 He is best known in the West for his discourse on the relationship between the names and actualities, preserved in his treatise "Zhonglun" (中論).Born in Ju County, Beihai Commandery (east of present-day Lechang, Shandong), Xu Gan developed a reputation for good memory and diligent studies as a youth.Around 189, Xu Gan left his residence in Linzi and went into hiding on the Jiaodong peninsula.