But it's a faith, not something supported by empirical evidence. — Michael

As if basing one's beliefs on empirical evidence were not an act of faith... If you are a Boltzmann brain, what are the chances of your having just happened to have imagined into being a world that exactly corresponds to the actual world? You happened to drop into existence in a way that allows you to realise you are a Boltzmann brain...

Pretty suspicious. Perhaps a good argument for solipsism...

Are you still there?

Yes, I would say that discussion performatively, if not logically, presupposes the existence of a mutually experienced world external to the body. We all believe in such a world, so why give any air to faux-doubt about it?

IF you are a Boltzmann brain, all bets are off. The coffee container might contain a lion. The cup will have fallen down a black hole inside the cupboard.

But this is not the world we experience.

I'm happy to treat this as a reductio; the persistence and predictability of the world shows that the Boltzmann brain argument is in error, even if it is not clear exactly what that error is.

And that is not a disproof of Boltzmann brain theory, so much as a rejection of mere quibbling.

Something like that.

As if basing one's beliefs on empirical evidence were not an act of faith... If you are a Boltzmann brain, what are the chances of your having just happened to have imagined into being a world that exactly corresponds to the actual world? You happened to drop into existence in a way that allows you to realise you are a Boltzmann brain... — Banno

There are, broadly speaking, four possibilities:

1. We are Boltzmann brains and our scientific theories are mostly correct
2. We are Boltzmann brains and our scientific theories are mostly incorrect
3. We are not Boltzmann brains and our scientific theories are mostly correct
4. We are not Boltzmann brains and our scientific theories are mostly incorrect

If our scientific theories are mostly correct then either (1) or (3) is the case, with (1) being most likely (as per those very scientific theories).

So one of these is true:

a. We are most likely Boltzmann brains (1 or 3)
b. Our scientific theories are mostly incorrect (2 or 4)

The argument is valid:

1. There are far more long-lived Boltzmann brains than long-lived humans
2. I am long-lived
3. Therefore, I am more likely to be a Boltzmann brain than a human — Michael

It is impossible for a human to not be a human.

It is impossible for a human to not be a human. — creativesoul

And it's impossible for a Boltzmann brain to not be a Boltzmann brain, or for a horse to not be a horse.

What of it?

What of it? — Michael

It's odd to me when one exclaims that they are more likely to be a philosophical tool for thinking than a human whose thinking and/or using the tool.

That's what.

It's odd to me when one exclaims that they are more likely to be a philosophical tool of thinking than a human. — creativesoul

It is a fact that our current scientific theories entail that we are more likely to be Boltzmann brains than ordinary humans.

It's certainly counter-intuitive, but then so is much of science. I won't claim that my intuitions ought take precedence over scientific evidence.

:smile:

:insert shaka:

that discussion performatively, if not logically, presupposes the existence of a mutually experienced world external to the body — Janus

Where there has never been language use, there could have never been any discussion such as this one. It does not matter if one believes that or not. — creativesoul

That still does not defeat solipsism, what I said before to Banno applies to language too:

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 — Lionino

That still does not defeat solipsism, what I said before to Banno applies to language too:
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 — Lionino

Solipsism cannot be defeated with certainty, but it is defeated by plausibility. You say, "in the case that I think there is no world", but no one or almost no one thinks that due to its implausibility. The issue of solipsism only gets raised because we cannot be, as with many other things, absolutely certain it is not the case.

Yep.

And given that there is a brain, the longer it persists the less likely it is to be merely a quantum fluctuation.

You are nothing if not persistent.

(See what I did there? )

That still does not defeat solipsism — Lionino

No, it doesn't, but it might reduce the solipsist to the status of a mere object of ridicule.

That is, in both these cases, as in the case of the existence of the world, there may be a point at which one's credulity is strained a bit too far. That point will be different for different folk, some of whom never participate in philosophy fora, some who treat it as an amusement and a very few who take it seriously enough to find themselves in an asylum.

So perhaps all up it is not unreasonable to take things at face value?

At the least, it makes it easier to buy coffee.

It is a fact that our current scientific theories entail that we are more likely to be Boltzmann brains than ordinary humans. — Michael

No, it is a fact that some interpretations of our current scientific theories entail that we are more likely to be Boltzmann brains than ordinary humans. It pays to remember that scientific theories, and science generally, only tell us how to make sense of how things appear to be to ordinary humans.

that discussion performatively, if not logically, presupposes the existence of a mutually experienced world external to the body
— Janus

Where there has never been language use, there could have never been any discussion such as this one. It does not matter if one believes that or not.
— creativesoul

That still does not defeat solipsism... — Lionino

Solipsism is a philosophical idea. It is a language construct. Language constructs are existentially dependent upon shared meaning; shared meaning... more than one mind. It is impossible for solipsism to be true.

...what I said before to Banno applies to language too:
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
— Lionino — Lionino

Solipsism is a philosophical idea. All philosophical ideas are existentially dependent upon language use. Language use... shared meaning; shared meaning... more than one mind... solipsism... more than one mind.

And given that there is a brain, the longer it persists the less likely it is to be merely a quantum fluctuation. — Banno

But still more likely than not being a Boltzmann brain.

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 — Lionino

That whole thing radically changes what is usually meant by "mind' and "my".

I understand what it is to dream - the world around me is no dream. I understand what it is to imagine or fantasise - the world around me is no such phantasm. So if the world around me is somehow a construct of my mind, it is very different to other mental constructs.

So different that one might be tempted to call it "real"?

But still more likely than not being a Boltzmann brain. — Michael

Are you still here?

Good.

The issue of solipsism only gets raised because we cannot be, as with many other things, absolutely certain it is not the case. — Janus

I am.

