五行

The theory of the five elements, along with the theory of yin and yang, originated from ancient China. It is the cognition of the material world by people in ancient China and was used to explain and analyze things in the natural world. The theory of the five elements, together with the theory of yin and yang, painted a splendid picture in ancient China. Later on, the theory of the five elements was applied to TCM and became one of the important components in theoretical system of TCM.

People in ancient China believed that wood, fire, earth, metal and water are indispensable in daily life and are keys to the variations in the natural world. For example, people drink water and use fire to cook food; metal and wood can be made into various tools; earth ensures the growth of all things. Besides, these elements are interrelated and influence each other. Such a cognition and understanding eventually formed the theory of the five elements.

Implication of the five elements

In Chinese, "wu" refers to five, here means wood, fire, earth, metal and water; "xing" means movement and transformation. So "wuxing"(the five elements) actually refers to the movement and transformation of these five elements including their interrelationships.

The theory of the five elements holds that all things in the natural world are derived from wood, fire, earth, metal and water. So they all bear the basic properties of these five elements and maintain a harmonious balance through the activities of constant inter-promotion and inter-restraint.

Categorization of things according to the properties of the five elements

Since wood, fire, earth, metal and water are five categories of the main objects in the natural world and possess specific properties and depend on each other to exist, people in ancient China divided and explained the properties of things according to the characteristics of the five elements.

As to the characteristics of the five elements, the early understanding concentrated on the primary properties of wood, fire, earth, metal and water in the natural world, such as "water moistens and flows downward", "fire flames up", "wood can be flexed and extended", "metal can be changed in form" and "earth can grow crops", etc. In order to explain the properties of more things, people abstracted the properties of the five elements for extensive application and extended their implications. For example, the properties of flexing and extending, growth and development as well as free activity all pertain to the category of wood; warmth, heat, ascending and brightness all pertain to the category of fire; reception, cultivation and transformation all pertain to the category of earth; change, depuration and astringency all pertain to the category of metal; and moistening, downward movement, cold and coolness as well as closure and storage all pertain to the category of water.

Properties and extended meaning of five elements

In the light of the basic properties of the five elements, analogy and induction can be used to categorize things in order to decide the properties of different things. The first step is to compare the image, properties and functions of things with the abstracted properties of the five elements respectively. If it is similar to the properties of one element, then it pertains to the category of that element. For example, the sun rises in the east according to the geographical location of China. In this case the east is similar to wood in properties, so it pertains to wood. The south is hot and similar to fire in properties. So the south pertains to fire. The west is mountainous with high terrain and cold climate, similar to the properties of metal. That is why the west pertains to metal. The north is cold and snowy with deeply latent terrestrial qi, similar to the properties of water. Thus the north pertains to water. The central region of China is mild in climate and rich in crops, similar to the properties of earth. Therefore the central region pertains to earth. Take the four seasons for another example. Spring, characterized by gradual ascendance of yang-qi, warm weather and resuscitation of all things, is similar to the properties of wood. So spring pertains to wood. Summer, characterized by hot weather and luxuriant growth of all things, is similar to the properties of fire. That is why summer pertains to fire. Autumn, characterized by decrease of yang-qi and decline of all things in the natural world, is similar to the properties of metal. Thus autumn pertains to metal. Winter, characterized by cold weather and storage of all things, is similar to the properties of water. For this reason winter pertains to water.

For dealing with things difficult to compare directly with the abstract properties of the five elements, inference and deduction can be used to decide the properties of these things in the light of the properties of other related things induced according to the defined properties of the known things. Take the liver for example. The physiological characteristic of the liver is to function freely, qtute similar to the properties of wood. So the liver pertains to wood in the five elements. However, the gallbladder, tendon and eyes are difficult to compare with the properties of the five elements directly. Because these organs and tissues are intrinsically related to the liver, they also pertain to wood.

