What is the Yin Yang Theory?
By Kenneth Wang  OMD  PhD. LAc.Â
 Introduction to Yin and YangÂ
Modern symbol of Yin Yang
陰陽符號
Yin yang theory is a kind of logic, which views things in relation to its whole. The theory is based on two basic components: yin and yang, which are neither materials nor energy. They combine in a complementary manner and form a method for explaining relationships between objects. Gradually, this logic was developed into a system of thought that was applied to other areas. Traditional Chinese Medicine (TCM) is an example of one area where the yin yang theory is used to understand complicated relationships in the body.
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The Origin of the Yin Yang Theory
Early Daoism representation of Yin Yang
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The original concept of yin and yang came from the observation of nature and the environment. “Yin” originally referred to the shady side of a slope while “yang” referred to the sunny side. Later, this thinking was used in understanding other occurrences, which occurred in pairs and had complementary and opposing characteristics in nature. Some examples include: sky and earth, day and night, water and fire, active and passive, male and female and so on. Working with these ideas, ancient people recognized nearly all things could have yin and yang properties. Yin and yang can describe two relative aspects of the same phenomena such as the example of the slope, or they can describe two different objects like sky and earth.
| Usually, yang is associated with energetic qualities. For example, movement, outward and upward direction, heat, brightness, stimulation, activity and excitement are all yang qualities. Yin, on the other hand, is associated with the physical form of an object and has less energetic qualities such as rest, inward and downward direction, cold, darkness, condensation, inhibition, and nourishment. See Table 1 for a description of yin and yang characteristics. |
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General Qualities of Yin and Yang
| Yin
|
Yang
|
| Darkness | Light |
| Moon | Sun |
| Feminine | Masculine |
| Shade | Brightness |
| Rest | Activity |
| West (Sunset = Yin) | East (Sunrise = beginning of Yang) |
| North | South |
| Earth | Heaven |
| Right | Left |
| Flat (like Earth) | Round (like Heaven) |
| Matter | Energy |
| More material/dense | Non-material, rarefied |
These transform into one another.
They are 2 states of a continuum. For Example: Liquid water (Yin) heat – vapor (Yang) – cools – liquid (Yin).
| Yin |
Yang |
| Produces form | Produces energy |
| Grows | Generates |
| Substantial | Non-substantial |
| Matter | Energy |
| Contraction | Expansion |
| Descending | Rising |
| Below | Above |
| Water | Fire |
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Four Main Aspects of Yin and Yang Relationship
- Yin-Yang are opposites
They are either on the opposite ends of a cycle, like the seasons of the year, or, opposites on a continuum of energy or matter. This opposition is relative, and can only be spoken of in relationships. For example: Water is Yin relative to steam but Yang relative to ice. Yin and Yang are never static but in a constantly changing balance. - Interdependent: Can not exist without each other
The Tai Ji (Supreme Ultimate) diagram shows the relationship of Yin & Yang and illustrates interdependence on Yin & Yang. Nothing is totally Yin or totally Yang. Just as a state of total Yin is reached, Yang begins to grow. Yin contains seed of Yang and vise versa. They constantly transform into each other. For Example: no energy without matter, no day without night.
The classics state: “Yin creates Yang and Yang activates Yin”. - Mutual consumption of Yin and Yang
Relative levels of Yin Yang are continuously changing. Normally this is a harmonious change, but when Yin or Yang are out of balance they affect each other, and too much of one can eventually weaken (consume) the other.Four (4) possible states of imbalance:
- Preponderance (Excess) of Yin
- Preponderance (Excess) of Yang
- Weakness (Deficiency) of Yin
- Weakness (Deficiency) of Yang
- Inter-transformation of Yin and Yang.
One can change into the other, but it is not a random event, happening only when the time is right. For example: Spring only comes when winter is finished.
Yin and Yang Theory and History
Yin Yang is the fundamental principle, and the most important theory in TCM, underlying all physiology, pathology & treatment.
Combining the two, we have the four stages of Yin and Yang
With addition of an extra line, the Eight Trigrams (Ba Gua) were formed, illustrating all the directions.
The Eight Trigrams were combined to form 64 hexagrams, symbolizing all possible phenomena of the Universe.
