In ancient Chinese cosmology, the universe was created not by divinities but self-generated from the interplay of nature's basic duality: the active, light, dry, warm, positive, masculine yang and the passive, dark, cold, moist, negative yin. All things, animate and inanimate, and all circumstances were a combination of these fundamentals. The ultimate principle of the universe was the tao, "the way," and it determined the proper proportions of yin and yang in everything. Anything that altered the natural relation of yin to yang was considered bad, and right living consisted of carefully following the tao. If one observed the tao by moderation, equanimity, and morality, as taught in the Tao-te Ching, by Lao-tzu (sixth century B.C.), one would be impervious to disease and resistant to the ravages of aging; disregard of the tao led to illness, which was not so much a punishment for sin as the inevitable result of acting contrary to natural laws. However, illness also could be caused by forces beyond one's control: "Wind is the cause of a hundred diseases," and atmospheric conditions could upset the harmonious inner balance of the yang and yin. One had to be alert to this possibility and combat its effects as well as modify internal imbalances of the vital forces. Longevity and health were the rewards.
Chinese medicine, in league with Taoism, was focused on the prevention of illness; for, as the legendary Huang Ti, father of Chinese medicine, observed, "the superior physician helps before the early budding of disease." Although Taoist hygiene called for temperance and simplicity in most things, sexual mores were governed by the yin-yang aspect of Chinese philosophy. Ejaculation in intercourse led to diminution of a man's yang, which, of course, upset the inner balance of his nature. On the other hand, one was strengthened by absorption of the yin released by the orgasm of one's female partner—unless she was over thirty, the point where female essence