Domenico Bertoloni Meli

Newton, Descartes and the Role of Experiments in Principia Mathematica

In this essay I offer a fresh reading of Newton's Principia Mathematica based on the experiments discussed in the text. Traditionally, Principia Mathematica has been considered as a mathematical masterpiece, whereas Newtonian scholars interested in experiment have looked at the Opticks. Some of the experiments in the Principia, such as the rotating bucket experiment or the one proving that gravitational and inertial mass are proportional, have been discussed in different contexts, but surprisingly we still lack an overall study of the role experiments play in Newton's masterpiece as a whole.

An investigation of this topic reveals a surprising number of links among many of the experiments discussed by Newton. These links are both conceptual and material. Conceptually, one finds links stretching from the definitions, to book II on motion in a resisting medium, to book III. Materially, one finds that Newton relied extensively on pendulums. At times possibly the very same apparatus seems to be employed in different experiments. An overall look at the experiments in the Principia shows that Newton did not rely on them at the beginning of his investigations, but rather at a later stage in the midst of his extraordinary creative effort. His experiments show a strong anti-Cartesian vein and at times seem to be designed to refute specific passages of Descartes' Principia Philosophiae. Thus the study of a surprisingly neglected area of Newtons's work provides fresh insights into its formative stages as well as into Newton's agenda.