Simply stated, TCM basic premise is the restoration, preservation, and promotion of balance or harmony. This balance can be described through the ever-changing forces of nature, Yin and Yang. Balance is through all aspects of ones life, diet, lifestyle, exercise, work, play, etc., all of which influences our health. Within our bodies, balance is through the body’s vital substances, (Qi, Xue, Shen, and Jing), the pathways and Vessels (Jing Lou), and the internal organs and bowels (Wu Zang Liu Fu).
In early times the Chinese observed that all things in nature are constantly moving and changing while maintaining unity. People in ancient China held that the original state of the universe was "qi"; and that the motion and variation of "qi"; produced two poles known as "yin" and "yang", Such a process of transformation was called " to divide one into two", Since all the things in the universe are produced through the motion and variation of qi, everything can be divided into the aspects of yin and yang, such as the heaven and the earth, the day and the night, the water and fire, upper and lower, cold and heat as well as man and woman, etc. They labeled these Yin and Yang and a symbol, the Taiji emerged to depict this phenomena. The earliest written documents on Yin and Yang dates back to 700 B.C. in the I Ching (Book of Changes).
All of the ancient Chinese wisdom of TCM is based on the fundamental concept of Yin and Yang. Everything in nature is categorized in these two forces. For example, night and day, heat and cold, dryness and wetness, and rest and activity. The Yin qualities express themselves as nurturing and passive such as rest, moisture, cold, and structure. Yang qualities are energetic such as activity, dryness, hot, and function.
Black part in tai ji refers to yin, white pot in clack refers to yang within yin; while white stands for yang and black pot in white means yin within yang. The circle of tai ji refers to “one”, representing the universe and infinities.
The yin and yang aspects within an object or phenomenon are not simply arbitrary divisions. In fact they are in constant and complicated interaction. Such interactions between yin and yang give rise to the origination, development and change of things. The interactions between yin and yang are various in manifestations. The following is a brief description of the major ones.
Interactions Between Yin and Yang
1. Everything in nature is expressed in opposition of Yin and Yang.
This includes living as well as non-living items. 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 weak side, consequently damaging the general balance of things.
2. The interdependance of Yin and Yang
Even though Yin and Yang are two opposing forces, they are co-dependent on each other. Yin cannot exist without Yang and visa versa. Interdependence between yin and yang, literarily yin and yang rooting in each other, 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 solitarily. In nature, yin and yang within an object can transform into each other under certain condition, implying that no one can exist without the existence of the other. That is why it is said in the theory of TCM that "solitary yang cannot exist"; and "solitary yin cannot grow".
3. The mutual consumption of Yin and Yang
Yin and Yang are constantly in a state of change. Balance is always the motive. When either Yin or Yang is out of balance, excess or deficient states arise. This is the basic property of harmony in nature and the human body.
4. Yin and Yang mutually control each other It is important to note that Yin and Yang are not set properties. They are actually transformations of each other. Yin changes into Yang and Yang changes into Yin. For example summer changes into winter, and a hot summer day changes to a cool summer day after a rainstorm passes through.
Clinical Application of Yin and Yang
All of TCM can be reduced to the fundamental concept of Yin and Yang. Every symptom and physical findings can be categorized and reduced as either Yin or Yang. Once the findings are analyzed, the practitioner will either tonify Yin or Yang, or eliminate excess Yin or Yang. One can see the importance of understanding the application of Yin and Yang. Without this concept, there is no reason. Here are some basic qualities of clinical interpretation:
Hot and Cold It has already been established that Yang represents Heat and Yin represents Cold. Therefore, Excess Yang reflects Heat and excess Yin reflects Cold. For example a patient that is experiencing Excess Yang will present with Heat symptoms and a patient experiencing excess Yin will present with a felling of Cold. At the other end, a deficiency of Yang will reflect Cold symptoms and a deficiency of Yin will present with a feeling of Heat.
Excess and Deficiency A state of excitement or excess is a reflection of excess energy, or most likely Yang. This can also manifest as Yin deficiency. This can lead to restlessness, insomnia, heat and palpitations. At the other end, a state of lethargy, depression, feeling of cold, or quiet behavior reflects deficient energy. This is a product of either Yin excess or Yang deficiency.
Dryness or Moisture Dry states such as dry skin, eyes, throat, and stools are a manifestation of either Yin deficiency or Yang excess. Any signs of extra wetness or moisture reflect excess state of Yin or deficient Yang.
Fast and Slow movements In general assessment if a person has a tendency to be a fast passed person that walks and talks rapidly, they have a tendency toward being more “Yang”, or possibly Yin deficient. At the other end, a person who is slow and very lethargic that does everything slow is more “Yin” or Yang deficient in nature.
Onset of Disease Acute conditions that are quick to come are a reflection of Yang activity, Yang excess or Yin deficiency. Conditions that are classified as Chronic, or a gradual onset are a product of Yin, either Yang deficiency or Yin excess.
Yin / Yang and the Human Body Just as everything in nature can be categorized as Yin or Yang, the human topical anatomy can be as well. Each part of the body is relatively Yin or Yang.