But what if you can’t make a good decision theory that works the same with or without MWI?
This contradicts the premise that MWI is untestable experimentally, and is only a Bayesian necessity, the point of view Eliezer seems to hold. Indeed, if an MWI-based DT suggests a different course of action than a single-world one, then you can test the accuracy of each and find out whether MWI is a good model of this world. If furthermore one can show that no single-world DT is as accurate as a many-world one, I will be convinced.
The fact that the universe apparently exists, and is apparently consistent with MWI, seems to indicate that an MWI universe is at least possible.
It is also consistent with Christianity and invisible pink unicorns, why do you prefer to be MWI-mugged rather than Christ-mugged or unicorn-mugged?
This contradicts the premise that MWI is untestable experimentally
No it doesn’t. DT is about what you should do, especially when we’re invoking Omega and Matrix Lords and the like. Which DT is better is not empirically testable.
It is also consistent with Christianity and invisible pink unicorns
Yes, except that MWI is the best theory currently available to explain mountains of experimental evidence, while Christianity is empirically disproven (“Look, wine, not blood!”) and invisible pink unicorns (and invisible, pink versions of Christianity) are incoherent and unfalsifiable.
(Later edit: “best theory currently available to explain mountains of experimental evidence” describes QM in general, not MWI. I have a hard time imagining a version of QM that doesn’t include some form of MWI, though, as shminux points out downthread, the details are far from being settled. Certainly I don’t think that there’s a lot to be gained by comparing MWI to invisible pink unicorns. Both have a p value that is neither 0 nor 1, but the similarity pretty much ends there.)
Re MWI: My understanding of QM is quite good for someone who has never done the actual math. I realize that there are others whose understanding is vastly better. However, this debate is not about the equations of QM per se, but about the measure theory that tells you how “real” the different parts of them are. That is also an area where I’m no more than an advanced amateur, but it is also an area in which nobody in this discussion has the hallmarks of an expert. Which is why we’re using terms like “reality fluid”.
My understanding of QM is quite good for someone who has never done the actual math
And my violin skills are quite good for someone who has never done the actual playing.
However, this debate is not about the equations of QM per se, but about the measure theory that tells you how “real” the different parts of them are.
Different parts of what? Of equations? They are all equally real: together they form mathematical models necessary to describe observed data.
Which is why we’re using terms like “reality fluid”.
Eliezer is probably the only one who uses that and the full term is “magical reality fluid” or something similar, named this way specifically to remind him that he is confused about it.
I have a related degree, if that’s what you are asking.
ψ
I’m yet to see anyone writing down anything more than a handwaving of this in MWI. Zurek’s ideas of einselection and envariance go some ways toward showing why only the eigenstates survive when decoherence happens, and there is some experimental support for this, though the issue is far from settled.
Precisely; the issue is far from settled. That clearly doesn’t mean “any handwavy speculation is as good as any other” but it also doesn’t mean “speculation can be dismissed out of hand because we already understand this and you’re just wrong”.
(Moved my reply, too)
This contradicts the premise that MWI is untestable experimentally, and is only a Bayesian necessity, the point of view Eliezer seems to hold. Indeed, if an MWI-based DT suggests a different course of action than a single-world one, then you can test the accuracy of each and find out whether MWI is a good model of this world. If furthermore one can show that no single-world DT is as accurate as a many-world one, I will be convinced.
It is also consistent with Christianity and invisible pink unicorns, why do you prefer to be MWI-mugged rather than Christ-mugged or unicorn-mugged?
No it doesn’t. DT is about what you should do, especially when we’re invoking Omega and Matrix Lords and the like. Which DT is better is not empirically testable.
Yes, except that MWI is the best theory currently available to explain mountains of experimental evidence, while Christianity is empirically disproven (“Look, wine, not blood!”) and invisible pink unicorns (and invisible, pink versions of Christianity) are incoherent and unfalsifiable.
(Later edit: “best theory currently available to explain mountains of experimental evidence” describes QM in general, not MWI. I have a hard time imagining a version of QM that doesn’t include some form of MWI, though, as shminux points out downthread, the details are far from being settled. Certainly I don’t think that there’s a lot to be gained by comparing MWI to invisible pink unicorns. Both have a p value that is neither 0 nor 1, but the similarity pretty much ends there.)
You ought to notice your confusion by now.
What is your level of understanding QM? Consider reading this post.
Re DT: OK, I notice I am confused.
Re MWI: My understanding of QM is quite good for someone who has never done the actual math. I realize that there are others whose understanding is vastly better. However, this debate is not about the equations of QM per se, but about the measure theory that tells you how “real” the different parts of them are. That is also an area where I’m no more than an advanced amateur, but it is also an area in which nobody in this discussion has the hallmarks of an expert. Which is why we’re using terms like “reality fluid”.
And my violin skills are quite good for someone who has never done the actual playing.
Different parts of what? Of equations? They are all equally real: together they form mathematical models necessary to describe observed data.
Eliezer is probably the only one who uses that and the full term is “magical reality fluid” or something similar, named this way specifically to remind him that he is confused about it.
I have actually done the math for simple toy cases like Bell’s inequality. But yeah, you’re right, I’m no expert.
(Out of curiousity, are you?)
ψ
I have a related degree, if that’s what you are asking.
I’m yet to see anyone writing down anything more than a handwaving of this in MWI. Zurek’s ideas of einselection and envariance go some ways toward showing why only the eigenstates survive when decoherence happens, and there is some experimental support for this, though the issue is far from settled.
Precisely; the issue is far from settled. That clearly doesn’t mean “any handwavy speculation is as good as any other” but it also doesn’t mean “speculation can be dismissed out of hand because we already understand this and you’re just wrong”.