Even a brief glance at modern history suggests that there is an important connection between popular sovereignty and the rise and spread of nationalism. At first glance then, it seems clear that “without a historically informed understanding of the theory of popular sovereignty, no clarification of the language of nation-states and nationalism is possible.” But correlations do not establish connections, let alone causation. This article attempts to identify some causal mechanism or some theory that would explain why belief in popular sovereignty should lead to the political assertion of national loyalties. The articles argues that (1) the spread of popular sovereignty doctrine has altered our understanding of political community in ways that are anything but self-evident, and (2) it is by means of this altered understanding of political community that it has made its greatest contribution to the rise and spread of nationalism.