Social groups and classical extensional mereology

The mereological account of social groups based on Classical Extensional Mereology (CEM) is notoriously associated with the reductionist stance that social groups are regular fusions identified by mereological conditions alone. This approach has many limitations and has suffered knock-down objections due to its transitive and coextensional features. The reaction to this impasse has been twofold. Philosophers have either moved away from CEM-based accounts altogether or attempted to resist these objections by appealing to extra-ontological explanations while retaining the reductive qualification of social groups. In this paper, I develop a non-reductive yet CEM-based framework that employs the notion of φ-parthood to restrict the interpretation of parthood simpliciter through extra-mereological, socially relevant conditions. Social groups turn out to be specified fusions and, depending on how the extra-mereological conditions are interpreted, the resulting account can be extensional or intensional. I show that both accounts successfully handle transitivity and coextensionality objections, and argue that long-standing objections from modal and temporal inflexibility are misguided for any CEM-based account.