Presumably not so much for someone who actually believes it. — Wayfarer

That would be called faith, not a fact, would it not? Or even imagination, if we moved God from heart to head, depending on the person in question.

Have a look back at my first one or two responses to this thread, about the purported Indian origins of Greek scepticism. Buddhism is, in most people’s reckoning, religious, but it doesn’t emphasis belief, in the same way that Christianity does. I sometimes wonder if one of the defining characteristics of Christianity is the fact that belief in the supernatural is required, in that the Resurrection is plainly a supernatural event, and you have to believe in that at the get-go.

Whereas, Buddhism starts with the observation that ‘life is dukkha (suffering or unsatisfactory)’ and then works from there through the ‘causes of dukkha’ (which is the subject of the rest of the teaching). However Buddhism also accommodates the supernatural (usually expressed as ‘transmundane’ or some such, so as to avoid the boo word ‘supernatural’.) Whether that belief is fundamental to the religion, is in fact a large bone of contention between those who wish to present it in purely naturalistic terms (like Stephen Bachelor and the ‘secular Buddhist’ movement) as distinct from the traditional exponents, for whom the ‘transmundane’ nature of the Buddha is accepted from the outset (along with acceptance of the miraculous powers, siddhi, that are understood to be possessed by the Buddhas and bodhisattvas.)

Thorny questions, all.

Anyway to get roughly back on point, the attitude that ‘only facts matter’ is, in simple terms, the attitude of positivism. The question ‘what do facts mean’ is the domain of hermeneutics, interpretation, ‘the meaning of things’. And the assertion that things have no meaning is precisely one of the customary claims of positivism; the view that the universe is essentially devoid of meaning being one of the ideas associated with modernity and modern science. But the belief in the ‘value-free’ nature of the Universe is one that most modern forms of scepticism will implicitly endorse, on the basis that scientific naturalism reveals what the world is really like when shorn of the accretions of belief. Which basically amounts to the view that, only scientifically-validated factual claims have truth value; which is, again, ultimately, a form of positivism, like it or not.

The metaphor I like is a tool box. When you have something to do, you pull out the tool that works best. — T Clark

So do you have a banana-fudger in your tool box at home? It's a tool that I just made up a bit like a feather tied to stick and painted green. It's for directing ants away from a lawn. No? Of course you don't because it's useless and something I just made up, you have tools in your toolbox that not only actually do a job that is needed but which you have personally experienced actually being useful. In a world without screws a screwdriver is just a useless piece of metal. The difference between realism and all other metaphysics is that realism is the metaphysical view we're born with. Kids play catch, they expect the laws of physics to work, they act as if the laptop (to borrow another example on this thread) is going to be the same laptop when they open their eyes as it was a minute ago., they act as if effect followed cause, and investigate cause using their senses fully anticipating that this will yield fruitful results. All other metaphysics are something people made up. That doesn't make them wrong, I think we've firmly established it would be impossible to prove that, but it does mean that, like the banana-fudger, they should not just be automatically stored alongside our native realism as an equally viable option, they must prove their worth.

Personally I'm a pragmatist in the tradition of Pierce, so I'm not going to claim that realism shows us the 'truth' of the world, nor that our senses can't be deceived, but what I do take issue with is the suggestion that because of this I must be open to Descarte's brand of dualism, or Berkely's solipsism, or some priest's religion. There are 7 billion people on the planet more who have ever lived and they all will have some opinion about the way the world is, the only way I could respond open-mindedly to all of them is to give each of them one ten millionth of my time to consider their views, that gives them all less than a second each. So if someone says to me I shouldn't be so dismissive of Platonic idealism, I could quite reasonably answer that I have given it a second's thought which is it's fair consideration given all the other equally viable ideas I must consider if I'm to be truly open-mined.

What is often labelled as open-mindedness is usually just an excuse for idolatry.

