Abstract

In his 1920 monograph Relativitätstheorie und Erkenntnis apriori the young Reichenbach distinguished between two meanings of the a priori: ‚apodictically valid, true for all time‘ and ‚constituting the concept of object‘. At the end of the 1990s Michael Friedman drew again the attention of philosophers of science to this forgotten distinction. In the spirit of Reichenbach’s early Kantianism Friedman attempted to construct a relativized or temporally variable a priori, which is nevertheless constitutive of the object of knowledge. Friedman rejects an alternative historicized version of the a priori elaborated by the Marburg school and in particular by Cassirer. According to Friedman, Cassirer defended a regulative, but absolute version of the a priori, the existence of a yet-to-be-found set of final principles that are conditions of all scientific experience. This paper suggests that using the constitutive/regulative distinction as a basis for comparison is misleading. In order to understand the Marburg school’s conception of the a priori one should get back to Hermann Cohen’s interpretation of Kant and in particular to his own distinction between two meanings of the a priori. A more suitable comparison is that between Cohen’s opposition metaphysical-vs.-transcendental a priori and Reichenbach’s distinction apodictic-vs.-constitutive a priori. If the comparison is conducted along these lines—as already suggested in the mid-1920 s by the Dutch neo-Kantian Alfred C. Elsbach—it turns out that Cohen and the Marburg school and not Reichenbach provided a good example of a relativized a priori.