People in ancient China believed that wood, fire, earth, metal and water were indispensable to daily life and were key to the variations in the natural world. Today we can still find examples of these elements and their natural relationships: people still drink water and use fire to cook food; metal and wood are still made into various tools; and earth still ensures the growth of all things! These elements are interrelated and influence each other in specific dynamics. Such a cognition and understanding eventually formed the theory of the five elements.
Five Elements “(wu xing)” is actually not the best translation of the theory. In Chinese, "wu" refers to five, for the five elements: wood, fire, earth, metal and water; and "xing" means movement and transformation. So "wu xing" (five elements) actually refers to the movement and transformation of these elements including their interrelationships, hence why its also referred to as the “Five Phases.”
The theory of five elements holds that all things in the natural world are derived from wood, fire, earth, metal, and water. Life bears the basic properties of all five elements and maintains a harmonious balance through the activities of constant inter-promotion and inter-restraint.
Categorization According To Five Elements Theory
The early understandings of the characteristics and properties for wood, fire, earth, metal and water derived from observing the natural world. Such examples are "water moistens and flows downward," "fire flames upward," "wood can be flexed and extended," "metal can be changed in form" and "earth can grow crops," etc.
In order to explain the properties of more things, people abstracted the properties of the five elements for extensive application, broadened their implications. For example, the properties of flexing and extending, growth and development as well as free activity all pertain to the wood element; warmth, heat, ascending and brightness all pertain to the category of fire; reception, cultivation and transformation all pertain to the category of earth; change, depuration and astringency all pertain to the category of metal; and moistening, downward movement, cold and coolness, as well as closure and storage all, pertain to the category of water.
Wood: Flexing and extending | Growing, ascending, developing freely
Fire: Flaming upward | Warming, brightening, moving upwards
Earth: Cultivating and reaping | Growing, supporting, transporting, receiving
Metal: Changing | Purifying, astringent, descending
Water: Moistening and flowing downward | Moistening, moving downwards, cooling, storing
From these classifications, TCM uses this method of categorization, inference and deduction to label things in the natural world as well as the viscera, organs and tissues of the human body respectively into the categories of wood, fire, earth, metal and water according to their properties. This in turn, has formulated a structural system of the five elements with close interrelationship between the internal and external environments of the body. This structural system of the five elements mainly includes the five flavors, the five colors, the five transformations, the five kinds of Qi, the five directions and the five seasons as well as the five Zang-organs, the five Fu-organs, the five sensory organs, five constituents (tendon, vessel muscle, skin and bone), the five emotions, the five kinds of liquids and the five states of pulse in the human body as illustrated in the following table.
(Top to bottom: Wood - Fire - Earth - Metal - Water)