Are You a Boltzman Brain?

What do the @physicists think about this?

William Lane Craig also talks about this.

Here’s where the Boltzmann Brains come into the picture. In order to be observable the patch of order needn’t be even as large as the solar system. The most probable observable world would be one in which a single brain fluctuates into existence out of the quantum vacuum and observes its otherwise empty world. The idea isn’t that the brain is the whole universe, but just a patch of order in the midst of disorder. Don’t worry that the brain couldn’t persist long: it just has to exist long enough to have an observation, and the improbability of the quantum fluctuations necessary for it to exist that long will be trivial in comparison to the improbability of fine tuning.

In other words, the observer self-selection effect is explanatorily vacuous. It does not suffice to show that only finely tuned worlds are observable. As Robin Collins has noted, what needs to be explained is not just intelligent life, but embodied, interactive, intelligent agents like ourselves. Appeal to an observer self-selection effect accomplishes nothing because there is no reason whatever to think that most observable worlds are worlds in which that kind of observer exists. Indeed, the opposite appears to be true: most observable worlds will be Boltzmann Brain worlds.

I’m not sure what to make of this. Do we even know what consciousness is? How can we know if a Boltzman Brain is even possible, let alone more probable. I don’t get it.

First of a Boltzmann Brain is just an observer (a “self-aware entity”) that is created randomly out of probabilistic fluctuations. This could just be something that is physically identical to a human. In this sense, there is no need for consciousness to be defined; it’s just the idea that probabilistic fluctuations can in theory produce a human being.

The chances of this happening is of course very low, but given the multiverse, which by most account is infinite, this has to happen.

Now, Boltzmann Brains are created “directly” in situ out of thermal fluctuations, but this leaves out a lot of possible “Brains” that could be created out of probabilistic fluctuations. I am specifically referring to the fact that there could be a self-aware entity that is not created “directly” out of probabilistic fluctuations, but rather probabilistic fluctuations create the initial conditions that would then evolve into the self-aware entity. Perhaps a more encompassing definition of the Boltzmann Brain would also encompass these entities.

If so, then we are Boltzmann Brains, as the initial conditions for our Universe is seeded by probabilistic fluctuations at inflation.

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And of course, the usual point made about Botzmann Brains in a mutiverse is that it’s a whole lot more likely that random fluctuations could produce just one Boltzmann brain imagining a universe that a whole universe full of independent intelligent beings.

Ergo it’s a lot more likely, given the multiverse, that I am imagining you lot than that you exist.


This is how we see it, too. :slight_smile:

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Oh no you don’t…


I may be imaginary, but I’m still obstinate!

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There are actually people who believe in this? Because, as I understand it, even if you have a naturalistic view of the world, Boltzman Brain fails on so many levels. At least, in this universe.

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Does the argument for Boltzman brains require a multiverse?

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You are all chat bots that my grad students created to mess with me.


Truly! This is all about you, Joshua!! :rofl:


In that case you need better grad students.


Hey, I have to ask: are there people trying to prove this? And if there are, who are they trying to prove it to?

What makes you think they fail? These are just probabilistic statements.

Prove which statement(s) about Boltzmann Brains?

I was talking about the thing @jongarvey said, I don’t know why it didn’t show the quote.

OK there seems to have been some misconception on my part, I googled Boltzmann Brain and simply skimmed over it, so I was under the impression that it was a belief that it means that some people believed that, somehow only their own brain exists and that other people are just a part of their imagination. I should have read more carefully, I apologize.

No worries!

That said, the position you brought up positing that nothing but one’s own mind exist (often called the “brain-in-a-jar” or hard solipsism scenario) is quite reasonable to me. Now I am curious on why you think this position has problems.

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Well, since I’m neither a scientist nor a philosopher I’m gonna have to use layman’s common sense (which you’re gonna prove wrong :slightly_smiling_face:) and say the biggest problem (in my opinion) would be parentage, meaning, where did such a brain come from, how it was created etc.

I see. I there are many answers to this problem, for example:

  1. Topically, you can be created out of thermal fluctuations, ala a Boltzmann brain

  2. The existence of your brain is just a brute fact, aka you are just “there” - this is similar to some views in Christianity where God is taken as a brute fact.

  3. If you extend the scenario to allow for the existence of beings that you cannot observe, you can be created by such beings. For example, you can be a brain in a jar sitting in some lab, created by scientists that are unobservable to you.

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OK, first and third I can understand but wouldn’t the second require me to have kind of always been “there”? You know, was never created, would never end, just am?

Yup, which is why this is similar to how the existence of God is understood in some branches of Christianity. Note also that your statement

Already posits the existence of time, which is not necessary in these models.

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