Born Apr. 22, 1724, in Königsberg (now Kaliningrad); died there Feb. 12, 1804. German philosopher and scholar; founder of German classical philosophy.

Kant lived his whole life in Königsberg, where he graduated from the university in 1745. He was a docent there from 1755 to 1770 and a professor from 1770 to 1796. Two periods are distinguished in Kant’s philosophical development: a precritical period that lasted until 1770 and a critical period. In his precritical period Kant admitted the possibility of speculative knowledge of things as they are in themselves (or of “metaphysics,” in the language of the age). In his critical period he rejected the capacity for such knowledge on the basis of preliminary research into the forms of cognition and the sources and limits of our cognitive capabilities.

During his precritical period Kant wrote his General Natural History and Theory of the Heavens (1755), in which he elaborated a “nebular” cosmological hypothesis on the formation of the planetary system from an original nebula, that is, from a huge cloud of diffuse matter. In the estimation of F. Engels, this theory “was the greatest advance made by astronomy since Copernicus. For the first time the conception that nature had no history in time began to be shaken” (K. Marx and F. Engels, Soch., 2nd ed., vol. 20, p. 56). At this time Kant also proposed the existence of a “great system of galaxies” outside our galaxy; he demonstrated the slowdown in the Earth’s daily rotation on its axis as a result of tidal friction; and he also developed the idea of the relativity of movement and rest. In biology Kant presented the idea of a genealogical classification of the animal world. In his research on anthropology, he advanced the notion of the natural development of the human races. Along with his works in the natural sciences, Kant wrote a number of philosophical works during his precritical period. Under the influence of the empiricism and skepticism of the English philosopher D. Hume, he distinguished real and logical foundations and mocked the infatuation of some of his contemporaries with “spirit visions.”

Kant’s dissertation The Forms and Principles of the Sensible and the Intelligible Worlds (1770) marked the beginning of his transition to the views of his critical period, the chief works of which were the Critique of Pure Reason (1781), Critique of Practical Reason (1788), and Critique of Judgment (1790). Fundamental to all three Critiques was Kant’s theory of appearances and things as they are—of “things-in-themselves.” According to Kant, our cognition begins when things-in-themselves affect our external sense organs and produce our perception. This premise in his theories would make Kant a materialist. But his theories on the forms and limits of cognition showed Kant to be an idealist and agnostic. He affirmed that neither the data of sense perception nor the concepts and judgments of our understanding could give us any theoretical knowledge of things-in-themselves. These things cannot be known. To be sure, empirical knowledge of things can become broader and more profound without limit, but this does not bring us one iota closer to cognition of things-in-themselves.

Kant introduced a distinction between ordinary, or general, logic, which investigates the forms of thought and abstracts from questions of subject matter, and transcendental logic, which investigates in the forms of thinking that which imparts to knowledge an a priori, universal, and necessary character. Kant formulated his fundamental question—the sources and limits of knowledge—as the question of the possibility of a priori synthetic judgments (that is, judgments producing new knowledge) in each of the three chief forms of knowledge: mathematics, theoretical natural science, and metaphysics (speculative knowledge of the truly real). Kant attempts to resolve these three questions, posed in his Critique of Pure Reason, by investigating the three basic capacities of cognition: sensibility, understanding, and reason.

The foundation of mathematics lies in the perception of space and time, whose forms cease in Kant’s thinking to be forms of existence of the things themselves and become only a priori forms of sensibility. The basis of these perceptions lies in “pure” forms of space and time, that is, forms independent of and preceding experience (a priori). This assures the universality and necessity of mathematical truths.

In theoretical natural science the possibility of a priori synthetic judgments is conditioned by 12 categories of understanding that, as “pure” concepts, are a priori: for example, unity, plurality, totality, reality, and negation. But for genuine knowledge to arise, there must be a joining or synthesis of sense perception with the categories of understanding. The highest condition of such a synthesis is the unity of our consciousness. In Kant’s opinion, to the extent that universal and necessary laws of experience belong not to nature itself but only to understanding, which imposes them on nature, natural science constructs its own subject-matter as far as its logical form is concerned.

