Descartes was an early advocate of many aspects of Copernican astronomy, in particular, the heliocentric premise that the earth orbits the sun, but the details of his particular version of Copernicanism have long baffled philosophers and scientists, and the whole affair is symptomatic of the complex relationship that existed between science and religion in the seventeenth century.

The Ptolemaic system, with its geocentric hypothesis that the earth is at rest at the center of the universe, was the theory accepted by the church during Copernicus's life (1473–1543), although by Descartes’ day most natural philosophers had turned to Copernicus's own system or the less radical Tychonic system, the latter upholding geocentrism (earth-centered universe). In his early, unpublished treatise on natural philosophy, The World (1633), Descartes advanced the Copernican idea that the earth moves around the sun, along with all of the other planets in the solar system (AT XI 64, G 41). But the news that Galileo had violated church censorship by embracing Copernicanism led Descartes to withdraw the work from publication. Writing to Mersenne in the fall of 1633, he comments that he was astonished to hear of Galileo's censure and adds “that if the view [that the earth moves] is false, so too are the entire foundations of my philosophy” (AT I 271, CSMK 41).

In 1644 Descartes published his Principles of Philosophy, which generally follows the outline of his theory of planetary motions accepted in The World, although it contains a more elaborate, Scholastic-influenced account of motion that would have ramifications for attributing rest and motion to bodies, including planets. In short, while motion can be taken in the ordinary sense as a mere change of place, Descartes’ proper definition of motion is the transference of a body from the neighborhood of contiguous bodies that surround it that are taken to be at rest, with rest being the absence of such a transference (AT VIIIA 53–54, CSM I 233). The Principles also accepts, as did the World, a matter-filled world (or plenum) that is absent of any void spaces, as well as his vortex theory of planetary motion. The vortex theory holds that the planets are situated in large bands of particles that circle around the sun, with each planet enclosed in a different band moving at different speeds.