A.J. Ayer's essay "Knowledge and Certainty" is an attack on Wittgenstein's critique of G.E. Moore, who famously claimed that proving the existence of an external world was as simple as pointing to one's hand and saying "here is a hand"1. Moore proposed a "common sense" account of knowledge, which was meant to expose many philosophical problems (that of extreme skepticism, for instance) as absurd. Moore insisted that we do have knowledge of the external world, which renders claims of skepticism irrelevant and foolish. This knowledge consists of, for example, the knowledge that we have bodies, that we have experienced the world,and that the earth has existed for some time prior to our arrival on it (CS 53). For Moore, this sufficiently answers the skeptic; however, Wittgenstein is not satisfied.

In On Certainty, he wonders whether anyone can actually say they "know" such things. It seems impossible to really doubt any of them, which puts the possibility of knowing them into question. As Wittgenstein says "from its seeming to me –– or to everyone –– to be so, it doesn't follow that it is so. What we can ask is whether it can make sense to doubt it" (OC §2). Wittgenstein suggests that while we cannot know whether or not we have a body, it does not make sense to doubt it either; this, he says, is what forms the larger backdrop of our experience of the world. We can only know something within the framework of an epistemic system – for instance, we can know whether or not it takes an object a certain amount of time to drop a certain distance. What we cannot know is the truth or falsity of those things that constitute the limits (the backdrop) of our world – that is, we cannot know whether our measurement of time, for example, corresponds to anything universal, or whether it is merely a human production2.

On Wittgenstein's view, Moore is attempting to do precisely that when he says "here is a hand" or "I know I have a hand": he is not making the claim in reference to any context. Rather, he is trying to make it outside of all contexts. In other words, Moore is trying to say that he has absolute knowledge of his own existence and thus absolute knowledge of the external world. Wittgenstein finds Moore's argument troubling, although he does not entirely disagree with it either.

This is where Ayer's response to Wittgenstein becomes important. He accuses Wittgenstein of, among other things, being an "irrealist" (KC 125), because Wittgenstein does not see "the possibility of there being any cognitive process which would permit the prising of the world off language" (Ibid.). It is with this reading of Wittgenstein that I take the greatest exception. I would like to argue, contra Ayer, that Wittgenstein is not an "irrealist"3, and that such a designation does not even make sense. Further, I would like to suggest that Ayer's criticism does not really speak to what Wittgenstein is actually saying, and that he also misses Wittgenstein's point. Ayer appears to cling to the possibility of knowledge outside of every context, but he fails to justify his assertions in the same way as Moore. Wittgenstein's point is that these assertions cannot be justified, and that seems to be what is lost in Ayer's reading. Here I will turn to Wittgenstein's problems with Moore in On Certainty; then I will deal with Ayer's response and follow up both with my own response.

Wittgenstein on Moore

In "A Defense of Common Sense", Moore sets out by saying "I am going to begin with enunciating, under the heading (1), a whole long list of propositions, which may seem, at first sight, such obvious truisms as not worth stating: they are, in fact, a set of propositions, every one of which (in my own opinion) I know, with certainty, to be true" (CS 53). He calls this his "list of truisms" and includes in it his knowledge that he has a body, that his body has been in contact with the earth's surface or close to it for his whole life, and so on (Ibid.). He works through the list of truisms and its associated propositions4, which provide the groundwork for his proof of an external world. As I stated in the introduction, his proof lies in pointing to his hand and asserting its presence:

I can prove now, for instance, that two human hands exist. How? By holding up my two hands and saying, as I make a certain gesture with the right hand, "Here is one hand," and adding as I make a certain gesture with the left, "and here is another." And if, by doing this, I have proved ipso facto the existence of external things, you will all see that I can also do it now in numbers of other ways: there is no need to multiply examples. (Ibid. 57)

This is where Wittgenstein becomes troubled, for it is upon this particular proposition (the claim of having proved something) that the whole problem hinges. It appears to make perfectly good sense to answer the skeptic by saying something along the lines of "Oh, poppycock! Look, my hand is right here! It exists!" and indeed, many of us would do just that. Moore himself says "did I prove just now that two human hands were in existence? I do want to insist that I did; that the proof which I gave was a perfectly rigorous one; and that it is perhaps impossible to give a better or more rigorous proof of anything whatever" (Ibid.). This alone seems to be unproblematic: within the epistemic boundaries of our world and our perception of it, we can make claims of this order.

