Understanding Yin & Yang 认识阴阳
However, the yin and yang properties of things are relative, not absolute.
1) Take spring and summer for example. It is relatively hotter in summer and cooler in spring, so summer pertains to yang and spring to yin. Take spring and winter for another example. It is relatively colder in winter and warmer in spring, so here, winter pertains to yin while spring pertains to yang.
2) Take daytime and night for example. Daytime pertains to yang while night to yin. However, daytime can be further divided into two phases: morning and afternoon. Since Yang-Qi ascends in the morning and descends in the afternoon, relatively, morning is more yang (yang within yang) than the afternoon (yin within yang).
Interaction Between Yin & Yang
The yin and yang aspects within an object or phenomenon are not simply arbitrary divisions. In fact they are in constant and complicated relationship. Such interactions between yin and yang give rise to the origination, development and change of things.
1. Opposition of Yin and Yang
Since yin and yang are opposite to each other in nature, they constantly repel and restrain each other. If both yin and yang are quite powerful, such a mutual repelling and restraining activity will maintain general equilibrium of things. If one side is weak and the other side is strong, the strong side will restrain the weaker side, consequently damaging the general balance of things. The so-called "contrary treatment,"one of the basic therapeutic principles in TCM, is developed in the light of the opposition between yin and Yang.
For example, the treatment of cold disease with drugs hot in nature means to use heat (yang) to control cold (yin), while the treatment of febrile disease with drugs cold in nature means to use cold drugs (yin) to restrict heat (yang).
2. Interdependence Between Yin and Yang
Interdependence between yin and yang indicates that yin and yang depend on each other for existence in an object. In conception, yin and yang must exist in pair and no side can exist independently. In nature, yin and yang within an object can transform into each other under certain conditions, implying that no one can exist without the existence of the other. In the light of such interdependence, TCM pays much attention to mutual transformation between Qi (yang) and blood (yin) in the treatment of diseases due to certain deficiency.
For example, the patients with blood deficiency can be treated by supplementing Qi to produce blood, the patients with Qi deficiency can be treated by supplementing blood to promote Qi, the patients with yin deficiency can be treated by supplementing yang to generate yin; and the patients with yang deficiency can be treated by supplementing yin to promote yang.
3. Mutual Consumption of Yin and Yang
This is also called the “waning and waxing between yin and yang,” which implies that, in the interaction between yin and yang, one side is developing while the other side is declining and vice versa. Such a state manifests in different ways, such as yin waning while yang waxing, yin waxing while yang waning, yang waning leading to yin waxing, and yang waxing leading to yin waning.
Under normal condition, wane and wax between yin and yang are maintained to a certain range. Waning to a certain degree will turn to waxing and waxing to a certain level will change into waning. In this way wane and wax will never be excessive. Alternation and repetition of wane and wax maintain a dynamic balance between yin and yang If wane and wax between yin and yang exceeds the normal level, relative predominance or relative decline of either yin or yang will arise, consequently damaging the dynamic balance between yin and yang and leading to imbalance of yin and yang.
4. Mutual Transformation between Yin and Yang
If yin or yang wanes or waxes to the extreme point, it will transmute into the opposite. That means yin will change into yang and yang into yin. The key element involved in such a mutual transformation is the degree of wane and wax. The degree that leads to transformation is termed "extreme point" or "excess" in TCM. The Huang di Neijing (Inner Canon of the Yellow Emperor), suggests that "extreme cold generates heat," "extreme heat generates cold," "excessive yin turns into yang" and "excessive yang changes into yin."
The typical mutual transformation process of yin and yang is well signified by the variations of yin and yang in the four seasons of a year. From spring to summer, yang waxes while yin wanes. However when such a transformation reaches the peak — the Summer Solstice — yin begins to grow while yang starts to wane away. From autumn to winter, yin waxes while yang wanes. But again, when we see the transformation reach the peak — the Winter Solstice — yang begins to wax while yin starts to wane. Such a change exactly explains the idea that "excessive yin turns into yang" and "excessive yang changes into yin."
Yin & Yang in Human Body
It is said in the Huang di Neijing, "man has a physical shape, which is inseparable from yin and yang." Generally speaking:
the upper part of the body pertains to yang while the lower part to yin;
the exterior pertains to yang while the interior to yin;
the back pertains to yang while the chest and the abdomen are yin;
the chest pertains to yang in relation to the abdomen because it is located in the upper part of the body, and the abdomen to yin because it is located in the lower part of the body;
the lateral sides of the four limbs pertain to yang while the medial sides to yin;
the five Zang-organs pertain to yin because they store essence;
the six Fu-organs pertain to yang because they transport and transform food, but never store it.
Each organ itself can be further divided into yin and yang aspects, such as heart-yin and heart-yang, kidney-yin and kidney-yang, etc.
When the balance between yin and yang in the body is damaged, it leads to various diseases known as "imbalance between yin and yang." For example, if one is “yin deficient,” this person often experiences agitation, dehydration, dryness, heat; if one is “yang deficient,” then this person often experiences coldness, fatigue, impotence, etc.