The Relative Necessity of the Kantian A Priori: ErnstCassirer and Hans Reichenbach

The Relative Necessity of the Kantian A Priori: ErnstCassirer and Hans Reichenbach

Francesca Biagioli

Much of the scholarship on the relativization of the a priori has taken its starting point fromthe way in which Reichenbach, inTheTheory of Relativity and A Priori Knowledge(1920),accounts for the possibility of varying the coordinating principleslinking abstractmathematical structures to empirical reality. Such are the principles that Reichenbach calleda priori in the sense of constitutive of the objects of experience but no longer valid for alltime as Kant thought. However, this poses the problem of distinguishing the relativization ofthe Kantian a priori from conventionalism. This paper aims to reconsider this issue in the example of Cassirer´s  and Reichenbach´s discussions of the apriority of geometry. Aftercomparing their views concerningthe revisability of the Kantian a priori, it will be arguedthat both attempts to address the status of geometry with regard to the general theory ofrelativity lead to a relativization of a priori knowledge in a different sense than the standardone, that is, as involving different, but interrelated, levels of constitutivity.