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A defence of Kuhn's incommensurability thesis Kosub, Timothy Alexander


Kuhn's incommensurability thesis is the claim that successive scientific theories often conflict not only logically but also normatively: i.e. they differ both about nature and also about the use of common apparatus, concepts and experimental results, and what are proper scientific goals and methods. Critics commonly object that Kuhn's thesis attacks such traditional scientific values as objectivity and rationality. But their strongest response can be expressed as a dilemma: either, if taken literally, the incommensurability thesis is self-contradictory; or, if that literal reading is rejected, this thesis has no philosophical Import. Kuhn claims his critics have misinterpreted his thesis and he maintains both its intelligibility and relevance. The problem is whether his position can be sustained. In support of Kuhn, I argue that his critics' reading of his thesis is based on a mistaken Identification of logic with formal logic and, more generally, of comparability with commensurabil-lty. I argue that logical comparison of theories that lack common concepts is possible if one can compare theories directly, as whole to whole, and that such direct logical comparison is actually commonplace in natural languages. I also argue more generally that Kuhn's critics' identification of comparison with com-mensuration leads to a vicious regress. My attempt at resolving the dispute between Kuhn and his critics is informed by a simple "hermeneutic" principle: If one view seems either unintelligible or irrelevant to the other, then both sides probably disagree on the Interpretation of shared concepts. Once the focus of the dispute is located, arguments can often be given for preferring one interpretation over another. Thus if I am right that Kuhn's critics' view wrongly equates comparability with commensurability and logic with formal logic, that view clearly must be replaced by one that distinguishes them. I argue that if those distinctions are made, incommensurability can be seen to represent no essential threat to scientific rationality and objectivity. In this light, I suggest Kuhn's major analytic concepts be viewed as Improvements on more traditional notions drawn from formal logic. I also use a historical case study of the original discovery of geometrical incommensurability to illustrate further Kuhn's concepts and to develop a more general notion of a proof of incommensurability that is applicable to scientific theories.

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