tokens for yellow blossoms. In the same way the distinction of species in order to reach a species/structure-specific homogeneous reductive explanation is not based on a functional criterion. In any case, it is the physical composition that serves as the criterion in order to construct the sub-sets of the property tokens in question. This means, from a functional point of view, it seems that there is no reason to consider these sub-sets. Therefore, this extended local reduction does not entail epistemological reductionism either. I shall consider this issue in more detail in what follows. Finally, let us consider the consequences of this failure to provide sufficient grounds for epistemological reductionism. It suggests the elimination of the scientific character of the special sciences. Generally, we assume that functionally defined concepts of the special sciences express salient causal relations. This means, any property token that fulfils a specific causal task comes under a corresponding concept. However, any of these property tokens comes under a (constructed) physical concept as well. In terms of Kim’s model, they are the so-called realizers. In this

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context, the suggestion of the elimination of the concepts of the special sciences proceeds as follows: First of all, ontologically speaking, no concept of the special sciences can explain anything that is not captured by means of physics. After all, as shown in chapter one, the argument for ontological reductionism and the explanatory completeness of physics are sound. On this basis, Kim established his local reduction. Any property token of the special sciences can be reductively explained in physical terms. But this, secondly, raises questions about the relevance of the concepts of the special sciences in relation to Kim’s model of reduction. If, for instance, biological concepts do not explain anything that is not explained in physical terms, why do we need biology? As a matter of simplicity, either biology or physics would be sufficient. And since physics gives us explanatory completeness and more detail relative to biology, there seems to be no reason not to dissolve the special sciences into physics. Third, in order to avoid such an elimination of the special sciences, one may argue as follows: the special sciences can consider salient causal relations in a homogeneous way that are considered only in a heterogeneous way by means of physical concepts. This means, the special sciences can abstract from physical causal details, which is not possible in terms of physics. For instance, biology can explain the occurrence of yellow blossoms in a homogeneous way even if there are physical differences in the way yellow blossoms are caused. Contrary to this homogeneous biological explanation, physics is not able to abstract from these causal differences such as the difference between the molecular configurations of type P1 and of type P2. There is no single physical concept under which we can group the molecular configuration types P1 and P2 in order to explain homogeneously the occurrence of yellow blossoms in terms of physics. To put it another way, the composition of the molecular configurations is essential for the causal explanation of the occurrence of the yellow blossoms in terms of physics. This is why physics cannot abstract from the physical details of the composition of the realizers, and this is why the special sciences should not be eliminated. After all, they provide general causal explanations that physics cannot provide. However, as a fourth point, this raises the following question: what does this abstraction from physical causal details exactly mean – an abstraction that does not hinder the special sciences from being explanatory? To put it in terms of truth-making, how can two physically

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different causal relations make one and the same biological explanation true? Let us keep in mind that it is not true to say that physics explains any step in a causal relation while biology provides only a lacunary explanation. The genes for yellow blossoms are physically different, the yellow blossoms are physically different, and the causal relations from the gene tokens to the yellow blossoms are physically different. Nonetheless, there is only one biological explanation for them – an explanation that can abstract from all these physical differences and nonetheless be a homogeneous explanation. I shall propose a positive answer to these questions later (cf. ‘relationship between concept and sub-concepts’, this chapter, p. 152, and ‘epistemological reductionism by means of subconcepts’, this chapter, p. 157). However, the point I want to make here is the following: Kim’s model does not give us a satisfactory answer to these questions, as a result of which we are unable to find any basis for the explanatory relevance of the special sciences. Since there is no systematic relationship between the concepts of the special sciences and physical concepts, there is no good argument for the explanatory relevance of the special sciences. This is why the eliminationist option still remains. Thus, the challenge for epistemological reductionism in a conservative sense is to establish such a systematic relationship between, for instance, biological concepts and (constructed) physical concepts in order to guarantee the explanatory relevance of biological concepts. Kim does not provide such a systematic relationship by means of the extension of local reduction of property tokens to species/structurespecific sub-sets of property tokens. Rather in such cases, the causal task that defines for instance “gene that produces yellow blossoms” is different in each of its species/structure-specific sub-sets, such as those in the two different types of flowers. Since we don’t use a functional criterion to construct species/structure-specific sub-sets of gene tokens for yellow blossoms that are homogeneously realized, and since the species/structurespecific realizers are causally heterogeneous, the salient causal relation that defines “gene that produces yellow blossoms” vanishes. The argument proceeds as follows: let us assume once again two types of flowers that possess a gene that produces yellow blossoms. The genes for yellow blossoms are uniformly realized in each type of flower – by molecular configurations of type P1x in the flower of the one type, and by molecular configurations of type P1y in flowers of the other type. Thereby, the homogeneous concept “gene that produces yellow blossoms” is lost in these species/structure-specific sub-sets.

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Summing up the ‘consequences for Kim’s model’, we note that, while the multiple realization argument does not lead to a total failure of Kim’s model of reduction insofar as it remains possible to provide socalled local reductions of the description of property tokens in any case of multiple realization, local reductions do not yield homogeneous reductive explanations of sets of property tokens coming under concepts of the special sciences. Therefore, Kim’s model invites eliminativism with respect to the concepts and the explanations of the special sciences.

xvi. Implication of multiple realization Multiple realization implies that the physical realizers causally differ.43 To come under different physical concepts implies causal difference. For example, if the physical realizers of a gene that produces yellow blossoms come under different (constructed) physical concepts, there are causal differences between the physical realizers. The difference lies in the molecular configurations of their composition, and this implies that they figure in different causal relations with their physical environment. Let us, at this point, analyze what is required for multiple realization to be true and what that implies. First, let us consider the requirement of the multiple realization argument. Multiple realization means that property tokens that come under one concept of the special sciences come under different physical concepts. For instance, there may be property tokens that are, from a biological point of view, homogeneously described by the concept “gene that produces yellow blossoms”. However, these genes for yellow blossoms are physically differently realized. The realizers are molecular configurations that differ in their composition by physical property tokens. Based on this, they are described by means of different constructed concepts, such as “molecular configuration of type P1x” or “molecular configuration of type P1y”. However, each of these molecular configurations is identical with a gene token for yellow blossoms. Second, let us consider the implication of the multiple realization argument in detail. If property tokens come under different physical concepts, then there are causal differences between the property tokens in question. Two property tokens will not come under different physical concepts if there are no causal differences between them. The argument is that any conceptual distinction between property tokens within the 43

Cf. Kim (1999, pp. 17-18).

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vocabulary of one science implies a causal difference. Molecular configurations that differ in their composition differ in their environing causal relationships as well (cf. ‘property discrimination by causal difference’, chapter I, p. 41). Given that the realizers of the genes for yellow blossoms come under different physical concepts, this conceptual distinction implies that there are molecular configurations that causally differ. For instance, the realizers that come under the concept “molecular configuration of type P1x” stand in different causal relations with other molecules in their environment than the realizers of type P1y. To put it in terms of dispositions, the molecular configurations of type P1x possess the disposition to stand in other causal relations than the molecular configurations of type P1y. This means, finally, that there are differences in the way in which the molecular configurations realize the functional type in question. Since certain molecular configurations such as those of type P1x and those of type P1y, realize the gene that produces yellow blossoms, each fulfils the causal task that characterizes that type of gene. From a biological point of view, each molecular configuration of type P1x or type P1y is a property token that comes under the concept “gene that produces yellow blossoms”. However, each molecular configuration of a certain type such as type P1x realizes the causal task in question in a specific physical way. If there are causal differences between the molecular configurations of type P1x and P1y, then they differ in the way in which they are realizers of the gene that produces yellow blossoms. This is why the reductive explanation of gene tokens in terms of “molecular configuration of type P1x” is different from the reductive explanation in terms of “molecular configuration of type P1y” (both embedded in physics): Implication of multiple realization: In any case of multiple realization, the physical realizers causally differ. In summary, the ‘implication of multiple realization’ is that the realizers of a given functional type causally differ. For instance, if the physical realizers of a gene that produces yellow blossoms come under different (constructed) physical concepts, this means that there are causal differences between the physical realizers. The causal task that characterizes genes for yellow blossoms is realized in different ways.

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xvii. Critique of the multiple realization argument44 The multiple realization argument raises questions about the scientific quality of the special sciences. If a concept of the special sciences is about entities that come under different physical concepts, it abstracts from ontological details. The physical differences between these entities imply ontological differences that are not considered in, for instance, the concept “gene that produces yellow blossoms”. Since it is not possible to deduce each concept of the special sciences from a single constructed physical concept, the ability of the special sciences to focus on salient causal relations is put into question. Moreover, it seems that only the deducibility from physics could justify their scientific status. In this context, I shall discuss the so-called new-wave reductionism that amounts to, in the last resort, the elimination of the scientific character of the special sciences. First of all, ontological differences imply causal differences (cf. ‘property discrimination by causal difference’, chapter I, p. 41), and ontological identity (token-identity) implies causal indifference (cf. ‘identity by causal indifference’, chapter I, p. 45). This leads to the claim that physical differences imply ontological differences so that, for instance, physically and thus causally different realizers of the genes for yellow blossoms will differ ontologically. Molecular configurations of type P1x differ ontologically from molecular configurations of type P1y. Second, taking ontological reductionism for granted, concepts of the special sciences and physical concepts are about the same property tokens. This means, there are no ontological differences in the referents of these concepts because of token-identity. The gene tokens are just described in different ways by means of different concepts – on the one hand by “gene that produces yellow blossoms”, on the other hand by constructed physical concepts such as “molecular configuration of type P1x” or “molecular configuration of type P1y”. This means, third, that the special sciences use one and the same concept in order to explain property tokens that are ontologically different. Contrary to this, the physical concepts take into account those ontological differences. To put it another way, the gene concept abstracts from physical details and thus ontological details. The “gene that produces 44

Of course, there are various critiques of the multiple realization argument. My critique mainly takes into account Sober (1999) who criticizes the anti-reductionist consequences of Fodor (1984) and Putnam (1975), reconsiders Kim’s model of reduction, and considers the so-called new wave reductionism.

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yellow blossoms” is not sensitive to the ontological differences between the molecular configurations that realize genes for yellow blossoms. But, nonetheless, the concepts of the special sciences are taken to be about causal relations. Even more strictly, a functionally defined biological concept is about property tokens that fulfil a certain causal task. However, from a physical point of view, different causal relations are summed up under this single concept “gene that produces yellow blossoms”. Fourth, this fact raises questions about how the special sciences can abstract from physical and thus ontological details and focus nevertheless on salient causal relations. After all, the two relata and the causal relation are often physically different. For instance, the gene tokens differ physically, the yellow blossoms differ physically, and the causal relation from the genes to the yellow blossoms differs physically. The supervenience of the truth-values of the concepts of the special sciences on the truth-values of physical concepts does not explain this abstraction from ontological details. It seems that such an abstraction can only be justified by means of a deduction of the concepts, law-like generalizations and thus explanations of the special sciences from physical concepts, physical lawlike generalizations and thus physical explanations. However, it then seems to follow that there is also a physical homogeneity between the realizers of, for instance, the gene that produces yellow blossoms. But, if this were the case, the multiple realization argument would be refuted. Fifth, let us consider Kim’s position on these matters. Kim’s extension of the local reduction to species/structure-specific reduction does not provide a sufficient answer to these questions because the species/structure-specific concepts are not functionally defined (cf. ‘consequences for Kim’s model’, this chapter, p. 123). This means, the abstraction from ontological details is not based on criteria expressed in terms of the special sciences. There is no explanatory intermediate step from the detailed physical concepts about the realizers of the genes for yellow blossoms to the biological concept about genes. In fact, Kim’s species/structure-specific concepts of genes for yellow blossoms are defined in terms of the concept of genes for yellow blossoms and a certain physical specification. Kim’s unmodified position, here, gives us no explanation of how biology can abstract from ontological details and nevertheless focus on certain salient causal relations. Finally, let us turn to the solutions proposed by new wave reductionism, as applied to biology.45 This position exploits the way in 45

Cf. Bickle (1998, especially chapters 2 - 4, and 2003) for new wave reductionism, cf. McCauley (forthcoming) for a detailed consideration of new reductionism, and cf.

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which Hooker changed Nagel’s account of theory reduction.46 The general idea is the following: one constructs within the physical vocabulary a theory that is an image of the theory of the special sciences that one seeks to reduce. That is to say, one has to construct physical concepts that image concepts of the special sciences as far as possible. Applied to the relationship between biology and physics, one constructs physical concepts that image as far as possible functionally defined concepts of biology. The ideal image is a bi-conditional relation between the concepts of the special sciences with appropriate constructed physical concepts. For instance, the constructed physical concept “molecular configuration of type P” is an ideal image of the biological concept “gene that produces yellow blossoms” if and only if it is co-extensional with that concept. However, the possibility of multiple realization excludes the coextensionality between concepts of the special sciences and the constructed physical concept. Nonetheless, it is possible to construct physical concepts that are locally co-extensional with concepts of the special sciences. For instance, it is possible to construct a physical concept that is co-extensional with the biological concept “gene that produces yellow blossoms” within a certain set of organisms that are structurally identical. One thus gains several images of the theory of the special science in question. Each image covers a sub-set of those entities that are considered by the theory in question. As a case in point, it is possible to construct images of the biological concept “gene that produces yellow blossoms” each of which covers a certain set of organisms that are structural identical. To put the point in terms of laws, given multiple realization, for any biological law-like generalization it is possible to construct law-like generalizations in terms of physics that cover parts of the extension of the relevant biological law-like generalization. While these constructed lawlike generalizations can be deduced from general physical laws, the relationship between the biological law-like generalization and these constructed law-like generalizations is characterized as an image relation. This image relation means that it is possible to construct several physical law-like generalizations that taken together match the biological law-like generalization in question. Each of the constructed physical law-like generalizations is an image of the biological law-like generalization because it is at least equal in explanatory and predictive capabilities about Endicott (1998) for a criticism that brings out the need for bi-conditional bridgeprinciples. 46 Cf. Hooker (1981, especially § 3).

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a certain sub-set of entities within the extension of the law-like generalization in question. Let us put this idea in the context of Nagel and Kim. There is a continuum between two possibilities: On the one hand, there is the coextensionality between all concepts of a theory of the special sciences with physical concepts. In such a case, Nagel’s model of reduction can be applied. On the other hand, there is no co-extensionality between the concepts of different sciences because of the multiple realization argument. This is the case in Kim’s species/structure-specific or structurespecific reduction as well as the case covered by new wave reductionism. Taking the argument of multiple realization for most properties considered in terms of the special sciences for granted, it is only possible to construct law-like generalizations in physics that image the causal relations of the special sciences in a specific domain in the sense of new wave reductionism (or in the sense of Kim’s species/structure-specific reduction). Then, from a scientific point of view, the physical law-like generalizations are favoured because they are embedded in physics that is complete with respect to biology. Finally, such constructed physical lawlike generalizations replace the biological law-like generalizations that have only a pragmatic value at a certain stage of the scientific art. In this way, the new wave reductionism submits to the argument for multiple realization. But it nevertheless regards multiple realization as an argument in favour of replacing the special sciences by constructed physical concepts. This move takes into account the completeness of physics and ontological reductionism. To conclude, any reductionist position that renounces bi-conditional bridge principles in order to establish coextensionality between concepts of different sciences ends up giving us a theory replacement instead of justifying conservative reduction. In sum, what we are calling the ‘critique of the multiple realization argument’ has two main critical strands that produce quite similar outputs. First, since it is not possible to construct physical concepts that are coextensional with concepts of the special sciences, the multiple realization argument shows that the scientific quality of the special sciences is spurious. Or, each special science theory can be replaced with certain constructed physical theories that taken together cover the domain of the special science in question. Such constructed physical theories are scientifically favoured with respect to the special sciences. Consequently, the latter ones can be eliminated. To put it simply, Fodor and Putnam take the multiple realization argument in order to argue for the irreducibility of the special sciences and

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thus their scientific autonomy. On the other hand, this irreducibility puts the scientific quality of the special sciences into question and provides grounds for the elimination of the special sciences. Following Fodor and Putnam, the new wave reductionists take the argument for multiple realization for granted, but instead of using this to advance an irreducibility argument, advance the argument that the special sciences can be replaced with constructed physical theories. The multiple realization argument thus leads to a dilemma: on the one hand, if it is taken to show the irreducibility and thus the autonomy of the special sciences, then entities, insofar as they are described by the special sciences, cannot be causally efficacious, given the causal completeness of the physical domain and the argument for ontological reductionism. If the special sciences capture causal relations without physics being able to capture these relations in its terms nor a reduction of the concepts of the special sciences to physical concepts possible, then it follows that the causal relations that the special sciences consider in their terms are ontologically not identical with something physical. I shall consider this issue later on in more detail (cf. ‘starting point ontological reductionism’, chapter III, p. 168, ‘implication of anti-reductionism’, chapter III, p. 169, and ‘conclusion’, chapter III, p. 172). On the other hand, if the multiple realization argument is taken to show that one can only construct physical theories for species/structure-specific or structurespecific realizers of the concepts of the special sciences without there being co-extensional concepts and thus deduce the law-like generalizations of the special sciences from physical laws, then the theories of the special sciences are eliminated in favour of physical theories. As a way out of this dilemma, I shall propose a reductionist strategy that assumes the multiple realization argument and at the same time makes a case for the indispensable scientific character of the special sciences. Consequently, my proposal is an argument for a conservative epistemological reductionism.

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New strategy for epistemological reductionism xviii. Detectability of physical differences Any physical difference can in principle be detected by the special sciences. There is no physical difference accounting for different types of realizers of a given functional type possible that does not lead to functional differences that the special sciences can in principle detect. Let us briefly come back to the multiple realization argument and consider the argument for this claim in two different formulations, evaluate this argument in the context of explanations and go into possible objections. First, let us reconsider the multiple realization argument. That argument mainly claims that property tokens that are physically heterogeneously described can be homogeneously described in terms of the special sciences. The point I would like to stress is the following: although these property tokens do not come under one physical concept (because of physical differences), the special sciences are able to bring out what these property tokens have in common. They can focus on salient causal relations that physics does not consider in a homogeneous way. However, it is not excluded by the argument of multiple realization per se that there are differences that can be expressed in terms of the special sciences as well. For instance, that argument does not exclude that genes that are realized by molecular configurations of type P1x differ biologically from the genes that are realized by molecular configurations of type P1y. This consideration takes up the criticism of the multiple realization argument put forward by Bechtel, Mundale and McCauley.47 They maintain that the idea of widespread multiple realization is an illusion arising from the fact that the functional description is coarse-grained, whereas the physical description of the realizer is more fine-grained. Therefore, if one uses the same degree of abstraction in the functional and the physical description, the impression of widespread multiple realization vanishes. If there are nonetheless cases of multiple realization, we should try to introduce a more fine-grained functional classification. I take up the latter point and propose a general strategy to introduce more fine-grained functional concepts. As I shall argue later on in a systematic manner, 47

Cf. Bechtel & Mundale (1999, pp. 201–204), and McCauley (forthcoming, section VIII).

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physical differences between realizers that come under one single concept of the special sciences lead to functional differences between these realizers. Based on these functional differences it is possible to construct functionally defined sub-concepts within the vocabulary of the special sciences in order to establish a co-extensionality between physical concepts and these sub-concepts. To conclude, I shall propose a strategy that systematically links concepts of the special sciences with physical concepts. This strategy develops functional reduction into epistemological reductionism and thus combines Kim’s functional reduction with Nagelian reduction. In this sense, my proposal goes beyond the proposals of Bechtel, Mundale and McCauley, providing for a complete and conservative reductionism. Second, let us consider a general formulation that suggests the detectability of physical differences in biological terms. Assume multiple realization in our world, w 1; thus on the one hand, there are entities that can be described by one and the same concept of the special sciences, but also, on the other hand, these entities are described by different physical concepts. For instance, genes for yellow blossoms are multiply realized by different molecular configurations. This means, entities that come under the concept “gene that produces yellow blossoms” (“B1”) come under different physical concepts, “molecular configuration of type P1x” (“P1x”) or “molecular configuration of type P1y” (“P1y”). Let us now suppose a world w2 that is physically distinct from our world w1. World w2 is physically such that there is no multiple realization. In w2, each entity that corresponds, for instance, to the concept “gene that produces yellow blossoms” (“B1”) comes under one physical concept, say “molecular configuration of type P1x” (“P1x”) (P1x in w1 = P1x in w 2). As a result of this, the concepts of the special sciences in w2 are co-extensional with physical concepts. For instance, the biological concept “gene that produces yellow blossoms” (“B1”) is co-extensional with the (constructed) physical concept “molecular configuration of type P1x”. Therefore, the descriptions of w1 and w2 differ only from a physical point of view. This means, in w2, there is for any biological concept such as “B1” a co-extensional physical concept such as “P1x”, whereas in w1, the genes that produce yellow blossoms are realized by molecular configurations that come under the physical concepts “P1x” or “P1y”. Having said this, our present concern should be to focus on the following question: can exclude the possibility of any occurrence of any difference in the description of w1 and w 2 in terms of the special sciences as well? Will the descriptions of w1 and w2 by means of concepts of the special

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sciences always be the same? Since most properties of the specials sciences are taken to be multiply realized (in w1), the question is about the absolute non-occurrence of any difference in the descriptions in terms of the special sciences.48 It seems to me that after a certain length of time, there will occur differences that are detectable in terms of the special sciences. Multiply realized genes (in w1) and uniformly realized genes (in w2) remain genes, but once in a while there will occur biological differences in w 1 that can be traced back to the physical differences between the realizers of the gene that produces yellow blossoms in w 1. Consequently, there will be differences in the biological descriptions of w1 and w 2. To put it another way, sooner or later, it is possible to detect functional differences between our biological world and duplicates of our biological world whereby the biological duplicate differs physically from our biological world: A biological world that is a biological duplicate of our world at t1 but that differs physically from our biological world, will differ biologically at tn as well. Third, let us consider another formulation of the detectability of physical differences in terms of the special sciences. I shall take the term ‘functional difference’ to indicate a causal difference that is detectable in terms of the special sciences, whereas the term ‘causal difference’ stands for a difference that is expressed in physical terms. Physical realizers of different physical types that all realize the same functional type are distinct by their physical composition. Any difference in composition that accounts for there being two types of realizers also implies a causal difference between the physical tokens coming under these different types; the realizers are causally heterogeneous (cf. ‘causal discrimination by causal difference, chapter I, p. 41). For any physical causal difference that amounts to there being two different types of realizers, there is an environment conceivable in which that physical difference leads to a functional difference as well. For instance, us take the molecular configurations of type P1x and P1y that realize genes for yellow blossoms in our world w 1. As they are physically different, these molecular configurations could be embedded in 48

Cf. Heil (2003), p. 116) who makes a quite similar point, even though in terms of qualities and dispositions: “Try changing a fragile object qualitatively, without altering it dispositionally. The object might remain fragile but become fragile ‘in a different’ way”.

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an environment in which their physical difference accrue different selective advantages or disadvantages, and thus instantiate a functional difference.49 To put it simply, entities that come under the biological concept “gene that produces yellow blossoms” and under the physical concept “molecular configuration of type P1x” differ functionally compared to entities that come under the physical concept “molecular configuration of type P1y”. In particular, these functional differences between the gene tokens are linked with the characteristic causal task that defines the gene that produces yellow blossoms. These functional differences can be traced back to the physical differences between the molecular configurations of type P1x and type P1y. As already mentioned, there are differences in the way in which the molecular configurations of type P1x and type P1y realize the causal task that defines the gene that produces yellow blossoms. These differences in the realization of the causal task can be detected in certain environments. This means, there is a functional difference in the way in which the genes that are realized by one type of molecular configurations fulfil the causal task to produce yellow blossoms compared to the genes that are realized by the other type of molecular configurations: When any causal difference accounts for there being two types of realizers of a concept of the special sciences, the possibility exists of conceiving of an environment in which this causal difference can be detected in terms of the special sciences. On this basis, let us consider such functional differences in more detail. Genes for yellow blossoms that come under the physical concept “molecular configuration of type P1x” differ in their composition of physical systems compared to genes for yellow blossoms that come under the physical concept “molecular configuration of type P1y”. This difference in composition means that the components of the molecular configurations of type P1x stand in other causal relations to each other and to physical 49

Here, I agree with Rosenberg (1994, p. 32), even if I focus only on the differences that account for molecular configurations being of two types of realizers. Compare furthermore Papineau (1993, p. 47) who correctly claims that “variable causes can have uniform effects in virtue of mechanisms which select items because they have that effect”. Just to bear in mind, I do not argue against this claim. After all, I do not argue against the multiple realization argument. But the crucial point is that there are always environments possible in which physical differences lead to different functional effects that are linked to Papineau’s “uniform” effects.

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systems in the environment than the components of the molecular configurations of type P1y. From this it follows that the molecular configurations of type P1x realize the gene that produces yellow blossoms in a causally different way compared to molecular configurations of type P1y, as when there are different interactions with the cellular components that are involved in the causal task to produce yellow blossoms. Generally, different intermediate steps in the production of the yellow blossoms occur in those cases in which the molecular configurations are different. This difference in the production of the yellow blossoms becomes detectable under certain environmental conditions. Imagine, for instance, an environment with a high radiation of ultraviolet light that increases the probability of gene damages. Under such environmental conditions, the difference in composition of the molecular configurations of the genes leads to a functional difference that is in principle detectable in terms of biology. For instance, genes for yellow blossoms that come under the physical concept “molecular configuration of type P1x” may possess a relatively high resistance to ultraviolet light whereas genes that come under the concept “molecular configurations of type P1y” may possess a relatively low resistance to ultraviolet light. This means, in environments with high radiation of ultraviolet light, the way in which genes cause yellow blossoms depends on whether the genes are resistant to ultra-violet light, or whether they are not resistant to ultra-violet light. To put it extremely simply but in an illustrative way, there is a difference in time and / or the need of resources in order to cause the yellow blossoms. Since I shall go into biological details in part II of this work, let us oversimplify for now and say that flowers with genes for yellow blossoms that come under the physical concept “molecular configuration of type P1x” cause yellow blossoms in a way that is advantageous for selection. Compared to this, flowers with genes for yellow blossoms that come under the physical concept “molecular configurations of type P1y” may need more time in order to cause the yellow blossoms. In this instance, this is disadvantageous for selection. These genes have to be repaired several times, and in order to repair the genes from the damages caused by the ultra-violet light, the flower needs resources that ‘lack’ at other locations of the flower. This is a functional difference that can be detected in biological terms and that is salient for selection. Let us note that this functional difference could hardly be detected in the environmental conditions that existed in our world several hundred years ago. However, the point is that one can conceive an environment in

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which the physical difference of composition in question leads to a functional difference that is linked to the characteristic causal task. Since any difference in composition between two types of molecular configurations means that the components of the one molecular configuration stand in other causal relations than the components of the other molecular configurations, one can always conceive a physical environment in which this difference leads to a functional difference that is detectable in terms of the special sciences. My claim therefore is that no possible physical differences between realizers, inasmuch as they justify the distinction between two different types of realizers, would under any physical condition, never lead to any functional difference. In fact, many functional implications of physical differences are already well known. Moreover, since we focus on physical differences between types of realizers, this functional difference is linked to the causal task that defines, for instance, the concept about genes for yellow blossoms: A certain concept defined in terms of composition implies that the components of the referents of this concept stand in certain causal relations to each other and possess therefore a certain disposition to stand in particular causal relations with the environment. For any difference in composition accounting for two different types of realizers, there is a difference in dispositions, and for any difference in dispositions, there is an environment possible in which this difference becomes manifested and leads to a functional difference that is detectable in terms of the special sciences. Since we focus on physical differences that account for there being two types of realizers, there is an environment possible in which the physical differences between the types of realizers lead to a functional difference in the way the causal task in question is realized. Let us add that this argument does not depend on the ability of the biologist to distinguish the environmental/physical conditions in her own terms. It is sufficient that some physicist conceives environmental conditions and some biologist detects a functional difference. Thereby, ‘detect’ means to express a functional difference in terms of the special science in question. Therefore, to detect a functional difference in terms of fitness advantages or disadvantages that are relevant for selection is all I intend to argue for at this point. For any physical difference that accounts for there being two types of realizers, there is an environment conceivable in which the physical difference in question leads to a functional

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difference that is detectable in biological terms because it is salient for selection. To reconsider the example, it does not matter whether or not ‘ultra-violet light’ is a biological or a physical concept. Moreover, suppose that the biologist is not able to describe the environmental conditions that lead to functional differences. Nonetheless, she can detect functional differences between the gene tokens in question because the gene tokens are advantageous or disadvantageous for selection. Let us consider such cases in more detail because they may be taken to suggest a problem. Let us suppose that the biologist detects functional differences between gene tokens for yellow blossoms that come under the one concept “gene that produces yellow blossoms”. In order to avoid the eliminativist consequences of the new wave reductionism, the biologist should construct concepts that take into account these functional differences. The one concept “gene that produces yellow blossoms” can, after all, not explain the functional differences (cf. ‘critique of the multiple realization argument’, this chapter, p. 133). Within biology as it stands, it seems that biology cannot abstract from physical details while always remaining its indispensable explanatory function. Up to now, it seems that such functional differences could be only explained in terms of the mentioned species/structure-specific constructed physical theories – theories that are intended to replace the biological theory. In order to sum up my point, let us consider a general formulation in terms of dispositions. Realizer configurations of different physical types possess different dispositions with respect to the way in which they fulfil the causal task in question. For instance, the gene tokens for yellow blossoms that come under the physical concept “molecular configuration of type P1x” possess the disposition to cause yellow blossoms in a way that is advantageous for selection compared to the gene tokens that come under the physical concept “molecular configuration of type P1y”. The crucial point to decide is how biology can retain its explanatory indispensability in face of the threat of eliminativism. Fourth, since we are dealing here with explanations, we need to be clear about our two patterns of explanation, one concentrating on the causal, and one on the functional. Generally speaking, in order to explain different effects, different causes are suggested. Thus, whenever two property tokens that come under one single concept lead to effects that come under different concepts, this difference in effects cannot be explained by means of the one single concept in question. To put it simply, genes for yellow blossoms cause the blossoms – but sometimes in a way that is advantageous for selection, and sometimes in a way that is

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disadvantageous for selection. In the context of this oversimplified example it becomes clear that there is no explanation of this functional difference by means of the one single gene concept. The fact that the yellow blossoms are caused is explained, but the functional difference does not follow from the way in which they are caused. After all, the biologist recognizes only one and the same cause (coming under one concept) for two different side effects (that are linked with the effect they have in common). Let us consider this issue in the context of the different worlds w1 and w 2. Assume that at one day, the biological description of w 1 starts to differ from the biological description of w 2. How could we explain this first difference since there is supposed to be just one and the same type of cause? This problem raises questions about the coherence of biology, and, hence, cries out for further explanations that are currently provided only by physics such that the elimination of biology could be suggested. This problem becomes even more obvious in the context of the second formulation of the argument with only one world. How could we coherently explain possible functional differences by means of one single concept? For instance, how could a biologist explain the functional differences between gene tokens for yellow blossoms if there is only one single concept under which these gene tokens come? Since relevant physical differences lead to functional differences, and since such functional differences are not explained by the common functional concepts of the special science in question, the explanatory relevance of these concepts becomes doubtful. Finally, let us consider possible objections to my argument to detect physical differences between types of realizers in terms of the special sciences. First of all, someone may maintain that the special sciences are sometimes not that precise, their epistemological classifications are sometimes vague, and maybe, that is why their law-like functional definitions and (if any) general laws are not strict but so-called ceterisparibus laws. The functional definitions are, after all, open-ended lists that focus on salient causal relations (cf. ‘functionally defined concepts’, this chapter, p. 109). So much the worse for any reductionist that starts from the incompleteness of the special sciences, and ends up there! This kind of objection is wrongheaded because it doesn’t touch my argument. The general point is that in principle, any causal physical difference between types of realizers leads to a functional difference that is detectable and thus expressible in terms of the special sciences. In addition to this, the aim of epistemological reductionism is not to show that the

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special sciences should be able to explain any physical difference, or to determine environmental conditions as precisely as does physics. To the contrary, it is physics that should explain what is inexplicable in terms of the special sciences. My strategy aims at constructing biological concepts that are co-extensional with physical concepts (cf. ‘implication of detectability’, this chapter, p. 148). As already said, I do not argue against the multiple realization argument and I do not claim that every science should be like physics. To the contrary, my aim is to provide a systematic link between the special sciences and physics that is based on coextensionality between their concepts. It seems that this is the only strategy available to avoid the elimination of the special sciences. Without such a co-extensionality between concepts the scientific status of the special sciences is put into peril. Furthermore, one may use my argument to construct contrary cases. For instance, one may conceive of cases in which there exist physical conditions in which the physical differences between the realizers does not lead to functional differences, or those in which physical differences appear only for a certain length of time, or one may emphasize the fact that there certainly are environmental conditions in which many physical differences do not lead to biological functional differences. One may only think about common environments in our world in which differences in resistance to ultraviolet light imply no functional differences. Thus, at least within a certain length of time, no functional difference may occur. In regard to this, I would like to note the following: the possibility of functional differences still remains. There are different dispositions by which it is possible to distinguish the entities in question. Even with the environmental conditions at our world, the genes for yellow blossoms that are realized by molecular configurations of type P1x possess another disposition to fulfil the causal task of being a gene that produces yellow blossoms than the genes for yellow blossoms that are realized by molecular configurations of type P1y. On the other hand, there might be physical differences conceivable that disappear after a certain length of time. Genes for yellow blossoms may differ with regard to some microphysical system, but these differences may vanish after a hardly measurable short time. Therefore, it might not be reasonable to postulate a different disposition to fulfil the causal task of being a gene that produces yellow blossoms. How to deal, hence, with such physical differences? In regard to this, let us re-examine the concept of a physical realizer (cf. ‘Kim’s model of reduction’, this chapter, p. 99). These physical differences are unlikely to be of relevance

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to the realization of the causal task in question. If microphysical systems are added to or disappear from a realizer configuration without any impact on the realization of the causal task, they do not play any role in realizing the causal task in question. For instance, let us assume that the physical difference between two individual realizers consists in one single electron. If this electron does not play any role in order to realize the causal task of the gene that produces yellow blossoms, there is only one type of realizer – that is to say, these two individual realizers come under one and the same physical realizer type. Let us take this point from the perspective of explanation. In order to provide an explanation any abstraction from physical details should be admissible as long as the physical explanation remains complete. To put it in terms of our example, the genes for yellow blossoms are multiply realized by different molecular configurations. But, if the physical differences are ‘redundant’ in order to explain why a given molecular configuration realizes the causal task that defines the concept “gene that produces yellow blossoms”, one may leave these physical differences aside. Let us distinguish between ‘relevant’ and ‘redundant’ physical differences. ‘Relevant’ physical differences between realizers are physical differences that make it impossible to explain homogeneously and coherently in physical terms why the causal task is fulfilled. Contrary to this, ‘redundant’ physical differences can be theoretically ignored in order to provide a homogeneous physical explanation of the causal task that defines the gene that produces yellow blossoms. For instance, in order to explain the function of genes for yellow blossoms in physical terms, additional microphysical systems such as possessing or lacking one additional electron are usually not considered. These physical differences are ‘redundant’ for the explanation of that task. To restate the counterarguments, we arrive at the conclusion that either (dispositional talk of) functional differences is reasonable, or the physical differences are ‘redundant’. Let us finally consider the following counterexample: is it possible to construct a world in which physically different molecular configurations come under exactly the same set of physical laws? This means that there exist no possible environmental conditions in which the physically different realizers of the gene that produces yellow blossoms will differ functionally. Since such a situation is not possible in world that is a physical duplicate of our world, I shall leave this kind of counterexample

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aside.50 My argument is based on the following considerations: if two entities differ in their composition, there are always environmental conditions possible in which these differences in composition lead to a difference in their causal efficacy. There are different ways in which the components of the molecular configurations interact with their environment. There always is a physical environment possible in which these differences lead to differences in the way in which the configurations react to certain environmental conditions. To put it another way, different configurations of physical property tokens differ in their dispositions to react to the environment. For each difference in such dispositions there is an environment possible in which this difference becomes manifest. Therefore, it is possible to distinguish these molecular configurations also in terms of different nomological descriptions. We will call this the ‘detectability of physical differences’, defining it as the rule that any physical difference can in principle be detected by the special sciences. There is no physically ‘relevant’ difference between the realizers of, for instance, a gene that produces yellow blossoms, that does not lead to functional differences that the biologist can detect. A different disposition how to fulfil the causal task of the genes for yellow blossoms corresponds to each realizer type. This means, genes for yellow blossoms that are realized by molecular configurations of a certain physical type possess different dispositions with respect to the production of yellow blossoms. Thus, there are functional differences that are linked with the characteristic causal task and that can be traced back to physical differences.

xix. Implication of detectability The special sciences are able to construct functionally defined subconcepts that are co-extensional with physical concepts. Given functional differences between property tokens that come under a single concept of the special sciences, it is always possible to construct sub-concepts of functionally defined concepts so that these sub-concepts describe entities that are uniformly described by physical concepts. For instance, it is possible to construct sub-concepts of “gene that produces yellow 50

Cf. Shoemaker (1980; added note on p. 135) to which the discussed possibility can be traced back. There, the possible counterexample is proposed by Richard Boyd. My counterargument is in the spirit of Shoemaker’s own argument, and the general argument of this section.

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blossoms” each of which is co-extensional with a (constructed) physical concept such as “molecular configuration of type P1x” or “molecular configuration of type P1y”. This construction of sub-concepts is based on the previous section. This means, contrary to Kim’s species/structurespecific reduction, there is a causal argument to construct sub-concepts and establish co-extensionality. After all, the physically different gene tokens for yellow blossoms differ functionally so that biologists can take these functional differences into account within a functional definition in their own functional vocabulary. Let us consider this strategy in three steps. First, let us reconsider the ability of the special sciences to detect physical differences as examined in the previous section. Any physical difference that amounts to there being different physical types of realizers leads to functional differences such as the mentioned functional differences between gene tokens for yellow blossoms. This means, the physical differences between the types of realizers are detectable in the functional vocabulary of biology – and not only in terms of physics. At least, it is possible to conceive environmental conditions in which physical differences between types of realizers lead to functional differences that are linked to relevant causal tasks. Based on this, it is possible to distinguish, for instance, genes for yellow blossoms by means of causal differences in the way in which they produce yellow blossoms. This is an important distinction between my model and Kim’s species/structurespecific reduction (cf. ‘consequences for Kim’s model’, this chapter, p.123). Kim’s criterion to consider sub-sets of the genes for yellow blossoms is based on purely physical arguments. This strategy is similar to the new wave reductionism that leads to the elimination of the special sciences (cf. ‘critique of the multiple realization argument’, this chapter, p.133). In my proposal, the distinction of the gene tokens for yellow blossoms is based on possible functional differences that are detectable in terms of biology. Based on this, the co-extensionality between concepts of different sciences is established that is necessary for conservative epistemological reductionism. Our second, step consists in examining how the sub-concepts are constructed. Based on the detectability of functional differences between the molecular configurations of type P 1x and P1y, it is possible to construct more detailed concepts of the genes for yellow blossoms. Thus, biologists can construct in their own functional vocabulary sub-concepts of the concept “genes for yellow blossoms” that are co-extensional with physical realizer concepts. These sub-concepts take into account any possible

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functional difference that is a consequence of the physical differences that account for different realizer types of the genes for yellow blossoms. The argument in general can be summed up as follows: (a) we take the multiple realization of functional types for granted, which is to say, the property tokens that come under one concept of the special sciences differ in physical respects. Then, (b), comparing worlds containing multiply realized functional types to worlds without multiple realization of those functional types, or given certain environmental conditions, we find that the physical differences between the realizer types lead to functional differences as well. Thus, they are detectable in terms of the special sciences as well (cf. ‘detectability of physical differences’, this chapter, p.138). It is, hence, possible to construct more detailed functionally defined sub-concepts. These sub-concepts are formulated in terms of dispositions and take into account any possible functional difference of the relevant physical differences. This remains, at least, a possibility in principle. Third, let us consider the level of the constructed sub-concepts in more detail. They are co-extensional with physical concepts because each relevant physical difference leads to a functional difference that can be considered in terms of the special science in question. Contrary to this, functionally defined concepts admitting of multiple realization do not take into account these possible functional differences. This is why I shall call these concepts abstract concepts. Considering a certain abstract concept, it is possible to construct sub-concepts each of which takes into account a specific functional detail that is tied to the causal task in question. This means, each sub-concept describes a certain way to fulfil the causal task that defines the abstract concept. Therefore, by means of the constructed sub-concepts, any possible functional difference can be traced back to relevant physical differences. For instance, biologists may distinguish between genes for yellow blossoms that are more resistant to ultra-violet light and thus advantageous to selection and genes for yellow blossoms that are not that advantageous to selection in the same environment. This functional difference becomes detectable under certain environmental conditions such that the distinction by means of different dispositions is well argued. Under the assumption that any relevant physical difference is detectable, the functionally defined sub-concepts are necessarily coextensional with (constructed) physical concepts. To reiterate: the special sciences can consider any relevant physical difference in their own terms, and hence, construct appropriate functionally defined sub-concepts co-

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extensional with the physical concepts of the realizer types. The physical concept describes entities that are physically homogeneous. In relation to the way the special sciences construct functionally defined sub-concepts that are co-extensional with physical realizer concepts, I shall consider the relationship between concepts and sub-concepts in the following section. The construction of functionally defined concepts will be reconsidered later on in more detail (cf. ‘epistemological reductionism by means of subconcepts’, this chapter, p. 157): Implication of the detectability of any relevant physical difference: Construction of functionally defined sub-concepts that are c o extensional with physical concepts of realizer types: “gene that produces yellow blossoms” 



(functionally defined sub-concepts)

“gene that produces “gene that produces yellow blossoms yellow blossoms + selective advantage” + selective disadvantage” 



(co-extensional with)

“mol. conf. of type P1x” “mol. conf. of type P1y” 



(embedded in / constructed out of)

Physics Finally, let us examine the co-extensionality thematic in connection to law-like generalizations. If it is possible to construct sub-concepts based on functional differences corresponding to each type of physical realizer, it must be possible to conceive more detailed law-like generalizations of the special sciences that are co-extensional with physical law-like generalizations. For instance, it is possible to conceive a detailed biological law-like generalization in which the sub-concept “gene that produces yellow blossoms that is advantageous for selection” figures. This expression is more detailed than the current law-like generalization in which the abstract concept “gene that produces yellow blossoms” figures.

