[Reading Guide] Materialism and Empirio-criticism

We are proud to provide the following reading guide for Lenin's classic philosophical text, Materialism and Empirio-Criticism. Published in 1909, during the period of black reaction following the defeat of the 1905 Russian Revolution, the book mounts an uncompromising defence of philosophical materialism.

Lenin provides a decisive rebuttal to the subjective-idealist and Neo-Kantian ideas infecting the Russian Social Democracy at the time, which persist in essence through the postmodern thought influential in academia and parts of the labour movement today. We must continue to combat these reactionary ideas, which deny objective reality, progress and the importance of class struggle. As such, this book remains just as essential now as when it was written. This guide contains chapter summaries and study questions to help both individual readers and Marxist study circles get the most out of the text, which can be purchased here from Wellred Books.


  1. The Theory of Knowledge of Empirio-Criticism and of Dialectical Materialism (I)
  2. The Theory of Knowledge of Empirio-Criticism and of Dialectical Materialism (II)
  3. The Theory of Knowledge of Dialectical Materialism and Empirio-Criticism (III)
  4. The Philosophical Idealists as Comrades-in-arms and Successors of Empirio-Criticism
  5. The Recent Revolution in Natural Science and Philosophical Idealism
  6. Empirio-Criticism and Historical Materialism

The Theory of Knowledge of Empirio-Criticism and of Dialectical Materialism (I)

“Machism is a muddle” Lenin remarks, revealing in this chapter the confused and inconsistent mix of ideas that make up Mach and the Empiriocritics. Showing the fundamentally subjective idealist basis of their philosophy, borrowed wholesale from Berkeley, Lenin exposes how Mach, Avenarius and others blur the distinction between Idealism and Materialism.

In adopting the term ‘elements’ to describe sensations, Mach performs a “futile verbal trick” to dodge the problem of whether matter or consciousness are primary. Declining to address this problem, the result for the Empiriocritics is a “pauper’s broth of eclecticism”: conceding the materialist conception of the dependence of thought upon matter, in the guise of ‘independent series’, ‘principal co-ordination’ etc, while continuing to assert that all that really exists is subjective thought independent of matter.

As well as claiming to have found “the truth transcending materialism and idealism”, the Machians attempt to reconcile their theories with materialist natural science, by trying to explain how the world could have existed before humans and whether thought is dependent upon the brain. These questions divide the Machians, who avoid the materialist explanations of these problems in absurd ways.

Either as a result of the “muddle” that Mach, Avenarius, Bazarov etc have got themselves in, or out of ignorance, the Empiriocritics pretend to launch an attack on ‘idealism’, but do so in a way that just goes to prove their own subjective idealism. The Russian Machians attack Plekhanov in this manner (who defends materialism), “a literary indecency” deliberately avoiding the great works of philosophical materialists like Marx, Engels and Feuerbach. Confronting these works would not allow the Machians to pretend their idealist philosophy can be reconciled with the materialist basis of Marxism.

Study Questions:

  1. What is the similarity between the ‘agnosticism’ of Hume and Kant, and the later theories of Mach and Avenarius?
  2. In what way do the Machian ‘elements’ and ‘principle coordination’ undermine Mach’s own theory of reality?
  3. Why does Lenin accuse Mach of “building a loophole for fideism” in his philosophy?
  4. How do the Machians attempt to reconcile their theories with natural science?
  5. In what ways does Lenin show that Mach’s ideas are subjective idealism, and that they must inevitably end in solipsism?

The Theory of Knowledge of Empirio-Criticism and of Dialectical Materialism (II)

In this chapter Lenin discusses the Empirio Critics’ denial of the knowability of the ‘thing-in-itself’, one of the most fundamental questions of modern philosophy. As usual, the Machians treatment of this question is characterised by confusion and a dishonest representation of the materialist, Marxist position, especially that of Engels. Their dishonesty is particularly clear when the school’s supposed Marxists feel obliged to pass over Engels’ position in silence, whilst the explicitly anti-Marxist members of the school, like Chernov, openly attack him. Instead, the ‘Marxists’ make the same points as Chernov, only they direct them at the easier target of Plekhanov.

Lenin shows how Engels refutes the Kantian idea that we cannot know the ‘thing in itself’, because we are able to apply our ideas about objects to the world around us, recreating these objects out of our own activity. The point Engels is making is that we are not passive observers of some mysterious, alien thing, instead we are active participants in the same objective world.

