Introduction:The terms “Xu” (虚) and “Shi” (实) have significant meanings in TCM. What do they really mean?
“Xu” and “Shi” refer to the nature of pathological changes and are extremely important in the differentiation of syndromes.
Thus, to tonify (补) is to treat “Xu”, and to purge (泻) is to treat “Shi”; this is a fundamental principle in TCM treatment. However, while it may seem easy to recognize the “Xu” and “Shi” of pathological changes and treatment methods, accurately differentiating and applying them is quite challenging.
Based on literature review and clinical experience, the meanings of “Xu” and “Shi” are summarized as follows for research purposes, which may assist in the differentiation and treatment of syndromes.
When analyzing the “Xu” and “Shi” of pathological changes during syndrome differentiation, it has various meanings that should not be confused, as this would affect the accuracy of the differentiation. Upon detailed analysis, there are approximately the following meanings:
1
Distinction of “Xu” and “Shi” based on the strength of Zheng Qi (正气)
The “Shang Han Lun” (伤寒论) states: “When taking the pulse, if the pulse comes quickly and leaves slowly, it is called ‘internal Xu and external Shi’. If the pulse comes slowly and leaves quickly, it is called ‘internal Shi and external Xu’.”
Zhou Chengzhi explains in the “Bian Ping Mai Zhang Ju” (辨平脉章句) that: “The coming and going refers to the pulse’s entry and exit; entry and exit refer to the internal and external aspects of Yin, Yang, blood, and Qi. If the pulse comes quickly and leaves slowly, it indicates more Qi is exiting than entering, hence external Shi; if the pulse comes slowly and leaves quickly, it indicates more Qi is entering than exiting, hence internal Shi. External Shi indicates weak Yin’s absorptive power, thus internal Xu; internal Shi indicates weak Yang’s driving power, thus external Xu.”
The entry and exit of pulse Qi, whether Yin or Yang, all belong to the category of Zheng Qi. Therefore, the “Xu” and “Shi” mentioned here refer to Zheng Qi and do not include Xie Qi (邪气).
2
Distinction of “Xu” and “Shi” based on the strength of Xie Qi (邪气)
The “Su Wen” (素问) states: “When Xie Qi is strong, it is Shi; when the essence Qi is depleted, it is Xu.”
Zhang Zhizong explains in the “Su Wen Ji Zhu” (素问集注) that: “Xie Qi refers to the evils of wind, cold, heat, and dampness, while essence Qi refers to Ying Qi (营气) and Wei Qi (卫气). Since Xie Qi can be strong or weak, when Xie Qi is strong, it is Shi; when Zheng Qi is weak, it is Xu. ‘Deplete’ means to lose, which can be due to the invasion of Xie Qi.”
Japanese scholar Tanba Genkan states in the “Su Wen Shi” (素问识) that: “When Xie Qi invades the body, it must first take advantage of the weakness of essence Qi to enter. If it enters and the essence Qi is strong, both will be strong, resulting in Shi, such as in the case of a full pattern of cold damage. If Xie Qi enters and the essence Qi cannot resist it, it is taken by Xie Qi, resulting in Xu, such as in the case of a direct attack of cold damage.”
Whenever Xie Qi is present, regardless of its strength, it is considered a Shi pattern; whenever there is no Xie Qi present, only the depletion of essence Qi exists, regardless of whether it pertains to Qi or blood, in the organs or bowels, it is considered a Xu pattern.
This concept is widely applied in clinical practice.
3
Distinction of “Xu” and “Shi” based on the presence or absence of disease
There are two situations regarding the distinction of disease and non-disease.
1. Considering disease as Shi and non-disease as Xu
As stated in the “Nan Jing” (难经): “External pain and internal comfort indicate external Shi and internal Xu; internal pain and external comfort indicate internal Shi and external Xu.”
