The Fundamental Principles of the Metaphysic of Morals - Immanuel Kant

The Fundamental Principles of the Metaphysic of Morals, also known as The Groundwork of the Metaphysics of Morals or Foundations of the Metaphysics of Morals or Grounding of the Metaphysics of Morals, is Immanuel Kant's first contribution to moral philosophy. It 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 readable than the Fundamental Principles. (Summary from Wikipedia)