Immanuel Kant's Groundwork of the Metaphysics of Morals ranks alongside Plato's Republic and Aristotle's Nicomachean Ethics as one of an influential work in moral philosophy. Its aim is to search for and establish the supreme principle of morality, the categorical imperative. He 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. The introduction examines and explains Kant's argument.