Qi, also known as Chi, is an important part of Traditional Chinese Medicine theory. Usually associated with that magical, mystical, indescribable and immeasurable force that separates Traditional Chinese Medicine from the rational approach of science and BioMedicine, in TCM ”Qi” is also used to describe the functioning of the organ systems & the refined essences that the organs and body produce.
This is the Chinese character for Qi. The bottom left part of the symbol means (uncooked) “rice”. The upper part of the symbol means “steam”, or “gas” or “vapour”. When taken as a whole, this character represents a range of states of matter and energy, from the dense and material (rice) to the sparse and immaterial (steam). Every phenomenon in the universe can be considered to be a form of Qi, differing only in the degree to which its matter is condensed, the energy it contains, and how it is manifested.
In modern science, this is the continuum between matter and energy, a concept central to modern physics. Water, for example, can be densely packed with less movement of individual molecules (ice), and it can also be loosely packed with more movement of individual molecules (vapour). The liquid form of water is a state of matter and energy which lies somewhere between ice and vapour.
Atoms (such as hydrogen & oxygen) and molecules (such as water) are simply different manifestations of matter and energy. They differ only in the number and arrangement of protons, electrons, and neutrons which compose them, and how they bond to each other.
Wave-particle duality in chemistry and physics further illustrates this point. In some situations, light behaves similar to particles (matter). In other situations, light acts more like waves (energy). This is Qi; sometimes it manifests as matter, sometimes it manifests as energy.
The Qi of the internal organs in Chinese Medicine is really two things. It is the functional activity of an organ system. The Heart beats. The Lungs breathe. The Stomach digests food. The Bladder holds and excretes waste liquid.
It is also a refined essence produced by the organs, which nourish the body and the mind. For example, the functional activity of digestion (energy) extracts the most important aspects of the food (matter) which goes on to nourish our muscles, blood, brain, etc…
Those who choose not to “believe” in Chinese Medicine often cite the mysteriousness of Qi as their main reason. This implies only that which can be measured and analyzed within the Cartesian paradigm is “real”.
The Chinese Medicine concept of the circulation and cultivation of Qi in the body refers in part to the circulation of arterial blood, venous blood, lymphatic fluid, extra-cellular fluid, hormones, and neurotransmitters. It includes the functioning of the central nervous system, the peripheral nervous system, the autonomic nervous system, all of the internal organs, and the synergism of voluntary muscles. But it also includes that as-yet-undocumented energy, the one which martial artists and acupuncturists have been conscious of for millenia.