The dramatic inauguration of democratic regimes in Eastern Europe after 1989 and their subsequent petitions to join the European Union (EU) are usually treated as separate events. But in fact they advanced a common political result: European unity. That the European Union promotes unity is plain. But democracy is an integrating force, too. The signers of the Helsinki Accords in 1975 asserted human rights as fundamental European values; at the end of the Cold War, heads of state spoke of a “common European home” of liberal democracies extending from the Atlantic to the Urals. Together European democratization and integration have curtailed the power, autonomy, and even sovereignty of the polity that has fragmented Europe for centuries: the nation state. Transnational unity is a historically notable end, for it has long been absent from Europe, achieved first in the Roman Empire, realized last in medieval Christendom, theorized in modern times in the philosophical visions of Rousseau, Kant, and Wilson, and attempted – without ultimate success – in the imperial ambitions of Napoleon and Hitler.

Europe's increasing transnational unity in its democratic and integrative dimensions greatly interests Europe's predominant religions: Roman Catholicism, Orthodoxy, and Islam. Given their own aspirations to transnational unity and universality, this is entirely fitting. They have a stake in this momentous trend for an additional reason: Europe's elites increasingly cast democratization and integration as secularizing projects, as José Casanova argues in this volume.