Perceptual knowledge is knowledge grounded in perceptual experience.
So, we have knowledge that is grounded in perceptual experience. This requires that perceptual experiences be the kind of thing that can ground perceptual knowledge. Thus, one criterion for evaluating accounts of perceptual experience is whether they allow that perceptual experiences can ground perceptual knowledge. John McDowell has proposed an account of perceptual experience that he believes meets this desideratum. He also criticizes certain competing accounts of perceptual experience on the basis that they do not allow that human perceptual experiences ground perceptual knowledge.