This dissertation is an enquiry into normative authority-that is, the enquiry into reasons. The project is motivated by a collection of tensions. I accept a variety of naturalism; however, this leads straightforwardly to a problem: I see no place for normative reasons in a naturalistic framework. Certain non-negotiable platitudes of normative authority cannot be satisfied on a naturalistic view of the world. If anything were to satisfy the platitudes about reasons, it would have to belong to a non-natural dimension of the world. However, I doubt that we could be connected to such entities in any significant way. This line of reasoning has led me to skepticism about reasons. And, since reasons seem to play such a large role in our lives, this skeptical thesis requires a defensible error theory. I will undertake the project of motivating my skeptical position and providing an error theory of reasons. The section headings below roughly correspond to the sections of the following work.