Kant reduces the question of the possibility of synthetic judgments in “metaphysics” to an investigation of reason, which gives birth to “ideas”—concepts of the absolute totality or unity of conditioned phenomena (such concepts as the soul, the world, and god). Kant concluded that all three speculative sciences of traditional philosophy treating these ideas (“rational psychology,” “rational cosmology,” and “rational theology”) are only pseudosciences. Realizing that his critique tended to limit the competence of reason, Kant proposed that where cognition lost, faith gained. Since god cannot be found in experience and does not belong to the world of phenomena, his existence can neither be proved nor disproved. Religion thus becomes an object of faith and not of science or of theoretical philosophy. According to Kant, it is not only possible but necessary to believe in god, because without this faith one cannot reconcile the demands of moral conscience with the indisputable facts of evil ruling in human life.

The Kantian critique of rational cosmology played a great role in the development of philosophy. According to Kant, the claims of rational cosmology necessarily lead to the appearance of antinomies in reason, contradictory but equally provable answers to the questions of rational cosmology: the world is finite and has no limits; there are indivisible particles (atoms) and there are no indivisible particles; all processes are causally conditioned and there are processes (actions) that are accomplished freely. Thus, reason is by nature antinomic and dialectic. However, according to Kant this dialectic of cosmological statements remains only subjective. It does not express the contradictions of the things themselves and does not violate the logical prohibition on contradictions. According to Kant, all the contradictions of the cosmological “dialectic” fall away when the false assumption at their base falls away: that the world as an absolute totality can be the object of theoretical cognition by reason.

Kant constructed his ethics on the basis of his critique of theoretical reason. His initial assumption showed the influence of the French philosopher J. -J. Rousseau: the conviction that every individual is an end in himself and should in no way be seen as the means for carrying out any task whatever, even one for the general good. Kant declared the fundamental law of ethics to be the internal directive or “categorical imperative” requiring that one be guided by the purely formal rule: to act always according to a maxim that could become a universal law; or, in another formulation, to act in such a way that you always behave toward humanity—in both your own person and the person of others—as an end and not only as a means.

In aesthetics Kant reduced the beautiful to “disinterested” pleasure that does not depend on whether the object portrayed in the work of art exists or does not exist but that is conditioned only by its form. However, Kant could not consistently maintain his formalism: despite the formal character of the categorical imperative, in his ethics he advanced the principle of the value as an end in himself of every man; and despite the formalism of his conception of the beautiful, in his aesthetics he declared the highest form of art to be poetry, since it ascends to the portrayal of the ideal.

Kant’s ideas on the role of antagonisms in the historical process of the life of society were progressive. According to Kant, the attainment of the greatest goal of humanity, universal legal civil status, was possible only through the action of forces that seem to be the source only of struggle and enmity. Along with this, a state of perpetual peace among all states was to be attained. Kant considered the means for establishing and preserving peace to be the development of international trade and contacts, with their mutual advantages for various states.

Although Kant’s theories contained abundant contradictions, they exerted an enormous influence on the later development of scientific and philosophical thought. By his theories on the antinomies of reason, Kant played an outstanding role in the development of dialectics. Philosophers of the most diverse tendencies have both criticized Kant and tried to develop his ideas. Neo-Kantianism, which arose in the 1860’s, tried to elaborate a system of idealism on the basis of Kant’s ideas. The dual character of Kant’s philosophy, which allowed it to be criticized both from the right and from the left, was noted by the classical writers of Marxism-Leninism, who highly valued its positive aspects while criticizing its subjective idealist and agnostic tendencies (see V. I. Lenin, Poln. sobr. sock, 5th ed., vol. 18, pp. 202–14). Karl Marx considered that in terms of its social content Kant’s philosophy was a German theory of the French bourgeois revolution (see K. Marx and F. Engels, Sock, 2nd ed., vol. 3, p. 184).