When we step back and think about the relationship between science and metaphysics, paradigmatically we think about physics, and we think about the metaphysics of space, time, and material existence quite generally. But metaphysical questions also arise in connection with biological, psychological and social entities, in realms investigated by the various special sciences. What is the relationship between scientific and metaphysical investigation in these domains?

In this paper I discuss this question in the context of social groups, looking in particular at identity conditions for social groups, and at the relationship between groups and their members. What can general metaphysical discussion of parthood, composition and persistence tell us about such issues? And how does such metaphysical discussion interact with (a) social scientific theories and (b) our intuitions about social groups?