"Self-knowledge" is commonly used in philosophy to refer to knowledge of one's particular mental states, including one's beliefs, desires, and sensations. It is also sometimes used to refer to knowledge about a persisting self -- its ontological nature, identity conditions, or character traits. At least since Descartes, most philosophers have believed that self-knowledge is importantly different from knowledge of the world external to oneself, including others' thoughts. But there is little agreement about what precisely distinguishes self-knowledge from knowledge in other (...) realms. Partially because of this disagreement, philosophers have endorsed competing accounts of how we acquire self-knowledge. These accounts have important consequences for the scope of mental content, for mental ontology, and for personal identity. (shrink)