I reiterate the galaxy example; saying that you could counterfactually make an observation by violating physical law is not the same as saying that something’s meaning cashes out to anticipated experiences. Consider the (exact) analogy between believing that galaxies exist after they go over the horizon, and that other quantum worlds go on existing after we decohere them away from us by observing ourselves being inside only one of them. Predictivism is exactly the sort of ground on which some people have tried to claim that MWI isn’t meaningful, and they’re correct in that predictivism renders MWI meaningless just as it renders the claims “galaxies go on existing after we can no longer see them” meaningless. To reply “If we had methods to make observations outside our quantum world, we could see the other quantum worlds” would be correctly rejected by them as an argument from within predictivism; it is an argument from outside predictivism, and presumes that correspondence theories of truth can be defined meaningfully by imagining an account from outside the universe of how the things that we’ve observed have their own causal processes generating those observations, such that having thus identified the causal processes through observation, we may speak of unobservable but fully identified variables with no observable-to-us consequences such as the continued existence of distant galaxies and other quantum worlds.
It seems to me that you’ve been taking your model of predictivism from people who need to read some Kripke. In Peirce’s predictivism, to assert that a statement is meaningful is precisely to assert that you have a truth condition for it, but that doesn’t mean you necessarily have the capability to test the condition.
Consider Russell’s teapot. “A teapot orbits between Earth and Mars” is a truth claim that must unambiguously have a true or false value. There is a truth condition on on it; if you build sufficiently powerful telescopes and perform a whole-sky survey you will find it. It would be entirely silly to claim that the claim is meaningless because the telescopes don’t exist.
The claim “Galaxies continue to exist when they exit our light-cone” has exactly the same status. The fact that you happen to to believe the right sort of telescope not only does not exist but cannot exist is irrelevant—you could after all be mistaken in believing that sort of observation is impossible. I think it is quite likely you are mistaken, as nonlocal realism seems the most likely escape from the bind Bell’s inequalities put us in.
MWI presents a a subtler problem, not like Russell’s Teapot, because we haven’t the faintest idea what observing another quantum world would be like. In the case of the overly-distant galaxies, I can sketch a test condition for the claim that involves taking a superluminal jaunt 13 billion light-years thataway and checking all around me to see if the distribution of galaxies has a huge NOT THERE on the side away from Earth. I think a predictivist would be right to ask that you supply an analogous counterfactual before the claim “other quantum worlds exist” can be said to have a meaning.
Just jaunt superquantumly to another quantum world instead of superluminally to an unobservable galaxy. What about these two physically impossible counterfactuals is less than perfectly isomorphic? Except for some mere ease of false-to-fact visualization inside a human imagination that finds it easier to track nonexistent imaginary Newtonian billiard balls than existent quantum clouds of amplitude, with the latter case, in reality, covering both unobservable galaxies distant in space and unobservable galaxies distant in phase space.
One big difference is that there are theoretical cracks in the lightspeed wall that don’t have any go-to-another-quantum-world analog. The Alcubierre solution to the field equations is a thing, after all. More importantly for this discussion, we can construct thought experiments about superluminal travel that have truth conditions because we know what a starfield would look like from N lightyears thataway. Quantumporting doesn’t have analogues of either of those things.
But that’s kind of a distraction. The interesting question for this discussion is how, if at all, the two claims “galaxies receding outside our light cone continue to exist” and “Russell’s teapot exists” are different. I think we agree that there is a predictivist account of “teapot”.
You assert that a predictivist definition of meaning and truth value cannot sustain an account of the “galaxies” claim, and that predictivism is therefore insufficient. I, a predictivist, deny your assertion—you have smuggled in an assumption that predictivists somehow aren’t allowed to assign meaning to counterfactuals that violate physical law, which I (a predictivist) am quite willing to do as long as hypotheically violating that physical law would not bar us from being able to cash out a truth claim in expected experiences.
I believe I am a predictivist who understands predictivism correctly and consistently. I believe you are a predictivist in practice who has failed to understand predictivism in theory.
How can we investigate, confirm, or refute these claims?
One big difference is that there are theoretical cracks in the lightspeed wall that don’t have any go-to-another-quantum-world analog.
In that case the conclusion would be that we don’t know whether or not galaxies outside of the light cone exist and whether or not they exist depend on whether the theoretical cracks actually allowing faster-then-light travel.
Eliezers position seems to be that they exist whether or not faster-then-light travel is possible.
Or are you saying that in a world where a person is certain about all physical laws that exist and there’s no faster-then-light travel, the other galaxies don’t exist for that person while they do exist for people with less knowledge about physics?
