I pitched this idea to Alex Pruss a couple years ago. (In my version, the fact that I'm not a BB is taken as a datum which is more likely on Christian eschatology than on "secular eschatology" involving heat death etc. Not sure this is the best framing though.) Another relevant verse is 2 Peter 3:10---"But the day of the Lord will come like a thief. The heavens will disappear with a roar; the elements will be destroyed by fire, and the earth and everything done in it will be laid bare."
he said that the argument had force, unless the opponent accepts a form of materialism where thought/consciousness constitutively depends on evolutionary history (say, because mentality requires teleology and teleology is grounded in selection history). In that case, BBs wouldn't be conscious. I think (i) it's crazy to think that consciousness constitutively depends on the distant past, but anyway (ii) the same problem arises for such views---just replace boltzmann brains with bigger boltzmann systems (local environments that spontaneously arise and last long enough get the right selection history etc.). It's similarly a datum that we're not in such a Boltzmann bigger-things, and for the same reasons these will eventually outnumber non-Boltzmann subjects given secular eschatology.
Your "core puzzle" doesn't seem very puzzling to me. Point 1 is not self-evident at all. Assuming Boltzmann brains are possible, why shouldn't I believe that I'm one of them? I have no evidence that I'm not a Boltzmann brain. And Point 2 is also not straightforward at all. Even if Boltzmann brains are possible (which I'm not convinced they are), it still seems like they would be exceedingly rare, probably much rarer than non-Boltzmann brains.
For that reason, I don't think the Boltzmann brain "problem" is much of a problem at all for atheists.
If you were a Boltzmann brain, odds are very good you'd be blacking out right now as you freeze to death and you shouldn't trust your reasoning that told you you're a Boltzmann brain. Also, your conscious experience probably wouldn't be coherent but would be random chaos.
??? Sounds like we have an easy solution to the Boltzmann brain problem right here!
How can you possibly assert that the problem is so insurmountable that we need to posit the Second Coming to solve it, and then dismiss it in two sentences of "your experience disproves this."
I didn't say that! What I said was that Christians have a nice solution not that this is the only solution.
That your experience proves ~P doesn't mean we shouldn't look for an explanation of ~P. Imagine on our best theory of physics, 99.999999999999999% of people would be green. But you're not green. It's true that experience proves you're not green, but we'd still want some story about why it is that you are not green that doesn't make it a huge coincidence.
I see. So the argument is not the Boltzman Brain skepticism argument. Fair enough.
But if we *can* notice that we are not a Boltzmann brain, if and only if we are not a Boltzmann brain, then the Anthropic argument seems to work. Under any theory of physics, there will be some non-Boltzmann humans. So it's not surprising that we notice that we are not Boltzmann brains. 100% of people who "notice" anything are not Boltzmann brains.
This isn't like the 10 royal flushes in a row example. In that case, you can notice or not notice that you didn't get 10 royal flushes either way, so noticing that you got 10 royal flushes in a row is a very special event indeed. One that requires explanation.
But imagine there were 10↑↑↑↑↑10 people each looking at a different random number generator ranging from 1 to 10↑↑↑↑↑10. They are told that they will instantly die if their generator does not return a "1." Let's say you survive. I don't think that this is grounds for believing that something supernatural must have occurred, even though the chances of you surviving were 1 in 10↑↑↑↑↑10. There was a 63.2% chance that *someone* would survive, and there was nothing special about you.
The idea behind Boltzmann brains is that, a human brain experiencing something is a certain low-ish entropy arrangement of matter; in the far future as time goes to infinity you should expect to see small fluctuations in entropy of arbitrary size: even fluctuations to pretty low entropy have some small probability of happening so in infinite time, they will happen infinitely often. This includes fluctuations to low-ish entropy states that include brains experiencing things.
So, infinitely often, in the distance future, a bunch of random stuff in the universe will, by complete coincidence, assemble itself into a physical structure that is sufficient to give rise to the experience of thinking to itself "I am a human being observing X", for any given X, for a brief moment before fading away again.
More "minimal" configurations are more likely, so "a human brain having it's visual cortex stimulated in a way that it perceives as seeing a dog" is more likely than "a human being and a dog, such that light from the dog stimulates the human's eyes, which pass the signal to the brain...", so for any given experience a human might have, it's easier for the universe to throw up a cheap simulacrum of a human having that experience than an actual human having that experience.
So it's, by construction, impossible to have evidence you're not a Boltzmann brain: every human being having the experience "I am a human observing evidence I'm not a Boltzmann brain" is much lower entropy, and thus less likely, than a brain having the correct electrochemical conductivity to think to itself "I am a human observing evidence I'm not a Boltzmann brain", just... without the human and without the evidence.
How rare these actually are depends on what you actually think the minimal entropy is for something that mimics a human brain in the relevant way. I personally think it may turn out that the minimum entropy to have a *conscious* experience of something is, more or less, the entropy of a human observing it, but it's all quite speculative
This is a fun idea. But I’m not sure that BB’s can ever exist in a Christian (or any cogent metaphysical framework) because BB’s presuppose that consciousness is reducible to the brain. Since it obviously isn’t, the question then arises how any BB’s are metaphysically possible as the hypothetical seems to encompass numerous category errors about “brain” and “consciousness.”
It presupposes BBs are *caused* by the brain, not reducible to it. A dualist atheist will still generally hold that if you have a brain randomly fizz into existence, it will give rise to consciousness.
