MWI, copies and probability

Your whole "paradoxical" setup works just as well if the randomizing device in the grenade is classical rather than quantum. But in the classical case our feelings are just the same, though no copies exist! The moral of the story is, I certainly do care about probability-branches of myself (the probabilities could be classical or quantum, no difference), but you haven't yet persuaded me to care about arbitrary copies of myself elsewhere in the universe that aren't connected to my "main tree", so to speak.

Another way to think about this is that many of us seem to share the follow three intuitions about non-interacting extra copies, out of which we have to give up at least one to retain logical consistency:

1. We value extra copies in other quantum branches.
2. We don't value extra copies that are just spatially separated from us (and are not too far away).
3. We ought to value both kinds of copies the same way.

_

• Giving up 1 is the position of "quantum immortality".
• Giving up 2 seems to be Roko's position in this post.
• Giving up 3 would imply that our values are rather arbitrary: there seems to be no morally relevant differences between these two kinds of copies, so why should we value one and not the other? But according to the "complexity of value" position, perhaps this isn't really a big problem.

Another possibility is to hold a probabilistic superposition of these three positions, depending on the relative strengths of the relevant intuitions in your mind.

I'll bite this bullet. If the grenade is always reliable, and if MWI is true for certain, and if it's not just a mathematical formalism and the other worlds actually exist, and if I don't have any relatives or other people who'd care of me, and if my existing in this world doesn't produce any net good for the other residents of this world, and if I won't end up mangled... then I would accept the deal of having this grenade thrown at me in exchange for 100 dollars. Likewise, I would deem it legal to offer this trade for other people, if it could be ascertained, without any chance of corruption, coercion or abuse, that these same criteria also applied to all the people the trade was being offered to.

But for that purpose, you have to assume pretty much all of those conditions. Since we can't actually do that in real life, this isn't really as paradoxical a dilemma as you imply it to be. In order to make it a paradox, you'd have to tack on so many assumptions that it ceases to have nearly anything to do with the world we live in anymore.

It reminds me of the argument that utilitarianism is wrong, because utilitarianism says that doctors should kill healthy patients to get life-saving organ transplants for several other people. Yes, if you could institute this as a general policy with no chance of anyone ever finding out about that, and you could always kill the chosen people without them having a chance to escape, and a dozen other caveats, then this might be worth it... but in pretty much any conceivable real-life situation, even trying to institute such a policy would obviously just do more harm than good, so it isn't really an argument against utilitarianism. Likewise, your proposed scenario isn't really an argument against not valuing identical copies.

I don't think MWI is analogous to creating extra simultaneous copies. In MWI one maximizes the fraction of future selves experiencing good outcomes. I don't care about parallel selves, only future selves. As you say, looking back at my self-tree I see a single path, and looking forward I have expectations about future copies, but looking sideways just sounds like daydreaming, and I don't have place a high marginal value on that.

The punch line is that the physics we run on gives us a very strong reason to care about the welfare of copies of ourselves, which is (according to my survey) a counter-intuitive result.

No, it doesn't. Maximising your Everett blob is a different thing than maximising copies. They aren't the same thing. It is perfectly consistent to care about having yourself existing in as much Everett stuff as possible but be completely indifferent to how many clones you have in any given branch.

Reading down to Wei's comment and using that break down, premise 3) just seems totally bizarre to me:

1. We ought to value both kinds of copies the same way.

Huh? What? Why? The only reason to intuitively consider that those must have the same value is to have intuitions that really don't get quantum mechanics.

I happen to like the idea of having clones. I would pay to have clones across the cosmic horizon. But this is in a whole different league of preference to not having me obliterated from half the quantum tree. So if I was Sly my response would be to lock you in a room and throw your 50% death grenade in with you. Then the Sly from the relevant branch would throw in a frag grenade to finish off the job. You just 50% murdered him.

It occurs to me that my intuitions for such situations are essentially updateless. Wedrifid-Sly cares about the state of the multiverse, not that of the subset of the Everett tree that happens to flow through him at that precise moment in time (timeless too). It is actually extremely difficult for me to imagine thinking in such a way that quantum-murder isn't just mostly murderring me, even after the event.

MWI copies and possible world copies are not problematic, because both situations naturally admit an interpretation in terms of "the future me" concept ("splitting subjective experience"), and so the moral intuitions anchored to this concept work fine.

It is with within-world copies, or even worse near-copies, that the intuition breaks down: then there are multiple "future me", but no "the future me". Analysis of such situations can't rely on those moral intuitions, but nihilistic position would also be incorrect: we are just not equipped to evaluate them.

(See also these comments.)

I think the point is that not valuing non-interacting copies of oneself might be inconsistent. I suspect it's true; that consistency requires valuing parallel copies of ourselves just as we value future variants of ourselves and so preserve our lives. Our future selves also can't "interact" with our current self.