Yin Yang had been understood for many centuries, but was systematically elaborated and written down by Tsou Yen of the Yin Yang (Naturalist) School in the Warring States Period (476-221 BC).
5 Element Theory was developed at same time.
The Naturalist school promoted idea of living in harmony with natural laws. Scholars of this school interpreted natural phenomena and observed how these are reflected in the human body in health and disease. Yin and Yang and the Five Elements became an integral part of Chinese philosophy.
The ancients observed 2 phases of constant cyclical change. Yin constantly changes into Yang & back into Yin again. This can be seen in the changes of four seasons, and the changes throughout a single day (24 Hour Cycle), as seen below.
24 Hour Yin Yang Cycle
(12 PM corresponds to Utmost Yang, while 12AM corresponds to Utmost Yin)
The Application of Yin Yang Theory in Traditional Chinese Medicine
Application in human body structures & Physiological:
Yin
Yang
Front (chest-abdomen) Back Body Head Interior (organs) Exterior (skin, muscles) Below waist Above waist Anterior-medial Posterior-lateral ventral surface of the trunk and limbs back and dorsal surface of the limbs Structure Function Blood/Body Fluids Qi Conservation/storage Transformation/change Yin Organs: Heart, Lung, Small Intestine, Lg. Intestine Liver, Spleen, Kidney, Gall Bladder, Stomach, Bladder Pericardium San Jiao “Solid Organs” “Hollow Organs” Front and Back
Front is more soft and vulnerable (Yin). Back contains spine that holds ribs: protection. When human depicted as crouching, back receives sun (Yang) and front faces the earth (Yin), is in shade and is protected.
All Yang channels (except the Stomach channel) flow on the dorsal or dorsolateral surface of the trunk and limbs. They carry Yang energy and protect the body from pathogenic factors. Yin channels flow on the anterior or anteromedial surface of the trunk and limbs.
Body and HeadÂ
Yang channels either end or begin on the head. Acupuncture points on the head can be used to raise Yang energy . When Yang energy is not cooled by Yin, it may rise to the head, causing signs such as red face and eyes. The head is easily affected by Yang pathogens such as heat and wind. The chest and abdomen (Yin) areas are more easily affected by Yin pathogens such as Cold and Dampness.
Interior and Exterior
The exterior of the body such as the skin and muscles is more Yang. The exterior protects body from attack by external pathogenic influences such as Cold, Wind, etc. The classics state: “Yang is on the outside and protects Yin”.
Below the waist and Above the Waist
Below waist – closer to earth (Yin). Above, closer to Heaven (Yang).
Upper part more affected by Yang pathogens, i.e. wind.
Lower part more affected by Yin pathogens, i.e. cold damp.Anterior/Medial and Posterior/Lateral Surface of the Limbs
Yin channels flow on anterior-medial aspect of trunk/limbs
Yang channels flow on posterior-lateral aspect of trunk/limbsStructure and Function
Structure = something substantial, i.e. Matter (Yin)
Function = something insubstantial, action, energy (Yang)
All parts of the body have a structure (a physical form), and a function (their activity)
However, all is relative. Even within the Yang category of function, there are Yin functions (i.e. storage, conservation) and Yang functions, i.e. transformation, transportation, digestion, excretion.
Within the Yin category of form there are Yin forms (“solid”) and Yang forms (“hollow”)Blood, Body Fluids, and Qi
Qi is Energy, more Yang.
Blood = denser and more material (therefore Yin).
But note that “Xue” (blood) not exactly like our concept of Blood. More like “thicker” form of Qi.Note: there are several types of Qi. Each is relatively more Yin or Yang.Â
Ancestral QI (more Yin, more slow moving. Moves in long slow cycles).
Ying Qi (more Yang than Ancestral Qi, moves with Blood with which it is closely related). Ying is more Yin than Wei Qi.
Wei Qi the most Yang form of Qi. Circulates in the exterior in the daytime to protect us from pathogenic influences, and regulates opening/closing of pores.Conservation/Store (Yin) and Transformation/Change (Yang)
Yin Organs store Blood, Body Fluids, Essence, etc.
