Answering the Skeptic

Fafner

Here’s a version of Descartes’ classical argument for skepticism about the external world:

Let p be any generic belief about the external world, such as Descartes believing that he’s sitting in front of his fireplace or having a body.

1. For any p, if a subject doesn’t have evidence which rule out (perhaps conclusively) the possibility of an error regarding p (that is, favor the possibility that p over not-p), then the subject doesn’t know that p.

2. Waking experience is indistinguishable from a very vivid dream (or a deception by an evil demon, or being a brain in a vat etc. – insert here your favorite skeptical scenario), since there are no distinct "marks" to distinguish the one from the other.

3. Therefore, for every p a subject can’t have evidence that favor p over not-p (from (2)).

4. Therefore, no p can be known (from (1) and (3)).

My proposed answer to the argument is to challenge the transition from (2) to (3). I wish to argue that the mere possibility of vivid dreams (and so on) doesn’t prove that we don’t actually possess evidence that rule out such possibilities (my response here is based on John McDowell’s work on epistemic disjunctivism).

Recall the skeptic’s claim that having a waking experience doesn’t rule out the possibility of vivid dreams, since the two are phenomenally indistinguishable from the subject’s point of view. But does it actually follow? I want to argue that it doesn’t. Premise (1) says that having evidence in favor of p requires to be in a state that rules out the possibility that not-p. But now if we think carefully about perceptual experience in a waking state, we can see that it actually can rule out such possibilities. The skeptic asks us to consider two kinds of possibilities, such as:

a. I’m awake and sitting in front of my computer typing some text.

or

b. I’m dreaming that I’m sitting in front of my computer typing some text.

Call (a) “waking experience” and (b) “dreaming experience”. Now the crucial question is whether having a waking experience rules out the possibility of having a dreaming experience? The answer seems to me “yes”, because what does it mean to be awake if not to be in a state which is logically inconsistent with having a dream? But if this is the case, then contra the skeptic, being in the one state as opposed to the other does after all entail information about how the external world actually is, because the way things appear to you when you are awake usually matches very closely the way they really are – something which is plainly not the case (at least most of the time) when one is dreaming. But then it means that by having a waking experience the subject actually does have direct perceptual evidence that excludes the possibility of him dreaming (and very good evidence - in fact his evidence, i.e. his perceptual experience, logically excludes the possibility of him being in error about what he sees) - and hence premise (3) is false. (but on the other hand, if he is in fact dreaming then he does lack such evidence, since his conscious states don’t match the way things really are in the world – the skeptic is surely right about this).

Now, it is important to note that the skeptic doesn’t dispute the distinction between a waking and a dreaming state, because after all he is not an idealist and doesn’t claim that he can show that I’m not in fact awake sitting in front of my computer etc.; his claim is merely that I can’t know that - even if in fact I really am. But I believe I’ve shown that such strategy can’t work: the skeptic doesn’t actually know whether my experience is consistent with me dreaming that I’m sitting in front of the computer etc. (which is what premise (1) requires), because for that purpose he need to show that I’m in fact dreaming right now (something that he obviously can’t do). And if this is so, then his appeal to dreaming possibilities is not enough for his purposes, since he needs a stronger premise to actually show that I don’t have the perceptual evidence that I believe that I have.

In conclusion, here’s the moral that I believe we should draw from all of this. The skeptics’ error consists in supposing that one can “categorize” experiences into types independently of the way the world actually is. The skeptic assumed that being awake and merely dreaming that one is awake, are intrinsically the same kind of mental state – but they are not, since waking states are conceptually defined in such a way that when a subject is having things appear to him in a certain way, then it must be the case that things in the world really are the way they appear to him, and hence he can’t be in perceptual error about the external world. Hence the skeptic cannot for his argument presuppose at the same time the conceptual distinction between waking and dreaming states, and also treat them as if they were the same.

Michael

Let's say that I have a confession written in French that John is guilty of some crime, but that I don't read French. According to my understanding of your argument, this counts as evidence that John is guilty of this crime, and so I know that John is guilty of this crime.

But this doesn't seem right. I don't know that John is guilty of this crime because I don't know that this written confession is in fact a written confession.

So like above, the fact that my experiences are veridical (for the sake of argument) isn't sufficient. I also need to be able to recognize them for what they are, but according to the skeptic I can't.

And, of course, if none of my experiences are veridical then the skeptic is right regardless, so at best your argument only works if you presuppose that there is an external world, which seems to beg the question.

