C:/ITOOLS/WMS/CUP-NEW/21715866/WORKINGFOLDER/ROSENBERG-ELE/9781108742313PRE.3D i [1–4] 27.3.2020 8:04PM Elements in the Philosophy of Biology edited by Grant Ramsey KU Leuven Michael Ruse Florida State University REDUCTION AND MECHANISM Alex Rosenberg Duke University C:/ITOOLS/WMS/CUP-NEW/21715866/WORKINGFOLDER/ROSENBERG-ELE/9781108742313PRE.3D ii [1–4] 27.3.2020 8:04PM University Printing House, Cambridge CB2 8BS, United Kingdom One Liberty Plaza, 20th Floor, New York, NY 10006, USA 477 Williamstown Road, Port Melbourne, VIC 3207, Australia 314–321, 3rd Floor, Plot 3, Splendor Forum, Jasola District Centre, New Delhi – 110025, India 79 Anson Road, #06–04/06, Singapore 079906 Cambridge University Press is part of the University of Cambridge. It furthers the University’s mission by disseminating knowledge in the pursuit of education, learning, and research at the highest international levels of excellence. www.cambridge.org Information on this title: www.cambridge.org/9781108742313 DOI: 10.1017/9781108592949 © Alex Rosenberg 2020 This publication is in copyright. Subject to statutory exception and to the provisions of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. First published 2020 A catalogue record for this publication is available from the British Library. ISBN 978-1-108-74231-3 Paperback ISSN 2515-1118 (print) ISSN 2515-1126 (online) Cambridge University Press has no responsibility for the persistence or accuracy of URLs for external or third-party internet websites referred to in this publication and does not guarantee that any content on such websites is, or will remain, accurate or appropriate. C:/ITOOLS/WMS/CUP-NEW/21715866/WORKINGFOLDER/ROSENBERG-ELE/9781108742313PRE.3D iii [1–4] 27.3.2020 8:04PM Reduction and Mechanism Elements in the Philosophy of Biology DOI: 10.1017/9781108592949 First published online: tbc Alex Rosenberg Duke University Abstract: Reductionism is a widely endorsed methodology among biologists, a metaphysical theory advanced to vindicate the biologist’s methodology, and an epistemic thesis those opposed to reductionism have been eager to refute. While the methodology has gone from strength to strength in its history of achievements, the metaphysical thesis grounding it remained controversial despite its significant changes over the last seventy-five years of the philosophy of science. Meanwhile, antireductionism about biology, and especially Darwinian natural selection, became orthodoxy in philosophy of mind, philosophy of science, and philosophy of biology. This Element expounds the debate about reductionism in biology, from the work of the post-positivists to the end-of-the-century debates about supervenience, multiple realizability, and explanatory exclusion. It shows how the more widely accepted twenty-first-century doctrine of “mechanism”–reductionism with a human face – inherits both the strengths and the challenges of the view it has largely supplanted. Keywords: reductionism, mechanism, special sciences © Alex Rosenberg 2020 ISBNs: 9781108742313 (PB), 9781108592949 (OC) ISSNs: 2515-1126 (online), 2515-1118 (print) C:/ITOOLS/WMS/CUP-NEW/21715866/WORKINGFOLDER/ROSENBERG-ELE/9781108742313PRE.3D iv [1–4] 27.3.2020 8:04PM Contents Introduction 1 1 What Was Reductionism? 8 2 Biology as Natural History 27 3 Reductionism and Natural Selection 39 4 Reduction Makes Way for Mechanism 55 Conclusion: Mechanism, Causation, Physicalism, and the Laws of Nature 66 Bibliography 71 C:/ITOOLS/WMS/CUP-NEW/21715866/WORKINGFOLDER/ROSENBERG-ELE/9781108742313C01.3D 1 [1–70] 27.3.2020 7:53PM Reduction and Mechanism 1 Introduction Reductionism is a metaphysical thesis, a claim about explanations, and a research program. The research program is pursued by scientists, who point to great achieve- ments that encourage its pursuit while recognizing the important challenges it still faces. What this program demands is that biology and the life sciences generally employ an opportunistic, top-down research strategy, always seeking more fundamental explanations that will complete, correct, or otherwise improve on previous explanatory achievements. Reductionism is often treated as also requiring an equivalent research program in the behavioral and social sciences, which, following Fodor (1974), have come to be called the “special sciences.” This extension is not unwarranted, since the special sciences are devoted to the study of one or a small number of biological kinds: hominins and higher primates. Reductionism as a research program among biologists doesn’t impose a bottom-up strategy that requires all biological research to begin at the molecular level. It only requires it to end there. The actual reductions these biologists have provided are illustrations to