Yang Organs constantly transform, transport and excrete the products of digestion.Solid and Hollow Organs (Zang Fu)
Yin Organs are “Solid”: constantly active, involved in production and storage of the body’s vital Substances (Qi Blood, Body Fluids, Essence)
Yang Organs are “Hollow”: receive and circulate but do not store, involved in digestion, transformation, excretion.
Application in Pathology
Clinical signs and symptoms can be interpreted via Yin-Yang theory. When Yin Yang are in dynamic balance and relating harmoniously, there are no symptoms to observe. When Yin and Yang are out of balance, they become separated.Â
For example: a.) Yin does not cool and nourish Yang so Yang rises (headaches, red face, sore eyes, sore throats, nosebleeds, irritability, manic behavior. b.) Yang does not warm and activate Yin (cold limbs, hypo-activity, poor circulation of blood, pale face, low energy. Actual symptoms depend on specific pathologies, which Organ involved, etc.
Yin Yang Deficiency Excess Hypo-activity Hyperactivity Chronic disease/gradual onset Acute disease/rapid onset Slowly changing symptoms Rapid pathological changes Quiet, lethargy, sleepiness Restlessness, insomnia Wants to be covered Throws off bedclothes Lies curled up Lies stretched out Cold limbs and body Hot limbs and body Pale face Red face
Weak voice, no desire to talk Loud voice, talkative Shallow, weak breathing Coarse breathing No thirst/wants warm drinks Thirst esp. for cold drinks Copious, clear urine Scanty, dark urine Loose stools (fluids not transformed) Constipation (damage to fluids by heat) Clear, copious secretions Thick, sticky white/yellow secretions Excessive moisture Excessive dryness (throat, skin, eyes etc.) Degenerative disease Inflammatory disease Pale tongue, white coat Red tongue, yellow coat Empty pulse Full pulse In Practice:
Although Yin-Yang essential foundation for understanding symptoms and signs, the above list of signs is too general. We need to distinguish further to get exact diagnosis. i.e., which Organ is involved, which pathogen involved, which channel involved.
Structure and Function
Without structure, function could not occur. Without function, structure would be meaningless.Mutual Consumption of Yin and Yang
Balance of Yin & Yang is constantly changing. Yin & Yang mutually consume each other.ÂFour different situations:
1) Excess of Yin 2) Excess of Yang 3) Deficiency of Yin 4) Deficiency of Yang Excess of Yin: i.e., when excess Cold in the body consumes the Yang (heat). This is an Excess Cold (Full Cold) condition.
Excess of Yang: i.e., when excess Heat (from Exterior or Interior of body) consumes Body Fluids, leading to Dryness or even Heat. This is an Excess Heat (Full Heat) condition.
Deficiency of Yin (Consumption of Yin): i.e., when the body’s Yin energy is depleted, an apparent excess of Yang results, leading to feelings of “empty heat” (mild but very specific heat symptoms, i.e., flushed cheeks, afternoon fever, sweating at night, heat in extremities. This is Deficiency Heat (Empty Heat) condition (i.e., a condition of deficiency and heat), also called “False Fire”.
Deficiency of Yang (Consumption of Yang). When body’s Yang energy is spontaneously deficient – an apparent excess of Yin results, leading to various symptoms involving cold and hypo-activity Deficiency of Yang can also occur after an Excess Cold condition has damaged Yang. This is an Deficiency Cold (Empty Cold) condition (i.e., a condition of deficiency and cold).
Excess of Yin (Full Cold) Excess of Yang (Full Heat) Excess of Yin is primary aspect Excess of Yang is primary aspect Yin is in true excess Can eventually cause deficiency of Yin Can eventually cause deficiency of Yang    Deficiency of Yang (Consumption of Yang) Deficiency of Yin (Consumption of Yin) (Empty Cold) (Empty Heat of “False Fire”) Decrease of Yang energy is primary aspect Deficiency of Yin is primary aspect Yin only apparently in excess Yang only apparently in excess Inter-transformation of Yin and Yang in Medicine
In medicine also, Yin and Yang transform into one another, but only when conditions are right. The right moment determined by internal qualities of the given situation or phenomenon.