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Any law-like generalization in which the abstract concept figures can be further specified by a more detailed law-like generalization in which the more detailed sub-concepts figure. I shall consider their relationship in the following section (cf. ‘relationship between concept and sub-concepts’, this chapter, p. 152). The crucial point I want to emphasize here is that the constructed detailed law-like generalizations are co-extensional with physical law-like generalizations insofar as these are conceived in terms of the physical realizer types. Their importance for my conservative reductionist strategy will be spotlighted in the last section of this chapter (cf. ‘epistemological reductionism by means of sub-concepts’, this chapter, p. 157). Summarizing, let us call the argument we have been making here the ‘implication of detectability’. The special sciences are able to construct functionally defined sub-concepts that are co-extensional with physical concepts. Given functional differences, it is always possible to construct sub-concepts of functionally defined concepts such that each of these subconcepts describes all and only those entities that are uniformly described by a physical concept. For instance, it is possible to construct sub-concepts of “gene that produces yellow blossoms” each of which is co-extensional with a (constructed) physical concept such as “molecular configuration of type P1x” or “molecular configuration of type P1y”. In this context it is possible to conceive detailed law-like generalizations in the functional vocabulary of biology that are co-extensional with law-like generalizations of physics insofar as they are expressed in terms of the physical concepts of the realizer types.

xx.

Relationship between concept and sub-concepts

Abstract concepts can be deduced from each of their sub-concepts. If the difference between a concept and its sub-concepts is that the sub-concepts only consider additional functional details, it is a theory-immanent question to deduce a concept from each of its sub-concepts. This tells us that we will not damage the scientific status of an abstract concept about property tokens that come under different realizer concepts by embedding it within sub-concepts. In order to make the point about relationship between abstract and detailed concepts, let us examine the example of the deducibility of the concept of genes for yellow blossoms from its subconcepts. To do so, we will consider these issues in connection with law-

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like generalizations, determine the possible danger of elimination posed here and, finally, put these issues in the context of the determinatedeterminable relation. First, let us outline the general relationship between abstract concepts and detailed concepts. An abstract functionally defined concept is so defined by a specific causal task. Functionally defined concepts that are more detailed (relatively to the abstract concepts) take into their scope both that causal task and specify further the causal relations that define that causal task. Thus, the causal task that characterizes a more detailed functionally defined concept takes those causal relations into account in a more detailed way than the abstract concept. Against this background, let us examine this relationship as it applies to the functionally defined concept of genes for yellow blossoms. Clearly, the functionally defined concept “gene that produces yellow blossoms” is a concept that abstracts from possible functional differences that are based on the physical differences between the realizers. These functional differences are only considered by more detailed functionally defined concepts that take these functional differences into account. These are the sub-concepts that are about entities that can be uniformly described in terms of physics. For instance, the sub-concept “gene that produces yellow blossoms in a way that is advantageous for selection” distinguishes certain gene tokens for yellow blossoms from other gene tokens for yellow blossoms that are not that advantageous for selection. Second, let us consider how we deduce an abstract concept from each of its more detailed sub-concepts. Provided that the abstract concept differs from the more detailed sub-concept only in the way in which the more detailed sub-concepts contain additional details, the abstract concept can be deduced from the more detailed sub-concepts. The argument goes as follows: a detailed sub-concept can be taken as a relatively long conjunction of single concepts. Assuming that the relatively long conjunction of concepts is true about a certain entity, the abstract concept is true about that entity as well. From this it follows that the degree of descriptive detail is only a theory-immanent matter. One has the conceptual leeway to focus only on the salient causal relation that defines the abstract concept if one so wishes, for instance, to bring out what the entity in question has in common with a broad set of other entities. After all, the abstract concept has generally a bigger extension than a more detailed sub-concept. Or, one may focus on what a narrower set of entities has in common and how the entities in this set differ from other entities that come under the abstract concept as well. This more detailed sub-

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concept gives additional functional details about the causal task that characterizes the abstract concept. To reiterate: it is a theory-immanent question which degree of abstraction or detail is scientifically appropriate, and the task of comparison allows for the application of relatively abstract concepts, while allowing, also, the application of relatively detailed concepts in order to explain certain differences. Therefore, the relationship between an abstract concept and its subconcepts can be seen as integrating the abstract concept in its sub-concepts such that the scientific quality of the abstract concept is not put into peril. The argument proceeds as follows: first of all, both the abstract concept and its sub-concepts are formulated within the vocabulary of the same theory. Second, the only difference between an abstract concept and its sub-concepts is the degree of abstraction from functional details. Finally, this abstraction is thus understandable within the theory in question – it is a theory-immanent matter on which functional details one wishes to focus. To put it another way, the elimination of the abstract concept is not necessitate from the fact that the sub-concepts entail the causal task that defines the abstract concept in question. There is nothing scientifically discreditable in using an abstract concept to bring out salient functional features that a relatively broad set of entities has in common. Against this background, let us consider this deducibility in the context of the genes for yellow blossoms. It is possible to deduce “gene that produces yellow blossoms” from “gene that produces yellow blossoms that is advantageous for selection”. To abstract from functional details is a theory immanent question, which does not put into peril the scientific quality of the abstract concept. To use our example, the causal task that defines “gene that produces yellow blossoms” is contained in each of its sub-concepts such as “gene that produces yellow blossoms that is advantageous for selection”; and it is only a theory-immanent question which degree of abstraction or detail is scientifically appropriate to describe an entity. In order to explain what a property token has in common with a relatively broad set of other property tokens, one prefers to apply the abstract concept “gene that produces yellow blossoms”. This concept only focuses on the causal effect of yellow blossoms that makes a property token a gene that produces yellow blossoms. In order to take into account functional differences in the way in which the yellow blossoms are produced, one applies more detailed sub-concepts such as “gene that produces yellow blossoms that is advantageous for selection”. This concept also focuses on the causal effect of yellow blossoms that makes a property token a gene that produces yellow blossoms and considers

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additional functional details in the way in which yellow blossoms are produced. These functional details are potentially relevant for selection. Third, let us overview the relationship between concept and subconcept in relation to the truth-maker relation. By the truth-maker realism argument, we have already seen that entities in the world can make the application of different concepts true. There are for instance physical and biological concepts that are made true by one and the same entity. In this context, one and the same entity can also make different concepts of one and the same theory true. It is possible that one and the same entity (say e1) makes true both a more abstract description, and a more detailed description. For instance, one and the same entity can make true both “gene that produces yellow blossoms” and “gene that produces yellow blossoms that is advantageous for selection”. Fourth, let us look at our theme here in relation to law-like generalizations. An abstract law-like generalization about the causal relation between genes for yellow blossoms and the production of yellow blossoms cannot be directly deduced from a single physical law-like generalization. This is a consequence of the argument for multiple realization. However, if it is possible to construct sub-concepts based on functional differences corresponding to each type of physical realizer, it is possible to conceive more detailed functional law-like generalizations that are all about the same type of effect that defines the abstract functional concept. For instance, the sub-concept “gene that produces yellow blossoms that is advantageous for selection” figures in a law-like generalization about yellow blossoms with greater detail than the law-like generalization in which the abstract concept “gene that produces yellow blossoms” figures (cf. ‘implication of detectability’, this chapter, p. 148). From such more detailed law-like generalizations, it is possible to deduce the abstract law-like generalization by simply abstracting from the details about the production of the effect in question that distinguish the subconcept from the abstract concept. The abstract and the detailed law-like generalizations are expressed within the functional vocabulary of the same theory, the application of either the abstract or the more detailed law-like generalization gives us a theory-immanent allowance for focusing to a greater or lesser degree on the details of the causal relations. These more detailed law-like generalizations entail the abstract law-like generalization. Consequently, we do not have an argument here for eliminating the abstract law-like generalization.

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To sum up, the scientific indispensability of the abstract law-like generalizations is based on two main points: firstly, in contrast to the detailed sub-concepts or physical concepts, they bring out salient causal features that a large set of physically different entities has in common. In that respect I agree with the multiple realization argument. Second, the eliminativist conclusion some philosophers draw from the multiple realization argument can be avoided because the abstract law-like generalizations can be integrated into a network of detailed law-like generalizations in which figure sub-concepts that are co-extensional with physical concepts. Let us finally reconsider the relationship between the abstract concepts and their sub-concepts in the context of the determinatedeterminable relation.51 The functionally defined sub-concepts are more determinate concepts than the abstract concepts. What a certain abstract concept explains about a certain entity can be specified in terms of a more detailed sub-concept. Contrary to this, what a specific sub-concept explains about a certain entity cannot be specified in terms of an abstract concept. Therefore, the necessary condition of asymmetry for there being determinates and determinables is fulfilled in the case of the relationship between concepts and sub-concepts. The meaning of the abstract concepts can be reached from the sub-concept by means of a semantic analysis of the meaning of the sub-concept. After all, sub-concepts differ from their abstract concepts only in the way in which they take into account a greater number of functional aspects than are considered in more abstract concepts. This abstraction from functional details is only a theoryimmanent question because both the abstract concepts and the subconcepts are defined within the same vocabulary of one theory. This determinate-determinable relation does not characterize the relationship between sub-concepts and physical concepts. There, the relationship is a bi-conditional correlation. To put it another way, there is a nomological co-extensionality and neither the physical concepts determine the functionally defined sub-concepts, nor vice versa. The relationship between physical concepts and concepts of the special sciences cannot be of the determinate-determinable relation because the meaning of the subconcepts cannot be reached from the physical concepts by a semantic analysis of the meaning of the physical concepts. After all, the subconcepts are defined in functional terms in the vocabulary of the one of the special sciences, while the physical concepts are defined by composition in purely physical terms. 51

Cf. Yablo (1992, pp. 250-271).

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Let us recap and call this ‘relationship between concept and subconcepts’. Abstract concepts can be deduced from each of their subconcepts. If the difference between an abstract concept and its subconcepts is that the sub-concepts only consider additional functional details, it is a theory-immanent question to deduce the abstract concept from each of its sub-concepts. This deduction does not discredit the scientific status of abstract concepts because only the abstract concepts bring out what a relatively broad set of entities have functionally in common. This justifies the relevance of law-like generalizations, in which abstract concepts figure can be deduced from more detailed law-like generalizations in which, in turn, the sub-concepts figure. The missing link, namely the relationship between on the one hand the constructed physical concepts and their law-like generalizations, and on the other hand the sub-concepts and concepts of the special sciences with their more detailed and abstract law-like generalizations, will be considered in the following section, which will complete our conservative reductionist approach to the special sciences.

xxi. Epistemological reductionism by means of sub-concepts Our argument has been aimed at showing that the concepts and theories of the special sciences can be epistemologically reduced to physics in a conservative manner, which completes my reductionist account of the special sciences. In this section, I shall sum up, first of all, the main steps of this chapter in order to set out our starting point. Second, I shall interrogate the construction of physical realizer concepts of functional types. This construction is in the spirit of Hooker and Kim. Third, the construction of functional sub-concepts will be reconsidered and contrasted with Kim’s species/structure-specific reduction and the approach of the new wave reductionism that both call into question the scientific quality of the special sciences. Based on these two reconsiderations, I shall outline the conservative epistemological reduction of the theories of the special sciences to physics by means of the constructed functional sub-concepts and detailed law-like generalizations and the constructed physical concepts and law-like generalizations. This epistemological reductionism brings together the main points of Kim’s and Nagel’s models of reduction and will be contrasted with their and other recent strategies. In the context of the mentioned issues, I shall argue why

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my reductionist proposal is a complete and conservative reductionism. I shall point out how this reductionist strategy can vindicate the scientific character of the special sciences and their indispensability. First, we need to overview the steps we have taken so far. Property types are concepts, and the truth-values of the application of concepts of the special sciences supervene upon a description in terms of physical concepts (cf. ‘concept of property types’, this chapter, p. 65, and ‘supervenience of truth-values’, this chapter, p. 79). Since theories are our epistemological account of the world, since physics is complete and since physical concepts apply to any property token in the world, the epistemological reduction of the special sciences to physics is well motivated (cf. ‘concept of theories’, this chapter, p. 64, ‘completeness of physics’, chapter I, p. 24, ‘universality of physical concepts’, this chapter, p.82, and ‘motivation for epistemological reductionism’, this chapter, p.83). There are two main strategies in order to reduce epistemologically the special sciences to physics. On the one hand, there is Nagel’s model of reduction by means of bi-conditional bridge-principles, on the other hand, Kim provides a functional model of reduction (cf. ‘Nagel’s model of reduction’, this chapter, p. 89, and ‘Kim’s model of reduction’, this chapter, p. 99). But since the co-extensionality between concepts of different sciences is necessary for epistemological reductionism, the famous multiple realization argument seems to be a general argument against epistemological reductionism (cf. ‘necessity of co-extensionality for epistemological reductionism’, this chapter, p. 85, and ‘argument of multiple realization’, this chapter, p. 117). In view of that argument, Nagel’s model completely fails, and Kim’s model can only provide local reductions (cf. ‘consequences for Nagel’s model’, this chapter, p. 120, and ‘consequences for Kim’s model’, this chapter, p. 123). As we saw, the multiple realization argument also puts into question the ability of the special sciences to abstract from physical details while remaining causally explanatory (cf. ‘critique of the multiple realization argument’, this chapter, p. 133). The argument of multiple realization can be read as an argument against the reducibility of the special sciences, but also functions as an argument in favour of eliminating the special sciences from a scientific account of the world. Kim admits this consequence, and the new wave reductionism amounts to such an elimination of the special sciences. Against this background, I have found a strategy that avoids both these consequences. Any physical differences between realizers, put into focus by the multiple realization argument, lead to the possibility to detect

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these physical differences in functional terms of the special sciences (cf. ‘implication of the multiple realization argument’, this chapter, p. 131, and ‘detectability of physical differences’, this chapter, p. 138). On this basis, it is possible to construct sub-concepts of concepts of the special sciences that are co-extensional with constructed physical concepts concerning the realizers, and to construct detailed law-like generalizations of the special sciences that are co-extensional with physical law-like generalizations conceived in terms of these constructed physical concepts (cf. ‘implication of detectability’, this chapter, p. 148). Since the common functional concepts of the special sciences are abstract concepts, and sub-concepts are relatively detailed concepts, it is possible to deduce an abstract concept of the special sciences from each of its sub-concepts. In this context, it is possible to deduce abstract law-like generalizations from detailed law-like generalizations in which the sub-concepts figure. Such a deduction neither implies the elimination of the abstract concepts nor does it imply the elimination of the abstract law-like generalizations (cf. ‘relationship between concept and sub-concepts’, this chapter, p. 152). I shall consider in this section the relationship between the constructed physical concepts and the sub-concepts of the special sciences and the relationship between the constructed physical law-like generalizations and the detailed law-like generalizations of the special sciences. As already mentioned, by means of this consideration, my reductionist approach is consonant with, and implies, a conservative epistemological reductionism. Our second task is to interrogate how we construct physical concepts about realizers. Just to bear in mind, a realizer is a configuration of physical property tokens that fulfils a certain causal task – the causal task that defines a certain concept of the special sciences. In particular, a configuration of physical property tokens is a realizer in virtue of fulfilling the causal task that defines the concept in question. Given that the argument for ontological reductionism is cogent (cf. ‘token-identity qua causal efficacy and completeness’, chapter I, p. 51), any biological property token that comes under a functionally defined concept is identical with a molecular configuration that fulfils the causal task in question. For instance, any biological property token that comes under the concept “gene that produces yellow blossoms” is identical with a molecular configuration. Therefore, it is in principle possible to describe any biological property token in physical terms. For any configuration of physical property tokens it is possible to construct a physical concept that refers to all and only the physical configurations that are composed in the same

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way.52 Such a constructed concept is embedded in physics that is generally about entities such as atoms or electrons and not about entities that come under concepts of the special sciences in particular. On this basis, an entity that is a gene token for yellow blossoms comes, for instance, under the constructed physical concept “molecular configuration of type P1x” (cf. ‘Nagel’s model of reduction’, this chapter, p. 89). Let us bear in mind that much empirical research may be needed in order to find out which molecular configuration has the effect that defines the causal task in question. The term ‘realizer’ is tied to the causal task that defines a concept of the special sciences. To put it simply, it is a specific causal relation that makes a molecular configuration a realizer of a functional type (cf. ‘Kim’s model of reduction’, this chapter, p. 99).53 In this context, it is possible to construct physical law-like generalizations in which the constructed physical concepts figure. Bearing the construction of physical concepts in mind, let us, third, reconsider the construction of sub-concepts in the special sciences. It is possible within the vocabulary of the special sciences to construct functionally defined sub-concepts that are co-extensional with the mentioned physical concepts about types of realizers. Given physical differences accounting for different types of realizers, there are functional differences as well (cf. ‘detectability of physical differences’, this chapter, p. 138). It is therefore always possible to construct sub-concepts of functionally defined concepts such that each of these sub-concepts describes all and only the entities that are uniformly described by a physical concept. For instance, it is possible to construct sub-concepts of the concept “gene that produces yellow blossoms” – for example “gene that produces yellow blossoms that is advantageous for selection” – such that this sub-concept is co-extensional with a (constructed) physical concept such as “molecular configuration of type P1x” (cf. ‘implication of detectability’, this chapter, p. 148). In this context, it is possible to construct detailed law-like generalizations of the special sciences that are co-extensional with constructed physical law-like generalizations. Fourth, let us consider the epistemological reduction of sub-concepts and detailed law-like generalizations to physics. Each sub-concept is coextensional with a constructed physical concept about realizers. Thus, it is possible to establish a bridge-principle in the sense of a bi-conditional 52

Cf. Hooker (1981, pp. 49-52) who outlines in detail the construction of such physical concepts. 53 The general strategy to discover a realizer can be traced back to David Lewis. Cf. Lewis (1970, pp. 81-82).

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correlation between those concepts of different sciences, for instance between the sub-concept “gene that produces yellow blossoms that is advantageous for selection” and the physical concept “molecular configuration of type P1x”. On this basis, each law-like generalization that is couched in terms of the sub-concept “gene that produces yellow blossoms that is advantageous for selection” can be deduced from the physical law-like generalization in which the constructed concept “molecular configuration of type P1x” figures (cf. ‘Nagel’s model of reduction’, this chapter, p. 89). In the context of Kim’s model of reduction, this co-extensionality between concepts and law-like generalizations of different sciences means that it is possible to provide homogeneous reductive explanations. The physical concept “molecular configuration of type P1x” embedded in physics provides a homogeneous reductive explanation of each property token that comes under the sub-concept “gene that produces yellow blossoms that is advantageous for selection” (cf. ‘Kim’s model of reduction’, this chapter, p. 99). This is epistemological reduction of the sub-concept in question. To conclude, insofar as a biological theory only extends over such sub-concepts and detailed law-like generalizations, it can be epistemologically reduced to physics. Bearing this first result in mind, let us finally consider the scientific quality of the current special sciences – sciences that conceive abstract law-like generalizations and explanations that are about physically different entities. Clearly, the functionally defined concept “gene that produces yellow blossoms” is a concept that abstracts from possible functional differences that are based on the physical differences between the types of realizers. In this context, the abstract law-like generalization in which the concept “gene that produces yellow blossoms” figures abstracts from functional details that are only taken into account in detailed law-like generalizations in which sub-concepts such as “gene that produces yellow blossoms that is advantageous for selection” figure. However, this abstraction from functional details does not endanger the scientific validity of the abstract concepts and abstract law-like generalizations of the special sciences. Since it is always possible to conceive sub-concepts and detailed law-like generalizations within the vocabulary of the same science, this abstraction does not invite the elimination of the abstract concepts and abstract law-like generalizations. This is a crucial distinction of my model and Kim’s model of reduction, and, especially, in the light of our response to new wave reductionism. In both these positions, the elimination of the special sciences is suggested

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because these positions do not take into account the possibility to construct functional sub-concepts that are co-extensional with physical concepts (cf. ‘critique of the multiple realization argument’, this chapter, p. 133). To conclude, the scientific character of the special sciences – to focus on salient causal relations by means of single abstract concepts and abstract law-like generalizations – is secured by means of the possibility to construct sub-concepts and detailed law-like generalizations. By means of these sub-concepts and detailed law-like generalizations, both the reduction and the indispensable character of the special sciences can be justified: first, the sub-concepts (detailed law-like generalizations) are coextensional with constructed physical concepts (law-like generalizations) such that the special sciences can be reduced to physics by means of these sub-concepts (detailed law-like generalizations). Based on this, second, the theory-immanent relationship between concept and sub-concept (abstract law-like generalization and detailed law-like generalization) does not invite the elimination of the former. Furthermore, the special sciences are indispensable because they conceive salient causal features that physically different entities have in common: the abstract concepts of the special sciences bring out salient causal similarities that physics cannot express in a homogenous way. There are no physical concepts that are co-extensional with these abstract functional concepts. Consequently, there are no physical law-like generalizations that are co-extensional with the abstract law-like generalizations that are couched in terms of these concepts. Therefore, the theories of the special sciences are indispensable. That is the correct point of the multiple realization argument. However, it is wrong to conclude from the indispensability of the special sciences to their irreducibility. To make our last statement clearer, take the biological concept “gene that produces yellow blossoms” and physical concepts. The scientific character of biology – to focus on the salient causal relation between genes for yellow blossoms and yellow blossoms by means of one single abstract concept “gene that produces yellow blossoms” and abstract law-like generalizations – is secured by means of the possibility of constructing sub-concepts and detailed law-like generalizations. Here, for instance, these sub-concepts are “gene that produces yellow blossoms in a way that is advantageous for selection” (“B1”) and “gene that produces yellow blossoms in a way that is disadvantageous for selection” (“B2”). By means of these sub-concepts and detailed law-like generalizations, both the reduction and the indispensable character of biology can be justified: first, the sub-concepts “B1” and “B2” (and corresponding detailed law-like

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generalizations) are co-extensional with constructed physical concepts (law-like generalizations) as for instance “molecular configuration of type P1x” and “molecular configuration of type P1y”. Therefore, biology can be reduced to physics by means of these sub-concepts (detailed law-like generalizations). Based on this, second, the theory-immanent relationship between concept and sub-concept (abstract law-like generalization and detailed law-like generalization) does not invite the elimination of the former. Furthermore, biology is indispensable because it can conceive salient causal features, for instance between gene tokens for yellow blossoms and yellow blossoms, that physically different entities have in common: the abstract concept “gene that produces yellow blossoms” brings out salient causal similarities that physics cannot express in a homogenous way. There is no physical concept that is co-extensional with this abstract biological concept “gene that produces yellow blossoms”. Consequently, there are no physical law-like generalizations that are coextensional with the abstract law-like generalizations that are couched in terms of the biological concept “gene that produces yellow blossoms”. Therefore, biology is indispensable: From abstract concepts to physics:

From physics to abstract concepts:

abstract concept of a special science “gene that produces yellow blossoms” “B” (take into account additional functional details and construct a more detailed sub-concept)

↓ ↑

“gene that produces yellow blossoms + selective advantage”

“B1” “B2”

(co-extensional with)

 

“molecular configuration of type P1x” (that are complex concepts, constructed within physics)

(abstract from functional details considered in the sub-concept and focus on salient causal relations)

“gene that produces yellow blossoms + selective disadvantage” (co-extensional with)

“molecular configuration “P1” “P2” of type P1y” ↓ ↑

Physics

(construct complex concepts out of concepts of general physics)

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Contrary to this, in the context of the new wave reductionism and Kim’s model of reduction, the constructed species/structure-specific concepts are not expressed in purely functional terms. Instead of justifying the scientific status of the special sciences, the new wave reductionism and Kim’s model replace the abstract and general theories of the special sciences with constructed local, at most species/structure-specific physical theories, which leads towards the elimination of the abstract concepts and abstract law-like generalizations of the special sciences, ignoring their indispensable character. This is why my strategy more successfully fulfils the criterion of a conservative epistemological reductionism – contrary to any other recent reductionist position. For that reason, it is neither an argument against reductionism nor for elimination that the current special sciences consider entities that are physically different. Taking the argument for multiple realization for granted, it is not possible to provide homogeneous reductive explanations of property tokens that come under the abstract concepts of the special sciences. On the one hand, Putnam and Fodor take multiple realization as an argument in favour of the irreducibility of the special sciences. Contrary to this, my proposal sets out a strategy to reduce the special sciences to physics. On the other hand, Kim’s model of reduction and new wave reductionism conclude from multiple realization to the elimination of the scientific character of the special sciences. Contrary to this, my proposal avoids such an elimination of the special sciences. We shall call this the ‘epistemological reductionism by means of sub-concepts’ argument. The special sciences can be epistemologically reduced to physics in a conservative manner. It is possible to construct theories within physics that consider concepts and law-like generalizations that are co-extensional with sub-concepts and detailed law-like generalizations expressed in the functional vocabulary of a special science. In that manner, the scientific character of the special sciences is secured. This proposal differs from new wave reductionism and Kim’s species/structure-specific reduction because it is based on functional differences between the physical types of realizers. The elimination of the current special sciences is avoided because the abstract concepts about physically different entities and the abstract law-like generalizations expressed in terms of these concepts can in principle be integrated in a network of sub-concepts and detailed law-like generalizations that are coextensional with constructed physical concepts and law-like generalizations. For that reason, it is neither an argument against reductionism nor for elimination that the current special sciences consider

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general causal features that cannot be homogeneously explained in terms of physics.

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Résumé and transition In this chapter, a strategy for epistemological reductionism has been proposed. After an introductory framework about theories, concepts, and explanations, I considered the motivation and condition for epistemological reductionism. In this context, the two main reductionist strategies were examined: the first one can be traced back, above all, to Ernest Nagel. It is a reductionist strategy towards the special sciences by means of the famous bridge-principles. The second strategy is the so-called functional model that is developed in detail by Jaegwon Kim. However, as explained, the argument of multiple realization is a strong argument against these models as they stand. But there is a dilemma – the multiple realization argument is conceived as speaking in favour of the irreducibility of the special sciences, but it can also be conceived as suggesting the elimination of the special sciences. In order to avoid this dilemma, I introduced a new reductionist strategy that takes into account considerations about Nagel’s and Kim’s models, and the dilemma of the multiple realization argument. The core of this strategy is based on the possibility to conceive functionally sub-concepts of the special sciences that are co-extensional with physical concepts. By means of these sub-concepts, the special sciences can be epistemologically reduced to physics. This means, their elimination can be avoided and their character as indispensable scientific theories can be emphasized. Against this background, I shall consider in the following chapter the relationship between ontological and epistemological reductionism. After all, chapter two was based on ontological reductionism, and, as I have argued, epistemological reductionism is the only option to vindicate the scientific quality of the special sciences. Chapter three will advance my argument that ontological and epistemological reductionism imply each other, allowing us to formulate a complete conservative reductionism as the only coherent reductionist position.

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Complete conservative reductionism Preliminary remark In order to oppose a complete conservative reductionism, either the elimination of the scientific character of the special sciences or property dualism are the only options.

Abstract There are three parts of this chapter. In the first part, I shall consider the implications of ontological reductionism. As I shall argue, contrary to what is generally claimed, ontological reductionism implies the principled possibility of epistemological reductionism. This supports my proposed reductionist strategy of chapter two. In the second part, I shall examine the implications of epistemological reductionism, which, as is generally assumed, implies ontological reductionism. Against the background of these two parts, I shall finally consider the meaning of complete reductionism, conservative reductionism, and the limits of my proposed strategy of complete conservative reductionism.

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Implication from ontological reductionism to epistemological reductionism i.

Starting point ontological reductionism

The starting point of this part of the chapter can be captured by the following two claims: On the one hand, as we have shown in chapter one, there is a strong argument for ontological reductionism. But, as we have shown in chapter two, there exist strong arguments against the coextensionality of concepts of the special sciences with physical concepts. Let us review these two points with an eye to strengthening our reductionist strategy. First of all, any causally efficacious property token of the special sciences is identical with a configuration of physical property tokens (cf. ‘token-identity qua causal efficacy and completeness’, chapter I, p. 51). This is ontological reductionism, which we have argued for both by completeness of physics and by supervenience. On this basis, it possible to provide a reductive explanation of any property token of the special sciences in terms of physics (cf. ‘concept of explanation’, chapter II, p. 71, and ‘Kim’s model of reduction’, chapter II, p. 99). For instance, any gene token for yellow blossoms is identical with a certain molecular configuration. In order to cause yellow blossoms, the gene token in question has to be identical with a configuration of physical property tokens by completeness of physics and by supervenience. Therefore, it is possible to provide a physical explanation of this gene token. Furthermore, physics can reductively explain why the property token in question comes under the functionally defined concept “gene that produces yellow blossoms”. Second, the multiple realization argument suggests that concepts of the special sciences are generally not co-extensional with physical concepts. Property tokens that come under one concept of the special sciences come often under different physical concepts. For that reason it is not possible to correlate such concepts of the special sciences with physical concepts in a co-extensional way (cf. ‘argument of multiple realization’, chapter II, p. 117). Since the co-extensionality between concepts of different sciences is necessary for epistemological reductionism, the special sciences are generally taken to be irreducible to

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physics (cf. ‘necessity of co-extensionality for epistemological reductionism’, chapter II, p. 85, ‘consequences for Nagel’s model of reduction’, chapter II, p. 120, and ‘consequences for Kim’s model’, chapter II, p. 123). By means of abstract concepts, the special sciences are able to focus on salient homogeneous causal relations in a way that physics is not able to do. For instance, gene tokens that come under one single gene concept such as “gene that produces yellow blossoms” come under different physical concepts such as “molecular configuration of type P1” or “molecular configuration of type P2”. Therefore, it is not possible to correlate bi-conditionally the biological concept “gene that produces yellow blossoms” with a physical concept. As a result of this, biology seems to be irreducible to physics because the co-extensionality between biological concepts and physical concepts is necessary for the reduction of biology. Biology is scientifically indispensable since it can focus on salient causal relations between gene tokens and yellow blossoms in a homogeneous way. This is not possible in terms of physics. We will label this the ‘starting point ontological reductionism’. Taking the argument for ontological reductionism for granted, any property token of the special sciences can be reductively explained in terms of physics. However, the argument of multiple realization suggests that epistemological reductionism is not feasible. This is a reductionist position about property tokens, but anti-reductionist about theories, laws, and explanations.

ii.

Implication of anti-reductionism

In this section, I shall rehearse the reasoning according to which the multiple realization argument seems to lead either to the elimination of the special sciences or to the refutation of ontological reductionism. Either, the argument of multiple realization suggests the elimination of the special sciences – contrary to the intentions of those who conceived that argument. Or, the argument as an anti-reductionist argument is not compatible with ontological reductionism. Let us examine these implications in more detail. First of all, take the suggestion that we are justified in eliminating the special sciences based on the criticism of the multiple realization argument (cf. ‘critique of the multiple realization argument’, chapter II, p.133). Since it is not possible to construct physical concepts that are coextensional with concepts of the special sciences, the special sciences lose

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their scientific status. Each special science theory can then, theoretically, be replaced by physical theories that capture in a homogeneous way species/structure-specific realizers of the functional descriptions of the special science in question. This is what the proposals of Kim and new wave reductionism push us towards. Starting from ontological reductionism, the argument from multiple realization intends to establish epistemological anti-reductionism, yet ends up in the elimination of the scientific validity of the special sciences. Let us consider still another argument leading to the elimination of the special sciences. It is possible that the homogeneous character of property tokens is only brought out in terms of the special sciences and that, in those terms, what cannot be reduced is an epiphenomenon. This means, the concepts of the special sciences are about something ontological beyond physical property tokens. They are made true by property tokens that are causally impotent. This kind of property dualism is compatible with the completeness of physics and supervenience provided that one considers the property tokens of the special sciences to be causally redundant. But, by our argument for the redundancy of epiphenomena, it is not possible to take such a position in order to argue for the indispensable character of the special sciences (cf. ´redundancy of epiphenomena´, chapter I, p. 31). What is irreducible to physics as an epiphenomenon is not of any scientific interest. This suggests again the elimination of the special sciences. Second, let us consider the anti-reductionist consequences of the multiple realization argument that do not lead to eliminativism. Assume that the abstract concepts, law-like generalizations and explanations of the special sciences are scientifically indispensable. This means, the special sciences are able to focus on salient homogeneous causal relations in a manner physics is not able to do. To put it another way, there is no physical homogeneity between different types of realizers of one functional type of the special sciences. Since there is no such physical homogeneity and since nonetheless the functional theories of the special science seize salient homogeneous causal relations, these theories cannot be reduced by Kim’s strategy of local, at most species/structure-specific reductions (or by new wave reductionism). To put it another way, we start with the indispensable scientific character of the special sciences. We take the multiple realization argument to imply that neither the elimination nor the reduction of the special sciences is possible. If the special sciences capture causal relations without physics being able to capture these relations in its terms nor a

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reduction of the concepts of the special sciences to physical concepts possible, then it follows that the salient causal relations that the special sciences consider in their terms are ontologically not identical with something physical. This means, there is something ontological beyond configurations of physical property tokens. If the special sciences can neither be reduced because of the multiple realization argument nor be eliminated by means of the strategies of Kim and new wave reductionism, then there must be ontological differences between property tokens of the special sciences and configurations of physical property tokens. There are then two possibilities. Either, first, multiply realized property types of the special sciences are concepts. In this context, the concepts of the special sciences that can neither be reduced nor eliminated bring out something ontological that physical concepts cannot bring out. Therefore, the truth-makers of concepts of the special sciences differ ontologically from the truth-makers of physical concepts. This means, there is no token-identity of property tokens of the special sciences with configurations of physical property tokens. Or, second, multiply realized property types are universals that exist in the world. In this context, the property types of the special sciences differ from physical property types such that there are ontological differences. Since the second possibility obviously is opposed to ontological reductionism, let us only reconsider the first possibility (types are concepts) in relation to the completeness of physics and supervenience. Taking the causal efficacy of the property tokens of the special sciences for granted, if there is no token-identity, the consequence is ontological dualism based on either the rejection of the completeness of physics or the rejection of supervenience. Either, first, the property tokens of the special sciences have physical effects (downward causation, interactionism), and thus, the principle of the completeness of physics is violated. Or, second, there are causal effects of the property tokens of the special sciences that have only effects on other property tokens of the special sciences. In this case, we can retain the completeness of physics but must reject supervenience. There is independent variation such that again there are ontological differences between property tokens of the special sciences and configurations of physical property tokens. Let us call this ‘implication of anti-reductionism’. The multiple realization argument seems to lead either to the elimination of the special sciences or to the refutation of ontological reductionism. In the latter case, the property tokens of the special sciences are either epiphenomena,

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suggesting the elimination of the special sciences, or the completeness of physics or supervenience is false. To conclude, the multiple realization argument as an anti-reductionist argument leads either to the elimination of the special sciences or it leads to the rejection of ontological reductionism.

iii.

Conclusion

Ontological reductionism is not compatible with epistemological antireductionism. Taking ontological reductionism for granted, either the special sciences can be reduced to physics, or their elimination is suggested. It is not possible that the scientific character of the special sciences is indispensable without the theories of the special sciences being reducible to physics or ontological reductionism being false. Provided that my chapter two argument holds, a reductionist strategy is available that combines the indispensable scientific character of the special sciences with their reducibility to physics. Against the background of this part of the chapter, my proposed strategy seems to be the only strategy that avoids the elimination of the special sciences, while taking into account the causal argument for ontological reductionism. It thus steers a middle course between hard-core physicalist eliminativism and ontological dualism.

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Implication from epistemological reductionism to ontological reductionism iv.

Starting point epistemological reductionism

The starting point of this part of the chapter can be captured by the following two claims: first, the co-extensionality between concepts of different sciences is a necessary requirement for epistemological reductionism. Second, the completeness of physics is what motivates epistemological reductionism. Let us reconsider these issues in more detail. First, let us reconsider the necessity of the co-extensionality of concepts for a conservative epistemological reductionism. Only on the basis of the co-extensionality between concepts of different sciences is it possible to deduce law-like generalizations of the special sciences from physical law-like generalizations (cf. ‘necessity of co-extensionality for epistemological reductionism’, chapter II, p. 85). Second, let us examine the role of the completeness of physics for epistemological reductionism. The aim is to link systematically the special sciences with physics such that any explanation and law-like generalization of the special sciences can be deduced from physical (reductive) explanations and law-like generalizations. To put it another way, epistemological reductionism aims in the last resort at explaining in a more complete manner what concepts of the special sciences (embedded in a theory) only explain in a relatively incomplete manner. Given the incompleteness of the special sciences (cf. p. 29), the concepts of the special sciences cannot outline the corresponding entities completely. In order to explain, the special sciences often have recourse to, in the last resort, physical concepts. Since only physics is taken to be complete, it is this completeness of physics that motivates epistemological reductionism (cf. ‘completeness of physics’, chapter I, p. 24, and ‘motivation for epistemological reductionism’, chapter II, p. 83). More precisely, the completeness of physics motivates the deduction of incomplete law-like generalizations of the special sciences from complete physical law-like generalizations and homogeneous reductive explanations of property

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tokens that are only incompletely explained in terms of the special sciences. We will calling this the ‘starting point epistemological reductionism’. Any strategy of epistemological reductionism requires the co-extensionality between concepts of different sciences in order to deduce law-like generalizations. In addition to this, epistemological reductionism is motivated by the fact that the sciences differ in their causal, nomological, and explanatory completeness. In this context, it is in the last resort the completeness of physics that motivates the epistemological reduction of the special sciences.

v.

Incompatibility of epistemological reductionism with property dualism

Ontological parsimony tells us that epistemological reductionism should suggest ontological reductionism. Moreover, the rejection of ontological reductionism is not compatible with epistemological reductionism. In this section, we are going to look at why the deduction of law-like generalizations of the special sciences from physical law-like generalizations is not possible in the case of property dualism. First, let us see how epistemological reductionism suggests ontological reductionism. The concepts of the special sciences can be shaped in such a way that we get to concepts that have the same extension as appropriate physical concepts (cf. ‘necessity of co-extensionality for epistemological reductionism’, chapter II, p. 85). Furthermore, any lawlike generalization and explanation in terms of the special sciences can be deduced from physical law-like generalizations and explanations. In this context, it is only an exercise in ontological parsimony to suggest that property tokens of the special sciences are ontologically identical with configurations of physical property tokens. Leaving aside epiphenomenalism because of its causal, nomological and explanatory redundancy, ontological parsimony is also an argument against parallelism (cf. ‘redundancy of epiphenomena’, chapter I, p. 31). To claim that there are perfectly parallel ontological levels of physics and the special sciences seems to be spurious because any explanation and law-like generalization of the special sciences can be deduced from physical explanations and law-like generalizations (whereas it is not possible to deduce the physical law-like generalizations and explanations from law-like generalizations and explanations of the special sciences).

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Second, let us look at the claims of ontological dualism. Whether or not we take the completeness of physics for granted, ontological dualism would force us to take the property tokens of the special sciences to be different from physical property tokens. There are different truth-makers for the application of physical concepts and concepts of the special sciences. For instance, the concept “gene that produces yellow blossoms” does not apply to entities that are referred to by means of physical concepts. There are ontological differences between a gene token for yellow blossoms and a token of a molecular configuration such as of type P1. Let us examine the implication of such ontological differences. Ontological differences imply causal differences. It is not possible that two property tokens manifest ontological differences without there being causal differences as well. To exemplify this, examine a situation in which a gene token for yellow blossoms b 1x causes yellow blossoms b2x. Let us furthermore suppose for this situation a token of the molecular configuration of type P1, p 1x, that causes a token of the molecular configuration of type P2, p2x. Such a situation is quite compatible with the co-extensionality of concepts of different sciences. Up to this point, the biological concept “gene that produces yellow blossoms” can be coextensional with the physical concept “molecular configuration of type P1” and the concept “yellow blossoms” can be co-extensional with the concept “molecular configuration of type P2”. Let us now assume a situation in which, contrary to the previous situation, a gene token for yellow blossoms b 1y does not cause yellow blossoms b2y. There are exceptional conditions such that b 1y cannot exercise its causal power. However, in this situation, given the ontological difference between b1y and p 1y and given that this difference implies a causal difference, it is possible that the causal relation from the token of the molecular configuration of type P1, p 1y, to the token of the molecular configuration of type P2, p2y, proceeds as in the previous situation. Since the gene tokens for yellow blossoms and the tokens of molecular configurations of type P1 differ causally, there always exists the possibility of an environment in which the causal efficacy of the one can be affected without affecting the causal efficacy of the other property token. For that reason it is possible that there are conditions such that gene tokens for yellow blossoms do not cause yellow blossoms, while tokens of molecular configurations of type P1 cause tokens of molecular configurations of type P2, or vice versa. As a result of such possible environments, it is not possible that the biological concept “yellow blossoms” – or any of its

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biological sub-concepts – is co-extensional with “molecular configuration of type P2”. In general, ontological differences exclude the coextensionality of concepts of different sciences. This argument is in the spirit of chapter two (cf. ‘detectability of physical differences’, chapter II, p. 138). Call this the argument of the ‘incompatibility of epistemological reductionism with property dualism’. Leaving aside epiphenomenalism, the argument of ontological parsimony suggests token-identity in any case of epistemological reductionism. Moreover, epistemological reductionism is not compatible with property dualism. The rejection of ontological reductionism means that the concepts of different sciences apply to property tokens that are ontologically different. That is to say that there are causal differences between the property tokens that are considered in terms of different sciences. Thus, it is always possible to conceive environments in which the causal efficacy of one property token is affected while the causal efficacy of other property tokens considered in terms of another science will not be. For that reason, the concepts that the relevant sciences employ cannot be nomologically co-extensional. To conclude, the rejection of ontological reductionism is not compatible with the nomological co-extensionality of the concepts of different sciences.

vi.

Conclusion

Epistemological reductionism implies ontological reductionism. Epistemological reductionism is not compatible with the rejection of ontological reductionism. Provided that epistemological reductionism necessitates the co-extensionality of the concepts of different sciences, it implies ontological reductionism. In order to deduce explanations and lawlike generalizations ontological differences between the referents of the concepts of different sciences have to be excluded.

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Complete conservative reductionism vii. What complete reductionism means Complete reductionism is both ontological reductionism and epistemological reductionism. Since ontological reductionism implies epistemological reductionism, and vice versa, complete reductionism is the only coherent reductionist position. Let us reconsider the implications from ontological reductionism to epistemological reductionism, and vice versa, and examine how we can claim complete reductionism be considered the only coherent reductionist position. First of all, ontological reductionism implies epistemological reductionism. Taking ontological reductionism for granted, either the special sciences can be reduced to physics, or their elimination is implied. The scientific character of the special sciences cannot be indispensable if the theories of the special sciences being reducible to physics or ontological reductionism are not true (cf. ‘starting point ontological reductionism, this chapter, p. 168, ‘implication of anti-reductionism’, this chapter, p. 169, and ‘conclusion’, this chapter, p. 172). Second, epistemological reductionism implies ontological reductionism. Provided that epistemological reductionism is based on the co-extensionality of the concepts of different sciences, it implies ontological reductionism. In order to deduce explanations and law-like generalizations ontological differences between the referents of the concepts of different sciences have to be excluded (cf. ‘starting point epistemological reductionism’, this chapter, p. 173, ‘incompatibility of epistemological reductionism with property dualism’, this chapter, p. 174, and ‘conclusion’, this chapter, p. 176). Finally, let us consider complete reductionism – the combination of ontological reductionism and epistemological reductionism. As argued above, both ontological reductionism implies epistemological reductionism, and epistemological reductionism implies ontological reductionism. For that reason, any reductionist position has to be a complete reductionism. Ontological reductionism is coherent only if epistemological reductionism is valid, and vice versa, which is the logical background to the claim that complete reductionism is the only coherent reductionist position.

