Kant

Immanuel Kant (1724–1804) is among the most important and challenging thinkers in the history of philosophy. He attempted a "Copernican revolution" in philosophy: rather than asking how the mind conforms to reality, he asked how reality as we experience it conforms to the structure of the mind.

Life

Kant was born in Königsberg, Prussia (now Kaliningrad, Russia) and never left the region. His life was famously regular — neighbours reportedly set their clocks by his afternoon walks. He spent decades as a private tutor and lecturer before publishing his major works in his fifties and sixties. He never married.

The Critical Philosophy

Kant's mature system — the Critical Philosophy — is developed across three Critiques:

Epistemology: The Copernican Revolution

In Epistemology, Kant aimed to reconcile rationalism (Descartes, Leibniz) with empiricism (Hume, Locke):

• Hume had shown that we cannot derive necessary truths from experience alone (the problem of induction)
• Kant responded: space, time, and the categories (causation, substance, unity…) are not read off from experience — they are the forms through which the mind structures experience
• We can have a priori knowledge of the empirical world, but only of the world as it appears to us (phenomena), not of things as they are in themselves (noumena)
• Metaphysics about God, the soul, and the cosmos as they are in themselves is impossible — these are ideas of reason that exceed possible experience

This gave Kant a powerful response to both the dogmatic rationalists (who claimed to know too much) and the skeptics (who claimed to know too little).

Ethics: The Categorical Imperative

Kant's moral philosophy rests on the Categorical Imperative — a supreme principle of morality derived from reason alone, not consequences or sentiment:

First formulation (Universal Law):

Act only according to that maxim by which you can at the same time will that it should become a universal law.

Second formulation (Humanity):

Act so that you treat humanity, whether in your own person or in that of another, always as an end and never as a means only.

Key features of Kantian ethics:

• Moral worth comes from acting from duty, not from inclination or self-interest
• Moral law is categorical (unconditional), not hypothetical ("if you want X, do Y")
• Persons have dignity — an incomparable worth that cannot be traded off against other goods
• Free Will and autonomy are presupposed by morality

See Categorical Imperative for a full treatment.

Aesthetics

In the Critique of Judgment, Kant analyzed the judgment of taste:

• Aesthetic pleasure is disinterested — not based on personal desire or practical use
• Judgments of beauty are subjectively universal — we feel they should command everyone's agreement
• The sublime differs from the beautiful: it overwhelms sense but reveals our rational superiority to nature

See Aesthetics for comparison with Plato, Hegel, and Nietzsche.

Influence

• Kant shaped virtually all subsequent philosophy in the West
• Hegel took Kant's idealism and radicalized it into absolute idealism via Dialectics
• Marx was shaped by Hegel's response to Kant
• Nietzsche both attacked and was fascinated by Kantian morality
• Phenomenology (Husserl) is in part a continuation of Kant's transcendental project
• Analytic philosophy of language (Frege, Wittgenstein) owes debts to Kant's syntheticism

Related Topics

• Categorical Imperative — Kant's supreme moral principle
• Epistemology — Kant's Copernican revolution
• Metaphysics — limits of metaphysical knowledge
• Aesthetics — the beautiful, the sublime, and taste
• Free Will — autonomy as the foundation of moral agency
• Hegel — who developed and criticized Kant's idealism
• Hume — whose skepticism awakened Kant from his "dogmatic slumber"
• Descartes — the rationalist tradition Kant sought to rescue and transform