In this dissertation I present an account of what we mean when we make ethical claims and of why we have reason to be ethical. I argue that we can analyze ethical concepts in terms of the rationality of certain motivational states. We can, for instance, analyze good outcomes as outcomes we should desire, and we can analyze wrongful acts as acts we should feel obligated not to perform. I proceed to argue that having reason to perform an act is a matter of the act’s contributing to an end at which we should aim - an end, that is, that we should be motivated to bring about. Since ethical judgments are judgments about how we should be motivated, and how we should be motivated determines what we should do, it is actually a conceptual truth t...