Recent epistemology has focused almost exclusively on propositional knowledge. This paper considers an underexplored area of epistemology, namely knowledge of persons: if propositional knowledge is a state of mind, consisting in a subject's attitude to a (true) proposition, the account developed here thinks of interpersonal knowledge as a state of minds, involving a subject's attitude to another (existing) subject. This kind of knowledge is distinct from propositional knowledge, but it exhibits a gradability characteristic of context-sensitivity, and admits of shifty thresholds. (...) It is supported by a wide range of unexplored linguistic data and intuitive cases; and it promises to illuminate debates within epistemology, philosophy of religion, and ethics. (shrink)