Moore wants to use this claim, which can be made within an epistemic framework, to "prove" that he has knowledge of the framework itself; perhaps, going beyond that, he wants to say that there is no such framework and our knowledge of the world is non-contextual or unconditional. He wants to speak about the existence of things external to us, without reference. To put it another way, he wants to obtain the "view from nowhere" –– in fact, he claims that we can have it –– from which we can know things beyond the conditioning of language and without epistemic limitations. Moore claims that he knows (that he cannot be mistaken, that he has access to the absolute truth) he has a hand and that this is proof of an external world. His claim is a major problematic for Wittgenstein, who feels as though Moore is conflating "I know that" with "I am certain that":

Moore's view really comes down to this: the concept 'know' is analogous to the concepts 'believe', 'surmise', 'doubt', 'be convinced' in that the statement "I know ..." can't be a mistake. And if that is so, then there can be an inference to the truth of an assertion. And here the form "I thought I knew" is being overlooked.––But if this latter is inadmissable, then a mistake in the assertion must be logically impossible too. And anyone who is acquainted with the language game must realize this––an assurance from a reliable man that he knows cannot contribute anything. (OC §21)

So if "I know" is more or less equivalent to "I am convinced",but there is no possibility of being mistaken, what is Moore really talking about? Even if he could be mistaken, how would he know? If he started to doubt things like the existence of his body, would that doubt even make sense?

Wittgenstein thinks that such doubts make as little sense as claims that we know that we have bodies, or that the earth existed for a long time before our birth, or that we have hands. "If Moore says he knows the earth existed etc., most of us will grant him that it has existed all that time, and also believe him when he says he is convinced of it. But has he also got the right ground for his conviction? For if not, then after all he doesn't know (Russell) (Ibid. §91). The whole issue seems to be one of talking about the grounds of "belief" and of "knowledge". When Moore points to his hand and asserts that it does exist, he does so because of a backdrop that provides the grounds for saying so. His hand's existence is a part of his experience of the world; as such, it cannot provide a ground for saying that the grounds themselves are either true or false.

As Wittgenstein says, "I did not get my picture of the world by satisfying myself of its correctness; nor do I have it because I am satisfied of its correctness. No: it is the inherited background against which I distinguish between true and false" (Ibid. §94). In other words, someone's picture of the world is the criteria for all other judgments; the relationship cannot be reversed to provide criteria for judging the world picture itself. As Wittgenstein says, we do not verify and falsify all components of the world as we experience it before we decide on what it actually is; rather, we are brought up using language in a community and we are "taught" the world.

To be able to do what Moore is suggesting, we would have to be able to view the relationship between our propositions and the states of affairs to which we apply them. In the Tractatus Logico-Philosophicus, Wittgenstein describes this kind of relationship, arguing "A proposition is a picture of reality"5 (TLP 4.01) and

At first sight, a proposition––one set out on a printed page, for example––does not seem to be a picture of the reality with which it is concerned. But neither do written notes seem at first sight to be a picture of a piece of music, nor our phonetic notation (the alphabet) to be a picture of our speech. And yet these sign-languages prove to be pictures, even in the ordinary sense, of what they represent. (Ibid. 4.011)

As Wittgenstein later realized, it is problematic to say things of this sort. There is no logical order of language, nor is there a logical and "real" connection between language and reality.

