Kuhn and Salmon on Rationality and Theory Choice

Kuhn and Salmon on Rationality and Theory Choice Carl G. Hempel The Journal of Philosophy, Vol. 80, No. 10, Part 1: Eightieth Annual Meeting of the American Philosophical Association, Eastern Division. (Oct., 1983), pp. 570-572. Stable URL: http://links.jstor.org/sici?sici=0022-362X%28198310%2980%3A10%3C570%3AKASORA%3E2.0.CO%3B2-K The Journal of Philosophy is currently published by Journal of Philosophy, Inc..

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rience, and asks why that should be the case. It asks, that is, not for a justification of learning from experience, but for an explanation of the viability of the whole language game that involves 'induction' and underpins the form of life we live. T o that question I attempt n o answer, but I would like one. Together with most of you, I share Hume's itch. Preparing this paper has made me realize that the itch may be intrinsic to the game, but I am not ready for that conclusion. THOMAS S. KUHN

Massachusetts Institute of Technology KUHN AND SALMON O N RATIONALITY AND

THEORY CHOICEt

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AGREE with Salmon's view that philosophical questions about the rationality of science demand close attention to the structure of scientific confirmation or of theory appraisal, and that a simple hypothetico-deductive construal affords n o adequate general explication of confirmation. But I have doubts concerning his program for a probabilistic account of theory appraisal along Bayesian lines. How are the pertinent. probabilities to be understood? Salmon acknowledges that theory choice is affected not only by empirical evidence, but also by factors like Kuhn's desiderata, and he suggests that the probabilities might be given a reasonably clear and objective interpretation by reference to serious judgments made by scientists. T h e prospect is most attractive, but-I fear-too highly idealized to permit a sufficiently close fit with scientific practice. Salmon suggests that close attention to the structure of inductive reasoning is needed to determine whether the existence of unobservable entities can be "inferred" from observable evidence. But Bayesian reasoning from observed clinical symptoms to a surgically observable coronary occlusion has, I think, the same structure as a Bayesian inference from an observed track pattern in a cloud chamber to a certain "unobservable" subatomic event. In either case, the inferred probability of the hypothesis h depends on observational data i and on background information e, which jointly provide some basis for determining the requisite prior and poste*Abstract of a paper to be delivered in an APA symposium on The Philosophy of C. G . Hempel, December 28, 1983, responding to papers by Wesley C . Salmon and Thomas S. Kuhn; see this JOI.RNAL, this issue, 555-562 and 563-570, respectively.

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rior probabilities. In the second example, e would have to contain suitable theoretical assumptions about subatomic events and their manifestations. Thus, the admissibility of talk about unobservable entities must be settled when choosing the language in which i, e, and h are expressed-prior to any application of inductive logic. A minor question: Is Kuhn's comparative conception of theory appraisal actually illuminated by the Bayesian formula (3), where the compared alternatives form an exhaustive set? No exhaustive set of significant alternatives is available in a comparative evaluation of large-scale theories like Newton's and Einstein's. Kuhn argues that statements claiming rationality for certain criteria used in scientific theory appraisal possess a kind of necessity that he finds clearly exhibited by the constitutive laws of scientific theories, e.g., by Newton's Second Law. By way of elaboration, he remarks that the Newtonian terms 'mass' and 'force' can be acquired only by reference to the Second Law, and that alteration of the Law would destructively alter the entire system of natural kinds and connections by which Newton's language seeks to order the world. But rather similar claims might be made also for what Kuhn calls "contingent generalizations," like Hooke's law: they mediate the application of the Second Law to nature and have to be acquired in learning the use of 'mass' and 'force'. And alteration of contingent laws also requires further-though perhaps less severe-changes in the theoretical network. Kuhn's categorial distinction seems to reflect a difference in degree. Conceptions of this kind have resisted various attempts at more specific explication. Perhaps Kuhn would argue that, like his notion of desiderata, his distinction is fruitful even though it admits of no precise explication. Kuhn argues analogically that such features as learning from experience, insistence on consistency, adherence to the desiderata for theory choice, and, in consequence, rationality, are necessary characteristics of science, relative to the language we use in categorizing and interrelating diverse disciplines. T h e basic pragmatism of this view is, I believe, very illuminating. Kuhn's construal presupposes, however, the availability of a widely shared language-cum-theory about science-a dubious assumption, considering the conflicting conceptions of science in vogue today. Are we to call the attribution of rationality to science necessary in Kuhn's language, contingent and false in Feyerabend's? Which language is to count here? T h e question calls for a critical comparison of competing theories, and there are pertinent consid-

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erations that can be, and have been, invoked in this context. Whatever threat of infinite regress or circularity may seem to loom here is unavoidable: there cannot, of course, be a definitive, unconditional justification. CARL G. HEMPEL

University of Pittsburgh

T H E INDEPENDENCE OF INTELLECTUALS"

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HERE are material preconditions for intellectual independence. This is not to deny that we can denounce our oppressors with our dying breaths. It is to recognize that to develop independent positions we must have access to the material resources with which to sustain life at a n adequate level. I. ASSUMPTIONS

I begin with the assumption that in ordinary times intellectuals must earn a living. Certainly there are intellectuals who on occasion rise above this need. They do so especially in dramatic bursts of determination. In rare instances, such bursts extend over much of a lifetime, if someone else-a friend, or spouse, or backer-picks u p the overdue bills. But especially when there are children to feed and n o inclination or chance to unload the responsibility, the need to earn a living returns to rein in cultural or intellectual adventurers. Even intellectuals are dependent, then, on sufficient social support to allow them to sustain themselves. But what is social support? T h e myths by which we are surrounded suggest that the citizen who "earns" his salary or fee in the "free market" and receives n o payments from "government" or "the public sector" receives n o "social support." These delusions are convenient to some, damaging to others. There would be n o Robinson Crusoe-like men accumulating possessions on intellectual islands without strong social ties at least between such men and the mothering persons who took care of the children they once were. And so we come into the real world with social ties attached. But by the time we are "earn* T o be presented in an APA symposium o n T h e Social Responsibility of Intellectuals, December 28, 1983. Richard Rorty will be co-symposiast, and Alasdair MacIntyre will comment, see this JOI'RNAL, this issue, 583-589 and 590-591, respectively, for their contributions. I a m grateful to Charles Landesman, Amelie Rorty, and Robert L. Thompson for helpful comments o n a draft of this paper.

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