Yin and yang may seem like a difficult concept, but it is also quite intuitive. While it is impossible to define yin and yang in a single phrase, when you are provided with several examples of what is considered yin or yang, the concept becomes easier to grasp.
Yin ⇠⇢ Yang
Darkness ⇠⇢ Light
Moon ⇠⇢ Sun
Feminine ⇠⇢ Masculine
Softness ⇠⇢ Hardness
Cold ⇠⇢ Heat
Night ⇠⇢ Day
Rest ⇠⇢ Activity
Introspection ⇠⇢ Extraversion
Water ⇠⇢ Fire
Passive ⇠⇢ Active
However, the application of yin and yang in traditional Chinese medicine (TCM) is not so simple. I have been teaching for over 10 years, and it can be quite challenging for some students who grew in western culture. Many students tend to understand yin and yang in a dichotomous manner. Some textbooks even claim that yin and yang are exclusive, which is a basic misunderstanding. Sometimes, I ask my students: Is the moon yin or yang? Is the hand yin or yang? The students confidently happens to answer that the moon is yin, and the hand is yang. However, when we compare the moon to a dimly shining star nearby or the hand to the forehead, the concept of yin and yang becomes less clear. Yin and yang cannot be explained without a point of comparison, and without a standard compare by. Therefore, we should not remove arrows from above yin and yang list. We can say moon is yin only compared to sun, but we cannot say moon is just yin.
This is why people in East Asian cultures, who are rooted in Chinese characters, use one common characters '間' in words like "human(人間)," "time(時間)," and "space(空間)." '間' means 'between A and B', so human, time and space are all conceived by relation among them. However, viewing yin and yang dichotomously leads to dichotomous interpretations of medicine and diagnosis. When a patient comes in, they are quickly categorized as having cold or heat, deficiency or excess, and medicines are prescribed accordingly, which can lead to contradictions and false rationalizations. It makes Yin and Yang very hard to be applied to real patients.
Let me ask a simple question: An 80-year-old thin grandfather enters the clinic wearing thick clothes even though it's spring. He is limping, and his ankle is swollen, red, and hot from a fall. Is he Yin or Yang? Is his illness Yin or Yang? It's already getting complicated, right?
Therefore, when prescribing medicine, it is important to consider the priority and weight of whether to treat the Yin or the Yang first. The branch symptoms can be treated first, followed by the root symptoms. Contrary to popular belief, many medicines like Ban Xia Xie Xing Tan, Er Shen Tang, and Ba Wei Di Huang Tang contain both Yin and Yang in one prescription. Students who understand Yin and Yang dichotomously cannot utilize these prescriptions, leading to more confusion.
Beside common opposing relationship between Yin and Yang, there are mysterious aspects of yin and yang. When you understand these, you can apply yin and yang, in treatment of patients and yourself.
First, although Yin and Yang are opposites, they are not exclusive. Do you see the two bulls fighting above? If one wins, the other dies; this is exclusivity. In this perspective, Patients cannot be both Yin and Yang, nor can they be both hot and cold. So when they see a medicine like Ban Xia Xie Xin Tang, they feel uneasy. Since both Huanglian and Ginseng are used together, is it a cold or a hot medicine? However, Yin and Yang are not exclusive. Instead, one cannot exist without the other. This kind of relationship is called a couple, generational, or complementary opposition. When explaining Yin and Yang, a sunny hillside and its shaded counterpart are often shown. If there is no sun on the sunny side, there is no shadow on the other side. This is a complementary relationship. Western science has made us uncomfortable with such ambiguity. Probably, Thomas Bulfinch confused when 'hope' was found with bad things together in Pandora's box. He says hope is a good thing, how it could coexist with bad things like war and famine. However, from the complementary perspective of yin and yang, it is inevitable that hope exists alongside war and famine. Without war and famine, there would be no hope. There is no reason to have hope if there is nothing bad.
Bulfinch's Mythology, Thomas Bulfinch (1796-1867)
Second, yin and yang can only be explained in terms of comparison. While the sun is yang, it becomes yin when compared to a brighter star in another solar system. Similarly, a person who is considered yang in Seoul might be considered yin among the Inuit people in Alaska. Thus, the appropriate treatment for the same individual might vary depending on the context. In the summer, a person who could gulp down beer in a glass filled with ice without any problems might suffer from diarrhea in the winter. Just like this, the medicine and treatment required for the same person are all determined relatively. If you look at the optical illusion below, A and B appear to be clearly different colors.
Is A yin and B yang? In reality, when measured quantitatively with a color picker in Photoshop, the two are exactly the same color. It's just an optical illusion. From a Western perspective, since A and B are the same, there is no yin and yang between them. However, from the perspective of yin and yang, A is clearly yin, and B is clearly yang. Therefore, it doesn't make sense to determine yin and yang by quantifying factors like pulse rate or the angle of the raised outer corner of the eye. We are trapped in the snare of quantification brought by modern science.
Third, yin and yang share the same origin and transform into each other. At any moment, what was yang can instantly become yin. Therefore, when treating a condition, one cannot simply categorize it as yin or yang, cold or hot, and proceed with treatment. Perhaps at the time when yang is most scarce, such as during midwinter or at the break of dawn, the emerging yang energy may be at its strongest. Just as a seed is in the yin (position) within the soil but possesses the most yang (energy). Diseases and people should be understood in this way as well.
These three aspects are all represented in the diagram of yin and yang. The symbol of yin and yang is a circle, divided into two halves. Yin and yang are constantly changing and transforming into each other in a dynamic, cyclical manner. At the pinnacle of yin or yang, it starts to change into the other, and they coexist at the same time. One half is black (representing yin) with a white dot, and the other half is white (representing yang) with a black dot. Yin and yang are not exclusive, so the black dot (yin) can be found inside the white wave (yang), and vice versa.
Students easily understand the left image as yin and yang when they first start learning. However, by the time they are about to graduate and become interns, they mistakenly view the right image as yin and yang. When they ask me if a disease or patient is yin or yang, hot or cold, I can only respond with:
"Based on what standard, compared to what, and in what context are you asking if something is yin or cold?"
Let's go back to the first question, how will you balance this patient in terms of Yin and Yang?
Let me ask a simple question: An 80-year-old thin grandfather enters the clinic wearing thick clothes even though it's spring. He is limping, and his ankle is swollen, red, and hot from a fall. Is he Yin or Yang? Is his illness Yin or Yang? It's already getting complicated, right?