The categorical imperative

Last lesson we found that moral worth lives in the maxim — the principle your will acts on. But which maxims are permissible? Kant answers with a single supreme principle from which every particular duty can be derived. He calls it the categorical imperative. To see what makes it special, first meet its opposite number.

An imperative is just a command reason issues to a will that doesn’t automatically obey — a formula for what we ought to do. Kant says imperatives come in two kinds. A hypothetical imperative commands an action as a means to an end you happen to want: “If you want to be healthy, exercise.” Its force is entirely borrowed from the end. Stop wanting the end and the command evaporates.

A categorical imperative is totally different. It commands an action as objectively necessary in itself, without reference to any further end — unconditionally. It does not say “if you want happiness, be honest.” It says: be honest, full stop, whether or not honesty gets you anything. This, Kant argues, is the form every genuinely moral command must take, because morality binds a rational being as such, not merely as a being who happens to have this or that desire.

Kant claims there is really only one categorical imperative, but he states it in several formulas meant to bring the same principle closer to intuition. The first — the Formula of Universal Law — reads: Act only according to that maxim whereby you can at the same time will that it should become a universal law.

Here is the procedure. Take the maxim you are actually about to act on. Universalize it — imagine it as a law that everyone follows, always, automatically. Then ask: can I still coherently will that world? If universalizing the maxim destroys itself, or something I must rationally will, the maxim is forbidden.

Some maxims survive that first test but fail a second, subtler one. Consider a comfortable person whose maxim is “I’ll never help anyone in need; let each fend for himself.” You can coherently imagine a world where nobody ever helps anybody — no contradiction in conception; humanity would grind on grimly. But can you consistently will it? Kant says no: as a needy, dependent creature you inevitably will that others help you when you’re desperate — so to will universal non-help is to will against your own rational needs. That is a contradiction in the will, and it violates an imperfect (wide) duty.

Kant’s second great formula shifts the angle from law to persons. The Formula of Humanity (the End in Itself): Act so that you treat humanity, whether in your own person or in that of another, always at the same time as an end, and never merely as a means.

Why do rational beings get this special status? Because, unlike tools and objects — which have value only as means to our ends — a rational being sets ends of its own. It is a source of value, not just a bearer of it. So a rational being exists as an end in itself, something whose worth is not up for trade. To ignore that, to reduce a person to a mere instrument, is the core moral wrong.

Crucially, the formulas are meant to be versions of one and the same principle, not a menu of separate rules. Universalizing a maxim (Formula of Universal Law) and refusing to treat any rational being as a mere means (Formula of Humanity) are two ways of expressing the single demand of practical reason. They should, Kant holds, always agree in their verdicts — the false promise fails both — and they set up the third formula, autonomy, which the next lesson takes as its keystone.