"it appeals to the (undermined) intuition of a single world. Then it may take an extra argument - say, that collapse violates Special Relativity"
So my intuition that there should be only one universe is useless, but your intuition that everything needs to be local (even though there are no time paradoxes involved in collapse like there would be if usable information could go back in time) is supposed to be a compelling argument?
These recent posts have been showing more rationalization than rationality.
Z. M. Davis: All this talk of "simpler computer program" seems pretty meaningless to me. A regex matcher in C is long and complex, but in PHP all you have to do is use the built-in preg_match function. (Does the language the universe was written in have a built-in copenhagen_interpretation function?)
One might claim that PHP is a more complicated language than C, but how is that measured? The only way to see how complicated a language is is by a complete description of it - an implementation. And the complexity of an implementation depends on the kind of CPU it must run on, and the complexity of a CPU architecture depends on the laws of physics it must exist in. Self reference: this is the stuff paradoxes are made of.
So the Bohm interpretation takes the same amplitude distribution as many-worlds and builds something on top of that. So what? That amplitude distribution is just a mathematical object, but it having a physical existence certainly doesn't change the truth or falsehood of any mathematical statements, so I could just as easily say that the amplitude distribution itself is an "epiphenomenon" (and therefore can't exist).
Websites are made of files, as we all know. But those mysterians out there are claiming that there exist websites that they call "blogs", where new content magically appears by virtue of some entity existing outside the World Wide Web, which is an utterly ridiculous concept when given a moment's thought; how could something existing outside the Web possibly affect it?
The word, "fish", is not the real issue. What actually matters is that including dolphins in that category leads to making incorrect inferential predictions ("Salmon, guppies, sharks, and trout all lay eggs, so dolphins probably do too.") as well as weakening the ability to make correct ones ("Do trout have gills? Well, salmon do, but dolphins don't, so who knows.")
What kinds of properties is your "aquatic animals" category better at predicting? (And "living in water" doesn't count, because that's what you have to already know to see if something's in the category.)
That's not really free though, because you're forced to make all possible choices. I guess there are ways that free will could be shoehorned onto the many-worlds model, but both make it even less attractive than it already is. One would be to say that the free-will-thingy only goes in one path rather than splitting. This would have nasty implications; since with an astronomically high probability every free-will-bearing person would be the only one in that universe, so it would be moral to be a psychopath. Another way would be that free will works by eliminating branches, but then it's no longer all possible universes, and if you're going that way why not go all the way and have just one anyway? So as far as I'm concerned, many-worlds -> no free will. Just one of the reasons I don't like it.
The main problem I have with it though is it posits a huge amount of unobservable information. That's way too high a price to pay just to get rid of wavefunction collapse. I really don't buy the argument that the monstrous Everett multiverse is somehow simpler than the nice compact Copenhagen universe.
Free will (I mean real free will. "compatabilist" free will is meaningless.) might or might not exist. I think it does but there's not yet any conclusive evidence either way.
Actually the universe is probably nondeterministic even if free will doesn't exist, just because of quantum mechanics. A hidden variable theory is a possibility but unless one is ever actually proposed I'll have to presume that yes, there really is random stuff. "Many worlds" is just ridiculous, and besides, even though it's deterministic in theory, so what? It doesn't help us make predictions in real life.
Gee, how could anybody ever assume hostility from an innocent statement like that. "Please don't take this the wrong way, but you're completely worthless and we'd all be better off if you just died. No offense intended."