It is because he takes into account the role of people's cognitive faculties in structuring the known and knowable world that in the second preface to the "Critique of Pure Reason" Kant compares his critical philosophy to Copernicus' revolution in astronomy. Kant (Bxvi) writes: Hitherto it has been assumed that all our knowledge must conform to objects. But all attempts to extend our knowledge of objects by establishing something in regard to them "a priori", by means of concepts, have, on this assumption, ended in failure. We must therefore make trial whether we may not have more success in the tasks of metaphysics, if we suppose that objects must conform to our knowledge.Just as Copernicus revolutionized astronomy by taking the position of the observer into account, Kant's critical philosophy takes into account the position of the knower of the world in general and reveals its impact on the structure of the known world. Kant's view is that in explaining the movement of celestial bodies Copernicus rejected the idea that the movement is in the stars and accepted it as a part of the spectator. Knowledge does not depend so much on the object of knowledge as on the capacity of the knower.