Information about mathematician rene descartes biography
Disagreement with other Cartesian views. Fermat differed also with Cartesian views concerning the law of refraction (the sines of the angles of incidence and refraction of light passing through media of different densities are in a constant ratio), published by Descartes in in La Dioptrique; like La Géométrie, it was an appendix to his celebrated Discours de la méthode.