I don’t hold that BBs are caused by the brain. Unless I’m misunderstanding (which I probably am) this sounds like epiphenominalism; I’m also not a dualist!
Yeah, this is a good point; Boltzmann brains only make sense under physicalism, what's the point of treating them under theism?
Although, you could I guess have non-physicalist analogues--if anything, the problem might be more serious under non-physicalism. If there are no physical preconditions for a conscious experience, we don't even need to wait for a high-entropy far future, we could just have arbitrary consciousness-moments popping up at any given time?
Why do BB's only make sense under physicalism? It seems that an emergent dualism (where the mind is generated by the brain, even if not reducible to it) would also work.
Precisely. An epiphenominalism also allows for BB’s but a highly Platonic and monistic ontology does not (God is Consciousness itself, being itself, good itself, and so forth).
I don't know enough about the relevant physics, but here are two thoughts:
1.) Maybe the big crunch is gonna happen and the future is finite (I think generally this is thought to be less likely than an infinite future).
2.) The universe keeps expanding. Maybe after some finite time T in the future, the universe becomes extremely dilute (think 1 photon per cubic lightyear or something) and the probability of generating a Boltzmann brain over time is therefore falling. If it's falling fast enough, maybe there is only a finite expected number of Boltzmann brains over the entire future of the universe.
The second option is pretty speculative, could be I'm way off base.
Essentially the problem is "solved" by any belief that reality post-heatdeath will be different than the scientific understanding described in the post. I guess you can say "Jesus will come again and god will change physics after that" as one way that our understanding is wrong, but that seems way less likely than other possibilities.
Maybe after the heat death a new big bang happens. Maybe after heat death reality is infinite but static (there is no 2 in an infinitely large set of ones). Maybe our best understanding of physics and reality is still wildly ignorant and true possibilities are incomprehensible to us, or we're nowhere near figuring them out.
Or even under the proposed understanding, you could be a boltzman brain that randomly popped out of the fuzz, or maybe entire universes can pop out of the fuzz and that's where we are. If it's infinite there are an infinite number of those "boltzman universes" (hopefully that's not already a term I'm redefining)
A problem with the second option is that it doesn't matter how fast the probability of generating Boltzmann's brains falls if the future of the universe is infinite. Something with the tinest probability you can imagine will still happen an infinite number of times over an infinite future. The only way the number of Boltzmann brains doesn't massively exceed the number of non-Boltzmann brain observers is if time literally comes to an end.
That's not true, at least not in the generality you seem to have in mind. For instance, the Borel-Cantelli lemma states that if E_1, E_2, ... are independent events [EDIT: independence is not necessary] whose probabilities sum to a finite number, the probability of infinitely many events happening is 0.
Now consider the following simplified universe: it is composed of time intervals [0,1], [2, 3]... and the probability of a Boltzmann brain being generated in [t, t+1] is, say, exponentially small: ~ 2^-t. Then
sum_t P[boltzmann brain in [t, t+1]] = 2 < infty,
so by Borel-Cantelli, only finitely many Boltzmann brains will appear almost surely. (It would be interesting to work out the precise distribution of how many there are, but I'm just typing this quickly.) Of course here I'm assuming that different time intervals are independent, which is an idealization, so take everything with a grain of salt; the point is just that a fast decay in probabilities can ensure that only finitely many events occur.
"The Flying Spaghetti Monster as a Solution to the Boltzmann Brain Problem"
When the FSM arrives and turns the universe into pure infinite pasta, He will set things up where no brains will arise in any of the noodles, so we can be confident that we aren't some kind of Bucatini Brain. Thanks be to the FSM
I don't know if this actually helps: I'm not sure exactly what is meant to come after the second coming, but my understanding is that people's consciousnesses will continue to exist for eternity, which implies a continuing forward motion of time after the second coming. But I believe it's still the case that our best idea for what distinguishes a "future direction of time" is increasing entropy, so I think you're either bound to believe that entropy continues to increase after the second coming, or that the state of affairs afterwards has no real directionality in time
"BB forming processes" is the increase of entropy; since increasing entropy is the process by which, in MWI, universes branch, does that mean that in heaven, macroscopic systems can be easily observed to be in superposition.
I know you don't think consciousness is physical, but TBH it's considerations like this that make me convinced that's wrong: that there are important places in physics where our basic intuitions about consciousness are coupled to entropy makes me very skeptical that you can subtract entropy and still have any idea of what consciousness even is: the fact that we experience time in a directional way; the fact that our intuition rebels against experiencing a superposition.
To me, "you have consciousness but no entropy" is almost a reductio: if that's sensible, then why do we need MWI to make sense of how the classical world emerges from the quantum? Why do we find out puzzling that the laws of physics don't obviously pick out a direction of time?
It's not specified much what comes after the Second Coming, but everyone is *bodily* resurrected, so time will still at least sort of exist for ex-mortals, but the material Universe we have now will be totally destroyed. It seems intuitively quite clear that there can't be increasing entropy in Heaven, so I think either (1) the question doesn't even make sense, Heaven isn't made out of matter that follows laws in anything like the ways we know from the material universe (2) the question makes sense and indeed time does not exist in the same kind of sense in Heaven. I tend to think both are probably true although it's a matter of faith that the rewards of Heaven must be, in some sense, infinite--there still must be progression of experience in some way or other.
