But even the steady state, our best-hope future, may not be achievable without space. Without power and materials from space we are doomed to shuffle… - Stephen Baxter

In the last centuries of the empire, educational standards and literacy had fallen. In the dulled heads of the masses, distracted by cheap food and the barbaric spectacles of the coliseums, the values on which Rome had been founded and the ancient rationalism of the Greeks had been replaced by mysticism and superstition. It was—Honorius had explained to his pupil—as if a whole culture was losing its mind. People were forgetting how to think, and soon they would forget they had forgotten. And, to Honorius’s thinking, Christianity only exacerbated that problem.
“You know, Augustine warned us that belief in the old myths was fading—even a century and a half ago, as the dogma of the Christians took root. And with the loss of the myths, so vanishes the learning of a thousand years, which are codified in those myths, and the monolithic dogmas of the Church will snuff out rational inquiry for ten more centuries. The light is fading, Athalric.”

But what would humans do, she mused, if they stumbled on a situation like this?
Well they wouldn’t be satisfied with the generosity of Candyland. They’d breed until the caves were overflowing. The hunters would start ranging farther until all the animals in the area were eaten or driven away. Then agriculture would start, with everybody forced to bend their bodies to back-breaking toil, day after day. As the population exploded the forests would be cut back, the animals decimated.
Then would come the famines and the wars.

I was struck by how ignorant we humans are, or make ourselves, of the passage of time itself. How brief our lives are!—and how meaningless the events which assail our little selves, when seen against the perspective of the great plastic sweep of History. We are less than mayflies, helpless in the face of the unbending forces of geology and evolution—forces which mold inexorably, and yet so slowly that, day to day, we are not even aware of their existence!