『塵劫記』のくろ船問題について
概要
In the first edition of the Jinko-ki of 1627, the title of section 14 is “Purchasing from the Black Ship”. From 1631, the following editions have been changed to “Purchasing in Nagasaki”. This problem was calculated by proportional allocation, and the problem scene was a transaction related to trade with China in Nagasaki in the early Edo period. This paper aims to reexamine the conventional way of thinking from the following three points. 1. The trade scene in question is not the Dutch ship at Nagasaki, but the Jesuit commerce with the Portuguese Nau ship. 2. The issue is not ordinary buying, but a special Jesuit business practice. 3. The calculation method for this problem is proportional allocation, but it is not the traditional Chinese mathematics“Shuāi fēn [衰分]”but the equivalent of Western mathematics“regula societatum [rule of copartnership]” introduced by the Jesuits.