Kant's "Copernican Revolution" is his effort to counter what
he saw as major weaknesses in Hume's empiricism. His study of Hume led him to reject rationalism's dogmatism, but Hume's empiricism did not fully satisfy him either. For example, Kant did not want to surrender
some of the subjects that concerned the rationalist metaphysicians, such as freedom and God, . . . even though he was prepared to say that we cannot have demonstrative knowledge of objects beyond our experience. Kant, therefore, sought to build upon what he thought was significant in both rationalism and empiricism and to reject what could not be defended. . . . (Stumpf 308).
The critical philosophy he developed sought to "prepare" for metaphysics, rather than to reject it as Hume did: "If metaphysics has to do with knowledge that is developed by reason alone, that is, prior to experience, or a priori, the critical question is how is such a priori knowledge possible" (Stumpf 308).
Therefore, Kant was trying to retain the reason of the rationalists (Spinoza, Leibniz), but in a less dogmatic form, and the empiricism of Hume, but in a less pessimistic form. Hume rejected metaphysics, whereas Spinoza, for example, too dogmatically affirmed his own theory of the nature of reality. Kant, with his reliance on a priori knowledge which gives the mind an active power denied by Hume's empiricism, opened up the possibility for philosophical inquiry into areas closed to or unconsidered by the rationalists and empiricists.
For example, as Kant says, if one says a chair is brown, one
can back up that claim with reference to experience. The chair is seen as brown and felt and sat in as a chair. However, if one makes a universal claim about a specific experience, the role of a priori is introduced.
If one looks at two points a foot apart on a table, one can see and say that the shortest distance between those two points is a straight line. However, if one extrap...