The Foundations of the Metaphysics of Morals or Groundwork of the Metaphysics of Morals (German: Grundlegung zur Metaphysik der Sitten, 1785), Immanuel Kant's first contribution to moral philosophy, argues for an a priori basis for morality. Where the Critique of Pure Reason laid out Kant's metaphysical and epistemological ideas, this relatively short, primarily meta-ethical, work was intended to outline and define the concepts and arguments shaping his future work The Metaphysics of Morals. However, the latter work is much less read than the Groundwork.
The Groundwork is notable for its explanation of the categorical imperative, which is the central concept of Kant’s moral philosophy.
The Groundwork is broken into a preface, followed by three sections. Kant's argument works from common reason up to the supreme unconditional law, in order to identify its existence. He then works backwards from there to prove the relevance and weight of the moral law. The third and final section of the book is famously obscure, and it is partly because of this that Kant later, in 1788, decides to publish the Critique of Practical Reason.
— Excerpted from Wikipedia, the free encyclopedia.