Immanuel Kant (April 22, 1724 – February 12, 1804) was a Prussian philosopher born in Königsberg. He spent his entire life in his native city, declining offers of positions and titles in order to continue his academic career there.

Between 1746 and 1758, Kant focused on the natural sciences; in the 1760s, he grew skeptical of metaphysics; and after 1769, he developed his critical philosophy. With the publication of Critique of Pure Reason (1781), he began a period in which he examined the limits and conditions of human knowledge, seeking to explain how the human mind apprehends nature. According to Kant, experience arises from the mind’s organization of sensory data through the categories of space, time, and causality. His thought aimed to ground the relationship between the necessity of natural laws and the moral freedom of human beings.

Early Life and Education

Immanuel Kant was born on April 22, 1724, in Königsberg. His father was a leatherworker who experienced little happiness in life, while his mother, Anna Reuter, was a strong-minded, pious, and rational woman. The family belonged to a Pietist community, a commitment that influenced both Kant’s access to education and the formation of his moral outlook. With the support of F. A. Schultz—the pastor of the family’s church and head of the Collegium—Kant entered the Collegium Fridericianum in 1732, where he studied for eight years.

In 1740, at the age of sixteen, he enrolled at the University of Königsberg. There he became a student of Martin Knutzen, who introduced him to the ideas of Leibniz, Newton, and Wolff, and guided him toward the mathematical-physical method in science. During his university years, Kant mastered Latin, worked with several of the era’s most promising students, and concentrated particularly on natural philosophy. These formative years laid the foundation for his later intellectual development.

Teaching and Academic Career

After the death of his parents in 1746, Kant began working as a private tutor for clergymen and noble families in East Prussia to support himself. During this nine-year period, he lived in various regions; the years he spent on the Judisch and Arnsdorf estates provided him with opportunities to observe society closely and gain insight into human behavior. Through the Keyserling family, whom he met in Arnsdorf, Kant established connections with the intellectual and cultural circles of the time.

In 1755, Kant returned to Königsberg and, in the same year, earned the title of Privatdozent (lecturer), which allowed him to teach at the university. That year, he defended his dissertation De Igne (“On Fire”) and soon afterward published his notable work Universal Natural History and Theory of the Heavens. In his lectures, Kant adopted an interdisciplinary approach, combining mathematics, physics, and philosophy. Even during the Seven Years’ War, when Russian forces occupied Königsberg, he continued his teaching activities.

For sixteen years, Kant lectured as a Privatdozent. In 1766, he declined an offer to become Professor of Poetry. Four years later, in 1770, at the age of forty-six, he was appointed Professor of Logic and Metaphysics. He inaugurated his professorship with his Latin dissertation De Mundi Sensibilis atque Intelligibilis Forma et Principiis (“On the Form and Principles of the Sensible and Intelligible World”). From that point onward, his teaching increasingly turned toward the development of the foundations of his critical philosophy.

Intellectual Development

Kant’s intellectual development is generally divided into three successive periods. The first period, covering approximately the years 1746–1758, is characterized by his engagement with the natural sciences. During this stage, Kant sought to establish a universal law of nature applicable to the cosmos as a whole by extending Newton’s mechanical principles. In his work Universal Natural History and Theory of the Heavens, he argued that the universe developed “from the simplest state of nature through purely mechanical laws.”^【1】  In this period, Kant adopted a conception of the universe governed entirely by causal relations. For him, physical causes and natural laws did not contradict belief in God; rather, they opened a rational path to understanding divine order. This perspective led him to view the universe as a dynamic and self-organizing process.

The second period, emerging in the 1760s, is marked by critical skepticism. During these years, Kant began questioning the foundations of metaphysics. In Dreams of a Spirit-Seer (1766), he declared that “metaphysics is a science that does not yet exist,”^【2】  emphasizing the limits of reason and the indeterminacy of its concepts. Around this time, Kant encountered the philosophy of Rousseau, which inspired him to consider the moral dimension of human existence as a realm of value beyond the laws of nature. Thus began a transitional phase in which his thought moved from the explanation of nature toward the problems of morality and freedom.

The third period, beginning around 1769, is known as the era of critical philosophy. Kant turned to the question of how human knowledge is possible, arguing that knowledge arises not only from objects but also from the structure of the mind that apprehends them. In his 1770 Inaugural Dissertation, he distinguished between the sensible and the intelligible worlds, initiating an inquiry into the conditions of knowledge. This orientation reached maturity in the Critique of Pure Reason, where Kant argued that the forms of space, time, and causality—which shape all experience—belong to the mind’s own operations rather than to the external world. In doing so, he brought about a fundamental transformation in the theory of knowledge.

Critical Philosophy and Fundamental Views

Kant’s critical philosophy is founded on an effort to determine the limits and possibilities of human knowledge. Building upon the Newtonian conception of nature, he argued that knowledge depends both on sensory experience and on the mind’s formative activity. According to Kant, the senses provide the material of knowledge from the external world, but this material cannot become knowledge until it is organized by the mind’s formal principles—such as space, time, and causality. Referring to this revolutionary shift, Kant wrote: “Up to now it has been assumed that our cognition must conform to objects; but let us suppose that objects must conform to our cognition instead,”^【3】  calling this reversal his “Copernican Revolution.”

In Kant’s view, human experience occurs on three levels. The first is that of sensory impressions perceived by individual consciousness. The second is the world of phenomena, shared by all beings possessing the same sensory organization; this is the domain of scientific knowledge. The third level is the realm of things-in-themselves (Dinge an sich), which lies beyond sensory experience and can be conceived only by reason. This realm includes ideas such as God, the soul, and the world as a totality. Kant maintained that these ideas have no sensory counterparts but function as necessary regulative principles that guide thought.

