"There is a tendency to think of knowledge as a mental state. Now I am supposed to know my own mental states. If I say I have a certain mental state and do not have it, then I have told a lie. But I can say that I know so and so, and it can turn out that so and so is false; but it doesn’t follow that I lied. Therefore, knowing is not a mental state."

I encountered this in Norman Malcolm's biography of Wittgenstein. Can someone explain to me what Wittgenstein means when he claims knowing is not a mental state?

  • 2
    I don't see a question here. Commented Sep 13, 2014 at 5:09
  • We can see Belief : "Belief is a state of the mind" and the (possible) definition of knowledge as Justified true belief. Commented Sep 13, 2014 at 11:27
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    There are now 5 answers to this question, and none of them describe Wittgenstein's theory of knowledge. Heck, none of them even mention Wittgenstein. This question is not being answered. Commented Jun 16, 2015 at 0:59

6 Answers 6


That is an awesome quote. Here are some thoughts:

If I go looking for a chair, I can find one using at least two of my five senses. If I go looking for my knowledge of something, it can't be found.

The tendency then is to lump it together with in the stew pot of our mental states. But mental states are ethereal; always morphing; never really a thing one has complete consciousness or control over.

Knowledge implies a sort of permanence. When I know something, I expect it to remain true as long as I know it. I expect that it has a consistency not afforded to a mental state. If water freezes at 32 deg Fahrenheit (0 Celcius), I expect this to be true until it is proven untrue (I will then know that truth in the same way). Where I know it is not in my mind as such. I know it (how do I know my name?) in a more deeply integrated chamber of my Self. It is part of me in a more permanent way than some conditional, temporary, mental state.

To know something is not the same as it is to be something. However, I assert that for most things we know - and I mean really know (like my Name, my gender) - we know in a way that we think is the same as being. If you were to convince me my name is Bob (it's not), it would really only be an affront to my knowledge, but it would occur as an affront to my being. Things we know deeply have an inflexible quality and are more solid than mental states. Think an iceberg vs floating ice chunks.

I can know things this deeply that have the quality of being untrue. At one point man knew that the earth, then the sun, was the center of the universe. This knowledge had a static and deeply entrenched quality. I did not believe it to be true; I knew it to be true.

When I know things, I am that knowledge. It does not rest upon anything other than the fact in question having risen to a particular point on my available information hierarchy. It stops living in my daily mental processes and begins to live somewhere deeper and more permanent.

I realize I could write for hours and not get close to a full dissection of this quote, and I'm on my mobile right now. So for now - those are my thoughts - definitely not something I know.

  • Interesting reflections though not Wittgenstein's view of the matter, not one of the prominent arguments against beliefs being "in the head." Commented Jun 15, 2015 at 21:50
  • @ChristopherE. The original question asked for a dissection of the quote, and has since been edited so that my answer now doesn't fit. I should probably delete it; though I confess I do like it.
    – dgo
    Commented Jun 16, 2015 at 7:54
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    Aha. I see. Moving target. Commented Jun 17, 2015 at 14:07

"I know that the number 12 horse will come in first place."
"The number 12 horse has finished fourth."
I lied because, in fact, I did not know how the race would end.

In other words, the quote seems bogus to me based on the above check. Therefore, I discount the entire quote as questionable, including the part referring to knowledge.

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    A single counterexample only invalidates a generalization. I can say I know where my keys are, and mean it, without lying, but be wrong. I can know that birds are not dinosaurs, (because when I went to school that was the appropriate trained response), and I can mean it, without lying, and be wrong. Knowledge is something both more durable and less immediate than an actual mental state. Because knowledge is durable, and the world changes, it is not as reliable to report as one's current mental state.
    – user9166
    Commented Jun 5, 2015 at 23:18
  • @jobermark You make a good point, but, the OP quote states "If I say I have a certain mental state and do not have it, then I have told a lie." In fact, as you stated, it's not necessarily a lie. Commented Jun 6, 2015 at 0:24
  • Huh? I think you miss my point, and I surely miss yours. If you are assuming the opposite of what is to be proved, you will clearly not see it proved. What state of mind are you referring to? If it is knowledge this is totally circular nonsense.
    – user9166
    Commented Jun 6, 2015 at 0:27
  • My point is that the quote in the OP is questionable. One does not necessarily lie if they are wrong. Commented Jun 6, 2015 at 0:30
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    I still think knowledge is not a mental state, but the latent content of an uncathected potential mental state (if that is not too much psychobabble for you). I can know things but not know them at the moment. Otherwise I am in far too many mental states all at once. I know Justin's phone number but I cannot recall it at the moment... What? How can you be in both states at once? Well, one is latent. So most of the time both are latent.
    – user9166
    Commented Jun 6, 2015 at 0:37

If I say I have a certain mental state and do not have it, then I have told a lie.

