In his Critique of Practical Reason, Kant argues that moral agents have a duty to promote the highest good, a state of affairs that involves a proportionality or harmony between two heterogeneous elements: virtue and happiness. He also argues that this duty to promote the highest good leads to a difficulty, for if we limit our perspective to the realm of appearances, there seems to be no ground that could possibly guarantee the requisite connection between virtue and happiness: morally good people suffer, and morally bad people prosper. Thus it seems that we are morally obligated to promote the highest good, but unable to do so through our own acts of willing. Kant calls this problem an antinomy of practical reason. His solution involves the three postulates of practical reason—God, freedom, and immortality. Many questions related to Kant’s conception of the highest good have received significant scholarly attention. These questions also played a central role in the development of post-Kantian ethics. Yet the scholarly literature on post-Kantian conceptions of the highest good is comparatively meager. My aim is to fill this lacuna and to show how Fichte, Schelling, and Hegel develop fundamental aspects of their ethical views in response to problems that arise in connection with Kant’s conception of the highest good.