The Eight Principles of Diagnosis
The Eight Principles, namely Yin, Yang, Exterior, Interior, Cold, Heat, Deficiency, and Excess, are one of the theoretical foundations for syndrome differentiation and treatment. Through the four examinations, after grasping the diagnostic information, a comprehensive analysis is conducted based on the depth of the disease location, the nature and severity of the pathogenic factors, and the strength of the body’s righteous Qi, which is then summarized into eight categories of syndromes, known as the Eight Principles of Diagnosis.
The content of the Eight Principles has been discussed in the Neijing (Inner Canon), and Zhang Zhongjing applied it more specifically in the diagnosis and treatment of febrile diseases and miscellaneous diseases. In the Complete Book of Jingyue, there are chapters such as Yin and Yang and Six Transformations, which further elaborate on the Eight Principles. In the Qing Dynasty, Cheng Zhongling advocated for it, making the Eight Principles an important component of diagnostic studies.
Although the manifestations of diseases are extremely complex, they can generally be summarized using the Eight Principles. For example, diseases can be categorized into Yin syndromes and Yang syndromes; the depth of the disease can be divided into Exterior syndromes and Interior syndromes; the nature of the disease can be classified as Cold syndromes and Heat syndromes; the severity of the pathogenic factors can be categorized as Excess syndromes and Deficiency syndromes. Thus, by using the Eight Principles of Diagnosis, the intricate clinical manifestations can be summarized into the four pairs of guiding syndromes: Exterior-Interior, Cold-Heat, Deficiency-Excess, and Yin-Yang, thereby identifying the key aspects of the disease, mastering its essentials, determining its type, predicting its trend, and guiding treatment. Among these, the Yin-Yang principle can also encompass the other six principles, with Exterior, Heat, and Excess syndromes belonging to Yang; and Interior, Cold, and Deficiency syndromes belonging to Yin, thus making Yin-Yang the overarching principle of the Eight Principles.
The Eight Principles serve as a method for analyzing the common characteristics of diseases and are the general framework for various types of syndrome differentiation. In the process of diagnosing diseases, they play a role in simplifying complex situations and are applicable to syndrome differentiation across various clinical specialties. Specifically, the differentiation in each specialty is deepened based on the Eight Principles of Diagnosis.
The Eight Principles of Diagnosis do not imply a strict division of various syndromes into eight distinct areas; they are interconnected and inseparable. For instance, Exterior and Interior are related to Cold and Heat, and Deficiency and Excess are related to Exterior and Interior. Due to the changes in diseases, they often do not occur in isolation but frequently present mixed conditions of Exterior-Interior, Cold-Heat, and Deficiency-Excess, such as simultaneous Exterior and Interior diseases, mixed Deficiency and Excess, and mixed Cold and Heat. Under certain conditions, diseases may also exhibit varying degrees of transformation, such as Exterior pathogens entering the Interior, Interior pathogens emerging from the Exterior, Cold syndromes transforming into Heat, Heat transforming into Cold, Excess syndromes transforming into Deficiency, and Deficiency leading to Excess. At certain stages of disease progression, some phenomena may appear that are contrary to the nature of the disease, such as true Cold presenting as false Heat, true Heat presenting as false Cold, true Deficiency presenting as false Excess, and true Excess presenting as false Deficiency. The same applies to Yin and Yang syndromes, where there is Yin within Yang and Yang within Yin, and diseases can transition from Yang to Yin and vice versa. Therefore, when conducting Eight Principles of Diagnosis, it is essential to not only master the characteristics of various syndromes but also to pay attention to their interrelations, transformations, mixtures, and the authenticity of symptoms to achieve a correct and comprehensive understanding and diagnosis of diseases.
1. Exterior and Interior
Exterior and Interior are two principles for distinguishing the location of the disease and the depth of its severity. It is a relative concept; for instance, when comparing the body shell and the internal organs, the body shell is considered Exterior, while the internal organs are considered Interior; when comparing the organs and bowels, the bowels belong to the Exterior, and the organs belong to the Interior; when comparing the meridians and internal organs, the meridians belong to the Exterior, and the internal organs belong to the Interior. The three Yang meridians are considered Exterior, while the three Yin meridians are considered Interior. From the perspective of disease depth, in cases of external pathogens, the pathogenic factors penetrate one layer into the Interior, indicating a deeper disease; conversely, when they exit the Exterior, it indicates a lighter disease. This relative understanding is particularly important for differentiating the six meridians in febrile diseases and the differentiation of Wei, Qi, Ying, and Blood in warm diseases. In a narrow sense, Exterior refers to the skin, hair, and meridians, while Interior refers to the internal organs and bone marrow. Diseases affecting the Exterior are classified as Exterior syndromes, while those affecting the Interior are classified as Interior syndromes.