  • If you say "I believe I can fly", you're lying.
  • If you say "I don't believe the sky is green", you're telling the truth.

Belief (or the lack thereof) refers to a mental state. It is something you are aware of and that you can describe to others with a high degree of accuracy.

But I can say that I know so and so, and it can turn out that so and so is false; but it doesn’t follow that I lied. Therefore, knowing is not a mental state.

While belief is a mental state, knowledge is not. To really know something requires both that you believe in something and that whatever you believe in is truthful.

While belief is something that you are aware of yourself and that can be verified just by looking inward (without any external sources of verification), verifying the truthfulness of that something you believe in requires external information.

Consider the notion that extraterrestrial aliens have come to earth and abducted humans several times in the past. You may or not believe that notion and you can verify that (dis)belief just by looking inward. However, the knowledge of whether extraterrestrial aliens have indeed come to earth and done those things cannot be verified by looking inward.

While you may think you are 100% certain that that statement is either true or false, that being truthful knowledge requires external verification. You can be 100% truthful in expressing what you believe and still be 100% inaccurate in expressing what is true.

  • I have difficulty considering most science true, or considering not knowledge, so I don't buy this.
    – user9166
    Commented Jun 12, 2015 at 0:10
  • @jobermark : You lost me there... Commented Jun 12, 2015 at 19:13
  • OK, is the atomic theory of matter not knowledge? It is only partially true, right? In an absolute sense, it is false. We found parts of atoms. Did that suddenly make all of Boltzmann's science no longer knowledge? We still use it, because the divergence between what it predicts and what we see is still pretty small. (It has problems dealing with the fact 4 degree centigrade water in a colder lake does not rise to the surface, but falls to the bottom, for instance.)
    – user9166
    Commented Jun 12, 2015 at 19:21
  • Science is still knowledge, even though, as a model of reality, it is not in any way absolutely true, and its only justification is that it makes what we observe seem logical. So it is not verified. (Popper, e.g. would insist that it cannot be verified, only falsified.)
    – user9166
    Commented Jun 12, 2015 at 19:22
  • The answer also misses that knowledge is somehow 'stored', that I can know someone's phone number but not be able to recall it at the moment indicates that knowledge has the property of not being real belief, but being a sort of latent, stored belief. I can know things, and when I recall them, decide I was wrong. So if the knowledge is belief, how does that happen? Belief is not temporal in that way. I am pretty sure that was Witgenstein's point. That knowledge has parameters (like time) that belief lacks, so as an object they are not the same.
    – user9166
    Commented Jun 12, 2015 at 19:33

Both of the other answers refer to a common theory of knowledge from the 20th century called "justified true belief", which defines knowledge as believing something under the conditions that it is justifiable for you to do so.

One recent challenge to this idea is the Gettier problems.

These problems have helped to buoy the view that knowledge should not be understood in terms of belief but rather as a successful type of action. John Greco and Ernest Sosa have both done very interesting work on this point. Sosa argues for virtue epistemology which defines to knowledge in the following manner:

to know affirmatively is to make an affirmation that is accurate (true) and adroit (which requires taking proper account of the evidence). But in addition, the affirmation must be apt; that is, its accuracy must be attributable to competence rather than luck.

I cannot speak to the quote directly, but it seems highly amenable to this reading of knowledge or least less amenable to the notion that knowledge is justified true belief.

  • Does pointing to others who provide no answer and yourself not providing and answer amount to an answer, or rather does your submission above display something about you, yourself? I ask this because you routinely delete answers that I contribute so it seems only fair for me to reciprocate criticism. You provide no answer here, right? Commented Jun 18, 2015 at 18:41
  • @RonRoyston I'm not really following your thought process here. If you think I've unfairly deleted answers, please ask about that on meta. Regarding this answer, I reference to three professional philosophers, one of whom raises the problem and two of whom identify knowing as a type of action. That sounds like an answer to "why is knowing not a mental state?" ...
    – virmaior
    Commented Jun 18, 2015 at 22:59

We might start from some concrete examples of his assertion. I know where my keys are, and I am wrong but not lying. I am confused. Or I know dinosaurs aren't birds, and I am wrong, but not lying. I was taught biology 30 years ago, and I am misled.

