Is there a good counterargument to the Boltzmann brain or simulation hypothesis

This is the argument as I understand it.

On universal time scales, there will probably be a near infinite number of Boltzmann brains that are identical to your own brain. Plus assuming intelligence continues to evolve, there are probably a large number of simulations of life before a singularity.

But there is only one version of you that actually occurred in the here and now.

So statistically, if ‘you’ are experiencing your life, that life may have happened endless times over the course of the universe before heat death, but all but 1 are either simulations or a Boltzmann brain. The odds that you are the 1 experience that actually happened is low, and by all probability it is a simulation of one kind or another.

What is a counterargument to this argument?

Well I am aware of at least two counter-arguments, hopefully these IIRCs are accurate enough:

  1. You shouldn’t make empirical claims based on statistics in this way.
    So, e.g. a stone age man concludes that humans are unlikely to ever live in vast cities because, if that were to happen, the chance of being born in the stone age would be that much lower. But of course some people need to be born in the stone age, and it’s debateable whether it makes sense to think of your “chance” of being born in a particular place. The same applies to thinking about your “chance” of being born in a simulation.

  2. The number of Boltzmann brains that think they have understanding would outnumber the number of brains that actually have understanding. Therefore it’s a thread of reasoning that leads us into discounting our own ability to reason.
    (Which technically isn’t quite a counter-argument, but apparently many philosophers find it convincing)

Counterargument - the Universe is neither infinite in extent nor duration, hence Boltzmann nucleation won’t happen.

The Boltzmann brain concept comes from the idea that the only thing that could cause the low-entropy state at the beginning of the universe is random perturbation. But a single brain is hugely more probable than a whole universe, so we’d expect to find ourselves in one of those, not a situation with a bunch of brains and other stuff.

One answer is that there must have been some other mechanism for creating the low-entropy state. One that isn’t quite so based on pure probability. Intuitively, it seems to me that even though the Big Bang singularity had low entropy, it was “boring” in a way that a brain is not. It was just a bunch of matter in a tiny space. As it blew up and evolved, it traded a kind of generic boring low entropy for more interesting structures.

My own view is that there is some kind of scaling event that went on. Imagine a bunch of particles in empty space interacting by some force; say, gravity. They’re spread out over some area. Entropic principles suggest that it’s unlikely that all these particles will suddenly all be at a particular location all at once; picking out some volume 1/10 the linear dimension would make the probability of all the particles being in that location 1/1000[sup]N[/sup]; very unlikely for large N.

Now imagine that the laws of physics “glitch” and the force constant goes up by a factor of 100. Our particles now behave as if they had suddenly been compressed into a volume 1/10 the size. Sure, this universe is scaled compared to one where we really did shrink everything, but there would be no way to tell the difference–every measuring stick would read the same between the two, because the sticks themselves have changed size.

Our universe has more complicated laws and such a scaling event would require changing more than one thing at a time in order to behave the same way–but who’s to say that the predecessor to our universe followed the same laws? Maybe only a few laws/constants had to change.

Of course, it’s weird to speculate that the laws of physics could change like this. It seems unlikely. But then, the odds of getting to the early universe state randomly is exceptionally unlikely. One can try to represent it with numbers (it is something like 10[sup]10[sup]-120[/sup][/sup]), but numbers this small defy human intuition.

The counterargument would seemingly be, AIUI - “Well, there’s no evidence for it.” It would be like arguing that “Somewhere, in the universe, is a planet made entirely of pink polka-dot marble.” Sure, the universe is incredibly vast, and there are an incredible number of planets out there, but there is zero evidence for it. It can’t be proven or disproven, but there is zero evidence for it.

This might be similar to Penrose’s “Conformal cyclic cosmology” model, though instead of a ten-fold shrinkage, his is a googol-fold or such, as one entropy death becomes the big bang of the next cycle.


Am I correct that, if I were a "Boltzmann brain," instead of "I think therefore I am", I should be writing "I think you guys think you think, therefore I think you think you're real .... but you're not!" ?

I think I didn’t explain this one very well, so I’ll take another run at it:

There’s a long history in philosophy of reasoning things into existence – of course the many “proofs” of God but many other concepts besides. Also “proving” that some things cannot exist.
But delivering such a conclusion almost always requires a liberal dose of wishful thinking and assumptions, whether those assumptions are obvious or not.

So let’s screw all that and do science instead.

And to be clear, the simulation hypothesis is absolutely reasoning something into existence: a world outside the Matrix. We only have empirical data of the matrix.

Exactly. OK, suppose you’re really a brain in a jar. The only problem is that requires there to be a higher-order universe for your brain to exist in, that runs the simulation that your brain is experiencing.

