Lixue zhengzong 理學正宗 "The core of the doctrine of the universal principle" is a summary of Neo-Confucian teachings compiled during the early Qing period 清 (1644-1911) by Dou Keqin 竇克勤 (1653-1708), courtesy name Minxiu 敏修, style Jing'an 敬庵, from Zhecheng 柘城, Henan. He was examining editor of the Hanlin Academy (Hanlinyuan jiantao 翰林院檢討) and wrote several books on philosophy, like Xiaojing zhayi 孝經閘義 of the "Classic of Filial Piety", Shigui yongyan 事規庸言, Biyang xue tiaogui 泌陽學條規 or the family instructions Xunletang jiagui 尋樂堂家規.
His book of 15 juan length is a collection of 15 brief biographies of Neo-Confucian philosophers from the Song 宋 (960-1279) to the Ming period 明 (1368-1644), with short notes on their most important contributions to the philosophical debate, and comments by Dou himself.
The text is found in Dou's collected works Dou Jing'an Xiansheng yishu 竇靜庵先生遺書.