Fafner

I need to also be able to recognize them for what they are, but according to the skeptic we can't. — Michael

But this is an absurd demand, since it generates a regress. If something is evidence only by virtue of having a second order evidence in its favor, then nothing can ever count as evidence, since that second order evidence would in turn require having additional third order evidence and so on. And I don't think this requirement has much plausibility if we consider what we usually call "having evidence" in the normal sorts of cases outside of philosophy.

I think it is very reasonable to think that having evidence in favor of something simply consists in a. having in some sense a cognitive "access" to the evidence (and notice that in your example this requirement isn't met since you cannot read French, while in the perceptual case you can directly perceive your environment without further ado) and b. the evidence itself should in some sense guarantee the truth of what it is evidence for (and this requirement is met when you are having a waking experience, since in that case your cognitive state is very reliably correlated with the facts that you perceive).

(Also notice that this understanding of evidence is strongly 'internalist' in the epistemic sense, and so it is not an externalist account in the style of Nozick or Sosa)

Michael

I think it is very reasonable to think that having evidence in favor of something simply consists in a. having in some sense a cognitive "access" to the evidence (and notice that in your example this requirement isn't met since you cannot read French, while in the perceptual case you can directly perceive your environment without further ado) and b. the evidence itself should in some sense guarantee the truth of what it is evidence for (and this requirement is met when you are having a waking experience, since in that case your cognitive state is very reliably correlated with the facts that you perceive). — Fafner

Then let's change my example slightly. I am given a piece of paper that either has random symbols drawn onto it or Arabic writing. In either case I have cognitive "access" to the evidence; I can see it right in front of me. But I don't know if it's random symbols or Arabic writing. I need some second order understanding of how to distinguish the two. And with the case at hand, I need some second order understanding of how to distinguish a veridical and a non-veridical experience, which the skeptic claims we do not have.

But, again, at best your argument is "if our experiences are veridical then we can know that our experiences are veridical", but given that the skeptic questions the antecedent, your argument would seem to beg the question. I could even turn your argument around and argue that because our experiences are not veridical we know that there isn't an external world (or at least none that we see).

T Clark

1. For any p, if a subject doesn’t have evidence which rule out (perhaps conclusively) the possibility of an error regarding p (that is, favor the possibility that p over not-p), then the subject doesn’t know that p.

2. Waking experience is indistinguishable from a very vivid dream (or a deception by an evil demon, or being a brain in a vat etc. – insert here your favorite skeptical scenario), since there are no distinct "marks" to distinguish the one from the other.

3. Therefore, for every p a subject can’t have evidence that favor p over not-p (from (2)).

4. Therefore, no p can be known (from (1) and (3)). — Fafner

This is not a very good paraphrase of Descartes's argument. He was interested in skepticism about absolute certainty as a philosophical world view - as a way to guide our understanding. It isn't some sort of technical method for evaluating evidence.

Fafner

Then let's change my example slightly. I am given a piece of paper that either has random symbols drawn onto it or Arabic writing. In either case I have cognitive "access" to the evidence; I can see it right in front of me. But I don't know if it's random symbols or Arabic writing. I need some second order understanding of how to distinguish the two. And with the case at hand, I need some second order understanding of how to distinguish a veridical and a non-veridical experience, which the skeptic claims we do not have. — Michael

In this case the "evidence" that you need is simply to know Arabic (or at least being able to reliably identify Arabic writing). And this is not "second order" evidence in my sense, because for you to know that you know (say) Arabic, all you need is simply the mere ability to read Arabic, and you don't need in addition some further ability to identify your own fluency in Arabic which is distinct from you just being fluent in the language.

Michael

In this case what you need is simply to know Arabic (or at least being able to reliably identify Arabic writing). And this is not "second order" evidence in my sense, because for you to know that you know (say) Arabic, all you need is simply the mere ability to read Arabic, and you don't need in addition some further ability to identify your own fluency in Arabic which is distinct from you just being fluent in the language. — Fafner

So knowing Arabic requires more than just being presented with Arabic words. Somehow I need to learn that these symbols are in fact Arabic words. And so knowing that our experiences are veridical requires more than just being presented with veridical experiences. Somehow I need to learn that these experiences are in fact veridical.

And in case you missed my recent edit, I could even turn your argument around and argue that because our experiences are not veridical we know that there isn't an external world (or at least none that we see).