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viii. What conservative reductionism means Conservative reductionism does not lead to the elimination of the special sciences, nor to the elimination of the property tokens, nor to the elimination of the concepts of the special sciences. It acknowledges the descriptions, law-like generalizations and explanations of the special sciences as being true and of scientific value. Let us reconsider the arguments against eliminativism and examine their compatibility with the proposed reductionist strategy. First, let us look at the criterion for conservativism with respect to property tokens of the special sciences. To put it another way, let us examine the argument against the elimination of property tokens of the special sciences. Causal efficacy of a property token is an argument against its elimination. If, for instance, a gene token for yellow blossoms causes yellow blossoms, this causal relation is an argument for the existence of the gene token in question. Thus, there is a causal argument for the existence of property tokens. In the context of chapter one, this causal efficacy of the property tokens of the special science leads to an argument for the identity of these property tokens with configurations of physical property tokens. In other words, the causal efficacy of property tokens of the special sciences is only compatible with the completeness of physics and the supervenience principle if there is ontological reductionism (cf. ‘token-identity qua causal efficacy and completeness’, chapter I, p. 51). By this move, we have eliminated any candidate except ontological reductionism as the causal argument in favour of the existence of property tokens of the special sciences. Ontological reductionism thus avoids the elimination of the property tokens of the special sciences. Second, let us consider the criterion for being conservative with respect to concepts of the special sciences. To put it another way, let us examine the argument against the elimination of the concepts of the special sciences. Without any doubt, the concept in question has to be true in order to avoid its elimination. Thus, there has to be a truth-maker for the application of a certain concept – there have to be entities in the world that make true concepts of the special sciences. It is generally assumed that there are truth-makers for concepts of the special sciences. However, there also is always a complete physical description and explanation of any causally efficacious property token of the special sciences possible: any causally efficacious property token of the special sciences must be identical with a certain configuration of physical property tokens, and this configuration is completely explained in terms of physics. Therefore, from

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a scientific point of view it seems that the concepts of the special sciences are dispensable. Such a dispensability of the concepts of the special sciences implies they can be eliminated from scientific explanations. In this context, the argument of multiple realization is an argument in favour of the indispensable scientific character of the concepts of the special sciences. After all, there are salient similarities among causal relations in the world that only the special sciences bring out in a homogeneous way – in a way physics is not able to bring them out. There are no physical concepts that can bring out homogeneously the salient similarities among causal relations that are generally considered in terms of the special sciences. However, as we have seen, the argument of multiple realization can be interpreted to imply the elimination of the special sciences (cf. ‘critique of the multiple realization argument’, chapter II, p. 133). After all, both Kim’s species/structure-specific reduction and the new wave reductionism lead to the elimination of the concepts of the special sciences because they are regarded as being scientifically spurious. To conclude, the logic of these arguments for the scientific indispensability of the concepts of the special sciences via their irreducibility implies just the opposite, their elimination. Thirdly, against this background, let us look at an argument that avoids the paradox mentioned above. This argument presents a reductionist strategy which, at the same time, demonstrates the indispensable scientific character of the concepts of the special sciences. As explained in chapter two, it is always possible to establish a coextensionality between constructed sub-concepts of the special sciences and constructed physical concepts (cf. ‘detectability of physical differences’, chapter II, p. 138, and ‘implication of detectability’, chapter II, p. 148). Thus, there are, for instance, constructed biological subconcepts that are only defined in biological terms, but that are nevertheless nomologically co-extensional with physical concepts. On this basis, we gain two theses: one, the scientific character of these sub-concepts is secured because they are systematically linked with physical concepts, and two, physics retains its fundamental character among the sciences: it alone is complete, universal, and it is ultimately more detailed. Therefore, once again, from a scientific point of view, the physical concepts are preferable with respect to the concepts of the special sciences. In this connection, the reductionist model of Nagel shows that the concepts and explanations of the special sciences are true, but it fails to establish their indispensable character, leaving open the possibility of the complete elimination of the special sciences. To conclude, if any concept of the special sciences is co-

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extensional with a physical concept, the special sciences can in principle be dispensed with. At this point, let us go back to the relationship between concepts and their sub-concepts in my reductionist strategy as introduced in chapter two. As already explained, the relationship between a concept of the special sciences and its sub-concepts is a theory-immanent question of abstraction (cf. ‘relationship between concept and sub-concepts’, chapter II, p. 152). The relationship between an abstract concept and its sub-concepts can be seen as integrating the abstract concept in its sub-concepts such that the scientific quality of the abstract concept is not put into peril: first, the abstract concept and its sub-concepts are formulated within the vocabulary of the same theory; second, the only difference between an abstract concept and its sub-concepts is the degree of abstraction from functional details; finally, this abstraction is intelligible within the theory in question – it is wholly a theory-immanent matter for the scientist to focus on her preferred functional details. In other words, we avoid eliminating the abstract concepts since the sub-concepts entail the causal tasks defining those same abstract concepts in such a way that the abstract concepts maintain their scientific respectability. On that basis, the abstract concepts of the special sciences are indispensable, inasmuch as they bring out salient functional features that a relatively broad set of entities has in common, and there are no physical concepts that are co-extensional with these abstract functional concepts. To conclude, the proposed reductionist strategy by means of the construction of sub-concepts establishes the scientific indispensability of the abstract concepts of the special sciences. This reductionist strategy is compatible with the fact that the abstract concepts of the special sciences are not co-extensional with physical concepts (multiple realization). Conservative reductionism proposes that it is possible to formulate a coherent system of our knowledge to which the abstract concepts of the special sciences make an indispensable contribution. These concepts abstract from functional details in order to bring out salient homogeneities between a broader set of entities. This is an abstraction from ontological details that is not possible in terms of physics. But this abstraction from ontological details is compatible with the completeness of physics, epistemological reductionism, and ontological reductionism. Let us bear in mind that conservative epistemological reductionism implies a conservative ontological reductionism so that the existence of the property tokens of the special sciences is not called into question (cf. ‘starting point epistemological reductionism’, this chapter, p. 173,

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‘incompatibility of epistemological reductionism with property dualism’, this chapter, p. 174, and ‘conclusion’, this chapter, p. 176). Our goal has been reached, here: given the completeness of physics and the supervenience principle, we thus are able to justify the existence of the property tokens of the special sciences by showing how the theories of the special sciences are reducible to physics in a conservative manner. This reductionist strategy seems to be the only viable argument available against the elimination of the property tokens of the special sciences, and so, by implication, of the special sciences.

ix.

The limits of the sub-concept strategy

As we have seen, the abstract concepts of the special sciences are not coextensional with physical concepts, which is the reason physics cannot provide homogeneous reductive explanations in the way the special sciences are able to do. This is the limit of my reductionist strategy and the reason why this strategy has to rely on functional sub-concepts. But this limit then tells us why the special sciences are indispensable, so that the reductionism set out here is conservative. Moreover, only this strategy can justify the scientific indispensability of the special sciences if we assume the completeness of physics. After all, the reductionist strategy set out here does not argue against multiple realization, but encompasses it, only then mounting an argument against both the anti-reductionist and the eliminativist consequences that have been derived from the multiple realization thesis. Although the abstract functional concepts are not co-extensional with physical concepts, it is possible to reduce the special sciences to physics. As explained in chapter two, it is possible to construct functionally defined sub-concepts in any case of multiple realization, and these sub-concepts of the special sciences are nomologically coextensional with physical concepts. Furthermore, the relationship between the abstract concepts and their sub-concepts is a theory-immanent question of abstraction. Therefore, the scientific indispensability of the special sciences fits into a reductionist approach. This is complete conservative reductionism.

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Résumé and transition to the biological part This chapter tried, above all, to connect the arguments of the first and the second chapter. Taking for granted the causal argument for ontological reductionism of chapter one, and taking for granted that any anti-reductionist strategy with respect to the special sciences ends up in the elimination of the special sciences (dilemma of the multiple realization argument), a complete and conservative reductionist strategy seems to be the only feasible option. This means, the special sciences can be, in principle, conservatively reduced to physics. In the next part of this work, I shall consider a concrete case in a still ongoing debate – the relationship between classical and molecular genetics. In this context, my proposed general reductionist strategy will be applied to a debate that contains also a historical dimension. After all, molecular genetics has developed out of classical genetics and its concepts about heredity and genes. I shall begin this biological part with a historical and systematic framework where my strategy will be briefly outlined. Against this background, both classical and molecular genetics will be considered in the context of their similarities, differences, and dependencies that, as we will see, suggest a reductionist approach. In the final section, such a reductionist approach will be outlined in detail, and possible objections will be considered. In the end, I shall give a summary and perspective that is linked to the general part and general issues in the philosophy of science.

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Historical framework54

In the year 1905, the British scientist William Bateson coined the term “genetics” (from the Greek; means ‘give birth’) in a personal letter to Adam Sedgwick. The experiments of Mendel of 1865 had recently been rediscovered and confirmed independently by three biologists, which lead to an enormous increase of scientific research in biology on the field of heredity, evolution, and development. It was in this context that Bateson introduced the term “genetics” publicly at an international conference in London in 1906 in order to describe this new field of research: genetics as the science of genes, heredity, and the variation of organisms. Let us begin by briefly giving a sketch of the development of genetics, from Mendel’s experiments through the first half of the 20th century, in order to frame the philosophical debate about the relationship between classical genetics and molecular genetics. From 1856-1863, the monk Gregor Johann Mendel (1822-1884) did experiments with pea plants in order to research the problem of heredity. He had chosen the pea plant Pisum sativum as his experimental object because it was easy to culture, control, and manipulate its pollination. There are obvious differences between the traits of the plants, such as that between white and red blossoms of the peas, or between plants bearing yellow or green seeds. In his experiments, Mendel discovered the so-called dominance in pairs of related characters and their constant 3:1 ratio with respect to recessive characters. In order to illustrate this important discovery, let us consider the related pair of the colour of the peas seeds: either the peas seeds are yellow, or they are green. In this context, Mendel observed that the yellow colour of peas seeds is dominant with respect to the green colour such that 75% of the peas possess yellow peas seeds (3:1 ratio). In order to explain this result, Mendel postulated so-called factors or elements in each pea. These factors or elements were later called “genes”. In the course of his experiment, Mendel discovered the rule of independent assortment (or segregation). By crossing pea plants with two different character pairs such as peas that are tall and possess yellow seeds with peas that are short and possess green seeds, he observed a 9:3:3:1 54

My historical framework is generally in the spirit of Allan (1985), Darden (1991 and 2005), Fisher (1936), Olby (1990), Rheinberger (2004), Stern & Sherwood (1966) and Weber (1998).

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ratio among the offspring. Once again, Mendel explained this result by postulating factors or elements that assort independently. In fact, the essential results are formulated in the famous Mendelian laws of heredity – the law of segregation, and the law of independent assortment. Let us look at those laws. The law of segregation describes the inheritance of the factors or elements from a so-called P generation to the so-called F1 and F2 generation. While in the P generation, 50% of the pea plants yield, say, yellow seeds, and 50% yield green seeds, in the following F1 generation, only the yellow seeds occur. This is the dominance of the yellow trait with respect to the green one. Nonetheless, in the then following F2 generation, the green colour reoccurs in the phenotype. Here, 75% of the pea plants possess yellow pea seeds, but 25% possess green pea seeds. The law of independent assortment states that given traits (yellow and green pea seeds for instance) assort independently from other traits and their segregation as described in the previous law. This means, if we consider both the colour of the seeds and the colour of the blossoms, in each case the 3:1 remains and the combination of both ends up in 9:3:3:1 ratio. Nine pea plants out of 17 possess yellow seeds and red blossoms, 3 possess yellow seeds and white blossoms, 3 possess green seeds and red blossoms, and only 1 possesses green seeds and white blossoms. To sum up, Mendel traced the inheritance patterns of certain characters in peas and demonstrated that they could be described mathematically. In 1865, he presented his results to the Brunn Natural History Society. Thus, his results became published – but they remained unappreciated until 1900.55 In 1900, the Dutch botanist Hugo Marie de Vries (1848-1935), the German biologist and geneticist Carl Erich Franz Joseph Correns (18651933), and the Austrian agronomist Erich Tschermak-Seysenegg (18711962) independently rediscovered and reconfirmed the regularities in the transmission of characters from parents to offspring presented by Mendel in 1865. Together with publications of other biologists, the English translation of Mendel’s work by the leading British geneticist William Bateson (1861-1926) created the public knowledge of Mendel’s experiments, results, and explanations.56 Based on this rediscovery, it was Bateson in 1905 who, as we saw, named this new working field of biology “genetics”. As an advocate for promoting knowledge about this new 55

Mendel (1865). De Vries (1901 and 1903), Correns (1900a and 1900b), and Tschermak-Seysenegg (1900).

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research field, he also coined new terms such as “homozygote”, “heterozygote”, or “allelomorphs” that became later known under the abbreviation “alleles”. It is probably due to him that Mendelism became a field of research. This means, Mendel’s experiments, method, results, postulates and explanations concerning heredity were converted into a new line of research – genetics. In 1909, the Danish geneticist William Johannsen (1857-1927) who collaborated with Bateson clarified the difference between the nowadays well-known terms “genotype” and “phenotype” that do not appear as such in the work of Mendel. Taking this as one of the most famous examples, one may state that the Mendelian terminology was often either replaced or clarified in the early years after the rediscovery of his experiments in 1900. Let me sum up. The genotype are all the genes of a certain organism. These genes cause the phenotype of that organism – the observable character of the organism in question. For each phenotype, one postulates a gene in form of two alleles. If the two alleles in question are identical, the organism in question is homozygote with respect to this gene. If, however, there are differences between two alleles of one gene in a given organism, this organism is called heterozygote with respect to the gene in question. Let me consider an organism that is heterozygote with respect to, for instance, the colour of the peas seeds. In this case, only the dominant allele will produce a phenotypic effect. In the case of peas seeds, the pea plant will possess yellow peas seeds because the allele for yellow peas seeds is dominant with respect to the allele for green peas seeds. In the same manner, it is possible to reformulate the second law of Mendel – the independent segregation of alleles of different genes. This was the state of the art in the early years of the 20th century. Let me now focus on the development that led to the formulation of classical genetics – a genetic theory that takes into account both the scientific progress in cytology, embryology and evolutionary biology, and that is sufficiently complete to make intelligible the close relation between development, evolution, and heredity. In 1908 and the following years, Thomas Hunt Morgan (1866-1945) and his research group worked with the fruit fly Drosophila melanogaster for which Morgan became very famous. Morgan, who is sometimes called “Lord of the flies”, studied under William Keith Brooks (1848-1908), a prominent embryologist and morphologist. In Morgan’s research group, there were gifted students – in particular Alfred Henry Sturtevant (18911871), Calvin Blackman Bridges (1889-1938), and Hermann Joseph Muller (1890-1967) who became very famous during their collaboration

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with Morgan and later on.57 Apart from this fruitful cooperation, Morgan was inspired by the chromosome theory of Mendelian heredity postulated by the German biologist Theodor Heinrich Boveri (1862-1915) and the American biologist Walter Stanborough Sutton (1877-1916). They both argued independently of each other in favour of regarding chromosomes as carrier of hereditary material in 1903-04.58 This chromosome theory was supported by an additional observation of the confirmation of Mendel’s results by de Vries, Correns, and Tschermak-Seysenegg: sometimes certain alleles that are taken to cause a certain phenotypic effect behaved as if they were linked. This result could be explained by the thesis of Boveri and Sutton that such linked alleles were located together on a certain chromosome. To put it another way, Sutton and Boveri combined genetic research with cytological research.59 It should be noted that for Morgan, as well as his famous European colleagues, theorizers August Weismann (18341914) and Ernst Haeckel (1834-1919), the problems of development, evolution, and heredity have to be considered together. But since the problems as a uniform set were not solved by the then-prevailing theories of evolution and heredity, Morgan was critical of these theories.60 Mendel’s famous laws, the chromosome theory of Boveri & Sutton, and Darwin’s theory of natural selection were theories that failed to solve the problem of development, evolution, and heredity. Let me add that, against the background of, for instance, the discovery of macro mutations like the ones de Vries61 had found in his experiments, it was Hans Driesch (18671941) who influenced Morgan to turn to experimental biology in order to solve the problems afflicting the three then-prevailing theories.

57

Cf. Sturtevant (1913), Bridges (1914, 1916, 1917, 1919, and 1921), Muller (1922 and 1927), and the corporate paper of Morgan, Sturtevant, Muller, and Bridges (1915) of that time. 58 Cf. Boveri (1904) and Sutton (1903). Let me note that by the late nineteenth century, chromosomes as bodies within the nuclei of cells had been already identified by cytologists who had also investigated their behaviour during cell division and fertilization. For instance, cf. Wilson (1896) who was later on a colleague of Morgan at Columbia University and the teacher of Sutton. 59 Cf. Darden & Maull (1977, pp. 51-54) who take the chromosome theory of Mendelian heredity as a so-called interfield-theory – a theory that connects two different fields of research that map with respect to their research objects or parts of it. 60 Cf. Allen (1985) for a good retrospective on Morgan’s ideas and objections that concern the then-prevailing theories and biologists. 61 Cf. de Vries (1901 and 1903).

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In 1910, Driesch’s advice to Morgan paid off when Morgan and his research group found the famous white-eyed mutation in the fruit fly: a male fly that had white rather than the usual red eyes. Due to this mutation, Morgan and his research group discovered a linkage among certain groups of genes allowing the second law of Mendel – the law of independent assortment – to be redefined. There was a proof of sex linkage that confirmed the results of de Vries, Correns, and Tschermak-Seysenegg supporting the chromosome theory of Boveri and Sutton. The white-eyed mutation, or better its allele, is linked to the sex of the fruit fly because it lies on the same chromosome. Advancing further, Morgan and his research group discovered another sex-linked mutant, the so-called crossing-over – a reciprocal exchange of genetic material between nonsister chromatids (parts of homologue chromosomes) during prophase I in meiosis (reduction division). By means of these recombination rates, it was possible to calculate the distance between genes and thus to construct a gene map.62 Genes, and by this we mean their alleles, which assort relatively dependently on each other lie very close on the same chromosome while genes that assort relatively independent from each other either lie at a distance on the same chromosome or on different chromosomes. Furthermore, Morgan and his associates redefined the “unit-character” of genes since they recognized that there is a so-called many-to-many relation between genes and phenotypic effects. Bateson, for instance, believed in a so-called one-to-one relation between each gene and phenotypic effect. The period of Morgan can be characterized by means of his famous statement in 1926 that genes lie in a line like beads on a string. Morgan’s accomplishment was to formulate a gene theory that demonstrated the heredity of genes and their impact of phenotypic differences in a comprehensive manner.63 Thus, even if it was clear to Morgan and Muller64 that the problem of development, evolution, and heredity was not solved by their experiments, one may take the results of Morgan and his group as establishing a comprehensive genetic theory – classical genetics. This theory is, in a nutshell, a mathematical description of the heredity of genes, the linkage of the heredity of genes given that they are lying on the 62

Cf. Sturtevant (1913) who made the first genetic map of a chromosome, and cf. Morgan et al. (1915). Cf. Weber (1998) who considers the importance of gene mappings for classical genetics. 63 Cf. Morgan (especially 1910, 1919, and 1926) and Morgan et al. (1915). 64 In particular Muller (1922).

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same chromosome. Hence, it establishes a connection of the more or less pure formal characterization of genes in terms of Mendel, de Vries, Correns, Thermak-Seysenegg, etc. with the more material approach of Boveri & Sutton, etc. Against this background, I shall now focus on the development of genetics until the discovery of DNA as the carrier of genetic information, the overall goal of which was to complete Morgan’s and Muller’s reductionist project of founding genetic research and explanation on more and more basic sciences such as physics and chemistry.65 Recognizing the results and the approach of the Morgan group, Sir Ronald Aylmer Fisher (1890-1962)66, the American geneticist Sewall Green Wright (1889-1988)67 and the British geneticist and evolutionary biologist John Burdon Sunderson Haldane (1892-1964)68 redefined evolution as a change of gene frequencies in the gene pool of a population in the 1930s and 1940s. This hypothesis is what is generally called the evolutionary synthesis.69 This synthesis is essentially an elaboration on mathematical models describing the effects like mutation or selection for the population in question. To sum up this development in the context of Morgan’s project, Fisher, Wright, and Haldane are the founders of population genetics. They established an explanatory link between the heredity of genes, mutations, and evolution. In 1941, George Wells Beadle (1903-1989) and Edward Lawrie Tatum (1909-1975) published their key experiment that involved exposing the bread mold Neurospra crassa to x-rays in order to cause mutations. By means of this experiment, Beadle and Tatum showed that these mutations caused changes in specific enzymes involved in metabolic pathways. This experiment led them to propose a direct link between genes and enzymatic reactions – the famous one-gene-one-enzyme hypothesis.70 They showed that genes code for enzymes – which became one of the tenants of the central dogma of genetics. Let me note that the gene, even far from being a simple notion or simple entity, was still essentially defined as an abstract or formal unit – a unit of transmission and function (Mendel) or a unit of recombination and mutation (Morgan et al.). However, the physical explanation for the replicative power of genes was still unknown, even if 65

Compare in particular Muller (1936) who argued that the problems in genetics could only be solved in collaboration with chemists and physicists. 66 Fisher (1930). 67 Wright (1931) 68 Haldane (1932). 69 Cf. Lewontin (1981). 70 Beadle & Tatum (1941).

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this gap did not hinder Morgan, Muller and Beadly & Tatum from trying to discover the physical base of development, evolution, and heredity. This changed in the early 40s. In 1944, the Canadian-born American physicist and medical researcher Oswald Theordore Avery (1877-1955), the Canadian-American geneticist Colin McLeod (1909-1972), and the American geneticist Maclyn McCarty (1911-2005) isolated DNA as genetic material.71 This discovery was confirmed later on by the American bacteriologist Alfred Day Hershey (1908-1997) and his laboratory assistant Marta Cowles Chase (1927-2003) in 1952.72 The famous Hershey-Chase experiment proved the genetic information of phages to be DNA. During that time, in 1950, the Austrian biochemist Erwin Chargaff (1905-2002) showed that the four nucleotides in nucleic acids are not present in stable proportions. He formulated the general rule that the nucleotide bases Adenine and Thymine always remain in equal proportions – and so do the nucleotide bases Cytosine and Guanine.73 Let me sum up this history as follows: from the classical period of genetics, in which was discovered the abstract mathematical descriptions of the heredity of genes, their relative distance on chromosomes, the impacts on populations etc., gave way to molecular genetics, which concentrated on the physical, molecular structure of the gene. This was the context in which the double helical structure of DNA was discovered in 1953. With the help of the British physical chemist and crystallographer Rosalind Franklin (1920-1958) and the New Zealand-born British physicist Maurice Hugh Frederick Wilkins (1916-2004), the American scientist James Dewey Watson (born 1928) and the English scientist Francis Harry Compton Crick (1916-2004) together discovered the structure of the DNA molecule as the carrier of genetic information.74 Watson & Crick’s work was mainly based on chemical information about base composition of the DNA (by Chargaff), on the data from Franklin’s and Wilkin’s experiments using x-ray crystallography, and on mechanical model buildings developed by the American quantum chemist Linus Carl Pauling (1901-1994). The result of the most famous discovery in the history of genetics is the following: DNA is a nucleic acid double strand whose four bases form complementary pairs such that the base adenine always pairs with the base thymine, and the base guanine always pairs with the base cytosine 71

Avery, McLeod & McCarty (1944). Compare also McCarty’s fifty-year retrospective on DNA (McCarty 1995). 72 Hershey and Chase (1952). 73 Chargaff (1950). 74 Watson & Crick (1953a and 1953b). Compare furthermore Watson & Crick (1954).

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(because of the mentioned discovery of Chargaff). By means of this quite simple picture, the mechanism of duplication, and insofar heredity, became intelligible: In order to create two identical helices from one, it would suffice to open the strands of the original double helix and to synthesize two new strands each of which is complementary of the separated strands respectively. This fact proved that the DNA molecule possesses the characteristics that were expected from a molecule serving as a heredity unit. In the context of this important discovery and the establishing of the more and more physical, chemical and molecular methods, the American physicist and biologist Seymour Benzer (born 1921) discovered the fine structure of a bacteriophage gene in 1955.75 Due to this work, Benzer laid down the groundwork for decades of mutation analysis and genetic engineering. This work later helped to establish the triplet code of DNA. Before that, in 1961, the British biologist Sydney Brenner (born 1927) postulated together with the French biologist François Jacob (born 1920) and the American geneticist and molecular biologist Matthew Stanley Meselson (born 1930) the so-called one-gene-one-ribosome-one-enzyme hypothesis.76 To put it another way, they demonstrated that ribosomal RNA molecules are stable – which later proved the existence of mRNA. These RNA molecules function as intermediates between the genetic information of the DNA and their effects on organisms to produce enzymes. Let’s briefly sketch out the picture of the gene generated by the discoveries of these first years after the discovery of the structure of the DNA in order to show the development. Genes are sequences of DNA molecules. A gene in form of a certain sequence of DNA molecules codes for a sequence of ribosomal RNA molecules. This mechanism is called transcription. This sequence of RNA molecules codes for a sequence of amino acids that constitute an enzyme. This mechanism is called translation. This is the underlying causal relationship connecting the genotype to the phenotype of an organism, and it makes us understand the difference between organisms. Furthermore, as already mentioned, the structure of DNA makes intelligible its duplication. This mechanism is called replication. Since 1953, all research on the problem of development, evolution, and heredity is fundamentally based on molecular biology. In this context, let me now sketch out certain further important discoveries of molecular genetics in order to complete my historical 75 76

Benzer (1955). Brenner, Jacob & Meselson (1961).

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introduction to the development of genetics. This introduction to the historical background of the developments in genetics aims to make intelligible any reductionist approach to classical genetics from a molecular point of view. Let me thus continue with Brenner, who, in general, made important contributions to the field of molecular biology in the 1960s, notably in the elucidation of the triplet code of enzyme translation (one triplet of RNA bases code for a certain amino acid of which enzymes are composed). Brenner then focussed on establishing Caenorhabditis elegans as a model organism for the investigation of animal development, including neural development, because this very small soil roundworm is easy to grow in bulk populations, and turned out be quite convenient for genetic analysis. Apart from that, Meselson’s research was important in showing how DNA replicates, recombines and is repaired in cells. Meselson, having studied under Pauling who assigned him to work on x-ray crystallography, had showed already in 1958 together with Franklin Stahl (born 1922) that DNA replicates semi-conservatively.77 This famous Meselson-Stahl experiment took Escherichia coli as model organism. Escherichia coli was grown in the presence of the nitrogen isotope nitrogen-15, which was then switched to be grown with normal nitrogen, nitrogen-14. When they extracted the DNA using density centrifugation Meselson and Stahl found three types of DNA – one containing nitrogen-15, one containing nitrogen14, and a hybrid containing both isotopes. When the hybrid DNA was made single stranded by heating, they would show one parental strand and one that had been newly synthesised. Thus, when DNA is synthesised the DNA double helix splits into two, each of the single strands acting as a template for the synthesis of a complementary strand. This phenomenon is called semi-conservative DNA replication. Against this background of both methodical and theoretical progress, the development in molecular genetics became faster and faster. Already in 1995, the entire genome of the bacterium Haemophilus influenzae could be sequenced. This was followed, in 1996, by the release of the first eukaryote genome sequence in the experiment model Saccharomyces cerevisiae. In 1998, the first genome sequence for a multicellular eukaryote, Caenorhabditis elegans, was released. Subsequently, in 2001, the first draft sequences of the human genome were released simultaneously by the Human Genome Project and Celera Genomics. We now have something like a successful mapping of the human genome. It is sequenced. For some, these developments may be seen as the triumphant 77

Meselson & Stahl (1958).

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fulfilment of Morgan and Muller’s project of reducing research to physical and molecular approaches, filling in the formerly abstract concepts of genes, alleles, etc. with physical and chemical properties. The question of whether this is correct - whether or not we can take this shift to mean that classical genetics, formulated by Morgan in 1926, is replaced, incorporated or not, in molecular genetics that began officially in 1953 will be the subject of the next section.

ii.

Systematic framework78

Keeping the historical development of genetics outlined in the previous section in mind, I shall now focus on the systematic framework concerning the relationship between classical and molecular genetics and the problem of comparing these genetic theories. After all, molecular genetics developed out of classical genetics. To put it in a nutshell, there are two contrary positions in the literature: on the one hand, there is a more or less “reductionist strand” among certain philosophers, which postulates that classical genetics can, firstly, be sufficiently distinguished from molecular genetics (and vice versa), and, secondly, that it is possible to reduce classical genetics to molecular genetics (or even this reduction has already been done in practice). On the other hand, there is an “anti-reductionist strand” that takes up arguments of philosophers against reducing classical genetics or parts of it to molecular genetics. Let me outline these two strands in more detail. First, let us look at the reductionist strand, which is associated with the names of, among others, William K. Goosens, Ernest Nagel, Alexander Rosenberg, Michael Ruse, Kenneth F. Schaffner, C. Kenneth Waters, and Marcel Weber. 79 We will consider the main themes here without going into too much detail, since we will later be arguing for a reductionist approach to classical genetics in some detail in the following chapters, in which helpful links to the general part of this work will be given. 78

Compare in general Beurton, Falk & Rheinberger (2000), Rheinberger (2004), and Sarkar (1998). 79 Cf. Goosens (1978), Kimbrough (1979), Nagel (1961), Rosenberg (1978, 1985, 1994, and 2001), Ruse (1971 and 1974), Schaffner (1967, 1969a, 1969b, 1974, 1993), Waters (1990, 1994, and 2000), and Weber (1996 and 2005). Let me note that the mentioned philosophers are not always reductionist tout-court, compare in particular Kimbrough (1979), Rosenberg (1985 and 1994), and the not yet mentioned papers of Nagel (1969), Rosenberg & Kaplan (2005), and Waters (2003).

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The first claim of any reductionist position can be stated as follows: the characteristic concepts of both genetic theories can be bi-conditionally linked. Let’s have a look at a concept that may be expressed purely in terms of classical genetics, the “recessive allele for sickle-cell anaemia” for instance. This concept can be bi-conditionally linked with the constructed concept “DNA sequence XY” as a simplified designator of molecular genetics that refers to a certain sequence of DNA. Thus, it is presupposed that the classifications of classical genetics can be matched by constructed concepts of molecular genetics. The argument for this claim of a bi-conditional connection of concepts is mainly based on the common ground of ontological reductionism and the completeness of molecular genetics with respect to classical genetics. I shall consider these issues later on in more detail (cf. ‘relative completeness of molecular genetics, chapter VI, p. 242). Secondly, any law-like generalization of classical genetics can be derived from law-like generalizations of molecular genetics. For instance, the classical law-like generalization concerning the inheritance of genes can be derived from law-like generalizations that figure in molecular biology. Those are law-like generalizations concerning the corresponding DNA sequences with regard to their molecular replication mechanisms, the molecular causal chain during the formation of sex cells, the molecular development of the organism with this DNA sequence, and so forth. Without going into detail at this point, let us have a look at a law-like principle of classical genetics at a very abstract level, say if x has B at t1, then x will have C at t2: ∀x: (Bx  Cx) Let us take the simple example of the sickle-cell anaemia in terms of classical genetics: any x that has two recessive alleles for sickle-cell anaemia (B), will have numerous disease symptoms (C). From a molecular point of view, let us ascribe “P” to x if x has a DNA sequence XY (in the above-mentioned way) and “Q” to x if x will produce deformed blood cells that cause malfunctions of certain organs. Given the relative completeness in causal and nomological respects of molecular genetics with respect to classical genetics, the molecular reference objects of “P” and “Q” have to be causally linked as well: ∀x: (Px  Qx)

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In addition to this, let us assume the mentioned bi-conditional linkage of the characteristic concepts, say the concept “B” of classical genetics is bi-conditionally linked with the concept “P” of molecular genetics. In the same manner, the concept “C” of classical genetics is biconditionally linked with the concept “Q” of molecular genetics: “B”  “P”, and “C”  “Q” As a result of this, the classical law-like generalization concerning (∀ x: (Bx  Cx)) can be derived from the molecular law-like generalization that connects the molecular reference objects of “P” and “Q” (∀x: (Px  Qx)). The law-like generalization in terms of classical genetics about the disease symptoms resulting from two recessive alleles for sickle-cell anaemia can be derived from the law-like molecular genetics. This means, the description of the causal connection between the above-mentioned DNA sequence XY and its effect for the organs qua deformed blood cells can be derived from molecular genetics. Finally, any law-like generalization of classical genetics can be explained by means of concepts and law-like generalizations of molecular genetics. This claim is based on the following premises: Molecular genetics is relatively complete in explanatory respects with regard to classical genetics. In addition to this, the previous two points are taken for granted: The concepts of the two genetic theories can be bi-conditionally linked, and the law-like principles of classical genetics can be derived from law-like generalizations of molecular genetics. As a result of this, we can make an argument for the following claim: in principal, every law-like principle of classical genetics can be explained in molecular terms. Using our example, of the sickle cell anaemia will help to demonstrate this claim. Molecular genetics can give an explanation of the causal link between the DNA sequence XY and its organic effects qua deformed blood cells (∀x: (Px  Qx)). We assume that this explanation is relatively complete with regard to classical genetics. Furthermore, the concepts of the two genetic theories can be biconditionally linked in the following way: “B”  “P”, and “C”  “Q”. As a result of this, the classical law-like principle concerning the sicklecell anaemia (∀x: (Bx  Cx)) can be derived from the molecular law-like principles linking the DNA sequence XY and its organic effects qua deformed blood cells (∀x: (Px  Qx)). Therefore, molecular genetics can give an explanation of the causal link between two recessive alleles for

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sickle-cell anaemia (B) in an organism and the consequence of numerous disease symptoms (C). On the other hand, secondly, let me consider the anti-reductionist strand that is reflected in the approaches of, among others, Lindely Darden, David Hull, Harold Kincaid, Philip Kitcher, Nancy Maull, and Russel Vance.80 Once again, I shall outline this strand without going into too much detail. After all, the anti-reductionist arguments will be considered later on in this and the following chapters, and this section only aims to give a systematic overview of the debate. Let me note that I do not consider the semantic differences between concepts of classical genetics and concepts of molecular genetics as an anti-reductionist argument. It is certainly not the intention of this work to argue for a semantic reduction in general, or to argue for a semantic reduction of classical genetics to molecular genetics. Thus, it is not my intention to reduce the meaning of the concept of the gene, for instance, to the meaning of a concept of DNA sequences. Let me begin with the following anti-reductionist claim: the proper concepts of both genetic theories cannot be bi-conditionally linked because they are not co-extensional. The concepts of classical genetics often refer to property tokens that come under different constructed concepts of molecular genetics. For instance, the concept “gene” of classical genetics brings out in a homogeneous way salient similarities among entities that come under different descriptions in terms of molecular genetics. Leaving aside molecular details, there are different DNA sequences that can be referred to by “gene”. For that reason, there is an asymmetry between concepts of classical genetics and concepts of molecular genetics. Abstracting from details, there is on the one hand a concept of classical genetics, say “classical gene X” that describes a certain set of entities and brings out their salient similarities. But on the other hand, there are differently constructed concepts of molecular genetics that describe the entities in question. Let me call them “DNA sequence X1”, “DNA sequence X2”, etc. Thus, the concept “classical gene 80

Cf. Darden & Maull (1977), Hull (1972, 1974 and 1979), Kincaid (1990), Kitcher (1984 and 1999), and Vance (1996). Let us keep in mind that some of the philosophers associated with the reductionist strand have put forward anti-reductionist arguments as well, in particular Kimbrough (1979), Nagel (1969), Rosenberg & Kaplan (2005), and Waters (2003). These anti-reductionist arguments are expressed within this part of the section. On the other hand, the mentioned philosophers of the anti-reductionist strand are not anti-reductionist tout-court as well, in particular Hull (1979) and Kitcher (1984).

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X” cannot be bi-conditionally linked to one molecular concept such as “DNA sequence X1”. Let us return to the example from our previous chapters, the property of having a gene that produces yellow blossoms. This can be molecularly realized by different sequences of DNA because of the redundancy of the genetic code. In other words, there are DNA sequences that are, on the one hand, described by “gene that produces yellow blossoms”, but that are, on the other hand, different DNA sequences. For that reason, the concept of classical genetics “gene that produces yellow blossoms” cannot be biconditionally linked to one of the constructed molecular concepts such as “DNA sequence X1”. This means furthermore that the law-like generalizations of classical genetics that contain concepts such as “gene” cannot be derived from lawlike generalizations of molecular genetics. For that reason, a reductionist approach to the theory of classical genetics by means of a deduction of concepts and law-like generalizations must therefore fail. Let me note at this point, that a reductive explanation of any property token of classical genetics may be nonetheless possible. This is the consequence of ontological reductionism and the completeness of molecular genetics with regard to classical genetics – two claims the philosophers of the antireductionist strand generally agree with. To sum up, this argument of multiple realization seems to refute the first two claims of the reductionist strand. It furthermore suggests the failure of the third reductionist claim as concerning concepts and law-like generalizations of classical genetics. Secondly, let us examine an explanatory argument against the reduction of classical genetics to molecular genetics. This argument contains at least two aspects. First, there are explanations of property tokens in terms of classical genetics that bring out salient similarities among these property tokens. Even under the assumption that molecular genetics could bring out these salient similarities (contrary to the previous point), such a molecular explanation would not add anything essential. To put it another way, there is no need for explanations in terms of molecular genetics if we focus on the issues that are brought out in terms of classical genetics. This explanatory unimportance of molecular genetics is mainly based on a claim of explanatory sufficiency of classical genetics. Second, classical genetics can explain property tokens in a way molecular genetics is not able to do. This second aspect is linked to the mentioned first claim of the anti-reductionist strand. Concepts of classical genetics, and thus their explanations, are relatively abstract. Therefore, they possess a relatively broad extension. Contrary to this, the explanations in terms of

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molecular genetics are relatively detailed ones, such that they possess a relatively narrow extension. As a result of this, it is only the explanations in terms of classical genetics that bring out salient similarities among a certain set of entities while an explanation in terms of molecular genetics is often heterogeneous. This argument is mainly based on the first antireductionist argument of multiple realization. The salient similarities considered in classical genetics disappear at the molecular level of description. To sum up these two aspects, there are still certain properties that are best explained in terms of classical genetics. This claim suggests that classical genetics cannot be reduced to molecular genetics. In order to illustrate this line of argument, let us consider the following example: Cytological explanations within classical genetics provide a sufficient answer for the independent assortment of nonhomologous chromosomes during the meiosis. Let us keep in mind that classical genetics is fundamentally based on cytological researches at the beginning of the 20th century (cf. ‘historical framework’, this chapter, p. 183). Here we have no need for molecular details in order to explain the phenomenon that frames the results of Mendel’s experiments and the confirmation by de Vries, Correns, and Tschermak-Seysenegg. Making this point even more compelling as an anti-reductionist argument, a molecular explanation of this assortment of chromosomes would be extremely heterogeneous. After all, the molecular explanation of the assortment of genes during meiosis would have to consider the molecular differences among DNA sequences (or chromosomes) such that the explanation of classical genetics could not be derived from molecular genetics. Third, let me consider the difference between the two genetic theories with respect to law-like generalizations. The lawfulness of classical genetics differs from the lawfulness of molecular genetics. To put it another way, the law-like generalizations that figure in classical genetics are not that strict if they obtain at all. For that reason, classical genetics cannot be representatively captured by the derivation of its law-like generalizations from molecular law-like generalizations. Such a derivation would miss the point of classical genetics. In general, the law-like generalizations of classical genetics are ceteris-paribus laws and hold only approximately. Law-like generalizations of molecular genetics are also ceteris-paribus laws, but their validity conditions can be expressed in more detail. Molecular lawlike generalizations are less approximate. Thus, leaving aside the first anti-

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reductionist argument, what we could derive from molecular law-like generalizations would not represent the theory of classical genetics. Finally, let us consider the anti-reductionist theme of independence. Classical genetics cannot be reduced to molecular genetics because the latter theory is not independent from the former one. But such an independence is an implicit requirement for any reductionist approach. In order to reduce classical genetics to molecular genetics, the concepts of classical genetics have to be reduced to concepts of molecular genetics that are purely defined in molecular terms. This anti-reductionist argument claims that there are no such independent levels of explanations. Both the concepts of classical genetics and molecular genetics are mutually dependent. As a consequence of this mutual dependency of concepts and explanations, classical and molecular genetics should be considered as complementary parts; both these theories are about the explanation of the same set of entities (in the case they refer to entities generally considered in terms of classical genetics). This anti-reductionist argument is mainly based on the obvious difference between two different types of explanations and a historical component: One the one hand, there are more or less purely functional descriptions in terms of classical genetics. Let us keep in mind that the concept of the gene at the beginning of the 20th century was purely functional and abstract. The explanations in terms of molecular biology are, on the other hand, mainly based on the compositions of molecules. The famous discoveries such as the discovery of the DNA structure by Watson & Crick were only made possible on the basis of the gene concept developed by classical genetics. These discoveries were guided by the functionally defined concepts of classical genetics. Therefore, the molecular gene concept is not purely physically defined. It is essentially based on the functional characterizations of classical genetics. This means, the concepts of molecular genetics are something like semi-functionally and semi-physically defined (defined by molecular composition). Thus, unquestionably, these molecular and physical discoveries did not modify the classical gene concept post hoc. Let me leave aside at this point the debate about whether there is one gene concept in classical genetics (and how one could define it) and focus instead on the point of our antireductionist argument: a mutual dependency between both genetic theories is suggested such that it is not possible to distinguish both theories in order to reduce the one to the other by means of a reduction of concepts. The two genetic theories are not historically fixed or dated theories but part of the same research program.

