Hartmann, Stephan

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11                                                 BOOK REVIEW1Cushing, James T., Philosophical Concepts in Physics. The Historical RelationBetween Philosophy and Scientific Theories, Cambridge University Press, 1998, xix +424 pp.This book successfully achieves to serve two different purposes. On the one hand, it isa readable physics-based introduction into the philosophy of science, written in aninformal and accessible style. The author, himself a professor of physics at theUniversity of Notre Dame and active in the philosophy of science for almost twentyyears, carefully develops his metatheoretical arguments on a solid basis provided byan extensive survey along the lines of the historical development of physics. On theother hand, this book supplies one long argument for Cushing´s own attitude in thephilosophy of science. While former studies of the author, from which this book drawsin part, focused each on one special episode in the history of science, this book gatherscase material from many different parts of physics and epochs. The main goal of thisbook is ”to impress upon the reader the essential and ineliminable role thatphilosophical considerations have played in the actual practice of science” (p. xv).The book is beautifully edited and produced; it contains a wealth of illustrative figures,well-chosen short quotations from original sources and contemporary commentators(some longer quotations are relegated in an appendix at the end of a chapter) and doesnot dispense with insightful mathematical arguments in the main text (some advanceddeductions are, however, relegated in the appendices). It contains nine parts, whereasonly the first and the last one are exclusively devoted to philosophical issues. Theseven remaining parts, each subdivided into three chapters, centre around one majorepisode (a theory, a world view, etc.) in the history of physics. The author presents thismaterial in a clear and philosophically unbiased way so that also readers who do notshare Cushing’s subsequent philosophical conclusions will find this inspiring bookextremely useful.Part 1 (”The scientific enterprise”) discusses some traditional (”objectivist”) viewsconcerning the status of scientific knowledge, ”the” scientific method, and the relation                                                           1 This review was published in Erkenntnis 52, 133-137 (2000).22between metaphysics and science. In this context, the relevant work of Aristotle, F.Bacon, R. Descartes, D. Hume, and - as a representative of our century - K. Popper isexamined and several methodological strategies (such as inductivism, the hypothetico-deductive method, and falsificationism) are introduced. All of these strategies seem toplay some role in the actual practice of science.Part 2 (”Ancient and modern models of the universe”) gives a careful account of someearly Greek cosmological considerations and of the Ptolemaic and Copernican modelof the universe in the light of the observational evidence of that time. Furthermore theonce highly influential ”impetus theory” and Galileis theory of motion is discussed.Cushing shows in detail why Galilei could never have performed his famous LeaningTower of Pisa experiment. This is one of several examples where Cushing points outwrong accounts of the history of physics in many physics textbooks. Other examplesfor this phenomenon, to be discussed in later chapters, are Planck’s work on the blackbody radiation, Bohrs’s original way to his atomic model, and Maxwell’s actualreasoning that lead him to postulate the existence of the displacement current.Part 3 (”The Newtonian universe”) introduces some of the arguments I. Newton’sdevelops in his influential treatise Principia. Cushing explains in detail what roleKepler’s laws played for the construction of Newton’s theory and, as an illustration,how the ocean tides can be explained with this theory.Part 4 (”A perspective”) presents the world view of Newtonian physics, elaborated byNewton’s successors. Special emphasis is given to an analysis of the concept ofdeterminism. Cushing shows how this concept emerged from a bold extrapolation ofan investigation of a few special force functions and the application of perturbationtheory for many body systems. Since modern chaos theory established thatdeterminism does not imply predictability, Cushing suggests that there is no way todecide if classical systems are deterministic or indeterministic. This interestingthought, of course, presupposes Cushing’s empiricist assumption that such decisionscan only be made on the basis of observations. This part also contains an informativediscussion of the well-known dispute between G. Galilei and the church. Cushingpoints out what role evidence as well as the different characters of the relevantdramatis personae and other social factors played in this conflict.Part 5 (”Mechanical versus electrodynamical world views”) presents a challenge forthe world view associated with Newtonian physics. Cushing discusses variousmechanical models of the electromagnetic aether and Maxwell’s theory. This part also33contains an illuminating analysis of data on the variation of the electron mass withvelocity in the light of rival theories of the electron obtained in experiments performedby W. Kaufmann in the first decade of this century. Cushing shows in detail how thehypotheses in question are embedded in a web of background assumptions andconcludes that ”the Kaufmann experiment [...] did not act as a definitive and deciding(`crucial´) experiment in the sense that a strict falsificationist view of science wouldlead one to expect” (p. 220). This kind of argument is a general feature of this book.Cushing establishes that a certain position in the philosophy of science that isessentially a result of logical considerations does not agree with the actual practice ofscience. Unfortunately, Cushing often presents only dummy positions that no oneholds any more (such as ”strict” falsificationism (p. 366) or certain criteria ofconfirmation (p. 369)). G. Andersson, for example, shows in his vigorous defence offalsificationism that episodes like the analysis of the Kaufmann experiment fit well inthis metatheoretical scheme (see G. Andersson, <English title etc.