Chang Po-tuan, styled Tzu-yang, lived from approximately 983 to 1082. He is considered the founder of the so-called southern school of Complete Reality Taoism. As he lived before the widespread public recognition and institutionalization of Complete Reality Taoism that took place under the successors and descendants of Wang Che (1113-1171), founder of the northern school, little is known about his life. Indeed, apart from his retrospective recognition as the first patriarch of the southern school of Complete Reality Taoism, Chang is mainly known simply as the author of Understanding Reality, considered a basic text by practitioners of both northern and southern schools.