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The approach

In this section, we will explore the motivation behind my approach to the relationship between classical and molecular genetics. First of all, I shall advance a brief, and non multiple realization based, argument against the above mentioned anti-reductionist arguments. Second, I shall then argue that the current debate on whether or not classical genetics can be in principle reduced to molecular genetics depends on the implications of multiple realization. In the spirit of the general part of this work, a reductionist strategy will be provided that takes into account the possibility of multiple realization. First, then, let us look at those anti-reductionist arguments that are not based on the multiple realization argument. As mentioned in the previous section (cf. ‘systematic framework’, this chapter, p. 192), the anti-reductionist may claim that there is no need of explanations in terms of molecular genetics if we focus on the properties that are brought out in terms of classical genetics. Classical genetics, according to this view, possesses an explanatory sufficiency which in itself gives us an argument against the reductionist position. Since we are leaving aside the multiple realization argument that supports this explanatory argument, I shall sum up this anti-reductionist claim as simply claiming that there are phenomena that seem to be best explained in terms of classical genetics. Its concepts are generally functionally defined – and not defined by composition like the concepts of molecular genetics. There are explanations in terms of classical genetics that do not need the molecular details about the composition of DNA, RNA, etc. However, this reference to the best explanation is either false, or means something like a best explanation from a heuristic point of view. In fact, the reference to the best explanation implies that the explanation of classical genetics is better than the explanation of molecular genetics or any other more fundamental theory. But this logically implies either that there is a conflict with the argument for ontological reductionism or the completeness of physics (and molecular genetics). That is to say, taking ontological reductionism for granted, any property token that is explained in terms of classical genetics can also be explained in terms of molecular genetics. Such an explanation is of course more detailed, etc. I shall outline these issues later on in more detail (cf. ‘completeness of molecular genetics, chapter VI, p. 242, and ‘argument for the token-identity of genes and DNA’, chapter VI, p. 247). To conclude, the reference to the best explanation is false in the context of classical genetics. Or, unpacking the second meaning of this reference to the best explanation, it only really

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means something like a heuristic advantage. But, first of all, any such heuristic advantage would be mainly based on the multiple realization argument. I shall discuss this issue later (cf. ‘final remarks’, chapter VII, p. 297). Furthermore, pointing out a heuristic advantage is not an antireductionist argument per se. To conclude, the reference to the best explanation is either false, or not an anti-reductionist argument per se. Before moving on to the second anti-reductionist argument, let me add some words on Kitcher’s unificationist approach.81 In order to improve our scientific understanding of property tokens, Kitcher proposes the following approach: theories, law-like generalizations or concepts that are used again and again in order to explain a broad set of property tokens improve our scientific understanding of the property tokens in question. To put it another way, if a certain property token can be explained by two different theories, we should prefer the theory that can explain, by the same so-called argument pattern, a broader set of other entities. This use of the same explicative concepts (argument patterns) makes intelligible the similarities between the relevant property token with these other entities, and thus, improves our scientific understanding. After all, it outlines salient similarities among property tokens the other theory cannot outline in such a way. Against this background, it is obvious that more abstract theories, such as classical genetics with respect to molecular genetics, may be preferred, for instance, in order to outline salient similarities among gene tokens. This is more than a heuristic value, as I have considered in the previous paragraph. It is evident that my proposed reductionist strategy of the general part of this work is compatible with this model of scientific explanation. If we compare classical genetics and molecular genetics, it is molecular genetics that can explain a broader set of entities by means of the same argument patterns. In general, it is physics (or the more fundamental theories) that are more unifying. Keeping this in mind for, as we shall see later on, it is possible to reduce classical genetics conservatively to molecular genetics, and to preserve the scientific status of classical genetics just because classical genetics possesses the capability of abstracting from molecular details that is denied to molecular genetics. This is however, simply a feature adhering to another level of description and explanation. In general, it is molecular genetics that is more unifying that classical genetics. Nonetheless, in the context of specific sets of entities (genes that are molecularly different), it is classical genetics that is more unifying. To conclude, classical genetics unifies molecularly 81

Kitcher (especially 1981 and 1984).

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different property tokens by abstract concepts, and can nonetheless be reduced to molecular genetics that is in general the more unifying theory. Keeping this point in mind, let me consider the anti-reductionist argument that is based on the lawfulness of classical genetics. The lawfulness of classical genetics differs from the lawfulness of molecular genetics. Classical genetics, so one may argue, is more than its law-like generalizations. Therefore, what can be derived from molecular law-like generalizations does not represent classical genetics. To put it another way, there are, in a simplified manner, two parts of classical genetics. One part can be captured by law-like generalizations. Let us take for granted at this point that it is possible to deduce these law-like generalizations from law-like generalizations of molecular genetics. At least, the argument under consideration says nothing against this possibility. The other part of classical genetics cannot be captured by law-like generalizations, and therefore, it cannot be deduced from the law-like generalizations of molecular genetics. There are two arguments against this: first, let us bear in mind that if it is not possible to connect systematically the explanations of classical genetics with the explanations of molecular genetics, the elimination of the former ones is suggested. Thus, the scientific quality of the part of classical genetics that cannot be deduced from law-like generalizations of molecular genetics is put into peril. This argument suggests a reductionist approach to any part of a theory that aims to be explanatory relevant. Second, explanations are based on causal relations, and thus, they are based on law-like generalizations. As outlined in detail, there are good arguments to take explanations as causal explanations (cf. ‘concept of explanation’, chapter II, p. 71). As a result of this, any part of classical genetics that cannot be captured by law-like generalizations seems to fall under the description of explanatory redundancy. Taking these two points together, there is a good argument to claim that any explanatory part of classical genetics is based on law-like generalizations that can be deduced from law-like generalizations of molecular genetics. Of course, as I shall outline in detail in the next chapter, classical genetics is more than the Mendelian laws and their modifications at the beginning of the 20th century. But, any concept of classical genetics can be functionally defined or characterized, and, law-like functional definitions or characterizations of gene types for instance are in fact law-like generalizations. In order to

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secure their scientific quality, it seems to be necessary to connect them systematically with law-like generalizations of molecular genetics.82 In this context, it is not an anti-reductionist argument that law-like generalizations of classical genetics only hold approximately, while the law-like generalizations of molecular genetics are, even if they are ceteris paribus laws as well, more strict. The aim of conservative reductionism is in fact to embed abstract theories with law-like, ceteris paribus generalizations in more detailed and general theories that may provide explanations for the limits of the former theories and their law-like generalizations. If a law-like generalization of classical genetics is true about a certain set of property tokens, and a more detailed law-like generalization in terms of molecular genetics is true as well about the same set of property tokens, the difference in lawfullness cannot constitute an anti-reductionist argument, since both these generalizations are about the same entities. The point of conservative reductionism can be spelled out as systematic correlation of different concepts and explanations that makes intelligible the scientific value of each of the relata. In this context, the starting point is that there are two different genetic theories with law-like generalizations that differ in their lawfulness. The aim of a reductionist approach that is conservative is to provide a systematic relationship that makes intelligible the obvious differences between these theories without leading to the elimination of any one of the theories. To secure the scientific value of the law-like generalizations of classical genetics, and thus ward off eliminativism, such a reductionist strategy seems to be the only option. . Let us now consider the last mentioned anti-reductionist argument outside of those based on the multiple realization argument. Molecular genetics developed out of classical genetics such that it is not possible to reduce the latter to the former, and thus, by implication, the concepts of molecular genetics developed out of the concepts of classical genetics. We need to distinguish two aspects of this argument: on the one hand, its factual historical foundation, and on the other hand, its more substantial systematic claim. Historically, classical genetics came first, and out it gradually developed the more and more molecular tendency. Let us briefly reiterate this historical development, as we have framed it previously: At the beginning there was Mendel and his famous experiments in 1865 that were rediscovered and reconfirmed at the beginning of the 20th century, there was progress in cytology, etc. during these decades, and after the 82

Compare furthermore the consideration of Rosenberg & Kaplan (2005, footnote 15) that regards Kitcher (1993b, p. 28).

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reflection of Morgan and his group on their experiments and discoveries in the 1910th and 1920th, classical genetics became a coherent genetic theory that took up the research project of explaining the intricate links between evolution, development and heredity. In this context, and against the background of the scientific progress in physics and chemistry, in particular the application of its methods in the research field of genetics, a more molecular focus on the issues of genetics began in the 1930th and 1940th and led to the discovery of the DNA by Watson & Crick in 1953. At least from this important discovery on, there was molecular genetics that tried to explain mechanisms of evolution, development and heredity with concepts of molecular biology. It is historically correct that Watson & Crick would not have searched for the physical structure of a gene if there had not been a gene concept. There was a functional characterization of a gene, and Watson & Crick tried to find the physical structure that fulfils the caused task that defines the gene in question. One must concede that historically, concepts of molecular genetics developed out of concepts of classical genetics. In terms of functional definition and realization, there were the functionally defined concepts of classical genetics such as genes, and later on, it was possible to explain in molecular terms how the causal tasks in question are fulfilled by certain physical structures such as DNA or RNA. But, despite this historical component and this sketched out dependency, it is nonetheless possible to compare both genetic theories in a purely systematic way. They are two theories in the same domain and partly about the same entities. Whenever they describe and explain the same entity, their descriptions and explanations are in fact different. And it is this difference that motivates the debate about their relationship from a non-historical point of view. The historical component seems to complicate or hinder this debate about reductionism. But, in fact the growth of molecular genetics out of classical genetics does not exclude to consider their systematic relationship. In this context, it is the aim of this part of the work to consider the systematic differences between theories and how to spell out their relationship beyond the historical development as outlined in the beginning of this chapter (cf. ‘historical framework’, this chapter, p. 183). This means, I shall consider the question whether or not it is possible to apply my reductionist model of the general part of this work to theories that are historically related. The question we face is whether or not a reductionist approach is compatible with conserving the concepts of a theory in its successor theory. . My position is that it is possible to reduce classical genetics to molecular genetics in a conservative way even if

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molecular genetics has developed out of classical genetics. Such a conservative reduction will bring out what remained indispensable of classical genetics up to the present even if genetic research is almost purely molecular today. To give parts of my conclusion in advance, I shall show that, recognizing the saliency of multiple realization, there is a representative part of classical genetics that may be taken to be indispensable from a scientific point of view. Classical genetics brings out salient similarities that are beyond the reach of molecular genetics. . But, in order to avoid the eliminativist consequences of the multiple realization argument, it is necessary to construct a systematic relationship. This means, one has to develop a reductionist approach that makes intelligible the scientific quality of classical genetics. Thus, I shall apply the proposed reductionist strategy of the general part of this work and incorporate the historical dimension of the debate over classical genetics as the predecessor of molecular genetics by showing how it can be reduced to its successor in a conservative manner (contrary to a replacement). Before proceeding to this incorporation of the historical dimension, let me focus on the systematic component of the anti-reductionist argument. The concepts of classical genetics are purely functionally defined concepts. For instance, the gene concept is a functionally defined concept. The concepts of molecular genetics, on the other hand, are more or less about molecular compositions, certain physical structures, etc., as, for instance, DNA, the configurations of RNA molecules, enzymes, and so on. Up to this point, there is no problem for a reductionist approach. As outlined in the general part of this work, the concepts of the special sciences are generally functionally defined, while the ones of physics are defined by composition. However, the anti-reductionist may now claim that the concepts of molecular genetics are in fact not purely defined by composition but by function as well. They are defined by composition and the functional characterization in question of classical genetics. As a result of this, there is not a reduction of the concepts of classical genetics to concepts of molecular genetics but a modification of the original concepts by molecular details. In order to argue against this claim, let me distinguish between definition and something like guidance. Of course, molecular biologists are guided by classical genetics when they try to discover the molecular structures that fulfil the causal definition of a certain gene concept of classical genetics. But nonetheless, the definition of these molecular structures can be provided purely in terms of molecular genetics. This

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means that, if we leave aside those empirical procedures aimed at discovering the realizers of genes, alleles, etc., it is possible to define, from a molecular point of view, the discovered entity purely in terms of composition. Thus, at this point, we have obtained a distinction between concepts of classical genetics that are defined by function, and concepts of molecular genetics that are defined by composition. As the second part of this section, let me outline the reductionist strategy I will be following in the next three chapters. First and foremost, let us keep in mind that the proposed strategy aims to provide a conservative approach to classical genetics. This means, I shall argue for a systematic relationship between classical and molecular genetics that considers classical genetics as reducible but indispensable in our scientific system. This conservative reductionism is in the spirit of the general part of this work. Let me note that, if my argument and strategy is convincing, the result is probably what most of the philosophers of the anti-reductionist strand have in mind when they try to defend the autonomy and the indispensable character of classical genetics. My argument will run as follow: I shall fully take into account the possibility of multiple realization, this being the strongest anti-reductionist argument made over the last decades. Multiple realization of properties of classical genetics means that property tokens that come under one functionally defined concept of classical genetics come under different concepts of molecular genetics. Therefore, it seems that the concepts of classical genetics cannot be bi-conditionally connected with concepts of molecular genetics, and thus, reductionism must fail. Contrary to this antireductionist conclusion, as I shall argue, every molecular difference can lead to functional differences. Such functional differences can be considered, in principle, in non-molecular terms. This means, it is possible to distinguish molecular differences with respect to fitness differences of the organisms in question. Therefore, it is possible to construct functionally defined sub-concepts in the vocabulary of classical genetics. By means of these sub-concepts, it is possible to establish a nomological co-extension between these sub-concepts and concepts of molecular genetics. Having done this, the abstract concepts of classical genetics can be deduced from each of their sub-concepts, and thus reduced to molecular genetics. This strategy will be applied to law-like generalizations and explanations as well. I shall outline this strategy in detail in the last chapter of this part (cf. ‘construction of sub-concepts, chapter VII, p. 269). Before going into this reductionist strategy in chapter VII, I shall consider both genetic theories in more detail in the following two chapters

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V and VI as some kind of common ground in order to compare both theories. In chapter V, I shall take into account classical genetics. There, I shall argue, among other things, that the property tokens of classical genetics supervene on configurations of property tokens of molecular genetics. Apart from this point, which is essential in order to establish a reductionist approach, it is possible to define functionally any property that is considered in classical genetics. Against this background, I shall argue in chapter VI that configurations of property tokens of molecular genetics are the so-called realizer of properties of classical genetics. To put it another way, there is ontological reductionism, and property tokens that come under the functionally defined concepts of classical genetics come as well under the concepts defined by composition in terms of molecular genetics. This argument for the token-identity of genes and DNA is mainly based on the concept of supervenience (outlined in chapter V) and a completeness claim: molecular genetics is complete in causal, nomological and explanatory respects with regard to classical genetics. Against this background, as already mentioned, I shall outline in chapter VII the reductionist strategy that aims to reduce conservatively classical genetics to molecular genetics by means of functionally defined sub-concepts.

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V.

Classical genetics Preliminary remark The answer to the question of whether or not classical genetic can be reduced to molecular genetics depends on the systematic core of classical genetics.

Abstract The aim of this chapter is to examine the systematic core of classical genetics. This will serve as the starting point for the systematic comparison with molecular genetics in the following chapter (VI) and the argument for a reduction of classical genetics to molecular genetics in the next but one chapter (VII). In this chapter, after an introduction to several central terms, I shall focus on four essential issues. First, the concept of supervenience will be applied to property tokens of classical genetics. On this basis, the argument for the tokenidentity of genes and DNA can be outlined in the next chapter (VI). Second, the law-like generalizations of classical genetics will be considered in detail. The still existing explicative force of classical genetics will thus become evident. Third, a functionally defined gene concept will be provided as a representative part of classical genetics. Let me note, that since the concept of multiple realization will be introduced not before the next but one chapter (VII), the indispensable scientific character of classical genetics will not be considered here. Finally, the explanatory limits of classical genetics will be examined, and, thus, the motivation for a reductionist approach will be sketched out.

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Introduction to classical genetics

Despite modifications over time, classical genetics possesses a conceptual core. Prima facie, classical genetics seems to be a complex of informative statements within a specific vocabulary that changed from Mendel to Morgan, and founded on assumptions that are partly modified in the development of genetics. Because of these modifications and changes, there seems to be more than one theory of classical genetics. If this were true, the comparison of classical and molecular genetics would be difficult. Therefore, I shall consider these modifications and changes in this section in order to outline nonetheless an essential core that remains more or less unchanged. This is the distinction between genotype and phenotype that is characteristic for classical genetics (cf. ‘the importance of the gene concept’, chapter V, p. 215). On this basis, I shall define a gene concept that represents classical genetics in my analyses of the following two chapters (cf. ‘functional characterization of the gene’, chapter V, p. 220). At the end of this chapter, the explanatory limits of classical genetics will be outlined in order to motivate a reductionist approach (cf. ‘the explanatory limits of classical genetics’, chapter V, p. 228). First of all, let us look at the reasons it difficult to formulate one theory of classical genetics in order to compare it with molecular genetics. In order not to complicate the issues, let us assume for the time being that there is one theory of molecular genetics. I shall consider this issue in the next chapter in more detail (cf. ‘introduction to molecular genetics’, chapter VI, p. 232). Here, the focus lies on the conceptual changes and replacements in genetics before the discovery of the DNA structure in 1953. Everything started with Mendel in 1865 whose experiments were rediscovered and confirmed in 1900. In the context of scientific progress in cytology, genetics became an own field of scientific research at the beginning of the 20th century. Biologists tried to make use of Mendel’s results and explanations and the progress in cytology in order to explain issues on evolution, development, and heredity. Thereby, the techniques, strategies of explanation, the basic assumptions, etc. changed in the first three decades of the 20th century until Morgan provided something like a coherent explanatory genetic theory (cf. ‘historical framework’, chapter IV, p. 183).83 On the one hand, concepts and law-like generalizations were 83

Compare for a good biological overview of classical genetics and the chromosome theory of inheritance any standard literature such as, for instance, Campbell (2005, especially ch. 15).

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modified or even replaced, such as the independent assortment stated by Mendel. On the other hand, there was an enormous increase of understanding such that, for instance, Morgan’s theory is more capacious compared to Mendel’s theory (results and explanations of these results). For instance, the purely functionally defined factors or elements Mendel postulated in order to explain the statistical distribution of the phenotypic effects were specified later on as genes or alleles that are something physical and lying on chromosomes. This is evidence of the conceptual changes occurring in the period spanning Mendel and Morgan. This historical change sets up a problem for reductionism: how is it possible to compare classical genetics with molecular genetics if there is such variance in classical genetics as to make it seem like more than one theory? Since, in fact, Mendel’s concept of a factor or an element differs from the gene concept of Morgan. Despite the differences in the methods in genetic research, the use of technical terms and the manner of explanations, in all genetic researches and writings of these years there was a fundamental concept underlying the projects of the researchers. This is the distinction between the genotype and the phenotype of an organism. As already mentioned, Mendel explained the observable effects such as green or yellow pea seeds by means of corresponding factors or elements. But even if there was a conceptual change of Mendel’s factors or elements to the gene concept of Morgan and his collaborators, the distinction between genotype and phenotype remained. From this perspective, there is a systematic core of classical genetics (cf. ‘historical framework’, chapter IV, p. 183). Let me explain this in more detail. The genotype of an organism is its hereditary disposition. The genes of an organism are its genotype. In this context, the genotype of an organism is all its genes – like a factor for yellow peas seeds in terms of Mendel, or a gene that produces white eyes in terms of Morgan and his collaborators. What had not changed from Mendel to Morgan is that there is something that causes the phenotypic effects. First it was called “factor” or “element”, later on it was called “allele” or “gene”. What had changed was the knowledge about these causally efficacious entities. According to Mendel, these entities were purely functionally defined and there were the famous Mendelian laws that describe mathematically the inheritance of traits by means of the inheritance of factors respectively elements. Later on, Mendel’s results became connected with the chromosome theory of Boveri & Sutton, which linked the concept, now called “genes”, to the well-supported assumption that genes are lying on chromosomes, and thus

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have physical presence. Furthermore, the laws stated by Mendel were modified. For instance, the one-gene-one-phenotype thesis was changed into something like a many-many relation, etc. Nonetheless, the conceptual distinction between genotype and phenotype per se remained. The phenotype of an organism, contrasted to the genotype, is the manifestation of the genotype, the visible features of the organism in question. The phenotype of an organism is, for instance, the yellow pea seeds, or the famous white eyes of Drosophila melanogaster. Of course, there was a conceptual change of the phenotype as well. For instance, Mendel’s experiments were only about phenotypes as observable traits such as the colour or shape of the pea plant Pisum sativum. The point here is that phenotypic effects are macroscopic, being easy to observe, to distinguish, etc. Later on, in the context of the progress in cytological research and the availability of better microscopes and methods of observations, it became clear that what can be observed such as yellow pea seeds or white eyes are the last step in a causal chain. If genes are something physical lying on chromosomes, and, one has, for instance, yellow pea seeds observable to the naked eye, there must be something in between. The must be an intracellular causal chain from the genotype to the macroscopic phenotype. In fact, leaving aside cytological details at this point, this is the implication of the conceptual distinction between genotype and phenotype. There is a causal relation from genotype to phenotype. To put it another way, a certain phenotype is caused by a gene or several genes. It is possible to observe the phenotype of an organism, and in order to explain the occurrence of this phenotype, a causal efficacious genotype is postulated. This is what Mendel assumed, and later on, this explanation became supported by means of many other experiments. I shall take this fundamental conceptual distinction as a starting point of this chapter and for my reductionist approach in general. In this context, let us bear in mind that even if there was the so-called synthesis of genetics with cytological research, there was no explanation of this causal relation from genotype to phenotype per se. To sum up, what remained unchanged is the conceptual distinction between genotype and phenotype and the postulation of a causal relation. This is something like a guiding idea in genetics that still actuates contemporary genetic research. What changed were the functional specifications of certain genes. For instance, the general laws of Mendel became modified and the concept of the gene changed in several respects. This history still failed to account for what in the physical structure of the

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gene leads to an explanation of its causal efficacy – the production of the phenotype – and in pursuing the answer to that question, Morgan and his collaborators developed molecular genetics.

ii.

The concept of supervenience applied to classical genetics

Property tokens of classical genetics supervene on configurations of property tokens of molecular genetics. As already considered in the general part of this work, biological properties supervene on physical properties (cf. ‘supervenience’, chapter I, p. 33). In this context, I shall outline in this section the first of two premises that will figure in the argument for the token-identity of genes and DNA. This means, in the next chapter, showing that this relationship will be modified such that the property tokens of classical genetics are identical with configurations of property tokens of molecular genetics (cf. ‘argument for the token-identity of genes and DNA’, chapter VI, p. 247). Since I shall consider property tokens of molecular genetics in the next chapter, let me leave aside the details in this chapter, taking property tokens of molecular genetics here in a more intuitive sense such as DNA sequences, the molecular structure of cells, etc. Let me note in advance that, since token-identity is a stronger relationship than supervenience, and since I have argued in the general part of this work to take the concept of supervenience to describe the relationship between concepts of different theories, I shall come back to this issue later on in chapter VII where the relationship between the concepts of classical and molecular genetics will be considered (cf. ‘introduction to the relationship’, chapter VII, p. 258). Keeping this structure of the biological part in mind, let me now consider the supervenience concept applied to property tokens: any property token of classical genetics supervenes on a property token or a configuration of property tokens of molecular genetics.84 The argument for this simplification is that what essentially characterizes molecular genetics with respect to classical genetics is in fact the incorporation of physical methods and concepts. Thus, let me take property tokens of molecular genetics as entities that are described first and foremost in terms of molecular biology, which takes into account physical approaches. In this context, this section is about the systematic relationship characterized in 84

In order not to complicate the issue, I shall not distinguish between molecular genetics, molecular biology and physics in what follows.

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terms of the determination and dependency relation of the concept of supervenience. The determination relation can be spelled out as follows: any molecular duplicate of our world is a duplicate of our world of classical genetics.85 The molecular world is the entities in the world that are described and explained in terms of molecular genetics, and the world of classical genetics is the entities in the world described and explained in terms of classical genetics: World of classical genetics  (supervenes on) 1. Molecular world

Duplicate of world of classical gen. ↑ (determines) 2. Duplicate of the molecular world

The term ‘molecular duplicate’ means a duplicate of any molecular property token in space-time. In such a molecular duplicate of our world there will be as well all the property tokens of classical genetics that are in our world. For instance, there will be also genes, recessive alleles, green pea seeds of Pisum sativum, and white eyes of certain fruit flies, etc. To put it in other terms, the molecular property tokens in the world determine what property tokens of classical genetics occur in the world. The molecular property tokens fix all the property tokens of classical genetics. Let us go into more detail and distinguish two kinds of arguments in favour of this determination relation. Some kind of historical existence determination is indicated. On the one hand, physics, chemistry, and molecular biology tell us something about the history of our universe, and the development of macromolecules, DNA, cells etc. out of physical elements and micromolecules. On the other hand, classical genetics tells us something about the causal relations between genotype and phenotype, the inheritance of genes, etc. The point I want to make here is the following: it is suggested that at the beginning of our universe, there were only physical property tokens, and later on molecules such as DNA, RNA, etc. Classical genetics now aims to consider entities such as genes that are taken to be causally efficacious for complex effects such as yellow pea seeds or white eyes in fruit flies. In other terms, in the very beginning of the universe, there were no entities that make true the applications of concepts of classical genetics such as 85

Cf. Jackson (1998, p. 12) and Chalmers (1996, pp. 32-41) in general, and Rosenberg (1978) in particular for biological properties.

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“gene” or “phenotype”. However, at one time, physical tokens were in certain particular molecular configurations. Subsequent to this, property tokens of classical genetics occurred. ‘Subsequent’ means, given a duplicate of the whole physical and molecular history of our universe, the history of classical genetics would be the same. For instance, we can take Mendel’s experiments. Under the assumption that the molecular environmental conditions would be perfectly the same (enough water, sun, nutrients, etc.) for two sets of molecularly identical peas seeds, we expect the same pea plants growing. This means, possessing the same phenotypic effects, etc. At least, there is no reason to assume something different. If there were a difference in the development of these plants, for instance because of spontaneous mutations or so, there would be a molecular difference as well. When there is a difference in the history outlined in terms of classical genetics of two worlds, there also is a molecular difference in the histories of the worlds. In any case, it is suggested that molecular conditions determine the occurrence of property tokens of classical genetics. When certain configurations of molecular property tokens are given, property tokens of classical genetics occur as well. In other words, configurations of molecular property tokens determine the existence and character of property tokens of classical genetics. There were no property tokens of classical genetics until certain configurations of molecular property tokens occurred. The historical fact that molecular genetics is a theory that was discovered after classical genetics stands in no opposition to the natural determination relation spelled out here. Of course, molecular descriptions of a gene were first possible several decades after the experiments of Mendel. But, nonetheless, ontologically speaking, the history of our universe in which property tokens of classical genetics occurred at one day began with property tokens that were first purely physical, then molecular, and at some time point ‘x’ property tokens such as gene tokens or tokens of yellow pea seeds occurred. Let me consider the argument in favour of the determination relation. Some kind of duplicate determination is suggested. Whenever we duplicate something molecularly, we expect a duplicate in respect to the factors considered in classical genetics. Our experience suggests this. For instance, let us imagine two pea plants that are indiscernible from a molecular point of view. This molecular indifference suggests that they possess the same property tokens of classical genetics (at least if there are the same environmental conditions). To put it in general terms, same property tokens of classical genetics occur whenever the same molecular

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property tokens are configured in the same structure. Even emergentists would not claim that certain emergent property tokens emerge from some molecular conditions but fail to emerge when these molecular conditions occur again. The second aspect spelled out by the concept of supervenience is about a dependency relation that can be stated as follows: a change of property tokens of classical genetics is possible only if there is an appropriate change of molecular property tokens. There is no change of a property token of classical genetics without a change of molecular property tokens. Let me compare such a change: 1.

Change in classical genetics 

(supervenes on)

Change in molecular genetics

2. Change in classical genetics ↓ (implies) Change in molecular genetics

To illustrate this point, take our example of a pea plant. The pea plant does not change, say developing yellow seeds, without there being a change of some molecular property tokens. The molecular configuration of the seed cells changes whenever the colour turns to yellow. One can also compare two peas from the point of view of classical genetics. Say, there is one flower with yellow pea seeds, and another pea plant with green seeds. This phenotypic difference between these two pea plants depends on an appropriate molecular difference between these two peas. It is not possible that pea plants differ in phenotypic respects, but fail to differ from a molecular point of view. That is what experience suggests. We can call this ‘the concept of supervenience applied to classical genetics’. Any property token of classical genetics is determined by molecular property tokens, and it depends on them. Because of this determination and dependency, supervenience is an asymmetric relation. Therefore, let us keep in mind that the concept of supervenience per se does not imply that every molecular change or difference implies a change or difference of property tokens of classical genetics as well. According to this concept, it is possible that two entities differ from a molecular point of view, say they are different molecular configurations. However, the two molecular configurations may be pea plants of one and the same type. In any case, this supervenience will be one of two premises in order to argue in the next chapter for the token-identity of property tokens of classical genetics with configurations of property tokens of molecular genetics.

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Thus, I shall not consider the relationship between the concepts of both genetic theories in this chapter but do so later on in chapter VII. In this context, let us bear in mind that this section was only the beginning of the approach to the relationship between both genetic theories. The concept of supervenience as describing the ontological relationship (as done in this section) will end up in an identity of property tokens of classical genetics with configurations of property tokens of molecular genetics in the next chapter (cf. ‘argument for the token-identity of genes and DNA’, chapter VI, p. 247). Against this background, the concept of supervenience will be taken to describe the relationship between the concepts of both genetic theories in the next but one chapter (‘introduction to the relationship’, chapter VII, p. 258).

iii.

The importance of the gene concept

The concept of the gene is at the centre of classical genetics.86 Just like the theory of classical genetics, the gene concept accrues different connotations depending on the contexts of its use. Despite all these differences in the history of genetics, the gene concept always was the fundamental concept, which is how it is at the centre of, and thus representative of, classical genetics. The difficulty for the philosopher of science is that a definition of the gene concept does generally not take into account all the conceptual changes that occurred after the rediscovery of Mendel’s experiments. In order to provide nonetheless a gene concept that will figure as representative in my following analysis, I shall focus on the gene concept of Morgan and take into my usage only some of the changes from Mendel to Morgan. After all, Morgan’s gene concept is developed out of the gene concept of his predecessors and subsumes what remained true and appropriate in order to describe the entities that cause the phenotypic effects. To put it another way, the importance of the gene concept at any time is as an argument functioning to represent the collective unity of classical genetics. To try to show all the conceptual shifts to which the gene concept was subject would be unnecessarily complex, muddying our comparison with molecular genetics. Therefore, I shall focus mainly on the gene concept at the time of Morgan et al. By means of this definition, it will be possible to consider the following question: is the genetic concept of classical genetics still scientifically 86

Cf. Kimbrough (1979, p. 393) or Waters (1994, p. 165) who point out the importance of the gene concept for the theory of classical genetics as a whole.

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appropriate, and moreover, does it possess an indispensable scientific character as an argument against the elimination of classical genetics? In this section, I shall therefore outline some important details about the gene concept and its significance for the understanding of heredity. In the next section, I shall abstract from several of these details in order to formulate a functionally defined gene concept to represent the general classical genetics perspective, in the comparison with molecular genetics. Let us look at the causal efficiency of genes and their unit character. Here, we need to introduce some important terms from classical genetics. Genes in respect to their alleles produce the phenotype, and each gene constitutes some kind of a unit with a stable structure. This stability is not a specific physical characteristic, but a functional trait insofar as genes can be inherited from generation to generation. I shall be considering function per se in arguing for taking function as a causal disposition (cf. ‘functional characterization of the gene’, this chapter, p. 220). Keeping this point in mind, genes can be regarded as a functional unit lying in a linear arrangement on chromosomes. Every gene in a diploid organism exists in form of two corresponding alleles whereby each allele is lying on one of two homologous chromosomes at a certain locus. The term diploid means that the genotype of an organism consists in two sets of chromosomes. Thus, there are pairs of so-called homologous chromosomes. In such organisms, genes hence occur in two forms, called “alleles”. In this context, the term homologous chromosomes means that two chromosomes match in their length, loci of their centromeres, patterns of staining, and have corresponding loci for alleles of the same type of gene, such as the gene that produces the colour of the pea seeds. These corresponding alleles of one type of gene can be the same or different, and they can be either “wild types” or “mutants”. Organisms with the same alleles of one gene type are called “homozygous” for that gene, while organisms will be heterozygous for that gene, if the corresponding alleles differ. Let us bear in mind that in classical genetics the stable unit character of genes in relation to their alleles is only postulated in order to explain the observed results of crossing experiments, etc. The physical structure per se was not identified until 1953, at the beginning of molecular genetics. Mendel postulated the existence of causally efficacious factors in each pea plant in order to explain the statistical distribution of phenotypic traits of the peas in the successive generations of his crossing experiments.87 This causal relation between the genotype and the phenotype became the template for explaining the regularities of 87

Cf. Mendel (1865, in particular the chapters 9 and 11).

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phenotypic identities and differences in species. However, in classical genetics it is only postulated that genes produce phenotypic effects,88 without an explanation of how this causation works.89 This means, there is no causal explanation of the gene, but only the postulation that there must be something that causes the phenotypic effects that can be observed. Let me focus on segregation that is also essential for the gene concept. Alleles segregate according to statistical probability. The probabilities of the heredity of alleles from generation to generation can be described as Mendel did in 1865 for some characteristics of the pea plant Pisum sativum.90 If an organism possesses two different alleles for one gene, then 50% of its sex cells will carry the one allele and 50% of its sex cells will carry the other allele. Because of that distribution, each allele will be usually transmitted to the offspring generated with the same probability of 50%. After the rediscovery of Mendel’s work, the existence of these factors (later called “genes”) in the form of same or different alleles in organisms became a well-proved hypothesis in genetics. To put it another way, this hypothesis combines the inheritance probabilities of genes with the behaviour of chromosomes as seen in certain mechanisms that were discovered at the end of the 19th century, which brought about an enormous progress in cytological research, leading to the discovery of the so-called mitosis and the meiosis of the chromosomes. Let us consider this synthesis of genetics with the chromosome theory in more detail. First of all, during the process of meiosis, the pairs of homologous chromosomes will be replicated and separated according to four daughter cells with different haploid genotypes. These different daughter cells constitute the sex cells – and each of them possesses chromosomes that are originally from the mother and/or chromosomes that are originally from the father. Thereby, the probability of a sex cell to possess a certain chromosome from the father amounts to 50% – respectively 50% to possess it from the mother. Second, during the process of mitosis, the pairs of chromosomes will be replicated and separated according to two daughter cells with identical diploid genotypes. 88

Compare for instance Morgan (1926, p. 306) where he speculates about the causal efficiency of genes, or cf. Beadle and Tatum (1941, especially pp. 499-500) who took for granted a control function of genes and formulate the one-gene-one-enzyme hypothesis. 89 Cf. Waters (1994, pp. 171-174) who claims that is was not even understood “what the genes’ contribution were.” 90 Cf. Mendel (1865, in particular the chapters 4-10, especially chapter 4 as regards the phenotypic features and the following chapters about their statistical distribution over the generations).

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Now, the connection between the inheritance of genes via the observed phenotypes and the behaviour of chromosomes becomes obvious. The inheritance probabilities of alleles as Mendel observed correlate with the behaviour of chromosomes during the process of meiosis. The biologists Sutton and Boveri recognized this correlation.91 Hence, they concluded that each of both alleles of one gene lies on one of the homologous chromosomes. Any diploid offspring usually gets one allele of a gene from the mother and one allele of the same gene from the father. This synthesis of Mendel’s results and the chromosome theory of Boveri and Sutton was modified by Morgan. He and his collaborators observed the phenotypic effects of two or more alleles that are lying on the same chromosome. Let us look at the details of Morgan’s famous April 1910 discovery of the white-eye male of Drosophila melanogaster. This male fruit fly possessed abnormal white eyes (called “mutant”) while the other fruit flies were all red-eyed (called “wild-type”). Morgan bred the white-eyed mutant male to a red-eyed wild type. But the following inheritance of the white-eyed mutation was special: in the first generation of offspring, there were only red-eyed offspring. These results were not yet special because the red eye colour of Drosophila could be dominant while the white-eye colour could be recessive as observed by Mendel and his experiments with pea plants (cf. ‘introduction to classical genetics’, this chapter, p. 208). To prove this idea of recessivity of the white-eyed mutant, Morgan carried out a brother-sister mating with the next generation. He found the expected Mendelian ratio for a recessive allele: only one white-eyed fruit fly to three red-eyed fruit flies. Thereby, Morgan expected an equal number of males and females carrying the white-eyed mutation. But, all female fruit flies had red eyes and the white-eyed mutation appeared only in males. Because of this unexpected result, Morgan concluded that the mutant allele lies on a chromosome that is also responsible for the sex of Drosophila melanogaster.92 Despite this special connection of the white-eyed mutant to the sex of the fruit fly, Morgan and his collaborators recognized in general a dependency between the probability of inheritance of alleles that are on the same chromosome: if two alleles are located on the same chromosome, a conjoint inheritance is not always given. The relative distance between the alleles on their chromosomes plays an important role. This distance dependency becomes clear by a process of crossing over. Crossing over 91 92

Cf. Boveri (1904) and Sutton (1903). Cf. Morgan (1910).

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means a change of genetic material between two homologous chromosomes during the process of meiosis. This change is expressed probabilistically, in the chance that a chromosome not be inherited in its original form. While the intersection of chromosomes could be microscopically observed, the change of the genetic material itself could not be observed microscopically. This change was only assumed in order to achieve a coherent explanation of the mentioned deviant statistical distribution of characteristics in the offspring generations. As our final consideration of these historical issues, let’s look at the recessive or dominant properties of the gene. Since Mendel’s rediscovery, it was well known in classical genetics that alleles can be dominant or recessive.93 In a simplified manner, a dominant allele produces always a phenotypic effect for the organism. There is no difference if the allele exists homozygously or heterozygously in that organism. For instance, the yellow colour of the pea seeds is dominant with respect to the green colour of the pea seeds such that 75% of the peas possess yellow pea seeds (3:1 ratio). To the contrary, a recessive allele produces only a phenotypic effect for the organism if the allele exists homozygously in that organism such as the green colour of the pea seeds. These properties of being dominant respectively recessive are well-proved statistical assumptions explaining phenotypic effects of alleles, but carried with them no explanation of the causal mechanism - which was not in fact explained in classical genetics. Let us term this ‘the importance of the gene concept’, and point to the historical facts going into the formulation of a gene concept that fit the paradigm of classical genetics. The orthodoxy about genes in classical genetics, after Morgan, was that they exist in form of two alleles in every diploid cell. Alleles cause phenotypic effects and lie on chromosomes. The inheritance of alleles is correlated with the behaviour of the chromosomes they are lying on. These connections are coherent and contain some kind of explanatory power. In fact, by means of the aspects considered in this section, it becomes clear how the gene concept is the fundamental thread holding together the connected issues of heredity, development and evolution. Therefore, I shall take the gene concept as the fundamental concept of classical genetics because everything in classical genetics is related to the genes (as they exist with respect to alleles). To put it another way, what classical genetics can state about a certain entity or event can be brought out by a corresponding gene concept. After all, everything in 93

Cf. Mendel (1865, especially chapter 4) who was the first to introduce these technical terms – even if he attributed them to specific characteristics of the peas such as the yellow colour of the pea seeds.

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genetics is related to genes. In the following section, I shall continue with my considerations of the gene concept in order to formulate a gene concept that represents classical genetics as an explanatory theory and will serve, by being more abstract, as useful for a comparison with molecular genetics.

iv.

Functional characterization of the gene

The concept of the gene can be functionally characterized. In this biological part, ‘characterization’ is preferred to the term ‘definition’ that I used in the general part, for the reason that I am reconstructing classical genetics in this chapter in order to use it in my reductionist approach in chapter VII. Thus, without leaving aside the history and the development of classical genetics and the fact that molecular genetics has developed out of classical genetics, I shall outline what remained indispensable of classical genetics. To put it another way, how it is possible to use classical genetics in order to construct functionally characterized concepts that are indispensable from a scientific point of view? Background of functional characterization:

Reconstruction of classical genetics (what is indispensable nowadays)

Conservative reduction Classical genetics and its development

Molecular genetics

Mendel 1865

Watson&Crick, etc. 1953-nowadays

(time) Correns, etc. 1900

Morgan, etc. 1910-1953

The general argument for such a functional characterization is based on its explanatory force: since one takes an explanation as a causal explanation, and since one takes the gene concept as being explanatory, it is the causal efficacy of genes that makes true the explanations by means of the gene concept. However, it is possible to distinguish between different concepts of biological functions. In regard to the mentioned issues, I shall begin with the explanatory aspect of the gene concept showing how this implies a law-like generalization, and finally take up the notion of a biological function in general to provide a functional

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characterization of the gene that will represent classical genetics in the following chapters. First of all, let me consider the gene concept as being an explanatory concept as outlined in detail in the previous section (cf. ‘the importance of the gene concept’, this chapter, p. 215). By means of the gene concept, biologists explain the occurrence of phenotypes such as the mentioned green or yellow pea seeds, the white eyes of the fruit fly, or other issues such as those ones concerning the inheritance. On the basis that the genotype of a certain set of organisms is known, it is possible to explain the statistical distribution of the genes among the offspring. Such explanations may take into account the so-called recessivity or dominance of genes, the unit character of genes, the possibility of mutations, the relative distance between genes on the chromosomes, etc., or they take into account, among other things, the cytological knowledge about chromosomes during meiosis. To sum up, the gene concept is explanatory. Second, let we take the implications of explanatory concepts to be about causally efficacity. This extends to the gene concept our previously constructed ‘concept of explanation’ argument (cf. p. 71). In this context, the explanations of the occurrence of phenotypes such as the mentioned yellow pea seeds or the white eyes of the fruit fly are based on the postulated causal efficacy of the genes in question. Similarly, the statistical distribution of the genes among offspring is explained by certain cellular mechanisms. Whether or not these mechanisms can be sufficiently described in detail in terms of classical genetics, they are still causal explanations. This is why we are not giving an argument to define any explanatory concept functionally. Since the notion of a biological function will be considered later on in more detail, the point I want to emphasize here is that in order to be an explanatory concept, the gene concept has to be characterized functionally. Third, let’s overview the implications of functionally characterized concepts. Any functionally characterized gene concept amounts to a lawlike generalization. Since functional characterizations are about causal relations, any functional characterization is law-like because causal relations come under law-like generalizations (cf. ‘concept of explanation’, chapter II, p. 71, and ‘functionally defined concept’, chapter II, p. 109). This means, a certain functionally characterized gene concept, such as the one about the gene that causes the yellow seed colour of the pea plant Pisum sativum, is a law-like generalization about the entities in question. To put it another way, any entity x that is a pea plant of the type Pisum sativum and that possesses a gene of the type Y (defined by its

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phenotypic effect: yellow seed colour) will produce yellow seeds, ceteris paribus. Let us bear in mind that this is how the gene concept is represented in classical genetics (cf. ‘importance of the gene concept’, this chapter, p. 215). Therefore, classical genetics can be in fact represented by law-like generalizations. Thus, we reply to the argument of the antireductionist strand, which holds that classical genetics cannot be represented by law-like generalizations (cf. ‘systematic framework’, chapter IV, p. 192). In order to represent classical genetics as an explanatory theory, it has to be represented by law-like generalizations. By means of such law-like generalizations (= functional characterizations), I shall compare classical genetics with molecular genetics in the following two chapters. Finally, let us take up what is meant by ‘biological function’. From a historical point of view, the definition of a biological function is expressed in terms of causal dispositions in the context of a fitness contribution, and thus replaced the so-called teleological definition of biological functions.94 This means, the notion of a function defined by an ultimate aim within evolution was replaced by the term “function” as something expressing purely the causal efficacy of properties in the context of natural selection.95 For instance, we do not describe hearts by their ultimate aim to pump blood when accounting for the reason they occur in order to provide an advantage in selection. Thus, hearts do not possess a function for something. Hearts are defined by their causal efficacy per se to pump blood that is essential for the fitness of the organism in question. In an oversimplified manner, organisms that possess hearts have advantages in the process of selection compared to organisms that do not possess hearts or heart-like organs. To sum up, hearts are functional properties defined by 94

Cf. Weber (2005, chapter 2.4) who outlines in detail the argument for this shift from the concept of a biological function as being something teleological to the concept of a biological function defined by a fitness contribution or contribution to the capacity of self-reproduction. My descriptions are in the spirit of Weber’s analysis. Let me note that I shall not distinguish between the functional definition of a property by means of its fitness contribution to the organism in question, or the functional definition of a property by means of its contribution to the capacity of self-reproduction to the organism in question. Cf. McLaughlin (2001) who connects the concept of a function to the capability of self-reproduction. This distinction is not relevant for us because this biological part is about genetics, and genetics only concerns organisms that are capable of self-reproduction and tries to explain this capacity. Furthermore, cf. Salmon (1998, chapter 4.5) who considers the term of a biological function in the context of scientific explanations. 95 Cf. Rosenberg & Kaplan (2005) who consider the principle of natural selection in detail.

