Kuhn’s Incommensurability Thesis: What’s the Argument?

Abstract

In this paper, I argue that there is neither valid deductive support nor strong inductive support for Kuhn’s incommensurability thesis. There is no valid deductive support for Kuhn’s incommensurability thesis because, from the fact that the reference of the same kind terms changes or discontinues from one theoretical framework to another, it does not necessarily follow that these two theoretical frameworks are taxonomically incommensurable. There is no strong inductive support for Kuhn’s incommensurability thesis, since there are rebutting defeaters against it in the form of episodes from the history of science that do not exhibit discontinuity and replacement, as Kuhn’s incommensurability thesis predicts, but rather continuity and supplementation. If this is correct, then there are no compelling epistemic reasons to believe that Kuhn’s incommensurability thesis is true or probable.

Keywords:

• Incommensurability
• Lexical Taxonomy
• Scientific Change
• Scientific Revolution
• Thomas Kuhn

Acknowledgments

An earlier version of this paper was presented at “Kuhn’s The Structure of Scientific Revolutions: 50 Years On” conference on 1 December 2012 at The College of New Jersey. I would like to thank Pierre Le Morvan, the audience, and Philip Kitcher for constructive feedback. I am also grateful to two anonymous reviewers of Social Epistemology for helpful comments on earlier drafts.

Notes

1 Another version of the incommensurability thesis was proposed by Feyerabend (1962) around the same time. As Sankey (2009, p. 196) notes, however, “It is widely recognized that Kuhn and Feyerabend did not mean the same thing when they originally spoke of the incommensurability of competing theories.” For the purposes of this paper, I focus on Kuhn’s version of the incommensurability thesis.

2 On TI as a special kind of conceptual incompatibility in terms of lexical taxonomies, see Kuhn (2000, pp. 14–5) and the introduction to Sankey and Hoyningen-Huene (2001).

3 For yet another notion of incommensurability, see Bird (2007, pp. 21–39).

4 See e.g. Sankey (1994) and the essays collected in Sankey and Hoyningen-Huene (2001).

5 For recent examples, see the “special issue of Social Epistemology [vol. 17, issue 2–3, 2003] devoted to critical comments on Fuller’s study of the philosophy of Thomas S. Kuhn and its context” (Gattei 2003, p. 89).

6 By “valid deductive argument,” I mean an argument whose premises, if true, necessitate the truth of the conclusion. An invalid argument, then, is an argument whose premises, even if true, do not necessitate the truth of the conclusion.

7 By “strong inductive argument,” I mean an argument whose premises, if true, make the truth of the conclusion more likely, but not guaranteed. A weak argument, then, is an argument whose premises, even if true, do not make the conclusion more probable.

8 On semantic incommensurability and variation of sense, see Sankey (2009, p. 197).

9 Cf. Stillwaggon Swan and Bruce (2011, pp. 341–3).

10 (C2) seems false as a general claim about conceptual schemes as well. On paradigms as conceptual schemes, see Henderson (1994, p. 174). See also Putnam (1981, p. 114). Cf. Feyerabend (1987, pp. 75–81).

11 Cf. Dupré’s (1981) “lily” example. Note that although “lily” refers to one thing in plant taxonomy and to another thing in ordinary language, it also refers to both in these conceptual frameworks, which is why there is no conceptual incompatibility, and hence no TI, in this case (Dupré 1981, p. 74). Similarly, although “kid” refers to a young goat in animal taxonomy and to a child in ordinary language or folk taxonomy, it also refers to both in these conceptual frameworks, which is why there is no conceptual incompatibility, and hence no TI, in this case, either.

12 See Sankey (2009, p. 197) on semantic incommensurability and discontinuity of reference.

13 See footnote 10.

14 On the phlogiston-oxygen episode, see also Kitcher (1978) who argues that “dephlogisticated air” genuinely referred to samples of oxygen.

15 Cf. Sankey (2009). According to Sankey (2009, p. 198), “the threat of wholesale referential discontinuity between theories has been removed by rejecting the description theory of reference.” That is, if “reference is independent of description,” then “successive theories are not incommensurable due to discontinuity of reference” (Sankey 2009, p. 198).

16 These are Friedman’s (2001, p. 71) examples.

17 Another episode from the history of science that runs contrary to (TI) is the scientific change from Wegener’s theory of continental drift to plate tectonics.

18 Just as it would be hasty to conclude from a few episodes that incommensurability is typical of scientific change, it would also be hasty to conclude from a few episodes that incommensurability is atypical of scientific change.

19 Given what I mean by deductive and inductive arguments, any non-deductive form of inference is covered by “inductive” for the purposes of this paper, except abduction or Inference to the Best Explanation. I think it is safe to assume that incommensurability is not supposed to be the best explanation for scientific change, since (TI) is supposed to be a mark of scientific change, not an explanation for scientific change. Moreover, it is not clear what, if any, novel predictions (TI) makes. Cf. Mizrahi (2012).

20 By “general thesis,” I mean a thesis that holds true of most—though not all—cases. So, if (TI) is not a general thesis, then it does not hold true even of most episodes of scientific change. This would be a problem, of course, if the argument for (TI) is supposed to be an inductive generalization.

21 See Kuhn (1962, p. 103). Cf. Bird (2012).

22 Though see Sankey (1993). Since (TI) is an integral part of Kuhn’s theory of scientific revolutions, and that theory is supposed to be a general account of scientific change, it follows that (TI) is supposed to hold generally, too.

23 I use “pragmatic” and “acceptance” in the constructive empiricist’s sense. On “acceptance,” see van Fraassen (1980, p. 88). On the distinction between epistemic and non-epistemic (or pragmatic) values in theory choice, see van Fraassen (2007, p. 340).

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Moti Mizrahi

Moti Mizrahi is an assistant professor in the Philosophy Department at St. John's University. He works in argumentation, epistemology, metaphilosophy, and philosophy of science. His recent publications include “Does Conceivability Entail Metaphysical Possibility?” (with David R. Morrow, Ratio, forthcoming), “Constructive Empiricism: Normative or Descriptive?” (International Journal of Philosophical Studies, forthcoming), and “The Argument from Underconsideration and Relative Realism” (International Studies in the Philosophy of Science, forthcoming).