The Opposition and Interdependence of Yin and Yang

The opposition of yin and yang generalizes the contradiction and struggle of the two opposites within an object or phenomenon. Ancient scholars used water and fire to symbolize the basic properties of yin and yang. That is to say, the basic properties of yin simulate those water, including coldness, downward direction, dimness, etc., while the basic properties of yang are like those of fire, including hotness, upward direction, brightness, etc. From this, it can bi inferred that anything that has the characteristics of quiescence, coldness, lower position (or downward direction), interior position (or inward direction), dimness, asthenia, inhibition, slowness, or which is substantial, etc., pertains to ying whereas anything that is moving, hot, in an upper position (or moving in an upward direction), exterior position (or outward), bright, sthenic, excited, rapid, non-substantial etc., belongs to yang.

Since the yin-yang nature of a thing exists only bay comparison, and moreover that a thing can be divided infinitely, its yin-yang nature is by no means absolute, but its relative. In some circumstances the two opposites of a thing may change, and so the yin-yang nature of the thing also changes. There exist the conditions of a yin aspect developing within yin, yang within yang, yang complicated with yin, and yin complicated with yang. This concept conforms with objective reality.

The tissues and organs of the human body may pertain either to yin or yang according to their relative locations and functions. Viewing the body as a whole, the trunk surface and the four extremities, being on the exterior, pertain to yang, while the zang-fu organs are inside the body and are yin. Viewing the body surface and the four extremities alone, the back pertains to yang, while the chest and abdomen pertain to yin; the portion above the waist pertains to yang and that below pertains to yin; the lateral aspect of the four extremities pertains to yang and the medial aspect to yin; the channels running along the lateral aspect of an extremity pertain to yang, while those along the medial aspect pertain to yin. When speaking of the zang-fu organs alone, the fu organs with their main function of transmitting and digesting food pertain to yang; while the zang organs with their main function of storing vital essence and vital energy pertain to yin. Each of the zang-fu organs itself can again be divided into yin and yang, e.g., the yin and the yang of the kidney, the yin and the yang of the stomach, etc. In short, however complex the tissues and structures of the human body and their functional activities, the can be generalized and explained by the relation of yin and yang.

The interdependent relation of yin and yang means that each of the two aspects is the condition for the other’s existence and neither of them can exist in isolation. For instance, without daytime there would be no night; without excitation there would be no inhibition. Hence, it can be seen that yin and yang are at once in opposition and in interdependence; they rely on each other for existence, coexisting in a single entity. The movement and change of a thing are due not only to the opposition and conflict between yin and yang but also to their relationship of interdependence and mutual support.

In physiological activities, the transformation of substance into function or vice versa verifies the theory of the interdepending relation of yin and yang. Substance pertains to yin and function to yang, the former being the basis of the latter, while the latter is the reflection of the existence of the former and also the motive force for the production of the former. Only when there are ample nutrient substances can the functional activities of the zang-fu organs are sound are they able constantly to stimulate the production of nutrient substances. The coordination and equilibrium between substance and function are the vital guarantee of physiological activities. Hence we find in Neijing: “Yin is installed in the interior as the material foundation of yang, while yang remains on the exterior as the manifestation of the function of yin.”