realist philosopher of the Song dynasty, a leader in giving neo-Confucianism a metaphysical and epistemological foundation.

The son of a magistrate, Zhang studied Buddhism and Daoism but found his true inspiration in the Confucian Classics. In his chief work, Zhengmeng (“Correcting Youthful Ignorance”), he declared that the world is a unity, with myriad aspects, and all existence is a process of arising and dissolving. qi (“vital energies”) is identified with the Great Ultimate (taiji), the ultimate reality. When qi is influenced by yang forces, it floats and rises, dispersing its vapours. When the yin forces are prevalent, qi sinks and falls, thus condensing and forming the concrete things of the material world.

In the realm of ethics, the one basic virtue is ren (jen) (“humaneness”), but in its various manifestations (i.e., in various human relations) ren becomes many things: filial piety toward parents or respect for an elder brother. Human beings are qi, like all other aspects of the world, and have an original nature that is one with all the things of the world. Their physical nature, however, derives from the physical form into which their qi has been dispersed. Moral self-cultivation consists in a person's attempting to do his duty as a member of society and as a member of the cosmos. One does not try to prolong or extend one's life. The exemplary person understands that “life entails no gain nor death any loss.”

Zhang influenced some of the most eminent later neo-Confucian thinkers; the brothers Cheng Hao (1032–85) and Cheng Yi (1033–1107) were his pupils. His theory of mind was adopted by the great philosopher Zhu Xi (1130–1200), and Wang Fuzhi (Wang Fu-chih) (1619–92) developed Zhang's philosophy into a system that has recently come to be recognized as one of the major achievements of Chinese thought.