This is part of a series of lectures on Qin Bowei's 56 methods. This lecture discusses the source, causes, mechanism, locations, disease manifestations, and presenting symptoms providing a broad picture of Phlegm. Additionally, the associated treatment principles are discussed. The lecture covers key diagnostic criteria for each principle, the associated flagship formula for each, how to modify it, as well as how it relates to classical Chinese medicine. The end of the lecture goes over numerous case studies to demonstrate how each is used in real life.