Human mobility poses a major challenge for social and normative theories developed during the age of nation-building. Many of these theories suffer from the cognitive biases of sedentarism, presupposing that populations are largely immobile, and of methodological nationalism, assuming a state-centred view of culture, territory, and human relationships. This raises conceptual issues for social theories that attempt to understand migration (a transnational phenomenon) through categories that presuppose largely homogenous, sedentary populations and rigid state borders. These cognitive biases create normative challenges by treating mobility as exceptional and pathological, in need of regulation and restriction. This perspective conflicts with widely recognised rights to mobility and with the fact that humans are a mobile species. People move in response to violence, persecution, and the inability to satisfy basic needs, as well as for reasons of family unification and economic interests. The use of force to prevent people from exercising their rights and from accessing important goods requires moral justification. This in turn suggests the need to situate mobility in a broader theory of global justice, as well as post-national social theory.