In ancient Greece, there was a theory of four elements. The four elements include fire, water, earth and air. A Greek philosopher Anaximander developed this theory, and he thought that a kind of original substance formed the four elements. At the same time, in ancient China, there was a theory of five elements. The five elements include wood, fire, earth, metal and water. They were formed by a kind of original substance which was called Qi (氣). In the Warring-States Period, Zou Yan, a thinker of the Qi (齊) State, connected the theory of five elements with the theory of Yin and Yang. Moreover, Zou Yan used the theory of five elements to explain and prophesy the changing of dynasties. Qin First-Emperor accepted this theory, because he needed it to justify his imperial regime. Except political use and philosophical use, the theory of five elements was also used widely by traditional medicine in ancient China.
Five elements are correlative. The relations of the five elements include promotion and restraint. Wood promotes fire, fire promotes earth, earth promotes metal, and metal promotes water. Why? Fire is from the burning of wood, and the ash formed earth. Under the ground, there are mineral resources of metal. Metal can be melted and become liquid as water.
As for the relations of restraint, wood restrains earth, fire restrains metal, earth restrains water, metal restrains wood, and water restrains fire. Why? A sprout breaks through the ground and becomes a big tree. A hoe or a spade has a wooden handle. Fire can melt metal. Earth can be used for building embankment against floods. An axe or a saw has a metal blade. Water can extinguish fire.
Five elements are abstracted to five attributes of many things such as seasons, climate, directions, colors, internal organs and taste so on. Spring, wind, east, green, liver and sour taste belong to wood. Summer, hotness, south, red, heart and bitter taste belong to fire. Autumn, dryness, west, white, lung and piquancy belong to metal. Winter, coldness, north, black, kidney and salt taste belong to water. Center, wetness, yellow, spleen and sweet belong to earth. The sixth month of the Chinese lunar calendar belongs to earth. Before the Han Dynasty, heart belonged to earth. However, in the Han Dynasty, heart started to belong to fire because of political need. Since the Han Dynasty, the theory of five elements had been steady.
Even today, the theory of five elements is still used for diagnosis, therapy and pharmacy in traditional Chinese medicine. For example, the face of a patient who has a nephropathy is a little black. Recent years, an herb Guanmutong (Caulis Aristolochiae Manshuriensis) has been forbidden, because the excessive dose of this herb is nephrotoxic and even induces acute renal failure. Patients whose kidneys are damaged by Guanmutong look a bit dark.
In ancient China, the theories of Yin-Yang and five elements were a panacea. If a person couldn’t explain a thing or a phenomenon, he would easily attribute it to the movement of Yin-Yang or five elements. This kind of attitude seriously hampered the development of ancient Chinese science.