Chu Hsi (1130-1200), author of the great Neo-Confucian synthesis, exerted a lasting influence on the thought & life of the Chinese in subsequent centuries. The core of his all-encompassing synthesis was moral & social philosophy, but it also included knowledge about the natural world. His doctrine of ke-wu (investigation of things) & his official duties made him mindful of the specialized knowledged in such scientificÓ traditions as astronomy, harmonics, medicine, etc. In this study of Chu Hsi's thought, Part 1 gives a systematic account of the basic concepts of his natural philosophy as background for understanding his natural knowledge. Part 2 discusses Chu Hsi's actual knowledge about the natural world. Part 3 examines the relation between Chu Hsi & Chinese scientificÓ traditions & compares his natural knowledge with that of the Western scientific tradition.