Kant’s Philosophies

Why are Kant’s philosophies still relevant?

Immanuel Kant (1724–1804) remains one of the great modern thinkers because he developed a whole new philosophy, one that completely reinterpreted human knowledge. A professor at Germany’s Königsberg University beginning in 1755, Kant lectured widely and was a prolific writer. His most important work came somewhat late in life—after 1775. It was in that year that he undertook “a project of critical philosophy,” in which he aimed to answer the three questions that, in his opinion, have occupied every philosopher in Western history: What can I know? What ought I do? For what may I hope?

Kant’s answer to the first question (What can I know?) was based on one important conclusion: What a person can know or make claims about is only his or her experience of things, not the things in themselves. The philosopher arrived at this conclusion by observing the certainty of math and science: He determined that the fundamental nature of human reality (metaphysics) does not rely on or yield the genuine knowledge of science and math. For example, Newton’s law of inertia—a body at rest tends to remain at rest, and a body in motion tends to remain in motion—does not change based on human experience. The law of inertia is universally recognized as correct and as such, is a “pure” truth, which can be relied on. But human reality, argued Kant, does not rest on any such certainties. That which a person has not experienced with their senses cannot be known absolutely. Kant therefore reasoned that free will cannot be proved or disproved—nor can the existence of God.

Even though what humans can know is extremely limited, Kant did not become skeptical. On the contrary, he asserted that “unknowable things” require a leap of faith. He further concluded that since no one can disprove the existence of God, objections to religion carry no weight. In this way, Kant answered the third question posed by philosophers: For what may I hope?

After arriving at the conclusion that each person experiences the world according to his or her own internal laws, Kant began writing on the problem of ethics, answering the second question (What ought I do?). In 1788 he published the Critique of Practical Reason, asserting that there is a moral law, which he called the “categorical imperative.” Kant argued that a person could test the morality of his or her actions by asking if the motivation should become a universal law—applicable to all people: “Act as if the maxim from which you act were to become through your will a universal law.” Kant concluded that when a person’s actions conformed with this “categorical imperative,” then he or she was doing his or her duty, which would result in goodwill.

Kant’s theories have remained relevant to philosophy for more than two centuries: modern thinkers have either furthered the school of thought that Kant initiated or they have rejected it. Either way, the philosopher’s influence is still felt. It’s interesting to note that among his writings is an essay on political theory (Perpetual Peace), which first appeared in 1795: In it, Kant described a federation that would work to prevent international conflict; the League of Nations and the United Nations, created more than a century after Kant, are the embodiments of this idea.

German philosopher Georg Hegel (in an 1884 portrait) theorized that at the center of the universe there is an absolute spirit that guides all reality. (Original painting by Ernst Hader.)

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