The theories of Yin/Yang, and the Five Elements, developed around the fourth century BC and are often called the theories of systematic correspondences. This is because of their unique contribution to the idea that the universe, as well as the body, consists of dynamic and functional interrelations. It attempts to explain the universe as forces or principles instead of the whims of gods, ancestors or demons. Along with the five-element theory of nature, this helped to create an important link in the development of Chinese science and medical theory. The I Ching (The Book of Changes) is a book about the constant flux and permanence of this process in the universe. The character “Jing” means “great book”, and the character “I” is derived from an abstract pictorial representation of the sun and the moon in combination, which signifies Yang and Yin respectively.


Originally, Yang and Yin represented the sunny and shady sides of a mountain. Chinese science later developed this principle to stand for polar opposites of interrelated phenomena. Yang represents the functional energetic qualities of the universe, while Yin represents the structural and substantive qualities of the universe. This has been explained in the following way: “In modern terms, yang corresponds to all that is active, expansive, centrifugal, aggressive, demanding, (polar) negative, and yin implies all that is structural, substantive, contractive, centripetal, responsive, conservative, (polar) positive”. These interrelated phenomena are expressed in terms of correspondences between qualities of any identifiable object. One cannot exist without the other. For example, the concept of up cannot exist without the idea of down, nor the concept of fast without the corresponding idea of slow.

Change, or “I”, in the universe is a dynamic interaction between Yin/Yang, in which the constant interplay of these basic forces creates, and is created by, the universe of which we are all part. “The universe is in movement or transformation at every moment. Life itself is a process of never-ending change from birth to death…The I Ching is an attempt to find reliable rules for nature and human life about changes in the universe.” The I Ching forms the basis for all Chinese science and is a fundamental part of Chinese cultural expression. In medicine, the theory of Yin/Yang is the organizing principle in the correlation of all medical information (for example, the differentiation of syndromes and pulse qualities), and combines

with other important theories like the Five Transformative Phases and Channel theories. So, in essence, “The Yin/Yang doctrine is simple but its influence has been very extensive. No aspect of Chinese civilization – metaphysics, medicine, government, or art – has escaped its imprint.” There were two schools of Yin/Yang theorists. The main difference between them was whether to divide the natural unfolding of change into four or six divisions.


Another vitally important philosophical and empirical contribution to Chinese science incorporated extensively within medical theory was the principle of Wuxing – the “Five Transformative Phases” or elements. In ancient times in China, it was thought that the universe consisted of five transformative phases or natures. Tzu-Szu (492-431 BC) was said to have advanced this theory, later redeveloped by Mencius. The world was viewed as a constant interaction and combination of the five transformative phases.

The five basic transformative phases are Wood, Fire, Earth, Metal and Water. This theory was an attempt to classify the basic properties of material things in the process of change. Each transformative phase has a particular nature and a predictable interaction and relationship with each other. Originally, the Yin/Yang theorists and Five Element theorists disagreed profoundly about the nature of change, but the concepts were later resolved and are now combined. So integrated is the Wuxing with Yin/Yang that they may now be considered different elements of a unified concept. “We are aware that Wuxing theory originated from and cannot be separated from Yin/Yang theory, so we can conclude that Wuxing is Yin/Yang, and Yin/Yang is Tao.”

In interaction, elements may clash, balance or nurture the others, depending on their inherent nature as well as their relative strength. The movement of Nature is a constant interplay of the natural assertions, adjustments or adaptations of these basic primal forces through the seasons. In this way, Nature archives a harmonious but vigorous balance. In the theory of Yin/Yang, as well as with the Five Elements, “The outlook is dynamic and not static. And the end is an ordered Nature rather than chaos. In point of process, there is contradiction as well as harmony, and in reality, there is unity multiplicity.”

The elements foster balance and harmony, with each other. When each transformative phase plays its natural part, all things function smoothly. Each specific transformative phase functions to keep another transformative phase imbalance with the whole, and is in turn balanced by yet another. The ancient empirical philosophers observed that the transformative phases also had specific functional relationships in the natural cycle of Nature. Just as seasons change from one to the next, the various transformative phases of Nature change or “give birth” to the others. All of Nature, including human social and political activity and changes, is explained by these transformative phases and their various corresponding natures.

It was in this light that the human body was seen as a part of Nature. The Wuxing was developed to represent these basic natural principles and forces. Within the body, there are “physiological” transformative phases and energies that reflect the basic forces of life.

There are tissues and organ functions that resemble each of the transformative phases both physically and energetically, and reflect the same basic interrelationships of Nature. There is a “physiological” equivalent to the actions of Wood, Fire, Earth, Metal and Water functioning within the body. For example, Wood is related to the organs of the Liver/Gallbladder, Fire is related to the Heart/Small Intestine, Earth is related to the Spleen/Stomach, Metal is related to the Lung/Large Intestine, and Water is related to the Kidney/Bladder. Each element nourishes another and they depend upon each other for their growth and support.

As the five transformative phases/elements nourish each other, so do the organ systems. As it is in Nature, so it is in the organ system. For example, the Water or the Kidney/Bladder system supports growth; the Earth or the Stomach/Spleen system can dam the Water/Kidney/Bladder, controlling the natural or physiological excess of water. As one transformative phase or physiological system nurtures or controls another, balance is achieved.