 Moore broke with idealism in 1898 and his “Refutation of Idealism” appeared in 1903. This paper did not introduce the concept of sense data, but it formulated the distinction that made him a realist, which he maintained throughout his life, between the act of sensation and its object. Moore contended that every case of sensation involves awareness of two distinct elements, one common to all sensations and the other differing among them. He distinguished the common element, which he called “consciousness”, from the differing “objects” of sensation, which might be blue in one case, green in another. He did not claim to prove that the object is what it seems to be: a material object at a distance, but he endorsed a naïve realism, according to which we are directly aware of “the existence of a table in space” just as we are directly aware of the conscious element (1903: 453).