Yuzi 鬻子 "Master Yu" is a collection of various saying of a certain Master Yu Xiong 鬻熊 (dates not known) from the Zhou period 周 (11th cent.-221 BCE). The imperial bibliography Yiwenzhi 藝文志 in the official dynastic history Hanshu 漢書 speaks of 22 chapters, and the book Yilin 意林 from the Southern Dynasties period 南朝 (420~589) of 6 chapters, while the received version has 14 chapters. The commentary of the monk Jiangxing 逄行 from the Tang period 唐 (618-907) calls the book as a chaotic assortment of various statements which are only fragmentarily preserved. The books therefore never attracted the attention of scholars and is rarely studied. Some even doubted the authenticity of the surviving paragraphs, yet Song Liang 宋濂, a Ming period 明 (1368-1644) scholar, identified it as a veritable ancient text. The authorship is attributed to Yu Xiong who is said to have been a "teacher" of the first kings of the Zhou dynasty. He must thus have lived in the 11th century BCE. He might have originated in the southern state of Chu 楚 or among the Miao tribes 苗.
The philosophy of the book Yuzi is mainly Daoist, regarding the universe and all creations within it as subject to ever-lasting change, living and dying being connected in a permanent cycle of reproduction. The bibliography in the Hanshu therefore lists it among the Daoist books. If Daoist thought stood really in the center of the book, can not be known because only fragements are preserved. It was therefore later classified as a "miscellaneous treatise".
The Yuzi is contained in the reprint series Miaomiaoge congshu 綿眇閣叢書， Bieliuzi quanshu 别六子全書， Shierzi 十二子, Zihui 子彙, Mohai jinhu 墨海金壺, Shoushange congshu 守山閣叢書, Zhuzi baoyi 諸子褒异 (Zide Studio 自得軒 of Yang Shen 楊慎), Wuzi 五子 (a print from the Jiajing era 嘉靖 1522-1566), the Daoist canon Daozang 道藏, and the Siku quanshu 四庫全書.