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their fitness contribution for the organism in question and its environment. This shift takes into account the anti-teleological turn of modern science. In the context of this naturalization of biological functions, there are two approaches that focus on different aspects because their definitions are based on different criteria. On the one hand, there is the so-called aetiological definition of a biological function that mainly aims to provide an answer to the question why a certain property evolved by natural selection. To put it another way, the aetiological definition of a functional property is a hypothesis about the evolutionary history of the property in question. On the other hand, there is the causal-role approach to biological functions. Firstly, we will take up the aetiological approach, and then the other one as candidates for the definition of a biological function in the framework of my comparison of classical genetics and molecular genetics. In the aetiological theory, a functional property token is defined by what property tokens of the same type contributed to the fitness of the organisms in question.96 This approach is therefore about the historical past. What defines the functional property token in question depends on the fitness contribution of functional property tokens of the same type in the past. A present heart, for instance, is defined by the fitness contribution of heart tokens to their organisms in evolutionary history. To put it another way, hearts pumped blood that transports, among other things, oxygen and nutrients to the cells of the body. Thus, to pump blood contributed a fitness value to the organism in question. This explains why organisms nowadays still possess hearts. To sum up, the function to be a heart is defined by its selective advantage in the past. I shall not argue against this definition per se, because it provides causal explanations on questions such as why so different organisms like humans, birds, fishes, and worms possess hearts or heart-like organs. However, let me outline two shortcomings of this definition that are relevant in the context of my work. Let us therefore come back to the case of the gene, and consider a gene that is functionally defined by the aetiological approach. This means, for instance, that pea plants possess genes producing yellow blossoms because pea plants in the past that possessed genes producing yellow blossoms had a selective advantage compared to pea plants that did not. Thus, the gene in question is a functional property defined by those property tokens of the same type contributed in the past. However, let us now consider the very first occurrence of a gene of that type in the history of evolution. According to the aetiological theory, 96

Cf. Wright (1973).

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this gene token is not a functional property. There are no other property tokens of that type in the historical past, and hence, there is no fitness contribution that could define this very first gene token as a functional property. To take this gene not as a functional property seems to be contra intuitive. After all, depending on the organism and environment, it will contribute a certain fitness value to the organism in question. This suggests that we don’t have to look at the history of the gene tokens of that type to define functionally the gene in question. In general, the aetiological definition takes into account the fitness contribution in order to define the property in question functionally. However, it is unable to define the property in question as a functional one when that property occurs for the very first time. Let me regard the second shortcoming of the aetiological approach, and consider the well-known example of the appendix. It is possible to run the same argument with an aetiological definition of a certain type of gene, but in order to illustrate this second shortcoming, the case of the appendix is more illustrative. At one point, the appendix contributed a certain fitness value to the organisms in question. This explains why organisms such as humans possess an appendix. This fitness contribution is what defines the appendix as a functional property. But this fitness contribution more or less vanished. In fact, the appendix is still functional property – but more in contexts such as the possible perforation of the appendix that may be lethal. Leaving these exceptions aside, the appendix does not contribute any fitness value to humans any more. This means, the appendix in humans is, according to the aetiological theory, a functional property defined by the fitness contribution of appendix tokens to the organisms in the past. The point is that the aetiological theory does not take into account that the environmental conditions for the appendix have changed. To conclude, property tokens of the type “appendix” contribute nothing to the fitness of humans. But aetiologically, this is irrelevant. The aetiological approach, thus, provides functional characterizations of properties that do not depend on the current environmental conditions. Let me reconsider these two shortcomings in the context of this work. The aetiological definition of a biological function is not based on the current causal efficacy of the property in question. Therefore, it cannot take into account that the environmental conditions can change such that the functionally defined properties currently do not contribute any fitness value. They are in fact only dispositions to contribute a certain fitness value to the organism in question – but this dispositional character lies outside aetiological theory. To put it another way, the talk of dispositions

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is implicitly environmental, which makes it unsuitable for the aetiological approach. These shortcomings are relevant in the context of this work where I compare classical genetics with molecular genetics, and where I take the functional characterization of the gene as representative for classical genetics. Let us bear in mind, that, for instance, Mendel and Morgan postulated genes as causal efficacious entities that produce phenotypic effects. In this context, they considered only the current causal efficacy of genes, or their dispositions to produce phenotypic effects (given that, for instance, the alleles are homozygous in the proceeding generation). Our conclusion is that the shortcomings of the aetiological approach make its definition of function inappropriate for classical genetics. In classical genetics, genes are defined by their current causal efficacy or their disposition to produce certain phenotypic effects given the appropriate conditions. Keeping this in mind let me consider the other approach to a biological function that will fit the requirements for the comparison of classical and molecular genetics. The other way to define a functional property is by means of its current causal efficacy or its disposition to produce certain effects.97 Let me note at this very beginning that I do not use the usual term “causal role” to define a biological function because I would like to avoid connotations with the term “function” as defining what is alleged to be a second-order property. Against the background of the general part of this work, I shall take a functional property as a causally efficacious property in the world and this causally efficacy is both brought out in terms of the functional characterizations of the special sciences by means of relatively abstract concepts, and can also be described in terms of, in the last resort, physics. Such a functional characterization in terms of the special sciences is outlined in the general part of this work (cf. ‘functionally defined concepts’, chapter II, p. 109). According to this approach, a functional property is defined by what it synchronically contributes to the fitness of the organism in question, and by what it could contribute to the fitness of the organism in question given other environmental conditions. Thus, contrary to the aetiological approach, a functional property is defined by its synchronic causal efficacy and its causal dispositions. Let us consider once again a gene. Either, the gene token in question synchronically causes yellow blossoms or the gene token does currently not cause yellow blossoms because, for instance, it is wintertime. Nonetheless, it still possesses the disposition to produce 97

Cf. Cummins (1975) and Bigelow & Pargetter (1987).

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yellow blossoms. In the first case, there is an actual fitness contribution to the organism in question. In the second case, there is the disposition to provide a fitness contribution to the organism in question. Such a non-historical definition of a function (functional property), is therefore not subject to the shortcomings of the aetiological definition. It captures the concept of a causally efficacious gene as described by classical genetics. In general, any property in genetics is a functional property. It has at least the disposition to contribute a certain fitness value to the organism in question (given certain environmental conditions). For such an ascription, according to the defenders of the aetiological account, the historical dimension is necessary. Let me consider this claim that the historical dimension is necessary, and then regard the objection to this claim. The definition of a function as a causal disposition seems to be too broad because, in this approach, any biological property token is a disposition for more than we want to take into account in our functional analysis. For instance, the heart is not only the functional property (or disposition) to pump blood, but also to produce a certain noise. To take this production of noise as also defining hearts is contra intuitive and of no particular scientific interest (as far as I know). To put this shortcoming in general terms, it is possible to make a very long list of causal dispositions for any biological property. The claim is that there is no non-historical criterion to decide which of the listed dispositions actually define the property in question. It is suggested that the historical dimension as considered in the aetiological account is necessary to define the function in question. To put it another way, when defining the heart, it is only by historical considerations that we can give answers to the questions about why we prefer the criterion of a disposition to pump blood to that of producing a certain noise. . The objection to this claim is that it is actually possible to distinguish different dispositions in the context of a fitness contribution to the organism in question, and this distinction is not based on historical data.98 In order to distinguish the disposition to pump blood from the disposition to produce noise, it is sufficient to consider their contribution to the fitness of the organism in question. This contribution will certainly differentiate the disposition to pump blood from the disposition to produce noise. In order to carry out such a comparison, it is not necessary to take into account the historical dimension as considered in the aetiological 98

Cf. Weber (2005, especially pp. 38-41) where he outlines this argument in detail in the context of experimental biology.

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account. It will suffice to consider the synchronic contribution or the disposition of a contribution to the fitness in the expected life of the organism in question. On this basis, it possible to take the disposition to pump blood as the causal disposition that defines hearts. Against the background of these considerations, let me provide a general frame for a functional characterization of a gene that will serve as representative for classical genetics. This means, it considers the causal dispositions of genes. What is characteristic of the genes of a certain type is its causal disposition within a certain environment. Thus, I shall focus on the characteristic effects of genes in order to outline their contribution to the fitness of the organism in question. To simplify, I shall not distinguish between the genotype, genes and alleles. Another simplification we should bear in mind is that the causal relation between a gene and its phenotypic effects is not the one of one gene causing always only one phenotypic effect. In fact, on the one hand, one gene can cause a variety of phenotypic effects, and a single phenotypic effect can be caused by genes of different types. Nonetheless, an appropriate modification of this abstract functional characterization would not change the definition substantially. Functional characterization of a gene coming under the concept “B”: The characteristic effect of the gene tokens coming under the concept “B” for organisms coming under the concept “O” in environments coming under the concept “W” is their phenotypic effect coming under the concept “E”. This phenotypic effect coming under the concept “E” contributes a certain fitness value f to the organisms in question. Let me finally note that, in order not to complicate the issues, I restrict the functional characterizations of genes to the context of phenotypic effects. Of course, this is a restriction, and there may be cases (gene types) in which an appropriate characterization takes into account other issues. However, the point is that it is possible to provide a functional characterization in terms of classical genetics. Furthermore, most gene concepts are characterized in the context of their dispositions, their phenotypic effects. Therefore, I shall take the proposed functional characterization of genes as representative for my following analysis. The characterizations in terms of classical genetics bring out natural kinds – salient similarities among property tokens – and, thus, there is referential

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stability from classical genetics to molecular genetics. This means, there are entities in the world that are characterized functionally (in terms of classical genetics), and these entities, as we shall see in the next chapter, can be described in terms of molecular genetics as well.

v.

The explanatory limits of classical genetics

Classical genetics is limited in the range and the depth of its explanations. The explanations in classical genetics always presuppose the causal efficacy of genes and alleles without providing any explanations of this causal efficacy and the mechanisms between genotype and phenotype. In this context, classical genetics describes more or less the connections between the genotype and the phenotype, pictures the connections between alleles and chromosomes or illustrates their correlating probabilities of inheritance. Each explanation ends with the assumptions that there are entities such as genes or alleles, that genes or alleles cause the phenotypic effects, that these alleles behave with respect to inheritance like chromosomes during the meiosis that leads to sex cells, or that alleles can be dominant or recessive. In this sense, classical genetics seems to be some kind of ”that-theory”.99 Let me consider this explanatory limit in the context of the motivation of a reductionist approach. There are two connected points we should bear in mind. First, we consider classical genetics, even if limited, as somehow explanatory. And second, we consider the functional properties treated by classical genetics as causally efficacious (cf. ‘functional characterization of the gene’, this chapter, p. 220). These points lead to the following questions: facing the explanatory limits of classical genetics, is it possible that molecular genetics provides more powerful explanatory answers? In other terms, classical genetics often ends an explanation with assumptions and connections whereby no mechanism is explained. Questions like “What is the reference object of a certain gene concept?“, “What is the reason for the stability of a gene?”, “How does a gene produce phenotypic effects?” or “What is the mechanism of being a dominant allele?” are not explained in classical genetics. While classical genetics expresses that a gene has effects and is therefore causally efficacious, molecular genetics can explain of the gene 99

Cf. Waters (1994, pp. 165-174), and Kitcher (1984, p. 358) as being representative for the reductionist and the anti-reductionist strand.

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compositionally in order for it to have these characteristic effects, referring to the properties of DNA and its molecular context with its mechanisms of molecular interaction to do this. At the end of the next chapter, the motivation for a reductionist approach to classical genetics will be reconsidered in more detail.

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VI. Molecular genetics Preliminary remark The answer to the question of whether or not a gene is something molecular depends essentially on the answer to the question whether anything molecular can satisfy the functional characterization of genes that represents classical genetics.

Abstract The main aim of this chapter is to argue for the token-identity of genes with DNA molecules, and to motivate a reductionist approach to classical genetics. The argument for tokenidentity is based on two premises: the first premise is the concept of supervenience applied to property tokens of classical genetics and configurations of property tokens of molecular genetics – as outlined in the previous chapter. The second premise is the causal, nomological, and explanatory completeness of molecular genetics with respect to classical genetics. My premises lead toward the argument that shows how something molecular satisfies the functional characterization of genes in classical genetics. Functionally defined genes are, in a simplified manner, sequences of DNA. In the context of this token-identity and the completeness of molecular genetics with regard to classical genetics, I shall motivate a reductionist approach to classical genetics. Bearing these two aims in mind, I shall start with an introduction to molecular genetics that will clarify essential terms and provide a basic understanding of the molecular point of view on genes. These general considerations will be specified in the second section where I shall compare the causal dispositions of the DNA with the functional characterization of the gene that represents classical genetics.

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i.

Introduction to molecular genetics

In 1953, James D. Watson and Francis H. C. Crick discovered the DNA as the carrier of genetic information (cf. ‘historical framework’, chapter IV, p. 183). They analyzed the three-dimensional structure of the DNA and immediately inferred its mechanism of replication.100 This discovery was very significant as it opened up the way for a molecular understanding of genes, and thus, the essential issues genetics is about. Let me therefore describe the DNA molecule with its essential structure in order to illustrate Watson and Crick’s new perspective and understanding. The DNA consists structurally of four kinds of bases (adenine, guanine, thymine and cytosine) joined to a sugar-phosphate backbone. The linear sequence of bases carries genetic information, whereas the sugar and phosphate groups perform a structural role. I shall take the term genetic information as a causal disposition – the disposition of a specific sequence of bases to act as a template for their own replication and for the synthesis of enzymes. This is the so-called variable part of DNA. On the other hand, the sugar-phosphate backbone is invariable and insofar the structural part of DNA.101 DNA molecules consist of two helical chains of polynucleotides running parallel to one another. A polynucleotide consists of many nucleotides that consist of a base, a sugar and a phosphate. The two chains are coiled around a common axis such that they result in a double helix. Thereby, the bases (adenine, guanine, cytosine and thymine) of each chain are on the inside of the double helix, whereas the phosphate and sugar units are on the outside. With regard to the causal disposition of genes as defined in classical genetics, the genetic information in the form of the bases is situated on the inside whereby the structural backbone consisting of sugars and phosphates is situated on the outside. I note this point here, because the DNA double helix has to be unspooled (and that requires enzymes) in order to produce a phenotypic effect, unspooled. This fact already indicates the importance of the molecular context of the DNA, and I shall come back to this issue later on. The two chains of the DNA double helix are held together by hydrogen bonds between the pairs of bases at the inside of the double helix. The pairing bases are complementary. This means that adenine nucleotides in one chain are positioned across from thymine nucleotides in 100

Cf. Watson & Crick (1953a, 1953b, and furthermore 1954). Compare for the molecular structure of the DNA any standard textbook of genetics, for instance Stryer (1999, pp. 75-77).

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the paired chain, and vice versa (A-T), while guanine nucleotides in one chain are paired with cytosine nucleotides in the other chain, and vice versa (G-C). Let me outline an aspect of the DNA double helix that is important for us in order to understand the new molecular perspective: the specificity of the pairing bases (adenine always pairs with thymine (A-T), and guanine always pairs with cytosine (G-C)). In virtue of this specificity or complementarity, the DNA acts as a direct template for its own replication. Let me already note here that this is what is postulated in classical genetics under the term “unit character” of genes (cf. ‘the importance of the gene concept’, chapter V, p. 215). Moreover, the DNA acts as an indirect template for the enzyme synthesis that is necessary for the constitution of an organism. This means, genes, as regards the production of phenotypic effects, are causally efficacious. Let me focus in this section on the so-called replication of the DNA, and consider then the causal relation of the DNA to phenotypic effects. Replication is a molecular process that is necessary to the growth of an organism by inducing the formation of new cells and the synthesis of sex cells for the sexual reproduction. During the process of DNA replication, each of the complementary chains of the DNA double helix serves as a template for one another. For instance, a sequence of adenineguanine-cytosine-thymine (A-G-C-T) of the one chain is always paired with thymine-cytosine-guanine-adenine (T-C-G-A) at the other chain. This complementarity of the DNA is sketched below (see column “I. Double helix”). If the hydrogen bonds between the paired bases of the two chains are broken (by means of special enzymes), the chains of the double helix can be unspooled and separated. This separation is sketched below (see column: “II. Separated helices”). Each separated part of the DNA serves as a template for the formation onto itself – of a new complementary chain. This synthesis is sketched below (see column: “III. Separated helices as templates”). After this process of DNA replication from an origin double helix – via the separation into templates and the formation of two new and identical double helices – a strong relation between structure and function becomes obvious:

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I. Double helix:

A–T G–C C–G T–A

II. Separated helices:

A G C T

T C G A

III. Separated helices as templates:

A–T A– T G ←C G→ C C ←G C→ G T ←A T→ A

(A, G, C, and T: Nucleotides/Bases) ( – : Hydrogen bond between nucleotides/bases) This molecular mechanism of the DNA replication is mediated by a coordinated interplay of more than 20 enzymes. Against this molecular complexity, let us focus on some essential steps of the DNA replication to convey its mechanism. On the one hand, there are the two chains of the DNA double helix. Each of these chains constitutes a template of its complementary chain – as illustrated in the sketch I. On the other hand, special enzymes and molecular units (deoxyribonucleotides – dATP, dGTP, dTTP and dCTP) are necessary for the synthesis of the complementary “new” chains. This means, during an unwinding of the double helix, each base of the separated chains acts as a template for the synthesis of the complementary chain consisting of “new” bases (as symbolized by the underlined letters in column: “III. Separated helices as templates”). Thereby, special enzymes (DNA polymerases) are necessary to catalyze this sketched step-by-step addition of deoxyribonucleotide units to the new chains. After this synthesis of the respectively complementary chains, two identical double helices are constituted. Each double helix consists of one chain containing “old” bases and one chain containing “new” bases. Note that the formation of the structurally necessary sugar-phosphate backbone by a phosphodiester bond will be only catalyzed if the base on the incoming nucleotide (on the “new” chain) is complementary to the base on the template chain (the original, “old” chain). For this reason, the DNA polymerases are so-called template-directed enzymes. In general, these molecular mechanisms with the causal chain from one DNA double helix to its doubling essentially depend on the structural properties of the DNA and the molecular interplay of specific enzymes, and molecular substances. In principle, each step of the process of replication can be explained by the relational properties of the molecular substances in terms of molecular genetics. Let me now elaborate on the causal effects of the DNA regarding its phenotypic effects.

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Special sequences of the DNA cause the synthesis of enzymes. This is mediated by single strand molecules of mRNA and a complex of different enzymes. RNA is a ribonucleic acid that is structurally similar to DNA (deoxyribonucleic acid) as described above – both consist of four major bases, but RNA and DNA differ in one of them: RNA contains uracil (U) instead of thymine (T) as one base – while adenine (A), guanine (G) and cytosine (C) are the same in RNA and DNA. Additionally to this difference the bases of RNA are joined to a sugar-phosphate backbone that contain the sugar ribose (instead of the sugar deoxyribose as in DNA). Each kind of synthesized enzyme differs in its causal disposition with regard to the state, the metabolism and the development of the cell or the corresponding organism with its visible features. Let me note here that the DNA produces molecular effects in the cells, and thus, for the organism in question. As I shall outline in the following section, this causal efficiency of the DNA is what is attributed to genes in classical genetics. Let me therefore focus on three main steps of the causal relation from DNA sequences to their intracellular effects as described in molecular genetics. As will become clear later on in this chapter, these intracellular effects are the phenotypic effects that define genes. Of course, the term “phenotypic effect” is generally a term of classical genetics. However, I shall use it sometimes instead of the specific terms of molecular genetics describing the molecular effects for the cell, and thus, the organism. This will make the link between classical and molecular genetics easier to understand for my following analysis. In order to outline the causal process from the DNA to the phenotype, let me begin with the so-called transcription. The term “transcription” designates essentially the synthesis of RNA molecules from sequences of DNA bases. Thereby, special sequences of the DNA act as templates for RNA sequences. Such RNA sequences differ in their causal dispositions. Let me mention the essential ones: the so-called rRNA (ribosomal RNA) and tRNA (transfer RNA) are special RNA sequences that are important in the context of the process of translation that will be mentioned below in more detail. Furthermore, the so-called mRNA (messenger RNA) acts as a template for the synthesis of enzymes that will be described below in more detail as well. The molecular mechanism of the transcription itself is mainly carried out by a special kind of enzyme, the so-called RNA polymerase that synthesizes the RNA molecule. Each kind of a transcribed chain of RNA is complementary to its DNA template in the following sense:

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Adenine (A) in the DNA acts as a template for uracil (U) in the RNA: AU Thymine (T) in the DNA acts as a template for adenine (A) in the RNA: TA Guanine (G) in the DNA acts as a template for cytosine (C) in the RNA: GC Cytosine (C) in the DNA acts as a template for guanine (G) in the RNA: CG This mechanism of transcription is in some respects similar to the one of the replication of the DNA as described above. Their differences concern mainly their enzymes and their need of different molecular units. The RNA polymerases require the so-called ribonucleotides (ATP, UTP, TTP and CTP) for the synthesis of the transcribed RNA, whereas the DNA polymerases require the so-called deoxyribonucleotides (dATP, dGTP, dTTP and dCTP) for the replication of DNA. . Let me add that the transcription is usually ruled by complex mechanisms that vary in different organisms. Note furthermore that there can be specific molecular mechanisms for a modification of the transcribed RNA.102 Let me now outline the subsequent process of translation. The term “translation” designates essentially the synthesis of a chain of amino acids from transcribed sequences of mRNA. The process of translation can be sketched in the following way: it takes place in the cells at the so-called ribosomes that are complex assemblies of ribosomal RNA (rRNA) and special enzymes. Triplets of mRNA bases are called codons. Each codon can be bound reversibly by one type of specific transfer RNA (tRNA) at its template-recognition site. Each type of tRNA contains an amino acid attachment site where it can bind reversibly one type of amino acid. At the ribosomes, each codon of the mRNA will be bound reversibly by a corresponding tRNA (that has bound its corresponding amino acid) and the amino acids of the successive tRNAs will be bound together. For example, each mRNA codon UUU (uracil, uracil, uracil) will be bound by a tRNA that has bound the amino acid phenylalanine. In the same way, the 102

A more detailed description of the molecular mechanism of the transcription with its specific differences (for example the differences concerning different species or special mechanisms such as a posttranscriptional processing of the transcribed RNA) can be found in any molecular standard textbook, such as Stryer (1999, pp. 95-102 and pp. 841-871). But as mentioned above with respect to a comparison of molecular genetics and classical genetics, it will be sufficient to show only the main molecular mechanisms of the causal chain between the DNA and resulting cellular effects.

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mRNA codon GUG (guanine, uracil, guanine) will be bound by tRNA that has bound the amino acid valine. Therefore, an alternate mRNA sequence of the mentioned codons will be translated into a linear chain of the amino acids of phenylalanine and valine.103 After this simplified description of the translation, a few points about enzymes have to be emphasized. Each linear chain of amino acids will be modified by special enzymes before becoming an enzyme with a specific three-dimensional structure and specific functions. This means, the produced enzymes differ in their causal dispositions. Let me outline some of these dispositions in the following. In general, enzymes differ in their effects for cells, tissues, organs and, consequently, for the organism as a whole. Some of these effects will be mentioned to convey their importance for the organism. For instance, structural enzymes have structural effects – such as collagen or elastin – that form a fibrous framework in the connective tissue of animals. Storage enzymes store amino acids – like casein – that constitute the main source of amino acids for young mammals. Transport or carrier enzymes transport substances – such as haemoglobin, which transports oxygen in vertebrates. Regulatory enzymes catalyze and regulate biochemical reactions – like digestive enzymes, which support the digestion of food. By possessing these mentioned effects, enzymes form the phenotype. This means, from a molecular point of view, they produce and regulate the physical and physiological features of the cells, tissues or organs that constitute the features of the organism as a whole. The causal efficacy of the enzymes cannot be underestimated. In fact, no domain in the organism is unaffected, either directly or indirectly, by enzymes. To conclude, enzymes are generally defined by their causal dispositions, which play an essential role in the fitness of any organism. Let us term our theme, here, the ‘introduction to molecular genetics’, and use it to make a transition to the following section. The aboveexamined molecular structure of the DNA, the mechanisms of replication and enzyme synthesis and the specific effects of enzymes for the organism are what generally characterize molecular genetics. This means, there is a molecular understanding of issues of heredity and development. In the following section, I shall reconsider some of the mentioned issues in the 103

A more detailed description of the molecular mechanism of the translation with its specific differences (for example the differences concerning different species or special mechanisms like a linkage of transcription and translation at prokaryotes) can be found in every molecular standard textbook such as Stryer (1999, pp.102-115 and pp. 875-906).

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context of the functionally defined genes of classical genetics. This means, the functional characterization of genes of the previous chapter will be taken up again. Thereby, the leading question is how the DNA satisfies the functional characterization of genes.

ii.

Causal disposition of the DNA

The aim of this section is to provide an approach to the systematic link between classical genetics and molecular genetics. The guiding thesis is that the functionally defined concept of genes is made true by entities described as DNA in terms of molecular genetics. The molecular concept of the DNA with its molecular comportment of enzymes such as polymerases, molecular units like nucleotides and the molecular interplay of all them satisfies the functionally defined gene concept of classical genetics. In regarding these issues, I shall consider the causal disposition of the DNA, reconsider outlined issues of the previous section in the context of the functional characterization of genes, and compare directly the concept of the gene of classical genetics with the concept of the DNA of molecular genetics. Let me clarify the molecular concept of the DNA. This means, let us consider the DNA as described in terms of molecular genetics, and how this DNA satisfies the functional characterization of genes in classical genetics. For the mechanism of transcription, DNA uses special enzymes such as RNA polymerises; for the process of DNA replication, the socalled DNA polymerases are used. Furthermore, molecular substances are necessary for these processes – such as a reserve of corresponding amino acids for the synthesis of an enzyme for instance. It is obvious that the DNA per se is a dispositional property that can manifest the effects outlined in the previous section only in the context of, say, normal molecular conditions of the cell.104 In regarding this issue, the question is what exactly is the reference object of the gene. To put it another way, is it possible to localize the gene in terms of molecular genetics? I shall not define the exact limits of this molecular context of the DNA in general. This is neither possible in general, nor, necessary for the purpose of this chapter and this section in particular. It is not possible to provide an exact limitation because whether or not a certain DNA token actually causes a certain phenotypic effect depends on its molecular environment. Therefore, the actual causal efficacy of DNA tokens depends 104

Cf. Waters (1994, pp. 178-182) who outlines this context dependency in detail.

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on, say, normal cellular conditions. For instance, for the transcription of certain DNA sequences, special enzymes, enough ATP, and RNA nucleotides are necessary, for the translation of the transcribed RNA sequence, other enzymes, ATP, and amino acids are necessary, and so on… To sum up, a certain DNA sequence causes a certain cellular effect, ceteris paribus. The DNA is in its causal disposition, of course, context dependent. Let me now compare this ceteris paribus clause to the functional characterization of genes in terms of classical genetics. There are, as well, normal environmental conditions assumed. Genes manifest their causal dispositions to produce certain phenotypic effects only if there are no environmental obstacles that prevent this manifestation. This is why the environmental conditions such as, for instance, the ease of culturing, the controlling of the pollination, etc. of Pisum sativum were important aspects for Mendel to choose peas as experimental objects. In response to the experimental problem, Mendel tried to establish experimental standard conditions. Therefore, both in the case of classical genetics, and in the case of molecular genetics, the corresponding law-like generalizations include ceteris paribus clauses. The manifestation conditions of the causal dispositions of both the gene and the DNA depend on the environment. However, there is a crucial difference between both cases. The specification of normal conditions that can be expressed in terms of molecular genetics are generally more precise. Molecular genetics can specify the molecular conditions under which a certain DNA sequence actually produces a phenotypic effect in a detailed manner. To conclude, both the DNA and the genes require certain environmental conditions in order to be actually causally efficacious. The causal efficacy of both the DNA and the genes relies on more or less local conditions whereby molecular genetics can specify such conditions in a more precise manner than classical genetics can do. Thus, there is no conceptual problem to specify the reference object of the gene in terms of molecular genetics. This is generally the DNA. I shall reconsider these issues in the context of the argument for the token-identity of genes and DNA in the fourth section (cf. ‘argument for the token-identity of genes and DNA’, this chapter, p.247), and at the end of the chapter (cf. ‘motivation for the reductionist approach to classical genetics’, this chapter, p. 253). Keeping this general consideration in mind, let me consider the stability of genes and DNA. In classical genetics, the observable phenotypic differences and identities are connected with the assumption of there being stable genes as discrete units that will be transmitted from the

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parental generation to the offspring generation and that cause certain phenotypic effects (cf. ‘historical framework’, chapter IV, p. 183).105 For example, if both parents are homozygous for one gene, their offspring will be homozygous for that gene. In the other case, the probability of each offspring to be heterozygous for that gene is about 50%, if one of the parents is heterozygous for that gene. To explain the inheritance of phenotypic characteristics and their distribution in the offspring generations, the existence of a stable and causal efficacious entity – the gene – is postulated. At the molecular level, in a simplified manner, each cell usually consists of a membrane that separates an intracellular domain with its DNA, organelles, enzymes, nutrients, etc. from an extracellular domain. If we observe such a cell, one item will catch our attention: while all molecular components of the cell are in change over time, the DNA remains stable. For example, the number of lipids that compose the membrane will increase, organelles and enzymes will be synthesized or decomposed, nutrients will be transformed – but the DNA with regard to its specific sequence of bases usually does not change. Furthermore, the molecular structure of the DNA of a certain organism and of its offspring is identical (of course, only at the one half of the chromosomes, but the same holds for the gene in classical genetics). Against this background, the concept of the gene that includes being a stable substance that will be transmitted from parental generations to offspring generations is what is made true by the DNA. The DNA remains stable in its specific sequence of bases that occurs in the cells of the offspring organisms as well as in the cells of the parental organisms. Moreover, it is this DNA that causes the phenotypic effect that defines the gene in question. Let us look at this, the most important aspect of the gene concept, regarding the causal efficacy of genes – the phenotypic effects – from a molecular point of view. The DNA acts as a template for specific RNA sequences (as for the transcription of a specific mRNA). Each mRNA acts as a template for the synthesis of a specific chain of amino acids (for instance, in the case of a mRNA consisting only of uracil bases coding for a chain of amino acids consisting only of phenylalanine).106 Let me note that the type of enzyme that will be synthesized depends on the causal interaction between the translated chain of amino acids and special 105

Compare furthermore Waters (1994, pp. 169-170). Let me note that I take the term “code” synonymously with “cause”. This is in the spirit of Waters (2003) who considers the term “code” in detail.

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molecular substances and enzymes that transform the linear chain of amino acids into an enzyme with a specific conformation and causal disposition. As a result of this, any enzyme contributes its share to the state of the cell and consequently to the phenotype of the organism. Without describing these mechanisms in more detail, we can say that there are causal mechanisms on the molecular level and that molecular genetics explains causally the relation from the DNA to a certain phenotypic effect. In the last section of the chapter, I shall reconsider these issues on explanations and compare the explanations in terms of classical genetics with the explanations of molecular genetics (cf. ‘motivation for the reductionist approach to classical genetics’, this chapter, p. 253). At this point, let me emphasize the following issue: genes are essentially defined by their causal disposition to produce certain phenotypic effects (cf. ‘functional characterization of the gene’, chapter V, p. 220). The DNA satisfies this causal definition. Let us call this the ‘causal disposition of the DNA’. If we compare the causal disposition of genes defined in classical genetics and the causal disposition of the DNA outlined in molecular genetics, the similarities are obvious. This is why the DNA is generally taken to be the carrier of genetic information, to be the molecular structure of genes, to be the truthmaker of the gene concept of classical genetics. In order to develop out of these molecular considerations of this section an identity claim, I shall reconsider in the following section the causal, nomological, and explanatory completeness of molecular genetics with respect to classical genetics. On this basis, is possible to apply the argument for ontological reductionism outlined in the general part of this work to the case of the genes and the DNA in the next but one section.

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Relative completeness of molecular genetics

Our intuition is that the success of molecular genetics substantiates a completeness claim for this theory with respect to classical genetics. This means that molecular genetics is taken to be complete in causal, nomological, and explanatory respects with regard to classical genetics. In this context, I shall take the term “relative completeness” as an abbreviation in what follows. Let me furthermore note that, in order not to complicate the issue, I shall take molecular genetics as standing for a physical theory in comparison to classical genetics being a theory of the special sciences. After all, molecular genetics often takes into account concepts and explanations of chemistry, biochemistry, and physics. In this section, I shall consider our three types of the completeness claim and their mutual dependencies. Let me note that this section extends the ‘completeness of physics’, argument (cf. chapter I, p. 24), and the ‘incompleteness of the special sciences’ argument, (cf., chapter I, p. 29). First of all, let me consider the relative causal completeness of molecular genetics. This means that for any property token m g2 of molecular genetics, insofar as mg2 has a cause, it has a complete molecular cause, say mg1: mg1

mg2

(complete cause)

‘Complete’ means, molecular biologists would never need to have recourse to causes described in classical genetics. ‘Insofar’, because causation might be probabilistic. Nonetheless, molecular biologists always search for causes within molecular genetics, and not in the theory of classical genetics. To put it another way, there are no causes expressed in classical genetics that are taken to fill in any gaps that there may be in the causal relations between DNA, RNA, enzymes, etc. Suppose that these causal relations are probabilistic; molecular biology still completely determines the probabilities with respect to classical genetics. Prior occurrences of property tokens of molecular genetics and their law-like generalizations completely determine the probability of the occurrence of all property tokens of molecular genetics. . Molecular genetics furthermore provides the better explanation of these causal relations compared to the explanations in terms of classical genetics. To illustrate one case in point,

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molecular genetics may consider the causal disposition of a certain DNA sequence. To explain its causes and effects, we seek a complete explanation within molecular genetics with respect to classical genetics. Such an explanation is actually a causal explanation while classical genetics only postulates the causal efficacy of genes to produce phenotypic effects. Second, let me consider the relative nomological completeness of molecular genetics. Insofar as there are law-like generalizations that apply to m g2, there are law-like generations of molecular genetics that apply completely to mg2 with respect to classical genetics: mg1

mg2

(complete cause, and causal law)

‘Completely’ means, molecular biologists never need to have recourse to law-like generalizations of classical genetics. ‘Insofar’, because the law-like generalizations of molecular genetics that apply to mg2 might be probabilistic, or it might turn out that there are no law-like generalizations applying to m g2. If there were no such law-like generalizations of molecular genetics under which mg2 comes, molecular biologists might search in chemistry or physics. In any case, there would not be law-like generalizations in classical genetics either. This is what scientific experience suggests. To illustrate this, consider a DNA sequence, mg1 that causes, in a certain molecular context, the RNA transcription of the RNA sequence mg2. In order to explain this process of transcription, molecular biologists search for law-like generalizations under which this causal relation from mg1 to mg2 comes. To explain what happens when the DNA sequence mg1 causes the RNA sequence mg2, they seek for a complete explanation without having recourse to concepts and law-like generalizations of classical genetics. Let me consider the implication from relative causal to relative nomological completeness. Any relation between two property tokens that meets the conditions for being a causal relation between them also meets the conditions for being a law-like relation between the property tokens in question. Therefore, any relative nomological completeness claim is mainly based on the argument for the relative causal completeness. However, if there were no relatively complete law-like description in terms of molecular genetics, there would not be a law-like description of classical genetics either. This implication is based on the following assumption: there could not be a law-like generalization of classical

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genetics that fills any nomological gap of molecular genetics since there is the relative causal completeness of molecular genetics. For any causal change of property tokens of molecular genetics, there is a complete molecular (or, in the last resort, physical) cause, and hence, a relatively complete law-like generalization of molecular genetics under which this change comes. Suppose there were some law-like generalizations of classical genetics without there being a law-like generalization of molecular genetics (or, in the last resort, physics), then either molecular genetics (or, in the last resort, physics) would be causally not complete with respect to classical genetics, or the law-like generalizations of classical genetics would be about non-causal property tokens. In order to claim the first possibility, one would have to argue against the relative causal completeness of molecular genetics. In order to maintain the second possibility, one would have to argue for law-like generalizations of classical genetics that are about causally redundant property tokens (epiphenomena). As epiphenomenalism (as per our ‘redundancy of epiphenomena’ argument, cf. p. 31) is not a valid position, I shall not consider this option here. However, let us suppose that molecular genetics turned out to be incomplete in causal respects with regard to classical genetics. Since lawlike generalizations are considered to be causal law-like generalizations, molecular genetics would be incomplete in nomological respects as well. There would be non-molecular (or, in the last resort, non-physical) property tokens with causal powers that do not come under law-like generalizations of molecular genetics. For instance, some structural changes of a DNA sequence would have non-molecular (or, in the last resort, non-physical) causes. Since I shall focus on causal issues, let me take ‘law-like generalization’ as an abbreviation for ‘causal law-like generalization’. Any law-like generalization applying to an entity invokes the causes of the entity in question. If there is no molecular (or, in the last resort, physical) cause of an entity, there is consequently no law-like generalization of molecular genetics under which the entity could come. In this context, the relative nomological completeness of molecular genetics depends on its relative causal completeness. If molecular genetics were causally incomplete with respect to classical genetics, molecular genetics would not completely determine the probabilities of its considered causal relations. In such a case, the probabilities of a structural change of a DNA sequence would have to be traced back to non-molecular (or, in the last resort, physical) causes. Therefore, this causal change would not come under a law-like generalization of classical genetics, and one would have

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to go beyond molecular genetics (and, in the last resort, physics) and might be obliged to have recourse to law-like generalizations of classical genetics in order to account for molecular changes. Bearing these implications in mind, let me, third, outline the relative explanatory completeness of molecular genetics. This means that insofar as there is an explanation of mg2, there is a relatively complete explanation of mg2 in terms of molecular genetics: mg1

mg2

(complete cause, causal law-like generalization, and causal explanation)

‘Complete’ means, that in order to explain, molecular biologists do no go beyond the concepts embedded in molecular genetics. They do not have recourse to concepts and explanations of classical genetics. Molecular biologists always search for explanations of m g2 within molecular genetics (or, in the last resort, physics). If there is no explanation of m g2 in terms of molecular genetics, there is not an explanation in terms of classical genetics either. To illustrate this point, let us once again consider a DNA sequence. Assume once again that there is a RNA sequence mg2. In order to explain mg2, molecular biologists search for a molecular cause, mg1, and the appropriate law-like generalizations under which this causal relation from mg1 to m g2 comes. To explain the RNA sequence mg2, we seek for a complete cause and the appropriate lawlike generalizations within molecular genetics (or, in the last resort, physics). If there is a complete molecular (or, in the last resort, physical) cause, there will be a relatively complete law-like generalization of molecular genetics as well. If there is such a relatively complete law-like generalization, there will be a complete explanation in terms of molecular genetics with respect to classical genetics as well. This implication from nomological to explanatory completeness is based on the following assumption: any metaphysical consideration of two property tokens that meets the conditions for being a causal relation between them meets the conditions for being a law-like relation between the property tokens in question as well. This is all that is needed to give an explanation (cf. ‘concept of explanation’, chapter II, p. 71). Therefore, any relative explanatory completeness claim is mainly based on the argument for the relative causal completeness that implies a relative nomological completeness. Conversely, if there were no relatively complete explanation in terms of molecular genetics, there would not be a relatively complete

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explanation in terms of classical genetics either. This implication is based on the following assumption: there could not be an explanation of classical genetics that fills any explanatory gap of molecular genetics since there is the relative causal completeness of molecular genetics that implies a relative nomological completeness. For any causal change of property tokens of molecular genetics, there is a complete molecular (or, in the last resort, physical) cause, and hence, a relatively complete law-like generalization of molecular genetics under which this change comes, and this is sufficient for a causal explanation. Suppose there were an explanation of classical genetics without there being an explanation in terms of molecular genetics (or, in the last resort, physics), then either molecular genetics is causally (and thus explanatorily) not complete with respect to classical genetics, or the explanation of classical genetics is about non-causal property tokens. Otherwise, one would thus have to argue once again against the relative causal completeness of molecular genetics, or one would have to argue for law-like generalizations of classical genetics that are about causally redundant property tokens (epiphenomena). Finally, let us suppose that molecular genetics turned out to be incomplete in causal respects with regard to classical genetics. As a result of this, molecular genetics would be incomplete in nomological and explanatory respects as well. There would be non-molecular (or, in the last resort, non-physical) property tokens with causal powers that do not come under law-like generalizations of molecular genetics and that are inexplicable in terms of molecular genetics. For instance, let us image some structural change of a DNA sequence that would neither come under a law-like generalization of molecular genetics, nor could it be explained by molecular genetics because its causes were non-molecular (or, in the last resort non-physical). Let us keep in mind that I take ‘explanation’ as an abbreviation for ‘causal explanation’ (cf. ‘concept of explanation’, chapter II, p. 71). Any explanation of an entity invokes the causes of the entity in question. An explanation in terms of molecular genetics of a DNA sequence is a causal explanation. Therefore, the relative explanatory completeness of molecular genetics depends on its relative causal completeness. If molecular genetics were causally incomplete with respect to classical genetics, molecular genetics would not completely determine the probabilities of the causal relations. One might then have to go beyond molecular genetics (or, in the last resort, physics) and might be obliged to have recourse to concepts and explanations of classical genetics, since we would be witnessing a structural change of a DNA sequence that had

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non-molecular (or, in the last resort, non-physical) causes, thus obviously making an explanation in terms of molecular genetics insufficient. Let us term this the ‘relative completeness of molecular genetics’. Molecular genetics is complete in causal, nomological, and explanatory respects with respect to classical genetics. To put it simply, if there is a change of a molecular configuration, there is a relatively complete molecular cause for this change as well. If there is a relatively complete molecular cause for this change, there is a relatively complete law-like generalization of molecular genetics under which this causal change comes, and there is a relatively complete explanation in terms of molecular genetics of the case in question as well, and vice versa.

iv.

