Zhiyan 知言 "Words of Wisdom" is a Confucian treatise written by the Song-period 宋 (960-1279) scholar Hu Hong 胡宏 (1105-1161), courtesy name Renzhong 仁仲, who also wrote the book Huangwang daji 皇王大紀. The 6-juan long Zhiyan is a biji 筆記 "brush notes"-style essay on the question of teaching and learning. It was several times revised by the author before he published it. The title is derived from an expression in the Classic Mengzi 孟子, referring to the fact that a wise man understands whatever words he hears.
The Neo-Confucian master Lü Zuqian 呂祖謙 (1137-1181) praised Hu's book as superior to Zhang Zai's 張載 (1120-1177) Zhengmeng 正蒙, yet Hu Hong's teacher was his own father Hu Anguo 胡安國 (1074-1138) who was a disciple of the famous master Yang Shi 楊時 (1053-1135). Hu Hong was also influenced by the teachings of Su Shi 蘇軾 (1037-1101).
According to the philosophy of this particular Neo-Confucian school, Hu Hong did in his book not discern between "good human character" and "bad character", but said that the human mind generally contained a complete set of characters (xin yi cheng xing 心以成性). Yet the Heavenly order and human desires might be displayed in different ways in human actions and emotions. The innate disposition called "character" (xing 性) and its effects in daily life are called the "mind" (xin 心). The famous philosopher Zhu Xi 朱熹 (1130-1200) respected Hu Hong, but he had a very different opinion and heavily attacked Hu Hong, Lü Zuqian and their disciples (like Zhang Shi 張栻) in his essay Zhiyan yiyi 知言疑義.
A quite interesting aspect of the Zhiyan ist hat the author advocated the ancient well-field system (jingtianzhi 井田制), which plays no role in the discussions of other Neo-Confucians.
From the Yuan period 元 (1279-1368) on the Zhiyan was rarely in circulation, and Ming period 明 (1368-1644) prints were full of typesetting errors. Some editors even added names of chapters that were not part of the original text. Fortunately enough the Zhiyan is quoted in the Ming-period encyclopaedia Yongle dadian 永樂大典, and some Song-period prints have survived. It is therefore possible to reconstruct the texts in its full and original shape.
The Zhiyan is included in the imperial series Siku quanshu 四庫全書.