An Introduction to Immanuel Kant

Austin Tannenbaum
8 min readJan 3, 2021


Immanuel Kant was an 18th century German philosopher whose synthesis of rationalism and empiricism, teleological view of human history, and deontological ethics, to name but a few of his contributions, had a tremendous influence on subsequent philosophy. Kant was born in 1724 in German Prussia to intelligent and deeply religious parents who raised him under Pietism: a sect of Christianity that emphasizes personal devotion to God and moral law. He was the fourth of nine children, but the eldest surviving. Kant received a strict, disciplinary education focused on religious instruction. After graduating, Kant moved on to the University of Königsberg.

Kant was young when his mother and father died: 13 and 22, respectively. After his father’s death Kant was forced to temporarily withdraw from University to work as a tutor to support himself. He spent nine years in the vocation before completing his degree in 1755. He then took up employment as a lecturer at the University of Königsberg, where he earned a reputation for being witty and erudite. Fifteen years later, he was appointed chair of logic and metaphysics, where he would remain until his death. Kant maintained a sharply regimented lifestyle throughout his life, with neighbors remarking that they set their clocks to his daily Philosopher’s Walk, as it came to be known. In 1804, after struggling with a prolonged illness, Kant passed away, uttering “It is good” as his final words.

Kant’s early thought is considered his “pre-critical” phase. The young Kant embraced the German rationalist tradition of Leibniz and Wolff, which crowned reason as the primary source of knowledge and asserted that using it alone, humans could come to know unobservable entities such as God and the soul.

This all changed when Kant encountered David Hume’s skepticism about the possibility of knowledge. Kant wrote that Hume awoke him from his “dogmatic slumbers” and, following his awakening, devised a new metaphysics that entails a collection of now-famous distinctions:

Phenomenal vs. noumenal: the phenomenal is the world of appearances, which humans encounter via their senses and understanding. The noumenal is the world in itself, which humans cannot access because it refers to how things are, unmediated by the human mind.

A priori vs. a posteriori: a priori is knowledge arrived at independently of experience. Take the equation 2 + 2 = 4. One does not have to physically witness two objects being joined with two other objects to know that adding two to two equals four. Contrast this with a posteriori knowledge, which is arrived at through empirical observations such as “Julie’s nails are red.” One cannot establish the color of Julie’s nails with reason alone; one must examine Julie’s nails with their own eyes to determine the color.

Analytic vs. synthetic: analytic judgments are judgments whose predicate is contained within its subject. Take the proposition “All bachelors are unmarried.” The definition of bachelor is “unmarried man.” The predicate “unmarried” is therefore contained within the subject “bachelor.” Synthetic judgments are judgments whose predicate is not contained within its subject, for instance, “All bachelors are tall.” The definition of bachelor does not include any information about height.

Kant’s big question is whether synthetic a priori knowledge — knowledge that is not self-evident yet is arrived at prior to experience — is possible. The viability of metaphysics hinges on the answer.

To overcome Hume’s skepticism Kant develops his theory of “transcendental idealism.” By transcendental, Kant means conditions that make experience possible. By idealism, Kant means reality as mind-dependent. Put together, Kant suggests that all humans possess concepts, such as space, time, and causality, that not only precede experience but cause and color it.

Two examples: we could not make sense of an object if we did not first possess the concept of extension: that an object has a definite shape, size, and limit. Similarly, we could not make sense of an event if we did not first possess the concepts of duration, cause and effect, and change.

Relatedly, we could not cognize experience without first recognizing ourselves as subjects separate from the objects of our experience. This is the centerpiece of Kant’s “transcendental deduction,” which identifies self-consciousness as a synthetic a priori concept.

With this, Kant achieves a “Copernican shift”: just as Copernicus turned astronomy on its head by suggesting that the Earth revolves around the sun and not the other way around, Kant turns epistemology on its head by declaring that knowledge is the source of experience rather than experience the source of knowledge.

Moving on to his conception of human affairs, Kant offers a teleological account of human history. To clarify, teleology is the study of purposes. It is derived from the Greek telos, meaning end, goal, or result. Those who view the world teleologically believe that all entities in the universe have an intrinsic function and that their purpose is to carry it out well. For instance, a chair provides a place to sit, a lung intakes oxygen, and so on for every object.

Kant asserts that humanity’s telos or purpose is the full development of its reason. His argument foreshadows Darwin’s evolutionary theory that species evolve traits that help them survive and reproduce. Kant remarks that unlike other animals, humans do not possess “the bull’s horns, the lion’s claws, nor the dog’s teeth.” Instead, we rely on reason for our survival, which, for example, helps us fashion tools and outsmart predators.

