Kant described his great work not as a critique of "books and systems" but as a critique "of the faculty of reason as a whole, in regard to all knowledge to which it may aspire independently of all experience."¹ Reason provides knowledge which is independent of experience, according to Kant, not because we are able to acquire knowledge in the absence of experience, but because the knowledge that we acquire in the face of experience is partially a reflection of that experience and partially a reflection of our ways of acquiring knowledge. In exploring reason itself in terms of its a priori, or experientially independent, knowledge, Kant proposed to examine how the workings of our thought processes are reflected in the knowledge claims we make. One philosophical point of the work is to reveal that particular aspects of our common wisdom are going to be invariant across peoples and times. Such invariances cannot be established by assuming metaphysical principles about the necessary uniformity or continuity of nature. Kant introduced a new method. He tried to demonstrate philosophically important invariances throughout the body of human knowledge, by arguing that they reflect the ways in which anyone with our basic mental constitution will be capable of thinking.