Argument for the token-identity of genes and DNA

Any gene token is identical with a certain DNA sequence. This is the token-identity of genes with configurations of molecular property tokens. Any causally efficacious gene token is identical with something molecular. Let me note that in order not to complicate the issue, I shall only consider DNA as the molecular base of genetic information. Any more detailed molecular consideration about other molecular structures to carry genetic information would pointlessly add details to our discussion without changing the themes of our argument in any way. After all, the concept of the DNA is the most central concept to understand genetics from a molecular point of view. Thus, let us consider the token-identity argument, advancing our thesis in five consecutive steps. This argument is in the spirit of the general part of this work (cf. in particular ‘token-identity qua causal efficacy and completeness’, chapter I, p. 51). First of all, we assume a gene token that can be described by a functionally defined gene concept of classical genetics (cf. ‘functional characterization of the gene’, chapter V, p. 220). This means, the gene token is causally efficacious, or has the disposition to produce a certain phenotypic effect. For instance, there is some gene token b1 that causes yellow blossoms b2: b1

b2 (causes)

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Our second step concerns the molecular supervenience base of b 1 and b 2. For instance, there are two different configurations of molecular property tokens that are described in molecular genetics, say mg1 and mg2. Provided that there are standard conditions in the environment, the molecular configuration mg1 is the supervenience base for the gene token b1, while some molecularly different configuration mg2 is the supervenience base for the yellow blossoms b 2 (cf. ‘concept of supervenience applied to classical genetics’, chapter V, p. 211): (gene) b1

(phenotype) b2 (Classical genetics)

(supervenes on) 

 (supervenes on)

mg1 (DNA)

mg2 (Molecular genetics) (molecular state)

In our third step, we claim any change in the molecular domain is sufficient to determine changes of the property tokens considered in classical genetics (cf. ‘concept of supervenience applied to classical genetics’, chapter V, p. 211). Therefore, if there is a causal relation from mg1 to mg2, this is sufficient to determine the change from b1 (gene) to b2 (yellow blossoms). Say, in a simplified manner that mg1 is a certain DNA sequence that causes a certain phenotypic effect mg2 described in terms of molecular genetics: Change from:

b1

to

is determined by  change from:

mg1

b2

(Classical genetics)

 (supervenes on) to

mg2

(Molecular genetics)

Fourthly, for any configuration of molecular property tokens mg2 that can be described by molecular genetics, insofar as mg2 has a cause, it has a relatively complete molecular cause (cf. ‘relative completeness of molecular genetics’, this chapter, p. 242). This relates to the molecular change between the DNA sequence mg1 and its effect mg2, insofar as one may take the molecular configuration mg1 as the complete molecular cause of the subsequent molecular configuration mg2. At least, the complete

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molecular cause of mg2 contains mg1. Nothing changes for the argument if there is some mg1 + mg1* that is the complete molecular cause of mg2. The point here is that there is a complete molecular cause with respect to classical genetics: b1

b2

(Classical genetics)

(causes) (supervenes on) 

mg1

 (supervenes on) mg2

(Molecular genetics)

(relative complete cause, causal law-like generalization, and causal explanation)

Our final and fifth step explains the three frameworks of understanding the causal relation between the gene tokens of classical genetics and the supervenience bases of molecular genetics, and why the most viable of those ways is token identity. Compare the gene token b1 of classical genetics with its molecular supervenience base mg1. The gene (b1) is taken to cause yellow flowers (b2) (step one). Both the gene (b1) and the yellow flowers (b2) supervene on molecular configurations (mg1 and mg2) (step two). Given that there is a causal relation between the molecular configurations mg1 and mg2, the occurrence of the yellow flowers (b2) is sufficiently determined by the occurrence of the molecular configuration mg2 (step three). In fact, the relative completeness of molecular genetics implies this. Thus, mg1 is taken to be the sufficient cause of mg2 on which the yellow blossoms (b2) supervene (step four). As a result of this, both b1 and mg1 seem to be sufficient for the occurrence of the yellow blossoms (b 2). The gene (b1) is taken to cause the yellow blossoms (b2), while mg1 is taken to cause (mg2 that is) the supervenience base of the yellow blossoms (b2). Against this background, there are three main possible relationships between b1 and mg1. First of all, let me consider systematic overdetermination in the case of genetics. This means that both the gene token b1 and the DNA sequence mg1 are sufficient and not identical causes of b 2. However, there are several arguments against this possible relationship in general (cf. in general ‘token-identity qua causal efficacy and completeness’, chapter I, p.51). Let me consider one of these arguments: the gene (b1) is no independent cause of the yellow blossoms (b2) because the gene token supervenes on mg1 that is taken to be the ‘competitive’ cause of b 2. The gene (b2) cannot be independent from mg1 since there is the supervenience relation (cf. ‘the concept of supervenience applied to classical genetics’,

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chapter V, p. 211). The gene (b 1) supervenes on the molecular configuration (mg1) that is itself sufficient for the occurrence of yellow blossoms (b2). However, if b1 is not independent from mg1, and if mg1 is causally sufficient for the occurrence of the yellow blossoms (b2), there is no reason for the assumption that b1 causes anything: b1 merely indicates that there is an underlying base m g1 that causes something. Molecular genetics by itself is relative complete in causal respects. Furthermore, causation is linked to law-like generalizations, and molecular genetics can express more precise, relatively complete law-like generalizations with respect to classical genetics. In order to put the problem for the causal efficacy of the gene token b1 in general terms, let us consider a molecular duplicate (say w2) of our world (say w 1). In addition to this, let us assume that genes are epiphenomena in w 2. Since w 2 is a molecular duplicate of our world in which molecular configurations (like mg1) are sufficient causes for yellow blossoms (like b2), by causing their supervenience base, there is no criterion to distinguish the causal efficacy of genes in our world from the epiphenomenal genes in w 2. This is why overdetermination leads to epiphenomenalism, which is no feasible ontological position (cf. in general ‘redundancy of epiphenomena’, chapter I, p. 31). As a result of this, we can discount the possibility of overdetermination in genetics. Second, there is parallelism. This means that both the causal relation between b1 and b 2, and the causal relation between mg1 and mg2 exist on different levels. It is the case that b1 causes b2, while mg1 causes mg2 that is sufficient (qua supervenience) for b 2. One may be inclined to say that the molecular configuration m g1 does not directly cause the yellow blossoms b2. However, the gene (b 1) supervenes on the molecular configuration (mg1), which is itself sufficient for the occurrence of yellow blossoms (b2). Consequently, if b1 is not independent from mg1, and if mg1 is causally sufficient for the occurrence of the yellow blossoms (b2) (even only qua supervenience of b2 on mg2), there is once again no reason for the assumption that b1 causes anything: the gene token b1 merely indicates that there is an underlying base mg1 that causes something. Molecular genetics by itself is sufficient (even qua supervenience). After all, causation is linked to law-like generalizations, and there these are expressed more precisely in terms of molecular genetics than in terms of classical genetics. Parallelism would be a plausible option only if classical genetics were equally as complete as molecular genetics. In order to put the problem for the causal efficacy of property tokens of classical genetics in general terms, let us consider once more a

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molecular duplicate (say w2) of our world (say w 1, in which I assume parallelism for the sake of the argument). In addition to this, let us assume that genes are epiphenomena in w2. Since w2 is a molecular duplicate of our world in which molecular configurations (like m g1) are sufficient causes for yellow blossoms (like b2), there is no criterion to distinguish the causal efficacy of genes in our world from the epiphenomenal genes in w2. This is why parallelism, too, leads to epiphenomenalism, which is no feasible ontological position (cf. in general ‘redundancy of epiphenomena’, chapter I, p. 31). In addition to this, there is one more consequence of parallelism: no property tokens of classical genetics would be causally efficient in the molecular domain. This is contrary to what experiences suggests. As a result of this, I shall leave aside the possibility of parallelism in what follows. Finally, there is token-identity. This entails taking the gene b1 as identical with its subvenient molecular configuration, the configuration of molecular property tokens mg1. The argument proceeds as follows: ‘the concept of supervenience applied to classical genetics’ (chapter V, p. 211) implies that the gene token b1 supervenes on a configuration of molecular property tokens mg1. In the same manner, ‘the concept of supervenience applied to classical genetics’ implies that b2 supervenes on mg2. The gene (b1) supervenes on the molecular configuration (mg1), and likewise the yellow blossoms (b 2) supervene on a molecular configuration (m g2). However, if there is a biological change (from b1 to b2), there is also an appropriate molecular change (from mg1 to mg2). The change dependency considered in the concept of supervenience implies this appropriate molecular change from mg1 to m g2. To put it simply, the molecular configurations have to be molecularly different. Supposing that the gene (b1) is the cause of the yellow blossoms (b 2), one may raise questions about whether there is also a sufficient molecular condition for the change from b1 to b 2. Indeed, the determination relation considered in the concept of supervenience implies that the molecular change from m g1 to m g2 determines the change considered in classical genetics. There is a molecular change that determines the change from the occurrence of the gene (b1) to the occurrence of the yellow blossoms (b2) that is considered in classical genetics. Furthermore, the ‘relative completeness of molecular genetics’ (this chapter, p. 242) implies that mg2 has a relatively complete molecular cause. This is mg1. Against this background, the gene (b1) and its subvenient molecular configuration (mg1) cannot be distinguished in a causal manner. In fact, mg1 causes mg2, and mg2 determinates b2 to occur. The molecular configuration (mg1) is a sufficient cause for the occurrence

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of the yellow blossoms (b 2) as well. Therefore, of the three frameworks, the token-identity of p1 and b1 is to be preferred (cf. in general ‘identity by causal indifference’, chapter I, p. 45). After all, in general, ‘property discrimination by causal difference’ (chapter I, p. 41) implies that any other difference between the gene (b1) and the molecular configuration (mg1) would imply causal differences between them. This is not the case. They cannot be causally discriminated. Consequently, there is a strong causal argument for the ontological reduction of b 1 to m g1. The gene (b 1) is identical with its subvenient molecular configuration (mg1). This is the DNA. Since the argument can be also applied to the yellow blossoms (b2), they are identical with their subvenient molecular configuration (mg2) as well: (gene) b1 (identical with)  mg1 (DNA)

(phenotype) b2  (identical with) (causes) mg2 (molecular state)

Let us term this section the ‘argument for the token-identity of genes and DNA’, and focus on the question how to understand this tokenidentity of genes and DNA. Since the concept of supervenience applies to classical genetics, any gene token considered in terms of classical genetics is identical with a configuration of molecular property tokens. To put it in general terms, since the two premises ‘relative completeness of molecular genetics’ and ‘the concept of supervenience applied to classical genetics’ are cogent, there is ontological reduction of any causally efficacious property token of classical genetics to configurations of property tokens of molecular genetics. This means, any gene token is identical with a certain DNA sequence that possesses the causal disposition to produce the phenotypic effects that define the gene token concept. . In this context, it is not necessary to take the whole molecular world as the molecular basis of the gene token in question. Again, the argument for this localization goes like this (cf. ‘causal disposition of the DNA’, this chapter, p. 238): from both points of view (classical and molecular genetics), normal environmental conditions are assumed in the law-like generalizations in which genes or DNA sequences figure. Genes manifest their causal dispositions to produce certain phenotypic effects only if no environmental obstacles prevent this manifestation, and the same holds for the DNA sequences to be transcribed, etc. Thus, in both cases, the law-like genetic

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concepts include a ceteris paribus clause. Furthermore, we can find more precise specifications of normal conditions in terms molecular genetics. Against this background, we have clear and sufficient reasons to take the causal disposition of a certain DNA sequence as the molecular property token with which the gene token in question is identical.

v.

Motivation for the reductionist approach to classical genetics

A reductionist approach to classical genetics seems to be implied by our argument for the token-identity of genes and DNA, plus the relative completeness of molecular genetics. This approach also takes into account that classical genetics often cannot provide explanations of causal relations but only postulate them. Let us weigh the factors that motivate the reductionist approach as they have accumulated over this and the two previous chapters. First of all, there is the molecular explanation of dominance and recessivity. It is postulated in classical genetics that there are alleles that are dominant or recessive. This postulation makes it possible to provide an explanation for the statistical distribution of phenotypic effects (cf. ‘historical framework’, chapter IV, p. 183). However, classical genetics cannot give us a causal explanation for this dominance or recessivity (cf. ‘the explanatory limits of classical genetics’, chapter V, p. 228). Let us bear in mind that alleles are identical with certain sequences of DNA (cf. ‘argument for the token-identity of genes and DNA’, this chapter, p. 247). If there is no molecular difference between the two alleles of one gene, the organism in question is homozygous for that gene. On the other hand, if an organism is heterozygous for a certain gene, there has to be a molecular difference between the two corresponding DNA sequences in question (cf. ‘concept of supervenience applied to classical genetics’, chapter V, p.211). If one observes two different DNA sequences that are the two heterozygous alleles for the gene in question, usually each of both sequences is transcribed into mRNA. This mRNA sequence will be translated into a chain of amino acids that will be transformed into an enzyme with a specific function. In each case of synthesis, the enzymes differ in their amino acids and differ therefore in their conformation and functionality (cf. ‘introduction to molecular genetics’, this chapter, p. 232, and ‘causal disposition of the DNA’, this chapter, p. 238). I shall leave aside the possibility of multiple realization that will be considered in detail

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in the next chapter (cf. ‘the multiple realization argument applied to genetics’, chapter VII, p. 262). In order to illustrate this difference, let me say that only one of both types of enzymes is digestive, has structural effects, or transports oxygen while the other does not. In the context of Mendel’s experiments, only one of the alleles (DNA sequence) produces an effect that can be observed. In this context, in heterozygous organisms only the dominant alleles are taken to be the cause for the phenotype while recessive alleles only cause a phenotypic effect if the alleles are given homozygously in the organism in question. In this context, let me highlight a case that illustrates the explanatory advantages of molecular genetics: that of the recessive allele for sickle-cell anaemia in organisms that are homozygous for that gene. Heterozygous organisms for that gene have no symptoms of that disease. As mentioned above, being a dominant or recessive allele is identical with a certain sequence of DNA that acts as template for the corresponding enzyme that causes the mentioned phenotypic effect. According to the example, the molecular DNA sequences of the allele for the sickle-cell anaemia differ in one nucleotide from the “healthy” allele – one adenine instead of thymine at the DNA sequence that codes via mRNA and tRNA for the ß-chain of haemoglobin. This difference of only one base at the DNA causes a different mRNA during the transcription that leads to a different chain of amino acids (the codon of the mRNA is guanine-uracil-adenine that codes for the amino acid valine instead of the “healthy” mRNA codon guanineadenine-adenine that codes for glutamic acid) and for that reason, the resulting enzymes differ in their causal disposition. This means, in terms of molecular genetics, that the solubility of deoxygenated sickle haemoglobin is abnormally low and causes a deformation of the red cells in form of a sickle shape and the known symptoms of the disease.107 Let me sum up the mentioned issues. The property of being dominant or recessive is explained in terms of molecular genetics, while it is unexplained in terms of classical genetics. A phenotypic effect of a recessive allele will be only visible if both corresponding sequences of the DNA produce the same enzyme that causes this effect. In the case of heterozygosity, the DNA sequence for the dominant allele codes for enough enzymes so that no difference to homozygous organisms for that gene will be observable. 107

Compare for a detailed analysis of the molecular basis of the sickle-cell anaemia any standard textbook such as Stryer (1999, pp.169-174). Cf. Kitcher (1999) where he concedes the explanatory power of molecular genetics with regard to the sickle-cell anaemia (1999, p. 32).

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In general, as shown in the previous chapter, classical genetics bases its assumptions about the gene mainly on the observable features of phenotypic differences and identities over generations of specific organisms and the behavior of chromosomes. For instance, the gene as a stable substance seems to be mainly a plausible assumption that is necessary in order to explain the distribution of the phenotypes. But the reference object of the term “gene” cannot be identified and the property of being a stable unit, the mechanism of the causal efficiency of genes and the reasons for being a dominant allele are not explained in classical genetics. Nevertheless, the probabilistic distributions of genes with regard to their inheritance from parental generations to offspring generations seem to be in principle right. The underlying concept of the distinction between genotype and phenotype of an organism is a heuristic aid as far as heredity, development, and evolution are concerned. This level of adequacy of biological descriptions can be summarized in functional characterizations of the respective types of genes as sketched out in an abstract way in the previous chapter. On the other hand, molecular genetics contains assumptions about molecular properties and mechanisms like being a helical chain of DNA or the causal process during the translation of mRNA into a chain of amino acids. These molecular mechanisms are explained by the molecular interaction of the molecules with their relational physical and biochemical properties. We will call this section the ‘motivation for a reductionist approach to classical genetics’, explaining it in the following way: the main difference between classical and molecular genetics is that they give us two distinct theories about the same entities. Without any doubt, classical genetics provides explanations that are of scientific interest. But there are causal properties considered in classical genetics that remain unexplained in terms of classical genetics. Such unexplained property tokens can often be explained in terms of molecular genetics. To put it another way, taking the token-identity of genes and DNA for granted, classical genetics cannot explain its target entities with the precision of molecular genetics. This motivates a reductionist approach to classical genetics, allowing us to establish: a systematic relationship between the concepts; law-like generalizations; and, thus, explanations of classical genetics, with concepts, law-like generalizations. Which, furthermore, gives us explanations of molecular genetics. Let us bear in mind that a reductionist and molecular approach to classical genetics does not distort its concepts

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and descriptions. To the contrary: molecular genetics confirms all adequate and true concepts, law-like generalizations, and explanations of classical genetics, defines their reference objects on the molecular level and explains the causal mechanism, etc. Against this background, the challenge now is to establish such a conservative reductionist approach. This will be the aim of the following chapter.

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VII. Reduction of classical genetics to molecular genetics Preliminary remark The question of reductionism in genetics is not whether reduction is possible, but how classical genetics can be reduced to molecular genetics. To put it another way, has classical genetics been replaced by molecular genetics, or is there some remaining indispensable scientific quality of classical genetics?

Abstract The main aim of this chapter is to reduce conservatively classical genetics to molecular genetics. I shall being applying the reductionist strategy outlined in the general part to the relationship between classical and molecular genetics, given my biological outline in chapters V and VI. This chapter will begin with a short summation of our previous three chapters about both genetic theories. Taking this as a starting point, I shall consider the so-called multiple realization argument in the context of genetics. To put it another way, the probably most compelling argument of the anti-reductionist strand will be considered in detail. In this context, I shall outline the dilemma for any anti-reductionist position that is based on the multiple realization argument. This argument leads in fact to the expulsion of classical genetics from a scientific view of the world. In order to avoid such a consequence, I shall propose a reductionist approach to classical genetics that ends up in a conservative (non-eliminative) reduction. This approach work in terms functionally defined sub-concepts of the gene concept that are nomologically co-extensional with constructed concepts of molecular genetics. By means of this construction, it is possible to justify the indispensable scientific character of classical genetics within a reductionist approach. Finally, I shall reconsider several central issues of my reductionist approach in a more general framework.

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Introduction to the relationship

We have established the reasons for enacting a reductionist approach to classical genetics. After all, there is the argument for the token-identity of genes and DNA, and there is the relative completeness of molecular genetics. But we have not considered the multiple realization argument, which does seems to exclude a reductionist approach to classical genetics. The concepts of both genetic theories are often not co-extensional, but coextensionality is necessary for theory reduction. Let me sum up the essential issues of the previous three chapters in order to provide a starting point for this last chapter. Against this background, I shall introduce the mentioned multiple realization argument of the anti-reductionist strand. First of all, let us bear in mind law likeness and centrality of the gene concept of classical genetics. Since the gene concept is explanatory, and since one takes an explanation to be a causal explanation, it is the causal efficacy of genes that makes true the explanation by means of the gene concept. For instance, the explanation of the occurrence of phenotypes such as yellow pea seeds or white eyes of the fruit fly is based on the postulated causal efficacy of the genes in question. In this context, any functionally defined gene concept amounts to a law-like generalization. Since functional characterizations are about causal relations, any functional characterization is law-like because causality comes under lawlike generalizations. For instance, the functional characterization of the genes that produce yellow pea seeds is a law-like generalization (cf. ‘functional characterization of the gene’, chapter V, p. 220). Such law-like generalizations apply to the gene concept of classical genetics, which is fundamental for that science (cf. ‘importance of the gene concept’, chapter V, p. 215). Second, let us keep in mind the token-identity of genes and DNA. The argument goes as follows: genes supervene on configurations of molecular property tokens (cf. ‘concept of supervenience applied to classical genetics’, chapter V, p. 211). Genes are functional properties (cf. ‘functional characterization of the gene’ chapter V, p. 220). The DNA satisfies the functional characterization of genes (cf. ‘causal disposition of the DNA’, chapter VI, p. 238). Since molecular genetics is complete causally with regard to classical genetics (cf. ‘relative completeness of molecular genetics’, chapter V, p. 242), there genes have token-identity of with DNA (cf. ‘argument for the token-identity of genes and DNA’, chapter VI, p. 247). Third, the factors that motivate the reductionist approach as follows: assume the token-identity of any gene token that is described in terms of

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classical genetics with DNA sequences that are described by molecular genetics. This means, there are two theories that are about the same entities in the world. Genes can be described in terms of molecular genetics. This raises questions about the relationship between both genetic theories. If we take into account that molecular genetics is relatively complete in causal, nomological, and explanatory respects, this strongly argues for a reductionist approach (cf. ‘motivation for the reductionist approach to classical genetics’, chapter VI, p. 253). Any entity that is described or explained in terms of classical genetics can be described and explained in terms of molecular genetics as well. Moreover, molecular genetics provides more precise and more detailed descriptions and explanations. This suggests that the law-like generalizations (the functional characterizations of types of genes) of classical genetics can be reduced to constructed concepts and law-like generalizations of molecular genetics.108 Furthermore, molecular genetics can explain systematically what remains unexplained in terms of classical genetics (cf. ‘explanatory limits of classical genetics’, chapter V, p. 228). Fourth, let us consider the relation of supervenience to the reductionist argument. Given the token-identity of genes and DNA, the concept of supervenience is more appropriate in the context of concepts than in the context of property tokens. After all, token-identity is a stronger relation than the relation expressed in the supervenience concept. Thus, the truth-value of descriptions of classical genetics supervenes on the description of the entities in question in terms of molecular genetics (compare for my general analysis ‘supervenience of truth-values’, chapter II, p. 79). This means, a description of an entity in terms of molecular genetics determines how to describe this entity in terms of classical genetics. Provided that genes are DNA sequences, the molecular description of such a DNA sequence determines how to describe this entity in terms of classical genetics. Furthermore, any difference in the description in terms of classical genetics depends on an appropriate difference of the molecular description. It is not possible that classical genetics can, for instance, distinguish between two types of genes without there being molecular differences. To sum up, taking the argument for the

108

Cf. Hooker (1981, pp. 49-52) who outlines in detail the construction of coextensional concepts. This construction is also considered in the general part (cf. ‘Nagel’s model of reduction’, chapter II, p. 89). The following analysis bears in mind this construction of concepts that will be reconsidered later on in more detail (cf. ‘reduction of classical genetics to molecular genetics’, this chapter, p. 289).

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token-identity of genes and DNA for granted, I shall apply the concept of supervenience only to truth-values of concepts in what follows. Finally, we get to the multiple realization argument of the antireductionist strand (cf. ‘systematic framework’, chapter IV, p. 192). In this chapter, I shall leave aside any anti-reductionist argument that is not based on multiple realization. These arguments were already considered (and refuted) both in the fourth chapter (cf. ‘the approach’, p. 199), and in chapters V and VI. Against this background, I shall take the multiple realization argument as the anti-reductionist’s most compelling argument. This section, then, is devoted to a consideration of this argument and its consequences for the relationship between classical and molecular genetics. Let me restate the multiple realization argument in the context of genetics: the proper concepts of both genetic theories cannot be biconditionally linked because they are not co-extensional. The concepts of classical genetics often refer to property tokens that come under different constructed concepts of molecular genetics. For instance, the functionally defined concept “gene that produces yellow blossoms” of classical genetics brings out in a homogeneous way salient causal similarities among gene tokens that are differently described in molecular genetics. Leaving aside molecular details at this point, there are different DNA sequences that can be referred to by “gene that produces yellow blossoms”. For that reason, there is an asymmetry between the functionally defined gene concepts of classical genetics and the corresponding DNA concepts of molecular genetics. Abstracting from details, there is on the one hand a functionally defined gene concept of classical genetics, say “gene that produces X” that describes a certain set of entities and brings out their salient causal similarities. But on the other hand, there are different constructed concepts of molecular genetics that describe the genes in question. Let me call them “DNA sequence X1”, “DNA sequence X2”, etc. Thus, the concept “gene that produces X” cannot be bi-conditionally linked to one molecular concept such as “DNA sequence X1”.109 This anti-reductionist argument is based on the following consideration: the genetic code is redundant. This means, different sequences of DNA bases can produce the same protein. Bear in mind that 109

Compare with regard to a multiple realization in the sense of an asymmetric relation between classical genetics and molecular genetics Vance (1996, pp. S36-S39). Compare furthermore Kitcher (1984, pp. 343-346) who outlines the disjunctive nature of the molecular configurations of a gene.

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the DNA will be transcribed into an mRNA sequence, and this mRNA will be translated into a chain of amino acids. At this point, a triplet of ribonucleotides codes for an amino acid of a certain type. For instance, each mRNA codon UUU (uracil, uracil, uracil) will be bound by a tRNA that has bound the amino acid phenylalanine. In the same way, the mRNA codon GUG (guanine, uracil, guanine) will be bound by tRNA that has bound the amino acid valine. However, phenylalanine and valine can also be coded by other mRNA triplets: phenylalanine will be coded also by the mRNA triplet UUC, and for valine, there are three other mRNA codons possible – GUU, GUC, and GUA.110 Therefore, different DNA sequences may result in the same type of protein. This suggests that there are molecular differences possible that vanish on the descriptive level of classical genetics. Even more precise, there are molecular differences that vanish at some point in the molecular causal relation that defines the gene in question. As a result of this, the concepts of classical genetics cannot be bi-conditionally linked with concepts of molecular genetics. This section, which we will term the ‘introduction to the relationship,’ sets up the problem posed by multiple realizability for the reductionist program. On the one hand, there are factors that motivate a reductionist approach to classical genetics: the representative character of functionally defined gene concepts, the argument for the token-identity of genes with DNA, and the relative completeness of molecular genetics. This all suggests the reduction of gene concepts to DNA concepts. On the other hand, the multiple realization argument seems to exclude such a reductionist approach to classical genetics because the functionally defined gene concepts cannot be connected bi-conditionally with DNA concepts of molecular genetics. To conclude, if it is not possible to reduce the representative gene concept to molecular genetics, it is not possible to reduce classical genetics. In the following section, I shall outline a dilemma for the anti-reductionist strand that is based on the multiple realization argument.

110

A more detailed description of the redundancy of the genetic code can be found in any standard textbook such as Campbell (2005, p. 314).

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ii.

The multiple realization argument applied to genetics

Multiple realization implies that the realizers causally differ.111 To come under different concepts of molecular genetics implies to differ causally. For instance, if the molecular realizers of a gene that produces yellow blossoms come under different (constructed) molecular concepts, this means that there are causal differences between the molecular realizers. The molecular configurations differ in their composition and this implies that they figure in different causal relations with their molecular environment. Let us bear in mind that in the context of token-identity, multiple realization is multiple reference: one and the same gene token is described by means of concepts of different genetic theories – “gene …” or “DNA …”. In this context, the concepts of classical genetics are not coextensional with the concepts of molecular genetics. To speak of multiple reference rather than of multiple realizations must also take into account the fact that genes are functional properties – and not entities that simply have a function. There is no causal role that the DNA literally realizes, but there are genes that are functional properties, and these genes are identical with certain DNA sequences (cf. functional characterization of the gene’, chapter V, p. 220). Let us keep this in mind in what follows since I shall sometimes use the term “realization” because it is common in the discussion about the relationship between classical and molecular genetics. Let me consider in this section first of all the requirement and the implication of the multiple realization argument. Against this background, I shall outline the implicit dilemma for the anti-reductionist strand that is based on the multiple realization argument. First, let’s summarize the multiple realization argument. Multiple realization means that property tokens that come under one single gene concept of classical genetics come under different DNA concepts of molecular genetics. For instance, there may be gene tokens that are, in terms of classical genetics, homogeneously described by the concept “gene that produces yellow blossoms”. However, these genes for yellow blossoms differ molecularly. There are DNA sequences possible that differ in their composition, in their sequence of DNA bases, but produce nonetheless proteins of the same type that result in the same phenotypic effect as described by “yellow blossoms”. Based on this, they are described by means of different constructed concepts, such as “DNA 111

Cf. Kim (1999, pp. 17-18).

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sequence X1” or “DNA sequence X2”. In any case, each of these molecular configurations is identical with a gene token that produces yellow blossoms. Second, let me consider the implication of the multiple realization argument in detail. If property tokens come under different concepts of molecular genetics, then there are causal differences between the property tokens in question. It is not possible that two gene tokens come under different DNA concepts of molecular genetics if there are no causal differences between the DNA sequences in question. The argument is that any conceptual distinction between property tokens within the vocabulary of one science implies a causal difference. Molecular configurations that differ in their composition differ in the causal relations in which they stand as well vide our argument, ‘property discrimination by causal difference’ (cf. chapter I, p. 41). Given that the DNA sequences that are identical with genes come under different concepts of molecular genetics, this conceptual distinction implies that they are DNA sequences that causally differ. For instance, those DNA sequences described by the concept “DNA sequence X1” stand in different causal relations with other molecules in their environment than the DNA sequences described by “DNA sequence X2”. To put it in terms of dispositions, the DNA sequences of type X1 possess the disposition to stand in other causal relations than the DNA sequences of type X2. Let us bear in mind that types are concepts. In this context, DNA sequence of type X1 is an abbreviation for a more detailed molecular description of the DNA sequences in question. This means that there are differences in the way in which the molecular configurations satisfy the functional characterization of the gene in question. Since certain molecular configurations such as those ones of the DNA sequences of type “X1” and those ones of the DNA sequences of type “X2” are identical with genes that produce yellow blossoms, each fulfils the functional characterization applicable to the type of gene in question. In terms of classical genetics, each of the DNA sequences of type “X1” and of type “X2” is a gene token that comes under the concept “gene that produces yellow blossoms”. However, each molecular configuration of a certain type, such as the DNA sequences of type “X1”, satisfies the functional characterization of the gene in a specific way. If there are causal differences between the molecular configurations of the DNA sequences of type “X1” and type “X2”, then they produce yellow blossoms differently. . To put this in terms of a reductive explanation, the production of yellow blossoms will be reductively explained in two different ways: gene tokens equivalent to DNA sequences of type “X1”

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produce yellow blossoms in a way that differs with respect to gene tokens that are identical with DNA sequences of type “X2”. There are two different reductive explanations (cf. concept of explanation’, chapter II, p.71): Implication of multiple realization of the gene: DNA molecules causally differ, they possess different causal dispositions. Third, let me outline the consequence of this causal difference. The multiple realization argument raises questions about the scientific value of classical genetics. If a gene concept of classical genetics is about entities that come under different DNA concepts of molecular genetics, it abstracts from ontological details. The molecular differences between these DNA sequences (such as between those of “X1” and “X2”) imply ontological differences (because of difference composition) that are not considered in the concept “gene that produces yellow blossoms”. Since it is not possible to deduce each gene concept of classical genetics from a single constructed DNA concept of molecular genetics, the ability of classical genetics to focus on salient causal relations of genes is put into question. Moreover, it seems that only the deducibility from molecular genetics could justify the scientific character of classical genetics – to provide correct explanations on issues of heredity. In this context, I shall reconsider the so-called newwave reductionism that amounts to, in the last resort, the elimination of the scientific character of classical genetics (cf. my general considerations in ‘critique of the multiple realization argument’, chapter II, p. 133). We can summarize the relevant issues at this point as follows: ontological differences imply causal differences (cf. ‘property discrimination by causal difference’, chapter I, p. 41), and ontological identity (token-identity) implies causal indifference (cf. ‘identity by causal indifference’, chapter I, p. 45). Thus, molecular differences between DNA sequences coming under different concepts should imply ontological differences. Molecularly and thus causally different DNA sequences that are genes, and that both produce yellow blossoms, differ ontologically. The DNA sequences of type “X1” differ ontologically from those ones of the DNA sequences of type “X2”. Taking ontological reductionism for granted, thus, the token-identity of genes and DNA, the functionally defined gene concepts of classical genetics and the DNA concepts of molecular genetics are about the same

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property tokens. This means that, because of token-identity, there should be no ontological differences in the referents of these concepts. . The gene tokens are just described in different ways by means of different concepts – on the one hand by “gene that produces yellow blossoms”, on the other hand by constructed concepts of molecular genetics such as “DNA sequences X1” (“X1”) and “DNA sequences X2” (“X2”). This means that classical genetics uses one and the same concept in order to explain ontologically different property tokens. Contrary to this, the concepts of molecular genetics take into account those ontological differences. To put it another way, the gene concept abstracts from molecular details and thus ontological details. “Gene that produces yellow blossoms” does not consider the ontological differences between the molecular configurations of the genes in question. But, nonetheless, the gene concept of classical genetics is taken to be about causal relations. Even more strictly, the gene concept is functionally defined, thus about functional property tokens. However, from a molecular point of view, the causal relations that are summed up under this single concept “gene that produces yellow blossoms” are different. This raises questions about how classical genetics can abstract from molecular and thus ontological details and focus nevertheless on salient causal relations. After all, the two relata and the causal relation are often molecularly different. For instance, the gene tokens differ molecularly, the yellow blossoms differ molecularly, and the causal relation from the genes to the yellow blossoms differs molecularly. The supervenience of the truth-values of the concepts of classical genetics on the truth-values of concepts of molecular genetics does not explain this abstraction from ontological details. It seems that such an abstraction can only be justified by means of a deduction of the functionally defined concepts of classical genetics from molecular concepts. This, however, suggests that there is also a molecular homogeneity between the DNA sequences that is sufficient to explain the causal disposition of genes. But, if this were the case, there would be no multiple realization. There are of course obvious similarities between different DNA sequences. For instance, the sequences of DNA bases cannot differ totally while coding for the same protein, and the structural properties of the DNA double helix are similar. However, the point in favour of the multiple realization argument is that molecular genetics cannot abstract from the differences in the sequence of DNA bases. To put it another way, molecular genetics has to take into account molecular details such as the different sequence of DNA bases in order to

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explain the mechanism of transcription that leads to the production of proteins (phenotypic effects). In this context, can we turn to Kim’s position on these matters to find a reductionist solution? It turns out that the answer given by Kim’s extension of local reduction to species/structure-specific reduction does not suffice, because the species/structure-specific concepts are not functionally defined (cf. ‘consequences for Kim’s model’, chapter II, p.123). This means, the abstraction from ontological details is not based on criteria expressed in terms of classical genetics. There is no explanatory intermediate step from the detailed concepts of molecular genetics about DNA sequences and their molecular environment to the concepts of classical genetics about genes. In fact, Kim’s species/structure-specific concepts of genes (if one applies Kim’s strategy to genetics) that produce yellow blossoms are defined in terms of the concept of genes that produces yellow blossoms and a certain physical or molecular specification. This does not make it intelligible how classical genetics can abstract from ontological (molecular) details and nevertheless focus on certain salient causal relations that define genes such those ones that produce yellow blossoms. Given our dissatisfaction with Kim, the next move for a reductionist is to examine the answers presented by new wave reductionism.112 The general idea is the following one: to construct within the molecular vocabulary a theory that is an image of classical genetics that one seeks to reduce. That is to say, one has to construct concepts of molecular genetics that together image what is described by the functionally defined concepts of classical genetics. More specific, one constructs concepts of the DNA that image as far as possible a certain functionally defined gene concept of classical genetics. The ideal image is a bi-conditional relation between a certain gene concept of classical genetics and an appropriately constructed DNA concept of molecular genetics. For instance, the constructed concept “DNA sequence X1” is an ideal image of the concept “gene that produces yellow blossoms” if and only if it is co-extensional with that concept. However, the possibility of multiple realization excludes such a coextensionality between these concepts. Nonetheless, it is possible to construct concepts of the DNA that are, taken together, co-extensional 112

Cf. Bickle (1998, especially chapters 2 - 4, and 2003) for the so-called new wave reductionism, cf. McCauley (forthcoming) for a detailed consideration of this form of new reductionism, and cf. Endicott (1998) for a criticism that brings out the need for bi-conditional bridge-principles. These issues are generally considered in ‘critique of the multiple realization argument’ (chapter II, p. 133).

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with the gene concept in question. For instance, it is possible to construct the DNA concepts “X1” and “X2” that are together co-extensional with the concept “gene that produces yellow blossoms”. In general, one thus gains several molecular image theories for any gene concept of classical genetics. Taking the argument of multiple realization for most gene types for granted, it is still possible to construct molecular concepts of DNA sequences that, taken together, image the functional characterization of the genes in question. Then, from a scientific point of view, these molecular theories (sets of DNA concepts) are favoured because they are embedded in molecular genetics, which happens to be complete with respect to classical genetics. As a result of this priority, such constructed molecular theories can replace the functional characterizations of genes in terms of classical genetics. This means that classical genetics has only a pragmatic value at a certain state of the scientific art, but it is dispensable. To put it another way, new wave reductionism respects the argument for multiple realization. But it regards multiple realization as an argument in favour of replacing classical genetics by molecular genetics. This move takes into account the relative completeness of molecular genetics and the argument for the token-identity of genes and DNA (cf. ‘relative completeness of molecular genetics’, chapter VI, p. 242, and ‘argument for the tokenidentity of genes and DNA’, chapter VI, p. 247). The consequence thus is that both an anti-reductionist and a reductionist position that renounces biconditional bridge principles in order to establish co-extensionality between concepts of classical and molecular genetics end up in theory replacement. Let us recap and call this ‘multiple realization argument applied to genetics’. There are two main strands of critique of that argument that are in their results quite similar. First, since we can’t construct concepts about DNA sequences in terms of molecular genetics that are such that they are co-extensional with functionally defined gene concepts of classical genetics, the multiple realization argument demonstrates the ultimate spuriousness of classical genetics from the point of view of science. Or, second, each functionally defined gene concept of classical genetics can be replaced by certain constructed concepts of DNA sequences that taken together cover the domain of the gene concept in question. Such constructed molecular concepts are scientifically favoured with respect to the functionally defined gene concepts. Consequently, classical genetics can be eliminated.

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In other words, the anti-reductionist strand takes up the multiple realization argument in order to argue for the irreducibility of classical genetics and thus its scientific autonomy. On the other hand, this irreducibility puts the scientific character of classical genetics into question, even leading us to eliminate classical genetics. Here, new wave reductionism makes the move, taking the argument for multiple realization for granted, of fully replacing classical genetics by claiming that any functional characterization of a gene type can be replaced with constructed molecular theories that are sets of concepts about DNA sequences. The multiple realization argument thus leads to a dilemma: on the one hand, if it is taken to show the irreducibility and thus the autonomy of classical genetics, then genes, insofar as they are described by classical genetics, cannot be causally efficacious, given the relative causal completeness of molecular genetics and the argument for the tokenidentity of genes and DNA. If classical genetics captures causal relations without molecular genetics being able to capture these relations in its terms nor a reduction of the gene concepts of classical genetics to DNA concepts of molecular genetics possible, then it follows that the causal relations that classical genetics considers in its terms are ontologically not identical with something molecular (for a general consideration, regard ‘starting point ontological reductionism’, chapter III, p. 168, ‘implication of anti-reductionism’, chapter III, p. 169, and ‘conclusion’, chapter III, p. 172). On the other hand, if the multiple realization argument is taken to show that one can only construct molecular theories for species/structurespecific (or even more fine-grained sub-sets of) DNA sequences of the gene concepts of classical genetics without there being co-extensional molecular concepts, then classical genetics can be eliminated in favour of the molecular theories. As a way out of this dilemma, I shall propose a reductionist strategy in the following two sections that, while taking the multiple realization argument for granted, makes a case for the indispensable scientific character of classical genetics. Consequently, my proposal is an argument for a conservative epistemological reduction of classical genetics to molecular genetics.

