What do rationalists think about the afterlife?

This question has little to do with LW-style rationality. The contrivance of postulating extra entities like souls becomes obvious once you accept that mind is a process in a living brain, affected by drugs, injuries, etc. You can, of course, postulate anything you want, but the odds are against you, and definitely not 50/50. See this illuminating debate, discussed here. More about the 50/50 fallacy you've fallen prey to.

Edit: fixed the debate video link to a better-quality one.

The reason for thinking that consciousness is a physical process of the brain is the remarkable correspondence we find between injuries to the brain or the introduction of various chemicals, and variations of conscious experience. That leaves open the possibility that consciousness is a physically separate entity for which the brain is the interface through which it moves the body and receives sensation from it, rather than brain processes themselves being consciousness. However most of the ground for that is undercut by the fact that some brain injuries severing parts of the brain from each other also appear to sever the corresponding parts of consciousness -- split-brain observations. It seems that it is not only components of consciousness that correspond to brain regions, but also their interconnection. The more we find out, the less role is left for the hypothesis of a separate consciousness to do any work. Like the old "God in the gaps" argument to defend theism against science.

That is the argument, but it is important to note what it does not solve. It does not solve the problem of what consciousness is -- of why there is any such thing in the world as experience, and how any physical process could produce it. Nobody knows the answer to that. (ETA: including non-materialists. "There are souls" is not an explanation of how they work.) In this it differs from the problem of God. There may be people who claim a direct experience of God in the same way as they have direct experience of themselves, but it does not seem to be common. Experience of one's own presence, on the other hand, is reported by almost everyone. Yet everything else we know about the world tells us that there cannot possibly be any such thing. We cannot even see what an explanation for experience would be.

There are those who point to some physical phenomenon that is present whenever consciousness is, and conclude, "that's consciousness". Unless they show how whatever it is produces experience, they have not explained consciousness. Most proposed solutions are of this form.

There are those who point to some more or less speculative physical process (e.g. quantum gravity in the microtubules) and assert, "that's consciousness". Unless they show how whatever it is would produce experience, they have not even speculatively explained consciousness.

There are those who take the apparently impossible magnitude of the problem as an argument that there is no problem, which is like a student demanding full marks because the exam was too hard.

There are those who claim to have realised that in fact they have no consciousness and never did (Buddhist enlightenment is often so described, and I believe that the psychologist Susan Blackmore has said something like this, but I can't find a cite). If they carry on functioning like ordinary people then they are claiming to be p-zombies, and if they don't, they've philosophised a tamping iron into their brain.

As for myself, I simply note the evidence above, the problem it leaves unsolved, and my lack of any idea for a solution. Yet it seems that few people can do that. Instead, as soon as they start thinking about the problem, they frantically cast about for solutions and latch onto something of one of the above forms. The problem is like a piece of grit in an oyster, provoking it to encyst it in layer upon layer of baroque encrustations that merely hide the problem instead of solving it.

My point in this post is that I don't see why we have reason to reject the 3 possibilities above.

We have as much reason to reject them as we have to reject the existence of a slice of chocolate cake in the asteroid belt.

People in the comments have just taken it as a given that consciousness resides solely in the brain without explaining why they think this.

Yes, this is a regrettably frequent error on this question.

"We have a number of situations in which we can hear music in this world e.g. Hitting play on your laptop. However this is just the data we have; there are many situations we don't know about. Can we really say that when a song stops, it doesn't continue somewhere else? Personally I see no reason to believe this. At best we're talking fifty-fifty here."

The situations that cause music to be heard are exceedingly complex and are not likely to happen in other parts of the universe by accident. Similarly, the situations which cause consciousness are exceedingly complex, involving so many substructures and modules working in some currently unfathomable way (Daniel Dennett suggests the need for competition ). Even if you think it's likely that all of the necessary parts exist elsewhere in the universe, that's like saying you think music exists somewhere else in the universe - it doesn't explain why you expect the music that stops here to keep on going elsewhere. There's nothing so special about consciousness that it probably just jumps out of the atoms it's being run on - that's magical thinking. Of course, if you are thing like that, maybe you are religious, and you have to contend with everything we know about the mind so far in cognitive science etc.

