Descartes and the Puzzle of Sensory Representation (review)

Descartes and the Puzzle of Sensory Representation is an intensely polemical attack on many recent expositions of sensory representation in Descartes, and a defense of De Rosa’s own Descriptive-Causal Account of Sensory Representation. For Descartes, she says, there are two kinds of ideas, sensible and intelligible, both of which have presentational and referential content. The presentational content of sensible ideas consists of touches, tastes, sounds, odors, and colored visual images that are obscure and confused, in that there is nothing like these sensible ideas in the material world. The presentational content of intelligible ideas, on the other hand, is clear and distinct, in that it consists of geometric representations of material bodies that do exist in the world outside the mind. Thus, whenever one has a clear and distinct intelligible perception of a material body that exists outside the mind, one also has at the same time an obscure and confused sensible image of that body as hard, sweet, squeaky, odiferous, and colored. Nothing like these sensible images actually exists in bodies. De Rosa says that the role of sensible imagery is to individuate and differentiate material bodies from one another, which would be difficult to do for geometric representations of similar bodies if all that were presented were their intelligible geometric properties. Sensory representation comes from the causal connection of our sense organs with external material bodies, and intelligible representation comes from the innate idea of matter in our minds. Thus, individual sensory ideas provide obscure descriptions of material bodies in the world external to our minds.

The build-up to this conclusion and the arguments De Rosa poses against other interpretations are beyond succinct abbreviation. Her main stalking horses are Margaret Wilson, Alison Simmons, and Martha Bolton. The amount of intellectual interaction among these four scholars is intense and impressive.

Although De Rosa meets and argues against at least a dozen opposing positions, this does not necessarily provide an argument for her own position, which needs independent confirmation. This confirmation must come from the texts of Descartes. One position De Rosa appeals to throughout is that “according to Descartes, resemblance is not a necessary condition for representation” (34), and she stresses that “there is nothing in the corporeal world that resembles color sensations” (44). But she nowhere disposes of the obvious suggestion that colored sensible and tactile images outline and thus resemble the shapes of external material bodies. In fact, she says that in the Optics, “Descartes is explicit that the patterns in the brain need not resemble what causes them” (177). But in fact, Descartes says that “in no case does an image have to resemble the object it represents in all respects.” Thus it is reasonable to conclude that sensible images can in some respects resemble the geometric patterns and shapes of material bodies.

Nevertheless, De Rosa continues, “it is not resemblance between the brain patterns and their causes that accounts for why the former are signs for the mind to produce ideas that represent the distal causes of the brain patterns” (177). She concludes that “causal accounts fail to explain both why sensory ideas are representations of their causes and the phenomenon of sensory representation” (178). Thus, according to De Rosa, “this capacity must come from internal resources of the mind,” and “brain patterns are taken as signs of their causes because of ideas already provided by the mind” (177).

But in an interpretation De Rosa does not examine, I have shown how resemblance works for Descartes’ sensible ideas in his description of sense perception, from touch, light waves and sound waves, and particles in the nose and on the tongue. From all of these sense-organ encounters with the material world, distinctive isomorphically-keyed material motions are transferred through the nerves to the pineal gland, where brain patterns that are similar to and derived from the shapes and patterns of the material things that caused them are exhibited. This is the ancestor of the...