In clinical practice, the above principle is important.Disease is prevented by achievement of BALANCE in lifestyle i.e., excessive work (Yang) without rest leads to deficiency (Yin) of energy i.e., excessive consumption of cold food (Yin) leads to deficiency of body’s Yang energy i.e., smoking (= putting heat (Yang) into Lungs) leads to deficiency of Yin of Lungs (and eventually Kidneys)
The principle is observable in pathological changes seen in disease i.e., Exterior cold (cold weather) can invade body and can change to heat (sore throat). i.e., Deficiency of Yang of i.e., Spleen. Because Spleen Yang is used to transform fluids, these can build up to cause Excess Interior Dampness (Yin).
Diagnostic application :
TCM diagnoses patients according to their disharmony pattern. Preliminarily, all patterns are classified into a system known as the “eight principal patterns.” The “eight principal patterns” contain four pattern pairs: interior and exterior, cold and heat, deficiency and excess, and yin and yang. Among the eight patterns, yin and yang are the most fundamental and essential pattern pair. (See Table .). Generally speaking, yang signs are associated with excitatory, active, hot, progressing externally and developing upward and improving manifestations. Yin signs, on the other hand, are associated with inhibitory, resting, passive, cold, progressing internally and developing downward and worsening manifestations. Table 3 illustrates the clinical signs of yin and yang patterns.Â
Eight Principal Disharmony Patterns
 Disharmony Pattern Yin/Yang Manifestations 1 Exterior Yang An exterior pattern is generated by “external influences” such as wind and cold. (i.e. common cold) 2 Interior Yin An interior pattern is generated by internal disharmony such as a disorder of organ function. 3 Cold Yin A cold pattern is manifested by the signs such as a pale face, cold limbs, aversion to cold, clear urine, or watery stools. The signs are usually related to non-excitatory physiological functions. 4 Heat Yang A heat pattern is manifested by signs of a red face, high fever, dislike of heat, dark urine, or constipation. The signs are usually related to excitatory physiological functions. 5 Deficiency Yin Signs of frail and weak movements, tiredness, shortness of breath, low voice, or dizziness indicate a deficiency pattern. The signs are usually related to lack of energy of normal functions. 6 Excess Yang An excess pattern exhibits signs of heavy movements, heavy and coarse respiration, or discomfort when touched with pressure. The signs are usually related to an excess/accumulation of evils/metabolic waste. 7 Yin Yin General pattern groups for Yin manifestations include interior, cold and deficiency patterns. 8 Yang Yang General pattern groups for Yang manifestations include exterior, heat and excess patterns.
 Yin and Yang signs in the body
Body signs
Yang signs Yin signs Face Red face, fever, hot feeling, agitated and active manner Pale face, low spirit, feels cold, cold limbs, tired and weak, Voice Coarse and strong voice, coarse breath, dry moth, thirst Low voice, reduced appetite, no taste in mouth, little thirst Urine Constipation with awkward smell, dark urine Copious and clear urine Tongue Red and scarlet tongue or yellow and black moss present on tongue Pale and swollen tongue material Pulse Rapid and floating, flooded and strong, slippery and full pulse Slow and sinking, weak, frail pulse
Yin and Yang and the Six Pathogenic Factors
Yin Yang  Wind Cold Heat Dampness Dryness  Summerheat
Application in treatment:
In general, every treatment modality aims to:
- Tonify Yang
- Tonify Yin
- Disperse excess Yang
- Disperse excess Yin
(In practice, depending on the condition, strategies may be combined, for example: disperse excess Yin & tonify Yang)
Herbs and their Yin and Yang Properties TCM also classifies herbs of different “natures” and “tastes” according to their yin and yang properties. Cold and cool nature herbs belong to yin while hot and warm herbs belong to yang. Yin herbs taste sour, bitter and salty, and yang herbs taste sweet and pungent. The yin yang theory also describes the effects of herbs. Herbs with floating and ascending properties are part of yang while herbs with sinking and descending properties are part of yin. In choosing the correct herbs for treatment using TCM, it is essential to first identify the disharmony pattern and then select herbs with the appropriate nature, taste and effect. By following these simple steps, Traditional Chinese Medicine can help maintain the body’s balance and health.