I think the situation with regard to MWI 'copies' is different from that with regard to multiple copies existing in the same Everett branch, or in a classical universe.

I can't fully explain why, but I think that when, through decoherence, the universe splits into two or more 'worlds', each of which are assigned probability weights that (as nearly as makes no difference) behave like classical probabilities, it's rational to act as though the Copenhagen interpretation was (as nearly as makes no difference) true. Strictly speaking the Copenhagen interpretation is incoherent, but still you should act as though, in a "quantum suicide" scenario, there is probability p that you will 'cease to exist', rather than a probability 1 that a copy of you will go on existing but 'tagged' with the information 'norm square amplitude of this copy is [1-p times that of the pre-existing person]'.

My rationale is roughly as follows: Suppose the universe were governed by laws of physics that were 'indeterministic' in the sense of describing the evolution over time of a classical probability distribution. Then if we want to, we can still pretend that there is a multiverse, that physics is deterministic, that all possible worlds exist with a certain probability density etc. And clearly the difference between a 'single universe' and a 'multiverse' view is 'metaphysical' in the sense that no experiment can tell them apart. Here I want to be a verificationist and say that there is no 'fact of the matter' as to which interpretation is true. Therefore, the question of how to act rationally shouldn't depend on this.

When we move from classical indeterminism to quantum indeterminism the probabilities get replaced by complex-valued 'amplitudes' but for reasons I struggle to articulate, I think the fact that the universe is 'nearly' classical means that our prescriptions for rational action must be 'nearly' the same as they would have been in a classical universe.

As for sly, he should act as though he has luckily survived an event that had a 1/2 chance of killing him ('once and for all', 'irrevocably' etc). Presumably he would charge you with something, though I'm not sure whether 'attempted murder' is what you'd be guilty of.

Attempted murder, I reckon!

We can't have people going around throwing grenades at each other - even if they "only" have a 50-50 chance of exploding. This dangerous idiot is clearly in need of treatment and / or serving as a lesson to others.

(B) if he thanks you for the free $100, does he ask for another one of those nice free hundred dollar note dispensers? (This is the "quantum suicide" option

I laugh in the face of anyone who attests to this and doesn't commit armed robbery on a regular basis. If 'at least one of my branches will survive' is your argument, why not go skydiving without a parachute? You'll survive - by definition!

So many of these comments betray people still unable to think of subjective experience as anything other than a ghostly presence sitting outside the quantum world. 'Well if this happens in the world, what would I experience?' If you shoot yourself in the head, you will experience having your brains blown out. The fact that contemplating oneself's annihilation is very difficult is not an excuse for muddling up physics.

All these comments and no one questions MWI? Is there another thread for that?

What does MWI explain that can't be explained without it? Name even a gedanken experiment that gives a different result in an MWI universe than it does in a universe with either 1) randomly determined but truly collapsed uniquely quantum collapses 2) quantum collapses determined uniquely by a force or method we do not yet know about.

Having said all that, Sly has plenty of reason to dislike me, even to want me arrested for attempted murder even without MWI. A world in which Sly is arrested and stopped of his odd gambling with other people's lives habit, I and other people I value have a higher probabiliy of surviving in my subjective timeline. I know that people who do something tend to do that in the future with much higher probability than do people who don't do that. This inference has been bred in to me because it was true enough to aid the survival, especially in our socially competitve groups, of my ancestors, so it makes good sense to go with this idea.

I would place 0 value on creating identical non-interacting copies of myself. However, I would place a negative value on creating copies of my loved ones who were suffering because I got blown up by a grenade. If Sly is using the same reasoning, I think he should charge me with attempted murder.

(A) Sly charges me with attempted murder. Sly does not think that his counterpart in the other Everett branch is not interacting with him -- actually, Sly, after reading LW a lot, thinks that he has a "causal" responsibility, going-back-in-time, on whether his counterpart lives in the other branch, and therefore on how well the other branch fares. (If we transform this grenade into a counterfactual mugging grenade that has an option to not be "probably lethal" conditional on Sly's refusing of $100, Sly has causal effect on whether he lives in the other branch. With a lethal-only quantum grenade, Sly is left with responsibility to consistently ban uses of the grenade, so he should refuse $100 and put charges anyway -- producing of such grenades is "sick".)

D) He will thank you, and charge you for attempted murder to minimize risk of being mangled by non-100%-kill grenade.

BTW, I've some thoughts on anthropic trilemma, maybe they'll be of use.

This looks unfinished? At any rate I'm not getting the point.

