A model of particularism is proposed that distinguishes bases and levels of identification, association, unions, and organization. It is constructed from the literature on urbanization in Subsaharan Africa and the author's research in Nigeria. The context of ethnicity is described as a set of concentric circles designating the more narrowly or more largely defined ethnic groups ego identifies with, recruits his/her friends from, joins in unions, and supports in formal organizations. Socioeconomic position and religion are seen as alternative bases, each again offering different levels at which to define ‘we’ as against ‘they.’ The model thus focuses attention on both: alternative contents of particularistic attachment and action, and different levels of ethnic, socioeconomic, or religious inclusiveness at which such attachment and action crystallize.