Content externalism implies first, that there is a distinction between concepts and conceptions, and second, that there is a distinction between thoughts and states of mind. The implications require us to rethink the nature of self-knowledge. In this paper, I argue for the partial-representation theory of self-knowledge, according to which the self-ascription of a thought is authoritative when it is based on a conscious, occurrent thought in virtue of which it partially represents an underlying state of mind. The model of self-knowledge I provide accommodates the distinction between concepts and conceptions and the distinction between thoughts and states of mind, and it also offers a middle path between absolute epistemic security on the one hand, and scepticism about first-personal self-knowledge on the other.