Such is the title under which Friedrich Adler, lecturer at the University of Zürich, probably the only German author also anxious to supplement Marx with Machism, writes of Mach. And this naïve university lecturer must be given his due: in his simplicity of heart he does Machism more harm than good. At least, he puts the question point-blank—did Mach really “discover the world-elements"? If so, then, only very backward and ignorant people, of course, can still remain materialists. Or is this discovery a return on the part of Mach to the old philosophical errors?
We saw that Mach in 1872 and Avenarius in 1876 held a purely idealist view; for them the world is our sensation. In 1883 Mach’s Mechanik appeared, and in the preface to the first edition Mach refers to Avenarius’ Prolegomena, and greets his ideas as being “very close” (sehr verwandte) to his own philosophy. Here are the arguments in the Mechanik concerning the elements: “All natural science can only picture and represent (nachbilden und vorbilden) complexes of those elements which we ordinarily call sensations. It is a matter of the connection of these elements. . . . The connection of A (heat) with B (flame) is a problem of physics, that of A and N (nerves) a problem of physiology. Neither exists separately; both exist in conjunction. Only temporarily can we neglect either. Even processes that are apparently purely mechanical, are thus always physiological” (op. cit., German ed., p. 498). We find the same in the Analysis of Sensations: “Wherever . . . the terms ‘sensation,’ ‘complex of sensations,’ are used alongside of or in place of the terms ‘element,’ ‘complex of elements,’ it must be borne in mind that it is only in this connection [namely, in the connection of A, B, C with K, L, M, that is, in the connection of “complexes which we ordinarily call bodies” with “the complex which we call our body”] and relation, only in this functional dependence that the elements are sensations. In another functional dependence they are at the same time physical objects” (Russian translation, pp. 23 and 17). “A colour is a physical object when we consider its dependence, for instance, upon the source of illumination (other colours, temperatures, spaces and so forth). When we, however, consider its dependence upon the retina (the elements K, L, M), it is a psychological object, a sensation” (ibid., p. 24).
Thus the discovery of the world-elements amounts to this:
1)all that exists is declared to be sensation,
2)sensations are called elements,
3)elements are divided into the physical and the psychical; the latter is that which depends on the human nerves and the human organism generally; the former does not depend on them;
4)the connection of physical elements and the connection of psychical elements, it is declared, do not exist separately from each other; they exist only in conjunction;
5)it is possible only temporarily to leave one or the other connection out of account;
6)the “new” theory is declared to be free from “one-sidedness.”
Indeed, it is not one-sidedness we have here, but an in coherent jumble of antithetical philosophical points of view. Since you base yourself only on sensations you do not correct the “one-sidedness” of your idealism by the term “element,” but only confuse the issue and cravenly hide from your own theory. In a word, you eliminate the antithesis between the physical and psychical, between materialism (which regards nature, matter, as primary) and idealism (which regards spirit, mind, sensation as primary); indeed, you promptly restore this antithesis; you restore it surreptitiously, retreating from your own fundamental premise! For, if elements are sensations, you have no right even for a moment to accept the existence of “elements” independently of my nerves and my mind. But if you do admit physical objects that are independent of my nerves and my sensations and that cause sensation only by acting upon my retina—you are disgracefully abandoning your “one-sided” idealism and adopting the standpoint of “one-sided” materialism! If colour is a sensation only depending upon the retina (as natural science compels you to admit), then light rays, falling upon the retina, produce the sensation of colour. This means that outside us, independently of us and of our minds, there exists a movement of matter, let us say of ether waves of a definite length and of a definite velocity, which, acting upon the retina, produce in man the sensation of a particular colour. This is precisely how natural science regards it. It explains the sensations of various colours by the various lengths of light-waves existing outside the human retina, outside man and independently of him. This is materialism: matter acting upon our sense-organs produces sensation. Sensation depends on the brain, nerves, retina, etc., i.e., on matter organised in a definite way. The existence of matter does not depend on sensation. Matter is primary. Sensation, thought, consciousness are the supreme product of matter organised in a particular way. Such are the views of materialism in general, and of Marx and Engels in particular. Mach and Avenarius secretly smuggle in materialism by means of the word “element,” which supposedly frees their theory of the “one-sidedness” of subjective idealism, supposedly permits the assumption that the mental is dependent on the retina, nerves and so forth, and the assumption that the physical is independent of the human organism. In fact, of course, the trick with the word “element” is a wretched sophistry, for a materialist who reads Mach and Avenarius will immediately ask: what are the “elements"? It would, indeed, be childish to think that one can dispose of the fundamental philosophical trends by inventing a new word. Either the “element” is a sensation, as all empirio-criticists, Mach, Avenarius, Petzoldt, etc., maintain—in which case your philosophy, gentlemen, is idealism vainly seeking to hide the nakedness of its solipsism under the cloak of a more “objective” terminology; or the “element” is not a sensation—in which case absolutely no thought whatever is attached to the “new” term; it is merely an empty bauble.