When Xie Qi invades externally, it causes external pain, indicating that the evil is on the surface. For example, in cases of Gui Zhi Tang (桂枝汤) or Ma Huang Tang (麻黄汤), one may only see symptoms like chills, fever, and body aches, which are external manifestations. Since the evil has not penetrated internally, the internal aspect is comfortable and not suffering.
When the disease evil is external, it is termed external Shi, and since there is no internal suffering, it is termed internal Xu, which is in contrast to external Shi, not indicating a deficiency of Zheng Qi internally;
When the disease evil occurs internally and causes internal pain, regardless of whether it is cold or heat, it is termed internal Shi based on the location of the disease evil; since the disease evil is not external, there is no external suffering, thus termed external Xu.
Thus, Shi indicates disease, while Xu indicates non-disease, which is also a contrasting meaning.
2. Considering disease as Xu and non-disease as Shi
As stated in the “Nan Jing”: “Yang Xu and Yin excess lead to sweating and recovery; purging leads to death; Yang excess and Yin Xu lead to sweating and death; purging leads to recovery.”
Hua Shou explains that, “When the disease is considered Xu, the non-disease is considered excess. Only when it is Xu can the evil invade; only when it is excess can the evil not enter. This refers to the concept of exterior disease harmonizing with interior disease, as mentioned in the ‘Wai Tai’ (外台), which refers to the transmission of cold damage. When the exterior disease harmonizes with the interior, sweating can be used to resolve the exterior; however, if purging is applied, it harms the unillness of Zheng Qi and causes the exterior evil to penetrate deeply into the interior, leading to death.”
Yang excess indicates that Zheng Qi is abundant externally and the exterior is not ill; Yin Xu indicates that essence Qi is deficient internally and Xie Qi is strong in the organs. When Xie Qi is strong in the organs, purging can lead to recovery; however, if sweating is induced, it may harm the exterior Yang, leading to both exterior and interior deficiency, and the Xie Qi becomes more solidified and cannot be resolved, thus leading to death.
Thus, this “Xu” and “Shi” are interchangeable terms for disease and non-disease, which is contrary to the meaning in the “Forty-Eighth Difficult” (四十八难).
4
Distinction of “Xu” and “Shi” based on the severity of disease
Generally, mild disease is considered Xu, while severe disease is considered Shi.
The differentiation between the major and minor chest obstruction syndromes in the “Shang Han Lun” belongs to this category.
The “Shang Han Lun” states: “In cases of cold damage lasting six to seven days, if there is a hard, painful area under the heart, with a deep and tight pulse, it is a major chest obstruction syndrome, treated with Da Xianxiong Tang (大陷胸汤). If there is a minor chest obstruction, located under the heart, with pain upon palpation and a floating, slippery pulse, it is treated with Xiao Xianxiong Tang (小陷胸汤).”
The chest obstruction syndrome generally belongs to the condition of Yang heat and Shi evil accumulating in the chest, hence termed “chest obstruction heat Shi”.
If the heat evil is strong and deeply accumulated, it is termed major chest obstruction, thus treated with Da Huang (大黄), Mang Xiao (芒硝), and Gan Sui (甘遂) to purge the heat Shi; if the heat evil is mild and superficially accumulated, it is termed minor chest obstruction, thus treated with Huang Lian (黄连), Ban Xia (半夏), and Gua Lou (瓜蒌) to clear heat and disperse the obstruction.
Although there are differences in severity, they are both considered heat Shi patterns.
The Xie Xin Tang (泻心汤) syndrome, which is a Xu Pi syndrome, is due to the prior deficiency of Yang Qi in the middle burner, with the formless heat evil penetrating internally, thus the various forms of Ban Xia Xie Xin Tang (半夏泻心汤), Sheng Jiang Xie Xin Tang (生姜泻心汤), and Gan Cao Xie Xin Tang (甘草泻心汤) treat differently, but all use Ren Shen (人参), Da Zao (大枣), Gan Jiang (干姜), and Gan Cao (甘草) to warm and tonify the Yang Qi of the middle burner as a base, supplemented with Huang Qin (黄芩) and Huang Lian (黄连) to clear the formless heat evil penetrating internally, thus the Pi syndrome is fundamentally a Xu pattern.
