Rising and falling, bright and dark, up and down, moving and static, cold and heat are opposites. This opposite opposition leads to a mutually restrictive relationship. If the rising force is restrained by the falling force, then the falling force is also restrained by the rising force. Other opposites also have this kind of mutual restriction relationship. Without restriction, the balance of Yin and Yang will also be lost.
(b) the relationship between mutual roots and interoperability
Yin and Yin do not exist alone without each other. It doesn't matter if there is no top, and it doesn't matter if there is no Yin. Both sides take the opposite as the condition of existence. This relationship is called "mutual root of Yin and Yang".
Yin-yang theory also holds that Yin-yang is an interactive relationship. This problem can be explained by the interaction between yin essence and yang spirit of human body. Yin essence represents the material basis or energy of the human body, while Yang spirit represents the functional activities of the human body. The functional activities of human body need yin essence as the energy basis, so it can be considered that yang is born of yin essence; As a result of human functional activities, new energy sources, namely yin essence, will be continuously generated and manufactured, so it can also be said that yin essence is generated by yang. Another example is the change of the length of day and night in a year. From winter to summer, the days are getting longer and longer, which can be regarded as the increase of sunshine day by day; The summer solstice is the longest day and the most prosperous day for the sun. From this day on, the night becomes longer and longer. It can be considered that the yin is increasing day by day until the winter solstice, so there are sayings that "winter is a sun born" and "summer is a yin born". This is also a concrete manifestation of Yang being born in Yin and Yin being born in Yang.
(C) the relationship between the growth and decline of Yin and Yang
The opposing forces of Yin and Yang are not always equal, but often in a quantitative fluctuation, and the change of the length of day and night in the last year is the best explanation. From the solstice of winter to the solstice of summer, the days are prolonged and the nights are shortened day by day, which means that the yang is increasing and the yin is disappearing; From the solstice of summer to the solstice of winter, the night gets longer and the day gets shorter, which means that the yin grows longer and the yang disappears. This kind of growth and decline maintains a certain "limit" within a certain range and maintains a relatively balanced state. The root cause of this situation is the opposition of Yin and Yang and their mutual utilization. However, if the growth and decline of Yin and Yang exceed a certain "limit", and a certain aspect is too long or excessively dissipated, one side of Yin and Yang will rise and fall. Losing the balance of yin and yang will lead to human diseases and natural disasters.
(D) Yin-Yang transformation
If the rise and fall of Yin and Yang is a process of quantitative change of Yin and Yang, then the transformation of Yin and Yang is a process of qualitative change. Yang Can can be transformed into Yin, and Yin can be transformed into Yang. The transformation of yin and yang takes place at the stage when the ups and downs of yin and yang reach "extreme" or "extreme", that is, the so-called "extreme must be reversed". "On Su Wen's Six Meanings" said: "The birth of things depends on transformation, and the extreme of things depends on change", which just illustrates this truth.
The climate of the four seasons in nature changes from cold to warm, and from hot to cool, which is a gradual process of yin-yang transformation, while "extremely cold produces heat" and "extremely hot produces cold" in the process of disease development is a sudden process of yin-yang transformation.