The five phases, an important philosophical concept related to the natural world and our understanding of it, were used by the ancient Chinese to classify all things on earth and their relationship to human life. It was based on their understanding of the attributes of the world and provided a classification principle that could be used to verify the idea of “unity of the heavens and humanity”.

In terms of extant sources, the term “fve phases” was frst recorded in the Book ofHistory （ Shàng Shū, 尚书） and is a symbolic system based on a synthesis of multiple concepts, customs and cultural notions. The fve phases are wood, fre, earth, metal and water. Each of these phases symbolizes a particular patern of motion and a set of functional characteristics. The fve phases were also applied to the realm of society and political afairs by Zou Yan and Dong Zhong-shu.

Knowledge of the five phases originated from ancient people’s study of astronomical phenomena, and originally referred to the movement of the “five stars”. They were also associated with the development of agriculture and metallurgical techniques. The concept of the five phases appeared even earlier than the concept of yin and yang.

Each has its own particular set of qualities, for example, water tends to flow downward, fire is characterized by blazing, wood characterized by bending and straightening, metal by change and transformation, and earth by sowing and reaping.

Although there are no exact historical data about the earliest content and form of the five phases, there are many references to using “five” as a means of categorization, particularly in records on primitive religions and beliefs.

The incorporation of the theory of the five phases into traditional Chinese medicine has its historical significance, but its limitations cannot be ignored. When the abstract concept of the five phases was applied to the theory of organ manifestations, it led to an emphasis on qi transformation, function and mutual relations, but overlooked morphologic observations. Abandonment of anatomy was the outcome of the development of the theory of the five phases and five zang-organs.

The Yellow Emperor’s Inner Classic itself is not only a great classic in which the theory of the five phases and medical knowledge are combined, but also represents the culmination of the historical process that led to the fusion of the two. In comparison with yin and yang, it is very difficult to have intuitive knowledge of the five phases. Only when the attributes of the five phases and their similarities to the zang-fu organs were accounted for, could medical reasoning move towards analogical processing and become the foundation of zang-fu physiology and pathology. Here “attributes” plays a significant role. In the process of analogical reasoning, when you “get the real meaning and forget the image” ^[2], then it becomes possible to incorporate the concept completely.

In the historical process of the formation of the concept of the five phases, their pairing and correspondence to the zang-fu organs was key. Through abstract analysis, the philosophy and the scientific theory of a particular subject can merge together into an integral whole. This “higher integration” is also essential for understanding why Chinese medicine is characterized by “virtual reality and working hypotheses”. So, in a sense, gain is loss. Dialectics shows us that nothing is absolute, and clinical practice leads us to embrace bidirectional thinking.