Groundwork of the Metaphysic of Morals (also known as the Foundations/Fundamentals of the Metaphysics of Morals, Grounding of the Metaphysics of Morals and the Grounding for the Metaphysics of Morals) is the first of Immanuel Kant's mature works on moral philosophy and remains one of the most influential in the field. It 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, decided to publish the Critique of Practical Reason.