ABSTRACT
Descartes regarded his theory of vision as important to his project of replacing theories of a broadly Aristotelian sort with his own mechanistic natural philosophy. It is, for example, in his Dioptrique rather than in his more narrowly philosophical writings that he claims to have laid to rest the ‘intentional species’ that had played such an important role in scholastic epistemology.1 Developing a satisfactory account of vision was necessary, he believed, because ‘the principal reason which moved philosophers to posit real accidents was that they thought the perceptions of the senses could not be explained without them’.2 And vision, of all the senses, is, on the face of it, the least amenable to mechanistic explanation; objects do not touch our eyes, and sight had long been regarded as the most spiritual of the senses. For vision was thought to have the highest power to abstract forms from matter, by contrast with touch which had the lowest power to do so; the eye can see a colour without physically becoming coloured, whereas the hand literally becomes warm when feeling a warm object. Thus, if he could explain vision without employing traditional Aristotelian concepts such as forms, species, or real qualities, providing a mechanistic account of the other senses would presumably pose no difficulties.3