Humans also require reason to navigate internal conflicts. Kant describes the condition of humanity as “unsocial sociability”: On the one hand, we crave togetherness, as we derive growth and fulfillment from participating in a community. On the other hand, we desire individuality, as we wish to structure our environment in accordance with our own ideas. This creates a quandary: humans must live together to be happy yet often disagree about how to live, causing constant quarrelling. In Kant’s words, we “cannot bear” one another, but we “cannot bear to leave.”

Yet for all its inconvenience, this unsocial sociability is said to be the catalyst for humanity’s rational development. As people clash over how to live, they employ reason to persuade one another about civic disputes such as who to vest power in, which laws to support, and whether to enter into contracts. Humanity therefore advances as a rational species by working through its interpersonal conflicts. This view of antagonism as the motor of social development influenced Hegel, who devised the dialectic (thesis → antithesis → synthesis) to explain how reason develops overtime in his own writings on the rational development of history.

This development is said to have its own end: a civil, just international federation of states, which Kant calls a “league of nations.” Kant was a proponent of the Enlightenment, holding that as reason matured, humanity would increasingly reject the harmful institutions handed down by superstition and authority — religious dogma, militarism, colonialism, and economic exploitation — and instead utilize its own rational moral compass to establish benevolent relations among individuals and states.

Kant maintained that eventually, over many lifetimes, humanity would arrive at a perfect society; one in which standing armies are “totally abolished,” world citizenship is granted to every inhabitant of Earth, and a “perpetual peace” is attained. Note that to Kant, this vision is not merely utopian; it is the teleological destiny of the human race.

With regard to his ethics, Kant’s unique perspective begins with the premise that we as humans can be held morally responsible only if we have free will. If not, our actions are not actually our choice; they are entirely determined by preceding biological and environmental factors. In such a scenario, it is nonsensical to praise or blame what we do, as what we do is outside of our control.

This prompts a crucial question: is it possible to establish that free will exists, especially considering the fact that nature is causally determined?

Kant attempts to answer this question using his two-world hypothesis: while the world of appearances conforms to the principle of determinism (every effect has a cause that was itself determined by a previous cause), the world in-itself need not. Free will may exist in this noumenal world, and it is from there that we may feasibly derive it. Kant also points to the human conscience to justify belief in free will. For instance, if I see a $20 bill drop from a woman’s pocketbook, I am aware that I ought to return it to her. If I do not, and instead pocket it, I feel guilty for having chosen the wrong action. Kant cleverly notes that it is absurd to imagine that we possess a sense of moral duty that we are simultaneously incapable of fulfilling. Why would we feel obligated to return the money, and contrite about not returning it, if we had no choice in the matter, being predetermined not to return it?

Our conscience figures prominently in Kant’s ethical framework known as deontology. The term comes from the Greek deon or duty and suggests that humans, as rational free agents, are duty-bound to act in certain ways, irrespective of the personal benefits and/or harms these actions may confer. For instance, it is my duty not to steal, even if I am hungry.

Deontology is contrasted with consequentialism, which evaluates the morality of an action based on the outcomes it produces. Consider the example of theft in a time of hunger: although a thief may deprive a farmer of a small portion of his crop, she is now able to feed herself and her starving family, producing an overall benefit.

Kant believes consequentialism is a flimsy foundation on which to base morality. In this system, one will behave morally only as long as it is useful to them — as soon as it isn’t, they won’t. For instance, one may donate to charity because they enjoy the tax write-off. But if it goes away, they lose their incentive to give to others.

Kant sought out a moral principle that is not subject to such fickleness. What he devised is the “categorical imperative”: an ethical requirement of reason that holds true for everyone in all circumstances. Its first and most famous “universalizability” formulation is as follows:

“Act only according to that maxim whereby you can at the same time will that it should become a universal law.”

Kant uses the example of stealing to illustrate this principle. Theft requires the existence of private property. But if everybody stole, private property couldn’t exist, as no one would have anything left to steal. Thus, stealing would be rendered impossible. This contradiction imposes a “perfect” duty on all rational moral agents not to steal. (Note: there are also “imperfect” duties that allow more leeway in when and how they may be carried out. Kant cites helping others as an example of an imperfect duty.)

Kant promotes two additional formulations of the categorical imperative rooted in “humanity” and “autonomy,” respectively. The former demands that we respect all humans’ subjectivity, treating them “never merely as a means to an end, but always at the same time as an end.” The closely related latter emphasizes our role as rational, autonomous law-givers who self-impose universal rules that preserve freedom and prevent coercion, exploitation, and other violations of our subjectivity.

The categorical imperative is meant to encourage “the moral strength of human beings’ will in fulfilling their duty” and make it so that happiness is no longer pursued undeservedly, at the expense of others, but rather in lockstep with virtue. (As a sidebar, Kant holds that as aesthetically minded beings we can also derive virtue from the arts.) For Kant, there is nothing more important than cultivating virtue and happiness in tandem, as the two “together constitute the position of the highest good in a person.”