Kant's Critique of Rationalism: Substance, Essence, Noumenon

This dissertation provides a novel account of Kant's distinction between appearances and things in themselves, and of Kant's denial that we know things in themselves. I show that one can appreciate Kant's distinction only by seeing how deeply engaged his philosophy is with the metaphysics of substance as developed in the Aristotelian and scholastic traditions. I argue that Kant's distinction amounts to the classical distinction between the essence of a substance on the one hand and its sensible qualities and powers on the other. Kant's denial that we know things in themselves thus conceived is, therefore, part of a tradition of reflections on the unknowability of substance found in scholastic and early modern thought. Kant's philosophical originality thus does not lie so much in the conclusions he reaches about the unknowability of substance. Rather, it lies in the manner in which he reaches them, which he calls critique: the project of unfolding out of the concept of a finite faculty of knowledge both the proper objects of that faculty and the limits of what we can know of them.