After he made an intensive study on Shanghan Lun (Treaties on Cold Damages) Mr. Zheng Qing'an realized that the theoretical essence of the qi transformation of six channels lies in the unity of yin and yang, and the coordination between restoring of yang qi and preservation of fluids. He also pointed out the complicated syndromes not only represent the ever changing transformation of manifestation and roots, but also embodies the unity between man and nature. Zheng developed the academic thought in Shanghan Lun, that is to treat three yin syndromes with restoring of yang qi, and became the guru of Huoshen (fire).