Yin and Yang - The Underlying Logic of Traditional Chinese Medicine

Legend has it that when Zhang Zhongjing was writing this epoch-making medical classic, he faced a complex historical background and academic environment. To make this work more widely understood and applied by later generations of physicians, he adopted a rather wise approach: he significantly reduced some of the prevalent content involving metaphysics and numerology.

A notable example is the Five Elements theory. The Five Elements theory holds an important position in the Traditional Chinese Medicine system, using the five basic substances of wood, fire, earth, metal, and water, along with their relationships of generation, restriction, overacting, and counteracting, to explain human physiological functions and pathological changes. However, what is remarkable is that even those who lack understanding of the Five Elements theory can comprehend and apply many of the principles, formulas, and medicinals in the Treatise on Cold Damage and Miscellaneous Diseases. This is because, although its theoretical basis is closely related to the overall framework of Traditional Chinese Medicine, Zhang Zhongjing, in the book, did not overly rely on obscure Five Elements terminology for explanation in the specific descriptions of symptoms and disease mechanisms, nor in the application of formulas. Instead, he focused on the direct description of clinical symptoms and pathogenesis.

However, among the many discarded metaphysical and numerological theories, Zhang Zhongjing did not remove the concept of Yin and Yang from the Treatise on Cold Damage and Miscellaneous Diseases, because the Yin and Yang theory is the soul of Traditional Chinese Medicine, the most fundamental logical framework that runs through the entire medical system. It highly summarizes the contradictory attributes and relationships of various phenomena in nature and within the human body.

For Traditional Chinese Medicine, whether it is the functional activities of the organs, the circulation of Qi and Blood, the occurrence and development of diseases, or the properties and meridian tropism of drugs, all can be analyzed and explained using the theory of Yin and Yang. If this most fundamental theoretical logic of Yin and Yang were removed, the diagnostic system of Traditional Chinese Medicine would lose its core guiding principle, and many pathological phenomena and treatment principles would become difficult to understand and express.

What exactly is ‘Yin and Yang’? This concept, which holds a central position in Traditional Chinese Medicine theory, may seem somewhat abstract at first. However, to put it simply, Yin and Yang is actually a practical problem-solving tool. It’s not just a profound theoretical framework, but also an effective method to help us understand and deal with the complexities of the real world.

When we face a problem that needs to be solved, whether it’s a trivial matter in life or a major decision, the first thing we often do is to establish a clear goal. Once the goal is set, the dichotomy of Yin and Yang can play its unique role, guiding our thinking to find a path to achieve that goal.

To understand this more clearly, we can draw on a real-life example, such as my decision on whether to move to Shanghai for development. In this decision-making process, we can categorize all relevant factors into the two categories of ‘Yang’ and ‘Yin’. Let’s define it this way: anything that is beneficial to me and can help me achieve my development goals is classified as ‘Yang’; conversely, those aspects that may hinder me or bring adverse effects are classified as ‘Yin’.

Thus, when I seriously consider the option of moving to Shanghai, the ‘Yang’ list might include: a higher income level, a broader perspective, more career development opportunities, and so on. These are factors that can actively promote personal growth. The ‘Yin’ list might include: a higher cost of living, more intense competitive pressure, and so on. These are aspects that may bring challenges or discomfort.

By clearly listing the pros and cons in this way, we can more intuitively compare the balance of power between ‘Yang’ and ‘Yin’. In the context of the example, if, after careful consideration, we find that the quantity and importance of ‘Yang’ (benefits) far outweigh those of ‘Yin’ (drawbacks), then making the decision to move to Shanghai seems more rational. This process of breaking down complex problems into binary opposites and analyzing their balance is a manifestation of Yin-Yang thinking in real life. In Traditional Chinese Medicine, this logic is often used to help think about how to solve patients’ problems.

Therefore, whether facing a crossroads in life or exploring the mysteries of health, this practical thinking tool of Yin and Yang dichotomy can help us clarify our thoughts, grasp the key to the problem, and ultimately find a solution. It transcends the purely theoretical level and becomes a wisdom that guides us in understanding the world and solving problems.

