In order to doubt that Canberra — Banno

I think it depends on how you define "doubt". If by doubt you mean "it is ◇¬P", yes you need a foundation to doubt it; but if by doubt you mean "I don't know if", you would not need a foundation for doubting, in fact the very lack of foundation would justify your doubt.
I don't know if Canberra is the capital of Australia (P) because none of these terms are known to me, I don't know if P, but I can't say that ◇¬P because perhaps it is □P.
The way Descartes uses 'doubt' is more akin to the weaker statement.

But this is not the argument in this thread. That is specifically about not believing that something continues to exist, unperceived. — Banno

The OP does look different from what I remember, perhaps it has been edited since my first reply.

...but if by doubt you mean "I don't know if", you would not need a foundation for doubting... — Lionino

Wouldn't that you don't know the meaning of "Australia" be the background for your doubt?

Wouldn't that you don't know the meaning of "Australia" be the background for your doubt? — Banno

In that sense, yes. Then your original argument would have to go into more detail regarding what "foundation" exactly means. We can concede that every belief or every though requires a reason or justification, but then we either go into infinite regression or hit some groundrock, typically the law of identity — and if we don't concede it, perhaps that belief/thought is the groundrock.

Word salad aside, if it is the case that "I don't know what Canberra is" is my foundation for doubt, do I need a foundation to state that? Isn't it an immediate assesment of my mental contents (aka knowledge)?

..do I need a foundation to state that? — Lionino

What do you think? Or is "I don't know what Canberra is" foundational?

What justifies believing "I don't know what Canberra is"? Isn't that question somehow inept?

So you have no reason to believe in the existence of the things behind you? When you put the cup in the cupboard, you cease to have any reason to believe that the cup is in the cupboard?

That's not right. — Banno

There are many other things that can be discussed in the thread such as the world itself, God, Souls, places one never has been, people one never met ... etc. The building which stood across the road, but demolished for the new development, hence no longer existing etc.

There are lots of meat in the tittle of the thread for good classic and traditional philosophising too such as reasons (logical grounds), beliefs (grounded or groundless beliefs) and the existence of the world ... etc.

But you keep pointing out the cup and ask if there is point in the thread sounds some sort of obsession with the cup. That comment sounds very silly. I know the cup exists, but I can start doubting if there is a reason to doubt it does. Why is it silly to doubt whatever it might be, if one has a reason to doubt?

For the same logic, Why is it silly to believe in whatever it might be, if one has a reason to believe? Discussing on the nature of the beliefs and doubts and logical grounds for them is an interesting philosophical topic anyone would say, apart from you.

There are many other things that can be discussed in the thread — Corvus

The cups are simple, clear and shows up the issues in a way that other examples tend to obfuscate.

The claim from the OP is that when one is not perceiving the world, there is no reason to believe in the existence of the world. You put the cup in the cupboard. You are no longer perceiving the cup. Therefore, the argument goes, you have no reason to believe that the cup exists.

You put the cup in the cupboard. I ask you to hand me the cup. Do you get it out of the cupboard or do you say "I don't know where the cup is"?

It's a pretty simple example that shows the absurdity of ill-placed doubt.

Of course it's an interesting topic. These considerations deserve attention, as part of "Discussing the nature of the beliefs and doubts and logical grounds for them". This argument is central to this topic. Doubt should not go unquestioned.

What do you think? Or is "I don't know what Canberra is" foundational? — Banno

You can justify that by saying that the symbol Canberra does not elicit any thought in your mind, but that is just equivalent to saying you don't know what Canberra is.

What justifies believing "I don't know what Canberra is"? Isn't that question somehow inept? — Banno

Beyond the circular justification above, it is close to a brute fact, somewhat similar to the cogito.

You can justify that by saying that the symbol Canberra does not elicit any thought in your mind, but that is just equivalent to saying you don't know what Canberra is. — Lionino

yep.

Beyond the circular justification above, it is close to a brute fact, somewhat similar to the cogito. — Lionino

Yep.

Comes in the main from Wittgenstein. See On Certainty.

The discussion in this thread, like all discussions, presupposes the existence of an "external" world in which the discussion is taking place...

Odd, don't you think?

