I've seen variants of MWI that were explicitly MWI, so what you're calling MWI would be straight Everettian MWI. But really, here, I'm asking: "Does this theory have multiple worlds in it?" I care significantly less what it's called.
For instance, Consistent Histories looks at things quite differently, but if you ask the critical questions of it, it looks like it has many worlds in it. It primes you to zero in on one of them, but if you're going to stick with the wavefunction being real then the histories you don't observe are going to be equally real, just less relevant. On the other hand if you say it's just a trick for finding the probabilities, well, then it's just a formalized ontological collapse and not MWI. I don't see any middle ground or ground off to the side here (aside from throwing your hands in the air and saying you don't know, which is perfectly legitimate but it isn't an interpretation).
The associations of the hermitian operators corresponding to observable quantities are very type-2. We should feel about as justified using them as using the Born rule.
The point of mentioning objective collapse in the last 2 paragraphs was as a reference point for the non-equality of type-2 postulates. I know it's terrible, and you know it's terrible - that's the point.
But really, here, I'm asking: "Does this theory have multiple worlds in it?" I care significantly less what it's called
Right- in consistent histories there is 1 world. When you make a measurement, you get one answer. In ensemble quantum mechanics there is 1 world. Remember- the creators of consistent histories (Hartle, for instance) consider it a formalized and clarified copenhagen variant (though inspired by many worlds). Maybe think about it like Bohmian mechanics- the "world" that the Bohmian particle actually sits in is the 'r...
There are a great many ideas which don't have enough carefully-measured evidence to be sufficiently confirmed as scientific fact and accepted as such by the scientific community (a recent joke was "While the Higgs Boson has not been discovered yet, its mass is 125 GeV"), but don't have enough carefully-measured evidence to be ruled out yet, either. Do any of the tools of the LW community help narrow down which ones are more worthy of consideration than others?
Eg:
* Cryonics as an arguably reasonable bet for its cost: proto-science
* Cryonics as a surefire way to achieve immortality: nigh-certainly pseudoscience (unless it's the method by which your Everett Immortality keeps you alive)
* Using math to demonstrate that taking classical physics and adding determinism results in MWI-style quantum physics: proto-science.
* Using math to demonstrate that quantum physics proves Christianity is true, from a certain point of view: pseudo-science
* Tubulin might self-organize into microtubules capable of computation on a sub-neuron scale: Possibly proto-science
* Tubulin architecture is 'quantum' in nature and that is what gives rise to consciousness: Probably pseudo-science
* 'Quantum consciousness' means anything is possible: Downright silly
* The E8 Lie group can provide a system for organizing the properties of subatomic particles: Proto-science, perhaps
* Heim theory is useful for predicting particle masses: Pseudo-science, probabilistically
* Using the Bullet Cluster to claim that dark matter is a better theory than Modified Newtonian Dynamics: proto-science
* Claiming that dark matter is made of 'anapoles': Proto-science, perchance
* Suggesting that dark matter is actually gravitational leakage from MWI 'parallel universes': You tell me. (But if it's true, then since I can't seem to find any previous serious discussion of this idea, I get to name part of it after myself, right? :) )
These may not be the best examples, but they're the closest ones I can think of to the boundary. If you know of any better ones, feel free to comment with them.