Self-consciousness, that is, the ground of a priori synthetic judgment, is the center of Kant's epistemology, while the doctrine of the thing in itself is the center of Kant's whole system of philosophy. In the conclusion to the Transcendental Analytic, Kant devoted an entire chapter to "The Ground of the Distinction of all Objects in general in Phenomena and Noumena." There he explained the concept of the thing in itself.