Scott Aaronson's cautious optimism for the MWI

I understand what you are saying, which I think my last post showed quite clearly

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.

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".

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.

Obviously both overlap and non-overlap cannot be true, they are ontologically different

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.

Have you read any of the papers that outline this? Alastair Wilson have written several: http://www.alastairwilson.org/

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.

Surely there's a difference between thinking that experiments that can distinguish MWI and Copenhagen are infeasible for various technological reasons, and thinking that MWI and Copenhagen are empirically indistinguishable. I usually interpret empirical indistinguishability as "no conceivable distinguishing experiment" rather than "no feasible distinguishing experiment".

There are certain observables for which MWI and Copenhagen predict different expectation values, provided decoherence is contained. The problem is, we do not currently have much of an idea of how we could go about making the relevant measurements, mainly because we do not know how to keep systems as large as Wigner (or Schrodinger's cat) informationally isolated for a sufficiently long period of time.

The territory is not in the map, because that is nonsense.

That does not beg the question against instrumentalism and jn favour.of realism, because the territory does not have to exist at all.

Realists and anti realists are arguing about whether the territory exists, not where.

Thus it is easy to forget that it is impossible to verify that "territory exists independently of our models of it"

This is one of those times it really is useful to pull out definitions... and for any reasonable definition of 'territory' and 'map', that's self-evidently true. Our models, even if correct, are underdetermined to the point that they cannot completely explain everything. Therefore, there's something else. That's what we call the 'territory'.

Whether the territory is vastly different from our models or simply more detailed, they do not coincide. And on the word 'independent' - well, the territory contains the map, so there's no short-circuit if the territory has map dependence.

Fair enough. Unfortunately, the interpretive options for QFT are still not clearly worked out. I think the idea among quantum foundations people tends to be that we first figure out the best interpretation in the relatively simpler domain of NRQM, then think about how to adapt this interpretation to meet any new challenges from QFT.

This is no doubt partly due to the fact that the formal structure of NRQM is much better systematized and understood. We basically have a satisfactory axiomatization of NRQM, but attempted axiomatizations of QFT still have many lacunae. So there's definitely a "looking for your keys under the streetlight even though you dropped them in the dark" thing going on here.

By all means! The Relativity complicates this MWI. We have different splits for different observers, since everything is not simultaneous for everyone.

Now what, if the future velocity of an observer is a result of a quantum experiment's outcome. What's very often, if not always!

MWI, the non-relativistic version is NOT real, anyway.