Widely considered one of the most important philosophers to have ever lived, Immanuel Kant was born in Königsberg, Prussia (now Kaliningrad, Russia) in 1724. His father was a harness maker; the members of the Kant household were strict Lutherans, and followers of the Pietist movement—a form of Lutheranism that placed a very strong emphasis on reading and interpreting the Bible. Kant’s parents hoped that he would have a career as a priest; accordingly, his first studies were in religion and Latin.
As a youth Kant attended the Collegium Friedricianum, a prestigious gymnasium, or preparatory school. He then attended the University of Königsberg in 1740. There, he distinguished himself in the study of philosophy. His teacher, Martin Knutzen, introduced him to the rationalist work of Leibniz and Christian Wolff, as well as to the mathematical physics of Isaac Newton. Kant left the university when his father died in 1748; like many scholars of the time, he found work as a Privatdozent, or private tutor for the aristocracy and upper bourgeoisie.
Rival accounts persist of Kant’s personality. He is frequently caricatured as an uptight, joyless man, who took his walks so punctually that the nuns in Königsberg set the clock at the abbey by the sound of his cane. His study was supposedly stripped of all decoration except for a portrait of the philosopher Jean-Jacques Rousseau. It is, in any case, true that Kant never married; nonetheless, he seems to have been a well-loved teacher, and to have carried on a lively social life, hosting popular luncheons at his home.
Kant’s work as a philosopher is usually divided into its “pre-critical” and “critical” phases—before and after the publication of The Critique of Pure Reason in 1781. Kant’s first publications were largely scientific, concerning questions in mathematics and astronomy. His first properly philosophical works appeared in the 1760s, and handled issues like logic, aesthetics, religion, and even the existence of ghosts. In 1770, he was appointed chair of philosophy at the University of Königsberg, making him the first major philosopher to have earned his living as a professor. He defended his appointment with a treatise on the difference between sensory perception and intellectual thought, a question that would be central to his later work.
Around 1771, Kant read the works of David Hume. The problems posed by Hume’s skeptical empiricism caused Kant to reconsider, if not entirely reject, many of his earlier positions, and he took a ten-year hiatus from writing. He returned with the work widely considered his most significant, The Critique of Pure Reason, his attempt to answer the question, “What can we know?”, by synthesizing the rationalism of his university education with Hume’s empiricism. The work did not immediately receive the reception he had hoped it would; in 1783, he wrote the Prolegomena to explain its central argument, and in 1787 he heavily revised the Critique and published it again.
The Critique was followed by a work on ethics, The Critique of Practical Reason, in 1788—his answer to the question, “What should we do?” Here, Kant advanced the argument that human beings could only act freely by forming their moral actions as the basis for a universal law. The second critique was followed by the third, and final one, The Critique of the Power of Judgment in 1790, a work on aesthetics and teleology, answering what Kant believed to be the third central question of philosophy, “What may we hope?” This period also saw the publication of his two most widely-read texts, the programmatic essay “What is Enlightenment?” (1784), and the “Groundwork for the Metaphysics of Morals,” a short work outlining what would be the main arguments of the second critique.
Kant’s final years saw a rapid decline in his health, and an expansion of his fields of study. He wrote about the French Revolution, anthropology, and religion. His publications on the latter subject caused him to be censored by the Prussian government for what was widely perceived as an attack on religious authority. His last philosophical works were an attack on the nascent movement of German Idealism, which derived radical conclusions from many of his arguments. He died in 1804 in Königsberg, at the age of 80.