This Chapter from the Yellow Emperor's Classic of Internal Medicine explores the principles of Traditional Chinese Medicine, focusing on the balance of yin and yang. It details how imbalances in qi, the vital energy, manifest as physical and dream-related symptoms, emphasizing the importance of accurate diagnosis through pulse and other physical examinations. The text stresses the necessity of understanding the interplay between yin and yang, the five zang-organs, and the seasonal cycles to achieve a proper diagnosis and treatment. Failure to adhere to these principles results in ineffective treatment and the propagation of medical errors. The ultimate goal is to restore harmony and balance within the body to promote health and longevity.