Europe was essentially defined by Islam. And Islam is redefining it now. For centuries in early and middle antiquity, Europe meant the world surrounding the Mediterranean, or Mare Nostrum (“Our Sea”), as the Romans famously called it. It included North Africa. Indeed, early in the fifth century A.D., when Saint Augustine lived in what is today Algeria, North Africa was as much a center of Christianity as Italy or Greece. But the swift advance of Islam across North Africa in the seventh and eighth centuries virtually extinguished Christianity there, thus severing the Mediterranean region into two civilizational halves, with the “Middle Sea” a hard border between them rather than a unifying force. Since then, as the Spanish philosopher José Ortega y Gasset observed, “all European history has been a great emigration toward the North.” After the breakup of the Roman empire, that northward migration saw the Germanic peoples (the Goths, Vandals, Franks, and Lombards) forge the rudiments of Western civilization, with the classical legacy of Greece and Rome to be rediscovered only much later. It would take many more centuries for the modern European state system to develop. Slowly, though, feudalism, whose consensual give-and-take worked in the direction of individualism and away from absolutism, gave way to early modern empires and, over time, to nationalism and democracy. Along the way, new freedoms allowed the Enlightenment to take hold. In sum, “the West” emerged in northern Europe (albeit in a very slow and tortuous manner) mainly after Islam had divided the Mediterranean world.

Islam did much more than geographically define Europe, however. Denys Hay, a British historian, explained in a brilliant though obscure book published in 1957, Europe: The Emergence of an Idea, that European unity began with the concept (exemplified by the Song of Roland) of a Christendom in “inevitable opposition” to Islam—a concept that culminated in the Crusades. The scholar Edward Said took this point further, writing in his book Orientalism in 1978 that Islam had defined Europe culturally, by showing Europe what it was against. Europe’s very identity, in other words, was built in significant measure on a sense of superiority to the Muslim Arab world on its periphery. Imperialism proved the ultimate expression of this evolution: Early modern Europe, starting with Napoleon, conquered the Middle East, then dispatched scholars and diplomats to study Islamic civilization, classifying it as something beautiful, fascinating, and—most crucial—inferior. A classical geography is reasserting itself, as terrorism and migration reunite North Africa and the Levant with Europe. In the postcolonial era, Europe’s sense of cultural preeminence was buttressed by the new police states of North Africa and the Levant. With these dictatorships holding their peoples prisoner inside secure borders—borders artificially drawn by European colonial agents—Europeans could lecture Arabs about human rights without worrying about the possibility of messy democratic experiments that could lead to significant migration. Precisely because the Arabs lacked human rights, the Europeans felt at once superior to and secure from them. Islam is now helping to undo what it once helped to create. A classical geography is organically reasserting itself, as the forces of terrorism and human migration reunite the Mediterranean Basin, including North Africa and the Levant, with Europe. The Continent has absorbed other groups before, of course. In fact, Europe has been dramatically affected by demographic eruptions from the east: In the medieval centuries, vast numbers of Slavs and Magyars migrated into central and eastern Europe from deeper inside Eurasia. But those peoples adopted Christianity and later formed polities, from Poland in the north to Bulgaria in the south, that were able to fit, however bloodily, inside the evolving European state system. As for the Algerian guest workers who emigrated to France and the Turkish and Kurdish guest workers who emigrated to Germany during the Cold War, they represented a more containable forerunner to the current migration.