 The “level of the social” is often divided from other “lower levels” in arrangements of the sciences into hierarchies (Comte 1830–1842, Oppenheim and Putnam 1958). This arrangement of the sciences into levels is sometimes challenged altogether (e.g., Wimsatt 1976, Thalos 2013). But even if certain domains of science can be arranged into levels, the level of the social has difficulties unique to it. One is the problem of identifying just which entities are the social ones. Even cases that would seem straightforward can be contentious. A crowd, for instance, was regarded by many in the late nineteenth century as the paradigmatic social object. But in recent years it has become less obvious that this is so. Margaret Gilbert, for instance, hesitates to attribute “sociality” to crowds: sociality, she argues, arises from norms and commitments, which many crowds lack. According to Gilbert, it is with joint commitment that a group is genuinely social (Gilbert 1989). Other philosophers and sociologists make alternative claims about the “mark of the social”, while still others deny that there is any criterion for distinguishing the social from the non-social (see Greenwood 1997).