IF Frederick the Great had not lived we might never have had Immanuel Kant. The Critique of Pure Reason and Religion within the Limits of Reason Alone were made possible by Frederick’s skepticism and toleration; within two years after Frederick’s death Kant was silenced by the Prussian government.

Like Frederick, Kant was a child of the Enlightenment, and—despite all his strategic wavering—held by reason to the end; but also, like Rousseau, he was part of the Romantic movement, laboring to reconcile reason with feeling, philosophy with religion, morality with revolt. He received an infusion of Pietism from his parents, and crossed it with the rationalism of Christian von Wolff; he absorbed the heresies of the philosophes, and crossed them with the “Profession of Faith of the Savoyard Vicar” in Émile; he inherited the subtle psychology of Locke, Leibniz, Berkeley, and Hume, and used it in an attempt to save science from Hume and religion from Voltaire. He ordered his life with bourgeois regularity, and hailed the French Revolution. Isolated in East Prussia, he felt and summed up all the mental currents of his time.

He was born in Königsberg (April 22, 1724), far from clarity-loving France and misty with the sea. Some doubt has been cast upon the Scottish origin of the family, but Kant himself tells us that his grandfather, “at the end of the last … century (I know not for what cause) emigrated from Scotland to Prussia.”1 His father, Johann Georg Cant, married Anna Reuter; Immanuel (i.e., God with us) was the fourth of their eleven children. He took his Christian name from the saint of his birth day; he changed his surname from Cant to Kant to prevent the Germans from pronouncing it “Tsant.”2 All the family was brought up in the Pietist sect, which, like English Methodism, stressed faith, repentance, and immediate appeal to God, as against the orthodox Lutheran worship in church with a mediating priest.

A Pietist preacher had established at Königsberg a Collegium Fredericianum; Immanuel attended this from his eighth to his sixteenth year. The school day began at 5: 30 A.M. with a half hour of prayer; every class hour ended with prayer; an hour every morning was devoted to religious instruction, with emphasis on the fires of hell; history was taught chiefly from the Old Testament, Greek solely from the New. Sunday was given largely to religious devotions. It was an education that produced virtue in some of its graduates, hypocrisy in others, and perhaps a somber spirit in most. Kant later resented this heavy dose of piety and terror; fear and trembling, he said, overcame him when he recalled those days.3

In 1740 he moved on to the University of Königsberg. Here his favorite teacher was Martin Knutzen, who, though a Pietist, introduced Kant to the “rationalism” of Wolff. Knutzen had read the English deists; he condemned them but he discussed them, and he left some deistic doubts in at least one pupil. When, after six years at the university, Kant was invited to enter the Lutheran ministry, he refused despite the promise of early advancement to a comfortable post.4 Instead, for nine years, he lived in poverty, tutoring in private families, and continuing to study. His interest till 1770 was rather in science than in theology. Lucretius was one of his favorite authors.5

In 1755 Kant received the doctoral degree, and was allowed to lecture in the university as a Privatdozent, or private teacher, recompensed only by such fees as his students chose to pay. He continued in that insecure status for fifteen years. Twice in that long novitiate his applications for a professorship were rejected. He remained poor, moving from one boardinghouse to another, never daring to marry, never having a home of his own till he was fifty-nine.6 He lectured on a wide variety of topics, probably to attract a greater range of students, and he had to make himself clear in order to survive. Kant as a teacher must have been quite different from Kant the author, so famous for obscurity. Herder, who was one of his pupils (1762-64), described him thirty years later with grateful memory:

I have had the good fortune to know a philosopher who was my teacher. In the prime of life he possessed the joyous courage of youth, and this also, as I believe, attended him to extreme old age. His open, thoughtful brow was the seat of untroubled cheerfulness and joy, his conversation was full of ideas and most suggestive. He had at his service jest, witticism, and humorous fancy, and his lectures were at once instructive and most entertaining. With the same spirit in which he criticized Leibniz, Wolff, Baumgarten, … and Hume, he investigated the natural laws of Newton, Kepler, and the physicists. In the same way he took up the writings of Rousseau. … No cabal or sect, no prejudice or reverence for a name, had the slightest influence with him in opposition to the extension and promotion of truth. He encouraged and gently compelled his hearers to think for themselves; despotism was foreign to his disposition. This man, whom I name with the greatest gratitude and reverence, is Immanuel Kant; his image stands before me, and is dear to me.7

If we were to remember Kant chiefly by his work before his fifty-seventh year (1781), we should think of him as rather a scientist than a philosopher—though these two terms were not yet separate. His first published work, Gedanken von der wahren Schätzung der lebendigen Kräfte (Thoughts on the True Evaluation of Dynamic Forces, 1747), is a learned discussion of whether the force of a body in motion is to be measured (as Descartes and Euler held) by mv, the mass times the velocity, or (as Leibniz held) by mv,the mass times the square of the velocity; a remarkable performance for a lad of twenty-three. Seven years later came an essay on whether the time of the earth’s daily rotation is altered by the ebb and flow of the tides. In the same year Kant published Die Frage, ob die Welt veralte (The Question Whether the Earth Is Aging) ; here we have our modern solicitude over the sun’s daily loss of energy and the future congealing of our earth.