Importantly, Lenin clarifies that Engels is not refuting or denying the existence of the ‘thing in itself’, but the Kantian idea that the ‘thing in itself’ is unknowable. The attempt of the empirio critics to make materialism out to be ‘metaphysical’ and dogmatic, lies in this confusion, because they think materialism means to say that there is no ‘thing in itself’ since nothing is unknown to us, as if materialists think there is nothing outside of knowledge. As Lenin points out, of course many things are outside knowledge, are unknown, but they are not in principle unknowable: “There is definitely no difference in principle between the phenomenon and the thing-in-itself, and there can be no such difference. The only difference is between what is known and what is not yet known.”

This is the key point about subjective idealism: as Lenin shows, Hume and Kant both “in principle fence off “the appearance” from that which appears, the perception from that which is perceived, the thing-for-us from the “thing-in-itself.”” They start out from the assumption of the fundamental difference between thought and being, and that thought can never ever know what is outside itself.

Lenin states very clearly that the decisive question of materialism is not the extent to which our sense perceptions are correct, or how frequently they are misleading, but is the insistence that it is an independent material world which acts upon our senses. Reality cannot ‘coincide’ with sense perceptions, as that makes reality dependent on perception. Reality is not dependent upon our perception of it.

Lenin also quotes Feuerbach to show that the independence of the material world from perception means that our ideas of things are distinct from the things themselves. Feuerbach gives the example of saltiness, which is distinct from that which is salty. Saltiness is the effect certain objects have upon the perceiving person. This does not contradict materialism, because as Feuerbach points out, thinking beings are part of nature, but not equal or identical to nature as a whole, or other parts of nature. The subjective feeling we have from external objects is therefore something distinct from the objects themselves, but is indispensable for helping us to know the nature of that object. The feeling of seeing redness is not the same thing as the wavelength of red photons, rather it is produced by red photons interacting with one’s nervous system. The taste of saltiness, and the perception of redness, help us to identify the real nature of the thing that is salty or red.

Lenin also ridicules their vague idea that truth is an ‘organising form of human experience’. He points out that this would mean one cannot say there are any objective truths independent of humanity, and it abolishes all criteria for truth - Catholicism, or any other widely held view that ‘organises human experience’, would then be true.

As Lenin later says “Knowledge can be useful biologically, useful in human practice, useful for the preservation of life, for the preservation of the species, only when it reflects objective truth, truth which is independent of man.”

What is notable about this ‘verbal jugglery’ is that it is a contortion they are obliged to perform in order to inject objectivity into their theory. No theory can do without the notion that some ideas are true, and others false, otherwise the theory itself would be pointless. But they cannot admit that only the independent existence of objective reality is what confers truth to different viewpoints. Without this, the empirio-critics ludicrously argue that only some organising forms of experience count as collective, and therefore true.

Lenin also quotes Engels’ brilliant dialectical treatment of eternal truths, showing the dialectical contradiction that absolute truth is realised through a succession of relative errors. The partially true ideas of limited, concrete individuals are what produce, over time, deeper and truer knowledge. But undialectical, or absolute relativists such as the empirio-critics, cannot transition from the existence of relative errors, to truth. For them, there is only absolute, timeless truth, or all things are purely subjective.

Finally, Lenin quotes Shulze’s ridiculous, but typical, insistence that his scepticism has no practical significance, and that practical application of ideas is something only suitable ‘for the mob’. As Feuerbach correctly replies, “a speculation which contradicts life, which makes the standpoint of death, of a soul separated from the body, the standpoint of truth, is a dead and false speculation”.

Study Questions:

  1. How does Engels explain the materialist understanding of the ‘thing-in-itself’? How is this used to refute the accusations of Chernov?
  2. How does the position of the agnostics, that Engels’ outlines, differ from Mach? And how does it further differ from materialism?
  3. What more can we learn about agnosticism from Lenin’s analysis of Engels?
  4. How can the materialism of Feuerbach be used to refute the assertions by the Machians against Marx and Engels?
  5. Why do Dietzgen and Feuerbach dispute any ‘fundamental’ difference between the thing-in-itself and the phenomenon?
  6. Why does Lenin say that Bogdanov confuses the question of whether objective truth exists?
  7. Does objectivity lie in collective experience? If ideas that ‘organise human experience’ such as organised religion create truth, then what determines these ideas’ ability to ‘organise human experience’, but other ideas not?
  8. Why do these philosophers who stand against fideism end up falling into this very trap?
  9. Are materialists dogmatists? If not, why?
  10. What is the relationship between relative and absolute truth?
  11. Are science and the theory of knowledge linked?
  12. What does the admission by Schulze that practical application of ideas is only ‘for the mob’ and that his ideas only have relevance ‘in theory’, tell us about this whole school of philosophy?

