Immanuel Kant is considered the most important representative of German Enlightenment philosophy. Influenced by Isaac Newton, John Locke and David Hume, his work focused on the question of the possibility of metaphysical knowledge (Kritik der reinen Vernunft, 1781; Kritik der praktischen Vernunft, 1788; Kritik der Urteilskraft, 1790). He based his system of strict science on the mathematico-physical natural sciences and he criticised the basic principles of traditional metaphysics. Kant established a radical separation of philosophy and theology. He attempted to lay a new foundation for knowledge, morality and faith with his transcendental philosophy. In his search for a reliable justification of morality, he formulated the categorical imperative.
Hugo Bürkner (1818–1897), Immanuel Kant (1724–1804), etching, 1854; source: Bechstein, Ludwig: Zweihundert deutsche Männer in Bildnissen und Lebensbeschreibungen, Leipzig 1854, public domain.