One of Hume"s and Kant"s most central claims is to have proposed and worked out a new system of thought which solves the age-old baffling problems of philosophy in an entirely new way. The "principles" of human nature which Hume discovers in his philosophy correspond programmatically to the "categories" which Kant works out in his philosophy. The thesis to be defended here is that the principles as well as the categories rest ultimately on the special constitution of human mind, human nature. The relativization of all our knowledge in every field of our enquiry to human nature is the central teaching of Hume"s as well as of Kant"s philosophy.