Fafner

↪T Clark

This is why I called it a "version" of his argument, and my aim wasn't to correctly represent his actual philosophical views. And in any case, my argument does show that we can (in some sense) acquire certainty about the world, since being in a waking state does actually logically entail that you cannot be in error about what you perceive.

Fafner

So knowing Arabic requires more than just being presented with Arabic words. Somehow I need to learn that these symbols are in fact Arabic words. And so knowing that our experiences are veridical requires more than just being presented with veridical experiences. Somehow I need to learn that these experiences are in fact veridical. — Michael

But my point is that knowing that something is an Arabic script is inseparable from the ability to understand Arabic (that is, you cannot describe someone as being fluent in Arabic without presupposing that he can as a matter of fact read Arabic); and analogously, knowing that you are having a veridical experience is nothing but just having it as a matter of fact. You know that you are seeing a tree just by seeing a tree (and perhaps some other conditions like the absence of fake tree facades in the vicinity, re the Gettier problem), and I claim that it is unreasonable to require something else in addition. (and also notice that I'm not trying to persuade the skeptic in a non question-begging way that I in fact do know that what I see is a tree (see the end of this reply), I'm only trying to give a reasonable characterization of what it is to be in a state of knowing that one is looking at a tree - see the end of my reply).

But, again, at best your argument is "if our experiences are veridical then we can know that our experiences are veridical", but given that the skeptic questions the antecedent, your argument would seem to beg the question. I could even turn your argument around and argue that because our experiences are not veridical we know that there isn't an external world (or at least none that we see). — Michael

First, I didn't assume, nor was trying to prove, that we do know that there is an external world; I was merely trying to block the skeptical conclusion that we don't know - but of course it doesn't prove by itself that we also do.

And secondly I don't agree that the argument begs the question. The skeptic claims that my having an experience say of seeing a tree, isn't a good evidence that there's a tree in front of me, since my perceptual state doesn't rule out the possibility that I'm actually dreaming. In other words, he says "I don't know whether there is or isn't a tree in front of you - you may be right about that - but what I do know is that you mental state is consistent with the possibility that there is no tree in front of you", and I have argued that he can't actually say this since he can't know whether my perceptual experience is consistent with the possibility that the tree is absent, because it conflicts with his own (implicit) characterization of the difference between waking and dreaming states. He cannot know what kind of state I'm in unless he also knows whether there is in fact a tree in front of me.

Michael

But my point is that knowing that something is an Arabic script is inseparable from the ability to understand Arabic (that is, you cannot describe someone as being fluent in Arabic without presupposing that he can as a matter of fact read Arabic); and analogously, knowing that you are having a veridical experience is nothing but just having it as a matter of fact. — Fafner

You're not comparing like for like here. Simply having a veridical experience is comparable to simply being shown an Arabic word. Just as the latter isn't the same as understanding Arabic, the former isn't the same as knowing that the experience is veridical.

You know that you are seeing a tree just by seeing a tree (and perhaps some other conditions like the absence of fake tree facades in the vicinity, re the Gettier problem)

I think that your example can itself be something of a Gettier case. If I have a veridical and a non-veridical experience of a tree, and if I can't determine which is which, and if in fact the first experience is veridical and the second isn't, then it doesn't seem right to say that I know that there's a tree in the first case. This is just epistemic luck.

And this is the sceptic's point. If I can't distinguish between a veridical and a non-veridical experience then I have no way of knowing which I'm having right now.

To offer another example, let's say that I'm shown a painting, which may or may not be a forgery. You seem to be suggesting that if it's the real painting then I know that it's the real painting, or if it's the forgery then I know that it's the forgery. But that's just not right. The fact that it is or isn't the real painting isn't sufficient to claim knowledge that it is or isn't the real painting. And so the fact that it is or isn't a veridical experience isn't sufficient to claim knowledge that it is or isn't a veridical experience.

T Clark

This is why I called it a "version" of his argument, and my aim wasn't to correctly represent his actual philosophical views. And in any case, my argument does show that we can (in some sense) acquire certainty about the world, since being in a waking state does actually logically entail that you cannot be in error about what you perceive. — Fafner

No one, not Descartes or any other philosopher I can think of, has said that we can't "(in some sense) acquire certainty about the world..." All the argument is about in what sense we can acquire it.