I reiterate the galaxy example; saying that you could counterfactually make an observation by violating physical law is not the same as saying that something’s meaning cashes out to anticipated experiences. Consider the (exact) analogy between believing that galaxies exist after they go over the horizon, and that other quantum worlds go on existing after we decohere them away from us by observing ourselves being inside only one of them. Predictivism is exactly the sort of ground on which some people have tried to claim that MWI isn’t meaningful, and they’re correct in that predictivism renders MWI meaningless just as it renders the claims “galaxies go on existing after we can no longer see them” meaningless. To reply “If we had methods to make observations outside our quantum world, we could see the other quantum worlds” would be correctly rejected by them as an argument from within predictivism; it is an argument from outside predictivism, and presumes that correspondence theories of truth can be defined meaningfully by imagining an account from outside the universe of how the things that we’ve observed have their own causal processes generating those observations, such that having thus identified the causal processes through observation, we may speak of unobservable but fully identified variables with no observable-to-us consequences such as the continued existence of distant galaxies and other quantum worlds.
It seems to me that you’ve been taking your model of predictivism from people who need to read some Kripke. In Peirce’s predictivism, to assert that a statement is meaningful is precisely to assert that you have a truth condition for it, but that doesn’t mean you necessarily have the capability to test the condition.
Consider Russell’s teapot. “A teapot orbits between Earth and Mars” is a truth claim that must unambiguously have a true or false value. There is a truth condition on on it; if you build sufficiently powerful telescopes and perform a whole-sky survey you will find it. It would be entirely silly to claim that the claim is meaningless because the telescopes don’t exist.
The claim “Galaxies continue to exist when they exit our light-cone” has exactly the same status. The fact that you happen to to believe the right sort of telescope not only does not exist but cannot exist is irrelevant—you could after all be mistaken in believing that sort of observation is impossible. I think it is quite likely you are mistaken, as nonlocal realism seems the most likely escape from the bind Bell’s inequalities put us in.
MWI presents a a subtler problem, not like Russell’s Teapot, because we haven’t the faintest idea what observing another quantum world would be like. In the case of the overly-distant galaxies, I can sketch a test condition for the claim that involves taking a superluminal jaunt 13 billion light-years thataway and checking all around me to see if the distribution of galaxies has a huge NOT THERE on the side away from Earth. I think a predictivist would be right to ask that you supply an analogous counterfactual before the claim “other quantum worlds exist” can be said to have a meaning.
Just jaunt superquantumly to another quantum world instead of superluminally to an unobservable galaxy. What about these two physically impossible counterfactuals is less than perfectly isomorphic? Except for some mere ease of false-to-fact visualization inside a human imagination that finds it easier to track nonexistent imaginary Newtonian billiard balls than existent quantum clouds of amplitude, with the latter case, in reality, covering both unobservable galaxies distant in space and unobservable galaxies distant in phase space.
One big difference is that there are theoretical cracks in the lightspeed wall that don’t have any go-to-another-quantum-world analog. The Alcubierre solution to the field equations is a thing, after all. More importantly for this discussion, we can construct thought experiments about superluminal travel that have truth conditions because we know what a starfield would look like from N lightyears thataway. Quantumporting doesn’t have analogues of either of those things.
But that’s kind of a distraction. The interesting question for this discussion is how, if at all, the two claims “galaxies receding outside our light cone continue to exist” and “Russell’s teapot exists” are different. I think we agree that there is a predictivist account of “teapot”.
You assert that a predictivist definition of meaning and truth value cannot sustain an account of the “galaxies” claim, and that predictivism is therefore insufficient. I, a predictivist, deny your assertion—you have smuggled in an assumption that predictivists somehow aren’t allowed to assign meaning to counterfactuals that violate physical law, which I (a predictivist) am quite willing to do as long as hypotheically violating that physical law would not bar us from being able to cash out a truth claim in expected experiences.
I believe I am a predictivist who understands predictivism correctly and consistently. I believe you are a predictivist in practice who has failed to understand predictivism in theory.
How can we investigate, confirm, or refute these claims?
In that case the conclusion would be that we don’t know whether or not galaxies outside of the light cone exist and whether or not they exist depend on whether the theoretical cracks actually allowing faster-then-light travel.
Eliezers position seems to be that they exist whether or not faster-then-light travel is possible.
Or are you saying that in a world where a person is certain about all physical laws that exist and there’s no faster-then-light travel, the other galaxies don’t exist for that person while they do exist for people with less knowledge about physics?