This Chapter is a dialogue from the Yellow Emperor's Classic of Internal Medicine, exploring the physiological basis of health, illness, and courage. The Yellow Emperor and Shao Yu discuss how susceptibility to illness varies based on skin, muscle, and complexion, attributing differences in responses to weather and pain to physical constitution rather than solely bravery or cowardice. Shao Yu explains that courage stems from a well-organized internal structure and strong organs, while cowardice results from imbalances and weakness. Finally, they examine how alcohol can temporarily mask cowardice.