Incommensurability and Theory Change

The paper explores the relativistic implications of the thesis of incommensurability. A semantic form of incommensurability due to semantic variation between theories is distinguished from a methodological form due to variation in methodological standards between theories. Two responses to the thesis of semantic incommensurability are dealt with: the first challenges the idea of untranslatability to which semantic incommensurability gives rise; the second holds that relations of referential continuity eliminate semantic incommensurability. It is then argued that methodological incommensurability poses little risk to the rationality or objectivity of science. For rational theory choice need neither be dictated by an algorithm nor governed by a binding set of rules. The upshot of the discussion is deflationary. There is little prospect for a relativistic conception of science based on inflated claims about the incommensurability of scientific theories.