(De. Grundlegung zur Metaphysik der Sitten). Published 1785. Often translated as Fundamental Principles of the Metaphysics of Morals.

Immanual Kant's introduction to his Critical moral theory, further expounded in the Critique of Practical Reason (1788) and the Metaphysics of Morals (1797).

In the Groundwork, Kant derives the idea of the Categorical Imperative. According to Kant, an action can have moral value only if it is done from duty alone and not for some goal. Such actions are called `categorical' (as opposed to `hypothetical'). The Categorical Imperative subsumes all such imperatives (`ought-to' statements). One statement of it, the ``Formula of Universal Law'', is:

Act only on that maxim through which you can at the same time will that it should become a universal law.

Note that the Groundwork is not itself a system of morals. Rather, it (like Kant's Critiques) states the conditions under which such a system is possible, and defines the bounds of such a system. Kant did write ``Die Metaphysik der Sitten'', which does to some extend expand the Categorical Imperative into particular imperatives.