Chu Hsi (1130-1200) exerted a lasting influence on the thought and life of the Chinese in subsequent cent. The core of his synthesis was moral and social philosophy, but it also included knowledge about the natural world. His doctrine of ke-wu (invest. of things) made him mindful of the specialized knowledged in such “scientific” traditions as astronomy, harmonics, med., etc. This study of Chu Hsi’s thought gives a systematic account of the basic concepts of his natural philosophy. Also discusses Chu Hsi’s actual knowledge about the natural world. And examines the relation between Chu Hsi and Chinese “scientific” traditions and compares his natural knowledge with that of the Western scientific tradition.