The Material-Historical A priori in the Italian Critical Rationalism and Kuhn’s incommensurability thesis

According to the Italian critical rationalism and many contemporary au- thors, a material and historical conception of the a priori is not only properly to be described as “Kantian”, but is also capable of solving the problem of incommensurability between successive theories posed by the relativistic turn in the philosophy of science. But the differences between such a notion of the a priori and Kant’s a priori are deeper than their similarities. To say that such a priori may be called “Kantian” because it has the function of making experience possible include too many positions, and many well-established historical-hermeneutical distinctions would be lost in such identity claims. Under such a definition of the a priori, philosophers as different as Poincaré, Reichenbach, Lorenz, Wittgenstein, Popper and Kuhn, are to be called Kantian. Many authors would even turn out to be Kantian ante litteram, leading to a possible but coarse-grained a history of philosophy, in which too many important epistemological distinctions would be obscured. Moreover, this widely accepted conception of the a material and historical priori, in paradoxical opposition to the very fundamental intent for which it was developed, not only does not solve the problem of relativism, but constitutes one of its main roots, as can be seen through a reference to Kuhn’s paradigm: a material and historical a priori renews, at least in a theoretically fundamental sense, the same theoretical move that led from Kuhn’s concept of “paradigm” to the relativist conclusions of his incommensurability thesis.