(Tractatus Logico-Philosophicus, 4.5): "The general form of propositions is: this is how things are."––That is the kind of proposition that one repeats to oneself countless times. One thinks that one is tracing the outline of the thing's nature over and over again, and one is merely tracing round the frame through which we look at it. (PI §114)

If we adopt this contrast to imagine Wittgenstein's criticism of Moore's acccount, we can get a clearer picture of what he finds troubling. Moore seems to be giving a kind of metaphysical weight to the meaning of "here is a hand" in the sense that what we can say about our perceptions and collectively agreed-upon norms somehow speaks to some kind of greater reality. To use an analogy again, Moore's "here is a hand" is similar to deriving a "law" of gravity from repeated experimentation with and observation of falling objects. The fallacy occurs in treating the law of gravity as a meaningful description of reality, one that we have discovered rather than developed. The theoretical implementation of a law of gravity is useful and rings true when held up against our epistemic framework; however, we do not know that there is a law of gravity outside of our usage of the concept6.

Likewise, we do not know that the external world exists except within our epistemic context (which includes language as well as perceptions), and we cannot get outside to find out whether or not the framework is itself true. Since we cannot get that unconditioned view, we cannot speak of knowing whether or not it is true (because we have no grounds to do so); instead, we just work with it. We can be convinced, and we can be certain, but we cannot make that final jump to really "knowing". "So here the sentence 'I know ...' expresses the readiness to believe certain things" (OC §330) rather than the condition of being able to be mistaken but not being in error about the issue at hand. "One might say: 'I know' expresses comfortable certainty, not the certainty that is still struggling" (Ibid. §357)

Wittgenstein certainly struggles with his response to Moore; one gets the sense that even in the midst of responding, he is still wondering what it is that troubles him so much. There are certain similarities between his position and Kant's. In the Critique of Judgment Kant insists and emphasizes that there is a gap between the phenomenal and noumenal that cannot be closed – we may suppose, for instance, that there is a purposive structure of nature, but we cannot prove it, and thus we must withhold a final judgment even though we feel certain of it (CJ §80)7. Although Wittgenstein is not a metaphysician and does not posit the existence of a metaphysical "reality", the concern seems to me to be the same. Moore actually responds to Kant's account in "A Defense of Common Sense", saying that he thinks Kant is wrong and that we can know things without proof (at least the kind of proof that Moore thinks is demanded within the philosophical tradition).

So, at least in some sense, Wittgenstein rescues the Kantian tradition and once again separates certainty from knowledge – at the very least, he cautions against the kind of mistake he sees being made in Moore's account8. Finally, it must be stressed that Wittgenstein is not proposing a radical skepticism by any means; rather, I would suggest that he is proposing a softened realism. He does not deny the reality of phenomena, or the possibility of our being certain of them. On the contrary, he merely wants to bring out more fully the epistemic limitations to which we are subject, and therefore the limitations on the senses in which we can deploy the phrase "I know that ...".

Ayer vs. Wittgenstein

In his response to Wittgenstein, Ayer takes exception to Wittgenstein's assertion that we cannot "legitimately speak of ... (Moore's type) of propositions as being known to be true" (KC 116). Of course, Ayer sides with Moore, saying that we can know things because sufficient proof exists in "the actual occurrence of the experiences which (people) describe" (Ibid. 114) or because "there came a stage at which a demand for further proof was no longer apposite" (Ibid. 115). Wittgenstein's argument that "to say that one knows a proposition to be true is not an acceptable method of proving it (Ibid. 114) is itself not acceptable for Ayer.

On Ayer's view, Moore's use of the word "I know" is not a misuse. To say "I know I have a hand" is a perfectly fine, everyday proposition, even though (as Ayer points out) "there is seldom any point, outside the practice of philosophy, in formulating such a sentence" (Ibid. 109-10). He thus takes On Certainty to be something of a polemic against Moore as well as against common sense and goes through "Knowledge and Certainty" giving numerous examples of how we can furnish adequate support for saying that we know things to be true. For instance:

One obvious way in which this demand could be met would be by (and informant) supplying us with evidence which gave strong support for the proposition concerned, where the evidence consisted of one or more propositions which were themselves equipped with adequate support. (Ibid. 116)

Ayer acknowledges the possible criticism that this might lead to an infinite regress of supporting evidence for propositions, but argues that we would be able to rest at a point where propositions are supported by "their own content or ... the conditions under which they were expressed" (Ibid.). Following Moore, he states that in these circumstances, we can safely speak of knowing things to be true. He finds it troublesome that Wittgenstein suggests that "only under cover of certain assumptions (does) the notion of agreement with reality come into play" (Ibid) 119), and disagrees with what he sees as Wittgenstein's doubt.

