Drawing on Foucault's approach to knowledge and power, this paper aims to strengthen theoretical perspectives on migration and to revise social theories by reflecting on the constitutive role of migration in the formation of society. Differing from studies that use a methodological approach based on Foucault, I draw on his work to develop a constructivist theory of society by examining and problematizing two dominant lenses through which migration is commonly problematized: the epistemological-political grids of the “people,” associated with sovereign power and nationalism, and the “population,” associated with biopower and capitalism. Both grids are crucial for understanding how migration is constructed as a specific object of knowledge and incorporated into mechanisms of power. Taken together, they allow us to reconnect the often separated debates on sovereign power and biopower—or nationalism and capitalism—and to reflect on the central tensions of contemporary migration societies. By highlighting the relevance of border and migration processes that Foucault barely addressed, I open up an alternative perspective on people and populations through an analysis of the marginal figures of “vagabondage” and “bad circulation” that are currently most associated with migration.