From Chapter 2: Yin-Yang and The Five Elements

Yin-yang and the five elements are the fundamental principles of TCM. They are a consolidation of the experiences by which the complex physiology and pathology of the human body can be elucidated in simple terms.

The Theory of Yin-Yang

The ancient Chinese believed that every object in nature consists of two opposite yet complementary aspects, which combine to create a whole unit. Yin and yang represent the negative and positive principles of the universe, and are in constant flux. Yin and yang are also the principles underlying Chinese philosophy and metaphysics, and can in fact be applied to everything in the world.

Through repeated tests and long-term observation, it was proven that indeed this theory can be applied to all things, animate and inanimate, including, naturally, human beings. As a product of the universe, the human physiological functions comprise the five elements and yin and yang.

When applied to medical studies, yin and yang are of the greatest importance. As the yin-yang symbol suggests, balance and harmony are the keys. In simple terms, when yin and yang are thrown off balance, disease can easily occur. As discussed in the previous chapter, herbal treatments always take this into consideration.

The concept of yin-yang is abstract but comprehensive. Dynamic, positive, bright, warm, solid and functional attributes are defined as yang while static, negative, dark, cold, liquid and inhibiting attributes are characterized as yin. Thus the sun is yang while the moon is yin; the sky is yang while the earth is yin; daytime is yang while nighttime is yin; fire is yang while water is yin. Sunlight and fire are hot while moonlight and water are cool. By analogy, warm elements are classified as yang and cold elements are taken as yin. Fire is dynamic and tends to ascend and is therefore treated as yang. Water is relatively static and tends to flow down. Thus elements that are active and ascending are described as yang whereas their counterparts being static and descending are described as yin. These are the characteristics of yin and yang. The following table shows some examples of the yin-yang classification.

As shown in Table 1, yin and yang may refer to real matters as well as abstract ideas, and may describe virtually anything. Yin and yang are complementary to and interdependent of each other, yet they are opposite to their counterpart. Being related, they can be transformed to their opposite component under certain conditions. Yin and yang coexist with reference to each other. Yin exists because yang is present. Yin may emerge from yang and vice versa. This idea may be illustrated by the yin-yang-yin cycle. Functional activities in the human body (yang) are supported by the body fluids (yin). This produces nutrients (yin) which support the functional activities (yang). Similarly, functional failure of the internal organs (yang) jeopardizes the digestion of food into usable nutrients (yin).

The water cycle is a good example of yin-yang transformation. The water on earth (yin) vaporizes to gas form (yang); which after condensation to water (yin), falls down on earth again. In TCM terms, one can sometimes witness the transformation of yin and yang in a diseased patient. For example, if a patient has pneumonia, the symptoms tend to be yang symptoms, such as a high fever, restlessness, a flushed face, dry lips and a rapid pulse. If the infection should be complicated by septic shock for example, the symptoms change and become more yin-related, i.e. cold limbs, pallor, profuse sweating and a weak pulse. Similarly, a patient with yin symptoms overtreated with hot-natured drugs may show yang symptoms.

Yin and yang conditions do not remain in a static state. They are in perpetual dynamic equilibrium according to the patient's changing environment. It is this equilibrium of yin and yang that balances the production and regeneration of qi (energy), blood and the body fluids to maintain the healthy physiological functions of the body. This is called "the warning and waxing of yin and yang" in TCM. These theories are utilized to analyze clinical manifestations. A condition of yang excess, as in patients with a high fever, may be complicated by a yin deficiency as shown by dehydration or fluid deficiency. On the other hand, patients who feel very weak may have a yang deficiency, and will therefore be averse to the cold (yin).