The discussion in this thread, like all discussions, presupposes the existence of an "external" world in which the discussion is taking place... — Banno

You can argue the same thing about many philosophical beliefs. Every determinist acts as if there is free will, or rather, it does not matter to him, because if there is free will he is choosing to act as such, but if there is not, he is not concerned, as he is predetermined to follow this course of action.

This presupposition of the existence of the outside world is not needed for the discussion to happen, as the discussion could be a projection of the mind; but it is needed to believe that there is any point to having the discussion, which most of us certainly believe¹. If we don't believe that there is an outter world but yet are here talking, that would be a case of contradictory beliefs or cognitive dissonance.

I think the subject-matter is the same as the (mostly pointless) 11 pages of this thread, where the definition of 'atheism' is fought over.

It is not that the topic here states that there is no outside world, but brings to question whether there are any strong argument for the belief of the outside world. By that metric, we can still call into question the existence of the outside world while holding a weak belief that it exists which justifies our discussion here.

I am an atheist because I don't think there any convincing arguments for the existence of God, not that I don't think God exists (even if these two might collapse under some epistemologies).

1 – Or is it? After all, what is wrong with interacting with the projections of our own mind?

The discussion in this thread, like all discussions, presupposes the existence of an "external" world in which the discussion is taking place... — Banno

Perhaps at the very least it presupposes that solipsism is false. It need not presuppose the existence of a material world (e.g. it allows for idealism), or that the world we experience is that material world (e.g. it allows for us being brains-in-a-vat).

But as philosophers we tend to want for something stronger than presuppositions, and so even solipsism is an open question.

This presupposition of the existence of the outside world is not needed for the discussion to happen, as the discussion could be a projection of the mind; — Lionino

Perhaps at the very least it presupposes that solipsism is false. It need not presuppose the existence of a material world (e.g. it allows for idealism), or that the world we experience is that material world (e.g. it allows for us being brains-in-a-vat). — Michael

I dunno. It seems to me that you should have difficulty in denying the existence of these words, even as you are reading them.

How can that be?

It seems to me that you must conclude that there is something more than just your thoughts.

But having established that there is something more than just your thoughts, we might press the argument further.

Novelty. We are sometimes surprised by things that are unexpected. How is this possible if all that there is, is already in one’s mind?

Agreement . You and I sometimes agree as to what is the case. How is that possible unless there is something "external" to us both on which to agree?

Error. We sometimes are wrong about how things are. How can this be possible if there is not a way that things are, independent of what we believe?

Again it might be worth pointing out that philosophy is hard. Each of these points needs a PhD, if not a career, to be treated adequately.


I guess the upshot is that it is somehow quite implausible to question the existence of a world around you, whilst all the while participating in it.

It seems to me that you must conclude that there is something more than just your thoughts. — Banno

Certainly more than my thoughts but possibly not more than my thoughts and experiences.

Novelty. We are sometimes surprised by things that are unexpected. How is this possible if all that there is, is already in one’s mind? — Banno

I can be surprised when I dream but it doesn’t follow that the things I dream about are “external” to my experience of them. So it’s not prima facie necessary that the same isn’t true of waking experience. It could be that dreams and waking experiences are two different modes of solipsistic existence.

Agreement . You and I sometimes agree as to what is the case. How is that possible unless there is something "external" to us both on which to agree? — Banno

It could be a shared hallucination. We’re both brains in a vat being fed the same misleading sensory inputs. Or it could be that you’re a figment of my imagination.

Error. We sometimes are wrong about how things are. How can this be possible if there is not a way that things are, independent of what we believe? — Banno

If solipsism is true but I believe that solipsism is false then my belief is in error. If solipsism and so mathematical antirealism are true then I still don’t know the square root of pi. Other minds and an external material world are not necessary to be wrong or ignorant.

And how would you reply to each of these counterpoints, were you arguing my view?

Your responding to me is not an argument for the world. It cuts all that rationalisation out, instead showing your participation in the world. PI §201, again.

Hence any doubt is infelicitous. We should then ask 's question.

And how would you reply to each of these counterpoints, were you arguing my view? — Banno

I’m not sure if I would. I just accept the existence of a material world and that my everyday experiences are of that material world as a matter of faith, even though there might be good reasons to believe otherwise, such as Bostrom’s simulation argument or the implications of Boltzmann brains being physically possible (and even likely).

But I won’t pretend that this faith is more reasonable than the alternative view.

