Immanuel Kant
Kant developed his moral philosophy in three works: "Groundwork of the Metaphysic of Morals" (1785), "Critique of Practical Reason" (1788), and "Metaphysics of Morals" (1797).
Rationalism
Kant named his brand of epistemology "Transcendental Idealism", and he first laid out these views in his famous work "The Critique of Pure Reason". In it he argued that there were fundamental problems with both rationalist and empiricist dogma. To the rationalists he argued, broadly, that pure reason is flawed when it goes beyond its limits and claims to know those things that are necessarily beyond the realm of all possible experience: the existence of God, free will, and the immortality of the human soul. Kant referred to these objects as "The Thing in Itself" and goes on to argue that their status as objects beyond all possible experience by definition means we cannot know them. To the empiricist he argued that while it is correct that experience is fundamentally necessary for human knowledge, reason is necessary for processing that experience into coherent thought. He therefore concludes that both reason and experience are necessary for human knowledge. In the same way, Kant also argued that it was wrong to regard thought as mere analysis. "In Kant's views, a priori concepts do exist, but if they are to lead to the amplification of knowledge, they must be brought into relation with empirical data".