How can expressivists make sense of the practice of communication? If communication is not a joint enterprise aimed at sharing information about the world, why do we engage in communication the way we do? Call this *the problem of communication*. Starting from basic assumptions about the rationality of speakers and the nature of assertion, we argue that speakers engaging in conversation about normative matters must presuppose that there is a unique normative standard on which the attitudes of conversational participants ought to converge. This gives the beginning of a solution to the problem of communication on behalf of expressivists.