1. Sensations and Complexes of Sensations

The fundamental premises of the theory of knowledge of Mach and Avenarius are frankly, simply and clearly set forth by them in their early philosophical works. To these works we shall now turn, postponing for later exposition an examination of the corrections and emendations subsequently made by these writers.

“The task of science,” wrote Mach in 1872, “can be merely the following: 1. To investigate the laws of the connection between ideas (psychology). – 2. To discover the laws of the connection between sensations (physics). – 3. To explain the laws of the connection between sensations and ideas (psychophysics).”[12] This is quite clear.

The subject of physics is the connection between sensations, and not between things or bodies, whose images our sensations are. And in 1883, in his *Mechanics*, Mach repeats the same thought: “Sensations are not ‘symbols of things.’ Rather is ‘the thing’ a mental symbol for a complex of sensations of relative stability. Not things (bodies), but colours, sounds, pressures, spaces, times (what we ordinarily call sensations) are the true elements of the world.”[13]

We shall speak later of this little word “elements,” which was the fruit of twelve years of “reflection.” At this moment we need only note that Mach here admits *directly* that things or bodies are complexes of sensations, and that he quite distinctly opposes *his* philosophical point of view to the opposite theory, according to which sensations are “symbols” of things (it would be more accurate to say images or reflections of things). This latter theory is *philosophical materialism*. For instance, the materialist Friedrich Engels—the well-known collaborator of Marx and a founder of Marxism—constantly and without exception speaks in his works of things and of their mental images or reflections (*Gedanken-Abbilder*), and it is self-evident that these mental images arise solely from sensations. It would seem that this basic view of the “philosophy of Marxism” should be known to everyone who speaks of it, and especially to everyone who appears in print in the name of this philosophy. But in view of the extraordinary confusion introduced by our Machians, it is necessary to repeat what is generally known. Let us open the first paragraph of *Anti-Dühring* and read: “... things and their mental reflections...”[14] Or the first paragraph of the philosophical section: “Whence does thought obtain these principles?” (we are speaking of the fundamental principles of all knowledge). “From itself? No... The forms of being thought can never derive and deduce from itself, but only from the external world... Principles are not the starting-point of the investigation” (as appears to be the case with Dühring, who wishes to be a materialist but cannot consistently pursue materialism), “but its final result; these principles are not applied to nature and human history, but are abstracted from them; it is not nature and humanity that conform to principles, but, on the contrary, principles are true only in so far as they correspond to nature and history. That is the sole materialist conception of the matter, and Dühring’s opposite conception is an idealist conception, turning the actual relation upside down, constructing the real world out of thoughts...” (ibid., S. 21).{21} And this “sole materialist conception” Engels, we repeat, pursues everywhere and without exception, mercilessly attacking Dühring for the slightest deviation from materialism to idealism. Anyone who reads *Anti-Dühring* and *Ludwig Feuerbach* with the slightest attention will find dozens of instances in which Engels speaks of things and of their images in the human head, in our consciousness, in thought, etc. Engels does not say that sensations or ideas are “symbols” of things, for consistent materialism must here place “images,” pictures or reflections in place of “symbol,” as we shall show in detail in its proper place. But now we are not speaking at all of this or that formulation of materialism, but of the opposition of materialism to idealism, of the difference between the two *fundamental lines* of philosophy. From things to sensations and thought? Or from thought and sensations to things? The first line, i.e., the materialist line, is adhered to by Engels. The second, i.e., the idealist line, is adhered to by Mach. No evasions, no sophisms (of which we shall meet a great many more) can eliminate the clear and indisputable fact that E. Mach’s doctrine of things as complexes of sensations is subjective idealism, a mere rehash of Berkeleianism. If bodies are “complexes of sensations,” as Mach says, or “combinations of sensations,” as Berkeley said, then it inevitably follows that the whole world is but my idea. Starting from such a premise, it is impossible to arrive at the existence of other people besides oneself: it is the purest solipsism. Despite all their denials, Mach, Avenarius, Petzoldt and Co. cannot in fact rid themselves of solipsism without outrageous logical absurdities. To explain still more graphically this fundamental element of the philosophy of Machism, let us cite some additional quotations from Mach’s works. Here is a sample from the *Analysis of Sensations* (Russian translation by Kotlyar, Skirmunt’s edition, Moscow, 1907):

“We have before us a body with a point S. When we touch the point, bring it into contact with our body, we receive a prick. We can see the point without feeling the prick. But when we feel the prick we find the point. Thus, the visible point is a permanent nucleus, while the prick is something accidental, which, according to circumstances, may or may not be connected with the nucleus. With the increasing frequency of analogous phenomena we finally become accustomed to regard all properties of bodies as ‘effects’ emanating from permanent such nuclei and conveyed to our Ego through the medium of our body,—‘effects’ which we call ‘sensations’...” (pp. 20–21.)

