The freedom to choose where to live and work is a fundamental right in liberal societies. The moral equality of persons is the basic principle of democratic politics. But liberal democracy has no coherent theory of boundaries, or how members should be selected for political communities. The global economy requires mobility across borders, but liberal democracy cannot reconcile the demands of footloose and rivalrous economic agents with the human needs of sedentary and vulnerable populations. These are urgent issues for the new century, as the upsurge of nationalist, authoritarian and racist movements threatens the liberal democratic order. Mass migrations in search of political freedom and economic opportunity expose incoherence in states’ policies, and in theories of equality and justice. Whilst globalization allows new opportunities for mobility and membership in a chosen community, claims for income support or humanitarian protection are viewed as signs of moral...