Immanuel Kant, (born April 22, 1724, Königsberg, Prussia [now Kaliningrad, Russia]—died February 12, 1804, Königsberg), German philosopher whose comprehensive and systematic work in epistemology (the theory of knowledge), ethics, and aesthetics greatly influenced all subsequent philosophy, especially the various schools of Kantianism and idealism.
Kant was one of the foremost thinkers of the Enlightenment and arguably one of the greatest philosophers of all time. In him were subsumed new trends that had begun with the rationalism (stressing reason) of René Descartes and the empiricism (stressing experience) of Francis Bacon. He thus inaugurated a new era in the development of philosophical thought.
Kant defines his theory of perception in his influential 1781 work the Critique of Pure Reason, which has often been cited as the most significant volume of metaphysics and epistemology in modern philosophy. Kant maintains that our understanding of the external world had its foundations not merely in experience, but in both experience and a priori concepts, thus offering a non-empiricist critique of rationalist philosophy, which is what he and others referred to as his "Copernican revolution"