I think that physics is best understood as answering the question “in what mathematical entity do we find ourselves?”—a question that Everett is very equipped to answer. Then, once you have an answer to that question, figuring out your observations becomes fundamentally a problem of locating yourself within that object, which I think raises lots of interesting anthropic questions, but not additional physical ones.
I disagree. “in what mathematical entity do we find ourselves?” is a map-territory confusion. We are not in a mathematical entity, we use mathematics to construct models of reality. And, in any case, without “locating yourself within the object”, it’s not clear how do you know whether your theory is true, so it’s very much pertinent to physics.
Moreover, I’m not sure how this perspective justifies MWI. Presumably, the wavefunction contains multiple “worlds” hence you conclude that multiple worlds “exist”. However, consider an alternative universe with stochastic classical physics. The “mathematical entity” would be a probability measure over classical histories. So it can also be said to contains “multiple worlds”. But in that universe everyone would be comfortable with saying there’s just one non-deterministic world. So, you need something else to justify the multiple worlds, but I’m not sure what. Maybe you would say the stochastic universe also has multiple worlds, but then it starts looking a like a philosophical assumption that doesn’t follow from physics.
Then what would you call reality? It sure seems like it’s well-described as a mathematical object to me.
without “locating yourself within the object”, it’s not clear how do you know whether your theory is true, so it’s very much pertinent to physics.
Put a simplicity prior over the combined difficulty of specifying a universe and specifying you within that universe. Then update on your observations.
The “mathematical entity” would be a probability measure over classical histories.
Not necessarily. You can mathematically well-define 1) a Turing machine with access to randomness that samples from a probability measure and 2) a Turing machine which actually computes all the histories (and then which one you find yourself in is an anthropic question). What quantum mechanics says, though, is that (1) actually doesn’t work as a description of reality, because we see interference from those other branches, which means we know it has to be (2).
Then what would you call reality? It sure seems like it’s well-described as a mathematical object to me.
I call it “reality”. It’s irreducible. But I feel like this is not the most productive direction to hash out the disagreement.
Put a simplicity prior over the combined difficulty of specifying a universe and specifying you within that universe. Then update on your observations.
Okay, but then the separation between “specifying a universe” and “specifying you within that universe” is meaningless. Sans this separation, your are just doing simplicity-prior-Bayesian-inference. If that’s what you’re doing, the Copenhagen interpretation is what you end up with (modulo the usual problems with Bayesian inference).
You can mathematically well-define 1) a Turing machine with access to randomness that samples from a probability measure and 2) a Turing machine which actually computes all the histories (and then which one you find yourself in is an anthropic question). What quantum mechanics says, though, is that (1) actually doesn’t work as a description of reality, because we see interference from those other branches, which means we know it has to be (2).
I don’t see how you get (2) out of quantum mechanics.
I think that physics is best understood as answering the question “in what mathematical entity do we find ourselves?”—a question that Everett is very equipped to answer. Then, once you have an answer to that question, figuring out your observations becomes fundamentally a problem of locating yourself within that object, which I think raises lots of interesting anthropic questions, but not additional physical ones.
I disagree. “in what mathematical entity do we find ourselves?” is a map-territory confusion. We are not in a mathematical entity, we use mathematics to construct models of reality. And, in any case, without “locating yourself within the object”, it’s not clear how do you know whether your theory is true, so it’s very much pertinent to physics.
Moreover, I’m not sure how this perspective justifies MWI. Presumably, the wavefunction contains multiple “worlds” hence you conclude that multiple worlds “exist”. However, consider an alternative universe with stochastic classical physics. The “mathematical entity” would be a probability measure over classical histories. So it can also be said to contains “multiple worlds”. But in that universe everyone would be comfortable with saying there’s just one non-deterministic world. So, you need something else to justify the multiple worlds, but I’m not sure what. Maybe you would say the stochastic universe also has multiple worlds, but then it starts looking a like a philosophical assumption that doesn’t follow from physics.
Then what would you call reality? It sure seems like it’s well-described as a mathematical object to me.
Put a simplicity prior over the combined difficulty of specifying a universe and specifying you within that universe. Then update on your observations.
Not necessarily. You can mathematically well-define 1) a Turing machine with access to randomness that samples from a probability measure and 2) a Turing machine which actually computes all the histories (and then which one you find yourself in is an anthropic question). What quantum mechanics says, though, is that (1) actually doesn’t work as a description of reality, because we see interference from those other branches, which means we know it has to be (2).
I call it “reality”. It’s irreducible. But I feel like this is not the most productive direction to hash out the disagreement.
Okay, but then the separation between “specifying a universe” and “specifying you within that universe” is meaningless. Sans this separation, your are just doing simplicity-prior-Bayesian-inference. If that’s what you’re doing, the Copenhagen interpretation is what you end up with (modulo the usual problems with Bayesian inference).
I don’t see how you get (2) out of quantum mechanics.