Basic category of TCM theory——qi(essential qi) in Inner Canon of Huangdi

Qi was a basic concept of material existence in Chinese ancient philosophy.Qi was the flowing and microscopic existence in pre-qin dynasty,which was different from liquid and solid.Qi was the important conception of the flowing and microscopic existence in Inner Canon of Huangdi,which constructed the medical theory and explained the nature,human body,physiology and pathology.Thus,it made the TCM theory belong to materialistic epistemology.Qi explained the existence of life material which could not be cognized at that time,this made TCM theory do not need to study what material was,but to study what the changes of material were,then promoted the progress of medical science.