In this way TCM classifies, with the methods of categorization, inference and deduction, various things in the natural world as well as the viscera, organs and tissues in the human body respectively into the categories of wood, fire, earth, metal and water according to their properties, thus formulating a structural system of the five elements with close interrelationship between the internal and external environments of the body. This structural system of the five elements mainly includes the five flavors, the five colors, the five transformations, the five kinds of qi, the five directions and the five seasons as well as the five zang-organs, the five fu-organs, the five sensory organs, five constituents (tendon, vessel muscle, skin and bone), the five emotions, the five kinds of liquids and the five states of pulse in the human body as illustrated in the following table.

The structural system of the five elements

Nature

Human body

Interactions among the five elements

The five elements possess specific properties respectively. They are related to each other and act on each other. Though the five categories of things classified according to the properties of the five elements are complicated and changeable, they still can be expounded with the theory of the five elements. The interactions among the five elements are either normal or abnormal. The former includes inter-promotion and inter-restraint and the latter includes over restraint (or subjugation) and reverses restraint which are actually the abnormal manifestations of inter-restraint.

1.Inter-promotion and inter-restraint among the five elements

①Inter-promotion

Inter-promotion means that one thing bears the effect of promoting or generating another in the five elements. The order of inter-promotion among the five elements follows certain rules and forms a circle, i. e. wood promoting fire, fire promoting earth, earth promoting metal, metal promoting water and water promoting wood. The one that generates is called "mother" while the one that is generated is termed "child". So the inter-promotion relationship among the five elements is also called mother-child relationship. Take fire for example. The one that generates fire is wood and the one that is generated by fire is earth. So wood is the mother of fire and earth is the child of fire.

②Inter-restraint

Inter-restraint means that one thing controls and restrains another thing in the five elements. The order of inter-restraint also follows certain rules and forms a circle, i. e. wood restraining earth, earth restraining water, water restraining fire, fire restraining metal and metal restraining wood. Since the thing being restrained "cannot dominate the one that controls it" and the thing restraining another "dominates the one that it controls"; , the inter-restraint relationship among the five elements is also known as the relationship of domination and submission. Take water for example. The one that restrains water is earth and the one that is restrained by water is fire. For this reason, earth is called the dominator of water and fire is called the submitter of water.

③The relationship between inter-promotion and inter-restraint

Inter-promotion and inter-restraint among the five elements are in fact inseparable. Without promotion, nothing can grow and develop; without restraint, there will be no way to prevent harm caused by excessive development of things. Only when restraint exists in promotion and promotion in restraint can the normal development and harmonious balance of things be maintained.

Besides, inter-promotion and inter-restraint among the five elements restrict each other to avoid harm resulting from excessive promotion and over restraint. For example, wood restrains earth, earth generates metal and metal, in turn, restrains wood. If wood is too powerful, it will over restrain earth and bring on harm. However, metal generated by earth can protect earth by restricting wood. Again take wood for example. Only under the normal restraint of metal can wood generate fire. If wood excessively generates fire, fire will become superabundant and turn to restrain metal. Consequently metal will be weakened in restraining wood and wood will become feeble in generating fire. In such a way automatic regulation within the five elements is realized through mutual restriction between inter-promotion and inter-restraint.

Full line：Generation
Dotted line：Restriction

2.0ver restraint and reverse restraint

①Over restraint

Over restraint refers to an abnormal state in which one element among the five elements excessively restrains another element. The order of over restraint is the same as that of inter-restraint, i. e. wood over restraining earth, earth over restraining water, water over restraining fire, fire over restraining metal and metal over restraining wood. There are two causes responsible for over restraint:

One is that one element among the five elements becomes too powerful and, in turn, excessively restrains the element that it normally restrains, damaging the normal restraint relationship between them. For example, if wood is too powerful, it will excessively restrain earth; if water is too strong, it will excessively restrain fire.

The other is that one element among the five elements becomes weak and therefore provides the element normally restraining it a chance to excessively restrain it, damaging the normal restraint relationship between them. For example, if earth becomes weak, it will be excessively restrained by wood; if water is weak, it will be excessively restrained by earth.

