Immanuel Kant was a German philosopher. Born in Königsberg in the Kingdom of Prussia, he is considered one of the central thinkers of the Enlightenment. His comprehensive and systematic works in epistemology, metaphysics, ethics, and aesthetics have made him one of the most influential and highly discussed figures in modern Western philosophy.
In his doctrine of transcendental idealism, Kant argued that space and time are mere "forms of intuition [German: Anschauung]" that structure all experience and that the objects of experience are mere "appearances". The nature of things as they are in themselves is unknowable to us. Nonetheless, in an attempt to counter the philosophical doctrine of skepticism, he wrote the Critique of Pure Reason (1781/1787), his best-known work. Kant drew a parallel to the Copernican Revolution in his proposal to think of the objects of experience as conforming to people's spatial and temporal forms of intuition and the categories of their understanding so that they have a priori cognition of those objects.
Kant believed that reason is the source of morality and that aesthetics arises from a faculty of disinterested judgment.