In other words: people “become accustomed” to taking the standpoint of materialism, to regarding sensations as the result of the action of bodies, things, nature on our sense-organs. This “habit,” harmful to philosophical idealists (acquired by all mankind and by all natural science!), is extremely displeasing to Mach, and he sets about destroying it:

“... But thereby these nuclei lose all their sensory content, becoming mere abstract symbols....”

The old song, most worthy Herr Professor! This is a verbatim repetition of Berkeley, who said that matter is a mere abstract symbol. But in reality, Ernst Mach goes about naked, for if he does not acknowledge that the “sensory content” is an objective reality existing independently of us, then he is left with a “mere abstract” *Ego*, an *Ego* that must be written with a capital letter and in italics, = “the insane piano which imagines that it alone exists in the world.” If the “sensory content” of our sensations is not the external world, then nothing exists save this naked *Ego* engaged in empty “philosophical” acrobatics. A stupid and fruitless occupation!

“... Then it is true that the world consists solely of our sensations. But then we *know* only our sensations, and the assumption of those nuclei, as also of the interaction between them, the fruit of which are only sensations, proves to be wholly idle and superfluous. Such a view can suit only a half-hearted realism or a half-hearted criticism.”

We have quoted Mach’s entire sixth section of the “Antimetaphysical Remarks” in full. It is a sheer plagiarism of Berkeley. Not a single reflection, not a single gleam of thought, except that “we sense only our sensations.” From this there is but one possible conclusion, namely, that “the world consists solely of *my* sensations.” The word “our” put by Mach instead of “my” is put by him illegitimately. By this one word Mach betrays that very “half-heartedness” of which he accuses others. For if the “assumption” of the external world is “idle,” the assumption that the needle exists independently of me and that an interaction takes place between my body and the point of the needle—if the whole of this assumption is indeed “idle and superfluous,” then first of all the “assumption” of the existence of other people is idle and superfluous. Only *I* exist, and all other people, like the whole external world, fall into the category of idle “nuclei.” To speak of “our” sensations is impossible from this standpoint, and since Mach speaks of them, this merely signifies his flagrant half-heartedness. It proves only that his philosophy is idle and empty words of which the author himself does not believe.

Here is a particularly vivid example of Mach’s half-heartedness and confusion. In §6 of Chapter XI of the same *Analysis of Sensations* we read: “If while I experience sensations I myself or another person could observe my brain with the aid of all possible physical and chemical means, it would be possible to determine with which processes occurring in the organism certain kinds of sensations are connected...” (p. 197.)

Very good! So, then, our sensations are connected with definite processes occurring in the organism in general and in our brain in particular? Yes, Mach quite definitely makes this “assumption”—it would be rather awkward not to make it from the standpoint of natural science. But allow me—is this not the very “assumption” of those “nuclei and the interaction between them” which our philosopher proclaimed to be superfluous and idle? Bodies, we are told, are complexes of sensations; to go beyond that, Mach assures us, to regard sensations as the product of the action of bodies upon our sense-organs, is metaphysics, an idle and superfluous assumption, etc., à la Berkeley. But the brain is a body. Hence the brain too is no more than a complex of sensations. It follows that with the help of a complex of sensations I (and I too am nothing but a complex of sensations) sense complexes of sensations. What charming philosophy! First sensations are declared to be the “true elements of the world” and “original” Berkeleianism built on this—and then the covert importation of the converse view that sensations are connected with definite processes in the organism. Are not these “processes” connected with the metabolism between the “organism” and the external world? Could this metabolism take place if the sensations of the given organism did not give it an objectively correct idea of that external world?

