The task of social psychology is to explain the flexibility of human beings in creating and relating to their social worlds. Social identity and self-categorization theories provide a thoroughgoing interactionist framework for achieving such a task. However, in order to do so, it is necessary to avoid reductionist misreadings of the theories that would explain human social action simply by reference to psychological processes, without examining how the play of process depends on the cultural and structural settings in which they occur. More specifically, to the extent that self-categories shape social action, flexibility is achieved through the categories to which we belong, the others with whom we compare ourselves, and the dimensions along which such comparisons occur. These are not a fixed aspect of the human condition but are a focus for argument precisely because of their world-making consequences.