Immanuel Kant 
On The Metaphysics of Morals and Ethics 
Groundwork of the Metaphysics of Morals, Introduction to the Metaphysic of Morals, The Metaphysical Elements of Ethics

Collected here in this omnibus edition are Immanuel Kant’s three most important works on the Metaphysics of Morals and Ethics. Included are Kant: Groundwork of the Metaphysics of Morals, Introduction to the Metaphysic of Morals, and The Metaphysical Elements of Ethics. Kant’s Fundamental Principles of the Metaphysics of Morals is one of the most important works in modern moral philosophy. It belongs beside Plato, Aristotle, Machiavelli, and Hobbes. Here Kant sets out to articulate and defend the Categorical Imperative – the fundamental principle that underlies moral reasoning – and to lay the foundation for a comprehensive account of justice and human virtues. In Introduction to the Metaphysic of Morals Kant states: "All duties are either duties of right, that is, juridical duties, or duties of virtue, that is, ethical duties. Juridical duties are such as may be promulgated by external legislation; ethical duties are those for which such legislation is not possible." In The Metaphysical Elements of Ethics states: "If there exists on any subject a philosophy (that is, a system of rational knowledge based on concepts), then there must also be for this philosophy a system of pure rational concepts, independent of any condition of intuition, in other words, a metaphysic. It may be asked whether metaphysical elements are required also for every practical philosophy, which is the doctrine of duties, and therefore also for Ethics."