Knowledge and Reality Scepticism Lecture two: The Commonsense Response Ema Sullivan-Bissett Feedback and Advice hour: Thursdays, 11:30, office A/101 (weeks 2–6)

G. E. Moore (fun fact) ‘G. E. Moore ( ) (who hated his first names, ‘George Edward’ and never used them—his wife called him ‘Bill’)’ (Baldwin 2004).

A Word from Kant ‘It still remains a scandal to philosophy... that the existence of things outside of us... must be accepted merely on faith, and that, if anyone thinks good to doubt their existence, we are unable to counter his doubts by any satisfactory proof’ (Kant CPR b xxxix, cited in Moore 1959: 127). It ‘falls properly within the province of philosophy’ to discuss what proof can be given of ‘the existence of things outside of us’ (Moore 1959: 127).

Some important(?) distinctions Presented in space. To be met with in space. External to our minds.

Presented in Space ‘I took the trouble to cut out a piece of white paper a four-pointed star, to place it on a black ground, to ‘look steadfastly’ at it, and then to turn my eyes to a white sheet of paper: and I did find that I saw a grey patch for some little time – I not only saw a grey patch, but I saw it on the white ground, and also this grey patch was roughly the same shape as the white four- pointed star at which I had ‘looked steadfastly’ just before – it was also a four-pointed star. I repeated this simple experiment successfully several times’ (Moore 1959: 131).

After Images ‘Now each of those grey four-pointed stars, one of which I saw in each experiment, was what is called an ‘after-image’ or ‘after-sensation’; and can anybody deny that each of these after-images can be quite properly said to have been ‘presented in space’? I saw each of them on a real white background, and, if so, each of them was ‘presented’ on a real white background. But although they were ‘presented in space’ everybody, I think, would feel that it was gravely misleading to say that they were ‘to be met with in space’ (Moore 1959: 131).

After Images The cut out star on the piece of paper was to be met with in space – this marks an important difference between it and the after-images of stars. The latter are not to be met with in space. For something to be met with in space, it needs to be the case that ‘there are conditions such that any one who fulfilled them might, conceivably, have ‘perceived’ the ‘thing’ in question – might have seen it, if it was a visible object, and felt it, if it was a tangible one, have heard it, if it was a sound, have smelt it, if it was a smell’ (Moore 1959: 132).

After Images So the white four-pointed paper star meets this condition for being met with in space because if someone had been in the room at the time, with normal eyesight and a normal sense of touch, she would have seen and felt the star. Take though any one of the after image stars: ‘it is not conceivable that anyone besides myself should have seen any one of them. It is, of course, quite conceivable that other people, if they had been in the room with me at the time, and had carried out the same experiment which I carried out, would have seen grey after-images very like one of those which I saw: there is no absurdity in supposing even that they might have seen after-images exactly like one of those which I saw. But there is an absurdity in supposing that any one of the after- images which I saw could also have been seen by anyone else: in supposing that two different people can ever see the very same after- image’ (Moore 1959: 132).

Seeing Double If I were suitably intoxicated, I might see two of my friend Sam dancing in The Willow. And it makes sense to say that both Sams are presented in space. But it is not right to say that both Sams are to be met with in space, because if both were: ‘it would follow that somebody else might see the very same two images which I see; and, though there is no absurdity in supposing that anyone else might see a pair of images exactly similar to the pair which I see, there is an absurdity in supposing that anyone else might see the same identical pair’ (Moore 1959: 133).

Pain When I have a pain in my knee, I feel that pain to be in a part of my body, namely, my knee. That pain is presented in space – it is, after all, felt to be in a particular region of space. However, pains are not the sorts of thing which can be met with in space, for the same reason as after-images and double images are not to be met with in space: ‘It is quite conceivable that another person should feel a pain exactly like the one which I feel, but there is an absurdity in supposing that he could feel numerically the same pain which I feel. And pains are in fact a typical example of the sort of ‘things’ of which philosophers say that they are not ‘external’ to our minds, but ‘within’ them. Of any pain which I feel they would say that it is necessarily not external to my mind but in it’ (Moore 1959: 133).

Met with in Space As examples of such things Moore gives ‘the bodies of men and of animals, plants, stars, houses, chairs, and shadows’ (Moore 1959: 157). A thing’s being such that it is to be met with in space follows from that thing’s existing, so from the claim ‘plants exist’ it follows that ‘there are things to be met with in space’ (Moore 1959: 137). So the proposition that there is at least one thing to be met with in space follows from: ‘There is at least one star’, from ‘There is at least one human body’, from ‘There is at least one shadow’, etc.

