an introduction to the philosophy of science ........................................................... SCIENCE AND ITS CONCEPTUAL FOUNDATIONS A SERIES EDITED BY DAVID L. HULL THEORY AND REALITY ........................................................... Peter Godfrey-Smith is associate professor of philosophy and of his­ tory and philosophy of science at Stanford University. He is the author PETER GODFREY-SMITH of Complexity and the Function ofMind in Nature. The University of Chicago Press, Chicago 60637 The University of Chicago Press, Ltd., London © 2003 by The University of Chicago All rights reserved. Published 2003 Printed in the United States of America 12 II 100908 45 ISBN: 0-226-30062-5 (cloth) ISBN: 0-226-30063-3 (paper) Library of Congress Cataloging-in-Publication Data Godfrey-Smith, Peter. Theory and reality: an introduction to the philosophy of science I Peter Godfrey-Smith. p. cm. - (Science and its conceptual foundations) Includes bibliographical references and index. ISBN 0-226-30062-5 (alk. paper) - ISBN 0-226-30063-3 (pbk. : alk. The University of Chicago Press / Chicago and London paper) I. Science-Philosophy. I. Title. II. Series. QI75 .G596 2003 501-dc2I 2002155305 @ The paper used in this publication meets the minimum requirements of the American National Standard for Information Sciences-Perma­ nence of Paper for Printed Library Materials, ANSI Z39.48-1992. 74 Chapter Four related to squid. This would have been a disaster for evolutionary theory, one of almost the same magnitude as the Precambrian rabbit. As it happened, the DNA data suggest that humans and chimps di­ verged about 4.6-5 million years ago and that chimps or pigmy chimps (bonobos) are our nearest living relatives. Prior to the DNA data, it was unclear whether humans were more closely related to chimps or to goril­ 5 las, and the date for the chimp-human divergence was much less clear. That is how the grand test ofour old pre-molecular family tree has tended to go. Kuhn and NormaL Science There have been no huge surprises but lots of new facts and a lot of ad­ justments to the previous picture. 5.1 "The Paradigm Has Shifted" Further Reading In this chapter we encounter the most famous book about science written Popper's most famous work is his book The Logic ofScientific Discovery, published during the twentieth century-The Structure ofScientific Revolutions, by in German in 1935 and in English in 1959. The book is mostly very readable. Chap­ Thomas Kuhn. Kuhn's book was first published in 1962, and its impact ters 1-5 and 10 are the key ones. For the issues in section 4.4 above, see chapter 5 was enormous. Just about everything written about science by philoso­ of Popper; for section 4.5, see chapter 10. A quicker and very useful introduction phers, historians, and sociologists since then has been influenced by it. The to Popper's ideas is the paper "Science: Conjectures and Refutations" in his collec­ book has also been hotly debated by scientists themselves. But Structure (as tion Conjectures and Refutations (1963). the book is known) has not only influenced these academic disciplines; Newton-Smith, The Rationality ofScience (1981), contains a clear and detailed many of Kuhn's ideas and terms have made their way into areas like poli­ assessment of Popper's ideas. It includes a simplified presentation of some of the tics and business as well. technical issues surrounding corroboration that I omitted here. Salmon 1981 is an A common way of describing the importance of Kuhn's book is to say exceptionally good critical discussion of Popper's views on induction and predic­ that he shattered traditional myths about.science, especially empiricist tion. See also Putnam 1974. Schilpp (1974) collects many critical essays on Popper, myths. Kuhn showed, on this view, that actual scientific behavior has little with Sir Karl's replies. to do with traditional philosophical theories of rationality and knowledge. Popper's influence on biologists and his (often peculiar) ideas about evolution­ There is some truth in this interpretation, but it is often greatly exag­ ary theory are discussed in Hull 1999. Horgan's book The End ofScience (1996) gerated. Kuhn spent much of his time after Structure trying to distance contains a very entertaining interview with Popper. himself from some of the radical views ofscience that came after him, even though he was revered by the radicals. And the connection between Kuhn's views and logical empiricism is actually quite complicated. For example, it comes as a surprise to many to learn that Kuhn's book was published in a series organized and edited by the logical empiricists; Structure was pub­ lished as part of their International Encyclopedia of Unified Science series. As a matter of historical fact, though, there is no denying that this was something of