Immanuel Kant
German philosopher (1724–1804) from Königsberg who synthesized rationalism and empiricism in his Critique of Pure Reason, established the categorical imperative as the foundation of ethics, and defined the Enlightenment as humanity's emergence from self-imposed immaturity.
Kant is the pivot point of Western philosophy. Before him, philosophy was split between rationalists (Descartes, Leibniz: reason gives us knowledge independent of experience) and empiricists (Hume, Locke: all knowledge comes from sensory experience). Kant performed what he called a 'Copernican revolution': the mind does not passively receive reality, it actively structures it through built-in categories of space, time, and causality.
His Critique of Pure Reason (1781) distinguished between phenomena (the world as we experience it, structured by our minds) and noumena (things-in-themselves, forever beyond our knowledge). This was both a limitation and a liberation: by defining the limits of knowledge, Kant made room for faith.
His ethics, the categorical imperative, commands: 'Act only according to that maxim by which you can at the same time will that it should become a universal law.' This is the formal structure of moral duty, not happiness or consequences, but the logical consistency of your action when universalized.
His essay What is Enlightenment? (1784) gave the era its motto: Sapere aude, 'Dare to know.' Have the courage to use your own reason without the guidance of another. This is the foundational statement of intellectual maturity.
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Frequently asked questions
What is Kant's categorical imperative? ＋
The supreme principle of moral duty: act only according to a maxim you could will to become a universal law. If lying were universal, language would collapse, so lying violates the categorical imperative. This is pure rational ethics, without reference to consequences or happiness.
What did Kant mean by phenomena and noumena? ＋
Phenomena are the world as we experience it, structured by our minds' categories of space, time, and causality. Noumena are things-in-themselves, the underlying reality that exists independently but is forever inaccessible to human cognition.