Jean Perrin and the philosophers’ stories: The role of multiple determination in determining avogadro’s number

The French physicist Jean Baptiste Perrin is widely credited with providing the conclusive argument for atomism. The most well-known part of Perrin’s argument is his description of 13 different procedures for determining Avogadro’s number (N)—the number of atoms, ions, and molecules contained in a gram-atom, gram-ion, and grammole of a substance, respectively. Because of its success in ending the atomism debates, Perrin’s argument has been the focus of much philosophical interest. Various philosophers have reached different conclusions, however, not only about the argument’s general rationale but also about the role that the multiple determination of N played in it. This article emphasizes the historical development of Perrin’s experimental work in order to understand the role that the multiple determination of molecular magnitudes played in his argument for molecular reality. It defends the claim that Perrin used the multiple determination strategy to put forward an exceptionally strong no-coincidence argument, to argue for both the correctness of the values for the molecular magnitudes determined and the validity of the auxiliary assumptions upon which the different determinations were based. The historicist approach also allows for the identification of the elements responsible for the epistemic strength of Perrin’s no-coincidence argument.