②Reverse restraint

Reverse restraint refers to an abnormal state in which one element among the five elements reversely restrains and bullies another element. That is why this phenomenon is called reverse restraint. The order of reverse restraint is just opposite to that of inter-restraint,i.e. wood reversely restraining metal, metal reversely restraining fire, fire reversely restraining water, water reversely restraining earth and earth reversely restraining wood. There are two causes responsible for reverse restraint:

One is that one element among the five elements becomes very powerful and turns to restraint the element that it is normally inferior to, damaging the normal inter-restraint relationship between them. For example, if wood becomes too powerful, it will reversely restrain metal, if fire becomes too strong, it will reversely restrain water.

The other is that one element among the five elements becomes weak and is restrained by the one that it is normally superior to, damaging the normal inter-restraint relationship between them. For example, if metal becomes weak, it will be reversely restrained by wood; if earth is weak, it will be reversely restrained by water.

Besides, the abnormal change of inter-promotion relationship is called mutual involvement of the mother and the child. The mother involving or affecting the child means that the disorder of the mother-element involving or affecting the child-element. The order of such an involvement or affection is the same as that of inter-promotion. The child involving or affecting the mother means that the disorder of the child-element involving or affecting the mother-element. The order of such an involvement or affection is just opposite to that of inter-promotion.

Application of the theory of the five elements in TCM

1. Explaining the physiological functions of the five zang-organs and the relationships among them

The theory of the five elements explains the physiological characteristics and functions of the five zang-organs according to the attributes of the five elements, pairing each of the five zang-organs with the corresponding one of the five elements. For example, wood is characterized by free development while the liver prefers freedom to stagnation, so the liver pertains to wood; fire is hot and tends to flame up while heart-yang warms the whole body, so the heart pertains to fire; earth receives and generates while the spleen transforms food nutrients and is the source of qi and blood, so the spleen pertains to earth; metal depurates and astringes while lung-qi maintains inside and normally descends, so the lung pertains to metal; water moistens and closes while the kidney stores essence and manages water metabolism, so the kidney pertains to water.

Some of the intrinsic relationships among the functional activities of the five zang-organs also reflect the relationships of inter-promotion and inter-restraint. So they can be explained with the theory of inter-promotion and inter-restraint among the five elements. In terms of inter-promotion, the state of wood promoting fire corresponds to the state of the liver promoting the heart because liver-blood can nourish heart-spirit; the state of fire promoting earth corresponds to the state of the heart promoting the spleen because heart-spirit can regulate the transporting and transforming functions of the spleen; the state of earth promoting metal corresponds to the state of the spleen promoting the lung because the spleen can transports and transforms food nutrients to nourish the lung; the state of metal promoting water corresponds to the state of the lung promoting the kidney because the lung depurates and descends qi to help the kidney receive qi; the state of water promoting wood corresponds to the state of the kidney promoting the liver because kidney-yin can nourish liver-yin. In terms of inter-restraint, the state of wood restraining earth corresponds to the state of the liver restraining the spleen because liver-qi relieves stagnation of spleen-earth to bring the transporting and transforming functions of the spleen into full play; the state of wood restraining water corresponds to the state of the spleen restraining the kidney because the spleen governs metabolism of water to prevent edema due to abnormal flow of kidney-water; the state of water restraining fire corresponds to the state of the kidney restraining the heart because sufficient kidney-yin can assist the heart to control hyperactivity of heart-fire; the state of fire restraining metal corresponds to the state of the heart restraining the lung because the warmth of heart-yang can prevent lung-qi from excessively depurating and descending; the state of metal restraining wood corresponds to the state of the lung restraining the liver because lung-qi depurates and descends to prevent liver-qi from excessively ascending.

2. Explaining interactions among the five zang-organs

The human body is an organic whole. The five zang-organs coordinate with each other physiologically and affect each other pathologically. Under pathological condition, disorder of one organ may be transmitted to another. According to the theory of the five elements, there are two aspects of pathological transmission among the five zang-organs: one includes over restraint and reverse restraint, the other includes disorder of the mother-organ involving the child-organ and disorder of the child-organ involving the mother-organ.

