Physics and Metaphysics in Descartes and Newton

Isaac Newton had a vexed relationship with his most important immediate predecessor in mathematics and philosophy, René Descartes. He was typically loath to admit the importance of Cartesian ideas for the development of his own thinking in mathematics and natural philosophy. For this reason, generations of students and scholars relying on Newton’s published work had little inkling of Descartes’s significance. This unfortunate fact was compounded by the tendency of philosophers to focus on the Meditations or the Regulae in their scholarship, for it was Descartes’s Principles above all that influenced Newton’s thinking as a young man. With the discovery of a previously unpublished manuscript amongst Newton’s papers by two famous historians of science in the middle of the twentieth century, everything changed. The manuscript, now known as De Gravitatione after its first line, illustrates the astonishing care with which Newton read the Principles, focusing his critical acumen on Descartes’s understanding of space, time, and motion. These criticisms of Descartes, in turn, shine light on otherwise opaque passages in Newton’s most significant published discussion of space, time, and motion, the Scholium in Principia mathematica. Indeed, the very title of the latter work represents both an homage to, and a swipe at, Descartes’s work: Newton would offer mathematical principles of natural philosophy to replace Descartes’s qualitative account. It is not a stretch to say that Newton saw further because he stood on Descartes’s shoulders, even if he wouldn’t admit it publicly.