A philosophical account of personal identity - in terms of the maintenance of fundamental beliefs, principles and commitments by spatiotemporally continuous particulars - is sketched, an account which is able to incorporate a social and relational conception of personal identity, and thus serve as the basis for a social psychological theory of personal identity - in terms of the pursuit of identity projects’within social collectives. Some implications of this theory are developed, concerning the relation between identity and individualism, responsibility and social labeling. The theory develops an account of the social constitution of personal identity that is consistent with a realist conception of social psychological theories of identity: as objective theoretical descriptions of the social dimensions of identity.