Take Petzoldt, for instance, the last word in empirio-criticism, as V. Lesevich, the first and most outstanding Russian empirio-criticist describes him. Having defined elements as sensations, he says in the second volume of the work mentioned: “In the statement that ‘sensations are the elements of the world’ one must guard against taking the term ‘sensation’ as denoting something only subjective and therefore ethereal, transforming the ordinary picture of the world into an illusion (Verflüchtigendes)."
One speaks of what hurts one most! Petzoldt feels that the world “evaporates” (verflüchtigt sich), or becomes transformed into an illusion, when sensations are regarded as world-elements. And the good Petzoldt imagines that he helps matters by the reservation that sensation must not be taken as something only subjective! Is this not a ridiculous sophistry? Does it make any difference whether we “take” sensation as sensation or whether we try to stretch the meaning of the term? Does this do away with the fact that sensations in man are connected with normally functioning nerves, retina, brain, etc., that the external world exists independently of our sensations? If you are not trying to evade the issue by a subterfuge, if you are really in earnest in wanting to “guard” against subjectivism and solipsism, you must above all guard against the fundamental idealist premises of your philosophy; you must replace the idealist line of your philosophy (from sensations to the external world) by the materialist line (from the external world to sensations); you must abandon that empty and muddled verbal embellishment, “element,” and simply say that colour is the result of the action of a physical object on the retina, which is the same as saying that sensation is a result of the action of matter on our sense-organs.
Let us take Avenarius. The most valuable material on the question of the “elements” is to be found in his last work (and, it might be said, the most important for the comprehension of his philosophy), Notes on the Concept of the Subject of Psychology. The author, by the way, here gives a very “graphic” table (Vol. XVIII, p. 410), the main part of which we reproduce here:
Things, or the substantial
Elements, complexes of elements: Corporeal things
Thoughts, or the mental (Gedankenhaftes)
Incorporeal things, recollections and fantasies
Compare this with what Mach says after all his elucidation of the “elements” (Analysis of Sensations, p. 33): “It is not bodies that produce sensations, but complexes of elements (complexes of sensations) that make up bodies.” Here you have the “discovery of the world-elements” that overcomes the one-sidedness of idealism and materialism! At first we are assured that the “elements” are something new, both physical and psychical at the same time; then a little correction is surreptitiously inserted: instead of the crude, materialist differentiation of matter (bodies, things) and the psychical (sensations, recollections, fantasies) we are presented with the doctrine of “recent positivism” regarding elements substantial and elements mental. Adler (Fritz) did not gain very much from “the discovery of the world-elements"!
Bogdanov, arguing against Plekhanov in 1906, wrote: “. . . I cannot own myself a Machian in philosophy. In the general philosophical conception there is only one thing I borrowed from Mach—the idea of the neutrality of the elements of experience in relation to the ‘physical’ and ‘psychical’ and the dependence of these characteristics solely on the connection of experience.” (Empirio-Monism, Bk. III, St. Petersburg, 1906, p. xli.) This is as though a religious man were to say—I cannot own myself a believer in religion, for there is “only one thing” I have borrowed from the believers—the belief in God. This “only one thing” which Bogdanov borrowed from Mach is the basic error of Machism, the basic falsity of its entire philosophy. Those deviations of Bogdanov’s from empirio-criticism to which he himself attaches great significance are in fact of entirely secondary importance and amount to nothing more than inconsiderable private and individual differences between the various empirio-criticists who are approved by Mach and who approve Mach (we shall speak of this in greater detail later). Hence when Bogdanov was annoyed at being confused with the Machians he only revealed his failure to understand what radically distinguishes materialism from what is common to Bogdanov and to all other Machians. How Bogdanov developed, improved or worsened Machism is not important What is important is that he has abandoned the materialist standpoint and has thereby inevitably condemned himself to confusion and idealist aberrations.
