The structure of pluralism: "We're all Italian around here, aren't we, Mrs. O'Brien?'

The subtitle of this paper is the punch-line of a story told by a perceptive observer of American ethnicity, Richard Juliani, who was being led through one of the all Italian blocks in South Philadelphia, Pennsylvania. It summarizes in a sentence the many contradictions found in the literature on ethnicity. Here is evidence of a melting pot, assimilation, cultural pluralism, and what Stephanie W. Greeley has labeled ethnogenesis, the emergence of new forms of ethnicity in the U.S. which have little relationship to national origins. The problem is that there is strong evidence supporting both the assimilation and cultural pluralism hypotheses. In order to make advances it is necessary to maintain the distinction between categories and groups. This paper, reporting the results of an investigation of ethnic groups in Philadelphia, Pennsylvania, is organized around two general issues. First, it focuses on the historical and structural problem of identifying the boundaries of groups and examining the relationship between the formation of ethnic groups and the city's economic and ecological structure. Second, is an analysis of the micro-level issues of the antecedents and consequences of group membership.