>, sec. 8.2).Part 6 (”The theory of relativity”) gives an overview of Einstein’s special and generaltheory of relativity. At the end of the chapter Cushing presents a world view based ongeneral relativity. Quite surprisingly, Cushing missed to mention in this context thecurrent discussion of determinism in general relativity and the recurrent theme of theunderdetermination of geometry by evidence. A discussion of these issues could havesupplemented his respective views developed in part 8.Part 7 (”The quantum world and the completeness of quantum mechanics”) providesan account of the development of quantum mechanics and a careful analysis of the roleof the famous inequalities first derived by J. Bell. Furthermore, this part contains alucid exposition of the measurement problem, the single big problem for manyinterpreters of quantum mechanics, and a reconstruction of the famous debate betweenN. Bohr and A. Einstein.Part 8 (”Some philosophical lessons from quantum mechanics”) continues thediscussion of quantum mechanics with an analysis of the EPR paper and theexposition of an alternative to the standard (”Copenhagen”) interpretation of quantummechanics. This alternative interpretation, first suggested by D. Bohm in 1952,supports a radically different ontology while, according to the author, beingempirically indistinguishable from the standard version. More specifically, Cushingargues that the Bohm theory uses the same formalism as the Copenhagen theory, butdiffers in the interpretation of this formalism. From this several conclusions are44drawn. Firstly, ”the best theory we have” is underdetermined by data. Secondly, thissituation implies that on the basis of observation alone, the choice betweendeterminism and indeterminism cannot be decided conclusively. Thirdly, thisdiagnosis raises a serious problem for the scientific realist, since observation does notrule out one of two ontologically quite different theories. If one accepts Cushing’sexposition, one may nevertheless wonder, if there aren’t any other (”soft”) criteria toidentify the ”true” theory. We shall come back to the role and status Cushing attributesto them later. One may, however, also doubt that both ”interpretations” (cf. M.Jammer’s usage of this term) are indeed empirically indistinguishable. After all,Bohm’s theory has an additional equation of motion for the particles’ trajectories thatmay eventually produce new empirical consequences. In this case, Cushing wouldhave lost his main argument for actual underdetermination in science and againstscientific realism. It should be noted, however, that Cushing does not primarily intendto defend an elaborated philosophical position in this book. Nevertheless, severalpositive claims can be identified (see Part 9):1. Science is a ”coupled network” of practice, methods, and goals. None of theselevels is immune to change, ”either in principle or in fact” (372 f). This means, forexample, that there is no fixed methodology (such as Popper’s). In fact, scientistshappen to be opportunists; in order to solve scientific problems they are willing toprovisionally accept any philosophical (or whatsoever) position or methodologythat might help.2. The development of scientific theories is, like any other cultural activity,accompanied by the occurrence of historically contingent factors. By telling afascinating story of counterfactual history, Cushing shows that the development ofmodern physical theory (quantum theory) could well have developed quitedifferently. This demonstrates that (at least one) important scientific theory is infact underdetermined by data.3. In order to select one theory over another, scientists have to apply soft criteria,such as simplicity. These criteria, however, have some uneliminable subjectivecomponent and are therefore not suited to identify the ”true” theory. The only realcriteria are the ”hard” ones: empirical adequacy and logical consistency. But theydo not uniquely determine the wanted theory.Another important weak criterion for theory selection is understandability. This conceptis notoriously hard to explicate. Cushing criticises the `standard view´ that55understanding can be equated with unification or reduction. He maintains thatunderstanding has also something to do with visualizability and the existence of a causalstory. The discussion of the EPR-correlations shows that scientists are not completelysatisfied with theories that are empirically adequate and provide formal explanations,but do not produce any real understanding whatsoever. The Copenhagen-Bohm caseshows, however, that understandable theories (such as the Bohm theory) are not alwayspreferred.At least as noticeable as these positive claims is way of doing philosophy of scienceCushing implicitly suggests and demonstrates in this book. The author supports anaturalistic and interdisciplinary approach to science, history, and philosophy (”ittakes a lot of history of science to anchor even a little philosophy of science” (xv)). Hepoints out, for example, that it does not suffice to restrict oneself to the business ofreconstructing already successful theories (”Whig-history”). Philosophers of sciencehave to go beyond the textbook level and examine the whole (philosophical, historical,sociological, etc.) culture in which theories are constructed. This approach isdescriptive, not prescriptive. Cushing has shown that it nevertheless leads tointeresting insights. For good reasons Cushing does not provide another overallphilosophical account of science, but he does a lot to increase our understanding ofwhat science is and how it really functions.  Stephan Hartmann

Review of J. Cushing: Philosophical Concepts in Physics

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