Wouldn't realism being the most likely inference from experience qualify? We don't need to posit demons or computer simulations. We can just say the things in perception continue to exist while not being perceived, along with other things we can't perceive, but we can infer from things perceived, like elementary particles.

That goes well with science, which doesn't infer demons or simulations or brains in vats, but does infer plenty of unobservables that make good sense of what is observed, along with object permanence. — Marchesk

The inference you suggest would be just the kind of things which is needed, but what makes Realism a better explanation of experience than the evil demon hypothesis or a brain-in-vat hypothesis? In fact, why is such an explanation even necessary? Isn't it ontologically simpler to suppose that things only exist when perceived?

In the Kantian approach, sentience holds within it aprior understanding of causation in the abstract, thereby facilitating belief that things causally continue to be even when not perceived or thought of. — javra

I am not sure what this argument really is. I am supposed to have a 'prior understanding of causation in the abstract'. Does that mean that I innately have a concept of causation? If so, how does that show that the belief that things exist unperceived has a reliable source? (1) I am not sure what relevance causation has to whether things exist unperceived, and (2) even supposing it has relevance, it does not follow from the fact that I have an innate concept of X, that X is a correct description of the world, unless you are supposing that all innate concepts are reliable, but that's empirically false.

In a strictly evolutionary approach, were intellect-endowed sentience (sapient or otherwise) to not have evolved unconscious aptitudes for discerning how things continue to be when not perceived or thought about, the given sentience would perish; lifeforms would either be, for example, quickly killed by stealthy predators or predators would quickly starve to death. — javra

Is it true that if we didn't believe that things continue to exist when unperceived we would die? I am inclined to deny it. Could you give an example in which it is clearly true?

In addition, let's suppose that evolution gave us this belief. Evolution just 'programmed' this belief into our minds for the sake of survival. Is that a reliable source for belief? Couldn't all kinds of beliefs be useful for survival and yet false? The belief that tigers have submachine guns hidden in their fur would be useful for survival. It would sure keep me away from tigers, but it is obviously false.

PA

The difference between realism and all other metaphysics is that realism is the metaphysical view we're born with. Kids play catch, they expect the laws of physics to work, they act as if the laptop (to borrow another example on this thread) is going to be the same laptop when they open their eyes as it was a minute ago., they act as if effect followed cause, and investigate cause using their senses fully anticipating that this will yield fruitful results. All other metaphysics are something people made up. That doesn't make them wrong, I think we've firmly established it would be impossible to prove that, but it does mean that, like the banana-fudger, they should not just be automatically stored alongside our native realism as an equally viable option, they must prove their worth. — Inter Alia

Lots wrong here. No, children are not born with realism. They are taught it. They learn it. Parents don't say "cogito ergo sum." They say "oopsie, baby fall down." They don't expect the laws of physics to work. Why do you think peek-a-boo works so well? It's because young children don't know that something is still there when they cover their eyes. Children play catch, but they also go to church. Is that proof for the existence of god?

All metaphysics are made up. Metaphysics isn't true or false, it's fashionable or unfashionable. Pretty or ugly. Approved or prohibited. Clever or boneheaded. Useful or not useful. And all in particular situations, not for everything always.

One of the real values of the other metaphysical views is that they offer a tool to help see things we don't see because we are blinded by realism.

It's because young children don't know that something is still there when they cover their eye — T Clark

Some philosophers, I believe following Bertrand Russell, have defended Realism by saying that it is an instinctive believe 'built in' to all of us and which we cannot help but have (Javra has a very similar argument above). I've never been too sure what to make of that argument. What you say here points out that this claim is obviously false. Your point is so obvious that I can't believe I didn't see it. My niece is at just that stage in childhood right now, and yet I still didn't pick up the philosophical relevance.