Over restraint and reverse restraint are pathological transmissions due to abnormal change of inter-restraint relationship. Over restraint refers to transmission of disease due to excessive restraint, the order of which is the same as that of inter-restraint. For example, if liver-qi attacks the spleen, spleen-qi will be weakened, leading to dysfunction of the spleen. Reverse restraint refers to transmission of disease due to opposite restraint, the order of which is just contrary to inter-restraint. For example, the lung normally restrains the liver. But if liver-fire becomes hyperactive and invades the lung, it may lead to failure of the lung to depurate.

Mutual involvement or affection of the mother-organ and the child-organ reflects pathological transmission due to abnormal change of inter-promotion relationship. Disorder of the mother-organ or affecting of the child-organ infers that the disease is transmitted from the mother-organ into the child-organ, the order of which is the same as that of inter-promotion. For example, hyperactivity of liver-fire may affect the heart and bring on hyperactivity of heart-fire, leading to superabundance of both heart-fire and liver-fire. Such a transmission is called disorder of the mother-organ involving the child-organ. Disorder of the child-organ involving or affecting the mother-organ indicates that the disease is transmitted form the child-organ into the mother-organ, the order of which is just opposite to that of inter-promotion. For example, prolonged deficiency of liver-yin affects the kidney and causes deficiency of kidney-yin. Such a transmission is called disorder of the child-organ involving the mother-organ, also known as "the child-organ consuming qi of the mother-organ".

3. Guiding clinical diagnosis

Since the five zang-organs pair with the five elements, the five colors, the five flavors and the five pulses respectively, and because the disorders of the internal organs can manifest on the surface of the body, clinically the theory of the five elements can be used to analyze the changes of complexion, taste and pulse in order to decide which viscus and meridian are involved.

① Diagnosis according to complexion, taste and pulse

The five colors, the five flavors and the five pulses correspond to the liver, the heart, the spleen, the lung and the kidney respectively. So they can be directly used to diagnose disease. For example, bluish complexion, preference for sour flavor or sour taste in the mouth and taut pulse indicate liver disease; reddish complexion, bitter taste in the mouth and full pulse indicate heart disease; yellowish complexion, sweet taste in the mouth and slow pulse indicate spleen disease; whitish complexion, acrid taste in the mouth and floating pulse indicate lung disease; and blackish complexion, salty taste in the mouth and deep pulse indicate kidney disease.

②Deciding the transmission of disease according to complexion, taste and pulse

If the complexion, taste and pulse of the patient do not agree with the nature of visceral disorder, it shows that the disorder is already changed among the five zang-organs. Then the theory of the five elements must be used to analyze the transmission. Take spleen deficiency for example. Instead of displaying the manifestations of yellowish complexion, sweet taste in the mouth and slow pulse, there are signs of bluish complexion, sour taste in the mouth and taut pulse which are normally the manifestations of liver disorder. It shows that liver disease has been transmitted to the spleen, i. e. wood over restraining earth. Take lung disease for another example. Instead of displaying the manifestations of whitish complexion, acrid taste in the mouth and floating pulse, there are signs of reddish complexion, bitter taste in the mouth and full pulse which are normally the manifestations of heart disease. It shows that heart disease has been transmitted to the lung, i.e. fire over restraining metal.

Of course. using the theory of the five elements to diagnose disease is only one of the methods used in clinical diagnosis. In order to reveal the nature of disease and make correct diagnosis, this method should be used together with other methods for differentiation of syndrome, such as yin and yang, zang xiang (visceral and their manifestations) , qi, blood and body fluid.

4. Guiding the treatment of disease

In the treatment of disease, the theory of the five elements is mainly used to control the transmission of disease and decide therapeutic principles.

