The foundation principles of Chinese medicine are not necessarily uniform, and are based on several schools of thought. Received TCM can be shown to be influenced by Taoism, Buddhism, and Neo-Confucianism.
Since 1200 BC, Chinese academics of various schools have focused on the observable natural laws of the universe and their implications for the practical characterisation of humanity's place in the universe. In the I Ching and other Chinese literary and philosophical classics, Chinese writers described general principles and their applications to health and healing.
Porkert, a Western medical doctor, placed Chinese medical theory in context as:
Chinese medicine, like many other Chinese sciences, defines data on the basis of the inductive and synthetic mode of cognition. Inductivity corresponds to a logical link between two effective positions existing at the same time in different places in space. (Conversely, causality is the logical link between two effective positions given at different times at the same place in space.) In other words, effects based on positions that are separate in space yet simultaneous in time are mutually inductive and thus are called inductive effects. In Western science prior to the development of electrodynamics and nuclear physics (which are founded essentially on inductivity), the inductive nexus was limited to subordinate uses in protosciences such as astrology. Now Western man, as a consequence of two thousand years of intellectual tradition, persists in the habit of making causal connections first and inductive links, if at all, only as an afterthought. This habit must still be considered the biggest obstacle to an adequate appreciation of Chinese science in general and Chinese medicine in particular. Given such different cognitive bases, many of the apparent similarities between traditional Chinese and European science which attract the attention of positivists turn out to be spurious.
The Shen Nong's Herbal Classic, a 2000-year old medicinal Chinese book considered today as the oldest book on oriental herbal medicine, classifies 365 species of roots, grass, woods, furs, animals and stones into three categories of herbal medicine:
The first category, called "superior", includes herbs effective for multiple diseases and are mostly responsible for maintaining and restoring the body balance. They have almost no unfavorable side-effects.
The second category comprises tonics and boosters, for which their consumption must not be prolonged.
The third category must be taken, usually in small doses, and for the treatment of specific ailments only.
Lingzhi ranked number one of the superior medicines, and was therefore the most exalted medicine in ancient times.The ancient Chinese use of mushrooms for medicine, has inspired modern day research into medicinal mushrooms like shiitake, Agaricus blazei, Trametes versicolor, the table mushroom and of course lingzhi. Highly purified compounds isolated from medicinal mushrooms like lentinan (isolated from Shiitake), and Polysaccharide-K, (isolated from Trametes versicolor), have become incorporated into the health care system of countries such as Japan.The compounds are used to stimulate the immune system and promote health.
Traditional Chinese medicine is largely based on the philosophical concept that the human body is a small universe with a set of complete and sophisticated interconnected systems, and that those systems usually work in balance to maintain the healthy function of the human body. The balance of yin and yang is considered with respect to qi ("breath", "life force", or "spiritual energy"), blood, jing ("kidney essence", including "semen"), other bodily fluids, the Wu Xing, emotions, and the soul or spirit (shen). TCM has a unique model of the body, notably concerned with the meridian system. Unlike the Western anatomical model which divides the physical body into parts, the Chinese model is more concerned with function. Thus, the TCM spleen is not a specific piece of flesh, but an aspect of function related to transformation and transportation within the body, and of the mental functions of thinking and studying.
There are significant regional and philosophical differences between practitioners and schools which in turn can lead to differences in practice and theory.
Theories invoked to describe the human body in TCM include:
Channels, also known as "meridians"
Wu Xing
Qi
Three jiaos also known as the Triple Burner, the Triple Warmer or the Triple Energiser
Yin and Yang
Zang and Fu
The Yin/Yang and five element theories may be applied to a variety of systems other than the human body, whereas Zang Fu theory, meridian theory and three-jiao (Triple warmer) theories are more specific.
There are also separate models that apply to specific pathological influences, such as the Four stages theory of the progression of warm diseases, the Six levels theory of the penetration of cold diseases, and the Eight principles system of disease classification.