The Theory of Knowledge of Dialectical Materialism and Empirio-Criticism (III)

This chapter delves into the question of matter and experience, covering how the Machians conceive of matter, and the language they use to obfuscate the issue. Their arguments demonstrate their understanding of the relationship of thinking and being, as they question whether any definition of matter can be truly materialist. For them, such a definition of matter as physical, as independent of subjective experience, is ‘only an abstraction’, a ‘complete chimera’. Instead, matter might exist, but it is defined as dependent on or merely part of experience, or as ‘a certain systematic combination of the elements (sensations).’ Once again, Lenin then exposes the Machians’ verbal jugglery, the vague terms that imply some new advance in philosophy, but which in reality just masks the same old subjective idealism.

The relationship between thinking and being is further questioned in relation to ‘experience.’ Understanding what experience is, is an important marker between materialism and idealism. The Machians, starting from an idealist stand point, conceive of experience as entirely subjective, thus inhibiting our ability to truly understand the objective world. As Lenin says, their ‘definition’ boils down to ‘experience is experience’, which, as Lenin points out earlier in the chapter, is not a definition, since to define means to bring a concept within a more comprehensive concept. Their ‘definition’ is what is known as a tautology, one of the most basic errors of philosophy.

This thought process is replicated on the question of causality, in which it is argued that we impose onto nature what we think, with language. As with the rest of the book, the fundamental question of why we have these particular thoughts (or language) remains unanswered by the Machians, and Lenin reaffirms the materialist answer: the objective world exists, and it is through objective reality that human beings understand and experience the world.

Study Questions:

  1. The Machians ask for a definition of matter that is truly materialist. They seem to think this can't be. Why is this? Why can't the Machians accept the materialist definition of matter?
  2. When talking about ‘experience’, Mach says we mustn’t philosophise out of ourselves. Why is this ironic?
  3. Does man give law to nature, or does nature give law to man? How can we understand this using a dialectical understanding of cause and effect?
  4. What is the difference between Engels & Mach’s approach to understanding freedom & necessity?

The Philosophical Idealists as Comrades-in-arms and Successors of Empirio-Criticism

In this chapter, Lenin sets out to examine the historical development of Empirio-Criticism, and its connection and relation to other philosophical trends, in particular Kantianism. Lenin first addresses the relationship of Mach and Avenarius to Kant, and in the first section he looks at criticism from the ‘left’ and the ‘right’. It is important to note that Mach and Avenarius started with Kant in their philosophical development, but branched away for several reasons.

Mach, having begun with Kant, claims he strayed more towards Berkely and Hume; he deemed them to be more consistent than Kant.

Likewise, Avenarius was very critical of Kant, and he claimed that Kant hadn’t sufficiently ‘purified experience’. Avenarius therefore tries to rid the Kantian doctrine firstly of a priorism, and secondly of the ‘thing-in-itself’, i.e. the assumption of matter. In his opinion, this “is not given in the stuff of actual experience, but is imported into thought”.

In other words, it was an attempt to ‘purify experience’ of any tending towards materialism. Lenin goes on to explain that Kant wavered between idealism and materialism, which is significant for understanding the difference between a materialist and idealist response to Kant.

However, Avenarius claimed to be the first to ‘purify experience’, yet this isn’t the case. In fact, the development of German classical philosophy after Kant gave rise to a criticism of Kantianism on the same lines as Avenarius. This was represented by Schulze, an adherent of Humean Agnosticism, and J. G. Fichte, an adherent of Berkleianism, i.e. subjective idealism.

Avenarius was therefore mistaken in thinking that by purifying experience in the Kantian doctrine he was somehow giving rise to a new trend in philosophy, when he was in reality continuing the line of Hume and Berkley, Schulze and Fichte.