The outcome of critical philosophy is the recognition that the human being is both subject to the laws of nature and free through the laws of reason. The understanding (Verstand) explains nature through necessary causes, while reason (Vernunft) establishes the sphere of moral freedom beyond necessity. Within this framework, science can discover the laws governing objects, but it can never reach the “thing-in-itself.” By setting limits to knowledge, Kant argued, reason opens a legitimate domain for faith and morality—thus reconciling natural necessity with moral freedom within a unified philosophical system.

Moral and Practical Philosophy

Kant’s conception of moral and practical philosophy is grounded in his view that the human being is both subject to natural necessity and free through the exercise of reason. According to him, human life unfolds on two levels: in the sensible world, a person is bound by causal necessity; in the rational domain, the same person acts as a free and autonomous subject. Nature operates according to the laws of cause and effect, whereas moral action presupposes the possibility of freedom. For this reason, the moral law does not arise from nature but solely from reason itself.

Following The Critique of Pure Reason, in which he established the limits of human knowledge, Kant turned to the practical use of reason. Practical reason is the capacity of human beings to legislate moral law for themselves; its validity depends not on external consequences but on the principle underlying the action. Kant held that a person must regulate his or her conduct according to the categorical imperative—the unconditional command of reason that requires actions to be guided by maxims that could be willed as universal laws.

The moral law, for Kant, addresses not only human beings but all rational agents. The ideas of freedom, immortality, and God are necessary postulates of the moral world, for only within a moral order can humanity find its true purpose. In Kant’s view, the existence of God cannot be demonstrated within the domain of theoretical reason; yet the idea of God is indispensable for the possibility of a moral universe. Thus, the limitation of reason in the sphere of knowledge safeguards the realm of faith and morality. By this synthesis, Kant unified the laws of nature and the laws of morality, reconciling necessity with freedom within a single philosophical system.

Major Works

Throughout his life, Kant wrote extensively on natural philosophy, metaphysics, ethics, religion, aesthetics, and political theory. His principal works include the following:

• Allgemeine Naturgeschichte und Theorie des Himmels (Universal Natural History and Theory of the Heavens, 1755): A work aiming to explain the formation of the universe solely through mechanical laws. In this study, Kant extended Newton’s principles and proposed that the universe could be understood as a dynamic, self-developing process.

• Monadologia Physica (Physical Monadology, 1756): An exploration of the structure of the universe in terms of “monads,” relating natural phenomena to mechanical causes.

• Der einzig mögliche Beweisgrund zu einer Demonstration des Daseins Gottes (The Only Possible Basis for a Demonstration of the Existence of God, 1763): A discussion of the relationship between the order of the universe and the concept of God.

• Träume eines Geistersehers, erläutert durch Träume der Metaphysik (Dreams of a Spirit-Seer, Explained by Dreams of Metaphysics, 1766): A critical inquiry into the limits of metaphysics, examining the scope and boundaries of human reason.

• De Mundi Sensibilis atque Intelligibilis Forma et Principiis (On the Form and Principles of the Sensible and Intelligible World, 1770): Written as Kant’s inaugural dissertation upon assuming his professorship, this work distinguishes between sensory and intellectual forms of knowledge.

• Kritik der reinen Vernunft (Critique of Pure Reason, 1781; 2nd ed. 1787): Kant’s seminal work, investigating the limits and conditions of human knowledge and laying the foundations of critical philosophy.

• Prolegomena zu einer jeden künftigen Metaphysik (Prolegomena to Any Future Metaphysics, 1783): A concise text intended to clarify and summarize the key arguments of the Critique of Pure Reason.

• Kritik der praktischen Vernunft (Critique of Practical Reason, 1788): An examination of the source of the moral law and the conditions of human freedom.

• Kritik der Urteilskraft (Critique of Judgment, 1790): A study linking aesthetics, teleology in nature, and the relationship between freedom and necessity.

• Zum ewigen Frieden (Perpetual Peace: A Philosophical Sketch, 1795): A political essay discussing the moral and legal foundations of lasting peace among nations.

Legacy and Influence

Through his critical method, Kant distinguished the spheres of knowledge, morality, and faith, defining the limits of validity proper to each. This distinction became a central axis of philosophical debate throughout the 19th century. Nearly all philosophical movements that followed were shaped around the problems and questions Kant had set forth.

Kant’s work bridged Leibniz’s rationalism and Hume’s empiricism, placing the critique of reason at the heart of modern philosophy. His approach preserved the legitimacy of the natural sciences while simultaneously providing a philosophical foundation for human moral freedom. This dual framework laid the groundwork for German Idealism, inspiring thinkers such as Fichte, Schelling, and Hegel, who each developed their own systems in response to Kant’s legacy.

Although Kant’s influence waned somewhat in the mid-19th century with the rise of materialism and the natural sciences, it regained prominence toward the end of the century. His ideas were reinterpreted in various philosophical movements: Neo-Kantianism in Germany, Neo-Criticism in France, Critical Idealism in Italy, and the British and American Idealist traditions. At the beginning of the 20th century, Kant’s thought was reassessed in the contexts of positivism, pragmatism, and theological debates. His critical method—establishing the limits and conditions of reason—continued to shape discussions in contemporary philosophy.

Death

In his later years, Kant suffered from severe mental fatigue and physical weakness. He gradually declined, his memory deteriorated, and he withdrew into solitude. This final stage of his life, following a long period of intellectual exertion, was described by those around him as a kind of “second childhood.”

Kant died in Königsberg on February 12, 1804. His contemporaries described his passing as “a painful yet merciful end.” He was buried in the cathedral of his native city, in a section later named the Stoa Kantiana. Inscribed on his tombstone are his own words from the Critique of Practical Reason:

“The starry heavens above me and the moral law within me.”^【4】