Wayfarer

Hence the skeptic cannot for his argument presuppose at the same time the conceptual distinction between waking and dreaming states, and also treat them as if they were the same. — Fafner

The problem I see is that it is still feasible that the waking state, the state of presumed normality, is still a consistent illusion. It would be logically possible that, at the time of death, one is suddenly roused as if from a sleep, to a mode of existence that one had never guessed at while alive, but which now is obvious once again; one might immediately begin to forget the life you had just lived, in the same way as forgetting dreams that you have just had woken from.

the way things appear to you when you are awake usually matches very closely the way they really are.... — Fafner

But the sceptic will say that this simply begs the question, i.e. assumes what it sets out to prove. If one's life were a perfectly well-ordered and consistent dream state, then the correlation between experience and the objects of perception could likewise be perfectly consistent and empirically verifiable. Even if fundamental physical constants were actually part of an illusion, provided they were consistent, then they would still make accurate predictions. The difference with that and normal dreams is that the latter are transient, inconsistent and short-lived, and most of us know on some level that we're dreaming, although at times, as we also know, they can have a scary reality of their own.

Fafner

You're not comparing like for like here. Simply having a veridical experience is comparable to simply being shown an Arabic word. Just as the latter isn't the same as understanding Arabic, the former isn't the same as knowing that the experience is veridical. — Michael

It all depends on what one means by "knowing that the experience is veridical". My point is that there is something confused in the way the skeptic thinks that we ought to know this. The skeptic thinks that our knowledge should be ultimately grounded in subjective states which don't themselves assume anything about how the world is. But I was trying to show that there's no coherent conception (by his own lights) of "subjective states" which could be described independently of how the world actually is. So to insist that one ought to prove that his experience is really veridical by the skeptic's rules is to miss the point. And I tried to undermine his argument not by responding to his challenge, but by rejecting the assumption which lead to it.

Of course one cannot prove that he "knows" that his experience is veridical in a non circular way (that is, without appealing to the experience itself), but my point is - so what? If we reject the assumption of the skeptic that mental state could be individuated without reference to the external world, then there would be no justification to keep clinging to the skeptics demand the we must distinguish veridical from non veridical experience in a way that would satisfy him.

To offer another example, let's say that I'm shown a painting, which may or may not be a forgery. You seem to be suggesting that if it's the real painting then I know that it's the real painting, or if it's the forgery then I know that it's the forgery. But that's just not right. The fact that it is or isn't the real painting isn't sufficient to claim knowledge that it is or isn't the real painting. And so the fact that it is or isn't a veridical experience isn't sufficient to claim knowledge that it is or isn't a veridical experience. — Michael

The difference is this: a non expert cannot visually distinguish forgeries from non-forgeries, while we all can in most cases distinguish trees from non-trees (and such like). So I'm not saying that whenever you believe that p, and that p happens to be true, then you know that p; what I'm saying is that you can know that p, if you have the capacity to perceive that p. You don't need a justification to believe that you have the capacity to perceive that p which is independent from the deliverances of that very same capacity; but this is not the same as saying that you can know that p whenever p happens to be true (and in your example you've assumed that the observer lacks the capacity to visually detect forgeries, so it doesn't apply to my account).

Fafner

the way things appear to you when you are awake usually matches very closely the way they really are.... — Fafner

But the sceptic will say that this simply begs the question, i.e. assumes what it sets out to prove. If one's life were a perfectly well-ordered and consistent dream state, then the correlation between experience and the objects of perception could likewise be perfectly consistent and empirically verifiable. Even if fundamental physical constants were actually part of an illusion, provided they were consistent, then they would still make accurate predictions. — Wayfarer

It doesn't contradict what I said in the quote. You just gave another example of a dream state, but my question is, what distinguishes dream states from waking states? And the point is that you cannot draw this distinction without reference to how the world is like.

Michael

The difference is this: a non expert cannot visually distinguish forgeries from non-forgeries, while we all can in most cases distinguish trees from non-trees. — Fafner

But we can't distinguish between a veridical experience of a tree and a non-veridical experience of a tree (or so the sceptic claims), and so the analogy holds.

I just don't know if right now I'm being deceived by an evil demon.

Wayfarer

↪Fafner

You can make the distinction on the basis of the difference between two states, i.e. the dream state and the waking state. And you can make that distinction on the basis of the nature and quality of experience - that the experience of waking and dreaming is qualitatively different.

Fafner

But we can't distinguish between a veridical experience of a tree and a non-veridical experience of a tree (or so the sceptic claims), and so the analogy holds.

