 Critical engagement with the origins and conceptualization of subjectivity also informs poststructuralist challenges to identity politics. They charge that it rests on a mistaken view of the subject that assumes a metaphysics of substance—that is, that a cohesive, self-identical subject is ontologically (if not actually) prior to any form of social injustice (Butler 1999 [1990]). This subject has certain core essential attributes that define her or his identity, over which are imposed forms of socialization that cause her or him to internalize other nonessential attributes. This position, they suggest, misrepresents both the ontology of identity and its political significance. The alternative view offered by poststructuralists is that the subject is itself always already a product of discourse, which represents both the condition of possibility for a certain subject-position and a constraint on what forms of self-making individuals may engage in. There is no real identity—individual or group-based—that is separable from its conditions of possibility, and any political appeal to identity formations must engage with the paradox of acting from the very subject-positions it must also oppose. Central to this position is the observation that any claim to identity must organize itself around a constitutive exclusion: