Descartes’s Physics: Cosmology, Meteorology, and Mineralogy

Despite concerning a quite significant section of his entire philosophical enterprise, René Descartes’s engagement with physics reveals some chal- lenges.1 Descartes conceived of his physics as a mathematical construction of an order of bodies, made of extended matter. Yet, he firstly focused atten- tion on sublunary bodies, which compose one of his famous essays, later to cosmological bodies, and finally to earthly bodies. In principle, he should have been able to explain all bodies through his methodology, given the fact that there are no mechanical differences between cosmological and earthly bodies. The same nature composes all bodies, which could be reduced to extended matter and motion. But things are more complex. In this chapter, I reconstruct the different phases of Descartes’s engagement with physics, from his first attention to meteorology, the rainbow and parhelia, to his work on cosmology in The World (unpublished, but written in 1632), several manuscripts, The Meteorology (1637), and finally the fourth part of the Principles of Philosophy (1644), where he discusses mineralogy. This chapter aims to provide a clearer reconstruction of the different engagements with inert bodies throughout Descartes’s philosophical career, as he performed several observations and experiments in order to define a corpuscular interpretation of nature.