Of course, the concept of Yin and Yang is not only the cornerstone of Traditional Chinese Medicine but also an important foundation upon which many ancient Chinese arts of divination – such as divination by lot, Feng Shui, and destiny analysis – were built and applied. It can be said that the theory of Yin and Yang is a key to understanding these numerological systems.

The emergence of the Yin and Yang concept is rooted in the most direct and profound observations of the natural world by ancient people. The alternation of the sun and moon brought the cycle of light and darkness; the coming and going of cold and heat formed the changes of the four seasons. These cyclical natural phenomena, and the ancient people’s understanding of their influence on all things in the world, gradually gave rise to the idea of ‘when Yin reaches its extreme, Yang is born; when Yang reaches its extreme, Yin is born.’ This is a simple yet profound philosophical insight, revealing the internal driving force and laws of the development and change of things.

The Book of Changes says, ‘One Yin and one Yang is called the Dao.’ Here, ‘Dao’ can be understood as the fundamental law governing the operation and change of all things in the universe. The character ‘之’ (zhī) implies change and transition, emphasizing that Yin and Yang are not two static states but are constantly interacting and transforming into each other.

The most representative symbol is the Taiji diagram (Tai Chi symbol). This simple yet profound design visually demonstrates the connotation of Yin and Yang. Typically, the white part on the left of the Taiji diagram symbolizes Yang, representing attributes such as active, upward, outward, bright, and movement; while the black part on the right represents Yin, symbolizing attributes such as passive, downward, inward, dark, and stillness. More ingeniously, the Taiji diagram respectively embeds a small dot of the opposite color, commonly known as the ‘Yin-Yang eyes.’ These two small dots profoundly reveal the philosophy that ‘there is Yin within Yang, and Yang within Yin,’ illustrating that nothing can exist in a purely Yang or purely Yin state. Yin and Yang are mutually permeated and interdependent. As the ancients said, ‘Isolated Yang does not generate, isolated Yin does not grow,’ emphasizing the mutual dependence and restriction of Yin and Yang. Only when Yin and Yang coexist harmoniously can all things grow and develop.

The circular outer frame of the Taiji diagram vividly expresses the ceaseless rotation and the mutually opposing yet complementary nature of Yin and Yang. It is not just a simple pattern but a fundamental philosophy revealing the origin of the generation and change of all things. The transformation between Yin and Yang is not simply a matter of one waxing while the other wanes, but a mutual transformation and dynamic balance of energy. Yang can transform into Yin, and Yin can also transform into Yang. This transformation is the driving force behind the continuous generation of all things in the universe.

Therefore, whether exploring the mysteries of nature or attempting to predict the trajectory of life, the theory of Yin and Yang provides a basic analytical framework and cognitive perspective. It tells us to view things from the perspective of the unity of opposites and to recognize the dynamic changes and interdependent relationships within things. This is why the concept of Yin and Yang has fundamental and guiding significance in many fields, including the arts of divination.

The opposition of Yin and Yang is the primary characteristic of the Yin-Yang theory, revealing the universal contradictory relationships that exist within the universe and the human body. Simply put, the opposite of Yin is Yang, and the opposite of Yang is Yin. This opposition is reflected in many aspects of nature and is also widely applied in Traditional Chinese Medicine theory to generalize various mutually opposing attributes.

For example, observing nature, we see the opposition of cold and heat, and the alternation of day and night. In the human body, there is the distinction between the exterior and the interior, the excitation and inhibition of functions, and the difference in gender – males tend to have more Yang characteristics, while females tend to have more Yin characteristics. These seemingly different things and attributes can all be divided and understood using the concepts of Yin and Yang. Cold is Yin, then heat is Yang; the exterior is Yang (relatively speaking), then the interior is Yin; male belongs to Yang, then female belongs to Yin.

