Subjective Views of Kuhn

Subjective Views of Kuhn Peter Achinstein Johns Hopkins University In response to a charge of subjectivism, Kuhn in his Postscript emphasizes the importance of “values” (accuracy, simplicity, explanatory power, etc) that are shared by scientists generally. However, Kuhn adds, these values are applied differently by different scientists. By employing a comparison with partially subjective views of Carnap on conªrming evidence, this paper raises questions about Kuhn’s position on values by considering ways it might be interpreted as subjective and ways it may not. Many philosophers of science have wrestled with the question of whether there is a universal scientiªc method, i.e., a set of rules for discovering or testing scientiªc hypotheses. The rules are universal because they hold for all sciences and all times. Examples might include rules of the sort that Descartes proposed (his 21 rules) in Rules for the Direction of the Mind, or the 4 rules of reasoning that begin the third book of Newton’s Principia. Two major ªgures in 20th century philosophy of science, Karl Popper and Paul Feyerabend, whose deaths occurred within a year or two of Kuhn’s, offered strikingly different answers to the question of whether universal rules exist. Popper’s answer I take to be a resounding, “Yes,” at least to the question of whether there are such rules in the case of scientiªc testing or justiªcation. (Rules of discovery, he believed, are another matter.) Popper’s method of corroboration—his version of hypothetico- deductivism—is, I believe, intended to be a universal scientiªc method for testing hypotheses. Feyerabend, although a student of Popper, offered a very different answer: There are no universal rules of discovery or testing. Doing science, Feyerabend said in one of his typically provocative moments, is like mak- ing love or waging war. There are some useful hints, some rules of thumb, Perspectives on Science 2001, vol. 9, no. 4 ©2002 by The Massachusetts Institute of Technology 423 Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/106361401760375811 by guest on 30 September 2021 424 Subjective Views of Kuhn but in general, to quote his most notorious principle, “anything goes.” Anarchism, while it may not be a workable political strategy, yields the best science, and is the best philosophy of science, he used to say. With Popper on the extreme right and Feyerabend on the extreme left, where does Kuhn ªt on this spectrum? One might be tempted to say that Kuhn acknowledges the existence of methodological rules, but they are not universal. They are paradigm-speciªc. The paradigm supplies rather speciªc rules for what sort of hypotheses are worth testing, e.g., ones that do not violate conservation of energy, or that do not postulate action at a distance or velocities greater than that of light. And the paradigm supplies speciªc rules for how to test such hypotheses. On the other hand, in his Postscript written for the second edition of The Structure of Scientiªc Revolutions, Kuhn emphasizes the importance of what he calls scientiªc values as an essential part of the “disciplinary matrix,” a term that replaces “paradigm” (Kuhn 1970a, p. 182ff.). Kuhn mentions values such as accuracy, consistency, scope, simplicity, fruitfulness, explanatory power, and plausibility. These are values employed in determining what theory or hypothesis to accept, or to promote, or at least to take seri- ously and explore. There are passages in Kuhn suggesting that these values are shared by very different scientiªc communities, that they are shared over time, and indeed that this is the reason why all scientists can, in an important sense, be thought of as forming a single community (Kuhn 1970a, “Postscript,” p. 184). So is Kuhn here allied with Popper? Is he a universalist? I don’t think so. Nor is he an anarchist either. Instead, he is delightfully paradoxical. He speaks of values shared within a scientiªc community and shared even by different communities. But he also says that these shared values are frequently applied differently even by scientists within the same community. Although the criterion of “accuracy” is pretty stable from one application to another, “judgments of simplicity, consistency, plausibility, and so on often vary greatly from individual to individual” (Kuhn 1970a, “Postscript,” p. 185). “In short,” Kuhn writes, “though values are widely shared by scientists and though commitment to them is both deep and constitutive of science, the application of values is sometimes considerably affected by the features of individual personality and biography that dif- ferentiate the members of the group” (Kuhn 1970a, p. 185). So while you and I may both agree that the simplest hypothesis is to be preferred, pro- moted, tested ªrst, or whatever, we may disagree substantially over what counts as simple. And this disagreement, I take it, may be unresolvable