Idealism - Immanuel Kant

Immanuel Kant was a German philosopher and one of the central Enlightenment thinkers. Born in Königsberg, Kant's comprehensive and systematic works in epistemology, metaphysics, ethics, and aesthetics have made him one of the most influential figures in modern Western philosophy.
In his doctrine of transcendental idealism, Kant argued space and time are mere "forms of intuition" 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. In an attempt to counter the philosophical doctrine of skepticism, he wrote the Critique of Pure Reason (1781/1787), his most well-known work. Kant drew a parallel to the Copernican revolution in his proposal to think of the objects of experience as conforming to our spatial and temporal forms of intuition and the categories of our understanding, so that we have a priori cognition of those objects.