Achieving consensus on a definition of “democracy” has proven elusive. Institutions that have been taken to be essential to democracy have changed radically since the word “democrat” began to be widely used toward the end of the eighteenth century. Democratic ideas and democratic practice engender conflict that transforms institutions rather than just reproduces them. Its transformative character rests on a half-dozen key attributes of democracy: it is an actor’s concept, as well as an analyst’s; it can arouse strong feelings; it combines not always compatible ideas; it empowers dissent; it involves a dynamic mixture of inclusion and exclusion; and the democratic histories of national states have been intertwined with global domination. Two processes combine to generate much social dynamism. First, democracy’s stirring inclusionary claims have been contradicted by a complex structure of exclusions, including distinctions in rights of full participation among citizens, distinctions in rights between citizens and non-citizens, and distinctions in resources among legally equal citizens. And second, democratic practice has been fertile soil for the development of social movements. Taken together, democracy is an invitation for movements to try to shift the boundaries of inclusion and exclusion, and in so doing to expand or constrict democracy itself.