In a brilliant treatise of 1755, Allgemeine Naturgeschichte und Theorie des Himmels, the venturesome youth of thirty-one offered “a general history of nature and theory of the heavens.” It was published anonymously and was dedicated to Frederick the Great; perhaps Kant feared trouble from the theologians and hoped for protection from the King. He reduced all the operations of earth and sky to mechanical laws, but argued that the result, by its co-ordination and beauty, proved the existence of a supreme intelligence. To explain the origin of the solar system Kant proposed his “nebular hypothesis”:

I assume that all the material of our solar system … was, at the beginning of all things, decomposed into its primary elements, and filled the whole space … in which the bodies formed out of it now revolve. … In space so filled, a universal repose could last only a moment. … The scattered elements of a denser kind, by their attractive force, gather from … around them all the matter of less specific gravity; these elements themselves, together with the material which they have united with them, collect in those points where particles of a still denser kind are found; these in like manner join still denser particles, and so on. . . .

But nature has other forces, … by which these particles repel one another, and which, by their conflict with attractions, bring forth that movement which is, as it were, the lasting life of nature. … This force of repulsion is manifested in the elasticity of vapors, the effluence of strong-smelling bodies, and the diffusion of all spirituous matters. It is by this force that the elements, which may be falling to the point that attracts them, are turned sideways … from their movement in a straight line; and their perpendicular fall thereby issues in a circular movement around the center to which they are falling.8

Kant believed that all the stars had been gathered—or were being gathered—into such systems of planets and suns; and he added a significant phrase: “Die Sch öpfung ist niemals vollendet”— creation is never complete; it is ever going on.9

This nebular hypothesis of 1755, as well as its emendation by Laplace (1796), is as rich in difficulties as most subsequent theories of origins; yet in the judgment of a famous living astronomer, “Kant’s treatise on cosmogony was, I believe, the finest objective summary of science up to that time.”10 For us the significance of the essay is in its indication that Kant was no mystic metaphysician but a man fascinated by science, and struggling to reconcile scientific method with religious belief. This is the essence of his labors to the end.

In 1756, stirred like Voltaire to the depths of his philosophy by the Lisbon disaster of 1755, Kant published three essays on earthquakes, and one on a theory of winds. In 1757 he issued an “Outline and Announcement of a Course of Lectures on Physical Geography”; and in 1758, a “New Doctrine of Motion and Rest.” Then, his interest widening, he sent to the press short treatises on optimism (1759), the syllogism (1762), and “diseases of the head” (1764)—here suggesting that the increasing division of labor might by monotonous repetitions produce insanity. In 1763 he moved into theology with a treatise, The Only Possible Ground for Proving the Existence of God; obviously he was uncomfortable over the tottering of his religious faith. In 1764, eight years after Burke’s similar disquisition, he offered Observations on the Feeling of the Beautiful and the Sublime.

At times he thought of extending his evolutionary cosmogony to biology; he was familiar with the idea that new forms had evolved from older ones through changes in the conditions of life;11 and he accepted the view that the human anatomy was originally adapted to four-legged locomotion.12 Yet he drew back from a fully mechanistic biology. “I also have at times steered into the gulf, assuming here blind natural mechanics as the ground of explanation, and I believed I could discover a passage to the simple and natural conception. But I constantly made shipwreck of reason, and I have therefore preferred to venture upon the boundless ocean of ideas.”13 Rudolph Raspe (author of Baron Müchausen’s Travels) had recently discovered, and had in 1765 published, Leibniz’ long-lost Nouveaux Essais sur l’entendement humain; Kant could read this in French; it shared in turning him toward epistemology. He did not quite abandon his interest in science; as late as 1785 he composed an essay On Volcanoes in the Moon. But the internal conflict between his scientific studies and his inherited theology impelled him to seek a reconciliation in philosophy.

Probably his new direction was caused in part by the offer (1770) of a professorship in logic and metaphysics. The salary was small for a man of forty-six—167 thalers per year, rising slowly to 225 in 1786; incidental services as “senator” and “senior of the faculty” raised this in 1789 to 726 thalers. Custom required a newly appointed professor to deliver in Latin an inaugural discourse. Kant chose a difficult subject—De Mundi sensibilis et intelligibilis Forma et Principiis (On the Form and Principles of the Sensible and Intelligible World). Kant used the Scholastic terminology that still prevailed in the German universities. By “sensible world” he meant the world as perceived by the senses; he would later call this also the phenomenal world, or world of appearances. By “intelligible world” he meant the world as conceived by the intellect or reason; this he would later call the “noumenal,” or thinkable, world. We seek to understand the sensible world by applying to it the subjective concepts of space and time through mathematics and the sciences; we seek to understand the conceivable world by going beyond the senses, through intellect and metaphysics, to the supersensual sources and causes of the sensible world. Here Kant already laid down his basic theses: that space and time are not objective or sensible objects, but are forms of perception inherent in the nature and structure of the mind; and that the mind is no passive recipient and product of sensations, but is an active agent—with inherent modes and laws of operation—for transforming sensations into ideas.

Kant considered this seminal dissertation as “the text on which something further is to be said in the following work.” This statement, in a letter of 1771 to Marcus Herz, shows that the philosopher was already planning the Kritik der reinen Vernunft. After twelve years of work on that immense treatise he gave it to the world in 1781, dedicated to Karl von Zedlitz, minister of education and ecclesiastical affairs under Frederick the Great. Zedlitz, like the King, was a child of the Aufklärung, and supported the freedom of the press. His protection would be precious if the theologians should perceive, behind Kant’s esoteric vocabulary and apparently orthodox conclusions, one of the most destructive analyses that the Christian theology has ever received.

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