Occam’s Razor, dude. You’re multiplying entities without necessity.

And besides, if our so-called senses are so fallible that we can’t trust anything we sense, and our so-called brains are so fallible that we can’t trust anything we think, then there’s no point to anything. And if there’s no point to anything, then what’s the point of postulating that there’s no point to anything?

Thing is, we do know our brains and our senses are fallible. I forgot my phone the other day. Stupid brain, it made a mistake. So I guess I should just curl up in a ball and sob and give up on life because nothing matters? Dude, if nothing matters then it doesn’t matter that nothing matters, so why bother curling up in a ball and sobbing about it?

Yeah, my idea looks something like that (and I am imagining a rescaling on the order of 10[sup]60[/sup] or more; the 10x was just an example), except that I propose a change to universal constants. Maybe even that is not necessary.

We don’t have a lot of strong evidence that the constants can’t change, even on the timeframe of our own universe. Extend things out a bit longer–10[sup]20[/sup] years, say–and who knows what can change. That’s still a much shorter time than it would take to assemble a singularity through sheer randomness.

Contrary to the OP’s suggestion, Boltzmann brains are not related to solipsism or brain-in-a-jar scenarios. The question is just why isn’t our brain the only thing in the universe? “I think, therefore I am” dictates at least one brain. But statistically, there shouldn’t be more than that. That contradicts observation–we see a whole universe. It’s not as parsimonious as we’d expect. It seems there must be an explanation that goes beyond entropy.

Firstly, I’m going to assume that you are presupposing a physicalist ‘everything.’ If you want to get into transcendent counterarguments, then they are many and varied since we can start talking about things like volition and desire. In a physicalist universe, we’re just stuck with process. So from that standpoint, here’s my counterargument.

What’s the difference? What is the functional difference between a random brain formed from the ether and existing due to a random slurry of chemicals that just happened to form some sort of thinking thing and what we’ll call a normal conception of a brain existing in a meatbag and existing due to a random slurry of chemicals that just happened to form some sort of thinking thing. Where exactly do you see a qualitative difference? We already can be reasonably well-assured that our senses are only approximate and our memories and way we perceive the universe are flawed, so what does it matter if they are flawed by a little or flawed by a lot? I guess there’s a certain amount of pleasure to be gained from thinking that you have a somewhat reliable conception of the universe, but realistically, you’re going to think that regardless. The dirty secret of empiricalism is that it treats our senses as axiomatic when we know they aren’t and we just hope that they are close enough to work. If they aren’t, then it all falls apart. If you’re simply uncomfortable with the idea that you aren’t sure, then “Get used to disappointment,” Humperdink. That’s the crux of existentialism. We are always unsure and never know what the truth or best thing is, but we are forced to act anyway. I’m a Kierkegaardian by proclivity, so my advice is to just accept your unsurety and take a leap of faith.

Yeah, random quantum fluctuations that just happen to form a working brain out of unliving matter? What’s the difference between that and life evolving out of the primordial soup?

The other problem is that the argument presupposes that a real universe exists in which a brain could spring into being out of random virtual particles. How do we know how virtual particles work? Is it…by observing the universe and figuring it out? Except if we’re just a random brain thrown together by random quantum fluctuations, with fake memories and fake sense impressions formed by the same random quantum virtual particles, then such a brain’s ideas about how the universe actually works are sure to be false. Including that brain’s ideas about how brains could be randomly created by random quantum whatevers. That brain’s theories about how the universe works would have no relation to the actual working of the universe.

So, you are a brain sitting here, and this thought about how brains might randomly appear in the universe has somehow entered your brain. How did it do so? Did it do so because some other brain observed the universe and formulated this theory about how this is a possibility, and then communicated the idea to your brain? Or did your brain just appear in an empty universe by accident, with this thought randomly implanted in it about how brains might appear in an empty universe by accident? And your brain experiencing this momentary existence and thoughts is almost certainly going to go back into the quantum foam in the next nanosecond?

How exactly could your randomly assembled brain form this correct theory about how brains could arise randomly?

Here’s the thing. I agree that the brains and senses we have, which are the product of evolution, are fallible. They don’t impart absolute truth upon us, they’re just machines that give the meatbags they’re part of a slightly higher chance of replication before disintegration. But the simplest way to give your meatbag a better chance of replication is by some sort of correspondence between the actually existing universe and the internal model and instincts of the brain sensing the universe. If your brain can feel heat and avoid fire, feel hunger and eat, feel thirst and drink, and deposit gametes in an environment likely to lead to the development of those gametes, then there will be more of that sort of brain in future generations, and fewer brains that don’t.

