You claimed that the MWI predicts that we should see many worlds. I'm saying it doesn't. The only way to argue for either
of these two positions is to examine what the MWI actually says.
I don't know how you define this "QM without collapse", but if it "doesn't agree with experimental results" then it doesn't make the same predictions as QM, which means that it isn't the MWI. So your objection against the MWI appears to be that QM can be modified to something undefined that makes incorrect predictions. That obviously doesn't qualify as an argument against the MWI.
And I argue that they're not. To prove that conclusively, I'd have to spend a lot more time extracting information from you about your fictional theory of organ symmetry than I'm willing to do, so I'll just point out one obvious difference: The fictional theory doesn't explain why the unobservable organs are unobservable.
It's possible that it was originally intended to be an explanation of why QM is a probabilistic theory (I haven't read Everett), but it certainly isn't
such an explanation. It doesn't solve any problems. It's just the minimal realistic interpretation of QM.
If we reject all
interpretations of the second kind, we can't ever claim that a theory describes reality. We can't even say that "the Earth is spherical" is an approximately correct statement. "The Earth is spherical" would be nothing more than a meaningless string of text that we can use to obtain predictions according to a specific set of rules.
In this particular case, we all feel that it's obvious that the theory not only makes accurate predictions, but also describes
reality. In other words, we all feel that it's obvious that the simplest possible interpretation (of the second kind) is correct
. (Approximately, of course). Most of us also think that it makes sense to say that Newtonian mechanics describes reality. We can think of it as an approximate description of (some aspect of) the universe we live in, or as an exact description of a fictional
universe, but it's certainly a description of something
Things get a bit more weird when we start talking about special and general relativity. There's a theory involving an aether and a preferred reference frame that makes the same predictions as SR. We can think of these as two different but equivalent theories, or as two formulations of the same theory. They make the same predictions, but describe things differently. There's also a version of GR that treats spacetime as flat, and measurement devices as being distorted by influence from matter. This theory makes the same predictions as GR, but describes things differently.
At this point in time, no one expected that we would ever have to settle for less. Everyone just assumed that a good theory had to be an approximate description of reality. They would even define the word "theory" to mean exactly that. People like Bohr, Heisenberg and Schrödinger, certaintly weren't looking for an algorithm that tells us how to calculate probabilities of possibilities. They were looking for a description
of what actually happens at the atomic level.
It must have been quite a shock for the physicists of the time to find a theory that's so weird it doesn't have an obvious interpretation of the second kind. Physicists have always been trying to find the truth
about what things really are like, and without an interpretation of the second kind, one can question whether the theory has improved our understanding of how the world works at all
! Imagine that the theory "the world is spherical" had been stated in the form of some text that you can't even understand, along with instructions about how to use that text to find predictions. This is how QM must have seemed to the physicists at the time.
Note that a theory that assigns non-trivial probabilities (not always 0 or 1) to possible results of experiments doesn't even satisfy the condition of falsifiability
. If the probability of getting a specific result is 99.9999%, you can still get a different result a million times or more. So to bring statistical, non-descriptive theories like QM into the world of science, we even had to drop the requirement of falsifiability from the definition of science, and replace it with a related concept which I think of as "statistical falsifiability". (I think it's obvious what I mean by that, so I won't explain it). Can you imagine changing the definition of science to get a new theory to be considered science? This what dowsers, homeopaths and remote viewers occasionally try to get us to do. (I'm sure that scientists had their share of encounters with those fools back then too).
With all that in mind, it's certainly not surprising that people have been trying to find ways to interpret QM as a description of something. Some people think that it's just a waste of time because experiments can't distinguish between interpretations. "It isn't science". I think this is a bizarre attitude (even though the "it isn't science" bit is technically correct). If we find a bunch of logically consistent interpretations, there's at least a chance
that we have found the correct description of the universe. And even if they're all wrong, they might still improve our understanding
of the theory, and therefore our understanding of the real world. Even an incorrect
description might make it easier to for us to solve problems in QM, by giving us a way to visualize what's actually happening in a fictional universe where experiments have the same results as in ours. There's also the possibility that one of the interpretations will be easier to modify into a new theory than the others, and if that's the case, working on that interpretation has been science all along. It just wasn't possible to see it before the job was done. I don't think many of those people would have that attitude if they understood the things I'm talking about in this post.
There are also people who think that it would be a waste of time to try to interpret QM, because QM can't
be interpreted. This I can understand. I was in that camp myself until I understood the MWI well enough to see that it isn't as crazy as it seems. I still don't think that QM can tell us what actually happens in our universe, but I find it fascinating that it might, and even if I knew
that it doesn't, I would still be interested in finding out if it can describe anything at all (a possible
There are two more things that I find really annoying when I read what other people are saying about interpretations. The first is the belief that QM obviously
can be interpreted. This is just wishful thinking. Mermin displays this belief in the articles I linked to. Penrose does it indirectly in his books by repeatedly claiming that the measurement problem is a huge problem in physics. (It isn't a problem at all for the ensemble interpretation, but it's a problem for some realistic interpretations). The second is the attitude that interpretations don't need proper definitions. It's hard to even find two people who have the same thing in mind when they mention the name of a specific interpretation.