The following is an extract from the beginning of the book ‘A Study of Qi’, in which Elisabeth Rochat gives a short introduction to the development of the concept of qi from its early appearance as ‘wind’ in the oracle bones, to through to its key position in Han dynasty cosmology:

In order to understand the origin of qi, we must first look at the concept of wind. A character for qi itself does not appear in the early oracular and bronze inscriptions, or in the most ancient Chinese texts, such as The Book of Documents, Shujing, or The Book of Odes, Shijing. What we do find in the very ancient oracular inscriptions of the twelfth, thirteenth and even fourteenth centuries BC is the character for wind, and these early descriptions of wind have some of the qualities which will be later attributed to qi.

There are several different kinds of wind, for example the four winds and the eight winds, and each of these contributes to the growing concept of qi. In the beginning qi appears as something coming from heaven and penetrating earth. It has an influence on earth and provokes a reaction, as for instance with the qi that makes cold and heat, day and night, wind and rain.

Later qi will be understood as what is behind yin yang (陰 陽) and this is a very important shift. We cannot speak of qi without speaking of yin yang, and we cannot speak of yin yang without speaking of qi. For instance, yin and yang appear in early texts as two of the six qi of heaven. They are like cold and heat, which is to say they are not only the bright, sunny side of a hill, but also the shady side. More than that they are the cold and heat which are the result of being in the sun or shade. Yin and yang will become a kind of differentiation of qi, as qi will become the influence behind any kind of manifestation. Yin qi will become the principle behind cold and cooling and yang qi will be the principle behind heat and warming.

We can see these differences evolving, and this development will be linked with changes in the weather and the passing of time, which is seen as a movement of qi and yin yang, with cooling from summer to winter and warming from winter to summer. So here qi is being used to codify the movement of time, and that movement is seen not only in the four seasons but also seen in the progress of each day. Many of the texts  describe all this.

As the understanding of qi evolves into what is behind the appearance of things, there is the development of what we may call analogy. For instance, the same kind of qi making wind and tempests in nature is also seen to make anger. Therefore in early texts there is a relationship between the six qi of heaven and the six qualities of qi within a human being. These texts show the development of qi not only outside in nature, but also inside a human being. An example of this is seen in the Zhuangzi, where qi is seen not only as that which lies behind any given phenomenon, but also as the link between different phenomena presenting similar characteristics. For instance, what is behind anger and wind may also be behind all kinds of violent impulses at the beginning of something; a rising up movement, like the sunrise, or springtime.

Through this linking process we have the possibility of developing a cosmology based on qi, yin yang and the five elements. The concept of the five elements or agents, (wu xing 五 行), developed around the third century BC. It was not possible to develop a cosmology of correspondences before having a substantial enough notion of qi to make these links, which occurred around the fourth and third centuries BC.