ROBERVAL’S SCEPTICISM IN THE ‟ARISTARCHI SAMII DE MUNDI SYSTEMATE”

Abstract

This paper argues for a different interpretation of Roberval’s scepticism in his Aristarchi Samii de mundi systemate. Roberval’s mild sceptical attitude, along with his fake attribution of hiscosmological treatise to the ancient Aristarchus of Samos, are explained by prudential reasons related to censure. I will instead provide a more internalist reading. There are deeper metaphysical and epistemological reasons for Roberval’s pessimism about the prospect of a perfect science of celestial motions, as well as for his (non-realistic) acceptance of heliocentrism as just a more plausible system than Ptolemy’s or Tycho’s. I start by spelling out two distinct sceptical worries conflated in the Aristarchi. The first is a general agnosticism regarding certainty about the causes of the motions of the heavens—it is more of a worry that the true system of the world can never be known. The second is a particular pessimism regarding the prospects of improving astronomy. The same effect (the apparent motions of the heavenly bodies) can be produced by diverse causes. Judging by what seemed to be the most probable physical causes of the heavenly motions, Roberval saw no reason for the existence of a precisely predictable regularity in heavenly motions. Both sceptical attitudes have to do, aside from the cosmology of the Aristarchi, with the theory of science he expounds in his private Principes du debvoir et des cognoissances humaine, and in a fragment he wrote for Mersenne’s Curiouse perspective de Niceron.