What caused the fall of the Roman Empire? The first reply that occurs to us is this: That the Romans were corrupt and enfeebled by corruption; the Barbarians, while rougher, were also stronger and less corrupt. When the latter had once crossed the Rhine and the Danube, their ultimate victory was assured; the Empire was bound to fall, new social conditions were bound to arise. But what had corrupted and weakened a people that had been for so many centuries a model of discipline, virtue, and strength - a people that had conquered the world? Its corruption was a consequence, not a cause, and was the first symptom of the decline that had already begun. The Empire that Livy had seen bending beneath the burden of its own greatness could not last forever.
- From The Barbarian Invasions of Italy by Pasquale Villari