Epilogue

Abstract

The outcome of these prolegomena to Galileo’s appropriated treatises on Aristotle’s Posterior Analytics may surprise historians and philosophers of science. After all, its central finding is quite simple: that Galileo employed the demonstrative regress of the Paduan Aristotelians, transmitted to him via the lecture notes of Jesuits at the Collegio Romano, to give causal explanations of phenomena he was the first to discover in the emerging sciences of astronomy and mechanics. Galileo felt that these explanations yielded true and certain knowledge on a par with the truth and certitude one attains in ordinary experience of the world of nature. There was, for him, nothing esoteric or deeply metaphysical about his newly discovered truths. For the most part they were established by a straightforward combination of mathematical and physical reasoning in the “mixed science” tradition of his day. If one could understand how sense observation of the phases of the moon, carefully analyzed, can yield apodictic knowledge that a remote object like the moon is a sphere, one would have no difficulty assenting to the startling explanations Galileo gave for what he had seen through his telescope: mountains on that moon, other moons revolving about Jupiter, Venus revolving around the sun. And the same geometrical-physical type of proof, based now on suppositions of the Archimedean type that fitted into his model of the regressus, enabled him to move beyond the ancient statics to a new kinematics or dynamics, one that demonstrated unexpected properties of bodies in local motion as well as at rest.