Mach does not put to himself such awkward questions when he mechanically jumbles together scraps of Berkeleianism and the views of natural science, which spontaneously adopts the standpoint of the materialist theory of knowledge.... “Sometimes the question is also asked,” Mach writes in the same section, “whether ‘matter’ (inorganic) also senses”.... This means that there is no question that organic matter senses? This means that sensation is not something primary but one of the properties of matter? Mach skips over all the absurdities of Berkeleianism!... “This question,” he says, “is quite natural if we start from the usual, widespread physical conceptions, according to which matter is the immediate and indubitably given reality on which everything is built, both organic and inorganic”.... Let us note this truly valuable admission of Mach’s, that the usual and widespread *physical* conceptions regard matter as immediate reality, and moreover only *one* variety of this reality (organic matter) possesses the clearly expressed property of sensing.... “For in that case,” Mach continues, “sensation must arise somehow suddenly in the edifice consisting of matter, or it must exist in the foundation, so to speak, of this edifice. From our standpoint this question is fundamentally false. For us matter is not the primary given. Rather are the elements (which in a certain definite sense are called sensations) the primary given”....

Thus, the primary givens are sensations, although they are “connected” only with definite processes in organic matter! And while uttering such nonsense, Mach seems to charge materialism (“the usual, the widespread physical conception”) with not solving the problem of whence sensation “arises.” This is a sample of the “refutations” of materialism by fideists and their hangers-on. Is there any other philosophical point of view that “solves” a problem for the solution of which sufficient data has not yet been collected? Does not Mach himself say in the very same paragraph: “so long as this problem (to solve ‘how far sensation extends in the organic world’) is not settled in any single special case, it is impossible to solve this question”?

The difference between materialism and “Machism” on this question thus amounts to the following. Materialism, in full agreement with natural science, takes matter as the primary given, regarding consciousness, thought, sensation as secondary, since in its clearly expressed form sensation is connected only with the higher forms of matter (organic matter), and “in the foundation of the edifice of matter” one can only *presume* the existence of a faculty akin to sensation. Such, for example, is the assumption of the well-known German naturalist Ernst Haeckel, the English biologist Lloyd Morgan and others, not to mention Diderot’s conjecture, which we have cited above. Machism stands on the opposite, idealist point of view and at once lands itself in an absurdity, since, in the first place, sensation is taken as primary *in spite of* the fact that it is connected only with definite processes in matter organised in a definite way; and, in the second place, the fundamental premise that bodies are complexes of sensations is violated by the assumption of the existence of other living beings and in general of other “complexes” besides the given great *Ego*.

The little word “element,” which many naive people accept (as we shall see) as something new and some kind of discovery, actually only confuses the issue with a meaningless term, creating a false impression that some solution or step forward has been achieved. This impression is false, for there still remains to be further investigated how matter, which supposedly does not sense at all, is connected with matter which, though composed of the same atoms (or electrons), yet at the same time possesses a clearly expressed capacity of sensation. Materialism clearly formulates the as yet unsolved problem and thereby stimulates the endeavour to solve it, stimulates further experimental investigation. Machism, i.e., a species of muddled idealism, befouls the issue and diverts it from the correct path by means of the empty verbal twist “element.”

Here is a passage in the last, the summary and concluding, philosophical work of Mach, which shows the entire falsity of this idealist twist. In *Knowledge and Error* we read: “Whereas there is no difficulty in constructing (*aufzubauen*) every physical element out of sensations, i.e., psychical elements, it is impossible to conceive (*ist keine Möglichkeit abzusehen*) how any psychical experience could be represented (*darstellen*) out of the elements employed by modern physics, i.e., out of masses and motions (in that rigidity—*Starrheit*—of these elements which is convenient only for this special science).”[15]

Engels speaks with the utmost definiteness on more than one occasion of the *rigidity of concepts* on the part of many modern natural scientists, of their metaphysical (in the Marxist sense of the word, i.e., anti-dialectical) views. We shall see later that it is precisely on this point that Mach went astray, either failing to understand or not knowing the relation between relativism and dialectics. But at the moment that is not what we are discussing. What is important for us to note here is how palpably the idealism of Mach emerges despite the muddled, supposedly new, terminology. There is, you see, no difficulty in constructing any physical element out of sensations, i.e., psychical elements! Oh yes, such constructions are, of course, easy, for they are purely verbal constructions, empty scholasticism serving as a loophole for fideism. No wonder, then, that Mach dedicates his works to the immanentists, that the immanentists, i.e., the advocates of the most reactionary philosophical idealism, throw themselves on Mach’s neck. Ernst Mach’s “newest positivism” is only about two hundred years too late: Berkeley already showed that “from sensations, i.e., psychical elements,” nothing but solipsism can be “constructed.” As regards materialism, to which Mach here too opposes his views, without mentioning the “enemy” directly and clearly, we already saw, by the example of Diderot, the real views of the materialists. These views do not consist in deducing sensation from the movement of matter or reducing it to the movement of matter, but in recognising sensation as *one of the properties of matter in motion*. Engels, on this question, stood on the same standpoint as Diderot. Engels dissociated himself from the “vulgar” materialists Vogt, Büchner and Moleschott, among other things, precisely because they strayed into the view that the brain secretes thought *in the same way as* the liver secretes bile. But Mach, who constantly opposes his views to materialism, naturally ignores all the great materialists—Diderot and Feuerbach and Marx and Engels—just as all the other official professors of official philosophy do.

