This Chapter from the Yellow Emperor's Classic of Internal Medicine details a traditional Chinese medicine theory of disease diagnosis and treatment. It explains the concepts of primary (本, běn) and secondary (标, biāo) disease manifestations, and how acupuncture techniques should be applied according to these principles, including aligning (cóng) and opposing (nì) methods. The text also describes the progression of diseases affecting various organs, their characteristic symptoms, and prognoses, ultimately outlining when acupuncture is and is not an appropriate treatment. The underlying principle emphasizes understanding the interplay of Yin and Yang to achieve effective treatment.