The five elements refer to wood, fire, earth, metal, and water and their motions. The five element theory resulted from the observations and studies of the natural world by the ancient Chinese people in the course of their lives and productive labor. Since ancient time, wood, fire, earth, metal and water have been considered as basic substances to constitute the universe and they are also indispensable for life. Zuo’s Interpretation of the Spring and Autumn Annals (Zuo Zhuan) says: “The five kinds of materials in nature are all used by people. None of them cannot be dispensed with”. Another classical work Shang shu states: “water and fire are used for cooking, metal and wood are used for cultivating and earth gives birth to all things, which are used by people.” These five kinds of substances are of the relationships of generation and restriction, are in constant motion and change. In TCM the five-element theory, as a theoretical tool, is used to explain and expound different kinds of medical problems by analogizing and deducing their properties and interrelations. It also used to guide clinical diagnosis and treatment. The theory, like the theory of yin-yang, has become an important component of the theoretical system of TCM.

Classification of Things in Light of the Five-Element Theory.

In ancient China, the five-element theory was unceasingly developed and gradually became perfected. In time it came to recognize that everything in nature might be respectively attributed to one of the five elements. For instance, wood has the nature of growing freely and unfolding. So, anything that is similar to the characteristics is attributed to the category of wood. Fire has the nature of flaring up. Thereby the things similar to the nature of fire are classified into the attribute of fire. Earth has the nature of giving birth to all things. Thus, those that possess the nature of earth are attributed to earth. Metal has the nature of purifying and descending. Hence, those with the nature of metal can be attributed to metal category. Water has the nature of moistening and flowing downwards. For this reason, the things that have moistening, downward movement and coldness correspond to water. The following table shows the classification of partial things according to the five-element theory.

Among the five-elements, there exist the relationships of generation, restriction, subjugation and counterrestriction, and mutual affection between mother-organ and child-organ. Generation implies that one kind of thing can promote, aid or bring forth another, i.e., wood generates fire, fire generates earth, earth generates metal, metal generates water, and water, in turn, generates wood. Each of the five elements contains the dual nature –“being generated” and “generating”. This relationship of the five elements is called the “mother-child” relationship. The element that generates is called the “mother”, while the element that is generated is called the “child”. Take wood for example, because wood produces fire, it is the mother of fire; but it is produced by water, so it’s water’s child.

the Classification of Things According to the Five Elements  

Restriction means bringing under control or restraint. The order of restriction goes as follows: wood restricts earth, earth does water, water does fire, fire does metal, and metal, in turn, does wood. Any one of the five elements has two aspects -being restricted and restricting. For example, the element restricting wood is metal, and the element that is restricted by wood is earth.