This chapter traces the idea of (migrant) ‘integration’ from its roots in classical political philosophy and the birth of the modern nation-state, to its current relevance in the European political agenda and, relatedly, its centrality in the newly consolidated field of Migration Studies. As an early sociological concept, ‘integration’ began as a question of the cohesiveness of the social body as a whole (societal integration), but political rationalities of present see it primarily as linked to the role of ‘Others’ in society (migrant integration). This chapter first discusses why this shift occurred and how integration became a hegemonic discourse embraced across the political and scholarly realm on both sides of the Atlantic. Next, it examines the parallel and often joint development of, on the one hand, the field of integration/assimilation research, and on the other, a Europe-wide policy trend known as civic integrationism. The chapter shows how the production of the subject of integration—the misfit ‘immigrant’ figure—is historically marked by a consensus across scholarship and government that identifies the preservation of a homogenous national social order as a societal goal.