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).
Critique of the Kantian philosophy
At the time he wrote his criticism, Schopenhauer was acquainted only with the second (1787) edition of Kant's "Critique of Pure Reason". When he later read the first (1781) edition, he said that many of Kant's contradictions were not evident.