The theory of the five elements (Wu Xing)

In TCM theory, the five elements (metal, wood, water, fire and earth) and the Yin and Yang are what constitute the physical universe. The theory of the “Five Elements” is known as "Wu Xing" in Chinese. To maintain balance among them, these elements support one another (the generating cycle), and oppose one another (the controlling cycle).

The generating cycle of the five elements

The generating cycle of the five elements describes the consequential series of the elements supporting the creation of another, which in turn supports the creation of another, and so forth, in a cyclical fashion:

• Water generates Wood, for without moisture there cannot be growth.
• Wood is the fuel to create Fire, and it is the action of heat on organic matter that produces Earth (think of a compost heap).
• Metal and minerals are generated from the Earth, and these filter and purify the Water that returns to feed the trees. So the cycle continues.

The controlling cycle of the five elements

Equally, and conversely, each element cyclically opposes or controls another element. This cyclical process is referred to as the ‘controlling cycle’. The controlling cycle exists to balance the generating cycle and connect the elements, thus forming a complete and balanced system.

For example, Water will keep Fire in check and Fire can make Metal usable. The hardness of Metal is required to tame Wood. Without the controlling structure of roots, the Earth would collapse and be in disarray. Water is without shape and will always sink to the lowest level: it is Earth that defines its outline.

Each element is characterised by certain properties, and is in turn associated with a season (this is with the exception of Earth, which is present in each of the four seasons). In terms of bodily functions, this is expressed through the organ relationships between each of the Five Elements. Each Element has an associated Yin and Yang organ.

The characteristics of the five elements:

Wood is associated with Spring and the Easterly direction. This is because the characteristic of wood is that of germination: spring is the time of germination, as is east is where the Sun rises, just as plants rise as they germinate. Its corresponding colour is green. In terms of the human body, in TCM theory, wood is correspondent with the following components of the human body:

Solid Organ (Zang)	Liver
Hollow Organ (Fu)	Gall bladder
Tissues	Tendons/nails
Body Fluid	Tears
Five Senses	Eye (Sight)
Sound	Shout
Emotions	Anger

These associations are based on the elemental characteristic properties of wood, and their relationship in the context of the components of the human body.

Fire is associated with summer, and the southerly direction. It is characterised by the phase of growth, and the correspondent colour is red. The corresponding human body functions:

Solid Organ (Zang)	Heart
Hollow Organ (Fu)	Small Intestine
Tissues	Blood vessels/ Complexion
Body Fluid	Sweat
Five Senses	Tongue (Speech)
Sound	Laugh
Emotions	Joy

Earth is present throughout all four seasons, but is particularly also associated with the late summer. The corresponding direction is centre. It is characterised by the phase of transformation, and the corresponding colour is yellow. The corresponding TCM body functions:

Solid Organ (Zang)	Spleen
Hollow Organ (Fu)	Stomach
Tissues	Muscles/Lips
Body Fluid	Saliva
Five Senses	Mouth (Taste)
Sound	Sing
Emotions	Thinking

Metal’s correspondent season is autumn, and direction is West. It is characterised by the phase of harvest. Its associated colour is white. The body functions:

Solid Organ (Zang)	Lung
Hollow Organ (Fu)	Large Intestine
Tissues	Skin/Body Hair
Body Fluid	Mucus
Five Senses	Nose (Smell)
Sound	Cry
Emotions	Melancholy

Water is the phase of the elemental cycle associated with winter, and the direction of the north. Its characteristic cyclical phase is that of storage: the storage of energy, as is the form of water. The corresponding colour to this element is black. The TCM human body components, thus, are as follows:

Solid Organ (Zang)	Kidney
Hollow Organ (Fu)	Urinary Bladder
Tissues	Bone/Head Hair
Body Fluid	Urine
Five Senses	Ears (Hearing)
Sound	Mourn
Emotions	Fear

The interrelationships between the elements in their characteristic properties is applicable to the contexts that they represent, i.e. the property of certain elements within the generating and controlling cycles in relation to each other is relevant to their associated characteristic weather patterns, body functions and can thus be identified and used in TCM diagnosis accordingly. This is the reason behind the association with the elements with particular organs of the human body in TCM theory: the properties of the elements are observed to be applicable in the context of the human body and its components, and as such so are the relationships between these components.