To some degree, in each case, I have done the work of justification and succeeded at establishing the truth of the proposition, but then the world changed. So the issue is not truth, or justification, it is time and mutability.

Beyond the uncertainty the quote points directly at, having these additional dimensions makes it difficult to classify knowledge as a mental state.

You could go well out of your way and identify it as a component of a composite mental state that transforms across time. But then what isn't? The notion is dauntingly broad. And you would need a separate component for every nuance of every item of information that you separately know, which takes us in unhelpful directions.

At that point, the question is answered, without needing a real definition of knowledge in terms of mental states. But looking deeper might help us consider the reason for the confusion.

(The quote is clearly dealing with knowledge as a personal property, and not on knowledge as a transmissible currency. It is to that latter form that the notion of 'justified true belief' applies better. And it is the former form that I will seek to define.)

We know (vaguely) when we come to know a proposition, and subjectively that point is a moment of belief. So there is motivation to consider knowledge to be the temporal trace of a past belief.

But there are confusing difficulties with knowledge of propositions that other mental states also generally don't have, which give it a mechanical feel. I can both know X's phone number and not be able to retrieve it at the moment. To the degree that I am just re-entering a past mental state, this should not be possible.

So the trace itself is not an image, it is more complex.

I can also only vaguely know something I once more clearly knew. If knowing were just stored belief, this fuzziness of knowing should be the same level of indecision that the belief had when I initially held it, or should at least be related. And it does not seem to be. The fuzziness of time seems independent of the surety at learning.

Beyond that, there are things we know that are not propositions. We know procedural things: driving a car, playing the piano, speaking... And we know impressionistic things: how to choose the right gift for the right person, when to use what rhetorical tone...

A lot of that is clearly knowledge. But because of its form, we are seldom conscious of it. And we may not consider the decision we made to act in the way that constitutes the knowledge itself to be a belief in particular, but it does involve some assent of faith.

Without some internal model of what memory and processing are and how memory modifies itself, the best you can honestly propose as a definition is that knowledge is the effect that faith in a past decision has upon your future thinking.

The most clearly identified effect would be reuse of information captured in a past mental state by reflecting upon or partially reconstructing the times you have decided that information had value. And that is probably why we think of knowledge as a mental state itself. But it is hardly the most important one, much less the only one.

Adopting a sort of Jungian psychoanalytic model of memory as a network of cathectic complexes, knowledge can be characterized as the latent content of an inactive potential mental state.

A memory forms connections to the memories around it, which reshapes them, but most of the time it just lies there until a related piece of knowledge makes it relevant, at which time it reactivates as an image of the memory of acquisition and information merged with that memory at each prior activation. (Complex formation is a form of Hebbian learning that takes place during cathexis.) Given stronger activation, the image is realized and one can temporarily re-enter the modified prior state.


Naively, mental states refer to what we think or believe. I certainly know what I am thinking and so if I tell you something about my thoughts I can be certain that what I told you was either true or false. If I told you something certainly false, I have lied.

However when I tell you about things that I know about but are not mental states I cannot be certain what I told you was true or false. Because I cannot be certain what I told you was true, if it turns out to be false I did not necessarily lie.

Although I fear my argument looks circular I think the distinction between what is a mental state and what is not a mental state is clear. Examples of mental states - 'I'm thinking about a chair', 'I feel happy', 'I believe the sky is blue'.

However, I think it is ambiguous whether a statement like 'I was thinking about a chair' is a statement about a mental state or not. Assuming people have imperfect knowledge about previous mental states it is possible someone could tell you a falsehood in this way without knowing that they were lying.

  • To me, it seems like there's an equivocation involved in calling introspecting "knowing" and calling making accurate statements about things that are true in our world "knowing". The former are veridical statements made about mental states; the latter are veridical statements about things I do not have such immediate access to.
    – virmaior
    Commented Jun 16, 2015 at 2:45
  • Yes, I agree. I tried (and failed) to answer without saying that I 'know' my mental states but I think the distinction between the two 'knowings' is clear. You put it better than I could!
    – mauiaw1
    Commented Jun 16, 2015 at 12:55

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