There is an interpretative puzzle at the centre of Kant’s Groundwork for the Metaphysics of Morals. The text presents the single principle of morality (G, 4: 392), but instead of providing a definitive statement of the principle, we find a three-step sequence of formulas. The puzzle concerns the formula relation: given the contrast between the moral law’s individuality and the plurality of formulas, how do the formulas relate to each other and the moral law? This paper takes the first step (...) towards a new account by focusing on G, 4: 436, a passage in which Kant makes claims about the matter and form of the moral law. By understanding the hylomorphism entailed by these claims, it is possible to achieve new perspectives on common questions about Kant’s ethics, in particular, the role of the formulas in deriving or explaining duties and how the formulas are used in the argument of Groundwork II and its transition from popular moral philosophy to metaphysics of morals. (shrink)