Is the social integration of contemporary Western societies at risk? We will not provide an answer to this question, which is high on the political agenda. Instead, in our introduction to this special issue, we first offer conceptual clarifications. What is a theoretically sound and empirically useful understanding of the social integration of modern societies? Second, we ask three basic questions for which adequate answers have not yet been found: (1) How is social integration generated? That is, what are its central mechanisms? (2) Is social integration a functionally necessary precondition of societies, as concerns about its erosion suggest? Or is it a goal in itself, that is, a normatively desirable state? (3) What about the dark side of social integration, i.e., its unintended or tacitly accepted side effects for society, its individual members, or particular social groups?