I just don't know if right now I'm being deceived by an evil demon. — Michael

It doesn't follow, and I've shown this already. Mere inability to distinguish on subjective grounds all non-veridical states from veridical proves absolutely nothing about ones knowledge of the world. Again look at the original argument. If you have a proposal how to fix it then I'll be glad to hear it, but I think that as the argument stands, the transition to the third premise is obviously unsound, and hence the final conclusion doesn't follow.

Fafner

And you can make that distinction on the basis of the nature and quality of experience - that the experience of waking and dreaming is qualitatively different. — Wayfarer

But this is not what the skeptical argument says. The whole point is that there is no subjective differences between waking and dreaming states, otherwise, how appeal to dreams supposed to prove skepticism?

Wayfarer

The whole point is that there is no subjective differences between waking and dreaming states, otherwise, how appeal to dreams supposed to prove skepticism? — Fafner

The argument doesn't quite put it that way - Descartes says:

As I then desired to give my attention solely to the search after truth, I thought … I ought to reject as absolutely false all opinions in regard to which I could suppose the least ground for doubt, in order to ascertain whether after that there remained [anything at all] in my belief that was wholly indubitable. Accordingly, seeing that our senses sometimes deceive us, I was willing to suppose that there existed nothing really such as they presented to us … [T]he very same thoughts (presentations) which we experience when awake may also be experienced when we are asleep, while there is at that time not one of them true, I supposed that all the objects (presentations) that had ever entered into my mind when awake, had in them no more truth than the illusions of my dreams. But immediately upon this I observed that, whilst I thus wished to think that all was false, it was absolutely necessary that I, who thus thought, should be somewhat; and as I observed that this truth, I think, therefore I am (cogito ergo sum), was so certain and of such evidence that no ground of doubt, however extravagant, could be alleged by the sceptics capable of shaking it. 1

There's no mention of waking and dreaming states, simply the observation that things appear real to us in dreams, yet are not, so, likewise, the reality of things that appear to our senses may be doubted. This is what leads directly to the famous declaration cogito, ergo sum.

Michael

Mere inability to distinguish on subjective grounds all non-veridical states from veridical proves absolutely nothing about ones knowledge of the world. Again look at the original argument — Fafner

I've already addressed it. It's epistemic luck, not knowledge. Unless you can distinguish between a veridical and a non-veridical experience (or between a real painting and a forgery) then you can't know that your experiences are veridical (or if the painting is real).

Fafner

There's no mention of waking and dreaming states, simply the observation that things appear real to us in dreams, yet are not, so, likewise, the reality of things that appear to our senses may be doubted. This is what leads directly to the famous declaration cogito, ergo sum. — Wayfarer

As I said in another comment, I'm not interested in a textual exegeses of Descartes, the argument is only inspired by some things that he says, but it doesn't mean that it fits 100% the text (and also you are looking at the wrong section of the text, and the cogito argument has nothing to do with this topic, but let's put Descartes aside).

Wayfarer

I think the other point that needs to be made is to consider Descartes' motives for this argument. Descartes was the first subject taught in the philosophy course I enrolled in, as 'the first modern philosopher.' So a large part of his motivation was to do what we would now colloquially refer to as a 'reset' - he wanted to sweep the board clean of scholasticism, essence and substance, and all of the machinery of medieval philosophy. It was an exercise which purportedly allowed him to start from a clean slate and a set of fundamental ideas - indeed, 'clear and distinct ideas', as he said. But as I now see you're not interested in Descartes, that anyway I've quoted the wrong section of Descartes (for which no citation has been provided) in any case, then I'll let you carry on with whatever topic it is you think you're interested in.

Michael

But still, your argument still seems to beg the question and assume that our experiences are veridical, whereas one of the sceptics claims is that they might not be. So unless you can show that our experience are veridical, your argument seems to miss the point.

Agustino

The problem I see is that it is still feasible that the waking state, the state of presumed normality, is still a consistent illusion. It would be logically possible that, at the time of death, one is suddenly roused as if from a sleep, to a mode of existence that one had never guessed at while alive, but which now is obvious once again; one might immediately begin to forget the life you had just lived, in the same way as forgetting dreams that you have just had woken from. — Wayfarer

Sure, it's logically possible that life - by analogy - has the structure of a dream, but we really have no reason to suppose so (at least in our ordinary consciousness). Lacking a reason to suppose so means that doubting it would be irrational. Much more, within the waking state we come to know about the distinction between awake and dreaming, hence if even being awake is dreaming, then we have destroyed the notion of awake - and hence the notion of dreaming, which also depends on the notion of being awake. Language is rendered meaningless by such skepticism.

