Abstract
The Nanban unkiron 南蠻運氣論 (Yunqi theory of the southern barbarians), compiled in Nagasaki in the mid-seventeenth century, occupies a unique position in the first influx of Western natural philosophy to Japan. Although the book discusses Aristotelian cosmology of Jesuit origin, some technical terms are modified according to the Chinese yunqi theory 運氣論 (the doctrine of five periods and six qi), and several new passages are inserted into the text from related Chinese treatises. While pursuing the possible author and origin of the book, this chapter argues that (1) the unknown author tried to decipher Aristotelian cosmology in terms of the Chinese yunqi theory, (2) his editorial aim was not to camouflage the Christian origin of the treatise, as previous studies have implied, but rather to rationalize the Western theory using Chinese theory, and (3) the process by which Japanese society received the book was not a replacement of the old cosmology by the new one, but an assimilation and absorption of the latter into the existing cosmological system.