 Because practices are so general and play so many roles in these theories, it is a challenge to interpret them from the perspective of social ontology. It is hard to tease apart different kinds of ontological claims they make, and also hard even to know when these theories are making an ontological claim, as opposed merely to telling a narrative of causal influence. Some theories of practice insist on the importance of material routines in the world, and yet return to mentalistic-sounding accounts of the conceptual creation of the social world. The centerpiece of Bourdieu 1972 [1977], for instance, is the claim that social practice is generated by a “habitus”—a mentally internalized system of discrimination and perception, embodied as dispositions. (See also Ortner 1984).