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Quantumental comments on Scott Aaronson's cautious optimism for the MWI - Less Wrong
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So, by "world" in this post I'll mean "basis sate for the universe." The basis is arbitrary, so what "world" means will still depend on how I'm choosing what "worlds" are - there's the energy basis, for instance, where nothing ever changes if you look at just one of those "worlds." But you can have animals or computers in your basis states if you want - they aren't energy eigenstates, so they change with time.
Anyhow, currently the universe is spread out over a very wide variety of energy eigenstates, which is a fancy way of saying that lots of stuff changes. If we only allow quantum mechanics (that is, strictly follow MWI), this spread over "energy-worlds" is how the universe has been since the beginning of time. But if we look at the exact same state a different way, you could just call the initial state of the universe a basis state, and then, lo and behold, the universe would have sprung from one world, and the distribution of worlds then changed over time. This way of looking at things is probably pretty useful for cosmology. Or you could use worlds that change over time but don't include the original state of the universe, giving you overlap again. This is what we do unintentionally when we choose worlds that have humans in them, which is also pretty useful :)
For overlap vs. non-overlap to get more complicated than "both are valid pictures," you'd need some model where there weren't any static worlds to talk about - this would be a change to QM though. Also, this does raise the interesting question of how complicated that initial world (if we look at it that way) was. It doesn't have to be too complicated before we see interesting stuff.
Anyhow, it's pretty likely I was too hasty in my mistake-detection. But meh, I rarely regret putting off reading things. And I only occasionally regret putting my foot in my mouth :)
To be perfectly honest, I do not see an answer to my question here.
You do explain some, but it seems that you end up indirectly stating that it is "semantics" whether the worlds overlap or not overlap. From what you say here it all depends on how you look at it, but that there is no "truth" of the matter. But that cannot be, either the worlds are overlapping or they are not. That is just the very fact of objective reality.
So while "both pictures are valid" in terms of math, not both can be the same. Metaphysically they are not the same and they got very different effects on episteomology. Also in terms of for instance quantum suicide. In overlap, it's hard to argue against some sort of Quantum Immortality, whilst in non-overlap death is just as in a classical one world theory.
What I am saying is that if one person says "all the worlds have always existed" and another says "the worlds spread out from one world," it's possible that both of them are being consistent, but then they are using two different definitions of "world." I am also saying that there is no basis that is "more real" than the others - only that some are more useful, and it's okay that people use different definitions as long as they're clear about it.
And yes, both pictures can describe the same thing. Have you worked with Bell states at all? Or am I misinterpreting your name and you actually haven't taken a class on quantum mechanics before?
The quantum world is like a diagonal line. One person comes up to it and says "Ah! Here is a diagonal line! It has just as much horizontal as it does vertical, therefore it is a mixture between horizontal and vertical." Another person comes up to it and says "Ah! Here is a diagonal line! It is a perfect rising diagonal, and is not even a little biased towards the falling diagonal." Will these two people argue over whether the line is made of two components or one?
I understand what you are saying, which I think my last post showed quite clearly, but this still does not answer the actual question at hand. What you are saying really amounts to saying that "realism and solipsism are the same", because we cannot really distinguish either through science, all we can do is use logic and metaphysical "reasoning".
Obviously both overlap and non-overlap cannot be true, they are ontologically different, yet you seem to say that "because the equations doesn't decide, reality isn't decided" which is some sort of extreme positivism.
Have you read any of the papers that outline this? Alastair Wilson have written several: http://www.alastairwilson.org/
Maybe you're just used to talking with people who are better at interpreting you, or people who are more similar to you. Clearly understandable to people you talk with every day isn't always clearly understandable to me, as we've seen.
Could you explain this? Is this a metaphor, or are have you interpreted my statements about vectors to actually bear on realism vs. solipsism? Perhaps we have been talking about two different things.
Ah. See, this is the sort of thing I was trying to illustrate with the example of the diagonal line. A line being made of one component is ontologically different from a line being made of two components. Does this matter?
What happens if a one-componenter runs into a two-componenter? Do they argue? Does the first say "because of [insert convincing component-ist argument here], it's ONE component!" Are there valid component-ist arguments? How can the two-componenter respond?
I think it would go more like this: the first one says "hey, if you describe lines in terms of plus and minus diagonals, this one is clearly just a plus diagonal, so why say it has two components?" And the second says "Oh, huh, you're right. But there are lots of horizontal and vertical lines out there, so two-components is more useful." And the first says "yeah, that makes sense, unless you were building a ramp or something." "Well then, cheerio." "Toodles."
The reason this was so anticlimactic is because each participant could frame their ontology in a universal language (vectors!), and the ontologies were lossless transformations of each other - in this case the transformation was as simple as tilting your head. This clarity of the situation leaves no room for appeals to componentism. Arguments are for when both people are uncertain. When people know what's going on, there's simply a difference.
Could you point me to an example? Similar to how we are potentially talking about two different things, Alastair Wilson seemed to be talking about something other than physics in the papers I skimmed. The phrase "the most appropriate metaphysics to underwrite the semantics renders Everettian quantum mechanics a theory of non-overlapping worlds" exemplifies this for me.