The Application of Yin-Yang in Human Anatomy and Physiology

Yin-yang may also describe the relative positioning of the organs with reference to interior or exterior, anterior or posterior as well as inferior or superior. The back, being relatively external to the abdomen, pertains to yang. In TCM, the five sang (solid) organs (heart, liver, spleen, lung and kidney) are referred to as yin organs, while the six fu (hollow) organs (gallbladder, stomach, large intestine, small intestine, bladder and the sanjiao) are the yang organs. In addition, the five sang organs may be subclassified into yin and yang among themselves. The heart and lung located in the upper part of the body are the yang organs whereas the liver and kidney, being in the lower part, are the yin organs. Even an individual sang and fu organ may be divided into yin and yang subsets such as heart yin and heart yang, or kidney yin and kidney yang (refer to Chapter 3). Hence yin and yang are relative and flexible terms. Their implications may vary with different objects and phenomena.

The Application of Yin-Yang in the Illustration of Human Diseases

The yin-yang principle is used for explaining the mechanism of diseases. In TCM context, the healing and life-giving properties of qi protect the body against pathogenic or disease-causing factors. The latter may be further classified as yin and yang pathogenic factors. Diseases caused by yin factors may result in a preponderance of yin and thereby give rise to the cold syndrome. On the contrary, yang factors may cause a preponderance of yang and may result in the heat excess syndrome. The anti-pathogenic qi is generally divided into yang qi and yin fluid. In the case of a yang qi deficiency, the cold deficiency syndrome may occur, while in case of a yin fluid deficiency, the heat deficiency syndrome may appear. Therefore, all disease mechanisms may be deduced in terms of TCM concepts, such as "having an imbalance of yin and yang", "a yang deficiency leading to external cold and a yin deficiency leading to internal heat" and "a yang excess bringing about heat, while a yin excess bringing about cold".

Extreme deficiency of either yin or yang may cause an insufficiency of its counterpart. Finally, there may be deficiency of both yin and yang. In the course of certain chronic illnesses, it is not uncommon to witness insufficient yin fluid production due to yang deficiency or on the contrary, a deficiency of yin fluid may jeopardize the generation of yang qi.

The Application of Yin-Yang in the Diagnosis of Diseases

Tipping the balance of yin and yang triggers off diseases and accounts for their progress. No matter how variable their clinical manifestations are, the fundamentals of diseases may be discussed and analyzed in terms of yin and yang complexes or syndromes. The eight principal syndromes commonly used in TCM in clinical diagnosis and management are based on yin and yang. Exterior syndrome, heat syndrome and excess syndrome all denote yang, while interior syndrome, cold syndrome and deficiency syndrome denote yin . Theimportance of identifying yin and yang is evident from a quotation from the Nei Jing: "A skilful clinician differentiates between yin and yang first after inspecting the [patient's] facial features and feeling the pulse".

The Application of Yin-Yang in the Treatment of Diseases

The causes and manifestations of diseases, as already stated, are due to an excess or deficiency of either yin or yang. Once the nature of the disease pertaining to either yin or yang is assessed, the yin-yang balance should be restored through regulation. This is fundamental to treatment in TCM. Thus yin- and yang-natured herbs are used to treat diseases with yang and yin natures respectively. This is why herbs of a cold nature are prescribed for diseases of the hot type while herbs of a warm nature are chosen for diseases of the cold type. The Nei Jing says, "Monitor the yin and yang and regulate them until equilibrium is achieved. Warm the cold. Fill up any deficiency and purge the excess."

The properties, flavours and effects of traditional Chinese herbs can also be generalized in terms of yin and yang. For instance, herbs of a cold nature, or those that have a moistening effect, denote yin, while warm, hot and dry herbs denote yang; drugs bitter and sour in taste denote yin, while those pungent or sweet in flavour denote yang. Drugs with astringent and descending effects denote yin, while those with ascending and dissipating effects denote yang. In general, herbs with a yin nature are able to dampen the heat in a person and can dissipate the internal heat and hyperactive symptoms. Herbs of a yang nature are able to cause stimulation and excitation, and can thus promote the bodily functions and eliminate the involutional symptoms. The purpose of drugs is, therefore, to rectify the excess or deficiency of yin or yang and restore the equilibrium of the human body in order to achieve the healing effects.