Thanks for this.
PA

This comes back to my point about the multiplicity of alternative metaphysics, you're both using the 'obviousness' of the fact that every single child is surprised by 'peek-a-boo' but then trying to establish an argument that it is far from obvious why every single child in every single culture in the world that has ever been recorded goes on act as if the parent continues to exist after they re-open their eyes. Are you suggesting that every single parent without exception just happens to indoctrinate their child with realism despite many equally reasonable alternatives, no-one in all of history has ever decided to teach their child solipsism and had the child obediently grow up to be solipsist?

I'm not suggesting that we're born with all the 'knowledge' of realism, that is provided us by sense data,but the evidence seems to be overwhelming that we are pre-programmed to interpret the sense data we receive through Realism, I literally can't think of a single example of any grown-up child in the world who genuinely still thinks their parent might actually have ceased to exist just because they can't see them any more. Is the teaching of realism to our children really that successful, I wish I could teach mine manners with the same degree of success.

I don't suppose that every single child in the history of the earth is surprised by peek-a-boo, no. But, as I said, many Realists put forward, as a reason for thinking that Realism is true, the claim that Realism is an instinctive belief pre-programmed into us. But the fact is that many children are surprised by peek-a-boo. Many children do seem to think that you cease to exist just because they can no longer see you (it is hard to tell whether they really think this, since you can't ask children at that stage what they think, and when they get to the stage where you could sensibly ask them, they won't remember what they thought!). I am not suggesting that all think this way, but many do. What this shows, is that Realism is not 'built in', but is in fact learnt.

And yes, I suppose that the teaching of Realism to children is incredibly successful. Why don't children rebel from their teaching and reject Realism? Well, W.T Stace did, as did the whole Idealist tradition. No doubt they are a minority of the human race. I think the more satisfying answer is that people don't normally bother to question things which make no practical difference, unless there is good evidence that it is false. We are all taught as children that Santa delivers our presents on Christmas, and I believed this without question until I was told by numerous people that it was false, I saw my mother bringing my presents into the house, I was 'teased' by older children about how Santa isn't real. If none of that had happened, I would have just gone on believing it, since it made no practical difference to me at that time, whether my mother or Santa gave me the gifts. There was just no reason to question it.

The same is true of Realism, we are all taught as children that things exist unperceived - or this is implied by other things we are taught - and we all swallow it just like we swallow the Santa story. We never question Realism because it makes no practical difference whether it is true or not, and there is no evidence against it. This, together with the fact that it is very easy, if you don't do philosophy, to mistakenly think that you can 'just tell' by sense perception that Realism is true, mean that Realism goes unquestioned for the majority of people.

You can't teach your children manners as effectively because it often takes excessive effort to be polite when we are in a bad mood, or when being rude would be much more efficient for our purposes.

PA

Sorry for the double post, but perhaps I should add to the above that most people have never even noticed that Realism is something which they believe, although they would accept it if you brought it up. Until you do philosophy, it is very easy to completely fail to notice your own Realism or that there is an alternative. That is another reason why the teaching goes so smoothly.

PA

I understand the logic of what you're saying, but it isn't very convincing, it's a story that makes sense - realism is like santa claus, we don't question it until we have to - but it's not one that is necessary. The idea that realism is something literally all children follow from the moment they have enough sense data to process to at least until early adulthood is something which is easily explained by the fact that we are pre-programmed to interpret the world that way, it doesn't require another explanation, no conspiracy of indoctrination, no almost miraculously successful teaching is needed.

Aside from this (as I recognise your interpretation is perfectly reasonable even though I don't agree with it), this doesn't then solve the problem I mentioned in my previous posts about the multiplicity of alternatives. I think we can all agree that one cannot prove realism, nor even provide any sound argument as to why it is 'better' than any other metaphysical view, for the educated, philosophically mined adult. But this them means that all metaphysical views have an equal claim, Plato's, Kant's, my Grandma's whcih leads to what i think is the bigger question (bigger than whether Realism has a claim to being the 'default' position) which is what do we do about it? What should one actually do about the fact that realism cannot be proven yet we all seem to have grown up with it?

