Cheng Yi

Song dynasty Neo-Confucian philosopher who developed the concept of li (principle/pattern) as the metaphysical structure underlying all things and human moral nature — foundational for the Cheng-Zhu school.

Li is the universal principle that gives each thing its nature and function; the investigation of things (gewu) and extension of knowledge (zhizhi) are the methods for grasping li; moral cultivation requires studying li in things, including one's own moral nature.