  There is, however, a way of understanding the sceptical question which Quine takes seriously. Philosophers have been concerned with the gap between what is given in experience and the knowledge that we take ourselves to have. Quine invokes gestalt psychology and argues that the simple sensory ideas which Berkeley and Hume had claimed were given by the senses are not in fact given, that we see things in three-dimensions, for example, instead of having to infer the third. He does not, however, conclude that there is no problem at all here. Rather, he says, “the problem was real but wrongly viewed” (1974, 2). Epistemology, as he sees it, is here “confronting a challenge to natural science that arises from within natural science.” (loc. cit.). What is the challenge? It starts with what Quine takes to be “a finding of natural science itself… that our information about the world comes only through impacts on our sensory receptors” (1990a, 19). The sceptical challenge is then: “How… could one hope to find out about that external world from such meager traces? In short, if our science were true, how could we know it?” (1974, 2).