Not much has been said cuz there ain't much to say about things that don't exist. Your mind is what your brain does. When the brain stops, so do you. This isn't even advanced rationality - it's reductionism 101. I believe there was a Intelligence Squared debate on it just a few days ago that rehashed all the same old ground if you'd like a refresher. Here we go.

Giving a prior of .5 is ridiculous. Something for which you have no evidence and which breaks several known laws of physics should begin with a seriously tiny prior. You're being heavily influenced by social traditions.

Personal identity is an illusion. It's often a useful illusion, but when you're dealing with something outside the normal usage, it can go way off. It results in asking meaningless questions like "Where did we come from?", "Where do we go when we die?", and "Is the guy who came out of the teleporter the real me, or just my clone?".

I don't mean to say that suggesting the existence of an afterlife is meaningless. I just mean that we're using a flawed model that implicitly assumes an afterlife, when there's no reason to believe in one. You assume that you continue to be conscious, when in fact there is a conscious entity at a given point in space and time, and there may or may not be another further ahead in time. You tried to be more skeptical about it, but you're still given it even odds. Since we live in an ordered universe, it's clear that almost all possible beings don't exist, or exist less in some sense or something like that. It's not even odds.

There may well be conscious beings beyond what we normally interact with. The issue here is that they aren't ex-humans. We know that a human brain is an integral part of the human mind. We know what individual pieces do. If there is some part of the human mind that survives death, it's not going to work the same way after we die. The mind might be modular enough that it can exist with some low-level animalistic intelligence, but more likely it would break down completely. It's also pretty unlikely that there is such a thing in the first place. There are a lot of problems that would be associated with an incorporeal organ. For example, how do you hold it in place?

And finally, since we have no data, what can we say about the likelihood of our consciousness returning/remaining after we die? I would say the chances are 50/50. For something you have no data on, any outcome is equally likely

I don't think that's true. It's not that we have no data; we still have prior probability. And with that, all of our background knowledge that goes into that prior which function as data. Theories aren't argued in isolation!

Think about how many things need to be true in order for consciousness to "return" after we die, and if any of those things are false then the entire model fails (this is why Occam's Razor is a useful heuristic) Where does it go after we die? How does it get there? What contains it? What is the energy source for this non-bodied consciousness? How does this fit in with our current understanding of physics like laws of thermodynamics (most people who posit non-bodied consciousness unwittingly propose that consciousness is a perpetual motion machine)? Is it even accurate to call it "consciousness" if it cannot receive any sensory input? In other words, we need ears to hear, eyes to see, etc. but this consciousness would be without the brain structure necessary to process vibrations in the air into what we know as "sound". Is this model of consciousness specific to humans or to any of the higher primates (or even other intelligent species like dolphins or elephants), and why?

On the other hand, we don't need to suggest other laws of physics / theory of evolution for our current model of consciousness, and it has a satisfactory answer for all of the questions I asked above. So Occam's Razor is the mode of thought until we actually get more evidence in the non-bodied consciousness direction.

There's a lot of very bizarre death-related stuff some people here take seriously: future simulations of you recreated from historical data, "quantum immortality", big universe with copies of you existing very far away, us living in a simulation, and so on and so forth. It's just that the atheists who believe in such can't call that "afterlife" otherwise they wouldn't be atheists.

edit: I think there's also a very serious case of inconsistency. If you ask someone about "afterlife", they're pretty sure there's no afterlife, but if you come up with an elaborate narrative, for example one where the future AI uses all the digital data and backtracks a simulation of the world to recreate you, so when you die you just wake up in that AI's simulation - they're no longer nearly as sure.

People in the comments have just taken it as a given that consciousness resides solely in the brain without explaining why they think this. My point in this post is that I don't see why we have reason to reject the 3 possibilities above. If you reject the idea that consciousness could reside outside of the brain, please explain why.