In 1899, as we saw, Bogdanov had the correct standpoint when he wrote: “The image of the man before me, directly given to me by vision, is a sensation.” Bogdanov did not trouble to give a criticism of this earlier position of his. He blindly believed Mach and began to repeat after him that the “elements” of experience are neutral in relation to the physical and psychical. “As has been established by recent positivist philosophy,” wrote Bogdanov in Book I of Empirio-Monism (2nd ed., p. 90), “the elements of psychical experience are identical with the elements of experience in general, as they are identical with the elements of physical experience.” Or in 1906 (Bk. III, p. xx): “as to ‘idealism,’ can it be called idealism merely on the grounds that the elements of ‘physical experience’ are regarded as identical with the elements of ‘psychical experience,’ or with elementary sensations—when this is simply an indubitable fact?”
Here we have the true source of all Bogdanov’s philosophical misadventures, a source which he shares with the rest of the Machians. We can and must call it idealism when “the elements of physical experience” (i.e., the physical, the external world, matter) are regarded as identical with sensations, for this is sheer Berkeleianism. There is not a trace here of recent philosophy, or positivist philosophy, or of indubitable fact. It is merely an old, old idealist sophism. And were one to ask Bogdanov how he would prove the “indubitable fact” that the physical is identical with sensations, one would get no other argument save the eternal refrain of the idealists: I am aware only of my sensations; the “testimony of self-consciousness” (die Aussage des Selbstbewusstseins) of Avenarius in his Prolegomena (2nd German ed., § 93, p. 56); or: “in our experience [which testifies that “we are sentient substance”] sensation is given us with more certainty than is substantiality” (ibid., § 91, p. 55), and so on and so forth. Bogdanov (trusting Mach) accepted a reactionary philosophical trick as an “indubitable fact.” For, indeed, not a single fact was or could be cited which would refute the view that sensation is an image of the external world—a view which was shared by Bogdanov in 1899 and which is shared by natural science to this day. In his philosophical wanderings the physicist Mach has completely strayed from the path of “modern science.” Regarding this important circumstance, which Bogdanov overlooked, we shall have much to say later.
One of the circumstances which helped Bogdanov to jump so quickly from the materialism of the natural scientists to the muddled idealism of Mach was (apart from the influence of Ostwald) Avenarius’ doctrine of the dependent and independent series of experience. Bogdanov himself expounds the matter in Book I of his Empirio-Monism thus: “In so far as the data of experience appear in dependence upon the state of the particular nervous system, they form the psychical world of the particular person, in so far as the data of experience are taken outside of such a dependence, we have before us the physical world. Avenarius therefore characterises these two realms of experience respectively as the dependent series and the independent series of experience” (p. 18).
That is just the whole trouble, the doctrine of the independent (i.e., independent of human sensation) “series” is a surreptitious importation of materialism, which, from the standpoint of a philosophy that maintains that bodies are complexes of sensations, that sensations are “identical” with physical “elements,” is illegitimate, arbitrary, and eclectic. For once you have recognised that the source of light and light-waves exists independently of man and the human consciousness, that colour is dependent on the action of these waves upon the retina, you have in fact adopted the materialist standpoint and have completely destroyed all the “indubitable facts” of idealism, together with all “the complexes of sensations,” the elements discovered by recent positivism, and similar nonsense.
That is just the whole trouble. Bogdanov (like the rest of the Russian Machians) has never looked into the idealist views originally held by Mach and Avenarius, has never understood their fundamental idealist premises, and has therefore failed to discover the illegitimacy and eclecticism of their subsequent attempts to smuggle in materialism surreptitiously. Yet, just as the initial idealism of Mach and Avenarius is generally acknowledged in philosophical literature, so is it generally acknowledged that subsequently empirio-criticism endeavoured to swing towards materialism. Cauwelaert, the French writer quoted above, asserts that Avenarius’ Prolegomena is “monistic idealism,” The Critique of Pure Experience (1888–90) is “absolute realism,” while The Human Concept of the World (1891) is an attempt “to explain” the change. Let us note that the term realism is here employed as the antithesis of idealism. Following Engels, I use only the term materialism in this sense, and consider it the sole correct terminology, especially since the term “realism” has been bedraggled by the positivists and the other muddleheads who oscillate between materialism and idealism. For the present it will suffice to note that Cauwelaert had the indisputable fact in mind that in the Prolegomena (1876) sensation, according to Avenarius, is the only entity, while “substance"—in accordance with the principle of “the economy of thought"!—is eliminated, and that in the Critique of Pure Experience the physical is taken as the independent series, while the psychical and, consequently, sensations, are taken as the dependent series.
