Chapter two reviews Kant’s philosophical approach to show how the nature of ethics and its relation to other aspects of his philosophy point toward moral idealism and metaphysical naturalism. Philosophical and each of its parts are understood as unified by an idea that identifies the relevant domain and structure. Philosophy’s domain is the ends of human reason. Its structure is divided in several ways, the most important being critique and system, pure and empirical, and practical and theoretical. A look at the first two divisions shows how the critical method of transcendental argument defends pure cognition in a methodologically anti-naturalistic way; these pure a priori cognitions apply within nature and along with empirical cognitions provide a metaphysically naturalistic ontology. A parallel transcendental grounding can hold for ethics, precluding the need for any non-naturalist metaphysics. The third division between practical and theoretical can be understood in many ways: is/ought, nature/morality, given versus creating objects, and knowledge/action. I show how these work together to divide the domain of philosophy into theoretical knowledge of nature as given and practical moral action creating and pursuing ends. Free acts understood from the agent-perspective thus form the domain of ethics itself. The practical thus prima facie suggests no ontology.