There are four standpoints from which a Marxist must proceed to form a judgment of empirio-criticism.
First and foremost, the theoretical foundations of this philosophy must be compared with those of dialectical materialism. Such a comparison, to which the first three chapters were devoted, reveals, along the whole line of epistemological problems, the thoroughly reactionary character of empirio-criticism, which uses new artifices, terms and subtleties to disguise the old errors of idealism and agnosticism. Only utter ignorance of the nature of philosophical materialism generally and of the nature of Marx’s and Engels’ dialectical method can lead one to speak of “combining” empirio-criticism and Marxism.
Secondly, the place of empirio-criticism, as one very small school of specialists in philosophy, in relation to the other modern schools of philosophy must be determined. Both Mach and Avenarius started with Kant and, leaving him, proceeded not towards materialism, but in the opposite direction, towards Hume and Berkeley. Imagining that he was “purifying experience” generally, Avenarius was in fact only purifying agnosticism of Kantianism. The whole school of Mach and Avenarius is moving more and more definitely towards idealism, hand in hand with one of the most reactionary of the idealist schools, viz., the so-called immanentists.
Thirdly, the indubitable connection between Machism and one school in one branch of modern science must be borne in mind. The vast majority of scientists, both generally and in this special branch of science in question, viz., physics, are invariably on the side of materialism. A minority of new physicists, however, influenced by the breakdown of old theories brought about by the great discoveries of recent years, influenced by the crisis in the new physics, which has very clearly revealed the relativity of our knowledge, have, owing to their ignorance of dialectics, slipped into idealism by way of relativism. The physical idealism in vogue today is as reactionary and transitory an infatuation as was the fashionable physiological idealism of the recent past.
Fourthly, behind the epistemological scholasticism of empirio-criticism one must not fail to see the struggle of parties in philosophy, a struggle which in the last analysis reflects the tendencies and ideology of the antagonistic classes in modern society. Recent philosophy is as partisan as was philosophy two thousand years ago. The contending parties are essentially, although it is concealed by a pseudo-erudite quackery of new terms or by a feeble-minded non-partisanship, materialism and idealism. The latter is merely a subtle, refined form of fideism, which stands fully armed, commands vast organisations and steadily continues to exercise influence on the masses, turning the slightest vacillation in philosophical thought to its own advantage. The objective, class role of empirio-criticism consists entirely in rendering faithful service to the fideists in their struggle against materialism in general and historical materialism in particular.