And of course we have very good evidence that our brains are pretty good and understanding the environment we evolved to survive in, but pretty terrible and understanding parts of the universe that didn’t matter to our replication. So we don’t understand relativity, we can’t sense all sorts of electromagnetic radiation, we get confused about whether the Earth is flat or spherical, we can look at a picture of a human female and become sexually aroused even though there isn’t really a human female present, and on and on. This is why we need telescopes and Geiger counters and voltage meters and so on, that convert the phenomenon we can’t sense directly into ones we can sense directly.

Of course, it could be that this is all nonsense, and there really is absolutely no correspondence between our senses and thoughts and the actual universe. If somebody thought this was true, why would they bother talking about it on the internet? It’s just solipsism, which needs no refutation.

Taken in isolation, the soup method is vastly more likely. And if nothing else, having a complete prokaryotic cell pop into existence to jumpstart evolution is still vastly more likely than a whole human brain.

The problem is that the primordial soup seems to require an entire universe of support infrastructure, and that is vastly less likely than the single brain. And projected back to the Big Bang singularity, things get even less likely.

No one yet has a good solution for the Big Bang entropy problem. Boltzmann brains are just a thought experiment to reject one possibility (that the Big Bang was just a low-probability fluctuation).

Sean Carroll goes over a lot of this stuff in From Eternity to Here.

I think that the proper counterargument to the simulation hypothesis is not that the simulation hypothesis is false, but that it doesn’t matter. We find ourselves in some sort of a world: Very well, then, let us determine the rules which that world follows. Why should we care whether those rules are the rules of a simulation rather than of a “real” world? And in what sense is a simulation not “real”?

I think this is incorrect. If we think that it is more likely that we are in a simulation than reality than we would want to behave differently. You would want to cater to the people playing the game and keep them happy and interested so they keep the simulation going (and you alive.)

  1. Make important and famous people feel engaged.
  2. Do interesting things that get lots of attention and require a response from famous and important people.
  3. Keep key events, like big parties and wars and such going as long as possible.
  4. Cash in your retirement, and avoid long term planning. It is unlikely that the simulation will continue past the point where it create a simulation within a simulation. At the current pace of technology this will probably be somewhere around 2050 or so. So don’t worry about anything beyond that.
  5. Strive to become a super fascinating, exciting, fun, dangerous or otherwise notable person because then maybe there is a chance that you will be copied into the next simulation, or maybe even yanked out of the simulation and incarnated in reality, just because you are so fun and exciting.
  6. No matter what you do, DO NOT read about Roko’s Basilisk. Don’t do it. You have been warned. If you do, you will be doomed to an endless eternity of torment or enslavement. So, don’t do it. Seriously.

The very fact that a real universe is indistinguishable from a simulated universe makes my brain hurt. I find it very difficult to accept the argument that we ought to be curious enough to explore the universe and figure out how it works, but not curious enough to wonder at whether we’re in a simulation or not.

Does it matter?

Does it make any real distinction on our reality? Is there any difference if this universe is real or simulated?

Before answering those questions, what you’ve got is a fundamentally useless philosophy.

Not really, this logic doesn’t follow, because it depends on who is running the simulation, and why.

Perhaps it’s some kind of experiment, and as soon as too many people are cognizant of it being a simulation it has to be terminated. Perhaps it’s to see whether some interesting event happens, therefore making such events happen could result in it being shut down sooner than otherwise.

But maybe being shut down is a good thing, because the simulators know how to transfer consciousness from one avatar to another, and the next simulation after this one is Super Great World.

We don’t know and can’t know. The knowledge of “This is a simulation”, in itself, would actually give us no guidance at all on how to behave.

The philosophical issue that since all experience is subjective one cannot possibly know anything real and all experience is essentially one big hallucination is interesting, but a sidetrack to the original question, which is what to make of the fact that the physical parameters of the universe in general, and in particular the circumstances that currently support human life, seem vanishingly small, so how come we are here talking about it? This is the so-called “anthropic principle”. There are several counterarguments to this, but the simplest at this stage is that nobody really knows enough to make confident predictions about what is or isn’t likely in “near-infinite numbers” or in multiple universes or on “universal time scales”. Before talking about that I might ask what specifically is the nature of dark energy, etc.

We don’t know. Sure. The absence of certainty doesn’t stop one from making educated guesses.

Do you think we are in a simulation? Let me ask, does Trump seem like you and me, or does he seem like a 13 year old kid playing a game?

Do you have literally any frame of reference for this? There’s no “educated” to this guess - Trump’s existence is entirely consistent with what we know about the world, but we know literally nothing about any hypothetical universe that can/does simulate our universe.