The argument above might suggest to some readers that perception is based on "assumptions" about the world. It would be a misleading idea for many reasons. For instance, to work by assuming something implies that one knows about or can imagine a more general situation which for the present purpose needs to be narrowed down. However, there is no reason why evolution (nor the resulting animal) should "know" anything about more general conditions. For the evolving animal its ecological niche is the universe. If a perceptual mechanism can pick up useful information in and about this universe, it is there to stay. The difficulties that we as scientists, trained in abstract geometry and theoretical physics, encounter in our attempts at understanding the preconditions for perception should not be ascribed to the perceptual system under study. (Runeson, 1977, p. 176).Take the claim that "to work by assuming something implies that one knows about or can imagine a more general situation which for the present purpose needs to be narrowed down". I don't see this implication. One might well hold the view that natural selection simply exterminated the visual systems without the right "assumptions". So, the visual system just has those assumptions, but not the ability to entertain alternatives. Indeed, a standard cognitivist assumption is that the assumptions might well be merely "implicit".
Nor does this account involve saying the evolution "knows" anything about more general conditions. That is only metaphorical at best.
The last sentences seems to me to be a little strong. I would say that "should not necessarily be ascribed to the perceptual system under study".