We can't just discard it because it can't be proven (that's true of all metaphysics), we can't check out all the alternative and give them their fair crack at convincing us (there are simply vastly too many alternatives to give them more than a few moment's thought each). Maybe we should just be open-minded to the ones we hear about, but that seems a bit defeatist and passive for my liking. That's basically where I come away from the anti-realists as a group, I'm not sure what value it has as an approach. I'm not sure what 'things' we're seeing that are of any actual use.

Are you suggesting that every single parent without exception just happens to indoctrinate their child with realism despite many equally reasonable alternatives, no-one in all of history has ever decided to teach their child solipsism and had the child obediently grow up to be solipsist? — Inter Alia

A lot of people are not what you call a realist. There are a lot of world views out there that you, and maybe I, would consider odd. It's always surprised me that people I consider very conventional have unconventional ideas about the world. My neighbor and friend is a 65 year old accountant. Very intelligent, mature, sophisticated, and conventional in the way he lives and in many of his ideas. He believes in reincarnation. Beyond that, I think very few people actually have world views that you would consider "realist." In the US, something like 45% of adults do not believe in evolution. More than 80% believe in God.

I think your adamant insistence reflects a failure of imagination and observation.

The same is true of Realism, we are all taught as children that things exist unperceived - or this is implied by other things we are taught - and we all swallow it just like we swallow the Santa story. We never question Realism because it makes no practical difference whether it is true or not, and there is no evidence against it. This, together with the fact that it is very easy, if you don't do philosophy, to mistakenly think that you can 'just tell' by sense perception that Realism is true, mean that Realism goes unquestioned for the majority of people. — PossibleAaran

I think you're buying into PossibleAaran's way of looking at this. You're trying to refute his argument from inside. The real problem with his argument comes from the outside, as I've tried to show in my other posts. To reiterate - most people are not realists. I wonder if anyone really is. That doesn't mean we don't use realism when it makes sense, or even when it doesn't.

Sorry for the double post, but perhaps I should add to the above that most people have never even noticed that Realism is something which they believe, although they would accept it if you brought it up. Until you do philosophy, it is very easy to completely fail to notice your own Realism or that there is an alternative. That is another reason why the teaching goes so smoothly. — PossibleAaran

This is a realist argument. You're using a realist argument to help PossibleAaran defend realism.

I don't deny that adults have non- or anti-realist views, to do so in the face of overwhelming evidence would indeed be absurd. I'm talking entirely about the claim that Realism is the 'default' view of the biological creature that we are. The evidence I'm forwarding to support that view is that as we grow up all the sense data we accrue seems to be automatically processed in that way. I know of plenty of kids who reject santa claus, fairies, the industrial-capitalist model. I know of no kids who decide the laws of physics do not apply to them at the age of five, who when a ball is thrown to them they have no good reason to trust their instinctive estimate of where it will land. I know of no nine year olds who will naturally consider the laptop not exist when the shut their eyes and only pop back into existence again when they open them.

I think you may be under-defining Realism. The fact that people believe in something they haven't yet sensed is different to them believing in something other than what they sense.

I think you may be under-defining Realism. The fact that people believe in something they haven't yet sensed is different to them believing in something other than what they sense. — Inter Alia

You and I have started repeating our positions and responses without adding anything new. I can't think of anything new to say.

Beyond that, I think very few people actually have world views that you would consider "realist." In the US, something like 45% of adults do not believe in evolution. More than 80% believe in God. — T Clark

That doesn't make you non-realist. That just means you think reality is different than the naturalistic version. Metaphysical realist means a belief in a mind-independent world. I grew up Christian, and most of those folks believed God created a material world that may or may not be compatible with what scientists say. I don't recall anyone espousing Berkeley's idealism, other than reference to Christian Science or gnosticism, which was considered heretical.

