This piece raises a lot of questions in my mind, none having to do with the title question. Descartes is in the Netherlands in 1633, three years after the death of Kepler, the fellow who proved that Copernicus was right. No mention is made of the Tychonic system, devised by Tycho Brahe, whose assistant Kepler had been. The Tychonic system was widely accepted at the time by those who disagreed with Copernicus. Galileo, interestingly, did not accept Kepler's findings, because they involved demonstrating that celestial orbits were elliptical, and Galileo rather unscientifically insisted they had to be circular. Even if Descartes had not heard of Kepler's work, he must have known of the Tychonic system, one would think. This whole matter is more complicated that we are usually given to understand.