Unfortunately for Ayer, he seems to be misreading Wittgenstein's account in On Certainty. First and foremost, Wittgenstein is not advocating doubt or skepticism – at least not in the way that Ayer thinks. Wittgenstein is not an "irrealist" in the sense that he give s "theory" priority over "fact" (Ibid. 125); on the contrary, he is fully willing to accept things as fact and believe them. As he says in On Certainty, "do I, in the course of my life, make sure I know that here is a hand––my own hand, that is?"(OC §9). More to the point, he wonders if we can even make sure of such things: we can perhaps feel one hand with the other, hold it up to a mirror, show it to other people and ask them if they see it, and so on – but what does this prove? It shows that within our world-picture, the presence of our hand makes sense; however, that is only within the world-picture and as I have stated, Wittgenstein argues that we cannot see things in any other way.

We are always touched by the world: it acts as grounds and limit simultaneously. Again, as he says in the Investigations, we can only reach as far as the frame of our world-picture when making propositions about it. Ayer seems to be missing this point repeatedly. Wittgenstein is not making a radical break by saying that there are limits to what we can know, he is trying to point to a problem in the way we use the words "I know".

Also, Ayer offers up the following criticism of Wittgenstein's account: "If all that he meant ... was that (propositions) were intelligible as they stood, we need not take issue with him. If, on the other hand, he meant that they offered no call for elucidation, he was surely wrong" (KC 124). This seems somewhat misguided. Wittgenstein at no point makes such an assertion, and he certainly does not deny that concepts can be elucidated, elaborated upon, and "made better" (that is, made more useful). His doubt lies in whether the ultimate elucidation can be made – that point at which we can say that we have knowledge of something. Wittgenstein asks "Should I say 'I believe in physics', or 'I know that physics is true'?" (OC §602). This question seems to embody the central theme of On Certainty

I am taught that under such circumstances this happens. Making the experiment a few times has discovered it. Not that that would prove anything to us, if it weren't that this experience was surrounded by others which combine with it to form a system. Thus, people did not make experiments just about falling bodies but also about wind resistance and all sorts of other things. But in the end I rely upon these experiences, or on the reports of them, I feel no scruples about ordering my own activities in accordance with them. (Ibid. §603)

This seems to be what (and Moore, for that matter) is missing most fundamentally. While Moore simply wants to throw up his hands and be done with the matter9, Wittgenstein thinks that Moore does not realize that he cannot make the claims he is trying to make in the way he is trying to make them. By just saying "here is a human hand" and then using that as a proof of the external world, Moore is ignoring all of the other propositions, assumptions, states of affairs, learned beliefs, and so on, that make his claim possible in the first place.

Thus, while Ayer sees Wittgenstein's approach as erratic and nebulous, Wittgenstein is really trying to bring out the complications involved in making knowledge claims. Maybe we can say that we know things, and have good reasons for saying so, but it always occurs within a system and we do not know facts independently of one another. Therefore, we cannot just pick up a particular proposition and say "I know this to be true," without affirming a vast system and vast history which has produced that system. It is this system which makes our knowlege possible, and we cannot have knowledge of the system anymore than we can "see" time except through the measurements we have developed for it. "It is so difficult to find the beginning. Or, better: it is difficult to begin at the beginning. And not try to go further back"(Ibid. §471).

In other words, we are not given the system of our knowledge before we go into the world; we are born into it and it is just there. Within it, "true" and "false" make sense, as do "knowledge" and "certainty", but those words lose their meaning when applied to the system itself. How does the system function for us? Through language: "A meaning of a word is a kind of employment of it. For it is what we lean when the word is incorporated into our language"(Ibid. §61). Thus, language is inextricably tied to what we know – and vice versa.