The New Testament conceives of “Heaven” as a place with a spatio-temporal location which can accommodate the physical, resurrected body of Christ, be visited by human beings in their own fleshly bodies (see 2 Corinthians 12:2-4) and can be accessed and exited by movement upwards (the ascension) and downwards (the parousia) through the sky.
No, that's not accurate. Heaven is most certainly not within either time or space, though certainly in some sense it can occupy the bodies of the resurrected (Christ and, eventually, everyone) and the Apostles report experiences a physical Ascension. The New Testament contains only the seed of Christian theology; only a fundamentalist would suppose it's appropriate to try to draw such conclusions from solely Scriptural sources.
Why did Jesus float into the sky to return to the Father? Why is he coming “in the clouds” at the judgment?
William Lane Craig postulates that Jesus physically ascended into the sky until he was out of sight of the apostles at which point he was translated out of the space-time universe.
But the much more parsimonious explanation is that the authors of the New Testament simply shared the very incorrect ideas about the organization of the cosmos that were current in their milieu. Understandable for their time and place, but very difficult to explain on the assumption they were inspired by God to teach without error.
Of course the apostles were not aware of the Copernican model of the solar system, if that's what you mean. It's not at all difficult to explain. The authors of the Gospels were not inspired to teach the modern model of the Universe, which would have been impossible for them to do in any number of ways; they were inspired to teach the Gospel. The Gospels do not in fact *teach* the Aristotelian model of the Universe, something that I very much doubt even the rather erudite Luke and Paul knew much about. They teach that they saw Jesus rise into the air and then disappear behind a cloud. That is an awfully vast leap from the supposition that Heaven is located above the sky and accessible by vertical motion. Even the Aristotelians would hardly have understood what you meant by the second prong of that hypothesis, even if they accepted the first in a broad sense accounting for their very different conception of space--the very notion of physical *motion* occurring in the superlunar realm in the same sense as it does here was not recognized as sensible until the modern era.
>The authors of the Gospels were not inspired to teach the modern model of the Universe, which would have been impossible for them to do in any number of ways; they were inspired to teach the Gospel.
The math may have been beyond them (then -- is anything impossible for the Lord?) but it would have been simple to give a simple sketch of the true organization of the solar system, comparable to that taught to small children today. And a powerful proof it would have been, when it was later confirmed by scientific investigation. The apostles can hardly be faulted for not figuring out that prevailing models of the universe were false, and thereby assuming them in their writings. But GOD can be faulted for permitting them to persist in error he was more than capable of correcting. Creationists like to say, "If we can't trust the Bible in matters of natural sciences, why should we trust it in matters of salvation?" Obviously I disagree with creationist claims about the natural world, but I think they're spot on with that question.
> The Gospels do not in fact *teach* the Aristotelian model of the Universe, something that I very much doubt even the rather erudite Luke and Paul knew much about.
Maybe not, in the sense most people today don't fully understand the Copernican model but can still tell you "the earth revolves around the sun" and maybe sketch you a simple diagram of the solar system remembered from 3rd grade. Paul's reference to "the third heaven" assumes the celestial spheres.
>They teach that they saw Jesus rise into the air and then disappear behind a cloud. That is an awfully vast leap from the supposition that Heaven is located above the sky and accessible by vertical motion.
I don't think it is. Actually, I think it's the only model that makes sense of the ascension. Why ELSE would Jesus rise up into the sky to return to the father? Not rhetorical -- I'm seriously asking. Do you believe that when Luke describes Jesus being "lifted up" into the clouds, he is describing a literal event in history, in which some force raised Jesus of Nazareth off of the surface of the planet and up into the lower atmosphere? If so, why did that happen? What is the significance of that particular direction of motion?
>the very notion of physical *motion* occurring in the superlunar realm in the same sense as it does here was not recognized as sensible until the modern era.
Perhaps for the philosophers, but on the "folk" understanding the gospel authors were working from, that doesn't seem to be the case. The Ascension of Isaiah, almost contemporaneous with the gospels, describes Isaiah's ascension up through the various levels of Heaven, bodily. He even gives physical measurements: "the height from the third to the fourth heaven was greater than from the earth to the firmament." It seems Paul is describing something similar in his letter to the Corinthians, and it makes sense of the much more famous ascension of Jesus. We know the organization of our universe is not like this, so I think it is a big problem that the inspired authors of scripture believe that it is.
Yeah this is what I'm getting at: I don't know how you have progression of experience without entropy, so either this "solves" the problem by saying, (1) don't extrapolate the laws of physics infinitely far into the future, which is fine but doesn't really get much extra from the second coming; it's basically just, "Boltzmann brains don't exist because the world of maximal entropy is never reached", and the second coming is just one way of never reaching it, or (2) by proposing a new notion of time that is separate from entropy, which, sure, great, but what is this *physically*? I can also say, maybe BBs don't exist because after some point we still have something that behaves like time but isn't associated with increasing entropy, but without putting meat on those bones, it's a stretch to say it "solves" the problem.
Yeah, it's probably not that helpful from a non-Christian perspective, but a Christian would probably not feel particularly tempted to try to speculate about the physics of Heaven, that being pretty clearly placed beyond our conception.
That's fine, but it's not clear to what extent that functions as a solution of a physical puzzle: "something weird that I can't explain happens" has very little *explanatory* punch.
