29 September 2026 · Ethics and the State

Kant on Duty, the Moral Law, and Treating People as Ends

Immanuel Kant published the Groundwork of the Metaphysics of Morals in 1785. Where Bentham measures right and wrong by pleasure and pain, Kant builds his whole approach on reason alone. He wants a standard for morality that holds for any rational being anywhere, not just for creatures built like us to feel pleasure and pain in certain ways, and that holds absolutely, not just when it happens to serve someone's interest. The assigned reading picks up near the end of Kant's first section, already past his opening discussion of the good will, and then covers the whole of his second section along with the opening pages of his third section.

Why common ideas of duty are not enough

The portion of the first section included here is Kant explaining why he cannot simply rest his case on ordinary moral experience. He points out that we can never be fully certain, even about our own actions, whether we really acted from duty or whether some hidden form of self interest was doing the work instead. Since we cannot inspect our own motives with full certainty, and since a true moral law has to hold for every rational being without exception, Kant concludes that morality cannot be built up from examples or from human psychology at all. It has to be worked out independently, by reason alone, before being applied back to human life.

Imperatives, and the difference between hypothetical and categorical

Kant opens the second section by defining the will as practical reason, the capacity to act according to principles rather than by instinct alone. When reason does not automatically control the will, as is normal for human beings, objective rational principles appear to us as commands, which Kant calls imperatives. He sorts these into two basic kinds. A hypothetical imperative tells you what to do only on the condition that you want some further goal, such as a doctor's advice for keeping a patient healthy, valid only if health is actually wanted. A categorical imperative commands an action as necessary in itself, with no further condition attached at all.

Kant further splits hypothetical imperatives into imperatives of skill, which apply to any possible goal a person might have, and imperatives of good sense, which apply to the one goal he thinks every person actually has by nature, their own happiness. He argues that happiness turns out to be a surprisingly unstable goal to build rules around, since nobody can say with certainty what would make them fully happy across their whole life, so even that kind of advice can only be loose rather than a strict command. Only the categorical imperative, in Kant's view, counts as a real law, since law requires unconditional necessity, not advice that depends on what a person happens to want.

The formula of universal law

Kant then asks what a categorical imperative could possibly look like, given that it cannot be based on any particular goal. His answer is that only the bare form of lawfulness itself is left once every specific goal is stripped away. This gives his first formula: act only on that principle through which you can at the same time will that it become a universal law. The personal rule behind an action, the private reason a person is actually acting on, is what Kant calls a maxim.

He tests this formula with four examples. A person considering suicide out of despair is asked whether a principle of ending one's own life out of self love could be willed as a universal law of nature, and Kant argues it could not, since a law built on self love that destroys life contradicts the very feeling that is supposed to preserve life. A person who wants to borrow money on a promise they know they cannot keep is asked whether lying promises could become a universal law, and Kant argues that if everyone made promises they had no intention of keeping, the practice of promising itself would collapse, so the principle defeats itself the moment it is made universal. A talented person who would rather enjoy comfort than develop their abilities is asked whether neglecting one's talents could be willed as a universal law, and Kant says it is not strictly self contradictory, but no rational being could actually will it, since reason also wants its own capacities developed for all the various purposes they might serve. A prosperous person who refuses to ever help anyone in need is asked whether indifference to others could be a universal law, and again Kant says such a world is possible to imagine, but no one could rationally will it, since anyone might someday need the help of others themselves.

The first two, he says, violate strict duty, since the maxim cannot even be conceived as universal without contradiction. The second two violate only looser duty, since the maxim could be universal but not rationally willed.

The formula of humanity

Kant then develops a second version of the same basic law. He argues that if there is going to be a supreme principle of morality at all, it must rest on something of absolute, unconditional worth, something that cannot be just a means to some further end. He locates that thing in rational beings themselves. Every person, as a rational being, exists as an end, not merely as a tool for someone else's purposes, which gives the formula: act so as to treat humanity, whether in your own person or in that of anyone else, always as an end, never merely as a means.

He runs the same four examples through this version. Suicide treats one's own person merely as a means to escape a painful situation, rather than as an end in itself. A lying promise treats the other party merely as a means, since they cannot actually agree to a method of being deceived. Neglecting one's own talents fails to actively support humanity as an end in oneself, even if it does not outright attack it. Refusing to help others fails to support their ends as a rational being would want their own ends supported, even though it does not violate anyone's rights outright. Kant is careful to separate this formula from the simpler golden rule, arguing that the golden rule is only a narrower version of his principle and cannot, on its own, explain duties to oneself or duties to actively help others.

Autonomy and the kingdom of ends

From these two formulas, Kant draws out what he treats as their deeper foundation: autonomy, the idea that a truly moral will is not obeying a law handed to it from outside, but is itself the author of the law it follows. He contrasts this with heteronomy, where the will is governed by something external to itself, whether that is inclination, self interest, or any outside authority, including even the will of God understood as an external command. Any moral theory built on heteronomy, in Kant's framework, can only ever produce conditional requirements, never a genuine, unconditional duty.

This idea of self rule leads Kant to picture what he calls a kingdom of ends, an imagined community in which every rational being is treated as making the moral law and also as being bound by it, so that no one is used merely as someone else's tool. He explains that in such a kingdom, things have either a price, meaning they can be traded for something else of equal value, or a dignity, meaning they are beyond all price and admit no substitute. Skill and cleverness have a price. Fidelity to one's word and genuine goodwill toward others have dignity, because their worth lies entirely in the disposition behind them, not in any use they happen to produce. Morality itself, Kant concludes, is what gives a rational being this kind of dignity, since only a moral being can be a self legislating member of this kind of kingdom.

He closes the second section by restating these three formulas, universal law, humanity as an end, and autonomy within a kingdom of ends, as different ways of presenting the exact same underlying law, chosen to make the same idea easier to grasp from different angles rather than to introduce anything new.

Opening the question of freedom

The brief excerpt from the third section that follows introduces the next problem Kant sets for himself: showing that this categorical imperative is not just a logical requirement but something a rational being is actually bound by. He connects this directly to freedom, defining it, in a first pass, as the capacity of the will to act independently of being determined by outside causes, and then starts to work out a fuller sense of freedom tied to a will giving laws to itself.

Why this still matters

Reading this against Bentham is the clearest way to see what is actually at stake. Bentham wants one measurable yardstick, pleasure against pain, that settles moral and legal questions by calculation. Kant wants the opposite: a standard that holds regardless of consequences, pleasure, or anyone's personal wants, because he thinks grounding morality in anything that variable, including feelings or self interest, can never produce a genuine, unconditional duty. That disagreement, a test built on outcomes against a test built on the form of the principle itself, is still one of the central fault lines in how people argue about ethics today.

Source: Immanuel Kant, Groundwork of the Metaphysics of Morals (1785), the closing portion of the First Section, the complete Second Section (covering imperatives, the formula of universal law with its four examples, the formula of humanity, autonomy, heteronomy, and the kingdom of ends), and the opening pages of the Third Section, through the first discussion of freedom as a form of causality.