Gu jingjie gouchen 古經解鉤沉 "Rediscovering lost ancient texts on the meaning of the Classics" is s collection of commentaries on the Confucian Classics compiled during the Qing period 清 (1644-1911) by Yu Xiaoke 余蕭客 (1732-1778), courtesy name Zhonglin 仲林, style Gunong 古農.
Yu hailed from Changzhou 長洲 (near modern Suzhou 蘇州, Jiangsu) and had learnt all about the Classics in his youth and began to note down his own thoughts and interpretations, which were, after all, often enough a match for those of the Confucian master Hui Dong 惠棟 (1697-1758). Yu Xiaoke therefore became the latter's disciple and was an important scholar of the so-called Han School of Confucians that investigated the ancient Han-period 漢 (206 BCE-220 CE) texts.
The governor-general of Zhili 直隸 (modern Hebei) invited Yu to participate in the compilation of the local gazetteer Jifu tongzhi 畿輔通志, but because of an eye disease, Yu returned to his home region, where he became a teacher. At that time he was a famous as Wang Yinglin 王應麟 (1223-1296) or Gu Yanwu 顧炎武 (1613-1682), but he died as a poor man. Apart from the Gu jingjie gouchen he wrote a phonetic commentary called Wenxuan yinyi 文選音義, the anthology Wenxuan zati 文選雜題, and the poetry collection Xuanyinlou shishi 選音樓詩拾.
The 30-juan long Gu jingjie gouchen is a collection of commentaries on the Confucian Classics from the Han to the Tang 唐 (618-907) period. It includes such on the Classics Yijing 易經 (Zhouyi 周易), Shangshu 尚書, Shijing 詩經 (Maoshi 毛詩), Zhouli 周禮, Yili 儀禮, Liji 禮記, Zuozhuan 左傳, Gongyangzhuan 公羊傳, Guliangzhuan 穀梁傳, Xiaojing 孝經, Lunyu 論語, Mengzi 孟子 and the gloss book Erya 爾雅.
For each commentary, the compiler provides biographic and bibliographic information, but quotes only from those texts that are not preserved as books but only in fragments used in other texts. He also mentions such texts whose author is not known or texts of which the book title is not known, but the author. The structure is very clear in first listing the classical text, and then the commentaries, each of them listed clearly and in an understandable sequence. The citations are given most complete, so that his book has a very high scholarly value. The text of the classics is based on a Northern Song-period 北宋 (960-1126) print, with support of a Ming-period 明 (1368-1644) edition to correct errors or to supplement missing words.
Yu Xiaoke worked for three years for his book, writing and reading day and night, so that his left eye was nearly blind when he finished the text in 1762. In spite of the high diligence with which Yu Xiaoke did do research, left out two important commentaries, namely Huang Kan's 皇侃 (488-545) Lunyu yishu 論語義疏 from the Liang period 梁 (502-557), and Shi Zheng's 史徵 Zhouyi koujue yi 周易口訣義 from the Tang period.
In the 18th century Huang Kan's book was lost in China and only preserved in a Japanese copy, and the book of Shi Zheng was only preserved in quotations in the encyclopaedia Yongle dadian 永樂大典, to which Yu Xiaoke did not have access.