a "Trojan horse" situation. Logical empiricism was widely perceived as being seriously damaged by Kuhn. I said above that some of Kuhn's ideas and terms have made their way into areas far from the philosophy of science. The best example is Kuhn's use ofthe term "paradigm." Here is a passage from Tom Wolfe's 1998 novel, 75 76 Chapter Five Kuhn and Normal Science 77 A Man in Full. Charlie Croker, a real estate developer who has debt prob­ 5.2 Paradigms: A Closer Look lems, is talking with his financial adviser, Wismer ("Wiz") Stroock. A moment ago I said that a paradigm in Kuhn's theory is a package of "I'm afraid that's a sunk cost, Charlie," said Wismer Stroock. '~t this point the claims about the world, methods for gathering and analyzing data, and whole paradigm has shifted." habits of scientific thought and action. However, it is more accurate to say Charlie started to remonstrate. Most of the Wiz's lingo he could put up with, that this is one sense in which Kuhn used the term "paradigm." In Struc­ even a "sunk cost." But this word "paradigm" absolutely drove him up the wall, so ture, the term is used in several different ways; one critic counted as many much so that he had complained to the Wiz about it. The damned word meant noth­ as twenty-one different senses (Masterman 1970). Kuhn later agreed that ing at all, near as he could make out, and yet it was always "shifting," whatever it he had used the word ambiguously, and throughout his career he kept fine­ was. In fact, that was the only thing the "paradigm" ever seemed to do. It only tuning this and other key concepts. To keep things simple, though, in this shifted. But he didn't have enough energy for another discussion with Wismer book I will recognize two different senses of the term "paradigm." Stroock about technogeekspeak. So all he said was: The first sense, which I will call the broad sense, is the one I described "OK, the paradigm has shifted. Which means what?" (71) above. Here, a paradigm is a package of ideas and methods, which, when . combined, make up both a view of the world and a way of doing science. This sort oftalk derives completely from Kuhn. But what is a paradigm? When I say "paradigm" in this book without adding "broad" or "narrow;' The short answer is that a paradigm, in Kuhn's theory, is a whole way of I mean this broad sense. But there is also a narrower sense. According to doing science, in some particular field. It is a package of claims about the Kuhn, one key part of a paradigm in the broad sense is a specific achieve­ world, methods for gathering and analyzing data, and habits of scientific ment, or an exemplar. This achievement might be a strikingly successful ex­ thought and action. In Kuhn's theory ofscience, the big changes in how sci­ periment, such as Mendel's experiments with peas, which eventually be­ entists see the world-the "revolutions" that science undergoes every now came the basis of modern genetics. It might be the formulation of a set of and then-occur when one paradigm replaces another. Kuhn argued that equations or laws, such as Newton's laws of motion or Maxwell's equations observational data and logic alone cannot force scientists to move from describing electromagnetism. Whatever it is, this achievement is a source one paradigm to another, because different paradigms often include within ofinspiration to others; it suggests a way to investigate the world. Kuhn of­ them different rules for treating data and assessing theories. Some people ten used the term "paradigm" just for a specific achievement of this kind. have interpreted Kuhn as claiming that changes between paradigms are I will call these achievements paradigms in the narrow sense. So paradigms completely irrational, but Kuhn definitely did not believe that. Instead, in the broad sense (whole ways of doing science) include within them par­ Kuhn had a complicated and subtle view about the roles of observation adigms in the narrow sense (examples that serve as models, inspiring and and logic in scientific change. directing further work). Kuhn himself did not use this "narrow/broad" ter­ In a passage like the Tom Wolfe one above, "paradigm" is used in a minology, but it is helpful. When Kuhn first introduced the term "para­ looser way derived from its role in Kuhn's theory of science. A paradigm in digm" in Structure, he defined it in the narrower sense. But in much of his this sense means something like a way of seeing the world and interacting writing, and in most of the work written after Structure using the term, the with it. broad sense is intended. Kuhn did not invent the word "paradigm;' It was an established term, Kuhn used the phrase "normal science" for scientific work that occurs which meant (roughly) an illustrative example of something, on which within the framework provided by a paradigm.