It pays to remember that scientific theories, and science generally, only tell us how to make sense of how things appear to be to ordinary humans. — Janus

They tell us how to make sense of how things appear to us. Whether or not we are ordinary humans or Boltzmann brains is the very question being considered.

it is a fact that some interpretations of our current scientific theories entail that we are more likely to be Boltzmann brains than ordinary humans. — Janus

Not just some, but the leading theories.

It pays to remember that scientific theories, and science generally, only tell us how to make sense of how things appear to be to ordinary humans. — Janus

I wonder what more Janus wants? What more could he want?

I am. — creativesoul

I also feel absolutely certain that solipsism is not the case, but since it cannot be proven to not be the case, I cannot be absolutely certain.

↪Michael I wonder what more Janus wants? What more could he want? — Banno

That's all I want, and since it seems incoherent to want something unimaginable, you might also say it's all I could want.

They tell us how to make sense of how things appear to us. Whether or not we are ordinary humans or Boltzmann brains is the very question being considered. — Michael

If Boltzmann brains are random fluctuations, it begs the question as to how anything like that could make sense of anything, and thus how they could (in concert?) construct the whole edifice we know as science.

Also, if, as Boltzmann brains our remembered past histories are illusions, whence the shared memories that humans routinely experience? Can you make sense of that? How far back into the memories of the past before we, as Boltzmann brains, encounter illusion? Years, months, day, hours, a few seconds. The whole idea seems, however it might be supported by (the mathematics of?) some theories, absurd. Are not all theories interpretations? Are our memories of what we have learned of science and mathematics also illusions? If so, then how can we justifiably use them to support any conclusions at all?

...since it cannot be proven to not be the case, I cannot be absolutely certain. — Janus

Drop the requirement of proof and take it as a "hinge" proposition, not to be subject to doubt.

That's all I want, and since it seems incoherent to want something unimaginable, you might also say it's all I could want. — Janus

Yep. It's not as if, that the description is only as it appears to ordinary humans implies that the description is wrong... But that seems to be what some folk think.

@Michael?

You still there?

Damn.

:yikes:

Drop the requirement of proof and take it as a "hinge" proposition, not to be subject to doubt. — Banno

:up: Yes, I think I do, but some are not satisfied with being unable to attain the unattainable.

Are not all theories interpretations? Are our memories of what we have learned of science and mathematics also illusions? If so, then how can we justifiably use them to support any conclusions at all? — Janus

See here.

There are, broadly speaking, four possibilities:

1. We are Boltzmann brains and our scientific theories are mostly correct
2. We are Boltzmann brains and our scientific theories are mostly incorrect
3. We are not Boltzmann brains and our scientific theories are mostly correct
4. We are not Boltzmann brains and our scientific theories are mostly incorrect

If our scientific theories are mostly correct then either (1) or (3) is the case, with (1) being most likely (as per those very scientific theories).

So one of these is true:

a. We are most likely Boltzmann brains (1 or 3)
b. Our scientific theories are mostly incorrect (2 or 4) — Michael

This ignores the fact that some aspects of science are far more speculative than others, and that a binary distinction between mostly correct and mostly incorrect doesn't address the fact that Boltzmann brains are a matter of speculation and not observation.

Well yes, there are good reasons to doubt that the cup will remain in the cupboard. The point here is simply that your "when I am not perceiving the world, there is no reason that I can believe in the existence of the world" is not a good reason to think that the cup has disappeared from the cupboard. — Banno

When you are not perceiving the world, you wouldn't be asking the question where is my cup, would you? The question sounds absurd.

This had me puzzling. How do you go about buying coffee? There's the package on the shelf at the store, brightly labeled "Dark Roast". But when one is not perceiving the coffee, — Banno

Again when you are not perceiving the world, you wouldn't be going out buying coffee either. Isn't it an absurd puzzling? The puzzle must be an illusion when you are not perceiving the world. Where does your puzzle come from?

But it's not a belief. The world really exists. And it really exists precisely because there is nothing outside of ideas or perceptions. Since there is nothing outside those, there is no "outside" at all, and since there is no outside, the so-called "inside" is actually the world itself. So the world does exist. It lies within the idea itself. Idealism leads to realism and realism leads to idealism. It's a "loop". — LFranc

When one is a hard idealist, and the world is just a representation in his mind, it would be hard to refute him. Indeed if what you see is a representation of the world, how do you know the real world?
If you are a part of the world, do you even exist yourself?

Boltzmann brains are a matter of speculation and not observation. — wonderer1

You're right that it's not a matter of observation (and perhaps that my binary distinction is imprecise), but it's wrong to suggest that it's as simple as speculation. Rather it's a consequence of our best understandings of quantum mechanics and thermodynamics.

So either we are most likely Boltzmann brains or our best understandings of quantum mechanics and thermodynamics is mistaken.

Given that the scientific evidence supports our best understandings of quantum mechanics and thermodynamics, the scientific evidence doesn't support the claim that we are not likely to be Boltzmann brains.

So what justifies your claim that we are not likely to be Boltzmann brains? Is it just "common sense" or "intuition"? Are "common sense" and "intuition" more reasonable than scientific evidence?

You're right that it's not a matter of observation (and perhaps that my binary distinction is unfair), but it's wrong to suggest that it's as simple as speculation. Rather it's a consequence of our best understandings of quantum mechanics and thermodynamics. — Michael

I'm not suggesting it is simple speculation, but it does depend on assumptions such as that the universe is eternal. Furthermore, science is hardly exhaustively covered by quantum mechanics and thermodynamics, and the best scientific case is for us being the result of biological evolution.