  Moore's most famous criticisms of idealism are contained in his paper ‘The Refutation of Idealism’ (1903). The basic theme of this paper is the extension to sense-experience of the strong distinction between the mind and its objects which we have encountered in connection with meaning. Moore concentrates here on the case of a ‘sensation of blue’ and maintains that this experience is a kind of ‘diaphanous’ consciousness or awareness of blue, which is not a ‘content’ of experience at all, but something real whose existence is not dependent on experience. His argument here is in part phenomenological: ‘when we try to introspect the sensation of blue, all we can see is the blue’ (41); but he also argues that to suppose otherwise, that the ‘blue’ is merely a content of the experience is to suppose that it is a quality of the experience, so that the experience is blue in much the way in which a blue bead is blue, which he takes to be absurd. Not surprisingly Moore's critics were not happy with this comparison, but it was not until the formulation of the ‘adverbial’ theory of experience by Ducasse in the 1940's, according to which someone who has a sensation of blue is someone who ‘senses bluely’, that there was a reasonably robust response to Moore's criticism. What is, nonetheless, odd about Moore's paper is that he makes no attempt to address the famous ‘argument from illusion’. Moore concludes that ‘“blue” is as much an object, and as little a mere content, of my experience, when I experience it, as the most exalted and independent real thing of which I am ever aware’ (42). As he was soon to realise, more needs to be said to handle cases in which something which is not in fact blue looks blue.