Comments on Bill Lycan, "More Layers of Perceptual Content"

(Draft of 6 October; please do not quote without permission) I'm very happy here to be sandwiched between Lycan and Millikan, two of the living philosophers from whom I've probably learned the most, and to whom I am the most grateful. Plus the intermediary position is appropriate for someone commenting on intermediary representations in vision. There's much to like in Bill's account of "layering" in visual representation. For one, it makes explicit and publicizes the notion that there are multiple layers of representation involved even in the seemingly simple achievement of seeing a tree or spotting a duck (or a rabbit, as the case may be). Representations at one level might represent colored expanses, whose shapes are (perhaps) just two dimensional silhouettes; another (much informed by vision, if not within "vision alone") represents everyday three dimensional physical objects. So, as Lycan puts it, visual representata are not always "physical objects of the everyday sort" (see Lycan 1996, 152). Here, here. The representations at different levels can engender differing ontological commitments. A possible visible world might satisfy the content of all the visual representations of colored expanses, but contain no physical objects of the everyday sort. Contrariwise, we might have-and according to Bill we do have-a visible world that satisfies the content of visual representations as of everyday physical objects, but that does not at the same time always satisfy the representations at the "colored expanse" level. In such cases the intentional objects of representations at the colored expanse level are represented, but non-actual. So, to use the original example from Peacocke: One sees two trees of the same size, one of which is further down the road. Hypothesis: One represents a bigger tree-shaped expanse, and a smaller tree-shaped expanse, and by representing those one represents two equally sized trees, one further away. There are trees of those sizes out there, but the tree-shaped expanses, with their differing sizes, are not actual (Lycan 1996, 157-8). Vision scientists certainly do credit the visual system with a variety of representational schemes of differing orders of complexity, from early retinotopic maps of "discontinuities of intensity" up through some sort of visual representation of three dimensional objects or voluminous shapes. It is difficult to gainsay the claim that there are asymmetric priority relations between various of these. One represents the visible edges of objects by representing differences in luminous intensity along loci out there in …