To see just how much geography and old empires shape today’s Europe, look at how former Communist Eastern Europe has turned out: the countries in the north, heirs to Prussian and Hapsburg traditions  Poland, the Czech Republic and Hungary  have performed much better economically than the heirs to Byzantium and Ottoman Turkey: Romania, Bulgaria, Albania and Greece. And the parts of the former Yugoslavia that were under Hapsburg influence, Slovenia and Croatia, have surged ahead of their more Turkish neighbors, Serbia, Kosovo and Macedonia. The breakup of Yugoslavia in 1991, at least initially, mirrored the divisions between Rome and Byzantium.

The Greek debt crisis is the biggest challenge since those Yugoslav secessions to Europe’s attempt at overcoming its geographical and historical divisions. Whereas in the early decades of the cold war the European enterprise had to heal only the long-time rift between France and Germany, now it is a matter of Carolingian and Prussian Europe  Brussels and Berlin  incorporating the far-flung Mediterranean and Balkan peripheries.

And it is precisely because Europe, for the first time in history, faces no outside threat to its security that it may fall prey to the narcissism of its internal contradictions. That the European Union’s northern powers aren’t willing to bail Greece out entirely by themselves, but are relying on the International Monetary Fund to kick in up to $20 billion, shows that there are limits to how far they will go toward the dream of a unified supercontinent.

Still, just as geography has divided Europe, it also unites it. For example, a lowland corridor from the Atlantic to the Black Sea has allowed travelers for centuries to cross the length of Europe with speed and comfort, contributing to Europe’s cohesion and sense of itself. The Danube, as the Italian scholar Claudio Magris rhapsodizes, “draws German culture, with its dream of an Odyssey of the spirit, towards the east, mingling it with other cultures in countless hybrid metamorphoses.” Central Europe, cleft from the West during the cold war, is the continent’s universal joint: a fact that puts the responsibility for surmounting the politics of historical division squarely on the shoulders of a united Germany.

Germans should realize that Greece, with only 11 million people, nevertheless remains the ultimate register of Europe’s health. It is the only part of the Balkans accessible on several seaboards to the Mediterranean, is roughly equidistant from Brussels and Moscow, and is as close to Russia culturally as to Europe by virtue of its Eastern Orthodox Christianity. In a century that will likely see a resurgent Russia put pressure on Europe, especially on the former Soviet satellite states in the east, the state of politics in Athens will say much about the success or failure of the European project.

The good news is that northern Europeans know this, and will not let Greece fail. Indeed, to let Greece drift politically eastward would forfeit any hope of a big and inclusive Europe  geographically, politically and culturally  in favor of a small and petty one, Charlemagne’s empire pretending to be Rome.