Abstract: The traditional aim of Western social democracy has been to create a society that is a “common possession” of its members (in T. H. Marshall’s words). Social democratic politics has therefore been both society-making and membership-making, orienting people to a shared society as an object of attachment and loyalty, and nurturing membership-based conceptions of democracy and the welfare state. This aspiration to create a society that is the common possession of its members has underpinned many social justice movements. However, some commentators argue that this model of politics only works for a long-lost world of sedentary populations, and is ill-equipped for an age of migration and liquid mobility. Immigrants are rendered vulnerable when politics is built around the idea that individuals are “members” of “societies”, or on the assumption that politics should aim to orient people to a shared society as an object of loyalty and a basis for solidarity. In this paper, I explore how the ideal of society as a common possession of its members can address different forms of migration, whether it can make room for the experiences and aspirations of migrants, and what immigrants themselves think about the legitimacy of membership-making.