This paper explores how social psychology has theorized the relationship between the individual and society. This is done through a genealogical analysis of the Social Identity Tradition (SIT). It is argued that the current state of SIT is profoundly shaped by a range of intellectual and moral strategies derived from the work of Henri Tajfel. This 'Tajfel effect' manifests itself as a way of settling theoretical, practical and moral disputes through the invocation of Tajfel as a founding figure. However, this strategy also ties SIT into a model of the subject and an understanding of society that is increasingly seen as problematic. The paper then goes on to show how a range of core concepts at the heart of SIT may be usefully reformulated by drawing on the work of Deleuze and Guattari. Their work offers SIT a way of thinking about individuals and groups as sites for connection and differentiation. This is illustrated using the example of Nazi social relations that was originally deployed by Tajfel. Potential issues and direction for SIT as reinvigorated by the encounter with Deleuze and Guattari are then sketched out.