Fafner

I've already addressed it. It's epistemic luck, not knowledge. Unless you can distinguish between a veridical and a non-veridical experience (or between a real painting and a forgery) then you can't know that your experiences are veridical (or if the painting is real). — Michael

The problem with the epistemic luck reply is the same. You cannot say that a belief is an instance of epistemic luck as opposed to knowledge without antecedently knowing the objective background against which the belief was formed. So you cannot know that my belief that I see a tree is merely lucky if you don't know whether in fact there is a tree in front of me (and perhaps also whether my ability to detect trees in general is genuinely reliable). But of course the skeptic doesn't claim to know that there are in fact no trees (if he wished to prove that my believe is merely lucky), so it would be of little help to appeal to epistemic luck on his behalf.

Michael

Sure, it's logically possible that life - by analogy - has the structure of a dream, but we really have no reason to suppose so (at least in our ordinary consciousness). Lacking a reason to suppose so means that doubting it would be irrational. Much more, within the waking state we come to know about the distinction between awake and dreaming, hence if even being awake is dreaming, then we have destroyed the notion of awake - and hence the notion of dreaming, which also depends on the notion of being awake. Language is rendered meaningless by such skepticism. — Agustino

This is just pedantry. You can always accept the meaningful distinction between wakefulness (experiences of an external world) and dreaming (experiences not of an external world) but claim that those experiences which we claim to be of wakefulness aren't actually so.

Or it could be that the distinction between wakefulness and dreaming is just one of quality, and that the claim that wakefulness is the experience of an external world is in fact false.

Agustino

This is just pedantry. You can always accept the meaningful distinction between wakefulness (experiences of an external world) and dreaming (experiences not of an external world) but claim that those experiences which we claim to be of wakefulness aren't actually so. — Michael

No you can't. Meanings are developed based on experience. If you categorize the experience of being awake as being equivalent to the experience of dreaming, then the meaning of awake and dreaming collapses. To avoid that collapse you'd need to have - in your experience - some other state in reference to which being awake is a dream. Lacking any such experience would render your terms meaningless.

Michael

So you cannot know that my belief that I see a tree is merely lucky if you don't know whether in fact there is a tree in front of me (and perhaps also whether my ability to detect trees in general is genuinely reliable). But of course the skeptic doesn't claim to know that there are in fact no trees (if he wished to prove that my believe is merely lucky), so it would be of little help to appeal to epistemic luck on his behalf. — Fafner

The claim is that if the experience isn't veridical then your belief is false and that if your experience is veridical then your belief is just lucky. So the sceptic doesn't need to claim that there are or aren't any trees. He just argues that either way there isn't knowledge.

To be able to get beyond luck to actual knowledge you must somehow know that your experience is veridical, which according to the sceptic isn't possible.

Michael

No you can't. Meanings are developed based on experience. If you categories the experience of being awake as being equivalent to the experience of dreaming, then the meaning of awake and dreaming collapses. — Agustino

They're not equivalent. They're different. But neither are experiences of an external world.

Agustino

They're not equivalent. They're different. But neither are experiences of an external world. — Michael

If the meaning of awake no longer has a reference in experience, then that meaning has been destroyed. If you say that being awake is dreaming, then you have short-circuited your language.

Michael

If the meaning of awake no longer has a reference in experience, then that meaning has been destroyed. If you say that being awake is dreaming, then you have short-circuited your language. — Agustino

You seem to be conflating. I'll set it out more clearly.

1. We have experiences of type A and experiences of type B.
2. We refer to experiences of type A as "wakefulness" and experiences of type B as "dreaming".
3. We claim that wakefulness is the experience of an external world and that dreaming is the experience of an imaginary world.

There are two ways for the sceptic to approach this. They can either claim that "wakefulness" and "dreaming" are defined by their referents, in which case our claim that wakefulness is the experience of an external world is false, or they can claim that they are defined as being the experience of an external and imaginary world respectively, in which case both types of experience fall under the umbrella term "dreaming" (even though they have other properties to distinguish them).

Nothing about this "destroys meaning" or "short circuits" language.

But again, this is just pedantry. The sceptic's claim is simply that we can't know that our experiences are of an external world, regardless of what we call them or think of them. You can't counter this by pointing to a dictionary.

Answering the Skeptic

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