It would indeed be ridiculous to deny the idealism of Avenarius’ *Prolegomena*, when he says there directly that “only sensation can be thought of as existing” (pp. 10 and 65 of the second German edition; the italics in the quotations are everywhere ours). So Avenarius himself expounds the content of §116 of his work. Here is that section in full: “We have recognised that that which exists (or: the existent, *das Seiende*) is substance endowed with sensation; substance falls away...” (“it is more economical,” you see, “less expenditure of force,” to think that there is “no substance” and that no external world exists!) “... sensation remains: the existent must therefore be thought of as sensation, at the basis of which there is no longer anything foreign to sensation” (*nichts Empfindungsloses*).

Thus, sensation exists without “substance,” i.e., thought exists without brain! Are there indeed philosophers capable of defending this brainless philosophy? There are. Among them is Professor Richard Avenarius. And we cannot but pause for a moment over this defence, difficult as it is for a healthy person to take it seriously. Here is Avenarius’ argument in §§89-90 of the same work:

“... The proposition that motion produces sensation is based on apparent experience only. This experience, of which perception is a separate act, consists, supposedly, in the fact that sensation is generated in a certain kind of substance (brain) as a result of transmitted motion (stimuli) and with the assistance of other material conditions (e.g., blood). However—apart from the fact that this generation has never been directly (*selbst*) observed—in order to construct the supposed experience as an experience which in all its parts is a real experience, at least empirical proof must be forthcoming that the sensation which is supposedly engendered in a certain substance by means of transmitted motion did not already exist in this substance in some manner or other; so that the appearance of sensation cannot be understood otherwise than as produced by an act of creation on the part of the transmitted motion. Thus, only by the proof that where sensation now appears there was previously no sensation, not even a minimal one, only by this proof could a fact be established which, signifying some act of creation, contradicts all the rest of experience and fundamentally changes all the rest of the conception of nature (*Naturanschauung*). But no experience furnishes such proof, and none can ever furnish it; on the contrary, the absolutely non-sensational state of the substance which subsequently senses is only a hypothesis. And this hypothesis complicates and befogs our cognition instead of simplifying and clarifying it.

“If the so-called experience, that by means of transmitted motion sensation arises in a substance which begins to sense from this moment, proved on closer examination to be only apparent, then perhaps in the remaining content of experience there is still enough material to establish at least the relative origin of sensation from conditions of motion, namely, to establish that the sensation which is present, but which is latent or minimal, or for other reasons not accessible to our consciousness, is, by virtue of the transmitted motion, released or raised, or becomes conscious. However, this bit of remaining content of experience, too, is only an appearance. If by means of ideal observation we trace the motion proceeding from the moving substance A and transmitted through a series of intermediate centres to the sensation-endowed substance B, we shall find, at best, that sensation in substance B develops or is enhanced simultaneously with the reception of the arriving motion, but we shall not find that this occurred *in consequence* of the motion....”

We have deliberately quoted this refutation of materialism by Avenarius in full, so that the reader may see what truly pitiful sophisms the “newest” empirio-critical philosophy operates with. Let us compare Avenarius’ idealist argument with the materialist argument of ... Bogdanov, if only to punish him for having betrayed materialism!

