Petrus van Musschenbroek’s Appropriation of Newton’s Natural-Philosophical Methodology

Steffen Ducheyne

Centre for Logic and Philosophy of Science - Vrije Universiteit Brussel

Petrus van Musschenbroek (1692-1762) has rightfully been considered as an important trailblazer in the diffusion of Newtonianism on the Continent. Together with W. J. ‘s Gravesande, he helped to establish teaching of Newton’s natural philosophy within the university curriculum and the textsbooks which he wrote were of vital importance in its spread and popularization. On the face of it, there are good reasons for portraying Musschenbroek as a ‘Newtonian’. Musschenbroek spent time in England where he became acquainted with Newton, his natural philosophy, and his disciples. During his stay in England he came to accept the basics of Newton’s natural philosophy and the theory of universal gravitation in particular, which he earlier rejected. In his Elementa physicæ conscripta in usus academicos (1734), for instance, he endorsed Newton’s distinction between absolute and relative space and time and he affirmed the theory of universal gravitation and the doctrine of the heterogeneity of white light. After ‘s Gravesande’s death in 1742, Musschenbroek was in full charge of teaching experimental and Newtonian philosophy at his alma mater. However, Musschenbroek did not, as has been correctly pointed out in the literature, accept all of Newton’s doctrines without reservation, which is particularly clear for instance from the position he took in the vis viva dispute. Although he occasionally departed from Newton’s views, at the same time he aligned himself to Newton’s methodological programme, which for him consisted in the fierce rejection of hypotheses, on the one hand, and in the endorsement of empirico-mathematical demonstrations, on the other. On the basis of this, scholars have concluded that Musschenbroek is to be considered as a methodological Newtonian. In my presentation I want to question this conclusion. My endeavour is to show that Musschenbroek developed a series of methodological views, which diverged from Newton’s views on the matter. Although it does make sense to speak of a modest Newtonian influence on Musschenbroek’s methodological ideas, Newton’s work was only one amongst several methodological sources and arguably perhaps not the most important one. First, I call attention to Musschenbroek’s views on the aim of “physics” (“physica” in Latin; “natuurkunde” in Dutch). Contrary to Newton, Musschenbroek endorsed the idea that physics does not unravel the causes of things. Rather, it describes the rules according to which effects occur. Accordingly, in contrast to Newton Musschenbroek put more emphasis on description than on explanation. Second, I explore Musschenbroek’s reception and understanding of Newton’s regulae philosophandi in several of his works. I show that Musschenbroek was one of the few eighteenth-century commentators who properly understood the meaning and methodological significance of Newton’s rules. Rule IV was, as I will show, especially relevant to understand Musschenbroek’s methodological position. Third, I provide an outline of Musschenbroek’s methodological views proper. It will be argued that Musschenbroek drew considerably on Francis Bacon’s and especially Bernard Nieuwentijt’s methodological ideas. All of the above will put into question the claim that Musschenbroek is to be considered as a methodological Newtonian.