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Any molecular difference between genes implies a functional difference, and can thus be considered in terms of classical genetics. In this section, I shall take our reductionist arguments from the general part of this work and apply them to the relationship of classical and molecular genetics, which will give us a background from which to argue: a), that any molecular difference between gene tokens implies that the gene tokens in question differ in their fitness contribution to the organisms in question (cf. ‘detectability of physical differences’, chapter II, p 138); and b), it is possible to establish functionally defined sub-concepts of the gene concepts in question. These sub-concepts are nomologically coextensional with constructed DNA concepts of molecular genetics (cf. in general ‘implication of detectability’, chapter II, p. 148. Point a) is in the spirit of my considerations of a biological function (cf. ‘functional characterization of the gene’, chapter V, p. 220). At the beginning of the first part of our argument, let me provide a suggestion of my thesis that any molecular differences imply functional differences. Assuming multiple realization within a certain set of gene tokens, say gene tokens that come under the concept “gene that produces yellow blossoms” (“B”), then, on the one hand, there are entities that can be described by one and the same concept of classical genetics – “B”, but, on the other hand, these entities are described by different DNA concepts of molecular genetics. This means, the gene tokens that come under the concept “gene that produces yellow blossoms” (“B”) come under different concepts of molecular genetics, say once again “DNA sequence X1” (“X1”) or “DNA sequence X2” (“X2”). Let us now consider only the gene tokens that come under the molecular concept “DNA sequence X1” (“X1”). This is one sub-set of the gene tokens that come under the concept “gene that produces yellow blossoms”. Among these gene tokens, there are no molecular differences. The other sub-set of the gene tokens is DNA sequences that are molecularly described by “DNA sequence X2” (“X2”). Among these gene tokens, there are no molecular differences either. Thus, the descriptions of both sub-sets only differ from a molecular point of view – classical genetics does not distinguish between these two sub-sets. Having said this, our present concern should be to focus on the following question: is it possible that there will never occur any difference in the description of the two sub-sets in terms of classical genetics as well? Is it possible that the descriptions of both DNA sequences will always be the same in terms of classical genetics? In any case, they are the genes that

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produce yellow blossoms. But, do these genes fulfil exactly the same functional disposition? Our problem is if no differences will ever occur in the context of natural selection, that is, of fitness contributions to the organism in question. Evidence from natural history seems to suggest the possibility that there may occur functional differences of the genes that can be traced back to the molecular differences between the DNA sequences of the gene in question at any point in the history of the genotype. ‘This possibility over the course of time points to the molecularly different genes having potentially different dispositions, and these different dispositions becoming manifest in certain environmental conditions. Let me first consider the different causal dispositions of different DNA sequences. Then, I shall outline environmental conditions under which these different causal dispositions become manifest such that there are different fitness contributions to the organism in question. In order to distinguish molecular differences between the DNA sequences, and functional differences between the gene tokens, I shall use the term ‘causal disposition’ in the context of the DNA sequences and the term ‘functional disposition’ in the context of the genes as regards their fitness contribution. The different DNA sequences or genes producing yellow blossoms are molecularly distinct, so that, for instance, the DNA sequences of type “X1” can differ in their sequences of bases with respect to the DNA sequences of type “X2”. I do not consider molecular differences that do not lead to different reductive explanations of the gene tokens in question (cf. ‘multiple realization argument applied to genetics’, this chapter, p. 262). Any difference in composition that accounts for there being two types of DNA sequences also implies a causal difference. This means, these sequences possess different causal dispositions. The DNA sequences of both types are dispositions to produce cellular effects that are described as the production of yellow blossoms in terms of classical genetics. However, there are differences in the way in which the DNA sequences satisfy the functional characterization of that gene. To put it another way, they differ in their causal disposition by how they produce yellow blossoms. The causal relation from the DNA sequence of type “X1” to the synthesis of the corresponding protein differs compared to the causal relation from the DNA sequence of type “X2” to the synthesis of the protein of the same type. Remember that I am not arguing against the possibility of multiple realization. Furthermore, I shall not consider environmental conditions under which the genes that produce yellow blossoms that are of the molecular type “X1” lead to the production of yellow blossoms, while those of the molecular type “X2” do not. Such

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cases are of course possible, but only show that molecular genetics is more complete when it comes to specifying standard environmental conditions. Such cases do not show whether and how classical genetics can be reduced to molecular genetics. Relative completeness per se is not sufficient for a reductionist approach, even though it is one of the two main premises. Let me consider some of the different causal dispositions of the DNA in more detail. The molecular difference between the DNA sequences of type “X1” and the DNA sequences of type “X2” implies a different stability of the DNA double helix, at least at the loci where the differences are. The stability of the DNA double helix depends on the complementarity of its DNA bases. Thereby, the binding of the complementary bases guanine and cytosine (G – C) is stronger compared to the binding of the complementary bases adenine and thymine (A – T). Guanine and cytosine are bound with 3 hydrogen bonds compared to two hydrogen bonds that connect adenine and thymine. Furthermore, adjacent G – C base pairs interact more strongly with one another. Therefore, the DNA sequences differ in their resistance against denaturation (separation of the DNA double helix) due to heat, chemicals, ultraviolet light, etc.113 In this context, let me consider the mechanism of transcription. In order to transcribe the DNA sequence in question into a corresponding mRNA that later on codes for a protein, the DNA double helix has to be separated. Thereby, the RNA polymerase that separates the DNA double helix and transcribes the DNA sequence in question separates double 113

Compare for instance Marmur & Grossman (1961) as one of the early works in this field that illustrates parts of the then-prevailing state of the art about DNA damages by means of heat, chemicals, or ultraviolet light. Compare furthermore any standard textbook about the structure of DNA and its so-called melting temperature such as Stryer (1999, pp. 84-87), or about the DNA mutations in the context of ultra-violet light or chemicals such as Stryer (1999, pp. 809-811). Another, quite more complex issue is the following: Salmonella is a bacterium that swims by rotating protein filaments. The Salmonella bacterium possesses the property that it has two different genes for different such protein filaments, but the organism produces only one of them at a given time. The switching between the production of these proteins occurs on average once in a thousand cell divisions. Without going into too many details (compare for instance Stryer, 1999, pp. 969-970), this spontaneous change is important for the fitness of the bacterium in question in order to evade the immune response of its host. The point I want to focus on in this context is the following: the switching between these two types of genes is based on inversions of DNA segments. Thus, this examined case illustrates that minimal structural differences have an impact for the fitness of the organism in question. To put it another way, if the average of such important gene switching is changed (because of, for instance, stronger bindings of G – C base pairs), the fitness contribution of the gene in question changes as well.

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helices of different stability. Let me note that the mechanism of transcription is generally repeated several hundred or thousand times (or even more) in order to produce cellular effects, and there are a lot of blossoms cells of flowers (depending on the type of flower, and the number and size of the blossoms of course). To put it another way, each of my considerations on differences of causal dispositions per se may appear minimal, but in the sum it becomes clear that the molecular differences between the DNA sequences of type “X1” and of type “X2” have an impact on the function of the cell and thus on the organism in question. Let me continue and focus on two other issues of the transcription process. First, the DNA sequence of type “X1” codes for a different mRNA sequence than the DNA sequence of type “X2”. If there is a difference in the DNA bases between the DNA sequences “X1” and “X2”, there is a difference in the corresponding mRNA bases as well. Thus, the transcription of the DNA sequence X1 needs different amounts of each type of ribonucleoside triphosphate (UTP, ATP, GTP, and CTP), or needs them in another order compared to the transcription of the DNA sequence. Second, there are proteins that can bind at the DNA such that the transcription will be interrupted. In the case of the difference between DNA sequences of type “X1” and of type “X2”, there are different dispositions to bind such interrupting DNA binding proteins because the binding depends on the sequence of DNA bases.114 Let’s now look at the translation and synthesis of proteins. Subsequent to the synthesis of proteins, any molecular difference is even more obvious than in the cases so far considered, because the function of proteins depends essentially on their conformation. By “conformation”, one understands the three-dimensional structure of the protein that is essentially based on the sequence of amino acids. As mentioned above, the different DNA sequences coming under the concepts “X1” and “X2” code for different mRNA sequences. Let me call them “mRNA1” and “mRNA2”. In any case, a triplet of mRNA bases codes for an amino acid that forms the protein. Proteins are essentially sequences of amino acids that are transformed into a specific three-dimensional structure by means of specific enzymes. This translation of the triplets into a sequence of amino acids is mediated by so-called tRNAs in the ribosome. For each triplet – also called “codon” – there is a specific tRNA that carries its corresponding amino acid. To sum up, if there is a difference in the sequence of the mRNA as there is in the case of “mRNA1” and “mRNA2”, 114

In this context, compare for instance Croxton et al. (2002) who outline in a specific case the relationship between DNA binding proteins and specific DNA sequences.

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there is a difference in the involved tRNAs. To put it simply, the translation of mRNA1 needs other tRNAs than the translation of mRNA2. Let us summarize the bearing these molecular considerations on our argument so far. The multiple realization argument claims that there are molecular differences in the composition of the DNA that do not have any functional impact as considered in classical genetics. In particular, the molecular differences vanish at a certain stage of the molecular processes from the DNA to the protein. For instance, both the different mRNA1 and mRNA2 code for the same protein. However, there are in fact different causal relations of the synthesis of the protein in question, and the DNA, and thus RNA, differences have, up to this point, at least different impacts at the cellular level as considered in terms of molecular genetics. Different resources are needed, the DNA sequences differ in their stability, and the mechanism of transcription and translation can differ in time. To conclude, the molecular differences between DNA sequences of type “X1” and of type “X2” do not vanish. Against this background, let me now consider how such molecular differences lead to functional differences as considered in the context of fitness in classical genetics. This will show that the mentioned differences between DNA sequences of type “X1” and of type “X2” do not vanish at the level of classical genetics either. There are environmental conditions possible in which the different causal dispositions of the DNA sequences of type “X1” and of type “X2” become manifest at the functional level as considered in terms of classical genetics. I shall give an illustrative example where the molecular differences of the DNA sequences of type “X1” and of type “X2” imply a different fitness contribution for the organism in question. For the molecularly different DNA sequences (being either of type “X1” or of type “X2”) there is an environment possible in which that molecular difference implies selective advantages, or disadvantages, and thus a functional difference.115 To put it simply, genes that come under the functionally defined concept “gene that produces yellow blossoms” and under the molecular concept “DNA sequence X1” differ functionally compared to genes that produce yellow blossoms but that come under the molecular concept “DNA sequence X2”. Even more precise, these functional 115

Cf. Papineau (1993, p. 47) who correctly claims that “variable causes can have uniform effects in virtue of mechanisms which select items because they have that effect”. Just to bear in mind, I do not argue against this claim. After all, I do not argue against the multiple realization argument. But the crucial point is that there are always environments possible in which molecular differences lead to different fitness contributions that are linked to what Papineau calls “uniform” effects.

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differences between the gene tokens are linked with their characteristic effect to produce yellow blossoms, and these functional differences can be traced back to the molecular differences between the DNA sequences of type “X1” and of type “X2”. As already mentioned, there are differences in the way in which the DNA sequences satisfy the functional characterization of the genes in question. The causal relation from the DNA sequence of type “X1” to the synthesis of the corresponding protein differs from that of type “X2”, synthesizing the same type of protein. At least, they differ in their causal dispositions how to produce the proteins (that lead to the observable effect of yellow blossoms). This difference can be detected as a functional difference between the gene tokens in question in environments that satisfy the following general condition: environments in which the mentioned molecular differences in the production of the yellow blossoms are crucial for the fitness of the flower in question.116 Thus, what I have in mind are environmental conditions in which, for instance, the different stability of the DNA sequences implies a different fitness contribution in the context of the production of the yellow blossoms. This means, for example, that the DNA sequences of both types (“X1” and “X2”) contribute a certain fitness value to the organism in question. But, in the case where the genes are DNA sequences of type “X1”, there is an additional selective advantage because of the stability of this DNA sequence, thus resistance against chemicals or ultraviolet light. My thesis can be specified as follows: For any causal difference accounting for there being two types of DNA sequences that are genes of one type, it is possible to conceive an environment in which this causal difference is salient for selection. Bearing this thesis in mind, let me outline one of those hypothetical environmental conditions in which genes coming under the molecular DNA concept “X1” possess a selective advantage for the organism in 116

Cf. Rosenberg (1994, p. 32) who argues that “no two physically diverse structures have exactly the same set of functions” and “… there is always some possible environment and some length of time in which the smallest structural difference or its immediate effect can bear a selective advantage or disadvantage.” Note that every selective advantage or disadvantage can be taken into account in terms of classical genetics. Furthermore, cf. Waters (1994, pp. 181-82) who points out the relational character of molecular genetics and compares it to classical genetics. Against this background, my proposed strategy becomes more comprehensible, because, also according to Waters, a change on the molecular level entails a functional difference that can be taken into account in the functional vocabulary.

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question compared to genes coming under “X2”. Imagine an environment with a high radiation of ultraviolet light that increases the probability of DNA damages. Under such environmental conditions, the difference in composition of the DNA sequences of the genes may lead to a functional difference. By chance, the genes that produce yellow blossoms that come under the molecular concept “DNA sequence X1” may possess a relatively high resistance to ultraviolet light whereas genes that come under the molecular concept “DNA sequence X2” may possess a relatively low resistance to ultraviolet light. This means, in environments with high radiation of ultraviolet light, the way in which genes cause yellow blossoms depends on whether the genes are resistant to ultra-violet light, or whether they are not resistant to ultra-violet light. There is a difference in time and / or the need of resources in order to cause the yellow blossoms. The flowers with genes that produce yellow blossoms that come under the molecular concept “DNA sequence X1” cause yellow blossoms in a way that is advantageous for selection because there is no, or relatively less, need of cellular resources in order to repair genetic damages caused by the ultra-violet light.117 Compared to this, flowers with genes that produce yellow blossoms that come under the molecular concept “DNA sequence X2” may need relatively more time and cellular resources in order to produce the yellow blossoms. This is disadvantageous for selection because the flowers in question need additional resources in order to produce the same effect that the other flowers (with genes of type “X1”) do not need. These genes have to be repaired several times, and in order to repair the genes from the damages caused by the ultra-violet light, the flower needs resources that ‘lack’ at other locations of the flower. This is a functional difference because this difference is salient for selection. This means, there is a different fitness contribution. The important issue at this point is that one can conceive an environment in which the molecular difference between the DNA sequences of type “X1” and of type “X2” leads to a functional difference that is linked to the gene as a functional property. Let me note that environmental conditions with high radiation of ultraviolet light are common in genetic researches – even if most of such laboratory conditions aim to analyse repairing mechanisms of different organisms that result from damages caused by ultraviolet light. Thus, one may not often observe functional differences in environmental conditions that are common in our 117

Compare for instance Christmann et al. (2003) who outline different repair mechanism of the DNA in humans.

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world just because the occurrence of such functional differences based on molecular differences has a small probability. But it is possible to conceive environmental conditions in which the probabilities become increased and a statistically relevant amount of model organisms are observed. Bearing this fact in mind, consider the argument for functional differences in general: since any difference in composition between two types of molecular configurations means that the components of the one molecular configuration stand in other causal relations than the components of the other molecular configurations, one can always conceive an environment in which this difference leads to a functional difference that is detectable in terms of classical genetics in the context of fitness contributions. My claim therefore is that any molecular differences between DNA sequences which lead to two different types of realizers are always subject, without exception, to conditions which may lead to some functional difference. In fact, many functional implications of molecular differences are already well known.118 Moreover, since we focus on molecular differences between DNA sequences that are genes for yellow blossoms, this functional difference is linked to the functional disposition that defines the genes that produce yellow blossoms. Let me sum up the steps of the argument:

118

Compare the enormous amount of literature on experience of effects of ultraviolet light on molecular structures, organelles, cells, etc. Compare furthermore any standard literature such as Campbell (2005, pp. 329-330) or Stryer (2005, pp. 809-811) in the context of ultraviolet light as a so-called mutagen.

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A certain DNA concept defined in terms of composition implies that the components of the referents of this concept stand in certain causal relations to each other and possess therefore a certain disposition to stand in particular causal relations with the environment. For any difference in composition accounting for two different types of DNA sequences that are genes of the same type, there is a corresponding difference in dispositions, and for any difference in dispositions, an environmental change may occur such that this difference becomes manifest and will lead to a functional difference that is detectable in terms of classical genetics – because it is salient for selection. Since we focus on molecular differences that account for there being two types of DNA sequences that are genes of the same type, there is an environment possible in which the molecular differences between the types of DNA sequences lead to a functional difference of the relevant genes. Let me add that this argument does not necessarily require that classical genetics is able to distinguish the environmental/molecular conditions in its own terms. It is sufficient that some molecular biologist conceives environmental conditions and some biologist using the functionally defined gene concepts and explanations of classical genetics detects a functional difference. Thereby, ‘detect’ means to express a functional difference in terms of classical genetics in the context of fitness contributions, and thus, in purely functional terms. I am simply arguing for the possibility of detecting a functional difference in terms of fitness advantages or disadvantages here. . For any molecular difference that accounts for there being two types of DNA sequences that are genes of the same type, there is an environment conceivable in which the molecular difference in question leads to a functional difference that is detectable in terms of classical genetics because it is salient for selection. It is irrelevant to our case whether or not ‘ultra-violet light’ is a concept that occurs in classical genetics or only in molecular genetics. Moreover, suppose that the biologist in question is not able to describe the environmental conditions in terms of classical genetics. Nonetheless, she can detect functional differences between the gene tokens in question because the gene tokens are advantageous or disadvantageous for selection. Imagine that the biologist observes that 50% of the flowers in question produce yellow blossoms earlier than the other 50%. Under the assumption that the high radiation of ultraviolet light holds, she could start with breeding experiments in the style of Mendel just to substantiate in her breeding line

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that variations in the production of yellow blossoms will be inherited because it occurs according to a statistical ratio. Such cases may be taken to suggest a problem. Let us suppose that the biologist in question detects functional differences between gene tokens that produce yellow blossoms that come under the one concept “gene that produces yellow blossoms”. In order to avoid the eliminativist consequences of the new wave reductionism, the biologist should construct concepts that take into account these functional differences. The one concept “gene that produces yellow blossoms” can, after all, not explain the functional differences. If we take classical genetics as irreducible, it doesn’t seem possible that classical genetics can abstract from molecular details while always continuing to be indispensable for scientific explanation. Up to now, it seems that such functional differences could be only explained in terms of the mentioned species/structurespecific constructed molecular theories – theories that are intended to replace classical genetics. The new wave, then, attacks the explanatory indispensability of classical genetics that we want to preserve. Against this background, let me consider possible objections to my argument to detect molecular differences between different types of DNA sequences in terms of classical genetics. First of all, someone may maintain that classical genetics is sometimes not that precise, its epistemological classifications are sometimes vague, and maybe, that is why its law-like functional characterizations and (if any) general laws are not strict but so-called ceteris-paribus laws. The functional characterizations are, after all, openended lists that focus on salient causal relations. Furthermore, who should be interested in specifying the fitness contribution of genes that produce yellow blossoms. So much the worse for any reductionist that starts from the incompleteness of classical genetics compared to molecular genetics, and ends up there. This kind of objection doesn’t touch my argument. The general point is that in principle, any causal molecular difference between types of DNA sequences that are genes coming under one concept of classical genetics leads to a functional difference that is detectable and thus expressible in terms of classical genetics. This is a philosophical analysis of the systematic relationship between classical and molecular genetics. In addition to this, we aren’t claiming that classical genetics should be able to explain any molecular difference, nor to determine environmental conditions to the degree of precision that molecular genetics can. To the contrary, it is molecular genetics that should explain what is inexplicable in terms of classical genetics (cf. ‘historical framework’, chapter IV, and

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p.183, and ‘explanatory limits of classical genetics’, chapter V, p. 228). However, to my mind, classical genetics is in fact indispensable for our understanding of heredity. My strategy therefore aims to justify this specific claim of the anti-reductionist strand – as the only claim of this strand of course. As has already been said, I accept the multiple realization argument and am making no argument that classical genetics should be like molecular genetics. To the contrary, my aim is to provide a systematic link between both genetic theories that is based on the co-extensionality between concepts. It seems that this is the only strategy available to avoid the elimination of classical genetics. Without such a co-extensionality between concepts, classical genetics is liable to lose its scientific status. Furthermore, one may use my argument to conceive contrary cases. For instance, one may either conceive molecular conditions in which the molecular differences between the DNA types “X1” and “X2” do not lead to functional differences, or molecular differences that appear only for a certain length of time. On the one hand, there certainly are environmental conditions in which many molecular differences do not lead to functional differences. One may only think of common environments in our world in which differences in resistance to ultraviolet light imply no functional differences. Thus, at least within a certain length of time, no functional difference may occur. In regard to this, I would like to note the following: the possibility of functional differences still remains. There are different dispositions by which it is possible to distinguish the gene tokens in question. Even under normal environmental conditions, the genes that produce yellow blossoms that come under the molecular concept “X1” possess another functional disposition than the genes that produce yellow blossoms that come under the other DNA concept “X2”. And, functional characterizations of genes are concepts about dispositions to contribute a certain fitness value to the organism in question. On the other hand, there might be molecular differences conceivable that disappear after a certain length of time. Genes that produce yellow blossoms may differ with regard to some molecular property, but these differences may vanish after a hardly measurable short time. Therefore, it might not be reasonable to postulate a different functional disposition. How to deal, then, with such molecular differences? In regard to this, let me reconsider the concept of a realizer (compare also my general considerations in ‘Kim’s model of reduction’, chapter II, p. 99). These molecular differences are unlikely to bear on the synchronic production of yellow blossoms. If molecular systems are added to or disappear from a DNA sequence that is a gene that produces yellow blossoms without any

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impact on the production of the yellow blossoms, these molecular differences do not play any role in being the gene token in question. For instance, let us assume that the molecular difference between two individual DNA sequences that are genes that produce yellow blossoms consists in one single electron, additional or different bases at the introns (parts of the mRNA that do not code for the sequence of amino acids), or something like this.119 If these differences are redundant for the production of yellow blossoms, the gene tokens come under one single DNA concept. They are redundant in order to satisfy the functional characterization of the gene token in question. Let me reconsider this point in terms of explanations. In order to provide an explanation, any abstraction from molecular details should be admissible as long as the molecular explanation remains coherent. To put it simply, the genes that produce yellow blossoms are multiply realized by different DNA sequences. But, if the molecular differences are ‘redundant’ to the explanation of why a given DNA sequence codes for a certain protein that leads to the observed phenotypic effect of yellow blossoms. ‘Relevant’ molecular differences between types of DNA sequences are molecular differences that make it impossible to explain coherently in molecular terms the causal disposition that defines the gene in question. For instance, a coherent molecular explanation of the synthesis of the protein (causing yellow blossoms) contains the DNA sequence that codes for mRNA sequences that code for the sequence of amino acids the protein in question is composed of. Contrary to this, ‘redundant’ molecular differences can be theoretically ignored in order to provide a homogeneous molecular explanation of the functional disposition that defines the gene that produces yellow blossoms. For instance, in order to explain the genes that produce yellow blossoms in terms of molecular genetics, additional molecular systems possessing or lacking one additional electron, for instance, or possessing or lacking of additional bases in the intron sequence, are commonly not considered. These molecular differences are ‘redundant’ for the reductive explanation of the gene in question. To summarize my counterargument: either (dispositional talk of) functional differences is reasonable, or the molecular differences are ‘redundant’.

119

Let me note that such molecular difference sometimes play a crucial role, especially in the context of transcription. Compare for instance Morita et al. (2003) who outline the effects of zinc-ions that are bound at the DNA and therefore repress the transcription of a certain gene. In any case, such considerations would support my argument – but would make it much more complicated to illustrate.

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Let me recap this first part of the section. Any relevant molecular difference between types of DNA sequences that are genes of the same type can in principle be detected by classical genetics. There is no molecularly ‘relevant’ difference between the DNA sequences “X1” and “X2” (that are in any case genes that produce yellow blossoms) that does not lead to functional differences between the gene tokens in question. There are dispositions of fitness contributions that correspond to each type of DNA. This means that “X1” genes producing yellow blossoms possess different dispositions that can be picked up in the context of natural selection. Thus, there are functional differences that that can be traced back to molecular differences. Having dealt with this issue, let’s see what follows from this detectability. The second part of this section is about the ability of classical genetics to construct sub-concepts of the gene concept in question that are nomologically co-extensional with DNA concepts. My thesis is that given functional differences between gene tokens can come under one gene concept, it is possible to construct sub-concepts of this concept such that these sub-concepts describe genes that are molecularly identical. For instance, it is possible to construct two sub-concepts of “gene that produces yellow blossoms” each of which is co-extensional with “DNA sequence X1”, or “DNA sequence X2”. This construction of sub-concepts is based on the first part of this section, but there is an underlying argument we need to examine. First, let us reconsider the ability of classical genetics to detect molecular differences between genes as examined in the first part of this section. Any molecular difference that amounts to there being different types of DNA sequences (that are genes) leads to functional differences. This means, the molecular differences between the DNA types are detectable in the functional vocabulary of classical genetics – and not only in terms of molecular genetics. To take into account fitness contributions, functions that are salient for selection, etc., belongs to the conceptual set of classical genetics. A functional characterization of a certain gene is implicitly a functional characterization in the context of natural selection. This is in the spirit of Dobzhansky’s dictum that “nothing in biology makes sense except in the light of evolution”.120 To put it another way, a functional characterization of a certain type of gene (as outlined in chapter V) is always a functional characterization in the context of fitness contributions, of natural selection, thus, in the light of evolution. 120

Dobzhansky (1973).

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Second, how do we construct functionally defined sub-concepts? More detailed concepts of the genes that produce yellow blossoms, for instance, can be based on the detectability of functional differences between the DNA sequences “X1” and “X2”. This means, it is possible to construct in terms of classical genetics sub-concepts of the concept “genes that produce yellow blossoms”. These sub-concepts take into account any possible functional difference consequent upon molecular differences arising between the DNA sequences of type “X1” and “X2”. The argument in general can be summed up as follows: we take the multiple realization argument in the case of the gene in question for granted. This means, the property tokens that come under the concept “gene that produce yellow blossoms” differ in molecular respects. Given certain environmental conditions, these molecular differences that are different causal dispositions are different functional dispositions in the context of fitness contributions. Thus, they are detectable in terms of classical genetics as well. ‘Detectable’ thereby means ‘differences in the fitness contributions’. It is, then, possible to construct more detailed functionally defined subconcepts. These sub-concepts are formulated in terms of functional dispositions and take into account any possible difference in the fitness contribution. This is, at least, a principled possibility. I shall consider these principled possibilities later in my ‘final remarks’ (cf. p. 297). Third, how do we explain the construction of sub-concepts of the gene concept? They are co-extensional with the molecular DNA concepts because each relevant molecular difference leads to a functional difference that can be considered in terms of classical genetics in the context of fitness contributions. Contrary to this, functionally defined gene concepts admitting of multiple realization do not take into account these possible functional differences. This is why I shall call the concepts such as “gene that produces yellow blossoms” abstract gene concepts. Considering a certain abstract gene concept, it is possible to construct sub-concepts each of which takes into account a specific functional detail that is tied to the function in question. This means, each sub-concept of “gene that produces yellow blossoms” takes into its scope specific dispositions of fitness contributions that differ from the other sub-concepts. For instance, “gene that produces yellow blossoms in a way that is advantageous in the context of selection”. This is of course a very first and vague specification of the subconcept in question just because the following objection can be raised: suppose we can, as I have claimed, construct two sub-concepts of the concept “gene that produces yellow blossoms”. Let me call this abstract

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concept “B” in this context of consideration, and its two sub-concepts “B1” and “B2”. As I claim, “B1” is co-extensional with the molecular DNA concept “X1”, and “B2” is co-extensional with the molecular DNA concept “X2”. The argument for this co-extensionality is that the way in which the gene in question produces yellow blossoms depends on its molecular DNA structure. Thus, there are two different fitness values that distinguish between “B1” and “B2”. In a simplified manner, one may say, “B” is specified by the fitness value n, “B1” by (n - x), and “B2” by (n - y). Now, it may be objected that we can conceive particular environmental conditions in which the DNA sequences of type “X1” (and not “X2”) contribute a fitness value of (n - y ). Thus, one takes my argument to conceive environmental conditions such that genes coming under the subconcept “B1” contribute exactly the fitness value (n - y) that defines the gene sub-concept “B2”. As a result of this, “B2” specified by (n - y) cannot be co-extensional with “X2” just because the DNA sequences of type “X1” can contribute the very same fitness value to the organism in question (given certain environmental conditions). To put this another way, the constructed sub-concept “gene that produces yellow blossoms in a way that is advantageous in the context of selection” that is specified by a certain fitness value is not co-extensional with one molecular DNA concept. Classical genetics can be as precise here as molecular genetics. The argument is that any molecular difference between two DNA sequences implies a functional difference of the corresponding genes that can be expressed in functional terms of classical genetics. However, it is not possible to construct on this basis nomologically co-extensional subconcepts because each specific fitness value as such (as the defining part of the sub-concepts in question) can be multiply realized. Any specific fitness value that defines a sub-concept of genes can be achieved by genes coming under different DNA concepts (given certain environmental conditions). Let me outline my counterargument. To attribute a specific fitness value to a certain gene concept, or to its sub-concepts, is a simplification. The terms “fitness value” or the paraphrase “in a way that is advantageous in the context of selection” are placeholders for more detailed specifications. Let us bear in mind that the genes coming under the concept “B” do not contribute any fitness value to their organisms in winter, or when there are no insects that are attracted because of the yellow colour of the blossoms. Thus, in these conditions, the contributed fitness value is 0. Assume that under the best conditions in springtime and

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summer, the fitness contribution of the gene in question reaches the value n. Under extreme environmental conditions in the summer or in springtime, when there is extreme heat or high radiation of ultraviolet light, this fitness value n decreases because of gene damages, etc. In any case, a specific fitness value does not specify the contribution of the gene in question in general, but only for a particular environment at a particular time or period of time. This suggests that a specification of a fitness contribution that figures in a certain gene concept or a sub-concept cannot be a specific or concrete fitness value. It is rather something like a statistical distribution of possible fitness contributions depending on the environmental conditions. In this context, a certain gene has the functional disposition to contribute a fitness value from 0 to n. At springtime, if many insects are attracted because of the yellow colour of the blossoms, it is something around n. If there are only a few insects that are attracted, the fitness contribution is between 0 and n, and in winter it is 0. Let us now imagine a bet between an anti-reductionist biologist who nevertheless knows a lot about molecular genetics and a classical biologist who has no idea of molecules and ultra-violet light, but nonetheless has reductionist inclinations. The molecular biologist knows two types of DNA sequences (“X1” and “X2”) that are genes coming under the same concept in classical genetics (“B”). The classical reductionist biologist bets that he can detect functional differences between the molecularly different genes if the molecular biologist changes the environmental conditions. To put it another way, he bets on the possibility of constructing sub-concepts of the gene that are co-extensional with the molecular DNA concepts “X1” and “X2”. The starting point for this bet is that the classical biologist does not know which flowers possess genes of the molecular type “X1” and which possess genes of type “X2”. All he can observe is a statistical relevant amount of flowers, and he knows that 50% possess genes that produce yellow blossoms coming under the molecular concept “X1”, and 50% possess genes coming under the molecular concept “X2”. Now imagine that the environmental conditions are normal in the first year. No extreme heat, no high radiation of ultraviolet light occurs. Nonetheless, the classical biologist starts to make a list for any flower. Such a list contains the occurrence of the first yellow blossom cell at any blossom of the flower in question. In this context, the list records the amount, the percentage, and the time of yellow blossoms cells of the blossoms of the flower in question. However, since the molecular biologist does not change the environmental conditions in this first year of record,

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no statistically relevant differences occur. This means, it is not possible to distinguish such small DNA differences under normal environmental conditions. In this time frame, then, it proves to be impossible to construct functionally defined sub-concepts of the gene concept in question. This changes in the second year of record. There, the molecular biologist changes the environmental conditions such that there is a high radiation of ultraviolet light. This leads to gene damages that appear more often in genes of the molecular type “X2” compared to the genes of the molecular type “X1”. As a result of this, the corresponding cells need more resources to repair these damages, and need more time to produce the yellow colour of the cell in question. At the end of the record, the classical biologist states the following results: every flower produced at some day yellow blossoms. But in 50% of the flowers, the production of yellow blossoms differs from the other 50% of the flowers. In the latter sample a statistically relevant amount of blossoms cells of the blossoms needed more time to become yellow. In this context, the classical biologist transforms his lists into mathematical functions that describe the occurrence of yellow blossoms cells of the blossoms. He ends up with two mathematical functions, say “mfA” and “mfB”. These are, so he claims, the specifications of fitness contributions he searched in order to detect functional differences between the different molecular DNA sequences “X1” and “X2”. After all, the occurrence of the yellow colour is relevant in the context of selection since the yellow colour attracts insects. The molecular biologist, astonished about the results his colleague obtained, raises the following objection: the sub-concepts as defined by the mathematical functions “mfA” and “mfB” are not co-extensional with the molecular DNA concepts “X1” and “X2”. His argument is based on his ability to change the environmental conditions in the following way: extreme heat appears and/or chemicals occur in the environment having the consequence that the genes of the DNA sequence “X2” will produce yellow blossoms cells such that now they can be described by the mathematical function “mfA”. Therefore, the mathematical function “mfA” cannot be bi-conditionally correlated with the molecular DNA sequences “X1”. The molecular DNA sequences “X2” can be described as well by the mathematical function “mfA” (given other environmental conditions than the ones in the second year). Bearing this objection in mind, the classical biologist continues his records. After one more year of record (the third year), the classical biologist realizes that it was actually possible that the other genes can also be specified by the mathematical function “mfA” – at least in this

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environment (but, of course, he has no idea about environmental conditions). However, he takes also notice of the occurrence of yellow blossom cells of the other genes. There, he transforms his data once again into a mathematical function, say “mfC”. This means, the molecular DNA sequences “X1” can be described by the mathematical function “mfC”. Against this background, the classical biologist claims that it is nonetheless possible to distinguish the molecular DNA sequences functionally. The strategy proceeds as follows: first of all, the classical biologist takes up the functional distinction of the second year by the two mathematical functions “mfA” and “mfB”. Of course, it is possible that the “mfA” or “mfB” can be realized by molecularly different gene tokens given certain environmental conditions (such as in the third year). But it is possible to combine the records of both years (the second and the third year) in order to describe the average fitness contributions by means of only two different mathematical functions. Thus, the task now is to construct two modified mathematical functions that take into account more data; these are hence more precise. 50% of the genes can now be specified by the mathematical function “mf1” (“mfA” + “mfC”), and the other genes can now be specified by “mf2” (“mfB” + “mfA”). At least, such two distinct mathematical functions will result after a certain length of time of record. If there do not occur significant differences in the first years of record, there will surely occur differences at some later time given enough different environmental conditions. At the very beginning, the mathematical functions may be not that precise and seem to be still multiply realizable, but after a certain length of time, they become more and more precise and the detection of molecular differences in terms of classical genetics becomes possible. This is, to sum up, the argument for the possibility to detect molecular differences in functional terms. In this context, let us reply to the objection from the new wave reductionist. Of course, it is possible that in a specific environment, the fitness contributions of the different DNA sequences “X1” and “X2” can be the same for the organisms in question. But if one observes the molecularly different gene tokens over a certain length of time, one will recognize functional characteristics that distinguish the gene tokens in question according to their molecular composition. To put it another way, one can rewrite the probabilities of fitness contributions in terms of a mathematical function each of which characterizes the fitness contribution of the genes of one molecular type. Of course, there may be intersections at certain specific points where the fitness contribution of the genes of one

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molecular type is like the one of other molecular type. But in context of the data over a certain length of time, that is, in the context of the mathematical functions that describe the dispositions of fitness contributions, it is possible to distinguish the gene tokens. To put it another way, genes of the molecular type “X1” come under the functionally defined sub-concept “B1” that is defined by a specific mathematical function of possible fitness contributions. One may say, the genes as described by the mathematical function “mf1” are defined by an always quick production of yellow blossoms, while the genes as described by “mf2” produce the yellow blossoms in a statistically relevant way more slowly. As our classical biologist shows, one can count the cells of the blossoms that become yellow and compare the observed colour changes in the context of time with respect to other flowers and their production of yellow blossoms. Depending on different environmental conditions, one will recognize differences in the production, and it is possible to transform the statistical analysis into mathematical functions that specify subconcepts. These sub-concepts are co-extensional with the mentioned molecular DNA concepts. Thus, let us bear in mind that expressions such as ‘advantageous in the context of selection’ are placeholders for mathematical functions that describe the probabilities of fitness contributions of the gene tokens in question. In any case, under the assumption that any relevant molecular difference is detectable under certain environmental conditions, the functionally defined sub-concepts of the gene concept in question are necessarily co-extensional with the DNA concepts in question. This is the consequence of the work of classical biologists that make the mathematical functions describing the possible fitness contributions more and more precise. It is worth restating the point once more, to drive home our argument: classical genetics can consider any relevant molecular difference in its own terms in the context of fitness contributions as described by a mathematical function, and hence, construct appropriate functionally defined sub-concepts co-extensional with the DNA concepts in question. These functionally defined sub-concepts describe genes that are molecularly identical:

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Implication of the detectability of any relevant molecular difference: Construction of functionally defined sub-concepts (specified by mathematical functions that describe the probabilities of fitness contributions) of the gene concept in question that are c o extensional with molecular DNA concepts: Classical genetics “gene that produces yellow blossoms”  “gene that produces yellow blossoms + selective advantage” 



(construction of functionally defined subconcepts)

“gene that produces yellow blossoms + selective disadvantage” 

(co-extensional with)

“X1” “X2” 



(embedded in / constructed out of)

Molecular genetics Summarizing the arguments that are instantiated in the ‘construction of sub-concepts’, we have shown that classical genetics is able to construct functionally defined sub-concepts of any gene concept that are coextensional with molecular DNA concepts. Given functional differences because of molecular differences, as argued for in the first part of this section, it is possible to construct sub-concepts of functionally defined gene concepts such that each of these sub-concepts describes all and only those entities that are uniformly described by a molecular DNA concept. For instance, it is possible to construct sub-concepts of “gene that produces yellow blossoms” each of which is co-extensional with a molecular gene concept such as “DNA sequence X1” or “DNA sequence X2”. Let me note that these detailed functionally defined sub-concepts are law-like generalizations. In this context, I shall consider the famous Mendelian laws at the end of this chapter (cf. ‘final remarks’, this chapter, p. 297).

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iv.