Long, long ago, a whole nine years ago, when Bogdanov was half a “natural-historical materialist” (i.e., an adherent of the materialist theory of knowledge on which the overwhelming majority of present-day natural scientists spontaneously stand), when Bogdanov was only half led astray by the muddle-headed Ostwald, he wrote: “From ancient times to the present day, descriptive psychology has maintained the division of facts of consciousness into three groups: the area of sensations and ideas, the area of feeling, the area of impulses.... The first group includes *images* of phenomena of the external or internal world, taken in consciousness by themselves.... Such an image is called a ‘sensation’ if it is directly evoked through the organs of external sense by a corresponding external phenomenon.”[19] A little later: “sensation... arises in consciousness as the result of some impulse from the external environment, transmitted through the organs of external sense” (222). Or again: “Sensations form the foundation of the life of consciousness, its immediate connection with the external world” (240). “At every step in the process of sensation a transformation of the energy of external stimulus into a fact of consciousness takes place” (133). And even in 1905, when Bogdanov, with the benevolent assistance of Ostwald and Mach, had succeeded in passing from the materialist standpoint in philosophy to the idealist one, he wrote (from forgetfulness!) in *Empirio-Monism*: “As is well known, the energy of external irritation, transformed in the terminal nervous apparatus into an as yet insufficiently studied but free of all mysticism, ‘telegraphic’ form of nerve current, reaches first of all the neurons situated in the so-called ‘lower’ centres—ganglionic, spinal, subcortical” (Book I, 2nd ed., 1905, p. 118).

For every natural scientist not led astray by professorial philosophy, as for every materialist, sensation is indeed the direct connection of consciousness with the external world; it is the transformation of the energy of external stimulus into a fact of consciousness. Every human being has observed this transformation millions of times and does observe it actually at every step. The sophism of idealist philosophy consists in regarding sensation not as the connection of consciousness with the external world, but as a partition, a wall, separating consciousness from the external world—not as an image of the external phenomenon corresponding to the sensation, but as the “sole existent.” Avenarius only gave a slightly altered form to this old sophism, which had been worn threadbare by Bishop Berkeley. Since we do not yet know all the conditions of the connection of sensation with matter organised in a definite way, which we observe every minute, let us therefore recognise sensation alone as existing—that is what Avenarius’ sophism boils down to.

In order to conclude with a characterisation of the fundamental idealist premises of empirio-criticism, let us briefly mention the English and French representatives of this philosophical trend. Of the Englishman Karl Pearson, Mach says outright that he “agrees with his epistemological (*erkenntniskritischen*) views in all essential points” (*Mechanics*, cited ed., p. IX). K. Pearson, for his part, expresses his agreement with Mach.[20] For Pearson the “real things” are “sense impressions.” Pearson proclaims any recognition of things beyond the boundaries of sense impressions to be metaphysics. He battles against materialism (not knowing either Feuerbach or Marx-Engels) in the most resolute manner—the arguments do not differ from those analysed above. But Pearson is so utterly devoid of any desire to imitate materialism (a speciality of the Russian Machians), Pearson is so ... careless that, without inventing “new” labels for his philosophy, he simply declares both his and Mach’s views to be “idealist” (p. 326 of the cited ed.)! He traces his genealogy directly from Berkeley and Hume. Pearson’s philosophy, as we shall see repeatedly below, is distinguished by far greater integrity and consistency than the philosophy of Mach.

With the French physicists P. Duhem and Henri Poincaré, Mach specially expresses his solidarity.[21] We shall have to deal with the philosophical views of these writers, which are particularly confused and inconsistent, in the chapter on the new physics. Here it is sufficient to note that for Poincaré things are “groups of sensations”[22] and that Duhem too incidentally expresses a similar view.[23]

Let us now turn to the question of how Mach and Avenarius, having realised the idealist character of their original views, *corrected* them in their subsequent works.

2. “The Discovery of the World-Elements”

Under this title a privat-docent of the University of Zurich, Friedrich Adler, writes about Mach, probably the only German writer who also wishes to supplement Marx with Machism.[24] And justice must be done to this naive privat-docent that in his simple-mindedness he does Machism a disservice. At least the question is put clearly and sharply: did Mach really “discover the world-elements”? In that case, of course, only extremely antiquated and ignorant people can still remain materialists. Or is this discovery a return of Mach to old philosophical errors?