Avenarius’ disciple Rudolf Willy likewise admits that Avenarius was a “complete” idealist in 1876, but subsequently “reconciled” (Ausgleich) “naïve realism” (i.e., the instinctive, unconscious materialist standpoint adopted by humanity, which regards the external world as existing independently of our minds) with this teaching (loc. cit.).
Oskar Ewald, the author of the book Avenarius as the Founder of Empirio-Criticism, says that this philosophy combines contradictory idealist and “realist” (he should have said materialist) elements (not in Mach’s sense, but in the human sense of the term element). For example, “the absolute [method of consideration] would perpetuate naïve realism, the relative would declare exclusive idealism as permanent." Avenarius calls the absolute method of consideration that which corresponds to Mach’s connection of “elements” outside our body, and the relative that which corresponds to Mach’s connection of “elements” dependent on our body.
But of particular interest to us in this respect is the opinion of Wundt, who himself, like the majority of the above mentioned writers, adheres to the confused idealist standpoint, but who has analysed empirio-criticism perhaps more attentively than all the others. p. Yushkevich has the following to say in this connection: “It is interesting to note that Wundt regards empirio-criticism as the most scientific form of the latest type of materialism,” i.e., the type of those materialists who regard the spiritual as a function of corporeal processes (and whom—we would add—Wundt defines as standing midway between Spinozism and absolute materialism ).
True, this opinion of Wundt’s is extremely interesting. But what is even more “interesting” is Mr. Yushkevich’s attitude towards the books and articles on philosophy of which he treats. This is a typical example of the attitude of our Machians to such matters. Gogol’s Petrushka used to read and find it interesting that letters always combined to make words. Mr. Yushkevich read Wundt and found it “interesting” that Wundt accused Avenarius of materialism. If Wundt is wrong, why not refute him? If he is right, why not explain the antithesis between materialism and empirio-criticism? Mr. Yushkevich finds what the idealist Wundt says “interesting,” but this Machian regards it as a waste of effort to endeavour to go to the root of the matter (probably on the principle of “the economy of thought"). . . .
The point is that by informing the reader that Wundt accuses Avenarius of materialism, and by not informing him that Wundt regards some aspects of empirio-criticism as materialism and others as idealism and holds that the connection between the two is artificial, Yushkevich entirely distorted the matter. Either this gentleman absolutely does not understand what he reads, or he was prompted by a desire to indulge in false self-praise with the help of Wundt, as if to say: you see, the official professors regard us, too, as materialists, and not as muddleheads.
The above-mentioned article by Wundt constitutes a large book (more than 300 pages), devoted to a detailed analysis first of the immanentist school, and then of the empirio-criticists. Why did Wundt connect these two schools? Because he considers them closely akin ; and this opinion, which is shared by Mach, Avenarius, Petzoldt and the immanentists is, as we shall see later, entirely correct. Wundt shows in the first part of this article that the immanentists are idealists, subjectivists and adherents of fideism. This, too, as we shall see later, is a perfectly correct opinion, although Wundt expounds it with a superfluous ballast of professorial erudition, with superfluous niceties and reservations, which is to be explained by the fact that Wundt himself is an idealist and fideist. He reproaches the immanentists not because they are idealists and adherents of fideism, but because, in his opinion, they arrive at these great principles by incorrect methods. Further, the second and third parts of Wundt’s article are devoted to empirio-criticism. There he quite definitely points out that very important theoretical propositions of empirio-criticism (e.g., the interpretation of “experience” and the “principal co-ordination,” of which we shall speak later) are identical with those held by the immanentists (die empiriokritische in Uebereinstimmung mit der immanenten Philosophie annimmt, S. 382). Other of Avenarius’ theoretical propositions are borrowed from materialism, and in general empirio-criticism is a “motley” (bunte Mischung, ibid., S. 57), in which the “various component elements are entirely heterogeneous” (an sich einander völlig heterogen sind, S. 56).