Differentiating between Exterior and Interior syndromes is applicable to external pathogenic diseases, and its significance lies in understanding the severity and depth of the disease and the trend of pathological changes. Exterior syndromes are shallow and light, while Interior syndromes are deep and severe. When Exterior pathogens enter the Interior, it indicates disease progression, while when Interior pathogens emerge from the Exterior, it indicates disease regression. Understanding the severity and progression of the disease allows for mastery of the evolution of the disease, providing an active role in treatment, and serves as the basis for employing methods such as releasing the Exterior and attacking the Interior.
1. Exterior Syndromes
Exterior syndromes refer to the symptoms that arise when the six excess pathogenic factors invade through the skin and hair, or through the mouth and nose. The Complete Book of Jingyue states: “Exterior syndromes are those where pathogenic factors enter from the outside; all wind, cold, heat, dampness, fire, and dryness, as well as any improper Qi, are included.” Exterior syndromes are often seen in the early stages of external pathogenic diseases, characterized by a rapid onset and a short course of illness.
[Clinical Manifestations]: Fever and chills (or aversion to wind), pain in the head and body, thin white tongue coating, and floating pulse. Accompanying symptoms may include nasal congestion, runny nose, itchy throat, cough, etc.
[Syndrome Analysis]: The six excess pathogenic factors invade the skin and muscle surface, obstructing the normal dispersal of Wei Qi, leading to heat. When Wei Qi is obstructed, it loses its function of “warming the flesh and nourishing the skin”, resulting in symptoms of aversion to wind and cold. The pathogenic factors stagnate in the meridians, causing obstruction of Qi and blood flow, leading to pain in the head and body. Since the pathogenic factors have not yet entered the Interior, the tongue appearance shows no significant changes, presenting a thin white coating. When external pathogens invade the surface, the righteous Qi rises to resist the pathogens, hence the pulse is floating. The lungs govern the skin and hair, and the nose is the orifice of the lungs; when pathogenic factors enter through the skin and mouth, they correspond to the lungs, leading to symptoms such as nasal congestion, runny nose, itchy throat, cough, and even wheezing.
2. Interior Syndromes
Interior syndromes refer to a category of syndromes where the disease penetrates deeply into the Interior (organs, Qi and blood, bone marrow). It is contrasted with Exterior syndromes. Interior syndromes are often seen in the middle and later stages of external pathogenic diseases or in cases of internal injury. The causes of Interior syndromes can generally be categorized into three situations: first, when external pathogens are not resolved and penetrate into the Interior, invading the organs; second, when external pathogens directly invade the organs; third, when emotional distress, dietary indiscretion, or overexertion directly damage the organs, leading to dysfunction and chaotic Qi and blood.
[Clinical Manifestations]:Interior syndromes have complex causes, broad disease locations, and diverse symptoms, as detailed in the sections on differentiating Cold and Heat, Deficiency and Excess, and organ differentiation. Here are a few examples:High fever, irritability, delirium, thirst, abdominal pain, constipation or diarrhea, vomiting, short and red urine, yellow or thick greasy tongue coating, and deep pulse.
[Syndrome Analysis]: When heat pathogens penetrate into the Interior, or when Cold pathogens transform into Heat in the Interior, the heat becomes intense, leading to high fever; heat pathogens injure body fluids, causing thirst and short red urine; heat disturbs the mind, leading to irritability and delirium. If Cold pathogens directly invade the organs or if Cold dampness directly attacks the spleen and stomach, Cold pathogens stagnate in the middle burner, leading to abdominal pain; if Cold dampness obstructs the spleen and stomach, the spleen and stomach lose their ability to transform and transport, leading to diarrhea; if the stomach loses its harmony and descent, vomiting occurs, with yellow or thick greasy tongue coating and deep pulse indicating internal disease.