External Things From the proposition that there is at least one ‘thing’ of that kind there follows the proposition that there is at least one thing external to our minds. e.g., from ‘There is at least one star’ there follows not only ‘There is at least one thing to be met with in space’ but also ‘There is at least one external thing’, and similarly in all other cases’ (Moore 1959: 144).

Pairs of Things So, for all kinds of ‘things’, if there is a pair of things, it follows that there are two things outside of us. So if Moore can prove that two things exist, he will have proved that there are at least two things outside of us: ‘if I can prove that there exist now both a sheet of paper and a human hand, I shall have proved that there are now ‘things outside of us’; if I can prove that there exist now a shoe and sock, I shall have proved that there are now ‘things outside of us’, etc.; and similarly I shall have proved it, if I can prove that there exist now two sheets of paper, or two human hands, or two shoes, or two socks, etc. […] Cannot I prove any of these things?’ (Moore 1959: 145).

The Proof ‘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 others ways: there is no need to multiple examples’ (Moore 1959: 145–6). This proof is ‘a perfectly rigorous one; and […] it is perhaps impossible to give a better or more rigorous proof of anything whatever’ (Moore 1959: 146).

Three Conditions on Rigorous Proofhood 1.The premise which is adduced as proof of the conclusion is different from the conclusion it was adduced to prove. 2.The premises adduced were ones which were known, and not merely believed. 3.The conclusion follows from the premises.

The Proof P. Here is one hand, and here is another. C. Two human hands exist at this moment.

Condition One 1.The premise which is adduced as proof of the conclusion is different from the conclusion it was adduced to prove. Moore’s conclusion: ‘Two human hands exist at this moment’. This is different from his premise: ‘Here is one hand, and here is another’. Different because they have different truth conditions – the conclusion can be true without the premise being true. The premise asserts much more than the conclusion, and so condition one is met.

Condition Two 2. The premises adduced were ones which were known, and not merely believed. ‘I certainly did at that moment know that which I expressed by the combination of certain gestures with saying the words ‘Here is one hand and here is another’ (Moore 1959: 146). ‘How absurd it would be to suggest that I did not know it, but only believed it, and that perhaps it was not the case! You might as well suggest that I do not know that I am now standing up and talking – that perhaps after all I’m not, and that it’s not quite certain that I am!’ (Moore 1959: 146–7).

Condition Three 3. The conclusion follows from the premises. ‘[I]t is quite certain’, that it did: ‘This is as certain as it is that if there is one hand here and another here now, then it follows that there are two hands in existence now ’ (Moore 1959: 147).

Moore’s proof meets all three conditions for a rigorous proof. And so: ‘I did, then, just now, give a proof that there were then external objects; and obviously, if I did, I could then have given many other proofs of the same sort that there were external objects then, and could now give many proofs of the same sort that there are external objects now ’ (Moore 1959: 147).

The Brain in a Vat Argument Modus Ponens (S1) If I do not know that I am not a brain in a vat then I do not know that I have two hands. (S2) I do not know that I am not a brain in a vat. (SC) I do not know that I have two hands. P → Q P Q

Moore’s Argument Modus Tollens P → Q ~Q ~P (S1) If I do not know that I am not a brain in a vat then I do not know that I have two hands. (S2) I know that I have two hands. (SC) Therefore, I know that I’m not a brain in a vat. ‘Baby you’re the sexiest inference form around. You set them up and then you tear them down. You’re valid but a little bit dangerous. You’re not prissy like that modus ponens’ ‘Modus Tollens’ – The Monads.

The G. E. Moore Shift Logical manoeuvre from modus ponens to modus tollens. (S1) If I do not know that I am not a brain in a vat then I do not know that I have two hands. (S2) I do not know that I am not a brain in a vat. (SC) I do not know that I have two hands. (M1) If I do not know that I am not a brain in a vat then I do not know that I have two hands. (M2) I know that I have two hands. (MC) Therefore, I know that I’m not a brain in a vat.