The problem with scepticism is that doubt only makes sense if it's limited, because doubt about one thing requires a reason to doubt, which presupposes the truth of something else, usually some other perception. Doubt can't exist in a vacuum, in suspension, without any presuppositions whatsoever.

The cash value of doubting is checking, which usually involves some further action. If you doubt whether a perception is illusory, then you do something like shift position, ask someone else, etc., etc. If you doubt the results of a calculation, you re-do the calculation, ask someone else to check it, etc., etc.

Generalized doubt, Cartesian doubt, or global scepticism, is fundamentally incoherent, especially if it's based on merely imagining that things could be different than they appear to be (imagining alternative "logical possibilities"). To doubt, you need a reason to doubt, not just a contextless wondering whether things might be different than you think they are.

One certainly imagines other possibilities when one is doubting, because one uses those alternative possibilities to formulate plans of action for checking; but the doubt is resolved by action in one way or another, it doesn't just stop at the mere imagining of alternative "logical possibilities."

And at some point, one or another of the results of the checking actions aren't doubted.

IOW, doubt is a phase of cognition that alternates with bits of truth acceptance, it can't coherently be elevated to a permanent cognitive stance that doubts everything.

To doubt, you need a reason to doubt, not just a contextless wondering whether things might be different than you think they are. — gurugeorge

Right, so for example you can imagine this is all a dream, but then we understand the distinction between dreaming and waking because we spend part of our time awake. But what does it mean if we were only dreaming the entire time?

Just like we can imagine taking a brain and putting it in a vat, but what would it actually mean for us to be brains in vats?

I understand what a simulation is because of the real things it's simulating, but what if everything was simulated? Then what does "simulated" mean?

That doesn't make you non-realist. That just means you think reality is different than the naturalistic version. — Marchesk

Indeed, that's what I meant by 'under-defining' but you explained it much more clearly, thanks.

The key question is not what we should doubt, but what doubting looks like. How would one tell that I doubted the entirely physical nature of existence, or even doubted the description of that existence as defined by the sum total of all the current scientific theories? I'm still very unclear on what such doubt would look like without relying on wholeheartedly believing something else instead, which means we're not talking about doubt in general but doubting some specific thing (generally science or naturalism) and wholeheartedly believing some other thing instead (spiritualism or religion).

I don't know if this is just my personal experience but I rarely get involved in discussions (outside of professional philosophy) advising one believes both in Buddhist reincarnation and Christian heaven because we shouldn't be so certain about reality. It seems remarkably easy to say we shouldn't dismiss the existence of the soul because we can't be sure, but much less popular to suggest we should follow the tenets of several different religions at once for the same reason.

, you disagree with my account of how people come to believe that Realism is true. You say that it just isn't convincing. For my part, I find the idea that a metaphysical interpretation of reality is biologically hardwired into the human race for survival purposes (what other purpose could the hardwiring serve, given natural selection?) incredible.

I do not have much stock in this however. It doesn't really matter to me whether it is hardwired or not. I was only interested in that idea insofar as it concerned the argument that 'because realism is hardwired into us, it is probably true', an argument which I reject entirely. It seems that you agree with me that there is no reason to think that Realism is true. I'm not sure yet what should be done about that fact. Of course, Idealists think we should just drop the assumption. I do think, however, that if we are right about the baselessness of Realism, that realization should instil a kind of modesty when criticizing worldviews different to our own, and I think that's a valuable consequence of this kind of philosophical discussion.

You're using a realist argument to help PossibleAaran defend realism — T Clark

The person you quoted is PossibleAaran, ie, me. Also, the argument I gave in the quotation isn't an argument in defence of Realism. I denied that Realism is 'in built' and suggested that it is taught to us as children. I haven't defended Realism at all in this thread. I have consistently said both that there is no way to prove Realism to those who don't accept it, and that the Realist can't even locate a reliable source for his belief in unperceived existence, even a source which Realists themselves recognize as reliable.