Wundt regards Avenarius’ doctrine of the “independent vital series,” in particular, as one of the materialist morsels of the Avenarius-Mach hotchpotch. If you start from the “system C” (that is how Avenarius—who was very fond of making erudite play of new terms—designates the human brain or the nervous system in general), and if the mental is for you a function of the brain, then this “system C” is a “metaphysical substance"—says Wundt (ibid., p. 64), and your doctrine is materialism. It should be said that many idealists and all agnostics (Kantians and Humeans included) call the materialists metaphysicians, because it seems to them that to recognise the existence of an external world independent of the human mind is to transcend the bounds of experience. Of this terminology and its utter incorrectness from the point of view of Marxism, we shall speak in its proper place. Here it is important to note that the recognition of the “independent” series by Avenarius (and also by Mach, who expresses the same idea in different words) is, according to the general opinion of philosophers of various parties, i.e., of various trends in philosophy, an appropriation from materialism. If you assume that everything that exists is sensation, or that bodies are complexes of sensations, you cannot, without violating all your fundamental premises, all “your” philosophy, arrive at the conclusion that the physical exists independently of our minds, and that sensation is a function of matter organised in a definite way. Mach and Avenarius, in their philosophy, combine fundamental idealist premises with individual materialist deductions for the very reason that their theory is an example of that “pauper’s broth of eclecticism” of which Engels speaks with just contempt.
This eclecticism is particularly marked in Mach’s latest philosophical work, Knowledge and Error, 2nd edition, 1906. We have already seen that Mach there declared that “there is no difficulty in constructing every physical element out of sensation, i.e., out of psychical elements,” and in the same book we read: “Dependencies outside the boundary U [ = Umgrenzung, i.e., “the spatial boundary of our body,” S. 8] are physics in the broadest sense” (S. 323, § 4). “To obtain those dependencies in a pure state (rein erhalten) it is necessary as much as possible to eliminate the influence of the observer, that is, of those elements that lie within U” (loc. cit.). Well, well, the titmouse first promised to set the sea on fire. . . i.e., to construct physical elements from psychical elements, and then it turns out that physical elements lie beyond the boundary of psychical elements, “which lie within our body"! A remarkable philosophy!
Another example: “A perfect (vollkommenes) gas, a perfect liquid, a perfect elastic body, does not exist; the physicist knows that his fictions only approximate to the facts and arbitrarily simplify them; he is aware of the divergence, which cannot be eliminated” (S. 418, § 30).
What divergence (Abweichung) is meant here? The divergence of what from what? Of thought (physical theory) from the facts. And what are thoughts, ideas? Ideas are the “tracks of sensations” (S. 9). And what are facts? Facts are “complexes of sensations.” And so, the divergence of the tracks of sensations from complexes of sensations cannot be eliminated.
What does this mean? It means that Mach forgets his own theory and, when treating of various problems of physics, speaks plainly, without idealist twists, i.e., materialistically. All the “complexes of sensations” and the entire stock of Berkeleian wisdom vanish. The physicists’ theory proves to be a reflection of bodies, liquids, gases existing outside us and independently of us, a reflection which is, of course, approximate; but to call this approximation or simplification “arbitrary” is wrong. In fact, sensation is here regarded by Mach just as it is regarded by all science which has not been “purified” by the disciples of Berkeley and Hume, viz., as an image of the external world. Mach’s own theory is subjective idealism; but when the factor of objectivity is required, Mach unceremoniously inserts into his arguments the premises of the contrary, i.e., the materialist, theory of knowledge. Eduard von Hartmann, a consistent idealist and consistent reactionary in philosophy, who sympathises with the Machians’ fight against materialism, comes very close to the truth when he says that Mach’s philosophical position is a “mixture (Nichtunterscheidung) of naïve realism and absolute illusionism”. That is true. The doctrine that bodies are complexes of sensations, etc., is absolute illusionism, i.e., solipsism; for from this standpoint the world is nothing but my illusion. On the other hand, Mach’s afore-mentioned argument, as well as many other of his fragmentary arguments, is what is known as “naïve realism,” i.e., the materialist theory of knowledge unconsciously and instinctively taken over from the scientists.
Avenarius and the professors who follow in his footsteps attempt to disguise this mixture by the theory of the “principal co-ordination.” We shall proceed to examine this theory presently, but let us first finish with the charge that Avenarius is a materialist. Mr. Yushkevich, to whom Wundt’s opinion which he failed to understand seemed so interesting, was either himself not enough interested to learn, or else did not condescend to inform the reader, how Avenarius’ nearest disciples and successors reacted to this charge. Yet this is necessary to clarify the matter if we are interested in the relation of Marx’s philosophy, i.e., materialism, to the philosophy of empirio-criticism. Moreover, if Machism is a muddle, a mixture of materialism and idealism, it is important to know whither this current turned—if we may so express it—after the official idealists began to disown it because of its concessions to materialism.