We have seen that in 1872 Mach and in 1876 Avenarius stood on a purely idealist point of view; for them the world is our sensation. In 1883 Mach’s *Mechanics* appeared, and in the preface to the first edition Mach refers precisely to Avenarius’ *Prolegomena*, greeting the “extremely close” (*sehr verwandte*) thoughts to his own philosophy. Here is the passage on the elements in this *Mechanics*: “The whole of natural science can only picture (*nachbilden und vorbilden*) complexes of those *elements* which we ordinarily call *sensations*. It is a matter of the connection of these elements. The connection between A (heat) and B (fire) belongs to physics, the connection between A and N (nerves) belongs to physiology. Neither connection exists *separately*; both exist *together*. Only temporarily can we abstract from the one or the other. Even apparently purely mechanical processes are therefore always physiological as well” (S. 499 of the cited German edition). The same in the *Analysis of Sensations*: “... Wherever, in addition to the expressions: ‘element,’ ‘complex of elements,’ or instead of them, the designations: ‘sensation,’ ‘complex of sensations’ are used, it must always be borne in mind that elements are sensations *only in this connection*” (namely, the connection of A, B, C with K, L, M, i.e., the connection of “complexes which are ordinarily called bodies,” with “the complex which we call our body”), “in this respect, in this functional dependence. In another functional dependence they are at the same time physical objects” (Russian translation, pp. 23 and 17). “A colour is a physical object if we consider, for example, its dependence on the source of light illuminating it (other colours, heat, space, etc.). But if we consider its dependence on the retina (the elements K, L, M...), we have before us a psychological object, a *sensation*” (ibid., p. 24).

Thus, the discovery of the world-elements consists in the following:

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 nerves of man and in general on the human organism; the former does not depend;
4) the connection of physical and the connection of psychical elements is declared not to exist separately one from the other; they exist only together;
5) only temporarily can one abstract from the one or the other connection;
6) the “new” theory is declared to be free from “one-sidedness.”[25]

Truly, one-sidedness is absent here, but what is present is the most incoherent jumbling together of opposite philosophical standpoints. Since you start only from sensations, you do not by means of the little word “element” correct the “one-sidedness” of your idealism, but only confuse the issue, cravenly hiding from your own theory. In words you eliminate the opposition between the physical and the psychical,[26] between materialism (which takes nature, matter as primary) and idealism (which takes spirit, consciousness, sensation as primary)—in fact you immediately restore this opposition, restore it stealthily, retreating from your fundamental premise! For if elements are sensations, you are not entitled to accept for a single second the existence of “elements” *independently* of my nerves, of my consciousness. But as soon as you admit such physical objects independent of my nerves, of my sensations, which give rise to sensation only by acting upon my retina, you shamefully abandon your “one-sided” idealism and pass to the standpoint of “one-sided” materialism! If colour is a sensation only depending on the retina (as natural science compels you to admit), then light rays, falling upon the retina, produce the sensation of colour. That is to say, outside us, independently of us and of our consciousness, there exists a movement of matter, say, ether waves of a definite length and a definite velocity, which, acting on the retina, produce in man the sensation of one or another colour. This is how natural science looks at it. It explains the different sensations of one or another colour by the different length of light waves existing outside the human retina, outside man and independently of him. This is materialism: matter, acting on 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 highest 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 little word “element,” which supposedly frees their theory from the “one-sidedness” of subjective idealism, supposedly permits the assumption that the psychical depends on the retina, nerves, etc., 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 sophism, for a materialist, on reading Mach and Avenarius, will at once pose the question: what are “elements”? It would indeed be childish to think that the creation of a new little word can eliminate the fundamental philosophical trends. Either the “element” is a sensation, as all empirio-critics, Mach, Avenarius, Petzoldt,[27] etc., say—in which case your philosophy, gentlemen, is *idealism*, vainly striving to cover the nakedness of its solipsism with the garb of a more “objective” terminology. Or the “element” is not a sensation—in which case no thought whatever is attached to your “new” little word; it is just an empty pompousness.

Take, for example, Petzoldt—the last word of empirio-criticism, according to the characterisation of the first and greatest Russian empirio-critic, V. Lesevich.[28] Having defined elements as sensations, he declares in the second volume of the work mentioned: “We must be careful that in the proposition: ‘sensations are the elements of the world’ we do not take the word ‘sensation’ as denoting something only subjective and therefore airy, reducing to illusion (*verflüchtigendes*) the ordinary picture of the world.”[29]

The tongue ever turns to the aching tooth! Petzoldt feels that the world “evaporates” (*verflüchtigt sich*) or turns into an illusion if the elements of the world are held to be sensations. And good Petzoldt thinks to help matters by means of a proviso: we must not take sensation for something merely subjective! Is not this a ridiculous sophism? Does the matter change because we “take” sensation as sensation or try to stretch the meaning of this word? Does the fact that sensations are connected in man with normally functioning nerves, retina, brain, etc., disappear from this? That the external world exists independently of our sensation? If you do not want to get off with evasions, if you seriously want to “be careful” of subjectivism and solipsism, you must first