In Purity and Danger, Douglas theorizes purity and impurity in terms of the instantiation and disruption of a shared symbolic order. Purity/impurity discourses act, according to Purity and Danger, as a homeostatic system which ensures the preservation of this social whole, generally encoding that which threatens social equilibrium as impurity. There have been calls for new social theory on this 'under-theorized' topic. Presenting such further reflections, I argue that Douglas' account is less a full explanation than a regularity. Representations of purity are only secondarily symbols of the social order. Rather, purity/impurity discourses are only associated with 'matter out of place' when phenomena are assessed for their relative deviation from an imputed state of 'self-identity': qualitative homogeneity and correspondence with their essence. Purity and impurity do more than judge self-identity, however. They can play a fundamental role in its performative construction; they are well adapted for smuggling assumptions into our discourses regarding the essence of particular phenomena and forms of subjectivity, simplifying a complex world into a stark contrast between the dangerous and the innocent, the valuable and the valueless, the necessary and the contingent, the originary and the prosthetic, the real and the apparent, and the unitary and the fragmented. © The Author(s) 2013.