An early historian of Confucian tradition, Liu Xiang (77-6 B.C.E.), claimed that by his time the Confucians had divided into 103 schools of thought, each defined by its distinctive manner of interpreting the essential texts. Whether that was literally the case or not, it is clear that during the Song and later dynasties, several important schools developed within the larger phenomenon called Neo-Confucianism. The two main branches became known as the School of Principle and the School of Mind, according to their respective theoretical points of departure.

The School of Principle (li xue) was also called the Cheng-Zhu school, combining the first names of the men it claims as its founders, Cheng Yi (1033-1107), his brother Cheng Hao (1032-85), and the later Zhu Xi (1130-1200). The brothers Cheng developed a sophisticated theory in which “principle” (li) meant not the classical Confucian rites and canons of social propriety, but an unchanging universal law inherent in all nature. Zhu Xi further refined that concept of principle, defining it as the Great Ultimate from which all forces in nature emerge. In what one might call a variety of “process theology,” Zhu Xi argued that the path to ethical development was “the investigation of things.”

The other major branch of Neo-Confucian thinking was known as the School of Mind (xin xue). Wang Yang Ming (1472-1529) was one of the school’s leading lights. Principle, he argued, was not merely a transcendent and inaccessible cosmic force, but was one with the human mind. He taught that one could cultivate good conduct through “reverent seriousness,” a type of meditative discipline through which one could realize the unity of mind and principle.