The formation of the study of Shushu and its development in the Middle Ages: a tentative study of a field of scientific study peculiar to East Asia.

Natural science in East Asia formed a unique field of study called the study of shushu, which consisted of various fields of natural science and divinations derived from the Yijing [Chinese characters: see text]. Though the study of shushu is a field peculiar to East Asia where people want to evaluate the essence of the scientific culture of East Asia properly, it seems indispensable to grasp its structure and historical development. In this paper, the process of transformation of fangshu [Chinese characters: see text] in the pre-Qin period into shushu caused by the great thought revolution occurring in the period of Han period and its development in the Middle Ages are discussed. In particular, the origin of the theory of yinyang [Chinese characters: see text] and the five phases that is the theoretical basis of the study of shushu is studied using materials excavated recently in China. Using the texts preserved in Japan seen in the Wuxing Dayi [Chinese characters: see text] and the Ishinpŏ [Chinese characters: see text] the development of the theory of yinyang and five phases in the Middle Ages and its theoretical characteristics are discussed.