The first lesson that Durant reveals to us is modesty. Two scientific revolutions forced us to be modest, the Copernican revolution, and the Darwinian revolution. Copernicus told us that we are not the center of the universe, and Darwin told us that we are merely highly evolved animals, but animals nonetheless.
What we think of as the most meaningful and important, our human lives is really, the accidental by-product of the grand forces of nature. And these forces exist within us, and around us, for all life is the struggle for existence, and the survival of the fittest.
It is impossible to have a total perspective on history. The best we can aim towards is partial knowledge. It is dangerous to think that within 30 to 40 years of studying, man can judge and subvert the collective wisdom of the human race, to question its tradition and motivation.
People like to think they are a little special, but of course, this is a delusion. Yet we need it to progress. Without this bit of vanity, we might find it harder to push forward. Delusion is a powerful motivator.