Yin and Yang
Yin and yang are the two most fundamental concepts in Chinese medical philosophy. These opposing concepts, rooted in ancient Chinese philosophy, are used to account for changes in the universe in a comprehensive manner.
In anatomy, the human body is divided into yin and yang as follows: the internal region is considered yin, while the external region is considered yang; the five viscera are yin, while the six bowels are yang; and the tendons and bones are yin, while the skin is yang. In physiology, yin represents the storage of energy, while yang represents human activities, as yin is said to stay within like a traditional housewife, while yang stays in the superficial region to guard against foreign invasion.
In pathology, yin and yang are used to describe two basic patterns of change. When yin prevails, yang will be diseased; when yang prevails, yin will be diseased. When yang prevails, there will be fever; when yin prevails, there will be chill. When yang is deficient, it will cause chill sensations in the superficial region; when yin is deficient, there will be internal heat. In diagnosis, yin and yang symptoms are used to describe the nature of a disease.
According to The Yellow Emperor's Classics of Internal Medicine, "a good physician who has mastered the technique of diagnosis will examine the patient's color and take their pulse, and they will classify all symptoms into yin and yang as the first step in making a diagnosis."
In terms of treatment, striking a balance between yin and yang is the most fundamental principle of clinical practice. Among the treatments based on this principle are sedating the excess and toning up the deficiency. The Yellow Emperor's Classics of Internal Medicine states, "A hot disease should be treated by cold herbs; a cold disease should be treated by hot herbs... Yin should be treated in a yang disease, yang should be treated in a yin disease."