The opposition of Yin and Yang is not a simple absolute separation but rather two mutually contradictory aspects within a unified entity. It is precisely the existence of this opposition that constitutes the internal driving force for the movement and change of things. Recognizing the Yin-Yang attributes of things is the foundation for grasping their characteristics and laws.

The interdependence of Yin and Yang, also known as their mutual utilization or mutual sustenance, profoundly reveals the relationship of mutual dependence and mutual use between the two aspects. This interdependence is mainly manifested in two aspects:

Firstly, Yin and Yang are mutually dependent; neither can exist without the other as a prerequisite for its own existence. Without daytime, we cannot recognize what nighttime is; without nighttime, there would be no concept of daytime. Similarly, in the human body, substance belongs to Yin, and function belongs to Yang. Substance is the carrier of functional activities, while functional activities manifest the vitality of substance. The two are mutually dependent and inseparable.

Secondly, the existence of Yin and Yang serves to mutually complement and confirm each other’s characteristics. Yang is recognized as Yang precisely through its contrast with Yin. The active, outward nature of Yang is more clearly manifested in comparison with the passive, inward nature of Yin. Conversely, the value of Yin’s existence is also reflected in its mutual contrast with Yang.

Therefore, by distinguishing and discussing the opposition of the Yin-Yang attributes of things, we can more deeply understand the thought process of their mutual dependence and mutual confirmation. This interdependent relationship makes Yin and Yang not isolated existences but a connected whole.

The waxing and waning of Yin and Yang refers to the fact that the two aspects are not in a static, unchanging state, but rather change dynamically, exhibiting a pattern of one increasing as the other decreases. When the power of one side weakens, the power of the other side inevitably strengthens accordingly; conversely, when the power of one side strengthens, the power of the other side will weaken accordingly.

This waxing and waning change is the normal state of the development and change of things. Taking the changes of the four seasons as an example, in summer, Yang Qi gradually flourishes while Yin Qi gradually declines, and when it reaches its peak, Yang reaches its extreme and Yin is born. In winter, Yin Qi gradually flourishes while Yang Qi gradually declines, and when it reaches its extreme, Yin reaches its extreme and Yang is born. The Yin and Yang within the human body are also in a constant state of waxing and waning, maintaining a dynamic balance. The occurrence of disease is often due to this waxing and waning of Yin and Yang losing its normal rhythm, leading to an excessive predominance or decline of one side.

Understanding the law of the waxing and waning of Yin and Yang helps us grasp the trends in the development of things and the process of disease evolution, thereby taking corresponding measures for regulation.

The transformation of Yin and Yang refers to the fact that the two aspects can transform into each other under certain conditions. This transformation does not occur arbitrarily but requires specific conditions as a prerequisite. When the development of a thing reaches a certain stage, and the balance of Yin and Yang forces within it reaches a certain critical point, a change in nature may occur.

For example, extreme heat can generate cold, and prolonged cold can transform into heat. This is a manifestation of Yang transforming into Yin, and Yin transforming into Yang. In the process of disease evolution, some diseases initially manifest as heat patterns (Yang patterns), but if they persist without healing, they may transform into deficiency-cold patterns (Yin patterns). Similarly, some deficiency-cold patterns may also transform into Yang patterns with appropriate treatment.

The mutual transformation of Yin and Yang reflects the dialectical nature of the development and change of things, suggesting that when we understand and deal with problems, we should not only stay at the superficial judgment of Yin-Yang attributes but also pay attention to their internal transformation trends, so as to more accurately grasp the essence and development direction of things.

To deeply understand the mysteries of Yin and Yang, one must first grasp their inherent essence. The essence of Yang lies in ‘movement,’ which is an active, initiative, and ceaseless state. The external manifestation of this ‘movement’ is often expansive, like sunlight spreading energy in all directions, like growing plants stretching their branches and leaves outward. This ‘movement’ can evolve into heat, which is a manifestation of energy, representing activity and ascendance. Spatially, Yang is often associated with an upward trend, like a flame burning upwards. In terms of nature, Yang often exhibits the characteristic of hardness, symbolizing strength and resilience.

