  Fortunately we do not ordinarily need to turn to a metaethical theory to tell us what reasons we have. People have a robust set of intuitions about what is and what is not a reason for a given agent to perform a given action. All nontrivial versions of reasons internalism and externalism have substantive implications concerning the extension of agents’ reasons, and for the most part theory here is answerable to common sense and aims at accommodating it. Some of the most significant and compelling arguments for and against versions of internalism are therefore extensional, that is to say, based on what reasons agents actually have. An internalist account’s predictions about what is and what is not a reason for a particular agent can be tested against our prior judgments about what reasons there are.