The Doctrine of Yin and Yang, and the Principles of Chinese Medicine

The ancient Chinese, like their modern counterparts, sought a way to understand and explain the world around them, principle and purpose in the changing pattern of events around them, and order in the chaos of existence.
The most powerful principle used to explain the cause and effect of events was that of the interplay of Yin and Yang, two opposite but complementary forces whose relationship and mutual ascendancies are continually changing.
Yin is negative, passive, weak, receptive; Yang is positive, active, strong, creative. Neither can exist without the other, and each, even at its most abundant, contains the seed of the other.
As Yin and Yang compete and cooperate in the manifestation of all things, so events occur in cycles, with various attributes and tendencies gaining ascendancy, and then diminishing. It was the legendary Huang-Ti, the Yellow Emperor, who first documented the cyclical nature of existence and its manifestation in the Five Elements: Metal, Water, Wood, Fire, and Earth. He noticed at various times the ascendancy of different types of life, and their associated colours; at one time, earthworms and burrowing insects were abundant, the force of Earth being strong; later, grass and trees were abundant, the force of Wood in full ascendancy. Later. metal blades appeared in the waters of the palace, and so on.