In reality, he was only purifying Kantianism of agnosticism. He actually fought not against agnosticism (the denial of objective reality given in sensation), but for a purer agnosticism. i.e. one rid of the thing-in-itself (albeit unknowable) and of necessity and causality. He therefore fought Kant not from the left, like a materialist, but from the right, like the sceptics and idealists.

Lenin then moves on to a critique of Schulze and Fichte and the way in which they criticised Kant. The former criticised Kant for the same recognition of a priorism and the ‘thing-in-itself’, claiming that the latter is “beyond the bounds of all experience”. Ultimately, Schulze rejects Kant’s doctrine of the ‘thing-in-itself’ as an inconsistent concession to materialism, and critiques Kant on the grounds that his assumption of the ‘thing-in-itself’ contradicts agnosticism and leads to materialism.

Fichte, on the other hand, argues that the thing-in-itself is realism, and that Kant makes no distinction between idealism and realism. In particular, he sees an inconsistency in the assumption that the thing-in-itself is the basis of objective reality, as this is in contradiction to critical idealism.

The way in which the Machians take aim at Kant reveals a glaring error in their understanding of Kant and the whole course of the development of German classical philosophy. Lenin reveals this and crucially explains the key difference between an idealist and materialist critique of these ideas.

Lenin explains that Kant wavers between materialism and idealism: when he assumes something outside of us, i.e. the ‘thing-in-itself’, he is a materialist; but when he says the ‘thing-in-itself’ is unknowable, transcendental, other-sided, he is an idealist. While the materialists blamed Kant for his idealism, the agnostics and idealists blamed Kant for his assumption of the ‘thing-in-itself’ as a concession to materialism.

For example, Feuerbach reproaches Kant not for his realism, but for his idealism and describes his system as “idealism based on empiricism”. Meanwhile, Engels rebuked Kant for being an agnostic.

Further to this, as regards the empirio-symbolist Yushkevich and the empirio-criticist Chernov, Lenin explains the admixtures of the different strands of philosophy and how we as Marxists should combat them.

In the third section, Lenin turns his attention to the immanentist school, and its relation to Empirio-Criticism. First we see a contradiction in Mach’s thinking about the school: he firstly claims that there are very few scientists who are followers of the supposedly ‘new’, but in reality old Humean-Berkeliean philosophy; and secondly, that this ‘new’ philosophy is part of a broad current in which the immanentists are on the same page as the empirio-criticists and positivists. The contradiction arises in Mach’s admission that this is an old philosophy, but also new - it reveals the innate desire of the Machians to ‘redesign’ old philosophies into ‘new trends’, by simply tweaking or adding a few novel words.

The immanentists and their co-thinkers greet the Machian philosophy warmly, but the same cannot be said for the Russian Machians: for example, Bazarov refers to “certain representatives of the immanentist school” as “realists”, Valentinov meanwhile accuses them of solipsism. While critical, the Machians refrain from calling out the immanentists for the reactionaries they indeed are. In reality, there is no fundamental difference between the empiro-criticists and immanentists.

Finally, Lenin looks to the development of Machism after Mach and Avenarius, to examine in what direction the philosophy developed. By pinning down in what direction it is heading Lenin is able to address the question of what the real essence of this philosophy is. By looking at the works of various descendents of Machism, Lenin shows that these ‘disciples’ were going in the direction of idealism, which in reality, is in no stark contrast to Mach and Avenarius, despite their best attempts to conceal it.

Study Questions:

  1. Avenarius critiques Kant for not having sufficiently 'purified experience', and takes up this task. Was Avenarius' 'new trend' in philosophy a success?
  2. The Machians claimed that Plekhanov was trying to reconcile Engels with Kant (with a thing-in-itself that is somewhat knowable). Why is this a mistake on the part of the Machians?
  3. The Machians took a reactionary line in philosophy, choosing to criticise Kant from the standpoint of Hume and Berkely. In contrast, Feuerbach, Marx, and Engels turned from Kant to the left, in complete rejection of all idealism and of all agnosticism. What does it mean to critique from the left?
  4. Lenin takes up a critique of the immanentist school of philosophy. What is the relation between Empirio-Criticism and the immanentists?
  5. Petzoldt rejected Ziehen (a descendent of Mach) as an idealist, as well as Cornelius, Kleinpeter, and Verworn. Why is it ironic for the successors of Empirio-Criticism to be labelled 'idealists'? How do they differ from Mach and Avenarius?