BREAK

There’s something wrong with this argument, But I don’t know what it is. The denial of the conclusion is more plausible than the conjunction of the premises. There must be something here to reject; Something’s gotta give. I’m gonna do the G.E. Moore shift. I wanna do the G.E. Moore shift. Come on the G.E. Moore shift. I wanna do the G.E. Moore shift. I can’t believe you think that that’s true. How can you accept the consequence of that view? It’s obvious something here ain’t right; Use a little common sense. It’s obvious something here ain’t right; Something’s gotta go.

Unsatisfying ‘Once we are familiar with the philosophical problem of our knowledge of the external world, I think we immediately feel that Moore’s proof is inadequate’ (Stroud 1984b: 86). ‘The greater part of the essay is devoted to exasperatingly slow ruminations on what it means to describe objects as “external”, or “outside our minds” or “presented in space” or “to be met with in space”. Nothing particularly consequential emerges. And the actual ‘Proof’—which everyone on first reading feels blatantly begs the question—is confined to the last few pages’ (Wright 2002: 30). ‘Moore’s proof strikes (almost all of) us as an obviously annoying failure, and does so immediately, on first encounter’ (Coliva 2008: 235).

Condition Two 2. The premises adduced were ones which were known, and not merely believed. ‘I certainly did at that moment know that which I expressed by the combination of certain gestures with saying the words ‘There is one hand and here is another’ (Moore 1959: 166). ‘How absurd it would be to suggest that I did not know it, but only believed it, and that perhaps it was not the case! You might as well suggest that I do not know that I am now standing up and talking – that perhaps after all I’m not, and that it’s not quite certain that I am!’ (Moore 1959: 166–7)

Moore Begs the Question ‘Of course, Moore can’t offer a deductive proof that he has a hand, from premises of whose truth he is more certain, and which the skeptic will accept. But it seems that his position is even worse than that. For Moore doesn’t seem ready or able to offer any considerations at all in favor of the claim that he has a hand—even defeasible, ampliative considerations—without begging the question against a skeptic who refuses at this stage of the dialectic to grant the existence of the external world. This is why Moore’s “proof” strikes us as so unsatisfactory: he hasn’t offered any non-question-begging reasons to believe his premises. Yet Moore claims he can know these premises to be true. He can know them to be true, though he has no non-question-begging arguments to offer in their support’ (Pryor 2000: 518).

Moore Doesn’t Prove his Premise We might push the question begging charge by pointing out that Moore does not prove his premise. The argument is valid, but without proving the premise the sceptic will remain unmoved.

Moore Doesn’t Prove his Premise P. Here is one hand, and here is another. C. Two human hands exist at this moment. Proof Principle: If you cannot prove that p, you cannot know that p. Proof for this premise needed!

Moore Denies Proof Principle ‘If I had proved the [proposition] which I used as [a premise] in my [proof], then they would perhaps admit that I had proved the existence of external things’ (Moore 1959: 169). ‘How am I to prove now that ‘Here’s one hand, and here’s another’? I do not believe I can do it. In order to do it, I should need to prove for one thing, as Descartes pointed out, that I am not now dreaming. But how can I prove that I am not? I have, no doubt, conclusive reasons for asserting that I am not now dreaming; I have conclusive evidence that I am awake: but that is a very different thing from being able to prove it’ (Moore 1959: 169).

A Different Kind of Dogmatism

James Pryor’s Dogmatism Two ways of ‘grappling with [the] skeptic’: 1.Ambitious anti-skeptical project: play the skeptic’s game, and win – establish that we can know propositions such as ‘there is a hand’ using premises allowed by the skeptic. ‘The prospects for this ambitious anti-skeptical project seem somewhat dim.’ 2.Modest anti-skeptical project: establish to our satisfaction (not the sceptic’s) that we can justifiably believe and know propositions such as ‘there is a hand’ – we do not need use only premises allowed by the sceptic. (Pryor 2000: 517).

Two Dogmas 1.Dogmatism about perceptual knowledge: justification from having an experience of p can sometimes give you knowledge that p. 2.Dogmatism about perceptual justification: when you have an experience that p, you are justified in believing that p, and this justification does not rest on any other justification for p. No other beliefs are required for this justification to be in place.

The Sceptical Challenge Sceptical arguments are put in terms of knowledge, concluding that we cannot have knowledge of the external world. Pryor’s dogmatism aims at the claim that we can have justified beliefs about the external world, and so his target sceptic needs to be characterised.

