The conventional view explains the fact that an image of a cup evokes the word "cup" as a symbolic abstraction of that image. Nowhere in any of these schemes however is there a high resolution fully spatial rendition of the actual object being viewed, and yet the most vivid conscious experience of a cup is of a solid three-dimensional presence at the highest perceptual resolution, complete in color, texture and form.
A cup that is held in the hand is clearly not a retinal image, for the retinal image is only a two-dimensional edge representation. Neither can it be the actual physical cup, because that is out beyond the retina, and therefore we can have no conscious awareness of it directly. The difficulty with the conventional view of perception is that it completely ignores this vivid spatial manifestation as if it did not exist. Indeed, the conventional view would predict a consciousness akin to the phenomenon of blindsight.
It is this function, the construction of a full spatial model of the world, which I believe constitutes the primary function of visual perception. The existence of this internal model, I propose, is identically equivalent to the perception of the object being modeled, whether that model represents a veridical facsimile of the external object, as in true perception, or a distorted misrepresentation, as in the case of illusory or hallucinatory perception. That other function of visual abstraction is, I believe, a secondary function of perception, by no means as essential for practical interaction with the world as the construction of the spatial model. Furthermore, I propose that what abstraction does occur, is an abstraction of that full spatial model, rather than of the impoverished two-dimensional retinal image on which it is based.