The Recent Revolution in Natural Science and Philosophical Idealism

Lenin quotes Engels early in the chapter that materialism has to change its form with each epoch making discovery in the field of science, and explains that this does not mean materialism’s fundamental principles should be revised, but that the specific form it takes must be updated as science develops.

Poincare is quoted to show that physics is in serious crisis. We can see how this crisis is leading to subjective idealist conclusions, leading Poincare to say that we impose onto nature concepts like space and time, and that whatever is not thought, is pure nothing.

Lenin quotes Abel Rey who declares that this confusion, this crisis in science, has led many to conclude that science is simply a system of convenient symbols, referring to nothing but its own closed system of man-made signs. He then says that this means many will conclude the only path to knowledge we have left, is that of intuition of a mystical reality. This refers to the trend of irrationalism, which would become very powerful, even dominant, throughout 20th Century philosophy. The idea that ‘signs’ have superseded and even destroyed ‘the signified’ was very common to postmodernism, for example. Of course, all these viewpoints are subject to the same fatal flaw: if science is no more than convenient signs, what determines their degree of convenience?

Lenin explains that advances in science do not explode materialism, because dialectical materialism does not hold that the hitherto recognised elements are immutable, but in fact holds that matter is inexhaustible, infinite, and thus our understanding of it is always developing. Hence, the crisis in science has thrown it into subjective idealism because of the mechanical materialism most scientists subscribed to.

The Machians believe they have a natural connection to the most modern theories in science, quoting approvingly from a new trend among scientists: the ‘physical idealist’ trend. Lenin identifies this as a reactionary, and not a progressive phenomenon.

Born out of new discoveries about atomic particles, and the refutation of old theories, the physical idealists declare that ‘matter has disappeared’. They substitute ‘forces’ for matter as the fundamental fabric of the universe, an idea Lenin calls “force without substance”. This is compared to the idealist conception of sensation without an objective/external cause.

With reference to the philosophers Cohen and Hartmann, Lenin shows the connection between this ‘physical idealist’ scientific trend and reactionary philosophical idealist conclusions. Following from a denial of matter, they argue science must reject the idea of an objective reality altogether, and cease trying to identify and describe natural laws.

Without an objective reality to study, or laws of necessity to be discovered, the objectivity of science itself is thrown into doubt. Philosophers and scientists are forced to confront this, with some saying that scientific theories must just be subjective. Others try to resolve this problem by acknowledging science as a ‘useful’ method, if not objectively true, or taking refuge in an inconsistent materialist standpoint.

None of the answers offered up by the idealist philosophers or the physical idealists can overcome this problem of objectivity that an idealist worldview creates. Far from being an advance in science, as the Machians wish to believe, the physical idealist trend is a backwards one.

Study Questions:

  1. Why should materialism’s form be changed with new scientific discoveries? How can this be done without changing its essence?
  2. Why do those who subscribe to mechanical materialism tend to collapse into subjective idealism when scientific theories get superseded by new ones?
  3. What is the “mathematical spirit” and how did it affect physics?
  4. Why does Lenin call the crisis/new trend in physics a “wavering of mind” among scientists?
  5. Why does Lenin say that the only correct form of relativism is dialectical materialism?
  6. What impact does the 'symbolist', 'physical idealist' etc philosophy have on scientific discovery?

Empirio-Criticism and Historical Materialism

In this chapter Lenin brings the discussion, which up till now has been focused on the philosophical question of knowledge or epistemology, in relation to practical, political activity. Lenin shows this is not merely an academic discussion. How do these philosophers of pure ‘experience’ fare when tackling sociological questions? What is their position on historical materialism?

Lenin starts with the empirio-critic F. Blei, who attempted to use his philosophical theory to criticise what he saw as the ‘metaphysical’ character of political economy. Lenin shows, with extensive quotations, how the school of empirio-criticism simply dismisses all economic theory, especially Marxism, on the grounds it is ‘metaphysical’, meaning it deals in abstractions or generalisations such as economic laws. The position is not new, it is essentially the same as other positivists and empiricists like Hume, for it is nothing but the denial of the general, of lawfulness, on account that nothing exists but individual experience. Taken to its conclusion, it is essentially the denial of society altogether.

