How the nature of expression constitutes a problem for expressivism

Expressivism in ethics is the view that moral language functions to express only the conative mental states of speakers. After distinguishing between two different senses of expression, and three different ways in which the expressivist might account for the expressive function of moral language, I explain that expressivists owe us an account of how it is that speakers express their mental states by making moral claims. Then I go on to develop just such an account, and in the end, the account puts expressivists in an awkward position. For if my account of expression is on point, then either (a) expressivists are committed to saying that competent users of moral language are often confused (perhaps even systematically so) about their own mental states and their own reasons for action, or (b) expressivism is false