The Formation of the Theory of Yin and Yang

According to the theory, Yin and yang exists in all things. At first, Yin meant a place not having exposure to the sun, and yang described a place that had exposure to the sun. Now, Yin and yang represent two components that oppose each other. Their interactions and plays against each other promote the occurrence, development, and transformation of things. They are used in reasoning things out while analyzing the things that occur in the world. It is believed, according to the Dao (the basic law in the natural world) that all things carry the two components of Yin and yang.

The theory of Yin and yang has an impact on the science of TCM, as it has promoted the development of the theoretical system of TCM.