Based on this, we can further associate and expand on the representative things and attributes of Yang. Yang often represents positive, active forces; corresponds to the masculine vigor of men; symbolizes the vast and boundless sky; points to the outside, the exposed aspects of things; is like a luminous object, radiating light and vitality; is located in a relatively high position; and all things and phenomena with characteristics such as positive upwardness, initiative, outwardness, and functional hyperactivity can be categorized as belonging to the realm of Yang.

Opposite to Yang, the essence of Yin is ‘stillness,’ which is a relative, inward-preserving, and composed state. Different from the expansiveness of Yang, the manifestation of Yin is introverted, like the quiet stillness of the earth, with energy accumulating inward. This ‘stillness’ can evolve into cold, which is a manifestation of relatively insufficient energy, representing contraction and descending. Spatially, Yin is often associated with a downward trend, like water flowing downwards. In terms of nature, Yin often exhibits the characteristic of softness, symbolizing inclusiveness and nourishment.

Similarly, we can expand our understanding of Yin. Yin often represents negative, relatively passive forces (not absolutely bad); corresponds to the gentle beauty of women; symbolizes the earth that carries all things; points to the inside, the inherent aspects of things; is like an object that absorbs light, containing energy; is located in a relatively low position; and all things and phenomena with characteristics such as quiet composure, inward contraction, and relatively reduced function can be categorized as belonging to the realm of Yin.

A crucial understanding is that Yin and Yang always appear in pairs, which constitutes a fundamental characteristic of the Yin-Yang theory. Isolated Yang or isolated Yin does not exist; they must be mutually dependent and compared with each other to manifest their meaning, just as there is no darkness without light, and no stillness without movement.

Therefore, when we use Yin-Yang thinking for expansive imagination, the key is to grasp its core essence – movement and stillness – and the characteristics that extend from them, such as expansion and contraction, heat and cold, upwardness and downwardness, hardness and softness. By grasping these essences, we can more accurately understand and apply the theory of Yin and Yang to analyze and understand the complex world.

Within the vast realm of Traditional Chinese Medicine, despite the various schools of thought and diverse treatment methods, all TCM practitioners share the same fundamental goal: to assist the human body in restoring its normal physiological state.

When a person becomes ill, TCM does not simply view it as the invasion of some external factor but understands it as a process of mutual resistance between the body’s own resistance (what TCM calls ‘Zheng Qi’ or upright Qi) and external pathogenic factors (‘Xie Qi’ or external evil). This invisible ‘battle’ unfolds within the body, and the task of TCM is to discern the state of this battle, judging whether the upright Qi has a slight advantage or the external evil is stronger, so as to adopt corresponding strategies to help the body.

So, from the perspective of TCM, how does one distinguish the strength comparison between upright Qi and external evil, and how does one assist the body in overcoming illness? One of the key tools is the dichotomy of Yin and Yang that we have been discussing.

In clinical practice, we often hear the terms ‘Yang pattern’ and ‘Yin pattern.’ When we determine that a patient leans towards a ‘Yang pattern,’ it usually means that in this process of struggle between upright Qi and external evil, the patient’s own upright Qi is relatively stronger than the invading external evil. At this time, the body often exhibits some ‘hyperactive’ states, that is, the body’s functional reactions exceed the normal range, such as fever, pain, flushed face, irritability, and other symptoms. These all belong to the category of ‘Yang,’ which are ‘heat signs’ or ‘excess signs’ produced by the intense struggle between the body’s upright Qi and external evil.

Conversely, if a patient is diagnosed as leaning towards a ‘Yin pattern,’ it often suggests that the patient’s upright Qi is relatively insufficient, and the body’s functions are in a state of ‘decline and weakness,’ that is, the body’s functional activities are reduced, and vitality is insufficient. Such patients often exhibit symptoms such as mental fatigue, listlessness, drowsiness, and aversion to cold. These all belong to the category of ‘Yin,’ which are ‘cold signs’ or ‘deficiency signs’ manifested by insufficient body function and slow response.

