Significantly, Berkeley, in his Essay Towards a New Theory of Vision, leveled a sustained attack on just this geometrical theory of distance perception. At first glance it may seem, as it did to Berkeley, that Descartes’ geometrical theory is produced by a simple error: namely, by the idea that a physiological optics provides an adequate description of the psychological processes of judging distances. In truth, this is the weakest of Berkeley’s objections to Descartes’ theory. Obviously we do not see the (...) angles and lines of convergence when we focus on a distant object, nor are we aware of having used any geometrical rules in judging distance. And Descartes never claimed this. (shrink)

This chapter explains Descartes confusion on sensations, size, shape, position, and motion. Descartes in detail explains that we perceive particular figures or actual bodies affecting our senses much more distinctly than their colours. Descartes construe the perception of position, distance, size, and shape as involving strong intellectual elements and he holds that they differ in this fundamental respect from ordinary perceptions of color, sound, heat and cold, taste, and the like, which are said to consist just in having “sensations” that (...) “arise from the mind-body union.” This position leaves room for uncertainty about what he means when he speaks elsewhere of the near-uselessness of sense perceptions in informing us of particular qualities of bodies, in so far as it opens the possibility of a quite restricted understanding of “sense perception” in these contexts. (shrink)