This article develops a constitutive account of self-knowledgethat is able to avoid certain shortcomings of the standard response to the perceived prima facieincompatibility between privileged self-knowledge and externalism. It argues that ifone conceives of linguistic action as voluntary behavior in a minimal sense, one cannot conceive ofbelief content to be externalistically constituted without simultaneously assuming that the agent hasknowledge of his beliefs. Accepting such a constitutive account of self-knowledge does not, however,preclude the conceptual possibility of being mistaken about one’s mental (...) states. Rather, self-knowledgehas to be seen as only a general constraint or as the default assumption of interpreting somebodyas a rational and intentional agent. This is compatible with the diagnosis of a localized lack of self-transparency. (shrink)