Among the products of Jesuits' scientific influence in "the Christian century" Japan (1549-1650), a Japanese treatise called
Kenkon bensetsu (A Discussion on the Heaven and the Earth with Critical Commentaries) deserves a special attention. The book consists of an original text and indented annotations by a commentator. The preface, which bears the name of the commentator Mukai Genshou (1609-1677), a Medico-Confucian in Nagasaki, explains that the original text was a Japanese translation, from some Western astronomical book, by the apostate Jesuit Christovao Ferreira (1580-1650).
According to Genshou's preface written around 1650's, the formation of
Kenkon bensetsu is as follows. Ferreira had been engaged in missionary activities in Japan since 1609 before he was caught in Nagasaki in 1633. He became an apostate and naturalized, taking a new Japanese name Sawano Chuuan. He was ordered by Inoue Chikugonokami, Inspector General against the Pagans, to translate into Japanese a Western astronomy book, which had been confiscated from a Christian father caught in 1643. Chuuan (Ferreira) wrote the text of the translation in the Roman alphabet, because he could not write Japanese well, though he was able to speak and read Japanese. A Nagasaki interpreter Nishi Kichibei converted the text into Japanese. And then, Gensho made critical comments on the Western cosmological ideas put forward by Chuuan.
However, we have another report about
Kenkon bensetsu's origin, which is quite different from Genshou's explanation. The report was made by Ro Sousetsu (1675-1729), a Nagasaki interpreter of Chinese language, in his private letter to Watanabe Gunzou at the beginning of 18th century. Since Sousetsu's account is seldom known to non-Japanese readers, here I translate the text into English. You can see the original Japanese text in Ryuji HIRAOKA and Kayoko Hibi "The Sokuryou-higen (Private Letters on Surveying) edited by Hosoi Koutaku",
Kagakushi Kenkyuu (Journal of History of Science, Japan) 43, 2004, p.96.
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In Nagasaki, we have a book of 2 volumes which is called
Kana tenmon shou (An extract on astronomy written in kana). Also entitled
Sangoku unki tsuuyou shou (A substantial extract on
yun-qi theory of 3 countries), it gives a highly reasonable explanation about astronomy. This book was made when a doctor called Asano Choutaku came from Edo [to Nagasaki] and made an agent of foreign origin (
Nanban no metsuke) Sawano Chuuan write about Western astronomical learning. At that time, a buddhist monk Shougin, the chief priest of Kougenji temple, dictated (
Hitsuyaku) what Chuuan told, since Chuuan, although well versed in reading Japanese language, could not write its characters. This is why the book is also called
Kougenji tenmonsho (An astronomy book of Kougenji temple). I suppose the original autograph by Shougin must have been preserved at Yoshimura Gouemon's place. Since Gouemon's grandfather was a servant of Suetsugu Heizou, Shogin's autograph was submitted also to Heizou. It is that book which has been passed down to nowadays. Moreover, we have a book of 4 volumes called
Kenkon bensetsu which cites this book of 2 volumes in due order and disproofs them. This book was edited by Mukai Genshou, a father of Mukai Gensei of our time. Genshou later went to Kyoto to be a celebrated doctor. But his criticism about astronomical topics [in
Kenkon bensetsu] also includes those which are dubious.
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