Immanuel Kant
Kant carried out what he called a 'Copernican revolution' in philosophy: rather than the mind conforming to objects, objects conform to the structure of the mind. Working in the quiet university town of Königsberg, he sought to secure both the certainty of science and the reality of human freedom and morality. His critical philosophy reshaped nearly every field that came after it.
Schools
Key concepts
Core works
Critique of Pure Reason
1781Kant asks how knowledge that is both necessary and informative — like mathematics and physics — is possible at all. His answer: the mind is not a passive receiver but actively structures experience. Space and time are forms our sensibility imposes, and categories like causation are concepts the understanding brings to all experience. We therefore have genuine knowledge of the world as it appears (phenomena), but never of things as they are in themselves (noumena). This both secures science and humbles metaphysics: traditional proofs about God, the soul, and the cosmos overreach the bounds of possible experience. By limiting knowledge, Kant argues, he makes room for rational faith and moral freedom.
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Groundwork of the Metaphysics of Morals
1785Kant seeks the supreme principle of morality and locates it in reason rather than consequences or feelings. A good will, he argues, is good not for what it achieves but in itself. Moral worth lies in acting from duty — from respect for the moral law — not from inclination. That law is the categorical imperative: act only on a maxim you could will to become a universal law, and always treat humanity, in yourself and others, never merely as a means but always also as an end. Because rational beings give this law to themselves, morality is grounded in autonomy, and to be moral is to be genuinely free.
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