When post-structuralism is applied to social theory, its epistemology contributes some new perspectives on agency and structure, change and continuity (Game 1991; Fox 1993). In particular, it contributes an understanding of the relationship between ‘power’ and ‘knowledge’, of the discursive construction of the self as opposed to a more essential conception, and a recognition of difference and diversity both as (dis)organising principles and as the basis for ethics and politics (Haber 1994). It would be fair to say that the impact of post-structuralism and postmodern philosophy within social theory has been dominated over the past decade by the position developed by Michel Foucault (Valverde 1991: 184; Lupton 1994: 5), a claim borne out by the contributions to this volume. However, closer examination of this ‘sociological Foucault’ which emerges in Foucauldian studies suggests that – while the epistemology has been embraced and used productively – the full complexities of the ontological implications of the de-centring of self and the ‘deep structure’ conception of the rules of discursive formation deserve closer attention. Part of this chapter will be devoted to such explorations.