So I can't make much sense of what you said here.

Generalized doubt, Cartesian doubt, or global scepticism, is fundamentally incoherent, especially if it's based on merely imagining that things could be different than they appear to be (imagining alternative "logical possibilities"). To doubt, you need a reason to doubt, not just a contextless wondering whether things might be different than you think they are. — gurugeorge

it can't coherently be elevated to a permanent cognitive stance that doubts everything. — gurugeorge

I have heard this argument several times, usually from Wittgenstien's followers. But why is it incoherent to doubt everything? There is no explicit contradiction, so can you make the contradiction explicit? Its obviously true that ordinarily we don't doubt everything. We hold some things fixed and doubt other things within that context. But I've never seen a reason to think that there is anything incoherent about extending the doubt to everything.

You said that 'you need a reason to doubt'. I don't think so. All you need in order to doubt something is the ability to ask 'why believe that?'. So long as I can ask that question, I can doubt, so why can't I ask that question with respect to everything I believe?

PA

That doesn't make you non-realist. That just means you think reality is different than the naturalistic version. Metaphysical realist means a belief in a mind-independent world. I grew up Christian, and most of those folks believed God created a material world that may or may not be compatible with what scientists say. I don't recall anyone espousing Berkeley's idealism, other than reference to Christian Science or gnosticism, which was considered heretical. — Marchesk

Interesting. I don't think I was making a distinction between realist, materialist, and naturalist. I may not have known there was one. I'll think about it.

So I can't make much sense of what you said here. — PossibleAaran

I seem to be having trouble getting my quotes and references wrong. I guess I need to slow down and pay better attention.

Yeah, exactly. Global scepticism is a dead end in thought. It looks tempting, and it's instructive to poke around, but ultimately it just doesn't make any sense.

Or to put it another way, whatever the hell the global sceptic thinks they're doing, it sure isn't doubting :)

Any "why believe that?" question can be answered normally. Why believe there's a table in front of you? Because you can see it, it's got the functional form of a table, you can rap on it, etc. Those sorts of things are the standard for answering "why believe?" questions.

You can't extend doubt to everything because, as I said, you can only doubt on the basis of some other things held to be true, because that's how doubt works, it's leveraged off of truths. Truth comes first, doubt is secondary. Truth is the usual state, doubt departs from it and returns to it.

For example, you can only say that something is an illusion on the basis of some other corrective perception that tells you it's an illusion. But that means you're accepting the corrective perception as valid. But that means you can't doubt whether all perceptions are illusions, only some.

IOW, if there's such a thing as illusion anywhere, then there logically must also be such a thing as valid perception somewhere, because without valid perceptions no such thing as illusion could possibly be revealed (or: "illusion" would have no meaning). They're inextricably tied together, depend on each other for meaning (or to be more precise, "valid perception" is tied to "illusion" in this way), so the idea of "extending" doubt to all perception is incoherent, it seems like something you might be able to do, but you can't actually do it, except as an imaginary exercise. But no truths hang on the use of the imagination.

Notice that even with something like the Brain in a Vat thought experiment, the hypothetical mad scientists must have been having valid perceptions in order to cobble together the apparatus. On the other hand if you use something like Descartes Demon to get rid of that problem, the problem with him is that he's just an imagined possibility. Whereas the mad scientists have the advantage that we know they're actually possible, at a stretch, there's no reason to believe a deceiving demon could exist; but if the mad scientists are possible then they must be perceiving things correctly, so the hypothesized BiV predicament can't possibly cast doubt on all perception, only one's own. But we already knew that our perception can be mistaken, that's why we sometimes check things by asking other people.

Another way of putting this: you can extend doubt by "but what if?" extensions, but the more "but what if?" extensions you add, the more you're just drifting into speculation without any reason for it, the more your doubt is transforming into idle imagination of alternative possibilities; whereas the simpler, more limited, more specific, particular and occasional the doubt, the more ACTUAL reasons you CAN HAVE for doubting.