Simply put: Occam's Razor, and lack of evidence.

More thoroughly: We have at best very weak evidence for an afterlife (non-verifiable near-death experiences, religious texts, and it being a generally common belief/hunch that it may exist), plausible explanations for why each of those weak sources of evidence would exist without a real afterlife (psychological effects of almost dying and general unreliability of minds in extreme situations, the fact that an afterlife makes a religious meme more powerful, and flat out hope/unwillingness to face the end respectively). All descriptions of a true afterlife conflict massively with the testable and prediction giving knowledge that science has found, and trying to make the two work together, if it is even possible, would give a much less simple theory.

"Returning" and "remaining" (as you put it in your last bullet point) are very different things. The latter seems to require that we are, or have, something like souls that, despite their immateriality and apparent complete inaccessibility to any sort of scientific investigation, are the true bearers of our identity and consciousness. This is very, very hard to square with (e.g.) the copious evidence that "the mind is what the brain does" and I think it's reasonable to regard it as pretty much refuted.

"Returning" is another kettle of fish entirely. It covers, e.g., (1) resurrection of the sort envisaged by religions like Christianity, (2) later reconstruction by some sort of superintelligent agent, and arguably (3) cryonics if that turns out to work. Not to mention other exotic options like (4) we are in a simulation and whoever's running it wants to resurrect us. Note that for some of these options our putative resurrection takes place entirely outside our world. Evidence for or against is going to have to be indirect (e.g., some guy turns up, works a sufficiently dramatic set of miracles, and explains that he is an emissary of the gods, who by the way are going to resurrect everyone whose surname begins with a vowel; or many things of this kind that might have happened fail to happen, constituting evidence against resurrection).

Mostly, though, the reason to reject resurrection (unless you happen to think you are in possession of some kind of divine revelation or something) is Occam's razor. Yeah, it might turn out that we're in the Matrix and the computers running it are going to give us all second chances, but that's a much more complicated possibility than that our world is "the" world. And no, the odds aren't 50/50, for the reasons others have given and linked to; you can't make everything equally likely on pain of inconsistency, and in-some-sense-on-average more complicated things must be less probable.

I think you'll probably find a strong (but not unanimous) consensus among LW-rationalists that: consciousness is a property of physical systems and doesn't involve immaterial souls (unless, e.g., you define those in some way reducible to properties of physical systems); it, or something "equally good", could exist on other substrates besides ours; "survival" (consciousness remaining after we die) is monstrously unlikely; "resurrection" (consciousness returning somehow after we die) is possible in principle and may some day happen to some people via technological wonders like "uploading"; there is no good reason to expect "resurrection" to be on offer to the human race at large and it should be regarded as very unlikely for Occamish reasons.

(I would expect most of the dissent to come from people who, despite being LW-rationalists, are adherents of a religion that says there's some kind of afterlife.)

[EDITED to add: there might also be a substantial fraction dissenting on the grounds that some of the key notions are ill-defined; for instance, that we don't really know what "conscious" means beyond the fact that one particular bunch of things -- namely, us -- seem to have it; or that personal identity is fuzzy and in putative cases of "resurrection" there really isn't a fact of the matter as to whether the "before" and "after" are actually The Same Person.]

It is a simple case of parsimony.

The brain and the physical world in general are sufficient to explain consciousness, so therefore any assumptions beyond that get a complexity penalty.

And...that's the only reason. All your "possibilities" are indeed possible... but improbable. I don't reject the idea that consciousness could theoretically reside outside the brain, but it's much more parsimonious to assume it does not.

I've read a fair amount on Less Wrong

If so, I take it you already understand about parsimony and its importance for hypothesizing, since there has been a good deal of discussion about that. Additionally, as a neuroscience major you have sufficient background to at least agree that consciousness could theoretically be an entirely physical phenomenon. You've got all the background information you need to make the required inferences.

So for my own curiosity, do let me know: Was reading above sufficient to cause you to alter your belief, and do you now know that consciousness probably (more probably than "50/50") is an entirely physical phenomenon which centers around the brain?

