We have been going through a period in the philosophy of science in which it has been dominated by the theory of the dematerialization of matter. From Eddington in 1927 to Hanson in the present day, this theory, in one formulation or another, has been maintained. Its adherents suppose that matter upon examination can be resolved into mental constructs of every description, from organized sets of sense impressions to mathematical equations. The idealists are so dazzled by the conditions under which the mental recognition of the extra-mental world occurs that they end by doubting the genuineness of the extra-mental world. But there are reasons to suspect that the idealistic interpretation is not the correct one, and I shall attempt here to present (though not to prove) the counter position. The materialist considers the extra-mental world genuine, but, as we shall see, it is not simply the case of an old materialism confronted with new evidence by the idealists. There is evidence for a new materialism as well. Thus what we have perhaps is an ancient controversy under fresh guises, a new idealism confronted by a new materialism.