Charles Van Doren writes in A History of Knowledge that the period from 450 to 550 AD were the darkest in the history of western civilization. The Byzantine Empire was unable to re-establish the Pax Romana that western Europe had known and the literacy, commerce and law became scarce.

Instead people were illiterate, their world shrunken to a small area around where they were born. Roads were too dangerous to travel as the law was one of arbitrary violence and force. Commerce shrunk to subsistence living and barter become the main mechanism of trade as the coins of the old Roman Empire were used up. The arts, philosophy and other leisure activities that the stability of the Roman political system had enabled was gone too. The population waned as a result of this instability. Van Doren writes:

It is hard to imagine them [these years]. Historically, they are almost a blank, we only know that at the end of this period of rapine and death the region now called Europe was utterly changed.

Van Doren's argument as to why there was a fall into the Dark Ages when Europe has survived political collapse and invasions (barbarian and nation-state) since without the catastrophic collapse of society, commerce and civilization; is that it was the effect of Christianity and its cultural dominance that led to the Dark Ages.

Van Doren writes that Rome was more like we are today; deeply devoted to the material world, and with out lust for adventure, travel, power, wealth and leisure - including exercise and health. With the collapse of the Empire and its replacement by the arbitrary nature of Dark Ages feudalism, Van Doren argues the people embraced Augustine's City of God rather than Rome's City of Man. Van Doren writes:

The new kind of Christians, after the fall, had little interest in their bodies as such. They cared about the health of their souls. They had no interest in consumption. They could lose their reputation rather than gain it for possessing wealth in a society where poverty was next to godliness.

Roman wealth was replaced by Christian poverty. Van Doren notes that rationality is perfectly logical to the people living under it at the time. To a Dark Ages christian they did not see the Dark Ages as a fall, or as dark; they saw it perfectly rational and normal to devote their lives to their soul's ascent to heaven through living for God.