Immanuel Kant

• 1. Introduction

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  Immanuel Kant lived so rigidly that his neighbors in Königsberg were said to set their watches by his daily walks. He was born Emanuel on the 22nd of April 1724, the son of a harness-maker, in a Lutheran household that prized humility and a literal reading of the Bible. He never married, never traveled far, and graduated into a teaching post he held for the rest of his life. Yet from this small, ordered existence came some of the most discussed thinking in modern Western philosophy. How does a provincial professor end up compared to a king-weighing executioner of ideas? What did Kant mean when he said he had to deny knowledge to make room for faith? And why did a single dense book over eight hundred pages long, which disappointed its first readers, come to be called the most significant work of metaphysics in modern philosophy? The answers reach from the formation of galaxies to the structure of the human mind.

• 2. The Königsberg Stoic

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  Anna Regina Reuter, Kant's mother, was born in Königsberg to a father from Nuremberg; her surname is sometimes wrongly given as Porter. His father, Johann Georg Kant, came from Memel, then Prussia's most northeastern city. Kant believed his family had Scottish roots, though genealogy has never confirmed it. He was baptized Emanuel and later changed the spelling to Immanuel after learning Hebrew. The fourth of nine children, six of whom reached adulthood, he grew up under a strict, punitive education that leaned on Latin and religious instruction rather than mathematics and science. Kant considered marriage twice, first to a widow and then to a Westphalian girl, but on both occasions he waited too long. He never married. Even so, he was fond of company and conversation, a popular teacher and a modestly successful author before his major works appeared. He kept company with students, colleagues, and diners at the local Masonic lodge; his main publisher, Johann Friedrich Hartknoch, was also a Freemason. Near the end, his health long poor, he died in Königsberg on the 12th of February 1804, saying Es ist gut, meaning It is good.

• 3. Star Clouds And Earthquakes

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  In 1754, weighing a prize question from the Berlin Academy about Earth's rotation, Kant argued that the Moon's gravity would slow the planet's spin. He also reasoned that gravity would eventually lock the Moon's rotation to match the Earth's. The following year he carried this thinking to the whole Solar System in his Universal Natural History and Theory of the Heavens. There he laid out the nebular hypothesis, deducing that the Solar System had condensed from a vast cloud of gas. Kant also correctly worked out that the Milky Way is a large disk of stars formed from a far larger spinning cloud, and he suggested that distant nebulae might be other galaxies. His 1756 essay on winds offered an early qualitative grasp of what is now called the Coriolis force. That same year he published three papers on the 1755 Lisbon earthquake. His explanation, involving shifts in huge caverns of hot gases, was wrong, yet it was one of the first attempts to account for earthquakes in natural rather than supernatural terms. In 1757 he began lecturing on geography, becoming one of the first to teach it as a subject in its own right.

• 4. The Sleep Of Reason

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  At age 46 Kant was an established scholar, much expected of him, yet privately stuck. In letters to his former student and friend Markus Herz, he admitted that his inaugural dissertation had failed to explain how our sensible and intellectual faculties relate. He needed to show how sensory knowledge combines with reasoned knowledge, two related processes that work very differently. Kant credited David Hume with waking him from an unquestioning acceptance of both religion and natural philosophy. Hume, in his 1739 Treatise on Human Nature, had argued that we know the mind only through a subjective, essentially illusory series of perceptions. On that view, ideas like causality, morality, and objects are not evident in experience, so their reality can be doubted. Hume called causal connection the cement of the universe and denied any necessary link between causal events. Kant believed reason could remove this skepticism and set himself to the problem. Fond of company yet now resisting friends who tried to draw him out, he withdrew into silence to solve it.

• 5. The Copernican Turn

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  When Kant broke his silence in 1781, the result was the Critique of Pure Reason, printed by Johann Friedrich Hartknoch. He drew a parallel to the Copernican revolution: just as Copernicus advanced astronomy by a radical shift in perspective, Kant proposed thinking of objects as conforming to our forms of intuition, rather than the mind conforming to its objects. He framed the whole project as one question. How are synthetic judgments a priori possible? A judgment is analytic when its predicate is already contained in its subject, as in all bachelors are unmarried. It is synthetic when the predicate adds something new, as in all bodies have weight. Knowledge can come before experience, a priori, or from experience, a posteriori. Kant argued that earlier thinkers had neglected the synthetic a priori, judgments that are both necessary and genuinely informative, such as the proposition seven plus five equals twelve. He held that the concept of twelve is not contained in five, seven, and addition. Showing how such judgments are possible meant showing how substantive knowledge about the world's necessary features is possible at all.

• 6. Forms Of Intuition

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  Space and time, Kant argued in the Transcendental Aesthetic, are not things in themselves but mere forms of intuition. Space is the form of outer intuition; time is the form of inner intuition. From this he drew a second thesis: we have knowledge only of appearances, never of things as they are in themselves. Because our forms of intuition are necessary conditions for any experience, whatever lies beyond what our senses can receive stays unknowable. He called these forms transcendentally ideal yet empirically real, by which he meant that everything coming to us as an external object is in space and time. Kant summed up the partnership of the two faculties with a line that became famous: Thoughts without content are empty, intuitions without concepts are blind. He distinguished his view from the subjective idealism of George Berkeley, and in the second edition added a Refutation of Idealism. Interpreters still divide over what he meant. The two-aspect reading, popularized by Henry E. Allison, treats the thing-in-itself and the appearance as one object. The two-world reading takes appearances and things in themselves to be genuinely distinct.

• 7. The Good Will

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  The source of the good, Kant argued, lies not in nature or in God but only in the good will itself. A good will acts from duty in accordance with a universal moral law that the autonomous person freely gives to themselves. This law commands us to treat humanity, understood as rational agency, always as an end in itself and never merely as a means. He grounded all moral obligation in the categorical imperative. A hypothetical imperative must be obeyed only to satisfy some contingent desire. A categorical imperative binds rational agents regardless of their desires, because we cannot opt out of being rational agents. Kant gave three formulations he held to be equivalent, though many scholars are not convinced. The Formula of Universal Law tells us to act only on a maxim we could will to become a universal law. Consider the maxim that it is permissible to break promises. Universalized, no one would trust any promise, so promising would become meaningless and the maxim would destroy itself. He developed this ethics across the Groundwork of 1785, the Critique of Practical Reason of 1788, and the Metaphysics of Morals of 1797.

• 8. Fame, Censorship, And A Tomb

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  Kant's fame arrived from an unexpected source. In 1786 Karl Leonhard Reinhold published public letters framing Kant's philosophy as the answer to the pantheism controversy, the bitter dispute that followed Friedrich Jacobi's charge of Spinozism against the late Gotthold Ephraim Lessing. Reinhold argued that the Critique could settle the quarrel by defending the bounds of reason, and his widely read letters made Kant the most famous philosopher of his era. Then came conflict with the state. In 1792 the King's censorship commission, newly formed amid the French Revolution, blocked part of Kant's Religion within the Bounds of Bare Reason. When he published a second edition in 1794, an irate censor secured a royal order forbidding Kant to publish or even speak publicly about religion. He answered in the preface to The Conflict of the Faculties of 1798. Heinrich Heine later called him a philosophical executioner and compared him to Maximilien Robespierre. When Kant's body was later moved, his skull was measured and found larger than the average German male's, with a high and broad forehead. His mausoleum, built by the architect Friedrich Lahrs and finished in 1924, still draws flowers from newlyweds beside Königsberg Cathedral.