Immanuel Kant is considered one of the most important figures in the history of western philosophy. His most influential works are his three critiques, Critique of Pure Reason, Critique of Practical Reason, and Critique of Judgment and his Foundations of the Metaphysics of Morals. In these works, he altered the course of future thought in epistemology, aesthetics, and ethics. In epistemology, his most important ideas can be found in his distinctions between things understood analytically and synthetically and a priori and a posteriori, and in particular his notion of synthetic a priori concepts which we attach to all our representations. In ethics, his three imperatives were very influential, the notions that morality must be universalizable, must treat all intelligent beings as ends in themselves, and that for an action to be moral it must be willed as a moral act.