Sure I can accept that I might have overestimated how well you should've been able to interpret my post.
Solipsism vs Realism is indeed a metaphor. If you are saying what I think you are saying, then it is quite equivalent.
I do not think that your example of a diagonal line is the same as overlap vs non-overlap at all. In overlap vs non-overlap the ontological differences matter. In a overlapping world, if you are shot, you are guaranteed to survive in another branch, so QI has to be true. In non-overlap, if you get shot, you just die. There is no consciousness that continue on in another branch that it was never connected to...
Also it makes away with the incoherence problem, which is HUGE if you are in the "Born Rule can be derived from decision-theoretic camp".
It is metaphysics, I've already said this in the first post. There is no experiment that can ever distinguish either, just like no experiment can ever tell us if solipsism or realism is true. But obviously (assuming MWI is right) one of them are, only one, not both.
I think 5 of those papers are directly about non-overlap vs overlap, and I can't remember which makes the point best right now, so read any of them you'd like. Or you can read Simon Saunders paper which was in a chapter of the Many Worlds? 2010 book here: http://users.ox.ac.uk/~lina0174/chance.pdf
Ah, I see. "Metaphysics."
By which you mean "taking human morality and decision-making, which evolved in a classical world, and figuring out what decisions you should make in a quantum universe."
Would you agree that overlap vs. non-overlap cannot be answered without looking inside humans, and in fact has little to do with the universe apart from a few postulates of quantum mechanics? For some reason I thought we were talking about the universe.
Anyhow, I think Shane Legg had a nice paper on porting utility functions, though of course humans are inconsistent and you immediately run into problems of how to idealize them. The basic idea being that you split up changes into "new things to care about" and "new ways to express old things." Quantum suicide is probably the easiest thing to deal with via this method.
You have a theory - "quantum mechanics without wavefunction collapse" - in which the whole of reality is supposed to be equal to a single big object, the wavefunction of the universe. There are various mathematical facts about that object: the existence of various sets of basis functions, the dynamical process of decoherence, and so on.
Now a questioner says, "OK. You say that there are multiple copies of me inside the wavefunction. Is that because there is one of me that splits into many, or were there just parallel mes living separate but similar lives?" You've implied that the answer depends on the definition of something. Can you tell the questioner what definition of self leads to the different answers? So far you've used the example "| / > = | | > + | _ >", which doesn't tell anyone whether they should think of themselves as "/", as "|" and " _ ", or otherwise answer the question. It illustrates a mathematical fact about wavefunctions, not a fact about how to find yourself in them.
I do? Well, I can pretend I do, at least.
If we want to recover classical choices in cases where there are clear classical analogs, one of you splits into one. If you'd rather follow other intuitions, though, you'll get different answers (see: quantum suicide).
Note that since humans aren't energy eigenstates, there is no general way to get completely "parallel lives" - you always interfere. But because the world is nice and orderly you can get pretty dang close to parallel most of the time.
Well, it answers the person who asks "But is the line really one component, or is it really two components?" And that answer is that they've gotten their levels confused - number of components is in your description of the line, not in the line.
Which, to make sure I'm being clear, is analogous to how I interpreted Quantumental's sentence "Obviously both overlap and non-overlap cannot be true, they are ontologically different." If we go with a correspondence theory of truth, we run into a problem because there is no overlap or non-overlap out in quantum mechanics that this sentence could correspond to. Instead, the thing that would make it true or false is humans; specifically how they choose what's right when presented with quantum mechanics. Unfortunately, humans are inconsistent, so you immediately run into the problem of how to idealize them.
I get it now. You're saying that the relativism of how one may define one's personal identity is so great that, in a quantum multiverse, even whether you are splitting into multiple selves or not is a matter of how you define yourself.
Still, that's not the end of it, because then we can ask exactly what parts of the wavefunction are "potential person-parts". I may have some freedom to choose whether a particular object, trait, thought, or state of mind that once existed or that could exist is "part of me", but at some level there has to be an objective correspondence between "person-parts" and "wavefunction-parts".
You may be a self-defining process, but the point of materialism is that this self-defining process is not something separate from the wavefunction which then freely chooses which parts of the wavefunction are going to count as "part of me"; the self-defining process is a part of the wavefunction, and the choosing about what to identify with, is just part of wavefunction dynamics. Eventually you have to ground the whole thing in physics rather than in cognition. Any thoughts on how that works?
So you see no objective facts about mwi? non-overlap vs overlap is nonsense in your opinion?
Yes, there are objective facts. Whether a waveunction is made of 2 components or 1 is still not independent of your perspective. No, it's not necessarily nonsense. I am just claiming that the unsolved problems of stuff like "overlap" are not due to a lack of information about quantum mechanics, but due to a lack of information about very complicated things humans do. If it the difficulty of understanding how humans categorize things and revise categories gets attributed to basic quantum mechanics, then we may get some nonsense.
You say there are objective facts, yet you claim it depends on ones perspective...this is contradictory. Have you read any of Wilson's papers? Or Saunders, Lawhead, Ismael etc.? All have written papers clearly indicating the OBJECTIVE difference.