Dao and TCM
Traditional Chinese Medicine (TCM) is a system of healing based upon the Chinese philosophy of the correspondence between Nature and human beings.This belief of Nature-Human sycnhronication 天人合一 is that there is an universal natural law, 道 Tao/ Dao, that doctrine all the creation and function of the universe (the macro system), including the human beings (the mirco system). When human respects and follows the natural law, we are in balance and stay healthy.
Despite the fundamental role of Taoist thinking played in the development of Chinese medical theories, little emphasis has been placed on the study of Taoism in most modern Chinese medicine training programs. A large part of the reason is that Taosim is very closely related to the Taoist religion and sometimes regarded as superstition or sometimes people just think that philosophy is useless. Even though the study of philosophy does not directly tell us the WHAT- like what medicine or food to take, what exercise to practice, philosophy indeed gives is a much deeper and fundamental meaning of WHY. The WHAT are like the branches of a tree, only the WHY is the root and orgin of life. Answering the question WHY, most often then not, give us a better understanding and sense of well being in our lives therefore waste less time and energy on unrelated matter.
What does Taosim teach us?
Dao De Jing(Tao Te Jing 道德經) is the essential scripture of Taoist, also known as Lao Zi (Lao Tzu 老子). It was poetic and full of philosophical insights. Comprising a total of 81 chapters, with approximately 5000 words, it was also the earliest philosophical workpiece in Chinese history. The passage from the book is simple and yet full of insights and dialectic. As the masterpiece of Taoism, discussion topics can be found within Tao Te Jing including the origins of the Universe due to changes, the appropriate way of country administration, as well as life and death. 
The Harmony Between of Yin and Yang
In the opinion of Taoism, everything in the universe can be found in the harmonious state, which consists of binary opposition and restriction, and yet it also can be the sequential root cause of each other. Yin and Yang are not merely about Qi; they are the common attribution in everything. 
“The created universe carries the yin at its back and the yang in front; through the union of pervading principles it reaches harmony.” - Tao Te Jing Chapter 42.
Nature is the way (Tao)
“Tao works in the principle of nature” is an essential concept in Taoism.
“Man is ruled by Earth. Earth is ruled by Heaven. Heaven is ruled by the Way. The Way is ruled by nature itself”. - Tao Te Jing, Chapter 25.
The Great Four are related through the modeling of the lower hierarchy after the higher hierarchy, from the Man the lowest hierarchy toward Tao the highest hierarchy. This reveals the objective recognition of the nature of everything in the universe; everything should be existing in the form “just as it is.” Consequently, every existence is harmonious to each other, as Liu pointed out, “the natural existence is a state without competition and struggling.”
“Natural simplisticity” was derived from the concept “works in the principle of nature.”
“Let them(mankind) enjoy their food, beautify their clothing, Be satisfied with their homes, delight in their customs.- Tao Te Jing, Chapter 80.
The Unity between the Universe and Man
The concept of “the Unity between the Universe and Man” is a very classical concept in Chinese traditional. Taoism is actively promoting this concept in discussing the relations between the Man and the Universe.
“The Tao produced One; One produced Two; Two produced Three; Three produced All things.” - Tao Te Jing, Chapter 42
The Way (Dao/ Tao) is a formless state of spirits, the most primitive form of existence, and being thus produced “One” and also the start just like the big bang. Following that, “One produced Two”, the binary state of mutual influencing of Yin and Yang like the Sky is the opposite to the Earth, the light is opposite of the darkness. From interaction and dynamic of all these binary energies, the three is born. The three mentioned here is referring to everything, every creatures, including mankind. Man, as well as everything, is the product of the Yin and Yang, the Universe, and we are all bound to the same principle of the nature.
Way of balance
Preserving equivalence, maintaining balance, is another essence in Taoism.
“It is the way of Heaven to take away from those that have too much and give to those that have not enough.
Not so with man's way: He takes from those that have not and gives it as a tribute to those that have too much.
Who can have enough and to spare to give to the entire world? Only the man of Tao.” - Tao Te Jing, Chapter 77.
The verse “take away from those have too much, and give to those that have not enough” implies the importance of the social impartiality and the balance in ecosystem; meanwhile, the verse “takes from those that have not, and gives it to those that have too much” is human behavior in common that leads to devastating due to imbalance or being unjust. In essence, the way of Tao, its principle, is to maintain and preserve the balance, which can be applied in the effort of the perseverance of the ecosystem. Taoism avoids both extreme cases which are overpossessing and underpossessing. 
A Take-home point about Taoism and TCM
Taoism is the foundation for the theory of TCM. The Harmonious of Yin and Yang explained that Yin and Yang as the root of the Universe, as a pair of opposition yet mutual influencing, and hence achieving the state of harmony. The Way models to Nature and this reveals the meaning of simplicity and the principle of no excessive effort in health care. The Unity between the Universe and Man emphasizes the synchronization between humankind and the natural environment around. Man is inseparable from nature and hence required to act according to the law of Nature. The way of balance stresses the perseverance of equilibrium state as the therapy methodology to avoid the extreme case of overpossessing and underpossessing.
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