In ancient China, “qi” was the highest philosophical category and is essential for grasping the fundamental questions of ontology as they were understood in ancient China.

Qi is a fundamental concept in Chinese philosophy, medicine and indeed the cultural tradition of the whole nation. The concept of qi ties together the traditional Chinese medical system and Chinese philosophy. Although the term qi originated long, long ago and has contained multiple meanings throughout the centuries, it is important to find the commonality among all of these in order to see its profound influence on Chinese medicine. Therefore, we will start our discussion with this vital concept.

Qi is a syncretic concept that contains multiple levels of meaning.

In the oracle-bone inscriptions “qi” has several meanings which are only peripherally related to its present meaning. In the Shang Dynasty （16 ^th century -11 ^th century B.C.） the ancestor of the modern character for “qi” occurred in references to praying for rain or for the avoidance of disasters, issues of utmost concern in an agricultural society. In the process of the ceremony people inevitably had perceptual intuition for “wind” and “cloud”, and tried to know their connection with “rain”. Rituals involving praying for rain or asking about its timing were intimately related to quasi-supernatural notions of “wind” and “clouds”. “Qi” was originally a product of these experiences of early peoples in ritual life.

In ancient China all philosophical schools attempted to illustrate and explain the growth and change of all things on earth and in human life with qi.

It is important to note that cosmology is roughly equivalent to ontology but does not include the entire set of concepts related to the existence and functioning of nature. This involves fundamental questions of epistemology.

In ancient China there was “qi monism” but there was no natural science system. Why? Cosmology and the conception of nature were not completely overlapping concepts in ancient Chinese thought. The “universe” was not considered equivalent to mere “nature”.

In the theory of “unity of the heaven and humanity”, the universe contained morality itself, and conceptually speaking it was impossible to separate “the conception of nature” from “objective nature”. “Qi” was actually a barrier to this separation because “qi” never left its ancient roots in animism and mystery. Ancient Chinese viewed qi as a type of very refined, but spiritual substance. However, the concept of qi was essential in the evolution from a universe ruled by gods to a universe composed of qi that followed regular patterns.

Since qi also contains non-material elements, it is not equal to materialistic monism. This is why we cannot find a modern concept to replace it. This multivalent term contains elements that do not fit into a modern, materialistic worldview.

To summarize, the Qin and Han dynasties （221 B.C.-220 A.D.） were a period when philosophers probed into the relations between the heaven and man. Using the category of “qi”, they adopted a classification method based on “like attracts like”, and gradually expanded the scope of “qi”. Since the viewpoint of “separation between the heaven and man” was antithetical to the concept of qi, an objective view of nature and its laws did not develop. Since human society and the natural world could not be separated, it became a significant obstacle to the development of science. Therefore the “binary body and spirit” became a key problem that had to be grappled with in traditional Chinese medicine.

The doctrine of “qi” reached its climax in the Han Dynasty （206 B.C.-220 A.D.）. “Essential qi” and “original qi” answered the question of how humans and all things on earth came into being. At that time, qi was also introduced into the theoretical system of traditional Chinese medicine, giving people a powerful concept to understand the essence of life, the occurrence and course of disease, and the relation between humans and the external environment. The connotation of “qi” includes some special characteristics of Chinese philosophy and cultural traditions as follows:

— “Qi” is the primary explanation for the source of life in the universe. Qi, as the most refined substance in the universe containing both material and non-material elements has never been overcome in the intellectual history of China.

— “Qi”, as a conception of nature （objective）, has some similarities to the conception of nature in Western philosophy. Both view specific substances as the basis for the formation of the natural world, such as water or atoms. But qi also has its own unique features. “Qi” is shapeless, impenetrable, and non-transformative. Its shapelessness may result in “indistinctiveness” in understanding of the nature of things. The material and the spiritual are conflated, making it difficult for a system of natural science to take hold.

— “Qi” and “atomism” share some common features because “qi” and “atoms”both carry a “substance” that initiates from a source and provides the basis for the union of original qi and essence, and life and disease. The growth and continuance of individual life depends on “qi”. In the theoretical system of traditional Chinese medicine, the zang-fu or internal organs are also based on the relationship between substance and spirit, and the concepts of “shapelessness”, “impenetrability” and distinctiveness. These features define the concept of the body structure in ancient times.

— “Qi” as a conception of nature has its limitations. Existence of any material thing depends on the dialectical unity between variability and stability. But when we say “qi” has the ability to create all things on earth, we find that variability is overly emphasized and structural stability is neglected. Qi indicates everything is changing and transforming, so no matter what we attribute this to, idealistic or materialistic, nature is surely only to be felt, but not expressed. The methodology behind this philosophy privileges mental analysis over stability and structure.

The philosophical category of “qi” was formed in the Spring and Autumn and Warring States Periods （770-221 B.C.）. “Qi” is the basis of the Chinese medical theory contained in The Yellow Emperor’s Inner Classic.

”Qi,” in The Yellow Emperor’s Inner Classic, is used to explain the following key questions:

— “Qi” is the source of life and has its essential nature.

— ”Qi” represents the functional activities of the body. In traditional Chinese medicine qi is both substance and function. For example, it includes the functions of yang qi, defensive qi, the qi and functions of the five zang-organs, the qi and functions of the six fu-organs, as well as the qi and functions of the acupuncture channels.

— “Qi transformation” is used to explain the harmonious activity of the body and “qi dynamic” is used to explain the motion and various mechanisms of qi, both of which are considered the most important traits of traditional Chinese medical theory.

· Qi transformation provides an explanation for disease causation and disease dynamics. “All diseases are the result of disorders of qi” aptly summarizes the fundamental understanding of disease causation and disease dynamics.

· The concept of qi transformation also elucidates the mechanism of action behind various modalities of treatment. Regulation of qi activity is the underlying treatment principle, since all diseases are caused by disturbed qi activity. That’s why regulation of the qi activity and smooth circulation of qi and blood are the first priority in treatment.

· Qi transformation guides the prescription of medicinals and is pivotal in making a prognosis. The four properties and five flavors of medicinal herbs, which guide the prescription of herbs, reflect a direct application of qi in medicine. The condition of channel qi, zang-fu qi and yin-yang qi is the basis for prognosis.

· Qi transformation is the underlying premise of the theory of the five circuit and six atmospheric influences, which explains how all things on earth function.

Afer publication of The Classic of Difculties （ Nàn Jīng, 难经） no other new theories about “qi” emerged.

In the late Ming Dynasty （1368-1644 A.D.） the theory of “epidemic pathogenic factors” was put forward by Wu You-ke based on the “six excesses causing diseases”. He thought that the epidemic pathogenic factors were a kind of “evil qi” causing epidemic diseases. He insisted on the viewpoint that there are two important factors in relation to the infection of epidemic diseases. One is the state of strong healthy qi and the other is the strength of epidemic evil qi.

We can now see that the concept of “qi” has played a pivotal role in traditional science in China, and that a primitive “qi monism” is the basis of The Yellow Emperor’sInner Classic and the traditional Chinese medical system. Here, we would like to make a summary of the theory of “qi”:

— It expands the scope of ideas and phenomena that can be incorporated into the traditional Chinese medical system. It provides a basis for the connection between the human body and the environment.

— It gives us a framework for interpreting the mechanisms of diagnosis and treatment, human physiology and pathology.