Sceptical Principle about Knowledge SPK: ‘If you’re to know a proposition p on the basis of certain experiences or grounds E, then for every q which is “bad” relative to E and p, you have to be in a position to know q to be false in a non-question- begging way—i.e., you have to be in a position to know q to be false antecedently to knowing p on the basis of E’ (Pryor 2000: 528).

Sceptical Principle about Justification SPJ: ‘If you’re to have justification for believing p on the basis of certain experiences or grounds E, then for every q which is “bad” relative to E and p, you have to have antecedent justification for believing q to be false— justification which doesn’t rest on or presuppose any E- based justification you may have for believing p’ (Pryor 2000: 531). You need antecedent justification to believe you’re not a brain in a vat for any perceptual belief to be justified.

Perceptual Justification Scepticist about perceptual justification: In order to be justified in believing that there is a cat on the mat (on the basis of perceiving there to be a cat on the mat), you need antecedent reason to believe that you’re not a brain in a vat. Dogmatist about perceptual justification: ‘when you have an experience as of p ’s being the case, you have a kind of justification for believing p that does not presuppose or rest on any other evidence or justification you may have’ (Pryor 2000: 532).

The Dogmatist and the Sceptic SPJ: ‘If you’re to have justification for believing p on the basis of certain experiences or grounds E, then for every q which is “bad” relative to E and p, you have to have antecedent justification for believing q to be false— justification which doesn’t rest on or presuppose any E- based justification you may have for believing p’ (Pryor 2000: 531). If the dogmatist about perceptual justification is right, SPJ is false. So is dogmatism about perceptual justification right?

Yes! If you have an experience of p, of there being a cat on the mat, you have immediate prima facie justification for believing that p, that there is a cat on the mat. Providing you have no defeaters for this prima facie justification, you have ‘all things considered justification for your belief’ (Pryor 2000: 535).

Experience and Sceptical Scenarios Your experience that p gives you immediate prima facie justification for believing that p. Your experience that p does not give you immediate prima facie justification for believing that you are in any of the sceptical scenarios.

Experience and Sceptical Scenarios ‘An experience as of there being hands seems to justify one in believing there are hands in a perfectly straightforward and immediate way. When asked, “What justifies you in believing there are hands?” one is likely to respond, “I can simply see that there are hands.” One might be wrong: one might not really be seeing a hand. But it seems like the mere fact that one has a visual experience of the phenomenological sort is enough to make it reasonable for one to believe that there are hands. No premises about the character of one’s experience – or any other sophisticated assumptions – seem to be needed’ (Pryor 2000: 536). ‘I say, let’s take these intuitive appearances at face value. Let’s say that our perceptual beliefs in these propositions are indeed justified in a way that does not require any further beliefs or reflection or introspective awareness. They have a kind of justification which is immediate, albeit defeasible’ (Pryor 2000: 536).

The ‘Anti-Skeptical Punch’ The dogmatist about perceptual justification is going for a modest claim, but it is one which still has ‘anti-skeptical punch’. If he is right, I can be justified in believing that there is a cat on the mat, even if I am unable to give any non-question begging argument for there being a cat on the mat (even if I can’t give justification antecedent to my experience of there being a cat on the mat for the claim). I can be justified in believing that there is a cat on the mat, even if I have no antecedent justification for believing that I’m not a brain in a vat.

Next Contextualism Semantic Externalism Seminars: –Do the reading! –Come with at least one question per topic.

References Baldwin, Thomas 2004: ‘George Edward Moore’ in The Stanford Encyclopaedia of Philosophy, available online at Coliva, Annalisa 2008: ‘The Paradox of Moore’s Proof of an External World’. The Philosophical Quarterly. Vol. 58, no. 231, pp. 234–43. The Monads 1999: ‘Modus Tollens’. Moore, George Edward 1959: ‘Proof of an External World’, in his Philosophical Papers, London: Allen & Unwin; pp. 127–51. Pryor, James 1999: ‘What’s Wrong with Moore’s Argument?’, Philosophical Perspectives 13: Pryor, James 2002: ‘The Skeptic and the Dogmatist’. Nous. Vol. 34, pp. 517–49. Stroud, Barry 1984: ‘The Problem of the External World’ in his The Significance of Philosophical Scepticism. New York : Oxford University Press Wright, Crispin 2002: ‘(Anti-)Sceptics Simple and Subtle: G.E.Moore and John McDowell’, Philosophy and Phenomenological Research. Vol. 65, pp. 330–48.