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Materialism and idealism differ in their answers to the question of the source of our knowledge and of the relation of knowledge (and of the “mental” in general) to the physical world; while the question of the structure of matter, of atoms and electrons, is a question that concerns only this “physical world”. When the physicists say “matter disappears” they mean that hitherto science reduced its investigations of the physical world to three ultimate concepts: matter, electricity and ether; now only the two former remain. For it has become possible to reduce matter to electricity; the atom can be explained as resembling an infinitely small solar system, within which negative electrons move around a positive electron with a definite (and, as we have seen, enormously large) velocity. It is consequently possible to reduce the physical world from scores of elements to two or three elements (inasmuch as positive and negative electrons constitute “two essentially distinct kinds of matter”, as the physicist Pellat says – Rey, op. cit., pp. 294-95). Hence natural science leads to the “unity of matter” (ibid.) – such is the real meaning of the statement about the disappearance of matter, its replacement by electricity, etc., which is leading so many people astray. “Matter disappears” means that the limit within which we have hitherto known matter disappears and that our knowledge is penetrating deeper; properties of matter are likewise disappearing which formerly seemed absolute, immutable, and primary (impenetrability, inertia, mass, etc.) and which are now revealed to be relative and characteristic only of certain states of matter. For the sole “property” of matter with whose recognition philosophical materialism is bound up is the property of being an objective reality, of existing outside the mind.
V.I.Lenin, Materialism and Empirio-Criticism: Critical Comments on a Reactionary Philosophy, 1908, Progress Publishers, Moscow, 1975, pp. 240-41
Part two/to be continued…
Full text at Marxists Internet Archive