I argue that having a theory of mind requires having at least implicit knowledge of the norms of the community, and that an implicit understanding of the normative is what drives the development of a theory of mind. This conclusion is defended by two arguments. First I argue that a theory of mind likely did not develop in order to predict behavior, because before individuals can use propositional attitudes to predict behavior, they have to be able to use them in explanations of behavior. Rather, I suggest that the need to explain behavior in terms of reasons is the primary function of a theory of mind. I further argue that in order to be motivated to offer explanations of behavior, one must have at least an implicit understanding of appropriate behavior, which implies at least an implicit understanding of norms. The second argument looks at three cases of nonhuman animal societies that appear to operate within a system of norms. While there is no evidence that any species other than humans have a theory of mind, there is evidence that other species have sensitivity to the normative. Finally, I propose an explanation for the priority of norms over a theory of mind: given an understanding of norms in a society, and the ability to recognize and sanction violations, there developed a need to understand actions that violated the norms, and such explanations could only be given in terms of a person's reasons. There is a significant benefit to being able to explain behavior that violates norms, because explanations of the right sort can also serve to justify behavior.