There is, therefore, only one categorical imperative. It is: Act only according to that maxim by which you can at the same time will that it should become a universal law.

Kant formulates this principle in the Groundwork of the Metaphysics of Morals (1785), written during the mature phase of his critical philosophy. In the Groundwork he aims to identify the supreme principle of morality not from theology, custom, or empirical psychology, but from pure practical reason. The passage occurs as Kant distinguishes hypothetical imperatives (conditional rules for achieving ends) from the categorical imperative (an unconditional command binding on any rational agent). He presents the “universal law” formulation as the fundamental test for whether a proposed maxim of action can count as morally permissible.

The quote states Kant’s core idea that moral requirements are grounded in rational consistency and universality. To act morally is to act on a maxim you could coherently will everyone to follow as a law—without contradiction or self-defeat. This makes morality impartial: one may not exempt oneself from rules one expects others to obey. The test also shifts ethics from outcomes to principles: an action’s rightness depends on whether its guiding maxim can be universalized, not on predicted consequences. In Kant’s system, this expresses autonomy: rational agents legislate moral law for themselves through reason, rather than being driven by inclination or external authority.

1) “Act only on that maxim through which you can at the same time will that it should become a universal law.”
2) “Act only according to that maxim whereby you can at the same time will that it should become a universal law.”
3) “So act that the maxim of your will could always hold at the same time as a principle of universal legislation.”