Kant's Categorical Imperative and the Formula of Universal Law

Immanuel Kant (1724–1804) laid out the foundations of his moral philosophy in the Groundwork of the Metaphysics of Morals (Grundlegung zur Metaphysik der Sitten, 1785), a short but dense treatise written while Kant held the chair of logic and metaphysics at the University of Königsberg. Kant's central innovation is the distinction between hypothetical imperatives, which command an action only conditionally, as a means to some desired end ("if you want X, do Y"), and the categorical imperative, which commands unconditionally, simply in virtue of one's status as a rational agent, independent of any particular desire or goal. Moral requirements, for Kant, must take the form of categorical imperatives, since a genuinely moral duty cannot depend on whether an agent happens to want a given outcome; a promise-keeping norm that bound only those who wanted its consequences would not be a moral law at all, merely a rule of prudence.