Abstract
The problem of the unity of Kant’s critical philosophy has inspired the development of German idealism from the beginning. This paper discusses the problem of the unity of theoretical and practical philosophy as the problem of an original unity that precedes Kant’s legislation of nature and freedom. Whereas from the perspective of the post-Kantian German idealists, a concept that conceives of such an original and overarchingunity as freedom seems to fail in Kant, it is my thesis that within his conception of activity, Kant indeed offers a distinction for constructing such a concept. Unfortunately, Kant’s distinction remains rather implicit in his philosophy: the distinction between activity qua performance of validity, and hence the subject as the logical instance that individuates or singularises validity (intentionality, act), and activity qua realisation of validity, and hence the real or concrete subject as the factor that realises validity.
