John Dewey's Human Nature and Conduct...What struck me... was the related idea that human thought is a reaction to frustrated habit— what people ofte… - William Hardy McNeill

The diffusion of alchemy westward, like the movement of astrology eastward, became significant only in the centuries after 200 A.D. The conservatism of learning was such that, even when commercial intercourse had made intellectual contacts possible, little serious interchange took place until severe social stress had disturbed the even tenor of the times in China, India, and Europe. Technology was a little, but only a little, less conservative.

Inferences and large dosages of imagination actually have allowed the construction of a far more adequate understanding of the cosmic and human past than earlier generations achieved. I believe that this is the central intellectual accomplishment of the twentieth century. Innumerable cosmologists, physicists, mathematicians, anthropologists, sociologists, historians, ecologists, ethologists, and other specialists have played their part; a few swashbuckling intellects led the way, and the outlines of an evolutionary worldview, uniting natural and human history, has begun to emerge. It may be convincing for generations to come—or again may not.

Decisive breakthroughs in military medical administration came just after the turn of the twentieth century. Until then, in even the best-managed armies, disease was always a far more lethal factor than enemy action, even during active campaigns.