Immanuel Kant (22-Apr-1724 to 12-Feb-1804) was a German philosopher and one of the central Enlightenment thinkers. 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 that space and time are mere forms of intuition
which structure all experience, and therefore that while things-in-themselves
exist and contribute to experience, they are nonetheless distinct from the objects of experience. From this it follows that the objects of experience are mere appearances
, and that the nature of things as they are in themselves is consequently unknowable to us. In an attempt to counter the skepticism he found in the writings of philosopher David Hume, he wrote the Critique of Pure Reason (1781/1787), one of his most well-known works. In it, he developed his theory of experience to answer the question of whether synthetic a priori knowledge is possible, which would in turn make it possible to determine the limits of metaphysical inquiry. Kant drew a parallel to the Copernican revolution in his proposal that the objects of the senses must conform to our spatial and temporal forms of intuition, and that we can consequently have a priori cognition of the objects of the senses.
Immanuel Kant Wikipedia