, this all seems largely misconceived.

Any "why believe that?" question can be answered normally. Why believe there's a table in front of you? Because you can see it, it's got the functional form of a table, you can rap on it, etc. Those sorts of things are the standard for answering "why believe?" questions. — gurugeorge

I grant that that is how we normally answer 'why?' questions.

You can't extend doubt to everything because, as I said, you can only doubt on the basis of some other things held to be true, because that's how doubt works, it's leveraged off of truths. Truth comes first, doubt is secondary. Truth is the usual state, doubt departs from it and returns to it. — gurugeorge

Why can I only doubt on the basis of some other things held to be true? I am assuming that by 'doubt' here, you mean suspend judgement. I am not sure what else could be meant. But why can't I suspend judgement on everything without believing other things to be true? Its all well and good saying 'that's how doubt works', but that isn't to answer the question I have asked, but just to restate your view with the qualifier 'that's just how it is'. Hardly a satisfying argument.

For example, you can only say that something is an illusion on the basis of some other corrective perception that tells you it's an illusion. But that means you're accepting the corrective perception as valid. But that means you can't doubt whether all perceptions are illusions, only some...

IOW, if there's such a thing as illusion anywhere, then there logically must also be such a thing as valid perception somewhere, because without valid perceptions no such thing as illusion could possibly be revealed (or: "illusion" would have no meaning). They're inextricably tied together, depend on each other for meaning, so the idea of "extending" doubt to all perception is incoherent, it seems like something you might be able to do, but you can't actually do it, except as an imaginary exercise. But no truths hang on the use of the imagination. — gurugeorge

Your example brings out a misunderstanding of the role that sceptical hypotheses play in my OP and subsequent posts. I am not merely saying "oh well all of life might be an illusion. I suspend judgement on whether it is or not." I never made that suggestion. My suggestion was two fold. (1) We cannot prove to someone who doubts it that the objects of sense perception exist unperceived, (2) we cannot even locate a reliable source for that belief to the satisfaction of realists themselves.

But let's think about illusion. What is meant by saying that my current perceptual experience is an illusion? It surely just means that the object of my current perceptual experience is one which doesn't 'really' exist, and what does that mean? It means just that the object of my current perceptual experience doesn't exist when I am not perceiving it. The difference between an illusion and a veridical perception is that the object of the latter, but not the former, is supposed to exist unperceived. If this is the concept of 'illusion' involved, then there is nothing incoherent about supposing all of life to be an illusion at all. To suppose that would be to suppose that every object of every perceptual experience one has is one which does not exist unperceived. And to think that the evil demon hypothesis is true is to think that every object of every perceptual experience one has is one which does not exist unperceived and that an unperceived evil demon exists which is the cause of perceptual experience. What's incoherent about that? It sounds like a perfectly coherent story of how things might be. I have given a perfectly clear meaning of 'illusion' which doesn't at all depend on any of our perceptions being veridical.

so the hypothesized BiV predicament can't possibly cast doubt on all perception, only one's own. But we already knew that our perception can be mistaken, that's why we sometimes check things by asking other people. — gurugeorge

Of course, if I am doubting whether any of the objects of sense perception exist unperceived, it is the objects of my sense perception about which I am doubting. It is true that perception can be mistaken and that we 'already knew that', but this is irrelevant to either (1) or (2) or my ability to entertain the evil demon hypothesis.

PA

For example, you can only say that something is an illusion on the basis of some other corrective perception that tells you it's an illusion. — gurugeorge

What you saying is, an illusion, compared to what? Which I think is a fair question.

It’s telling that in a culture which generally values scientific realism, that the possibility of life itself being a grand illusion is imagined in terms of what ought to be considered ‘veridical perception’ and the sense in which it might turn out not to be veridical. It’s as if we’re considering ‘illusion’ as a kind of optical illusion or mirage.

