### Wuxing and Compatibility Coefficient: Part I

Wuxing (五行) is a very fundamental concept in Chinese fate calculation. Some scholars believe that wuxing originates from the planetary motion of the five planets visible to the naked eyes, namely Mercury, Venus, Mars, Jupiter, and Saturn.

In the Chinese literature, the term wuxing first appeared in a war declaration when Qi (启), the second King of the Xia Dynasty, was preparing to launch a war on the tribe of You Hu (有扈).
Shang Shu: Gan Shi (The Declaration of Gan)《尚书·甘誓》: The tribe of You Hu insulted the wuxing and muddled the correct calendrical order. It is the heaven will that they must be destroyed. I am now to dutifully carry out my heavenly duty to punish them. (有扈氏威侮五行，怠弃三正，天用剿绝其命，今予惟恭行天之罚。)
In this text, the term wuxing was not defined. It is possible that the author of the declaration meant to use the term wuxing in its planetary sense or `heaven' in general. The first discussion of Wuxing can be found in Hong Fan (洪范).

When Ji Fa (姬发) destroyed the Shang Dynasty, he had a conversion with an old Shang official named Qi Zi (萁子) on how to rule a nation. Shang Shu: Hong Fan (The Great Laws) 《尚书·洪范》is the record is that discussion. The book was probably compiled during the Spring-Autumn period.
Shang Shu: Hong Fan (The Great Laws)《尚书·洪范》: Wuxing: The first is water, the second is fire, the third is wood, the fourth is metal, and the fifth is earth. Water is characterized by downward flowing moist, fire by upward flowing flame, wood grows vertically, metal is moldable, the earth permits the growth of crops. (五行：一曰水，二曰火，三曰木，四曰金，五曰土。水曰润下，火曰炎上，木曰曲直，金曰从革，土爰稼穑。)
It is in the Book of Hong Fan (洪范) that the elemental characteristics of wuxing is first explained. It is quite clear that wuxing is treated as matter or substance here.