 Scholars have difficulty finding an argument purporting to show that heat, etc. as we sense it does not inhere in bodies. Some suggest that his best argument is the intelligibility, simplicity, and explanatory adequacy of his mechanist theory (CSM 1.284–86, 288; AT 7.121–123, 326). But it is conclusive only in conjunction with the norm expressed by Ockham’s razor. (Downing 2011: 113–14). Another problem is that Descartes writes that his mechanist physics explains the nature of light, heat, etc. because he presupposes that they are “only in our senses… and not in the objects we perceive by sense” (Letter to Chanut,26 Feb 1649; CSM 3.369; AT 5.291–2). It is doubtful Descartes would advance the explanatory adequacy argument unless he had an independent argument for the presupposition (for a different analysis, see Downing 2011: 114).