It is worth highlighting, in Lenin’s response to this, how in subsection 2 (‘How Bogdanov Corrects and ‘Develops’ Marx’) he gives an excellent account of how economic laws, and historical development, take place in and through the unconscious, or semi-conscious, activity of individuals developing techniques of production. In explaining this he makes use of the dialectical principles of part and whole, and necessity and chance - laws, or necessity, emerge through the more or less accidental activity of many individuals, activity which affects not just themselves but society as a whole. Empirio-critics, who lack dialectics entirely, can see nothing but a series of atomised individuals performing separate activity, and therefore cannot grasp economic lawfulness.

In doing so, Lenin demonstrates the correctness of the notion that social being determines consciousness, because consciousness is incapable of grasping the the sum-total of all this economic activity of individuals. This objective activity takes place regardless of whether or not we understand it, but it is possible, as Marx has shown, to grasp the overall laws governing it, if not every detail of economic activity in a given society.

Lenin also reveals the reductionism of Petzoldt, who despite, as an empirio-critic and positivist, rejecting ‘metaphysical’ abstractions, reduces all social phenomena to the abstraction of ‘stability’. This is typical for such philosophers, because their positivism rejects a real, scientific study of economic laws, in favour of purely individual experience. This leaves them nothing with which to explain social phenomena, and so they have to resort to idealistic abstractions about morality to get by.

It is also worth highlighting Lenin’s brilliant points on the phrasemongering of such philosophers. Lenin aptly describes their terminology as a ‘dead scholastic appendage’. This is highly relevant to academia today, which is rife with trendy terms which add nothing to our understanding. It is a product of the cloistered and competitive nature of this petty bourgeois environment. The table produced by Haeckel, shown at the end of the chapter, demonstrating the ‘ghost in the machine’ of idealism also reveals the relationship between idealism and this industry of verbal jugglery that is academia. The point is, as Lenin says, that this demonstrates idealism creates ‘philosophical-artifices’, whereas materialism identifies the problems that need solving and provides a method for solving them. Because idealism discourages a rigorous, scientific approach to theoretical problems, it is the perfect outlook for professors who wish to invent ‘revolutionary’ theories, unhindered by the need to prove them, to sell new books.

In subsection 4, Lenin explains how, in contrast to this, Marx and Engels did not just develop materialism as a philosophical position, but consistently applied it to real problems with great clarity and with historical results. To this day, the achievements of Marx and Engels in both theory and practice stand out compared to all others.

Lenin explains that Marx and Engels were partisans in philosophy, and explains why. In the final analysis, philosophical schools express historical development, and the material interests of different classes, albeit usually in disguised form. The great question facing humanity today is: how to resolve the problems of capitalist society? Marx and Engels used dialectical materialism to show how to do so, and proved that only the working class can take society forwards. Those who refuse to recognise this fact, cannot admit its validity, and so need recourse to philosophical obfuscation, to do so. Frequently, they hide behind forms of subjective idealism to justify this, arguing that to believe in the working class is naive and simplistic. The empirio-critics are like reformists who pretend to stand on neither side of the barricade, but want instead a reconciliation between the warring classes. In doing so, they help to weaken the ideological convictions of revolutionaries and thus do service to reaction.

Study Questions:

  1. Blei denies the meaning and validity of all sociology and economics on the basis they abstract from individuals and base themselves on general processes that only the mind can produce. What element of dialectics does this lack?
  2. Why is Blei's criticism of Marx's preconceptions ironic?
  3. Why is Petzoldt’s theory so reductionistic and speculative, as seen with his fixation on ‘stability’, when he leaves the terrain of epistemology and considers social and political questions?
  4. How does Lenin's statement that consciousness reflects being show he does not have a ‘copy theory’ of consciousness? And how does this discussion show how ‘crude materialism’ actually falls short of materialism? How do his later comments on how social being is independent of consciousness, and the need to accurately grasp social being’s character in order to change it, also show this?
  5. How does Lenin’s exposition of the laws of society arising independently of the consciousness of individuals help in answering Blei’s earlier point that social laws can only be inventions of the mind?
  6. Can you think of any good examples of ‘empty scholastic appendages’, - ie the peddling of new phrases that add absolutely nothing to real knowledge?