Groundwork of the Metaphysics of Morals (German: Grundlegung zur Metaphysik der Sitten; 1785; also known as the Foundations 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. Kant conceives his investigation as a work of foundational ethics-one that clears the ground for future research by explaining the core concepts and principles of moral theory and showing that they are normative for rational agents. Kant aspires to nothing less than this: to lay bare the fundamental principle of morality and show that it applies to us. In the text, Kant provides a groundbreaking argument that the rightness of an action is determined by the character of the principle that a person chooses to act upon. Kant thus stands in stark contrast to the moral sense theories and teleological moral theories that dominated moral philosophy at the time he was writing. Central to the work is the role of what Kant refers to as the categorical imperative, the concept that one must act only according to that precept which he or she would will to become a universal law. 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 book is famously obscure, and it is partly because of this that Kant later, in 1788, decided to publish the Critique of Practical Reason. In the preface to the Groundwork Kant motivates the need for pure moral philosophy and makes some preliminary remarks to situate his project and explain his method of investigation. Kant opens the preface with an affirmation of the ancient Greek idea of a threefold division of philosophy into logic, physics, and ethics. Logic is purely formal-it deals only with the form of thought itself, not with any particular objects. Physics and ethics, on the other hand, deal with particular objects: physics is concerned with the laws of nature, ethics with the laws of freedom. Additionally, logic is an a priori discipline, i.e., logical truths do not depend on any particular experience for their justification. By contrast, physics and ethics are mixed disciplines, containing empirical and non-empirical parts. The empirical part of physics deals with contingently true phenomena, like what kind of physical entities there are and the relations in which they stand; the non-empirical part deals with fundamental concepts like space, time, and matter. Similarly, ethics contains an empirical part, which deals with the question of what-given the contingencies of human nature-tends to promote human welfare, and a non-empirical part, which is concerned with an a priori investigation into the nature and substance of morality. Because it is a priori Kant calls this latter, non-empirical part of ethics "metaphysics of morals." It corresponds to the non-empirical part of physics, which Kant calls "metaphysics of nature."