Edit: Reading your other comments, you still don't get parsimony.

Hypothesis 1: I have only two left toes.

Hypothesis 2: I have only two left toes and own a bunny rabbit hat.

1 is more parsimonious than 2. It's not 50/50.

Hypothesis 1: The brain is enough to explain the evidence of consciousness

Hypothesis 2: The brain is enough to explain the evidence of consciousness, but there are additional things which are also conscious, only we can't observe them.

1 is more parsimonious than 2. It's not 50/50.

While I do still find myself quite uncertain about the concept of 'quantum immortality', not to mention the even stronger implications of certain multiverse theories, these don't seem to be the kind of thing that you're talking about. I submit that 'there is an extant structure not found within our best current models of reality isomorphic to a very specific (and complex) type of computation on a very specific (and complex) set of data (ie your memories and anything else that comprises your 'identity')' is not a simple proposition.

The OP is terribly confused.

"What happens to our consciousness when we die?"

The question makes no sense. The irreversible disruption of metabolic chemistry that for reasons of convenience we all call death implies also the irreversible destruction of consciousness. Asking what happens to consciousness when we die is like asking what happens to a bird flying formation when they land.

[N]euronal firing [only represents] the preconditions that seem to produce consciousness that can/do communicate/demonstrate its consciousness to us.

Any other factors would be irrelevant. With no self-awareness, there's no consciousness worth speaking of.

In short: Physical destruction of the brain entails destruction of consciousness because your consciousness resides entirely and solely in your brain. If the brain tissue gets too damaged (most commonly from lack of oxygen), it dies, and you with it. There is not, and cannot be, any afterlife.

On your last point, no. To put it colloquially, the simpler answer is more likely.

In practical terms, saying that all binary choices without evidence causes conflicts. Namely, if there's a 50/50 chance that your consciousness dissolves when you die, and a 50/50 chance that a hidden FAI captures your brain state, and a 50/50 chance that a hidden UFAI captures your brain state. That implies that in every case that a FAI captures your brain state so does a UFAI.

People in the comments have just taken it as a given that consciousness resides solely in the brain without explaining why they think this.

And it's a neuroscience major who's asking this. For Skynet's sake, if you of all people can't see why consciousness requires a physical substrate several levels above the subatomic scale, then this whole thread is hopeless.

It may be magical thinking, but magical thinking is awesome!

"Anxiety reliefAccording to theories of anxiety relief and control, people turn to magical beliefs when there exists a sense of uncertainty and potential danger and little to do about it. Magic is used to restore a sense of control. In support of this theory, research indicates that superstitious behavior is invoked more often in high stress situations, especially by people with a greater desire for control.[7] It is proposed that one reason (but not necessarily the only reason) for the persistence of magic rituals is that the ritual activates vigilance-precaution systems – that is to say, that the rituals prompt their own use by creating a feeling of insecurity and then proposing themselves as precautions.[8] Pascal Boyer and Pierre Liénard propose that the shape rituals take results from goal demotion and attentional focus on lower level representation.[9] Levels of representation were previously described by J.M. Zacks and Barbara Tversky.[10] At the lowest level are simple gestures (such as putting the left foot in a shoe). At the mid-level are behavioral episodes (such as putting one’s shoes on). At the highest level are scripts (such as getting dressed to go out). Ordinarily, people describe and recall behavior in terms of the middle level of behavioral episodes. In studies of obsessive-compulsive rituals, focus shifts to the lower level of gestures, resulting in goal demotion. For example, an obsessive-compulsive cleaning ritual may overemphasize the order, direction, and number of wipes used to clean the surface. The goal becomes less important than the actions used to achieve the goal, with the implication that magic rituals can persist without efficacy because the intent is lost within the act. Debate remains as to whether studies of obsessive-compulsive rituals can be extended to describe other kinds of rituals."

The problem with asking a question like that in this forum, is that most people here have been trained not to recognize the referent of the word "consciousness" and thus tend to confuse it with its correlates.