Concluding thoughts

Ayer's critique is highly unsatisfactory. Primarily, he misses the thrust of Wittgenstein's account and therefore does not properly address the issues raised in On Certainty. When he thinks Wittgenstein is rejecting "fact", Wittgenstein is actually unpacking the notion of what a "fact" is and how it is constituted. He also seems to be misinterpreting Wittgenstein when he says "I have conceded that it may nearly always be pointless and possibly misleading for me to say such things as 'I know I am seeing red' or 'I know that these are my hands', but I have tried to show that this in no way entails that what I am saying is not empirically true" (KC 117).

Again, Wittgenstein is not arguing anything of the sort. He is calling into question the meaning of words like "know", "true", and "empirical" as they are often used philosophically. Ayer seems to be reading Wittgenstein's account as a radical, total rejection, but it is actually a questioning and elaboration. He has not sufficiently answered Wittgenstein's argument that our knowledge can only occur in a system and not be taken apart and examined as separate components10: he has not shown why this is not the case. Since this is central to Wittgenstein's response to Moore, Ayer has not really properly picked up on the argument and is therefore talking at cross-purposes to it. He continues to maintain that "knowledge"and "certainty" can be legimately employed (Ibid.) in the way that Moore does, but he still seems to be falling prey to the same mistakes as Moore. Thus, Wittgenstein's account has not really been addressed in the first place, much less seriously challenged.

  1. See Moore's "A Defense of Common Sense", the essay to which Wittgenstein responded in On Certainty.
  2. To put it another way, we might ask the question "Did we discover time, or did we invent the concept of time based on certain observations we have made and the way we experience the world?"
  3. I would like to say "whatever that means" here, but that would perhaps be a bit uncalled for
  4. Namely, that human beings generally are able to claim similar types of knowledge with certainty and should be able to recognize Moore's account base on their own experiences (CS 54).
  5. Of course, Wittgenstein later rejected his work in the Tractatus and revamped his whole approach in the style of Philosophical Investigations. The Tractatus is nonetheless useful in this instance because it speaks to the kind of relationship necessary between propositions and reality for Moore's account to make sense. In other words, Mooore's account has to be realist for it to work properly. Language does have to correspond to reality; otherwise, we are not necessarily speaking the truth about anything.
  6. Similarly, Wittgenstein says "We are satisfied that the earth is round" (OC §299). He means to highlight the difference between depending on a proposition that adequately and coherently helps form our world-picture, and knowing that it is true (that is, being in a position where no mistake is being made).
  7. The reference I just listed is, of course, just one place among many in Kant's work where examples like this can be found.
  8. It is also perhaps worth mentioning the possibility of discussing Wittgenstein's concerns in a moral or ethical light. We can apply his line of questioning not only to epistemic concerns, but also to political and societal ones. A backdrop – our world-picture – frames our certainty that physical objects exist (for instance); similarly, moral beliefs occur in the same way. Dogmatic beliefs in moral codes arise because we make the mistake of thinking that we know their validity and correctness to be true. Furthermore, this occurs despite the fact that no proof exists for any moral propositions. In this sense, we can talk about Moore's mistake as being dangerous, for it creates and supports the possibility of dogmatism and terror; however, this is a topic that is perhaps best left to another paper.
  9. Pardon the pun.
  10. Any more than it can be categorized and made more easily managed!

  • Ayer, A.J. "Knowledge and Certainty" (KC) in Wittgenstein. London: Weidenfeld and Nicholson, 1985.
  • Kant, I. Critique of Judgement (CJ), trans. Werner S. Pluhar. Indianapolis: Hackett Publishing Company
  • Moore, G.E. "A Defense of Common Sense" (CS), in The Theory of Knowledge, ed. Louis. P. Pojman. Toronto: Wadsworth Publishing Company, 1999.
  • Wittgenstein, L. On Certainty (OC), trans. Denis Paul & G.E.M. Anscombe. 1969; Oxford: Blackwell Publishers, 1999.
  • –––––––– Philosophical Investigations (PI), trans. G.E.M. Anscombe.
  • –––––––– Tractatus Logico-Philosophicus (TLP), trans. D.F. Pears & B.F. McGuinness. 1921; New York: Routledge, 2001.

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