It's just part of Christian belief. The Second Coming is the occasion of the end of the world, this world is fallen, Heaven and Hell already exist and we have no particular information that God will make new ones after the end of the world, etc. I think it would be conceivable to imagine the universe profoundly transmuted rather than utterly destroyed, but it probably becomes a semantic difference. It's going to be a very different place to allow immortality to resurrected human bodies, among other things.
OK, that's interesting. N.T. Wright made some arguments about the 'renewal' of the world, as opposed to transcendence to another realm, so I thought there was some debate. I'm not sure if it's an entirely semantic difference. The picture he paints seems closer to something like an ideal version of this world, as opposed to a completely transformed one.
It's entirely possible I'm getting a bit out over my skis here; I'm not an Anglican but Wright is quite erudite and seems rather orthodox for an Anglican. I do think that either way it's clear that there's no reason to expect the future world not to be well outside the imagination of the physics that applies in this one.
once in a rare while a B-Brain pops up and persists long enough to sustain within its brain a Cosmos Sim, from start to end. i know, i know - we're not likely in *that* brain. but wouldn't it be cool?
Fizzling into existence is shortly followed by fizzling out, in most cases, and that solves the problem. Most BB's are momentary. Extended BB's are rare , and rarer than ordinary brains. If you are conscious for more than a than a few seconds , you are probably not a BB.
Putting on my hypothetical Christian hat to say that Matthew 24 is probably not about the second coming! The most plausible interpretation, imo, is that he's symbolically referring to the destruction of the Temple in 70 AD. Doesn't really impact your point but I've got to stand up for Preterism!
I honestly really appreciate you trying to reconcile natural theology with Christian theology. I don't agree with it at all, but this is an intellectually respectable effort.
> Bad news: if there’s only a finite period of initial stability, before an infinite period of disorder, then there will be vastly more Boltzmann brains than normal brains.
The conditions necessary to form a Boltzmann brain become less likely the more dilute and the colder the universe gets. We don’t understand the physics around extremely unlikely quantum events (Iron stars decaying or fusing in a way that forms a conscious machine 10^1000 years in the future or so), or if there’s Proton decay which would essentially guarantee matter will become more dilute in the near-infinitely far future.
Thus we can’t really say much about the probability of Boltzmann brains. If in the limit of time their probability of forming approaches zero, either due to the dilution of matter or cooling of matter to a level without enough energy to form into a conscious being, then it would be extremely unlikely anyone is a Boltzmann brain.
When i read your steelmanning christianity article i for my own evaluation revised some of your estimates downwards for various reasons, a few zeroes came off. This seems reasonably persuasive to me so, perhaps this is good for 100/1 evidence in favour of christianity?
What do we define as a brain? Is it something that exhibits intelligent thoughts or patterns of behavior? If so, something we say doesn't have a brain (like a tree or a jellyfish) is essentially a brain in itself. Although they don't have any defined tissue substrate that can be defined as a brain, like we do, they still exhibit intelligence. Why not refer to these things as Boltzmann brains? Afterall, there is an inordinate amount more of intelligent yet non-brained organisms when accounting for every single one of them. Apparently there are more than 3 trillion trees in the world. The world has already become infinitely more interpersonally disordered since the enlightenment period and the Byung-Chul Han quantification of all we know. Is that evidence that the second coming has already happened and we are currently experiencing the fall?
Notable that BBs wouldn't be a problem at all under the cosmology that the New Testament writers were working with, that being the old Aristotelian model of earth at the center of the concentric celestial spheres, through which Christ will descend to subdue the powers of the sublunar realm. It's a very small universe, so infinities don't rear their ugly heads
Are cosmic cyclic models (eg. Penrose CCC/Big Crunch/Baby Universe) independently motivated by physical facts, or are they typically proposed to avoid these kinds of philosophical problems?
Penrose seems to think that the CCC is the most likely explanation for certain features of the Cosmic Microwave Background. I remember him pointing specifically to supposed signs of supermassive black hole collisions and the gravitational 'ripples' they create, which he thinks come from a previous universe. His interpretation is not popular, but he seems motivated mostly by empirical considerations.
"You should expect your vision to begin blacking out as you freeze in some dark celestial void. But that’s not what you observe"
Wouldn't more void-resistant brains be strongly selected for over the lifespan of the universe? Near-perfect reversible computing and a strong outer membrane keeping pressure and energy in would drastically lengthen the lifespan of a BB so experiencing the fizzling out as you boil off into space actually shouldn't be expected I think. They don't have to resemble human brains at all!
Yes I'm not talking about evolution but rather boltzmann brains that aren't simply identical to human brains. For example, there's no reason why a clockwork BB made of exclusively bronze gears or a digital one made of silicon semiconductors wouldn't come into existence. This makes me think that over time as more fragile BBs come and go the ones that would eventually populate the space would be ones that have ultra long lived forms
I pitched this idea to Alex Pruss a couple years ago. (In my version, the fact that I'm not a BB is taken as a datum which is more likely on Christian eschatology than on "secular eschatology" involving heat death etc. Not sure this is the best framing though.) Another relevant verse is 2 Peter 3:10---"But the day of the Lord will come like a thief. The heavens will disappear with a roar; the elements will be destroyed by fire, and the earth and everything done in it will be laid bare."
