or Chang Tsai born 1020, Chang'an, China died 1077, China Realist philosopher of the Song dynasty. The son of a magistrate, he studied Buddhism and Daoism before being inspired by the Confucian classics. In his Cheng-meng, he declared the universe a unity with myriad aspects and all existence an eternal integration and disintegration. Ren (humaneness) is the basic virtue, and morality consists in doing one's duty as a member of society and of the universe