Isaac Newton, Richard Bentley and Galileo's Platonic Myth

In both the “Dialogo sopra i due massimi sistemi” (1632) and the “Discorsi e dimostrazioni matematiche intorno a due nuove scienze” (1638), Galileo describes the origins of the planetary system using a cosmogonical myth that he explicitly ascribes to Plato. In this essay I will focus on how Galileo presented his Platonic cosmogony to make it conform with the world system proposed by Copernicus in “De revolutionibus” (1543), and how such a cosmogony was essential in order to give a universal value to Galileo’s theory of motion, and to justify in physical terms his commitment to a heliocentric cosmology. In particular, I will try to show how Galileo’s rejection of the Keplerian theory that the planets move in elliptical orbits could be a consequence of his cosmogonical hypothesis. This brief analysis will allow me to examine how Newton interpreted the Platonic myth as used by Galileo and how he demonstrated that the Italian scientist’s philosophical speculations fell short of explaining Kepler’s laws of planetary motion.