13-3Kant's critical philosophy and his Copernican revolution The turning point in Kant's intellectual development was his encounter with Hume's empiricism.
Other German philosophers also joined in the enterprise of transforming Kant's critical philosophy into a metaphysical idealism—most notably, Hegel, Schelling, and Schopenhauer.
14-4-3Phenomenal and Noumenal Reality A major aspect of Kant's critical philosophy was his insistence that human knowledge is forever limited in its scope.
Apart from minor grounds on which Kant's philosophy may be criticized, there is one main objection which seems fatal to any attempt to deal with the problem of a priori knowledge by his method.
Thus according to the philosophers before Kant, the law of contradiction, which asserts that nothing can at the same time have and not have a certain property, sufficed to establish the truth of all a priori knowledge.