ニュートン『プリンキピア』における「哲学することの規則IV」追加の動機

Newton added “Rule IV of Reasoning” in the third edition of his Principia. The aim of this paper is to clarify the reason why this Rule was added. Although “Rule IV” is new in the third edition of the Principia, its contents is anticipated in previous texts, especially the second English edition of the Opticks. Nevertheless, Newton added it again. As the background of this addition, I focus on his manuscripts for “Definitions” which was written in the same period as the formation of outlines of “Rule IV”. In these manuscripts, he tries to define body, vacuum, and phenomenon in the daily and physical context in contrast with mathematical definitions in Book I in the Principia. It seems that the plan of “Rule IV” is derived from that of “Definitions”. It is important to note that Newton plans to settle both “Rule of Reasoning” and plan of “Definitions” in the front of Book III in the Principia. Book III is philosophical, that is, physical part whereas Book I and II is mathematical one of the Principia. Newton tried to clarify the goal of Book III through stressing the necessity of daily and sensible phenomenon which is explored in experiments. Therefore, he adds “Rule IV” and declares that experimental philosophy begins with our phenomena in the Principia as “Mathematical Principles of Natural Philosophy”.