What did he say?
he said that the argument had force, unless the opponent accepts a form of materialism where thought/consciousness constitutively depends on evolutionary history (say, because mentality requires teleology and teleology is grounded in selection history). In that case, BBs wouldn't be conscious. I think (i) it's crazy to think that consciousness constitutively depends on the distant past, but anyway (ii) the same problem arises for such views---just replace boltzmann brains with bigger boltzmann systems (local environments that spontaneously arise and last long enough get the right selection history etc.). It's similarly a datum that we're not in such a Boltzmann bigger-things, and for the same reasons these will eventually outnumber non-Boltzmann subjects given secular eschatology.
Your "core puzzle" doesn't seem very puzzling to me. Point 1 is not self-evident at all. Assuming Boltzmann brains are possible, why shouldn't I believe that I'm one of them? I have no evidence that I'm not a Boltzmann brain. And Point 2 is also not straightforward at all. Even if Boltzmann brains are possible (which I'm not convinced they are), it still seems like they would be exceedingly rare, probably much rarer than non-Boltzmann brains.
For that reason, I don't think the Boltzmann brain "problem" is much of a problem at all for atheists.
Unbeknownst to you, I actually AM a Boltzmann brain. Checkmate, Theist! Haha very based.
If you were a Boltzmann brain, odds are very good you'd be blacking out right now as you freeze to death and you shouldn't trust your reasoning that told you you're a Boltzmann brain. Also, your conscious experience probably wouldn't be coherent but would be random chaos.
??? Sounds like we have an easy solution to the Boltzmann brain problem right here!
How can you possibly assert that the problem is so insurmountable that we need to posit the Second Coming to solve it, and then dismiss it in two sentences of "your experience disproves this."
I didn't say that! What I said was that Christians have a nice solution not that this is the only solution.
That your experience proves ~P doesn't mean we shouldn't look for an explanation of ~P. Imagine on our best theory of physics, 99.999999999999999% of people would be green. But you're not green. It's true that experience proves you're not green, but we'd still want some story about why it is that you are not green that doesn't make it a huge coincidence.
I see. So the argument is not the Boltzman Brain skepticism argument. Fair enough.
But if we *can* notice that we are not a Boltzmann brain, if and only if we are not a Boltzmann brain, then the Anthropic argument seems to work. Under any theory of physics, there will be some non-Boltzmann humans. So it's not surprising that we notice that we are not Boltzmann brains. 100% of people who "notice" anything are not Boltzmann brains.
This isn't like the 10 royal flushes in a row example. In that case, you can notice or not notice that you didn't get 10 royal flushes either way, so noticing that you got 10 royal flushes in a row is a very special event indeed. One that requires explanation.
But imagine there were 10↑↑↑↑↑10 people each looking at a different random number generator ranging from 1 to 10↑↑↑↑↑10. They are told that they will instantly die if their generator does not return a "1." Let's say you survive. I don't think that this is grounds for believing that something supernatural must have occurred, even though the chances of you surviving were 1 in 10↑↑↑↑↑10. There was a 63.2% chance that *someone* would survive, and there was nothing special about you.
The idea behind Boltzmann brains is that, a human brain experiencing something is a certain low-ish entropy arrangement of matter; in the far future as time goes to infinity you should expect to see small fluctuations in entropy of arbitrary size: even fluctuations to pretty low entropy have some small probability of happening so in infinite time, they will happen infinitely often. This includes fluctuations to low-ish entropy states that include brains experiencing things.
So, infinitely often, in the distance future, a bunch of random stuff in the universe will, by complete coincidence, assemble itself into a physical structure that is sufficient to give rise to the experience of thinking to itself "I am a human being observing X", for any given X, for a brief moment before fading away again.
More "minimal" configurations are more likely, so "a human brain having it's visual cortex stimulated in a way that it perceives as seeing a dog" is more likely than "a human being and a dog, such that light from the dog stimulates the human's eyes, which pass the signal to the brain...", so for any given experience a human might have, it's easier for the universe to throw up a cheap simulacrum of a human having that experience than an actual human having that experience.
So it's, by construction, impossible to have evidence you're not a Boltzmann brain: every human being having the experience "I am a human observing evidence I'm not a Boltzmann brain" is much lower entropy, and thus less likely, than a brain having the correct electrochemical conductivity to think to itself "I am a human observing evidence I'm not a Boltzmann brain", just... without the human and without the evidence.
How rare these actually are depends on what you actually think the minimal entropy is for something that mimics a human brain in the relevant way. I personally think it may turn out that the minimum entropy to have a *conscious* experience of something is, more or less, the entropy of a human observing it, but it's all quite speculative
This is a fun idea. But I’m not sure that BB’s can ever exist in a Christian (or any cogent metaphysical framework) because BB’s presuppose that consciousness is reducible to the brain. Since it obviously isn’t, the question then arises how any BB’s are metaphysically possible as the hypothetical seems to encompass numerous category errors about “brain” and “consciousness.”
It presupposes BBs are *caused* by the brain, not reducible to it. A dualist atheist will still generally hold that if you have a brain randomly fizz into existence, it will give rise to consciousness.
I don’t hold that BBs are caused by the brain. Unless I’m misunderstanding (which I probably am) this sounds like epiphenominalism; I’m also not a dualist!
Sorry I meant consciousness.
Even if you're an idealist, presumably there is a distinct experiencer wherever there is what looks *from the outside* like a brain.
Yeah, this is a good point; Boltzmann brains only make sense under physicalism, what's the point of treating them under theism?
