Fundamental Principles of the Metaphysic of Morals

In this foundational work the author sets out to clarify what it means to ground ethics in pure reason rather than in everyday experience. By tracing the ancient division of philosophy into physics, ethics, and logic, he shows how each field rests on distinct principles—material knowledge of objects versus formal knowledge of thought itself. The text argues that while natural science can blend empirical observation with rational analysis, moral philosophy must be stripped of empirical elements to reveal the universal laws that govern freedom and duty.

Through careful distinctions between the laws that describe how things happen and those that prescribe how they ought to happen, the author introduces a “metaphysic of morals” that seeks a priori certainty. He explores the idea that true moral obligations, such as the prohibition against lying, carry an absolute necessity that applies to all rational beings. The early chapters invite listeners to reconsider the role of pure reason in shaping ethical life, laying the groundwork for a rigorous, systematic approach to morality.