Concept
Xu Dachun (; 1693–1771), courtesy name Xu Lingtai (), also known as Xu Daye (), was a Chinese writer and physician active during the Qing dynasty. Despite having no formal education, he was a celebrated medical authority who authored numerous medical treatises, four of which were fully preserved in the Siku quanshu. Xu spent most of his life in Jiangsu but he died in Beijing. Xu was born in 1693 in Wujiang, Jiangsu. His grandfather, Xu Qiu (徐釚; 1636–1708), was a noted artist, historian, and poet, while his father, Xu Yanghao (徐養浩; died 1721), was an hydraulic engineer. At the time of Xu's birth, the family's financial situation had taken a turn for the worse. In lieu of a formal education, Xu acquired much knowledge on irrigation from his father. He also taught himself how to read and write, with an emphasis on medicine and philosophy, although he was also interested in astronomy, martial arts, and music. Described as "a man of tall stature with a wide forehead and a resonant voice", Xu received much acclaim as a physician. He authored commentaries on Chinese medical classics including the Nan jing, the Shennong bencao jing, and the Shanghan lun. In 1757, he published Yixue yuanliu lun (醫學源流論; literally Treatise on the Origin and Development of Medicine). Outside of medicine, Xu also wrote lengthy treatises on irrigation, Taoist philosophy, and zaju (a form of Chinese opera). Xu robustly defended the practice of medicine, arguing that "humans occupy the most important position on earth, and the fate of humans on earth depends on medicine." However, he conceded that medicine had its limitations—any suggestion that it could help one achieve immortality was "nonsense". He also observed that not all diseases require treating: "I believe that there are some people who, when they get sick, recover spontaneously without treatment, others who struggle to recover without medical intervention, and yet others who cannot recover without medical help and will die.