Although, you could I guess have non-physicalist analogues--if anything, the problem might be more serious under non-physicalism. If there are no physical preconditions for a conscious experience, we don't even need to wait for a high-entropy far future, we could just have arbitrary consciousness-moments popping up at any given time?
Why do BB's only make sense under physicalism? It seems that an emergent dualism (where the mind is generated by the brain, even if not reducible to it) would also work.
Yeah you're right, it only needs some kind of emergence from the physical, though I think the broader point still applies
Precisely. An epiphenominalism also allows for BB’s but a highly Platonic and monistic ontology does not (God is Consciousness itself, being itself, good itself, and so forth).
I don't know enough about the relevant physics, but here are two thoughts:
1.) Maybe the big crunch is gonna happen and the future is finite (I think generally this is thought to be less likely than an infinite future).
2.) The universe keeps expanding. Maybe after some finite time T in the future, the universe becomes extremely dilute (think 1 photon per cubic lightyear or something) and the probability of generating a Boltzmann brain over time is therefore falling. If it's falling fast enough, maybe there is only a finite expected number of Boltzmann brains over the entire future of the universe.
The second option is pretty speculative, could be I'm way off base.
I'm also ignorant of the physics.
Essentially the problem is "solved" by any belief that reality post-heatdeath will be different than the scientific understanding described in the post. I guess you can say "Jesus will come again and god will change physics after that" as one way that our understanding is wrong, but that seems way less likely than other possibilities.
Maybe after the heat death a new big bang happens. Maybe after heat death reality is infinite but static (there is no 2 in an infinitely large set of ones). Maybe our best understanding of physics and reality is still wildly ignorant and true possibilities are incomprehensible to us, or we're nowhere near figuring them out.
Or even under the proposed understanding, you could be a boltzman brain that randomly popped out of the fuzz, or maybe entire universes can pop out of the fuzz and that's where we are. If it's infinite there are an infinite number of those "boltzman universes" (hopefully that's not already a term I'm redefining)
A problem with the second option is that it doesn't matter how fast the probability of generating Boltzmann's brains falls if the future of the universe is infinite. Something with the tinest probability you can imagine will still happen an infinite number of times over an infinite future. The only way the number of Boltzmann brains doesn't massively exceed the number of non-Boltzmann brain observers is if time literally comes to an end.
That's not true, at least not in the generality you seem to have in mind. For instance, the Borel-Cantelli lemma states that if E_1, E_2, ... are independent events [EDIT: independence is not necessary] whose probabilities sum to a finite number, the probability of infinitely many events happening is 0.
Now consider the following simplified universe: it is composed of time intervals [0,1], [2, 3]... and the probability of a Boltzmann brain being generated in [t, t+1] is, say, exponentially small: ~ 2^-t. Then
sum_t P[boltzmann brain in [t, t+1]] = 2 < infty,
so by Borel-Cantelli, only finitely many Boltzmann brains will appear almost surely. (It would be interesting to work out the precise distribution of how many there are, but I'm just typing this quickly.) Of course here I'm assuming that different time intervals are independent, which is an idealization, so take everything with a grain of salt; the point is just that a fast decay in probabilities can ensure that only finitely many events occur.
That's cool. I didn't realise there was a boundary where the probability decline can result in a finite sum.
I actually misquoted the lemma (it has 2 forms), in our case the assumption of independence is unnecessary.
"The Flying Spaghetti Monster as a Solution to the Boltzmann Brain Problem"
When the FSM arrives and turns the universe into pure infinite pasta, He will set things up where no brains will arise in any of the noodles, so we can be confident that we aren't some kind of Bucatini Brain. Thanks be to the FSM
I don't know if this actually helps: I'm not sure exactly what is meant to come after the second coming, but my understanding is that people's consciousnesses will continue to exist for eternity, which implies a continuing forward motion of time after the second coming. But I believe it's still the case that our best idea for what distinguishes a "future direction of time" is increasing entropy, so I think you're either bound to believe that entropy continues to increase after the second coming, or that the state of affairs afterwards has no real directionality in time
Consciousness continues but BB-forming processes don't.
"BB forming processes" is the increase of entropy; since increasing entropy is the process by which, in MWI, universes branch, does that mean that in heaven, macroscopic systems can be easily observed to be in superposition.
I know you don't think consciousness is physical, but TBH it's considerations like this that make me convinced that's wrong: that there are important places in physics where our basic intuitions about consciousness are coupled to entropy makes me very skeptical that you can subtract entropy and still have any idea of what consciousness even is: the fact that we experience time in a directional way; the fact that our intuition rebels against experiencing a superposition.
To me, "you have consciousness but no entropy" is almost a reductio: if that's sensible, then why do we need MWI to make sense of how the classical world emerges from the quantum? Why do we find out puzzling that the laws of physics don't obviously pick out a direction of time?
It's not specified much what comes after the Second Coming, but everyone is *bodily* resurrected, so time will still at least sort of exist for ex-mortals, but the material Universe we have now will be totally destroyed. It seems intuitively quite clear that there can't be increasing entropy in Heaven, so I think either (1) the question doesn't even make sense, Heaven isn't made out of matter that follows laws in anything like the ways we know from the material universe (2) the question makes sense and indeed time does not exist in the same kind of sense in Heaven. I tend to think both are probably true although it's a matter of faith that the rewards of Heaven must be, in some sense, infinite--there still must be progression of experience in some way or other.
