Truth and Historicism in Kuhn’s Thesis of Methodological Incommensurability

Methodological incommensurability is a Thomas Kuhn’s thesis affirming that there are not shared, objective methodological rules or neutral scientific standards for theory comparison and choice. This thesis has often been interpreted as a relativistic and irrationalist claim on the incomparability of scientific theories. Since every paradigm refers to its standards, problem-field and aims, theory choice is subjective and arbitrary. Moreover it seems that, in his latest works, Kuhn abandons this aspect of incommensurability to focus on semantic incommensurability. On the contrary I will argue against the interpretation of methodological incommensurability as a source of epistemological relativism. The relativistic feature of incommensurability, rather, must be looked for in Kuhn’s skepticism on the concept of truth as correspondence. From this point of view methodological incommensurability is consistent with semantic incommensurability, because they are both rooted in the intra-theoretical nature of truth. According to Kuhn, incommensurability and truth are historical concepts. The rational explanation of scientific conviction change cannot aim to something above the historical situation and the concrete scientific practice (such as the correspondence between theory and reality): truth is not correspondence, but an historical function of scientific community’s agreement. We can evaluate theories’ respective accuracy, fruitfulness, consistency, scope, simplicity and made a rational decision; but none of these parameters can measure theory’s likeness to truth. Theory choice is always a theory-theory match, not a theory-reality match.