them and to reductionist philosophers of how biological explanation at its best proceeds. The successes motivate biologists far more than any philosophical arguments. Among these successes are at least the following: the molecular account of respiration all the way down to the oxygen affinity of the iron molecule in the four-unit adult and fetal hemoglobin protein molecules, their allosteric properties, and the roles of coenzymes such as 2,3-diphosphoglycerate (DPG) in their positive cooperativity (Perutz, 1962); the central dogma of molecular genetics (Watson, 1965) and its associated achievements in the explanation of heredity and somatic gene regulation; the specific role of somatic gene regulation in embryological development (Lawrence, 1992); sensory transduction in the visual system (Montell, 2003); and the less spectacular successes of the physical understanding of photosynth- esis as a chemical process – the Calvin cycle – and the even earlier detailing of the mechanism of cellular metabolism in the tricarboxylic acid (TCA) or Krebs citric acid cycle. By itself, a list of successes of this sort is at best a relatively weak inductive argument for reductionism as the methodology of a research program that will succeed everywhere in the life sciences. A few biologists have tried to provide more arguments for why such a program should face no limits and be expected to succeed everywhere in the life sciences. Of these, the most visibly explicit advocates of reductionism were the Nobel laureates J. Monod (1971) and F. Crick (1966). By and large, their arguments were metaphysical: the nature of reality as being wholly physical motivated their reductionism. But C:/ITOOLS/WMS/CUP-NEW/21715866/WORKINGFOLDER/ROSENBERG-ELE/9781108742313C01.3D 2 [1–70] 27.3.2020 7:53PM 2 Elements in the Philosophy of Biology metaphysics doesn’t much concern biologists, when they even notice it at all. Philosophers, however, are not indifferent to it. Philosophers who endorse the research program on which biologists such as Monod and Crick placed their bet ground their confidence in its eventual metaphysical vindication, which they identify as physicalism: All of the facts empirical science deals with are physical facts – facts about physical matter and physical fields. Reductionism’s biological and philosophical opponents reject the research program as misguided because they insist there are many excellent irreducible explanations in biology. In the words of one of the most prominent of anti- reductionists, reductionism’s “mistake consists in the loss of understanding through immersion in detail, with concomitant failure to represent generalities that are important to ‘growth and form’ [invoking D’Arcy Wentworth Thompson’s expression]” (Kitcher, 1999, p. 206). As we will see, they proffer examples of such fully adequate but irreducible explanations. Many (perhaps most) philosophers who reject reductionism as a research program or a thesis about explanation embrace a metaphysical commitment to physicalism. This is especially true among philosophers of mind and philoso- phers of psychology who do not wish to endorse dualism or the existence of mind or mental events, states, or processes distinct from physical events, states, or processes. Physicalist antireductionism is in fact the most widely held view in the philosophy of mind and philosophy of psychology, as well as a widely accepted view in biology, as we shall see. But it is important to bear in mind that there are some philosophers of science, including a number of philosophers of biology, who reject reductionism for other reasons. Many of them call themselves pluralists largely because they reject the suggestion that there is a single epistemic standard or methodology underlying science, especially one that requires strong consilience or even logical compatibility between disciplines and their claims. These pluralists emphasize the corrigibility and tentativeness of all scientific findings, and they urge that serious consideration of a large number of different, competing, and conflicting theoretical and experimental results is healthy. Thus, they reject physicalism as the reflection of unacceptable claims for the hegemony of results and methods characteristic of the physical sciences. Pluralism is committed to (tentatively) accepting the knowledge claims of the apparently irreducible findings, theories, and explanations they identify in biology. The train of their argument proceeds from their acceptance of one or another theory, model, regularity, or explanation in biology as well established, together with their claim that it is irreducible, to the intermediate conclusion that as philosophers we should endorse them as true or well warranted