The New Testament conceives of “Heaven” as a place with a spatio-temporal location which can accommodate the physical, resurrected body of Christ, be visited by human beings in their own fleshly bodies (see 2 Corinthians 12:2-4) and can be accessed and exited by movement upwards (the ascension) and downwards (the parousia) through the sky.
No, that's not accurate. Heaven is most certainly not within either time or space, though certainly in some sense it can occupy the bodies of the resurrected (Christ and, eventually, everyone) and the Apostles report experiences a physical Ascension. The New Testament contains only the seed of Christian theology; only a fundamentalist would suppose it's appropriate to try to draw such conclusions from solely Scriptural sources.
Why did Jesus float into the sky to return to the Father? Why is he coming “in the clouds” at the judgment?
William Lane Craig postulates that Jesus physically ascended into the sky until he was out of sight of the apostles at which point he was translated out of the space-time universe.
But the much more parsimonious explanation is that the authors of the New Testament simply shared the very incorrect ideas about the organization of the cosmos that were current in their milieu. Understandable for their time and place, but very difficult to explain on the assumption they were inspired by God to teach without error.
Of course the apostles were not aware of the Copernican model of the solar system, if that's what you mean. It's not at all difficult to explain. The authors of the Gospels were not inspired to teach the modern model of the Universe, which would have been impossible for them to do in any number of ways; they were inspired to teach the Gospel. The Gospels do not in fact *teach* the Aristotelian model of the Universe, something that I very much doubt even the rather erudite Luke and Paul knew much about. They teach that they saw Jesus rise into the air and then disappear behind a cloud. That is an awfully vast leap from the supposition that Heaven is located above the sky and accessible by vertical motion. Even the Aristotelians would hardly have understood what you meant by the second prong of that hypothesis, even if they accepted the first in a broad sense accounting for their very different conception of space--the very notion of physical *motion* occurring in the superlunar realm in the same sense as it does here was not recognized as sensible until the modern era.
>The authors of the Gospels were not inspired to teach the modern model of the Universe, which would have been impossible for them to do in any number of ways; they were inspired to teach the Gospel.
The math may have been beyond them (then -- is anything impossible for the Lord?) but it would have been simple to give a simple sketch of the true organization of the solar system, comparable to that taught to small children today. And a powerful proof it would have been, when it was later confirmed by scientific investigation. The apostles can hardly be faulted for not figuring out that prevailing models of the universe were false, and thereby assuming them in their writings. But GOD can be faulted for permitting them to persist in error he was more than capable of correcting. Creationists like to say, "If we can't trust the Bible in matters of natural sciences, why should we trust it in matters of salvation?" Obviously I disagree with creationist claims about the natural world, but I think they're spot on with that question.
> The Gospels do not in fact *teach* the Aristotelian model of the Universe, something that I very much doubt even the rather erudite Luke and Paul knew much about.
Maybe not, in the sense most people today don't fully understand the Copernican model but can still tell you "the earth revolves around the sun" and maybe sketch you a simple diagram of the solar system remembered from 3rd grade. Paul's reference to "the third heaven" assumes the celestial spheres.
>They teach that they saw Jesus rise into the air and then disappear behind a cloud. That is an awfully vast leap from the supposition that Heaven is located above the sky and accessible by vertical motion.
I don't think it is. Actually, I think it's the only model that makes sense of the ascension. Why ELSE would Jesus rise up into the sky to return to the father? Not rhetorical -- I'm seriously asking. Do you believe that when Luke describes Jesus being "lifted up" into the clouds, he is describing a literal event in history, in which some force raised Jesus of Nazareth off of the surface of the planet and up into the lower atmosphere? If so, why did that happen? What is the significance of that particular direction of motion?
>the very notion of physical *motion* occurring in the superlunar realm in the same sense as it does here was not recognized as sensible until the modern era.
Perhaps for the philosophers, but on the "folk" understanding the gospel authors were working from, that doesn't seem to be the case. The Ascension of Isaiah, almost contemporaneous with the gospels, describes Isaiah's ascension up through the various levels of Heaven, bodily. He even gives physical measurements: "the height from the third to the fourth heaven was greater than from the earth to the firmament." It seems Paul is describing something similar in his letter to the Corinthians, and it makes sense of the much more famous ascension of Jesus. We know the organization of our universe is not like this, so I think it is a big problem that the inspired authors of scripture believe that it is.
Yeah this is what I'm getting at: I don't know how you have progression of experience without entropy, so either this "solves" the problem by saying, (1) don't extrapolate the laws of physics infinitely far into the future, which is fine but doesn't really get much extra from the second coming; it's basically just, "Boltzmann brains don't exist because the world of maximal entropy is never reached", and the second coming is just one way of never reaching it, or (2) by proposing a new notion of time that is separate from entropy, which, sure, great, but what is this *physically*? I can also say, maybe BBs don't exist because after some point we still have something that behaves like time but isn't associated with increasing entropy, but without putting meat on those bones, it's a stretch to say it "solves" the problem.
Yeah, it's probably not that helpful from a non-Christian perspective, but a Christian would probably not feel particularly tempted to try to speculate about the physics of Heaven, that being pretty clearly placed beyond our conception.
That's fine, but it's not clear to what extent that functions as a solution of a physical puzzle: "something weird that I can't explain happens" has very little *explanatory* punch.
I took it as "Christians already have reason not to believe Boltzmann Brains exist in large numbers", for which it seems quite satisfactory.