...good reasons... — Michael

Then perhaps our only point of difference is, what reasons are to count as "good"...

:wink:

But there's a further issue we might consider, in that so many of the posts in this thread attempt to argue for the existence of the world from physics (without the maths).

That has to strike you as circular, doesn't it? Arguing from a description of the world to the existence of the world?

If you are convinced by Boltzmann to believe you are a Boltzmann brain, then the universe is pretty much as physics describes it, since that description - physics - is what Boltzmann uses to reach the conclusion that you are a Boltzmann brain...

And yet somehow the argument is seen as reaching the conclusion that the world is not as it appears...

If you are convinced by Boltzmann to believe you are a Boltzmann brain, then the universe is pretty much as physics describes it, since that description - physics - is what Boltzmann uses to reach the conclusion that you are a Boltzmann brain...

And yet somehow the argument is seen as reaching the conclusion that the world is not as it appears... — Banno

The conclusion is that there is an external world that behaves according to the laws of physics but that we are most likely brains floating in a vacuum rather than embodied humans living on Earth. Part skepticism, part external world realism.

Of course, the problem is when you want to accept the veracity of physics but reject the implication that we are most likely Boltzmann brains. How would you resolve that apparent contradiction without resorting to special pleading?

How would you resolve that apparent contradiction without resorting to special pleading? — Michael

I don't see a need to "resolve" the issue.

But if pushed I'd use much the same sort of argument I used against reincarnation - what is the "I" in "I have been reincarnated"... and what is the "I" in "I am a Boltzmann brain"? I am not a Boltzman Brain, nor am I the reincarnation of Cleopatra. I am Banno.

I am not a Boltzman Brain, nor am I the reincarnation of Cleopatra. I am Banno. — Banno

“I am Banno” and “I am a Boltzmann brain” are not in conflict.

You are Banno, and if our physics is correct then you are also most likely a Boltzmann brain.

“I am Banno” and “I am a Boltzmann brain” are not in conflict. — Michael

Sure. That does not render Boltzmann brains true. Again, I don't see a need to "resolve" the issue; indeed, I don't see that it could be resolved.

There's plenty of insuperable philosophical issues, and it's easy to make up even more.

But, so far as this thread goes, if Boltzmann brains exist, that shows that there is a world.


(Edit: just to be sure, I'll maintain that the person to whom you are talking is not a Boltzmann brain, even if a Boltzmann brain is somehow imagining him...)

But, so far as this thread goes, if Boltzmann brains exist, that shows that there is a world. — Banno

Sure. Same with brains in a vat.

That does not render Boltzmann brains true. — Banno

I’m not saying they’re true, only that if our understanding of physics is correct then it’s most likely.

Ok.

If you want me to pick at this some more, I'd say that the conclusions reached by such arguments, especially in pop literature and in these fora, are overblown.

But yeah, sure. Cheers.

A bit more - again, the showing is what counts here - all this might well be the construct of a random quantum fluctuation... but if I don't go water the plants, they will die. It's what we do that counts, action over theory, meaning as use.

Here's perhaps the original paper in which the mad brain response is worked out: You are not a Boltzmann Brain

So you have no reason to believe in the existence of the things behind you? When you put the cup in the cupboard, you cease to have any reason to believe that the cup is in the cupboard?

That's not right. — Banno

There might had been a situation where you put the cup in the cupboard of the shared kitchen dormitory in your university time. I wonder if you had ever lived in a dormitory of a university with the other folks sharing a kitchen. I had long time ago.

A cup can go missing in shared kitchen cupboard like that with other folks coming into the kitchen and grabbing whatever cup they see when they open the cupboard, make coffee and take it to their room. This used to happen often, and I had to look for an any free cup for making coffee for me.

If you were buying some coffee for yourself in a spar, and see new cups for a dollar or two beside the coffee jars in the shelf, then you might decide to buy them because you doubt if your own cup in the cupboard has been taken away by some other folks in the corridor, and you will never see it again. Yes, you might doubt if your cup exists or not. Why not?

In real life, people move things around, buildings and houses get demolished for new development, roads and grounds get eroded by heavy rains, trees get chopped off, people born, people die, people leave, the sun keeps rising and setting, and time passes non-stop. Nothing remains the same. Why should you stop doubting? If you don't doubt, that's not right.

