Showing that MWI is correct while other interpretations are not is straight-up Nobel material.
I don’t think “MWI” is a useful abbreviation (unless you unpack it as “many world interpretations” it implies it’s singular, for example), and I’m not sure “correct” is the right word either. My understanding of Eliezer’s argument is like so:
Interpretations of QM differ in how many postulates they have, and how difficult those postulates are to justify, but typically not in verifiable experimental predictions. (An interpretation that gets experimental predictions wrong should be dropped out of the running.)
One should have higher credence in simpler interpretations—that is, ones with fewer and less strange postulates.
The first major interpretation of QM adopted by mainstream science had additional costly postulates relative to later interpretations or the agnostic interpretation. That it is still taken seriously is evidence for the strength of first mover effects / the inadequacy of scientific philosophy in getting answers correct quickly.
We know from superposition that many quantum phenomena are better described by “branch both ways” than “branch one way xor the other,” and supposing that the other branch is deleted rather than inaccessible requires an extra postulate, which should lower our credence in interpretations that have only one surviving world.
I don’t think this argument implies that there is a unique surviving interpretation—but it will never be the case that there is a unique surviving interpretation, because I can take that interpretation and add an unobservable feature to it, creating a new interpretation. The principle by which those interpretations are reduced in prominence, when applied straightforwardly to QM, suggests that it’s more likely that other branches of the wavefunction that we are not on continue to exist rather than disappearing because we are not there.
(Personally, I still identify with “shut up and calculate,” where one refuses to answer statements about whether or not the other branches are real. But if one must conclude something, it’s less jarring to conclude they are real than unreal.)
That all sounds very reasonable—though I’m not as big a fan of William of Ockham as many people here—but I still don’t understand what did Eliezer mean by “knowable”.
In the absence of a straightforward empirical interpretation (“knowable” = pokable, measurable, analysable...), I associate this word with mushy theology (along the “Christ is knowable through your heart” lines).
I still don’t understand what did Eliezer mean by “knowable”.
It’s one thing to say “there are multiple competing interpretations,” another to say “there is a simplest interpretation, and other, more burdensome variants,” and still another to be able to point to the calculations that determine which explanation is simplest. I don’t poll people on their interpretations of QM, but I am of the impression that many people who have opinions on QM interpretations aren’t even aware that there’s math that is useful for comparing interpretations. (Hence them not realizing that it’s “knowable.”)
There’s also the point about lightness, and using the most likely explanation as the default explanation, instead of saying “sure, it’s more likely, but not so much more likely enough that my pet theory is totally unacceptable in comparison, so I’m sticking with my pet theory.”
aren’t even aware that there’s math that is useful for comparing interpretations
Notably, that “math” (and it’s not just math) did not convince large chunks of the physics community—people who are quite comfortable with numbers and who certainly know the “knowable” issue.
But this is an endless debate and it probably would be best not to step into the morass :-)
I don’t think “MWI” is a useful abbreviation (unless you unpack it as “many world interpretations” it implies it’s singular, for example), and I’m not sure “correct” is the right word either. My understanding of Eliezer’s argument is like so:
Interpretations of QM differ in how many postulates they have, and how difficult those postulates are to justify, but typically not in verifiable experimental predictions. (An interpretation that gets experimental predictions wrong should be dropped out of the running.)
One should have higher credence in simpler interpretations—that is, ones with fewer and less strange postulates.
The first major interpretation of QM adopted by mainstream science had additional costly postulates relative to later interpretations or the agnostic interpretation. That it is still taken seriously is evidence for the strength of first mover effects / the inadequacy of scientific philosophy in getting answers correct quickly.
We know from superposition that many quantum phenomena are better described by “branch both ways” than “branch one way xor the other,” and supposing that the other branch is deleted rather than inaccessible requires an extra postulate, which should lower our credence in interpretations that have only one surviving world.
I don’t think this argument implies that there is a unique surviving interpretation—but it will never be the case that there is a unique surviving interpretation, because I can take that interpretation and add an unobservable feature to it, creating a new interpretation. The principle by which those interpretations are reduced in prominence, when applied straightforwardly to QM, suggests that it’s more likely that other branches of the wavefunction that we are not on continue to exist rather than disappearing because we are not there.
(Personally, I still identify with “shut up and calculate,” where one refuses to answer statements about whether or not the other branches are real. But if one must conclude something, it’s less jarring to conclude they are real than unreal.)
That all sounds very reasonable—though I’m not as big a fan of William of Ockham as many people here—but I still don’t understand what did Eliezer mean by “knowable”.
In the absence of a straightforward empirical interpretation (“knowable” = pokable, measurable, analysable...), I associate this word with mushy theology (along the “Christ is knowable through your heart” lines).
It’s one thing to say “there are multiple competing interpretations,” another to say “there is a simplest interpretation, and other, more burdensome variants,” and still another to be able to point to the calculations that determine which explanation is simplest. I don’t poll people on their interpretations of QM, but I am of the impression that many people who have opinions on QM interpretations aren’t even aware that there’s math that is useful for comparing interpretations. (Hence them not realizing that it’s “knowable.”)
There’s also the point about lightness, and using the most likely explanation as the default explanation, instead of saying “sure, it’s more likely, but not so much more likely enough that my pet theory is totally unacceptable in comparison, so I’m sticking with my pet theory.”
Notably, that “math” (and it’s not just math) did not convince large chunks of the physics community—people who are quite comfortable with numbers and who certainly know the “knowable” issue.
But this is an endless debate and it probably would be best not to step into the morass :-)