Wundt was answered, among others, by two of Avenarius’ purest and most orthodox disciples, J. Petzoldt and Fr. Carstanjen. Petzoldt, with haughty resentment, repudiated the charge of materialism, which is so degrading to a German professor, and in support referred to—what do you think?—Avenarius’ Prolegomena, where, supposedly, the concept of substance has been annihilated! A convenient theory, indeed, that can be made to embrace both purely idealist works and arbitrarily assumed materialist premises! Avenarius’ Critique of Pure Experience, of course, does not contradict this teaching, i.e., materialism, writes Petzoldt, but neither does it contradict the directly opposite spiritualist doctrine. An excellent defence! This is exactly what Engels called “a pauper’s broth of eclecticism.” Bogdanov, who refuses to own himself a Machian and who wants to be considered a Marxist (in philosophy), follows Petzoldt. He asserts that “empirio-criticism is not . . . concerned with materialism, or with spiritualism, or with metaphysics in general,” that “truth . . . does not lie in the ‘golden mean’ between the conflicting trends [materialism and spiritualism], but lies out side of both". What appeared to Bogdanov to be truth is, as a matter of fact, confusion, a wavering between materialism and idealism.
Carstanjen, rebutting Wundt, said that he absolutely repudiated this “importation (Unterschiebung) of a materialist element” which is utterly foreign to the critique of pure experience.”. “Empirio-criticism is scepticism χαι εςοχην (pre-eminently) in relation to the content of the concepts.” There is a grain of truth in this insistent emphasis on the neutrality of Machism; the amendment made by Mach and Avenarius to their original idealism amounts to partial concessions to materialism. Instead of the consistent standpoint of Berkeley—the external world is my sensation—we some times get the Humean standpoint—I exclude the question whether or not there is anything beyond my sensations. And this agnostic standpoint inevitably condemns one to vacillate between materialism and idealism.
 Friedrich W. Adler, “Die Entdeckung der Weltelemente (zu E. Machs 70. Geburtstag)” [The Discovery of the World-Elements (On the Occasion of E. Mach’s 70th Birthday)], Der Kampf, 1908, Nr. 5 (Februar). Translated in The International Socialist Review, 1908, No. 10 (April). One of Adler’s articles has been translated into Russian in the symposium Historical Materialism. —Lenin
 Mach says in the Analysis of Sensations: “These elements are usually called sensations. But as that term already implies a one-sided theory, we prefer to speak simply of elements” (pp. 27-28). —Lenin
 “The antithesis between the self and the world, sensation or appearance and the thing, then vanishes, and it all reduces itself to a complex or elements” (ibid., p. 21). —Lenin
 Joseph Petzoldt, Einführung in die Philosophie der reinen Erfahrung [Introduction to the Philosophy of Pure Experience], Bd. I, Leipzig, 1900, S. 113: “Elements are sensations in the ordinary sense of simple, irreducible perceptions (Wahrnehmungen).” —Lenin
 V. Lesevich, What Is Scientific [read: fashionable, professorial, eclectic] Philosophy?, St. Petersburg, 1891, pp. 229, 247. Petzoldt, Bd. II, Leipzig, 1904, S. 329. —Lenin
 Petzoldt, Bd. II, Leipzig, 1904, S. 329. —Lenin
 R. Avenarius, “Bemerkungen zum Begriff des Gegenstandes der Psychologie,” Vierteljahrsschrift für wissenschaftliche Philosophie, Bd. XVIII (1894) und Bd. XIX (1895). —Lenin
 The Fundamental Elements, etc., p. 216; cf. the quotations cited above. —Lenin
 Kritik der reinen Erfahrung.—Ed.
 Oskar Ewald, Richard Avenarius als Begründer des Empiriokritizismus [Richard Avenarius as the Founder of Empirio-Criticism], Berlin, , S. 66. —Lenin
 p. Yushkevich, Materialism and Critical Realism, St. Petersburg, 1908, p. 15. —Lenin
 W. Wundt, “Ueber naiven und kritischen Realismus” [On Naïve and Critical Realism], in Philosophische Studien, Bd. XIII, 1897, S. 334. —Lenin
 THIS FOOTNOTE has been moved into BODY OF DOCUMENT.