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The main aim of this section is to provide a reductionist approach to classical genetics that is not eliminativist. In the first part of this section, I shall consider the relationship between abstract gene concepts and their more detailed sub-concepts. My thesis is that an abstract gene concept can be deduced from each of its sub-concepts. This section applies considerations of the general part of this work to genetics (cf. ‘relationship between concept and sub-concepts’, chapter II, p. 152). In the second part of this section, I shall outline how we can construct a conservative reduction of classical genetics to molecular genetics by means of the constructed sub-concepts of the gene. This section takes into account several issues of the general part as well (cf. ‘epistemological reductionism by means of sub-concepts’, chapter II, p. 157). First, let’s examine the general relationship between abstract concepts and detailed concepts. An abstract functionally defined concept is defined by specific causal relations or functional dispositions. For instance, genes are defined by their functional disposition to produce yellow blossoms. Functionally defined concepts that are more detailed (relatively to the abstract concepts) take into their scope both that functional disposition and certain functional specifications. In particular, the more detailed functional characterizations take into account further specifications of the functional disposition in question. For instance, the concept “gene that produces yellow blossoms in a way that is advantageous in the context of selection” is a specification of the functional disposition to produce yellow blossoms. Thus, the functionally defined concept “gene that produces yellow blossoms” is an abstract concept because it abstracts from possible functional differences that are based on the molecular differences between the DNA sequences “X1” and “X2”. These functional differences are only considered by more detailed functionally defined concepts that take these functional differences into account. These are the sub-concepts such as “gene that produce yellow blossoms in a way that is advantageous in the context of selection” that are about gene tokens that can be uniformly described in terms of molecular genetics. Second, let me consider the possibility to deduce an abstract gene concept from each of its more detailed sub-concepts. Provided that the abstract gene concept such as “gene that produces yellow blossoms” differs from its more detailed sub-concepts only in the way in which the

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more detailed sub-concepts contain additional functional specifications, the abstract gene concept can be deduced from each of its more detailed sub-concepts. The argument can be stated as follows: a detailed subconcept can be taken as a relatively long conjunction of single concepts. Thus, one part of the conjunction is exactly what is stated in the abstract gene concept, as, for instance, the concept about the disposition to produce yellow blossoms. The other part of the conjunction is the functional specifications in the context of fitness contributions, advantages or disadvantages in selection, etc. For instance, these are dispositions to produce yellow blossoms in a way that is advantageous for selection. This means, the abstract gene concept is about a certain set of entities; and these entities can be described as well by means of more detailed sub-concepts that take into account possible differences in fitness contributions. Each gene token has the disposition to contribute certain fitness values to its organism (as described by a mathematical function). This quantification also appears in the one part of the conjunction of concepts in the functionally defined sub-concepts. It characterizes in general the function to produce yellow blossoms. The other part is about the way in which the former disposition (to produce yellow blossoms) becomes manifest is salient for selection, for instance, the advantages for selection if the production of yellow blossoms does not need that much resources. Let us bear in mind that the term “resources” may not be a term of classical genetics since the differences are about molecules that are needed. However, as already mentioned in the previous section, it is sufficient that fitness differences can be detected. These differences can be described in form of a mathematical function that is sufficient to reach coextensionality between the mentioned sub-concepts and the molecular DNA concepts in question. The explanation of such fitness difference (as described in the mathematical functions about probabilities of fitness contributions) may then be well a task of molecular genetics. In any case, it follows that level of detail is only a theory-immanent matter. One may or may not, depending on the research project, prefer to focus only on the fact that a certain gene produces yellow blossoms. By means of this, one brings out what the gene token in question has in common with a broad set of other gene tokens. After all, the abstract concept has generally a bigger extension than its more detailed subconcepts. Or, one may focus on what a narrower set of gene tokens has in common and how the gene tokens in this set differ from other gene tokens that produce yellow blossoms as well. This more detailed sub-concept gives additional functional details about the production of yellow

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blossoms, or at least, about detected fitness differences. To put it simply, in order to explain what a broad set of entities has in common, one prefers to apply relatively abstract concepts, while in order to explain (fitness) differences, one prefers to apply relatively detailed sub-concepts. Therefore, the relationship between an abstract gene concept and its sub-concepts can be seen as integrating the abstract gene concept in its sub-concepts so that the abstract gene concept remains scientifically sound. The argument proceeds as follows: first of all, both the abstract gene concept and its sub-concepts are formulated within the vocabulary of classical genetics. Second, the only difference between an abstract gene concept and its sub-concepts is the degree of abstraction from functional details, implicitly or explicitly in the context of fitness contributions. Finally, this abstraction is thus understandable within classical genetics – it is a theory-immanent matter on which functional details one wishes to focus. To put it another way, the elimination of the abstract gene concept cannot be favoured because the sub-concepts entail the concept of the functional disposition that defines the abstract gene concept in question. For instance, the concept “gene that produces yellow blossoms” appears in each of the sub-concepts. There is no scientific impediment to the claim that an abstract gene concept brings out those salient functional features a relatively broad set of entities have in common. Third, let me reconsider the relationship between abstract gene concepts and their sub-concepts in the context of the truth-maker relation (cf. ‘truth-maker realism’, chapter I, p. 16). Entities in the world can make the application of different concepts true. There are for instance concepts of classical genetics and concepts of molecular genetics that are made true by one and the same entities. In this context, one and the same entity can also make different concepts of one and the same theory true. It is possible that one and the same entity (say e1) makes true both a more abstract gene concept, and a more detailed gene (sub-) concept. For instance, one and the same entity can make true both “gene that produces yellow blossoms” and “gene that produces yellow blossoms in a way that is advantageous for selection”. Let us summarize our points. Abstract gene concepts can be deduced from each of their sub-concepts. If the difference between an abstract gene concept and its sub-concepts is that the sub-concepts only consider additional functional details, it is a theory-immanent question of classical genetics to deduce the abstract gene concept from each of its sub-concepts. This deduction does not put in doubt the scientific soundness of abstract gene concepts because only abstract gene concepts bring out what a

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relatively broad set of gene tokens have in common. The missing link, namely the relationship between on the one hand the constructed molecular DNA concepts, and on the other hand the sub-concepts and concepts about genes of classical genetics will be considered in the second part of this section. This second section then completes the conservative reductionist approach to classical genetics. Let us survey the arguments so far that allow us to formulate a starting point for our next part. Gene types are concepts, and the truthvalues of the application of gene concepts of classical genetics supervene upon a description in terms of molecular DNA concepts. Since theories are our epistemological account of the world, since molecular genetics is relatively complete and since molecular concepts apply to any gene token in the world, the epistemological reduction of classical genetics to molecular genetics is well motivated. As we saw in our general sections, there are two main strategies, Nagel’s and Kim’s, that we can use to reduce theories to one another. On the one hand, there is Nagel’s model of reduction employs bi-conditional bridge-principles, while Kim provides a functional model of reduction (cf. ‘Nagel’s model of reduction’, chapter II, p. 89, and ‘Kim’s model of reduction’, chapter II, p. 99). But since the coextensionality between concepts of both genetic theories is necessary for epistemological reductionism, introducing the multiple realization argument seems to make a general argument against epistemological reductionism (cf. ‘necessity of co-extensionality for epistemological reductionism’, chapter II, p. 85, and ‘argument of multiple realization applied to genetics’, this chapter, p. 262). In view of that argument, Nagel’s model completely fails, and Kim’s model can only provide local reductions. However, the multiple realization argument also puts into question the ability of classical genetics to abstract from molecular details while remaining causally explanatory (cf. ‘argument of multiple realization applied to genetics’, this chapter, p. 262). To sum up, the argument of multiple realization can be read as an argument against the reducibility of classical genetics, but also as an argument in favour of geneticists elimination from the scientific world view. Kim admits this consequence, and new wave reductionism completed the eliminationist assault on classical genetics. Against this background, I have been deploying a strategy that avoids both of these consequences. Any molecular differences between DNA sequences that are genes, picked out by the multiple realization argument, make possible detecting these molecular differences in functional terms of classical genetics (cf. ‘construction of sub-concepts’, this chapter, p. 269). On this basis, it is

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possible to construct sub-concepts of gene concepts of classical genetics that are nomologically co-extensional with constructed DNA concepts referring to genes. Since the common functional gene concepts of classical genetics are abstract concepts and since sub-concepts are relatively detailed concepts, it is possible to deduce an abstract gene concept of classical genetics from each of its sub-concepts. Such a deduction does not imply the elimination of the abstract gene concepts. Having said this, let me reconsider the construction of molecular DNA concepts about genes. If the argument for the token-identity of genes and DNA is cogent (cf. ‘argument for the token-identity of genes and DNA, chapter VI, p. 247), then any property token that comes under a functionally defined gene concept of classical genetics is identical with a DNA sequence that satisfies the functional characterization in question. For instance, any gene token that comes under the concept “gene that produces yellow blossoms” is identical with a certain DNA sequence. Therefore, it is in principle possible to describe any gene token in molecular terms. For any configuration of molecular property tokens it is possible to construct a molecular concept that refers to all and only the molecular configurations that are composed in the same way. These are the “DNA sequence of type X1”, for instance as a placeholder for a detailed molecular description of the target DNA sequence. . Such a constructed concept is embedded in molecular genetics. Note that much empirical research may be needed in order to find out which molecular configuration has the effect (relative to the molecular environment) that defines the genes in question. We are dealing with the theoretical possibility, here. How does the construction of molecular DNA concepts bear on the construction of sub-concepts in classical genetics? It is possible within the vocabulary of classical genetics to construct functionally defined subconcepts that are co-extensional with the mentioned molecular DNA concepts. Given molecular differences accounting for different types of DNA sequences that are genes, there are functional differences as well (cf. ‘construction of sub-concepts’, this chapter, p. 269). It is therefore always possible to construct sub-concepts of functionally defined gene concepts such that each of these sub-concepts describes all and only the entities that are uniformly described by a molecular DNA concept. For instance, it is possible to construct sub-concepts of the gene concept “gene that produces yellow blossoms” – for example “gene that produces yellow blossoms in a way that is advantageous for selection” – such that this sub-concept is co-

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extensional with a (constructed) molecular DNA concept such as “DNA sequence of type X1”. Against this background, let us go through the argument for the epistemological reduction of sub-concepts of classical genetics to molecular genetics. Each sub-concept of abstract gene concepts is coextensional with a constructed molecular DNA concept. Thus, it is possible to establish a bridge-principle in the sense of a bi-conditional correlation between those concepts of the different genetic theories, for instance between the sub-concept “gene that produces yellow blossoms in a way that is advantageous for selection” and the molecular DNA concept “DNA sequence of type X1”. In the context of Kim’s model of reduction, this co-extensionality between concepts of the different genetic theories means that it is possible to provide homogeneous reductive explanations. The molecular DNA concept “DNA sequence of type X1” embedded in molecular genetics provides a homogeneous reductive explanation of gene tokens that come under the sub-concept “gene that produces yellow blossoms in a way that is advantageous for selection” (in general, cf. ‘Kim’s model of reduction’, chapter II, p. 99, and in particular, cf. ‘motivation for a reductionist approach to classical genetics’, chapter VI, p. 253). To put it another way, molecular genetics can explain in detail the fitness contributions of the gene tokens in question, can explain possible differences of gene tokens that differ in their fitness contributions even if they come under one and the same abstract gene concept, etc. To conclude, insofar as classical genetics only conceives such sub-concepts, it can be epistemologically reduced to molecular genetics. Finally, let us take up the defence of the scientific status of classical genetics against the eliminationist argument. Classical genetics we take to be a theory that conceives abstract law-like generalizations and explanations that are about molecularly different entities. Clearly, the functionally defined concept “gene that produces yellow blossoms” is a concept that abstracts from possible functional differences that are based on the molecular differences between the types of DNA sequences that are genes. However, this abstraction from functional details does not put into doubt the scientific soundness of the abstract gene concepts. Since it is always possible to conceive sub-concepts within the vocabulary of classical genetics, this abstraction does not invite the elimination of the abstract gene concepts of classical genetics. This crucially distinguishes our argument from Kim’s model of reduction; and, of course, opposes us to new wave reductionism (cf. ‘multiple realization argument applied to genetics’, this chapter, p. 262). In both these positions, the elimination of

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classical genetics is suggested because these positions do not take into account the possibility to construct functional sub-concepts that are coextensional with molecular DNA concepts. To conclude, the scientific character of classical genetics – to focus on salient causal relations in terms of single abstract gene concepts – is secured by means of the possibility in principle to construct sub-concepts. In this context, both the reduction and the indispensable character of classical genetics are justified: first, the sub-concepts are co-extensional with constructed molecular DNA concepts such that classical genetics can be reduced to molecular genetics by means of these sub-concepts. Based on this, second, the theory-immanent relationship between abstract gene concepts and their detailed sub-concepts does not invite the elimination of the former. Furthermore, classical genetics is indispensable because it conceives salient causal features that molecularly different entities have in common: an abstract gene concept such as “gene that produces yellow blossoms” brings out salient causal similarities that molecular genetics cannot express in a homogenous way. There is no molecular DNA concept that is co-extensional with such an abstract gene concept. Therefore, classical genetics is indispensable. That is the correct point of the multiple realization argument. However, it is wrong to conclude from the indispensability of classical genetics to its irreducibility. Let me outline this point in a recapping scheme:

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From abstract gene concepts to molecular genetics:

From molecular genetics to abstract gene concepts:

abstract gene concept of classical genetics “gene that produces yellow blossoms” “B” (take into account additional functional details and construct a more detailed concept)

↓

↑

(abstract from functional details considered in the sub-concept and focus on salient causal subrelations)

“gene that produces “B1” “B2” “gene that produces yellow blossoms yellow blossoms + selective advantage” + selective disadvantage” (co-extensional with)

“DNA sequence of type X1” (that are complex concepts that are constructed within molecular genetics)





“X1” “X2” ↓

↑

(co-extensional with)

“DNA sequence of type X2” (construct complex concepts out of concepts of molecular genetics)

Molecular genetics (General concepts of molecular genetics) Contrary to this, in the context of new wave reductionism and Kim’s model of reduction, the constructed species/structure-specific gene concepts are not expressed in purely functional terms. Instead of vindicating classical genetics, new wave reductionism and Kim’s model amount to replacing, at best, the abstract gene concepts with constructed local species/structure-specific molecular theories. Both positions tend to eliminate the abstract gene concepts of classical genetics, whereas my reductionist account makes intelligible their indispensable character. This is why the proposed strategy reaches the aim of a conservative epistemological reductionism – contrary to any other recent reductionist position. As I have shown, it is neither an argument against reductionism nor for elimination that classical genetics considers genes that are molecularly

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different. Taking the argument for multiple realization for granted, it is not possible to provide homogeneous reductive explanations of gene tokens that come under the abstract concepts of classical genetics. On the one hand, the anti-reductionist strand takes multiple realization as an argument in favour of the irreducibility of the special sciences (cf. ‘systematic framework’, chapter IV, p. 192). Contrary to this, my proposal sets out a strategy to reduce classical genetics to molecular genetics. On the other hand, Kim’s model of reduction and new wave reductionism moves logically from multiple realization to the elimination of the scientific character of classical genetics. Contrary to this, as mentioned above, my proposal avoids such an elimination of classical genetics. Let us summarize the reasons the ‘reduction of classical genetics to molecular genetics’ is upheld by a conservative reductionist theory. Classical genetics can be epistemologically reduced to molecular genetics in a conservative manner. It is possible to construct DNA concepts within molecular genetics that are co-extensional with sub-concepts of abstract gene concepts expressed in the functional vocabulary of classical genetics. In that manner, the scientific character of classical genetics is secured. The elimination of classical genetics is avoided because the abstract gene concepts about molecularly different genes can in principle be integrated in a network of sub-concepts that are co-extensional with constructed molecular DNA concepts. For that reason, it is neither an argument against reductionism nor for elimination that classical genetics considers general causal features that cannot be homogeneously explained in terms of molecular genetics.

v.

Final remarks

In this final section, I shall reconsider several issues of the discussed reduction of classical genetics to molecular genetics. First of all, I shall reconsider whether it is possible in principle to detect functional differences in terms of classical genetics. Secondly, I will look at the relationship between the argument for the token-identity of genes and DNA and the reduction of the concepts of classical genetics. Thirdly, I shall outline my understanding of abstract law-like generalizations of classical genetics such as the famous Mendelian laws. Finally, a summary of the new thesis outlined in this work will be provided. This summary will show that the issues of most anti-reductionist positions are taken into account by means of the proposed strategy of conservative reduction.

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First of all, let me look at whether it is possible in principle to detect functional differences in terms of classical genetics (cf. ‘construction of sub-concepts’, this chapter, p. 269). In our retrospect of the development from Mendel via Morgan to the birth of molecular genetics up to the Human Genome project and other current research fields, there are two points I would like to emphasize in the context of my reductionist approach. The first point is about the relationship between a gene and its possible types of alleles. For instance, an important issue of Morgan and his collaborators was to find so-called mutant alleles. These are different alleles of one type of gene where the general type of allele is called “wild type” (cf. ‘historical framework’, chapter IV, p. 183). In any case, the criterion to distinguish types of alleles is based on their different phenotypic effects. To put it another way, there is a functional criterion similar to the construction of more detailed concepts – the distinction between gene concepts and their sub-concepts as introduced in this chapter. To conclude for the time being, it is common in classical genetics to introduce or construct more detailed functionally defined concepts in any case in which it is possible to detect functional differences. The other issue in this context is about my claim that the molecular differences of DNA sequences that are genes of the same gene type can lead to functional differences of the genes in question. At least, the molecular differences lead to a different functional disposition of the gene tokens in question that can be described in terms of a mathematical function. The link to the previous point is the following: the discovered functional differences between alleles of the same type of gene generally depend on protein differences. For instance, the sickle cell anaemia is caused because of a DNA difference in the corresponding gene. This produces a protein that differs with respect to the wild type of the allele that produces the common protein. To put it another way, a molecular difference, which is in fact a difference of one single DNA base, leads to a functional difference that can be easily detected. In this case, anyone of the anti-reductionist strand concedes that there are two types of genes (alleles) distinguished by their different functional dispositions. However, my reductionist strategy goes beyond such known cases and examples of specifying types of genes into sub-types. What I claim is that DNA differences that lead to the same protein (so-called silent DNA differences) nonetheless have different functional impacts for the organism in question. This is a claim that cannot easily be supported by experiments just because these functional differences are, if they occur at all in our laboratories, rare and minimal in their differences.

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Since I have already argued for the nonetheless remaining principled possibility to detect functional differences that are based on minimal molecular differences (cf. ‘construction of sub-concepts’, this chapter, p.269), let me focus at this point here on this principled possibility. I do not claim that classical genetics should be actually modified such that it constructs sub-concepts of each gene concept in order to establish coextensionality with molecular gene concepts. A philosophical reflection on the relationship between classical and molecular genetics does not need to have any consequences for current research programmes – even if it could lead to constructive consequences in research. In any case, let us bear in mind that multiply realized gene types are gene concepts that abstract from ontological details that can (in certain environmental conditions) be salient for selection. In this context, the anti-reductionist strand does definitely not lead to any constructive consequence, as it undermines the scientific soundness of classical genetics. . Let me add that the new wave reductionism and Kim’s local reductions cannot make the systematic relation between classical and molecular genetics intelligible either: they lead in the last resort to the elimination of the abstract gene concepts of classical genetics. In neither case, a systematic relationship by means of co-extensional concepts is established. These positions can therefore not make intelligible why classical genetics still illuminates our understanding of heredity. Contrary to both the anti-reductionist strand and new wave reductionism or Kim’s model, my proposed strategy can make intelligible this explanatory contribution of classical genetics for our understanding of heredity and related issues. To sum up, to bring out salient causal similarities among genes by means of abstract gene concepts of classical genetics is of scientific value only within a reductionist framework. Its scientific character can be justified by the principle possibility to construct functionally defined sub-concepts as the bridges between classical and molecular genetics. Second, let me consider the relationship between the argument for the token-identity of genes and DNA, and the reduction of the concepts of classical genetics (cf. ‘argument for the token-identity of genes and DNA’, chapter VI, p. 247, and ‘reduction of classical genetics to molecular genetics’, this section, p. 289). Let me take into account considerations of the general part, especially of chapter III. The starting point of the issues here is that there is a strong argument for the identity of genes with DNA. However, the multiple realization argument suggests that the abstract gene concepts of classical genetics are generally not co-extensional with

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molecular DNA concepts. The dilemma of this strong anti-reductionist argument is that it seems to lead either to the elimination of classical genetics or to the refutation of ontological reductionism. Either, the argument of multiple realization suggests the elimination of classical genetics – contrary to the intentions of those who conceived that argument in the anti-reductionist strand. Or, the argument, taken as an antireductionist argument, is not compatible with the token-identity of genes and DNA. Since the former implication is already considered in this chapter, let me examine this latter implication in more detail (cf. ‘multiple realization applied to genetics’, this chapter, p. 262). I take for granted that the abstract gene concepts of classical genetics are scientifically indispensable. This means, classical genetics is able to focus on salient homogeneous causal relations in a manner molecular genetics is not able to do. To put it another way, there is no molecular homogeneity between different types of DNA sequences of genes coming under one abstract gene concept. Since there is no such molecular homogeneity and since nonetheless the functionally defined gene concepts of classical genetics seize salient homogeneous causal relations, these concepts cannot be reduced by Kim’s strategy of local, at most species/structure-specific reductions (or new wave reductionism). To put it another way, we start with the indispensable scientific character of the concepts of classical genetics. Then, we take the multiple realization argument to imply that neither the elimination nor the reduction of classical genetics is possible. If classical genetics captures some causal relations outside of the scope of molecular genetics then it follows that the salient causal relations that classical genetics considers in its terms are ontologically not identical with something molecular (compare my considerations in ‘the multiple realization argument applied to genetics’, this chapter, p. 262). This means, there is something ontological beyond configurations of molecular property tokens. If classical genetics can neither be reduced because of the multiple realization argument nor be eliminated by means of the strategies of Kim and new wave reductionism, then there have to be ontological differences between the gene tokens of classical genetics and DNA sequences of molecular genetics. As a result of this, the truth-makers of the gene concepts of classical genetics differ ontologically from the truth-makers of the molecular DNA concepts. This means, there is no token-identity of gene tokens of classical genetics with tokens of DNA sequences. Let me consider the consequence of such a possibility. Taking the causal efficacy of gene tokens of classical genetics for granted, if there is

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no token-identity, the consequence is ontological dualism based on either the rejection of the relative completeness of molecular genetics or the rejection of supervenience. Let me note in this context that I do not consider over-determination or parallelism as an attractive alternative. After all, they lead to epiphenomenalism and thus eliminativism (cf. ‘argument for the token-identity of genes and DNA’, chapter VI, p. 247). Either, first, the gene tokens of classical genetics have molecular effects (downward causation, interactionism). Then, the principle of the relative completeness of molecular genetics is violated. Since the relative completeness of molecular genetics is a necessary premise for the argument of token-identity of genes and DNA, the rejection of the completeness claim is not compatible with such a token-identity. Or, second, there are causal effects of the gene tokens of classical genetics that have only effects on other gene tokens of classical genetics. In this case, the principle of the relative completeness of molecular genetics can still be valid, but the supervenience thesis must be rejected. There is independent variation such that again there are ontological differences between gene tokens of classical genetics and molecular DNA sequences. The first conclusion therefore is that the token-identity of genes and DNA is not compatible with epistemological anti-reductionism. Taking the token-identity argument for granted, either classical genetics can be reduced to molecular genetics, or the elimination of classical genetics is suggested. It is not possible that the scientific character of classical genetics is indispensable without classical genetics being reducible to molecular genetics or the token-identity argument being false. Provided that my argument of this chapter is cogent, my reductionist strategy combines the indispensable scientific character of classical genetics with its reducibility to molecular genetics. Against the background of the considered issues, mine seems to be the only strategy that avoids the elimination of scientific disenfranchisement of classical genetics. In this context, furthermore, let us keep in mind that epistemological reductionism implies ontological reductionism (cf. ‘starting point epistemological reductionism’, chapter III, p. 173, ‘incompatibility of epistemological reductionism with property dualism’, chapter III, p. 174). This means, the reduction of classical genetics to molecular genetics is not compatible with the rejection of the tokenidentity of genes and DNA. Provided that epistemological reductionism requires the co-extensionality of the concepts of the two genetic theories in question, it implies the token-identity of the referents. In order to deduce the gene concepts and the explanations of classical genetics from

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molecular genetics, ontological differences between the referents of the gene concepts and the corresponding molecular DNA concepts have to be excluded. Third, let us look at what we have learned about the systematic place of the abstract law-like generalizations of classical genetics such as the famous Mendelian laws (cf. ‘historical framework’, chapter IV, p. 183). Let us assume that the famous Mendelian laws, or their modifications by Morgan et al. truly apply to a certain gene, or more appropriate, to a certain set of genes as considered in the breeding experiments of Pisum sativum or Drosophila melanogaster. Of course, there are molecular differences between the considered gene tokens in question. Therefore, it is not possible to construct law-like generalizations in terms of molecular genetics that are co-extensional with the mentioned Mendelian laws or the modifications by means of Morgan. This is a case of multiple realization. As already considered, it is possible to represent classical genetics by means of functionally defined gene concepts (cf. ‘the importance of the gene concept’, chapter V, p. 215, and ‘functional characterization of the gene’, chapter V, p. 220). The argument is that the gene concept is fundamental for the theory of classical genetics. In other words, any essential concept of classical genetics about a certain entity figures in the functional characterization of the corresponding functionally defined gene concept. In this context, the Mendelian laws figure implicitly in any functional characterization of the gene type in question. For instance, the statistical distribution of recessive alleles of a certain type of gene over n generations (as described by Mendel) appears in the corresponding functionally defined gene concept. It is also possible to make explicit the modifications of these Mendelian laws introduced by Morgan and his collaborators (cf. ‘historical framework’, chapter IV, p. 183). Provisionally we can say that the Mendelian laws or their modifications by Morgan et al. are contained (at least implicitly) in any functional characterization of the gene type in question. Against this background, let me now consider whether or not the Mendelian laws and the modifications as expressed by Morgan and his collaborators are conservatively reduced to molecular genetics as well. Obviously, the Mendelian laws and their modifications abstract from ontological details because they apply to genes that are molecularly different. This means, they abstract from causal dispositions. Taking for granted our reductionist strategy, it is possible to distinguish these molecular differences in terms of classical genetics, too, making explicit the possible fitness contributions. These are the functionally defined sub-

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concepts of the gene concepts. From each of these sub-concepts, it is possible, in the last resort, to deduce the Mendelian laws because they are, provided they apply to the genes in question, implicitly expressed in the functional characterization of the gene in question. In a simplified manner, the Mendelian laws are functional abstractions of the functionally defined gene concepts as outlined in chapter V. Thus, the relationship between the Mendelian laws and the gene concepts is like the relationship between a certain gene concept and its sub-concepts. Let me illustrate this conservative reduction of the Mendelian laws and their modifications in the context of the gene that produces yellow blossoms. Let us take for granted that the Mendelian laws and their modifications correctly describe the statistical distributions of the alleles among the offspring of the flowers in question. Thus, these laws are true about the entities in question, and therefore, they can be considered in the functional characterization of the gene type in question. This is the first issue. The second issue is the multiple realizability of the gene type in question (the genes that produce yellow blossoms). This means, as outlined several times in this chapter, there are molecular differences among the DNA sequences possible that are nonetheless genes that produce yellow blossoms. Thus, it is not possible to construct law-like generalizations that are co-extensional with the functionally defined gene concept in question. However, in the context of my reductionist strategy, we can construct functionally defined sub-concepts of the gene concept about genes that produce yellow blossoms. These sub-concepts can be biconditionally correlated with molecular DNA concepts. The Mendelian laws and their modifications figure in each of these sub-concepts. This means, the functional description of certain genes that produce yellow blossoms by means of the functionally defined sub-concept contains the application of the Mendelian laws and their modifications. To put it simply, there are genes that produce yellow blossoms (abstract functional characterization), and they produce yellow blossoms in a way that is salient in the context of selection (specification of the fitness contributions by means of a mathematical function), and they will be inherited according to a certain statistical ratio (application of the Mendelian laws and their modifications). Against this context, the only difference between such sub-concepts and the more abstract gene concepts is the following: the functionally defined sub-concepts contain a specification of the fitness contributions by means of a mathematical function. This specification does not appear in

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the abstract gene concept. Thus, it is possible to deduce the abstract gene concept from each of its sub-concepts (cf. ‘reduction of classical genetics to molecular genetics’, this chapter, p. 289). Then, the only difference between the Mendelian laws (and their modifications by Morgan et al.) and the mentioned abstract gene concept is the following: the Mendelian laws and their modifications are abstract concepts which are not restricted in their application to the genes that produce yellow blossoms. Thus, the only difference between them is the degree of abstraction. Furthermore, the truth of the application of the Mendelian laws and their modifications to the genes that produce yellow blossoms can be deduced from the functionally defined gene concept (that contains these Mendelian laws and their modifications – at least implicitly). To sum up, the scientific soundness of the Mendelian laws and their modifications can be justified by means of the proposed reductionist approach: functionally defined gene concepts contain these abstract laws, and by means of the construction of functionally defined sub-concepts, it is possible to reduce them to molecular genetics. Furthermore, these abstract Mendelian laws and their modification according to Morgan et al. are indispensable from a scientific point of view because they apply to genes that are molecularly different. Thus, they bring out salient similarities among genes (and also among different types of genes) that molecular genetics cannot bring out in a homogeneous way. Our final statement of the conservative reductionist strategy is that, in the context of evolution, natural selection, fitness contributions, etc., any true law-like generalization that ever figured in a genetic theory between Mendel and 1953 can be conservatively reduced to molecular genetics. Summarizing the points in this dissertation, we have argued as follows. Taking the completeness claim of physics and the concept of supervenience for granted, there is a strong argument for ontological reductionism. This means, any causally efficacious property token of the special sciences is identical with a configuration of physical property tokens. This is the main result of chapter one, and something like a common ground nowadays in any debate about reductionism and antireductionism in the philosophy of science. Against this background, chapter two considers the relationship between the special sciences and physics. Since both physics and the special sciences provide our epistemological account to describe and explain the same entities in the world (result of chapter one), one may put forward questions about their relationship. What about the special status of physics to describe and explain any entity in the world, what about the

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autonomy and the indispensable character of the special sciences to describe and explain the entities of their proper domain? In order to examine these questions, the standard reductionist models were considered and faced with the most compelling anti-reductionist argument – the argument of multiple realization. In this context, the model of Ernest Nagel failed to provide a reductionist account while Jaegwon Kim’s model of functional reduction establishes species/structure-specific reductions. Nonetheless, Kim’s approach cannot make intelligible the indispensable character of the special sciences. The scientific quality of the abstract concepts of the special sciences is put into peril in any case of multiple realization (reference). Keeping this in mind, the multiple realization argument per se was considered, and new wave reductionism was examined. This approach shows that, in principle, we can construct physical theories that match any theory of the special sciences. In the context of the completeness of physics, such constructed physical theories are preferred with respect to the special science theory in question. Therefore, New Wave Reductionism leads to the elimination of the special sciences. This result is what I called the dilemma of the multiple realization argument: taking the multiple realization argument as an anti-reductionist argument, it is not possible to justify the scientific quality of the special sciences without ending up in eliminativism. To conclude, leaving aside Nagel’s model that fails in the context of multiple realization, Kim does not provide a positive account to the scientific quality of the special sciences, and the New Wave Reductionism leads to the elimination of the special sciences. Against this background, I proposed a new reductionist approach that both takes the multiple realization argument into account, and is a non-eliminativist reduction. This means, I proposed a general strategy to reduce conservatively the special sciences to physics. Thereby, a systematic link of co-extensional concepts is established by means of socalled functionally defined sub-concepts that take into account possible functional differences of physical differences. Both the link between such sub-concepts and physical concepts, and between these sub-concepts and more abstract concepts of the special sciences is intelligible from the scientific standpoint. To put it another way, the multiple realization is the argument for the scientific soundness of the special sciences, but in a reductionist framework. There remains nothing spurious about the capacity of the special sciences to abstract from physical details and focus on salient similarities among entities. This capacity is what makes classical genetics indispensable nowadays – that there is a more abstract scientific

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point of view even though any causal detail is explained in molecular genetics. To put it another way, the gene concept as characterized in terms of classical genetics bring out salient similarities among DNA sequences molecular genetics cannot bring out. Thus, there are different standards for description and explanation.121 These can be taken into account in a reductionist approach, as I have shown. To conclude, my work shows a way to compatibility on both the unity and the plurality of sciences. All there is in the world is something physical, but there are different (physical) sciences.

121

Cf. Kitcher (1981) and Sober (1999).

307

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[Footnote 5 on p. 24, 16 on p. 58, 49 on p. 141, and 115 on p. 273]

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Waters, C. Kenneth: “Why the antireductionist consensus won’t survive: the case of classical Mendelian genetics” (1990) PSA: Proceedings of the 1990 Biennial Meeting of the Philosophy of Science Association, 1: pp. 125-139. [Footnote 79 on p. 192]

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325

Index A abstraction....................................., 8, 129, 134, 138, 147, 154, 156, 161, 180, 181, 265, 266, 280, 291, 294, 304 Allen, Garland E., ....................186 anti-reductionism, .......................... 137, 169-172, 177, 268, 301, 304 autonomy, ...................................... .............8, 13, 137, 205, 268, 305 Avery, Oswald Theordore, .......189 B Beadle, George Wells,...... 188, 217 Bechtel, William, .....................138 Benzer, Seymour,.....................190 Beurton, Peter, .........................192 Bickle, John, .............. 99, 134, 266 Bigelow, John, .........................225 Block, Ned, ................................58 Boveri, Heinrich Theodor,.............. ....................... 186-188, 209, 218 Brenner, Sydney,.............. 190, 191 Bridges, Calvin Blackman,............. ...................................... 185, 186 C Campbell, Neil A., ... 208, 261, 276 causal role, ....................... 225, 262 ceteris paribus, 202, 222, 239, 253 Chalmers, David J., ....................... .....................33, 74, 75, 100, 212 Chargaff, Erwin,.......................189 Chase, Marta, ...........................189 Christmann, M., .......................275 Churchland, Paul M., .................99

concepts, abstract concepts,........................ 150-157, 159, 162, 163, 180, 283, 289, 290 biological concepts, .................... 11, 16-18, 22, 36, 46, 65, 6870, 75, 78-81, 85, 86, 88, 90, 91, 96-98, 101-103, 105-107, 110, 113-115, 118, 119, 121, 123, 125, 134, 135, 139, 141, 162, 169, 175 co-extensional concepts, ............. 89, 117, 120, 137, 259, 299, 305 concepts of the special sciences, . 8, 9, 13, 16, 40, 61, 63, 79-84, 98-100, 107, 109, 113-116, 118-121, 125, 128, 130, 134137, 139, 140, 159, 162, 164, 166, 168-175, 178-181, 305 functionally defined concepts, .... 8, 75, 76, 89, 100-118, 123, 128, 150-153, 159-161, 168, 198, 203-205, 221, 225, 238, 260, 265, 273, 289, 294, 298 physical concepts,....................... 7, 9, 11-13, 16-18, 22, 27, 30, 40, 41, 44, 46, 48, 61, 63, 64, 69, 77-80, 82-86, 88, 91-102, 104-109, 114, 118-121, 123125, 127-132, 134-139, 141, 142, 144, 149-152, 159-163, 169, 175, 179-181, 305 Correns, Carl, ................................ ...............184, 186-188, 197, 220 Crane, Tim,................................ 24

326

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Crick, Francis H. C.,....................... ...............189, 198, 203, 220, 232 Croxton, Rhonda, .....................272 Cummins, Robert, ....................225 cytology, .................. 185, 202, 208 D Darden, Lindley, ...... 183, 186, 195 De Vries, Hugo, .......................184 deduction, ...................................... 73-75, 85, 86, 89, 98, 100, 108, 122, 134, 157, 159, 173, 174, 196, 265, 291, 293 development,.................................. 15, 40, 71, 72, 92, 183, 185-193, 202, 203, 208, 212, 219, 220, 235, 237, 255, 298 dilemma, ........................................ 137, 166, 182, 257, 261, 262, 268, 300, 305 disposition,..................................... 42, 43, 76, 112, 132, 143, 144, 146, 148, 209, 216, 225-227, 232, 235, 238, 239, 241, 243, 247, 252-254, 258, 263, 265, 270, 276, 277, 279, 280, 284, 289-291, 298 Dobzhansky, Theodosius,.........281 dominance,....... 183, 184, 221, 253 dualism, ......................................... 21-23, 167, 170-172, 174-177, 181, 301 duplicate,........................................ 13, 33-35, 37-40, 53, 54, 56, 58, 108, 140, 147, 212, 213, 250, 251 E elimination, .................................... 8, 63, 98, 128, 129, 133, 137, 145, 146, 149, 153, 154, 158,

159, 161-164, 166, 167, 169172, 177-179, 181, 182, 201, 202, 216, 264, 279, 291, 292, 294-297, 299-301, 305 eliminativism, ................................ 131, 144, 170, 172, 178, 202, 301, 305 emergence,................................. 35 Endicott, Ronald, ............. 135, 266 entity, ............................................ 10, 13, 16-18, 21-23, 26, 28, 31, 45-47, 57, 64-66, 68, 69-71, 7375, 78-82, 87, 88, 96, 102, 108, 109, 119, 139, 153, 154-156, 160, 188, 203, 205, 219, 221, 240, 244, 246, 259, 291, 302, 304 environment, ................................. 30, 37, 42-44, 46, 59, 80, 112, 131, 132, 140-143, 148, 150, 175, 223, 224, 227, 238, 239, 248, 262, 263, 266, 273-275, 277, 284-286, 293 epiphenomenon,......31, 32, 57, 170 epiphenomenal,..53, 54, 250, 251 epiphenomenalism, ........................ 40, 53, 54, 57, 58, 174, 176, 244, 250, 251, 301 evolution, ...................................... 34, 43, 183, 185-190, 203, 208, 219, 222, 223, 255, 281, 304 explanation, biological explanation,................ ..........................31, 65, 104, 130 causal explanation, ..................... 28, 74-76, 78, 103, 114, 127, 129, 217, 220, 243, 246, 253, 258 deductive-nomological, explanation ....................... 73, 74

IX. Index

homogeneous explanation, ....130 physical explanation,................... ..25, 27, 28, 74-76, 104, 108, 147 reductive explanation, ................. 75, 76, 104, 107, 108, 114, 120, 123, 125, 126, 132, 280 F factor,................................. 44, 209 Falk, Raphael, ..........................192 Fisher, Sir Ronald Alymer,............. ...................................... 183, 188 Fodor, Jerry A., ............................. ...............117, 122, 133, 136, 164 Friedman, Michael, ....................72 function, 42, 43, 45, 65, 69, 104, 114, 144, 147, 188, 190, 204, 205, 216, 217, 220-226, 233, 253, 262, 269, 272, 282, 285287, 290, 298, 303 aetiological,............223, 224-226 biological, ............. 222, 223, 225 functionalism, ............................72 G Goosens, William K., ...............192 Grossman. Lawrence,...............271 H Haldane, John Burdon Sunderson, . ..............................................188 Hasker, William, ........................24 Heil, John,............. 16-18, 112, 140 Hempel, Carl Gustav, ...........71, 72 heredity, ......................................... 182-190, 203, 208, 216, 217, 219, 237, 255, 264, 279, 299 Hershey, Alfred Day, ...............189 Hooker, Clifford A., ...................... ...........92, 99, 135, 157, 160, 259 Hull, David L., ................. 118, 195

327

I identity, ......................................... 13, 22, 45-47, 51, 55-60, 84, 112, 133, 178, 211, 215, 231, 239, 241, 247, 249, 252, 258, 259, 264, 265, 267, 293, 299, 301 image relation, ......................... 135 inheritance, .................................... 184, 193, 208, 209, 212, 217, 218, 219, 221, 228, 240, 255 J Jackson, Frank, .............................. ............ 33, 36, 37, 100, 112, 212 K Kaplan, David M., ......................... ...................... 192, 195, 202, 222 Kim, Jaegwon, .............................. 20, 36, 42, 51, 53, 58, 63, 75, 76, 83, 84, 90, 99-103, 106-108, 113, 120, 122-124, 127-131, 133, 134, 136, 139, 146, 149, 157, 158, 160, 161, 164, 166, 168-171, 179, 262, 266, 279, 292, 294, 296, 297, 299, 300, 305 Kimbrough, Steven Orla, ............... ................................192,195,215 Kincaid, Harold, ...................... 195 Kitcher, Philip, .............................. 72, 195, 200, 202, 228, 254, 260, 306 L Laurence, S,............................. 100 law,................................................ 25-29, 31-33, 52, 57, 64, 65, 7175, 82-90, 92-98, 115, 117, 120122, 134-137, 145, 151, 152,

328

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155-157, 159-162, 164, 170, 173, 174, 176-178, 184, 185, 187, 193, 194, 196, 197, 200202, 205, 207, 208, 220, 221, 239, 242-247, 249, 250, 252, 255, 258, 259, 278, 288, 294, 297, 302-304 law-like generalizations,.............. 71, 73, 74, 84-90, 92-95, 97, 98, 120-122, 135, 151, 155, 161163, 173, 174, 193, 194, 202, 220, 221, 243-247, 249, 258, 304 Mendelian laws, ......................... 184, 201, 209, 288, 297, 302-304 physical laws,................................. 25, 28, 30, 57, 94, 95, 135, 137, 147 layered view of the world ..... 18-23 levels, ............................................ 20, 58-60, 150, 193, 197, 200, 240, 241, 255, 256, 261, 273, 274, 290 level of description, .......... 18-20 Lewis, David,..... 74, 102, 123, 160 Lewontin, Richard C., ..............188 Loewer, Barry, .....................24, 58 M Marmur, Julius, ........................271 Marras, Antonio, .............. 100, 107 McCarty, Maclyn, ....................189 McCauley, Robert N., .................... .............................. 134, 138, 266 McLaughlin, Peter,...................222 Melnyk, Andrew, .....................100 Mendel, Gregor, ............................. 183-188, 197, 202, 208-210, 213, 215-220, 225, 239, 254, 277, 298, 302, 304

Mendelian laws, ......................... 184, 201, 209, 288, 297, 302304 Meselson, Matthew Stanley, .......... ..................................... 190, 191 Morgan, C. Loyd, ...................... 20 Morgan, Thomas Hunt,.................. 185-188, 192, 203, 208, 209, 211, 215, 217-220, 225, 298, 302, 304 Morita, Eugene Hayato, ........... 280 Muller, Hermann Joseph,............... .............................. 185-189, 192 multiple realization, ....................... 8, 9, 12, 63-68, 77, 87, 96-99, 107, 117-124, 127, 131-139, 141, 144, 146, 149, 150, 155, 156, 158, 162, 164, 166, 168171, 179-182, 196, 197, 199, 200, 202, 204, 205, 207, 253, 257, 258, 260-270, 273, 279, 282, 292, 294, 295, 297, 299, 300, 302, 305 multiple reference, ................... 262 Mumford, Stephen, .................. 112 N Nagel, Ernest, ................................ 63, 73, 83, 84, 86, 89, 90, 92, 96, 98, 99, 101, 106-109, 117, 120, 122, 127, 135, 136, 157, 158, 160, 161, 166, 169, 179, 192, 195, 259, 292, 305 natural kind,......................... 10, 68 O object, ........................................... 46, 47, 91, 99, 140, 183, 228, 238, 239, 255 Olby, Robert, ........................... 183 Oppenheim, Paul, .......... 20, 71, 72

IX. Index

P Papineau, David, .. 24, 58, 141, 273 Pargetter, Robert, ............. 112, 225 Pettit, Philip, ..............................24 Prior, Elisabeth,................ 112, 242 property type, .....41-43, 65-68, 120 Psillos, Stathis, ...........................71 Putnam, Hilary, ............................. .................20, 117, 133, 136, 164 R realism, ......................................... 10, 16-18, 21-23, 41, 79, 155, 291 realizer, .......................................... 100-102, 104-106, 108, 109, 114, 115, 121, 123, 125-127, 138, 146, 148, 149, 151, 152, 155, 157, 159, 160, 206, 279 reductionism, conservative reductionism,.......... 7, 9, 88, 139, 158, 166, 167, 177, 178, 181, 202, 205 epistemological reductionism, .... 7-9, 11, 13, 40, 63, 71, 79, 8385, 87-90, 92, 95, 96, 98, 100, 101, 104-108, 115, 117, 120, 123, 128, 130, 137-139, 145, 149, 151, 152, 157-159, 164, 166-169, 173, 174, 176, 177, 180, 289, 292, 296, 301 new wave reductionism, ............. 98, 99, 133, 134, 136, 144, 149, 157, 158, 161, 164, 170, 171, 179, 266-268, 278, 292, 294, 296, 297, 299, 300, 305 ontological reductionism, .............. 7-9, 11, 13, 15, 21, 23, 24, 40, 51, 56, 57, 60, 64-68, 79, 81-83, 85, 87, 90, 92, 97, 102, 105, 108,

329

112, 117, 120, 125, 129, 133, 136, 137, 159, 166-174, 176, 177, 178, 180, 182, 193, 196, 199, 206, 241, 264, 268, 300, 301, 304 relative completeness,.................... 24, 59, 60, 193, 242, 247-249, 251-253, 258, 261, 267, 301 replication,..................................... .190-193, 232-234, 236-238, 317 Rheinberger, Hans-Jörg, .. 183, 192 Rosenberg, Alexander, .................. 118, 141, 192, 195, 202, 212, 222, 274 Ruse, Michael, ......................... 192 S Salmon, Wesley, ...........72, 73, 222 Sarkar, Sahotra, ....................... 192 Schaffner, Kenneth F., ....... 99, 192 scientific progress, ....185, 203, 208 scientific quality, .......................... 88, 133, 136, 137, 154, 157, 161, 166, 180, 201, 204, 257, 305 scientific status, ............................ 133, 146, 152, 157, 164, 170, 200, 279, 294 scientific value, ............................. ............ 9, 77, 178, 202, 264, 299 selection, ....................................... 142-144, 150, 151, 153-155, 160-162, 186, 188, 222, 223, 270, 274, 275, 277, 281-283, 285, 287, 289-291, 293, 294, 299, 303, 304 Sherwood, Eva R., ................... 183 Shoemaker, Sydney, .......... 42, 148 Sider, Theodore, ........................ 47 Sober, Elliot,.................... 133, 306 Stahl, Franklin, ........................ 191 Stephan, Achim, .................. 20, 35

330

Reductionism in the philosophy of science

Stern, Curt,...............................183 Stryer, Lubert, ............................... ....... 232, 236, 237, 254, 271, 276 Sturtevant, Alfred Harry, ..185-187 sub-concept, ................................... 88, 150, 151, 153, 155, 156, 160163, 181, 282-284, 287, 290, 293, 294, 296, 303 Sutton, Stanborough Water, ........... ....................... 186-188, 209, 218 system, .......................................... 10-13, 19-21, 38, 39, 112, 115, 146, 180, 205 T Tatum, Edward Lawrie,.... 188, 217 token-identity, ................................ 7, 14, 22, 24, 40-47, 54-60, 64, 79, 81-83, 100, 102, 133, 159, 168, 171, 176, 178, 199, 206, 207, 211, 214, 231, 239, 247, 249, 251-253, 255, 258, 259, 261, 262, 264, 267, 268, 293, 297, 299-301 Tschermak-Seysenegg,................... .............................. 184, 186, 197 trait,.................................. 184, 216

transmission,.................... 184, 188 truth-maker/making, ...................... 10, 16-18, 21-23, 41, 44, 79, 118, 129, 155, 178, 241, 291 U unification/unificationist, ............... ............................72, 77, 78, 224 V Vance, Russel E.,............. 195, 260 W Waters, C. Kenneth,....................... 192, 195, 215, 217, 228, 238, 240, 274 Watson, James D., ......................... .............. 189, 198, 203, 220, 232 Weber, Marcel, .............................. .............. 183, 187, 192, 222, 226 Wilson, Edmund Beecher, ....... 186 Woodward, James,..................... 71 Wright, Larry,.......................... 223 Wright, Sewall Green, ............. 188 Y Yablo,...................................... 156