Immanuel Kant (1724-1804) was a German philosopher whose work in epistemology, ethics, and metaphysics shaped the course of Western philosophy. In his landmark work, Critique of Pure Reason, Kant proposed "transcendental idealism," asserting that human knowledge is limited by the mind's structures, which mediate our understanding of reality. This "Copernican revolution" in philosophy argued that we can only know phenomena (appearances) and not noumena (things-in-themselves). In Critique of Practical Reason, Kant introduced the "categorical imperative," a foundational principle in ethics that calls for actions to be universally applicable. Kant's focus on autonomy, moral duty, and rationality laid the groundwork for modern ethical and political thought, and his ideas continue to influence fields such as philosophy, law, and cognitive science, positioning him as a central figure in the Enlightenment.