I do not insist that I am right: I merely think so. - 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.

My principles require me merely to invite you to agree, while expecting the contrary. Missionaries do not make converts with such a message: millions are not mobilized by such tepid phrases. That is why the merely intellectual compulsion to regard human diversity and flux is unlikely to prevail against simpler systems of misunderstanding truly capable of altering the world in which we live.

The principle obstacle to human dominion over the rain forests is still the rich variety of parasites lying in wait for intruders.