I do believe in the existence of the cup when I am perceiving it, but when I am not perceiving it, I no longer have a ground, warrant or reason to believe in the existence of it.

Indeed, and this is what Berkeley said. Something that would exist independently of a perceiving mind is unverifiable. Because, if you check that such a thing exists, well, too late, you're using thought again. That is the powerful argument by Berkeley.
BUT it doesn't lead to a pure and insane subjectivism, as Berkeley himself noted (although Hegel showed it way better, according to me). Here is the condensed proof. If we can not have any knowledge about the external world, then we can't even say that this "external world" exists. So there would only be an "internal" world. But how could there be an "internal world" without an external one? So it means that our so-called "internal world" is not "just internal", "sadly internal"... It is the world itself.
(source: Brief Solutions to Philosophical Problems Using a Hegelian Method, Solution 2)

I can’t speak on the more scientific aspects of that paper, but on that final section, although it’s the case that any randomly selected brain is most likely a batty brain, it’s also the case that any randomly selected non-batty brain is most likely a Boltzmann brain.

↪Corvus
I do believe in the existence of the cup when I am perceiving it, but when I am not perceiving it, I no longer have a ground, warrant or reason to believe in the existence of it.
Indeed, and this is what Berkeley said. Something that would exist independently of a perceiving mind is unverifiable. Because, if you check that such a thing exists, well, too late, you're using thought again. That is the powerful argument by Berkeley. — LFranc

The point at the time of writing the post was logical ground rather than physical, ontological or epistemic ground for the doubt. If your ground for believing in the world is your perception (P), then
what is the ground for the belief when not perceiving the world? (¬P).

It wasn't about the existence of a cup, or any particular physical objects as such. It was rather about the the nature of our belief in the existence of the unperceived objects or world.

I guess the upshot is that it is somehow quite implausible to question the existence of a world around you, whilst all the while participating in it. — Banno

I would go as far as to say that, even if we outright deny the existence of the outside world, it is not a performative contradiction. You do not need to be agnostic about it to have consistent beliefs.

In the case that I think there is no world, it follows that I believe that everything around me is merely a projection of my mind (or simply is my mind). If I also believe that I am here discussing for a purpose, it could very well be that I believe that I am interacting with the very contents of my mind and, upon investigating them, I might arrive at a conclusion regarding the topic. Upon talking with you lot (aka investigating the contents of my mind), it could be that I change my mind and now believe that there is indeed an outside world, or it could be that I strenghten my previously belief that there is no world.

You can say it is an unhinged perspective, but so is solipsism, albeit there not being a logical contradiction in the view, remaining within the realm of possibility.

As to your points regardings agreement, novelty, and others, it might be that Michael has satisfactorily addressed them (not for me to decide, since the doubt (:razz:) is yours).
As as far agreement and disagreement goes, it can simply be that I hold two pieces of information in mind and I come to the conclusion that they contradict each other, and, since the mind is not perfect, it is fine to have two beliefs that seem to contradict each other as result of a lack of some information or some other imperfection.

If a mind progresses through time, it may use the information it holds as premises to reach new conclusions, hence novelty. From this explanation of agreement and novelty, we may realise our errors.

You may say "A floating mind that changes through time? This is fantasy.". And it is fantasy, because I just made it up, but I am just defending that solipsism does not entail contradiction. "But then time is the outside world!" Well, that is a question that I don't wanna tackle, but it could be.

It is not that denial of an external world, or solipsism, is logically contradictory, or else those views would long since have been put paid to. The question, as @Banno has indicated, concerns plausibility.

So, when everything we ordinarily think, do and say flies in the face of those views, then holding to them by mere lip would be a performative contradiction, not a logical contradiction.

That much is fine, as our actions often reflect our common sense rather than our rationally held (so to speak) beliefs, but let me explain myself. When I said "contradiction" or "logically contradict" in the post above, I am alluding to this exchange we had:

That the discussion in this thread pressuposes a belief in a real world outside our minds, my comment is a rebuttal exactly to that claim.

That the discussion in this thread pressuposes a belief in a real world outside our minds, my comment is a rebuttal exactly to that claim. — Lionino

I would say that it might not logically presuppose the existence of a world, but that it does pragmatically presuppose it. No one really believes they are the only person or that there is no external (to the body) world; and anyone who consistently behaved as though they believed those things would likely be scheduled and put on medication for the protection of themselves and others..