This dissertation investigates the morpho-syntactic makeup of personful expressions in natural language; special focus is given to referential uses of personal pronouns. The central thesis guiding the inquiry is that utterance contexts, which serve to fix the semantic values of person indexicals, are specifically a kind of centered situation. This treatment of contexts puts restrictions on what kinds of person features are definable, and the resulting inventory of such features (in conjunction with independently-motivated pragmatic constraints on the use of referential expressions) provides a novel explanation for the typology of person systems.