Rome

After the Athenian Alliance in Greece lost its power, Rome (in Italy) became the dominant and imperial civilization in Europe and the Mediterranean. Rome and, therefore, Europe became Christian when Constantine, the Roman emperor, converted to Christianity.

Rome was a successful administrative civilization and brought law, government, roads, irrigation, etc. to the primitive countries of Europe; however, they, like the great civilizations before them, eventually collapsed. Why? War, of course: this time, war brought on by the barbarian Germanic tribes of Germany and Scandinavia, which swept through Europe wiping out all that the Romans had accomplished. And so humankind begins another Dark Age, much like our Mycenaean Greeks' after the collapse of their civilization. This dark age in Europe lasted until what we call the Middle Ages (or the medieval age), from roughly 500-1500 A.D.

Christianity

From an historical perspective, the new religion appealed to

Psychological factor: Christianity -- with its messages of forgive thy neighbor; turn the other cheek -- offered a release from hatred and an answer to the problem of revenge.

During the Dark Ages, the Church became an organizing bureaucracy and provided stability, internationalization and a meritocracy. Also, learning -- including literature -- survived in Christian monasteries where monks and labored in scriptoriums copying ancient texts that would otherwise be lost to us. They also "illuminated" the pages of these texts.