by argumentation, but only explainable by reference to causal features of temperament, training, and so forth. Moreover, to complicate matters fur- ther, in determining which of two theories to prefer, promote, or pursue, Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/106361401760375811 by guest on 30 September 2021 Perspectives on Science 425 it may turn out that each has some virtues the other lacks, and that scientists, even from the same community, weight these virtues differently. Kuhn emphasizes that the criteria for selecting theories “function not as rules, which determine choice, but as values which inºuence them” (Kuhn 1977, p. 331). The idea seems to be that rules, at least if clearly for- mulated, are, or are supposed to be, applied by different people in the same way under the same circumstances. It wouldn’t do if the rule that you must stop your car at a red light could be interpreted by different people in a very different manner. But for Kuhn, values can be variably applied, and that is ªne and dandy. Moreover, Kuhn thinks this is sufªcient to avoid the charge of subjectivity levelled against him by a number of critics. Responding to Schefºer, e.g., Kuhn writes, “it is emphatically not my view that ‘adoption of a new scientiªc theory is an intuitive or mysti- cal affair, a matter for psychological description rather than logical or methodological codiªcation’” (Kuhn 1970b, “Reºections on My Critics,” p. 261). Kuhn insists that there are good reasons for adopting one theory over another, and these reasons are of the sort philosophers of science typically describe involving accuracy, scope, simplicity, explanatory power, and so on. So where does Kuhn end up on the spectrum between Popper, the universalist, and Feyerabend, the anarchist. Like Popper, he wants to promote certain values common to scientists generally, from one period to another. He wants to say that scientists generally favor theories satisfying these values. Appeals to these values constitute good reasons for preferring the theories. And it is the acceptance of such values that is at least part of what it is to be a scientist. Like Feyerabend, however, he wants to reject the idea that scientists proceed in accordance with some ªxed and universal set of rules which determine what hypothesis it is reasonable to accept. Let me put this another way which may be more helpful. All three of the philosophers I have mentioned talk about values such as simplicity, consistency, explanatory power, and empirical conªrmation (even though Feyerabend at one point calls them “verbal ornaments”). Now there are several views about such values. On one, there are objective rational constraints on how they are to be interpreted and applied in particular circumstances. On another, opposing view, there are no objective rational constraints. What one takes to be simple, consistent, explanatory, or conªrmatory, is a personal matter, or perhaps is decided by voting or power politics. I will attribute that view to Feyerabend, at least in his more provocative moments. As for the rational constraint view, I see two versions: one is a strict constraint view. This is the idea that how a value is applied is strictly con- strained by usage, or deªnition, or practice, so that in accordance with this Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/106361401760375811 by guest on 30 September 2021 426 Subjective Views of Kuhn usage or deªnition or practice, although there might be borderline cases, what counts, or is to count, as simple, consistent, explanatory, or empiri- cally conªrmed, is quite generally determined in individual applications. I think that is Popper’s view, or something close to it. The second rational constraint view is weaker. It is that usage or deªnition or practice furnish at least some constraints on how scientiªc values are to be interpreted and applied. Not just any theory a scientist or a community calls simple or conªrmed is really so. But these constraints, however universal, do not completely determine how scientiªc values are to be interpreted and applied. Scientists associated with the same practice can still differ considerably over whether, or to what extent, some theory is simple, conªrmed, explanatory, etc. I suspect this weak constraint view is Kuhn’s view, or something close to it. If this is Kuhn’s view, there is an interesting similarity between this and the view of someone most people take to be one of Kuhn’s major op- ponents, viz. Rudolf Carnap, the arch-logical positivist. In his Continuum of Inductive Methods published in 1952, 10 years before Kuhn’s most fa- mous work, Carnap sought to explicate the idea of the degree to which a theory is conªrmed or supported by the evidence. He began by setting down all the objective, rational, universal constraints he could think of for this concept, resulting in 11 axioms.

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