Li Gong 李塨 (1659-1733), courtesy name Gangzhu 剛主, style Shugu 恕穀, was a philosopher of the early Qing period 清 (1644-1911), and founder of the so-called Yan-Li School (Yan-Li xuepai 顏李學派). He hailed from Lixian 蠡縣, Hebei, and was a disciple of Yan Yuan 顔元 (1635-1704), and so adapted Yan's proposition of a "practical science" (shixue 實學). With the age of 32 sui he graduated the state examination but instead of taking an office, he traveled around and visited numerous scholars throughout the empire, with which he discussed philosophy, lectured, and learned medicine. As an old man, with 60 sui, he finally was appointed educational instructor (xuezheng 學正) of Tongzhou 通州, but after only one month he returned home to care for his ailing mother.
The philosopher Li Gong was one of the early modern scholars doubting the traditional teachings of the Neo-Confucians. Li Gong was of the opinion that the "universal principle" (li 理) and matter or substance (qi 氣) were inseparable. While the Neo-Confucians had believed, that the principle existed before matter and as a separate entity, modern Confucians stressed that the principle was embedded in the objects (li zai shi zhong 理在事中). All things had, Li Gong said, a conditional principle and a chronological principle (tiao li ri li 條理日理), in other words, the principle was subject to circumstances. Without substance, a "principle" made no sense.
Li Gong was an ardent teacher of practical knowledge. Reading about history will not necessarily result in success in daily politics. It was therefore necessary to learn practice (xi xing 習行), something the Song 宋 (960-1279) and Ming 明 (1368-1644) period Neo-Confucians had not done, and therefore experienced the end of their dynasties. While the Neo-Confucians had advocated "reaching the voidness (i.e. the universal principle itself) and safeguarding quietness" (zhi xu shou ji 致虛守寂), Li Gong underlined the importance of practice as "real knowledge" (zhen zhi 真知). Learning and studying was, nonetheless, also important. Knowledge preceeded action, and was the master of action (xue sheng xing, xue xian xing 學勝行，學先行). This assumption differs somewhat of Yan Yuan's propositions who had tought that on the one hand learning preceeds knowledge, and knowledge action, but that practice was more important than pure theoretical knowledge.
In the field of politics, Li Gong advocated a just distribution of land to the peasants, in order to secure that a sufficient amount of grain was produced for all.
Li Gong himself was also interested in philological research of the ancient Confucian Classics and wrote numerous commentaries, like Zhouyi zhuanzhu 周易傳注, Shijing zhuanzhu 詩經傳注, Chunqiu zhuanzhu 春秋傳注, Lunyu zhuanzhu 論語傳注, Daxue zhuanzhu 大學傳注, Zhongyong zhuanzhu 中庸傳注, Zhuanzhu wen 傳注問, Zhongyong jiangyu 中庸講語, Xiaoxue xiye 小學稽業, Daxue bianye 大學辨業 and Shengjing xuegui zuan 聖經學規纂. During his many travels to southern China he visited the scholars Mao Qiling 毛奇齡, Wang Fuli 王複禮, Yan Ruoqu 閻若璩, Wan Sitong 萬斯同 and Hu Wei 胡渭, representatives of the philogical school of Han Studies (Hanxue 漢學) or Studies of the Classics (jingxue 經學).
Li Gong also wrote a theory of teaching, the Lunxue 論學, and the book Pingshu ding 平書訂. His collected writings are the book Shugu houji 恕穀後集.