Appendix: Half Exterior Half Interior Syndromes
When external pathogens penetrate from the surface into the Interior but have not yet fully entered, or when Interior pathogens emerge from the surface but have not yet reached the surface, and the pathogenic factors and righteous Qi are in conflict between the Exterior and Interior, this is termed half Exterior half Interior syndrome. The symptoms include alternating chills and fever, fullness in the chest and hypochondria, irritability with a preference for vomiting, disinterest in food and drink, bitter mouth and dry throat, dizziness, and wiry pulse. (See the section on Shaoyang disease in the differentiation of the six meridians for details.)
3. Key Points for Differentiating Between Exterior and Interior Syndromes
The differentiation between Exterior and Interior syndromes primarily involves examining the changes in temperature, tongue appearance, pulse, and other factors. The Heart of Medicine states: “The differentiation of Exterior and Interior in a disease is entirely based on fever and tidal heat, aversion to cold and aversion to heat, headache and abdominal pain, nasal congestion and dry mouth, the presence or absence of tongue coating, and the floating or deep pulse. If there is fever and aversion to cold, headache and nasal congestion, with no tongue coating (or a thin white coating), and a floating pulse, this indicates Exterior syndrome; if there is tidal heat and aversion to heat, abdominal pain and dry mouth, with yellow-black tongue coating and a deep pulse, this indicates Interior syndrome.” Generally speaking, in external pathogenic diseases, the simultaneous presence of fever and aversion to cold indicates Exterior syndrome; however, if there is fever without aversion to cold or aversion to cold without fever, this indicates Interior syndrome. Exterior syndromes show little change in tongue coating, while Interior syndromes often show significant changes; a floating pulse indicates Exterior syndrome, while a deep pulse indicates Interior syndrome.
4. The Relationship Between Exterior and Interior Syndromes
The body’s surface and internal organs are interconnected through the meridians, allowing for communication between the Exterior and Interior. During the progression of a disease, under certain conditions, mixed Exterior and Interior syndromes may occur, and transformations between them may take place. For instance, simultaneous Exterior and Interior diseases, where Exterior pathogens enter the Interior, or Interior pathogens emerge from the Exterior, etc.
(1) Simultaneous Exterior and Interior Diseases
When Exterior and Interior syndromes appear at the same time, it is referred to as simultaneous Exterior and Interior diseases. This situation arises not only when the initial disease presents both Exterior and Interior syndromes but also often occurs when the Exterior syndrome has not resolved and has affected the Interior; or when the original disease has not healed and has been compounded by an external pathogen, such as having an internal injury and then being affected by an external pathogen, or initially having an external pathogen and then injuring the body through diet. The appearance of simultaneous Exterior and Interior diseases is often associated with the mutual presence of Cold and Heat, Deficiency and Excess, commonly seen as Exterior Cold with Interior Heat, Exterior Heat with Interior Cold, Exterior Deficiency with Interior Excess, and Exterior Excess with Interior Deficiency, etc. (See the section on differentiating Cold and Heat, Deficiency and Excess for details.)
(2) Exterior and Interior Interactions
a. Exterior Pathogens Entering the Interior: When a disease presents as an Exterior syndrome, if the Exterior pathogens are not resolved and penetrate into the Interior, this is termed Exterior pathogens entering the Interior. This often occurs due to a decrease in the body’s ability to resist pathogens, excessive pathogenic factors, improper care, or misdiagnosis and mistreatment. For example, in cases of Exterior syndromes with aversion to cold and fever, if the aversion to cold resolves but the patient no longer feels cold and instead feels hot, accompanied by thirst, red tongue with yellow coating, and red urine, this indicates the symptoms of Exterior pathogens entering the Interior.
b. Interior Pathogens Emerging from the Exterior: In certain Interior syndromes, when the pathogenic factors penetrate from the Interior to the Exterior, this is termed Interior pathogens emerging from the Exterior. This often occurs due to appropriate treatment and care, enhancing the body’s ability to resist pathogens. For example, internal heat causing irritability, cough, and chest tightness may subsequently lead to fever and sweating, or the appearance of rashes or spots, indicating that the pathogenic factors have reached the surface from the Interior.
Exterior pathogens entering the Interior indicate a worsening of the disease, while Interior pathogens emerging from the Exterior reflect a reduction in pathogenic factors, indicating a decrease in disease severity. Understanding the changes in the interactions between Exterior and Interior is of great significance for predicting the development and outcome of the disease.
Editor: Yang Wenjie, Physician Email: [email protected]