I think, by contrast, the original intent of scepticism was much more concerned with the possibility of the illusory valuation of what we (the hoi polloi!) all take for granted. I think the early sceptics doubted convention and conventional ways of understanding, and cast doubt on the values imputed by those around them on such things as wealth, possessions, social status, respectability, the social contract, and the kinds of things that ‘everyone knows’ to be true.

It was in that sense a renunciate phiosophy, which calls ‘the world’ into question, not in the sense of asserting that raw sensory experience is illusory, but in the sense that ‘the world’ is a world of imputed and agreed meanings, values, and attributions. SO I think the original intent of scepticism was to disentangle oneself from the illusions of conventional mores rather to cast doubt on whether ‘the table really is a table’ (which is the object of the rather ridiculous ‘objection to idealism’ ‘here is my hand’ by Moore.)

I am assuming that by 'doubt' here, you mean suspend judgement. — PossibleAaran

Doubt is not suspension of judgement, it's the questioning of the truth or validity of something based on reasons (e.g. some anomaly). Suspension of judgement would be something like agnosticism or indecision.

We cannot prove to someone who doubts it that the objects of sense perception exist unperceived, — PossibleAaran

If they are truly objects of perception, then necessarily they exist unperceived, so doubting that objects of perception exist unperceived doesn't make any sense. Generally, with odd exceptions like rainbows, objects of perception just are the kinds of things that exist unperceived (or: if it doesn't exist unperceived, then it wasn't an object of perception after all). You can easily verify the existence of unperceived objects by means of instruments (e.g. using a watch, shut your eyes and simultaneously take a picture with a camera with a timestamp).

I have given a perfectly clear meaning of 'illusion' which doesn't at all depend on any of our perceptions being veridical. — PossibleAaran

Yes, but you've given us no reason to take it seriously and to replace our ordinary use of "illusion" with it. It's just an imaginary usage, a flight of fancy that bears little relation to the ordinary, everyday concept of illusion. The ordinary use of "illusion" is contextual - illusion in relation to veridical perception, and one doubts perception based on reasons. Imagining a deceiving demon isn't a reason to doubt perception.

I think the early sceptics doubted convention and conventional ways of understanding, and cast doubt on the values imputed by those around them on such things as wealth, possessions, social status, respectability, the social contract, and the kinds of things that ‘everyone knows’ to be true. — Wayfarer

Yes, I think that's right. Early philosophers would have been (rightly) baffled by Cartesian scepticism.

Who says being in the world is primary (other than Heidegger)? — T Clark

What's fascinating is that even an attempt like Heidegger's to get under the usual metaphysical fumes can begin to smell like one more fume.This is perhaps because a proper and moreover famous name is tied to 'being-in-the-world' and so on. This over-determines the concept and threatens to drain the words of their original power. If we really are being in the world, then it's away from the book we must look. But books that point away from books are fascinating. It's hard not to write a book about such a book. And now that's one more book we need to read to justify looking away from the cooked books.

In short, I relate to your 'who says?" reaction and at the same time defend the primality of being in the world. My defense fits with your critique elsewhere in the thread of exaggerated skepticism. We aren't bodiless computers in an air-conditioned room searching for perfect string of symbols. We have to eat and breath and excrete just to survive as bodies. We have to interact as babies and children to learn language and become more or less fully human in an emotional sense long before we can indulge in epistemological niceties and pretend to pretend that the world isn't really there. Our world, the world our bodies and hearts live in, has to be in pretty good shape already (as the result of work and suffering) for us to soar with the strange and long words of the metaphysicians. Is this something I need to prove? Ah, but if this isn't 'obvious' to my conversational partners, how I can hope to relate to those who know neither work nor suffering? Those do can doubt the existence of the hammer as it smashes their thumb? Those for whom the eyes of the beloved are an illusion?