246 Ayao KuwAKi 



This so called revision of the J6-Ky6 era marked an epoch in the 

 development of astronomy in Japan and henceforth came a continuous 

 stream of publications on Japanese chronology, on commentaries of 

 Chinese calendology, and on explanations of astronomical problems from 

 writers in Yedo, Kyoto, Nagasaki, and other places. Among these were, 

 besides those expounding the old Chinese astronomical theoreis, books 

 based on recent astronomical works of the Jesuits in China which had 

 been placed under the ban some years previously Nishikawa Joken 

 of Nagasaki, was not only well versed in Chinese astronomical knowledge 

 of this kind, but also had some acquaintance of the recent Dutch 

 calendar. Nakane Genkei of Kyoto was also famous as a calendologist. 



The orthodox learning of Japan at this epoch was the Chinese 

 philosophy of Chu-Tse originating in the Sung dynasty of China. Its 

 metaphysical principle was a dualism based upon '^Ri" (principle) and 

 "Ki" (matter). 



Against this predominating doctrine, Ito Jinsai of Kyoto, Kaibara 

 Ekiken of Chikuzen, and later Miura Baien of Bungo propounded a 

 monism based on "Ki" (Matter). Among these, Baien attempted most 

 elaborately to formulate a system of natural philosophy, while science 

 in Japan was in the meantime confronting a serious crisis. 



As has already been mentioned, the more vulgar of the Japanese 

 astronomers of that day were nothing more than mere astrologists while 

 the more scientific ones were adherents of the geocentric theory taught 

 by the Jesuit missionaries. As actual observations of the heavens were 

 attemj3ted with more and more exactness, these also began to recognize 

 the crudeness of their theory. Asada Koritsu, a friend of Miura Baien 

 mentioned above, was the most prominent of these actual observers. 

 He later left his native province of Bungo and started a private school 

 in Osaka, where he counted many brilliant students among his pupils, 

 luo Chukei who attained great fame by his successful survey of Japan's 

 coast lines before and after 1800 was initiated into his science by one 

 of the pupils of Asada. 



Tokugawa Yoshimune, who was the Shogun from 1716 to 1745, 

 was fond of astronomical observations and founded an observatory in 

 the rear garden of his castle. In 1718, he invited Nishikawa Joken 

 from Nagasaki and Nakane Genkei from Kyoto and instituted enquiries 

 on astronomical questions. This scientific interest of the Shogun became 

 the motive power for raising, in 1720, the ban upon European books 

 and their Chinese translations except for those on religion. 