①Controlling the transmission of disease

The pathological changes of the five zang-organs, according to the phenomena of over restraint, reverse restraint and mutual involvement of the mother-element and the child-element among the five elements, can affect and transmit to each other. Thus in clinical treatment of the affected viscus, other viscera to be possibly involved must be taken into consideration by taking preventive measures in advance to control the transmission of disease. However, the following two points have to be borne in mind. One is to select the viscera that are subject to transmission for treatment. For example, liver disease, according to the theory of five elements, tends to transmit to the heart, the lung, the spleen and the kidney. However, clinically the organ that is more frequently to be affected by liver disease is the spleen. So, preventive measures should be taken in advance to protect the spleen in the treatment of liver disease. The other is that the treatment should be done according to the functional state of the viscera. Though liver disease tends to transmit to the spleen, the transmission usually results from the abnormal changes of spleen function. If the spleen is sufficient in qi, healthy in function and powerful in resistance, liver disease is difficult to transmit to the spleen and no measures need to be taken to deal with the spleen. If the spleen is too weak to resist attack of liver disease, it will be invaded by liver disease. In this case measures must be taken to prevent further transmission in treating the spleen.

②Decidng therapeutic principles

Visceral diseases, according to the inter-promotion and inter-restraint relationships among the five elements, may affect each other. Clinically the theory of the five elements can be used to readjust the relationships among the five zang-organs to realize the aim of treatment. Usually the therapeutic principles are decided in the light of inter-promotion and inter-restraint relationships.

The therapeutic principle decided according to inter-promotion relationship is termed "tonifying the mother-organ and purging the child-organ".

Tonifying the mother-organ is a therapeutic principle used to treat deficiency syndrome. It is also known as "tonifying the mother-organ in the treatment of deficiency syndrome". This principle is mainly used to treat deficiency syndrome due to failure of the mother-organ to promote the child-organ. The aim of this principle is to strengthen the weakened child-organ by tonifying the mother-organ. Take insufficiency of liver-yin for example. Since it results from malnutrition of liver-wood due to insufficiency of kidney-yin, it can be treated by nourishing kidney-yin. Since the kidney is the mother-organ of the liver, tonifying kidney-water can promote liver-wood. That is why this therapy is called "enriching water to nourish wood."

Purging the child-organ is a therapeutic principle used to treat excess syndrome, also known as "purging the child-organ in treating excess syndrome". This principle is mainly used to treat excess syndrome resulting from disorder of the mother-organ by reducing exuberant pathogenic factors through purging the child-organ. For example, superabundance of heart-fire due to hyperactivity of liver-fire can be treated by purging the heart because the heart is the child-organ of the liver. That is why liver-fire can be reduced by purging heart-fire.

The principle decided according to inter-restraint relationship is called "inhibiting the strong organ and supporting the weak organ"; .

The abnormal states of inter-restraint among the five elements are over restraint and reverse restraint. In visceral disease, the manifestations of such abnormal relationships are signified by a series of pathological changes resulting from visceral imbalance. The principle of inhibiting the strong organ and supporting the weak organ means to correct visceral imbalance and restore visceral harmony in function. Inhibiting the strong organ and supporting the weak organ, two different sides of a therapeutic principle, are closely related to each other. The purpose of inhibiting the strong organ is to prevent it from bullying the weak organ while the aim of supporting the weak organ is to correct its deficiency so as to free it from the domination of the strong organ. Inhibiting the strong organ and supporting the weak organ can be used singly. However, they are frequently used in combination in order to quickly correct visceral imbalance. For inhibiting the strong organ, purging therapy is usually used; for supporting the weak organ, nourishing therapy is frequently resorted to. The application of this principle is often marked by simultaneous application of attack and tonification. For example, adverse flow of liver-qi tends to invade the spleen, but deficiency of spleen-qi also makes it easy for liver-qi to attack the spleen. Thus disease resulting from liver-qi attacking the spleen can be treated by inhibiting wood and supporting earth (also known as inhibiting the liver and strengthening the spleen), simultaneously reducing liver-qi and strengthening spleen-qi. With the regulation of both the spleen and the liver, there will be no difficulty in curing spleen disease.