Boltzmann brains assume physicalism about consciousness, which Christians already reject, not clear why any other arguments are necessary.
Why are you so confident the material universe will be destroyed?
It's just part of Christian belief. The Second Coming is the occasion of the end of the world, this world is fallen, Heaven and Hell already exist and we have no particular information that God will make new ones after the end of the world, etc. I think it would be conceivable to imagine the universe profoundly transmuted rather than utterly destroyed, but it probably becomes a semantic difference. It's going to be a very different place to allow immortality to resurrected human bodies, among other things.
OK, that's interesting. N.T. Wright made some arguments about the 'renewal' of the world, as opposed to transcendence to another realm, so I thought there was some debate. I'm not sure if it's an entirely semantic difference. The picture he paints seems closer to something like an ideal version of this world, as opposed to a completely transformed one.
It's entirely possible I'm getting a bit out over my skis here; I'm not an Anglican but Wright is quite erudite and seems rather orthodox for an Anglican. I do think that either way it's clear that there's no reason to expect the future world not to be well outside the imagination of the physics that applies in this one.
once in a rare while a B-Brain pops up and persists long enough to sustain within its brain a Cosmos Sim, from start to end. i know, i know - we're not likely in *that* brain. but wouldn't it be cool?
Fizzling into existence is shortly followed by fizzling out, in most cases, and that solves the problem. Most BB's are momentary. Extended BB's are rare , and rarer than ordinary brains. If you are conscious for more than a than a few seconds , you are probably not a BB.
Putting on my hypothetical Christian hat to say that Matthew 24 is probably not about the second coming! The most plausible interpretation, imo, is that he's symbolically referring to the destruction of the Temple in 70 AD. Doesn't really impact your point but I've got to stand up for Preterism!
I honestly really appreciate you trying to reconcile natural theology with Christian theology. I don't agree with it at all, but this is an intellectually respectable effort.
> Bad news: if there’s only a finite period of initial stability, before an infinite period of disorder, then there will be vastly more Boltzmann brains than normal brains.
The conditions necessary to form a Boltzmann brain become less likely the more dilute and the colder the universe gets. We don’t understand the physics around extremely unlikely quantum events (Iron stars decaying or fusing in a way that forms a conscious machine 10^1000 years in the future or so), or if there’s Proton decay which would essentially guarantee matter will become more dilute in the near-infinitely far future.
Thus we can’t really say much about the probability of Boltzmann brains. If in the limit of time their probability of forming approaches zero, either due to the dilution of matter or cooling of matter to a level without enough energy to form into a conscious being, then it would be extremely unlikely anyone is a Boltzmann brain.
When i read your steelmanning christianity article i for my own evaluation revised some of your estimates downwards for various reasons, a few zeroes came off. This seems reasonably persuasive to me so, perhaps this is good for 100/1 evidence in favour of christianity?
Can i ask how much this increases your credence in christianity?
What do we define as a brain? Is it something that exhibits intelligent thoughts or patterns of behavior? If so, something we say doesn't have a brain (like a tree or a jellyfish) is essentially a brain in itself. Although they don't have any defined tissue substrate that can be defined as a brain, like we do, they still exhibit intelligence. Why not refer to these things as Boltzmann brains? Afterall, there is an inordinate amount more of intelligent yet non-brained organisms when accounting for every single one of them. Apparently there are more than 3 trillion trees in the world. The world has already become infinitely more interpersonally disordered since the enlightenment period and the Byung-Chul Han quantification of all we know. Is that evidence that the second coming has already happened and we are currently experiencing the fall?
For the argument it doesn't matter how we define a brain--however you define it, most of these on standard views will be non-genuine.
Notable that BBs wouldn't be a problem at all under the cosmology that the New Testament writers were working with, that being the old Aristotelian model of earth at the center of the concentric celestial spheres, through which Christ will descend to subdue the powers of the sublunar realm. It's a very small universe, so infinities don't rear their ugly heads
Are cosmic cyclic models (eg. Penrose CCC/Big Crunch/Baby Universe) independently motivated by physical facts, or are they typically proposed to avoid these kinds of philosophical problems?
I don't really know
Penrose seems to think that the CCC is the most likely explanation for certain features of the Cosmic Microwave Background. I remember him pointing specifically to supposed signs of supermassive black hole collisions and the gravitational 'ripples' they create, which he thinks come from a previous universe. His interpretation is not popular, but he seems motivated mostly by empirical considerations.
"You should expect your vision to begin blacking out as you freeze in some dark celestial void. But that’s not what you observe"
Wouldn't more void-resistant brains be strongly selected for over the lifespan of the universe? Near-perfect reversible computing and a strong outer membrane keeping pressure and energy in would drastically lengthen the lifespan of a BB so experiencing the fizzling out as you boil off into space actually shouldn't be expected I think. They don't have to resemble human brains at all!
There's no evolution of BBs--they just occassionally fizz into existence.
Yes I'm not talking about evolution but rather boltzmann brains that aren't simply identical to human brains. For example, there's no reason why a clockwork BB made of exclusively bronze gears or a digital one made of silicon semiconductors wouldn't come into existence. This makes me think that over time as more fragile BBs come and go the ones that would eventually populate the space would be ones that have ultra long lived forms
The fizzling solves the problems, anyway. Most BB's are momentary. Extended BB's are rare , and rarer than ordinary brains.