In the Preface of Groundwork of the Metaphysics of Morals, Kant presents his plans for his book and explains why establishing a metaphysics of morals is necessary. While he acknowledges he will not be able to accomplish this task in one book, he hopes to lay the foundation for future work on the subject and prove “the identification and corroboration of the supreme principle of morality” (7, 4:392). Kant’s background in the sciences is evident here, as he lays out his plans for both the text and the development of philosophy as a field with methodical precision.

Kant explains he will borrow from three divisions of Ancient Greek sciences: physics, ethics, and logic. Laws of nature correspond to physics, principles of freedom are examined through ethics, and formal philosophy is ruled by logic. Philosophical ideas are classified as either “empirical” or “pure.” Empirical philosophy is guided by everyday human experience, and pure philosophy is defined by its capacity to utilize logic and a priori cognition. If a principle is grounded by a priori reasoning, it is understood through intuition alone and without any justification from personal experiences. Knowledge of these distinctions can help us understand what Kant means by metaphysics: pure philosophy directed toward a better understanding of the world around us.