Therefore, TCM precisely uses the analysis of the Yin-Yang attributes of various clinical manifestations of the patient to judge the nature of the disease and the comparison of the strength of upright Qi and external evil, thereby providing direction for subsequent treatment.

Master Ni emphasized that changes in body temperature often contain information about Yin-Yang imbalance.

Warm palms, cool back of hands and forehead: This phenomenon usually indicates that the condition is developing in a positive direction. It may suggest that the outward-dispersing Yang Qi is beginning to become contained, and the body’s Yin and Yang Qi are gradually moving towards coordination and balance.

Breast cancer area feels hot, surrounding area cool: This localized high temperature suggests an excess of Yang heat in that area. The patient will clearly feel the lesion as hot, but this is different from a systemic fever. Master Ni explained that this may be due to local ‘Yin excess’ (such as a lump) obstructing the normal inward flow of Yang Qi, causing Yang Qi to stagnate locally and forming a pathological state of ‘Yang not entering Yin’.

The manifestations of disease are varied, but within the framework of Yin and Yang, they can be fundamentally categorized:

Yang patterns: These typically manifest as hyperfunction and overreaction, such as fever, pain, and irritability. The ‘hot’ feeling when touching a localized area of breast cancer is one manifestation of a Yang pattern.

Yin patterns: These typically manifest as hypofunction and underreaction, such as mental fatigue, aversion to cold, and weakness.

The effectiveness of treatment can also be observed through changes in Yin and Yang:

Breast cancer area feels hotter after medication: This may suggest that the treatment has not effectively opened up the local ‘Yin excess,’ and Yang Qi still cannot flow inward smoothly, indicating that the condition may not have improved.

The heat subsides a bit after medication: This is often a positive sign, suggesting that the treatment is starting to take effect, and the Yin-Yang imbalance in the body is gradually being corrected.

Master Ni believed that through the traditional TCM diagnostic methods of observation, listening & smelling, and inquiry, a wealth of information regarding a patient’s Yin-Yang imbalance can also be obtained:

Observation : Observing the patient’s complexion, form, demeanor, and movements, such as mental state and physical activity, indirectly reflects the Yin-Yang balance within the body.

Listening & Smelling : Listening to the patient’s voice, breathing, etc. A loud or weak voice, and rapid or slow breathing, are often related to the flourishing or decline of Yang Qi.

Inquiry : Asking the patient in detail about their symptoms and feelings. The patient’s descriptions often directly or indirectly point to the Yin-Yang imbalance in the body. For example, palpitations may relate to the Yin and Yang of the heart, and abdominal throbbing may be related to the imbalance of Yin and Yang in the lower Jiao. Abnormalities in daily physiological activities such as bowel movements and sleep are even more important manifestations of Yin-Yang imbalance.

When seeing patients, Master Ni emphasized that practitioners need to maintain a state of ’emptiness in the middle for clarity,’ not being prejudiced by Western medical diagnoses. Instead, they should start with the patient’s basic physiological state and grasp the patient’s overall Yin-Yang state through detailed questioning, thereby conducting pattern identification and treatment more accurately.

Beyond career and relationships, Yin-Yang thinking can also be applied to many aspects of life. For example:

Health and Wellness: The ‘movement’ of exercise is Yang, the ‘stillness’ of rest is Yin; the two need to be balanced to maintain physical health. In diet, foods with cooling properties are Yin, and foods with warming properties are Yang; they need to be harmonized according to one’s constitution.

Interpersonal Interactions: Associating with positive and optimistic people is Yang, bringing positive energy; being with negative and complaining people is Yin, which may drain our energy. We can consciously move closer to ‘Yang’ and away from ‘Yin.’

Learning and Growth: Actively learning is Yang, introspective thinking is Yin; the combination of the two allows for more effective self-improvement.

In conclusion, the Yin-Yang dichotomy is a simple yet practical thinking tool. It reminds us to view things from the perspective of the unity of opposites, seeing both the positive and recognizing the potential negative aspects, so as to make more informed judgments and choices.