The aim of this chapter is to arrive at an understanding of Fichte’s metaethics that integrates two parallel accounts of what he variously called the “instinct of reason” (in the Wissenschaftslehre nova method lectures, 1796–1798) and our “moral nature” (in the System of Ethics of 1798). The chapter first characterizes Fichte’s metaethics as theoretical (i.e., not directly concerned with practical deliberation or action) and idealist (i.e., as avoiding both naturalist and supernaturalist metaphysics along with causal explanation in general). While it is accurate to label Fichte’s approach “transcendental,” the chapter argues that both accounts ultimately introduce a theological element, namely, the idea of God. The role of God turns out to be a “necessary idea” within Fichte’s genetic explanation of our moral nature, without reducing to any form of supernaturalist metaphysics.