Immanuel Kant's Groundwork of the Metaphysics of Morals ranks alongside Plato's Republic and Aristotle's Nicomachean Ethics as one of the most profound and influential works in moral philosophy ever written. In Kant's own words its aim is to search for and establish the supreme principle of morality, the categorical imperative. Kant argues that every human being is an end in himself or herself, never to be used as a means by others, and that moral obligation is an expression of the human capacity for autonomy or self-government. This edition presents the acclaimed translation of the text by Mary Gregor, together with an introduction by Christine M. Korsgaard that examines and explains Kant's argument.