When did I start to distrust supposed knowledge from the perceptual to the conceptual? When I recognized that when I perceive a tree my head doesn't explode because it didn't duplicate it. Aha, if I'm to trust any knowledge, including provisional, I can trust abstractions. Indeed, that's what the tree is in my brain at a significant etiological terminus. If I'm to recognize other trees and to be able to talk about them, my perceptual apparatus had better be able to abstract relevant tree-properties from trees automatically. The principle: Perceptual 2-D maps are not intrinsically superior to conceptual n-D maps. Hanson makes this sort of point very clear.