I reject "3" (We ought to value both kinds of copies the same way), but don't think that it is arbitrary at all. Rather it is based off of an important aspect of our moral values called "Separability." Separability is, in my view, an extremely important moral intuition, but it is one that is not frequently discussed or thought about because we encounter situations where it applies very infrequently. Many Less Wrongers, however, have expressed the intuition of separability when stating that they don't think that non-causally connected parallel universe should affect their behavior.

Separability basically says that how connected someone is to certain events matters morally in certain ways. There is some debate as to whether this principle is a basic moral intuition, or whether it can be derived from other intuitions, I am firmly in favor of the former.

That probably sounds rather abstract, so let me give a concrete example: Imagine that the government is considering taking an action that will destroy a unique ecosystem. There are millions of environmentalists who oppose this action, protest against it, and lobby to stop it. Should their preference for the ecosystem to not be destroyed be taken into consideration when calculating the utility of this situation? Have they, in a sense, been harmed if the ecosystem is destroyed? I'd say yes, and I think a lot of people would agree with me.

Now imagine that in a distant galaxy there exist approximately 90 quadrillion alien brain emulators living in a Matrioshka Brain. All these aliens are fervent environmentalists and have a strong preference that no unique ecosystem ever be destroyed. Assume we will never meet these aliens. Should their preference for the ecosystem to not be destroyed be taken into consideration when calculating the utility of this situation? Have they, in a sense, been harmed if the ecosystem is destroyed? I'd say no, even if Omega told me they existed.

What makes these two situations different? I would say that in the first situation the environmentalists possess strong causal connections to the ecosystem in question, while the aliens do not. For this reason the environmentalists' preferences were morally relevant, the aliens' not so.

Separability is really essential for utilitarianism to avoid paralysis. After all, if everyone's desires count equally when evaluating the morality of situations, regardless of how connected they are to them, then there is no way of knowing if you are doing right or not. Somewhere in the universe there is doubtless a vast amount of people who would prefer you not do whatever it is you are doing.

So how does this apply to the question of creating copies in my own universe, versus desiring a copy of me in another universe not be destroyed by a quantum grenade?

Well, in the issue of whether or not to create identical copies in my own universe, I would not spend a cent trying to do that. I believe in everything Eliezer wrote in In Praise of Boredom and place great value on having new, unique experiences. Creating lockstep copies of me would be counterproductive, to say the least.

However, at first this approach seems to run into trouble in MWI. If there are so many parallel universes it stands to reason that I'll be duplicating an experience some other me has already had no matter what I do. Fortunately, the Principle of Separability allows me to rescue my values. Since all those other worlds lack any causal connection to me, they are not relevant in determining whether I am living up to the Value of Boredom.

This allows us to explain why I am upset when the grenade is thrown at me. The copy that was killed had no causal connection to me. Nothing I or anyone else did resulted in his creation, and I cannot really interact with him. So when I assess the badness of his death, I do not include my desire to have unique, nonduplicated experiences in my assessment. All that matters is that he was killed.

So rejecting (3) does not make our values arbitrary, not in the slightest. There is an extremely important moral principle behind doing so, a moral principle that is essential to our system of ethics. Namely, the Principle of Separability.

If you think carefully about Descartes' "I think therefore I am" type skepticism, and approach your stream of sensory observations from such a skeptical point of view, you should note that if you really were just one branch-line in a person-tree, it would feel exactly the same as if you were a unique person-line through time, because looking backwards, a tree looks like a line, and your memory can only look backwards.

I like this way of explaining how MWI all adds up to normality, and I'll use it in future discussions.

What if I simply don't trust the many worlds interpretation that much?

I think that I can be consistent with charging you with attempted murder.

In your scenario, if the grenade is not in my favor; this particular instance of me will be dead. The fact that a bunch of copies collect $100 is of little value to the copy that my subjective experience occupied.

For instance, if Omega came up to me right now and said that he just slew some copies of me in other lines, than it is unclear how that event has affected me. Likewise if I die, and Omega tells my other copies, it seems like it is only this subjective branch that suffers.

So because the grenade can affect the current branch that I experience, I can object.

I think anyway, I may have misunderstood everything.

Also: I was very surprised to be the subject of a post. It has been interesting. =)

EDIT: Wouldn't the grenade thought experiment be more accurate if the grenade only killed or gave out $100 to copies when thrown at me? The fact that it interacts with me and not just copies of me is where I get a disconnect.

BTW. I don't understand, why it is taken for granted that Sly's thread of subjective experience in branch where grenade exploded will merge with thread of subjective experience in other branch.

Question of assigning probabilities to subjective anticipations is still open. Thus, it's possible that after grenade explosion Sly will experience being infinite chain of dying Boltzmann brains, and not a happy owner of $100.

EDIT: Using Solomonoff prior, I think he will wake up in a hospital, as it is one of simplest continuations of his prior experiences.