The “Shang Han Lun” states: “When the disease arises from Yang, purging leads to chest obstruction; when the disease arises from Yin, purging leads to Pi.”
Thus, the chest obstruction syndrome is termed “chest obstruction heat Shi”, while the Pi syndrome is termed: “This is not heat obstruction, but due to deficiency in the stomach, causing Qi to rise against it, hence the hardness.” This indicates that the heat in chest obstruction is severe, thus it is a Shi pattern, while the mild heat in Pi is a Xu pattern.
5
Distinction of “Xu” and “Shi” based on cold and heat
First, cold is considered Xu, while heat is considered Shi.
The “Su Wen” states: “Yang is Shi, Yin is Xu”, which carries such meaning. Tanba Genkanin the “Yao Zhi Tong Yi” (药治通义) states: “Cold leading to diarrhea is widely recognized as a major Xu that requires tonification; tidal heat and delirium are widely recognized as a major Shi that requires purging.”
The former is a Xu cold pattern, while the latter is a Shi heat pattern.
Secondly, cold is considered Yin Shi and Yang Xu, while heat is considered Yang Shi and Yin Xu.
The “Su Wen” states: “When Yin is excessive, it leads to internal cold; when Yang is deficient, it leads to external cold”, which belongs to the former; “When Yang is excessive, it leads to external heat; when Yin is deficient, it leads to internal heat”, which belongs to the latter. This reflects the opposing nature of Yin and Yang, each according to its category.
6
Distinction of “Xu” and “Shi” based on the form of disease
This primarily involves the accumulation, dispersion, emptiness, and hardness of the disease.
For example, Qi stagnation upwards is Shi, while downward sinking is Xu; Qi accumulation internally is Shi, while external dispersion is Xu.
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Distinction of “Xu” and “Shi” based on wind evils
The “Ling Shu” (灵枢) states: “Wind that comes from its native place is called Shi wind, which promotes growth and nourishes all things; wind that comes from the opposing direction is called Xu wind, which harms people and is deadly. One should be cautious of Xu wind and avoid it.”
Zhang Jiebin explains: “The native place refers to the place where Tai Yi resides. For example, when the moon is in the Rat position, the wind comes from the north, which is the correct winter Qi; when the moon is in the Rabbit position, the wind comes from the east, which is the correct spring Qi; when the moon is in the Horse position, the wind comes from the south, which is the correct summer Qi; when the moon is in the Rooster position, the wind comes from the west, which is the correct autumn Qi. The four corners and twelve positions all have such Qi.”
When the Qi is in its correct position, Zheng Qi is abundant, thus it is called Shi wind, which can promote growth and nourish all things. When the Qi is lost from its correct position, Zheng Qi is insufficient, thus it is called Xu wind, which can harm people and is deadly, and should be avoided.
In the “Nei Jing” (内经), Xu wind and Shi wind are also referred to as “Xu evil and Zheng evil”, as stated in the “Ling Shu”: “Xu evil is within the body, causing sweating and movement; Zheng evil is within the person, causing subtle changes…”
Based on the above analysis, the concept of “Xu” and “Shi” in TCM is extremely broad, encompassing multiple aspects.
Both Zheng Qi and Xie Qi can have Xu and Shi, thus in pathological changes and syndromes, there is always a presence of Xu and Shi. Simply relying on the phrase from the “Tong Ping Xu Shi Lun” (通评虚实论) ‘When Xie Qi is strong, it is Shi; when essence Qi is depleted, it is Xu’ cannot encompass the full scope of Xu and Shi.
Note:This article was published in the “Selected Lectures on TCM”, compiled by the Graduate Class of TCM Research Institute, People’s Health Publishing House, October 1980. This public account is used for academic exchange only; if there is any infringement, please contact for deletion, and please indicate the source when reprinting.
Cover image source: Internet.