 Eduard von Hartmann, Die Weltanschauung der modernen Physik [The World Outlook of Modern Physics], Leipzig, 1902, S. 219. —Lenin
 J. Petzoldt, Einführung in die Philosophie der reinen Erfahrung, Bd. I, S. 351, 352. —Lenin
 Empirio-Monism, Bk. I, 2nd ed., p. 21. —Lenin
 Ibid., p. 93. —Lenin
 Fr. Carstanjen, “Der Empiriokritizismus, zugleich eine Erwiderung auf W. Wundts Aufsätze” [Empirio-Criticism, with a Reply to W. Wundt’s Articles], Vierteljahrsschrift für wissenschaftliche Philosophie, Jahrg. 22 (1898), S. 73 und 213. —Lenin
 Der Kampf (The Struggle—)a monthly magazine, the organ of Austrian Social-Democracy, published in Vienna from 1907 to 1934. it took up an opportunist, Centrist position under the cover of Left phraseology. Among its editors were Otto Bauer, Adolf Braun, Karl Renner, Friedrich Adler and others.
 The International Socialist Review—an American Socialist monthly magazine of a tendency inside the Socialist Party of America, published in Chicago from 1900 to 1918.
 Vierteljahrsschrift für wissenschaftliche Philosophie (Quarterly of Scientific Philosophy)—a magazine of the empirio-criticists (Machists), published in Leipzig from 1877 o 1916 (from 1902 its title was Vierteljahrsschrift für wissenschaftliche Philosophie und Soziologie) (Quarterly of Scientific Philosophy and Sociology). It was founded by Richard Avenarius and published under his editorship until 1896;after 1896 it was edited by Ernst Mach. Contributors included Wilhelm Wundt, Alois Riehl, Wilhelm Schuppe and others.
Lenin’s appraisal of the magazine is given on p.317 of this volume.
 Spinozism—the system of views of the Dutch seventeenth-century materialist philosopher Benedict Spinoza, according to whom all things are manifestations (modes) of a single, universal substance, which is its own cause and identical with “god, or nature”. The essence of substance is expressed in innumerable qualities—attributes, the most important of which are extension and thought. Spinoza regarded causality as a form of the interconnection of the separate phenomena of nature, understanding by it the immediate reciprocal action of bodies whose first cause is substance. The action of all modes of substance, including man, is strictly one of necessity; the notion of accident arises only in consequence of ignorance of the totality of all the acting causes. Since hought is one of the attributes of universal substance, the connection and order of ideas are in principle the same as the order and connection of things, and the possibility of human knowledge of the world is unlimited. For the same reason, of the hree forms of cognition—sensuous, rational and rational-intuitive—-the last is regarded as the most rustworthy, in which “a thing is perceived singly through its essence or through knowledge of its immediate cause” (B. Spinoza, ractatus de intellectus emendatione, et de via, qua optime veram, rerum cognitionem dirigitur). This method enables man both to know his own passions and to become master over them; man’s freedom consists in knowing the necessity of nature and of he passions of his soul.
Spinozism was not only a form of materialism, but also of atheism, since it rejected ideas of god as a supernatural being who had created the world and rules it. At the same time, by identifying god and nature he made a concession to heology. This retreat, as also the mechanical character of Spinoza’s materialism, was due, on the one hand, to the level of knowledge at that epoch and, on the other hand, to the limited progressive nature of the young Dutch bourgeoisie, whose interests were expressed by Spinoza’s philosophy. Subsequently, a sharp ideological struggle, which has continued to the present day, developed round the philosophical legacy of the great Dutch thinker, Idealist philosophy, by taking advantage of the inevitable historical limitations of Spinoza’s views, distorts the materialist essence of Spinozism, which was an important stage in the development of he materialist world out look.
 Philosophische Studien (Philosophical Studies)—a magazine of an idealist tendency devoted primarily to questions of psychology, published by Wilhelm Wundt in Leipzig from 1881 to 1904. From 1905 it was published under the title Psychologische Studien (Psychological Studies).
 Petrushka—a serf domestic servant, one of the characters in N. V. Gogol’s novel Dead Souls; he used to read books by syllables without paying any attention to the meaning, being interested only in the mechanical process of reading.
 See F. Engels, Ludwig Feuerbach and the End of Classical German Philosophy (K. Marx and F, Engels, Selected Works, Volume II, Moscow, 1958, pp. 358-59).