Chu Hsi (1130–1200), Neo-Confucian scholar of the Sung dynasty (960–1279), commonly regarded as the greatest Chinese philosopher after Confucius and Mencius. His mentor was Ch’eng Yi (1033–1107), hence the so-called Ch’eng–Chu School. Chu Hsi developed Ch’eng Yi’s ideas into a comprehensive metaphysics of li (principle) and ch’i (material force). Li is incorporeal, one, eternal, and unchanging, always good; ch’i is physical, many, transitory, and changeable, involving both good and evil. They are not to be mixed or separated. Things are composed of both li and ch’i. Chu identifies hsing (human nature) as li, ch’ing (feelings and emotions) as ch’i, and hsin (mind/heart) as ch’i of the subtlest kind, comprising principles. He interprets ko-wu in the Great Learning to mean the investigation of principles inherent in things, and chih-chih to mean the extension of knowledge. He was opposed by Lu Hsiang-shan (1139– 93) and Wang Yang-ming (1472–1529), who argued that mind is principle. Mou Tsung-san thinks that Lu’s and Wang’s position was closer to Mencius’s philosophy, which was honored as orthodoxy. But Ch’eng and Chu’s commentaries on the Four Books were used as the basis for civil service examinations from 1313 until the system was abolished in 1905. See also CH’IEN MU, CHINESE PHILOSOPHY, CONFUCIUS , FUNG YU – LAN , MENCIUS , WANG YANG – MIN. S.-h.L.