If “I” “exist” in multiple universes, I don’t view there being a fact of the matter as to which one I’m “really” in. I think at least some realists agree, and it is to that subset of realists that my argument is directed. Their worldview is internally inconsistent.
Any statement about external reality is true in some worlds and false in others. Almost all such statements will be false if you’re located in a Boltzmann brain world, for example.
I’m not using the multiverse as an axiom. It’s the possibility of a multiverse that undermines meaning of realism.
To be a realist, you need one of the following claims:
There is only one universe containing entities subjectively indistinguishable from us, or there are so few universes that we can effectively ignore them (MWI, or any other Big world theory implies otherwise)
There is a fact of the matter as to where we are under self locating uncertainty
I think e.g EY rejects both of these but is still a realist. You seem to be hinting that you believe in 2?
Note that you can further build on my QM example. Scott Aaronson has suggested that you can affect the past via your decisions in the present. I haven’t read his arguments recently but I think this is related to the self locating uncertainty point—there could be no fact of the matter as to what the initial conditions were that led to your decision until after it’s made.
, I don’t view there being a fact of the matter as to which one I’m “really” in.
But there is a fact of the matter for realists, using their definitions of truth and fact. So your conclusion isn’t coming from metaphysics alone, it’s coming from epistemology as well.
Any statement about external reality is true in some worlds and false in others
Not quite. “There is some kind reality” is true in all realities.
It’s the possibility of a multiverse that undermines meaning of realism.
There are a lot of shades and variations to realism and anti realism.
The possibility of empirically indistinguishable realities limits empiricism.
It doesn’t give you ontological anti realism, that there is no reality.
It doesn’t give you a firm conclusion that you can never have a true belief about reality, because if you assume a small world base level reality, it could be true.
(As you say: “There is only one universe containing entities subjectively indistinguishable from us, or there are so few universes that we can effectively ignore them (MWI, or any other Big world theory implies otherwise)”)
It doesn’t give you the conclusion that there is no way of placing credences on empirically indistinguishable models, because you can still use non empirical criteria such as simplicity.
It doesn’t tell you anything about semantics, which statements are meaningful.
The minimal concession realists need to make is that empirically indistinguishable distinguishable theories are harder to judge between. That’s more sceptical than the High Rationalist ideas, that you can solve everything with Bayes and Solomonoff. But it’s less sceptical than verificationism and instrumentalism.
There is a fact of the matter as to where we are under self locating uncertainty
I think e.g EY rejects both of these but is still a realist. You seem to be hinting that you believe in 2?
Realists believe in a fact of the matter, but not necessarily a verifiable fact of the matter.
If “I” “exist” in multiple universes, I don’t view there being a fact of the matter as to which one I’m “really” in. I think at least some realists agree, and it is to that subset of realists that my argument is directed. Their worldview is internally inconsistent.
Any statement about external reality is true in some worlds and false in others. Almost all such statements will be false if you’re located in a Boltzmann brain world, for example.
I’m not using the multiverse as an axiom. It’s the possibility of a multiverse that undermines meaning of realism.
To be a realist, you need one of the following claims:
There is only one universe containing entities subjectively indistinguishable from us, or there are so few universes that we can effectively ignore them (MWI, or any other Big world theory implies otherwise)
There is a fact of the matter as to where we are under self locating uncertainty
I think e.g EY rejects both of these but is still a realist. You seem to be hinting that you believe in 2?
Note that you can further build on my QM example. Scott Aaronson has suggested that you can affect the past via your decisions in the present. I haven’t read his arguments recently but I think this is related to the self locating uncertainty point—there could be no fact of the matter as to what the initial conditions were that led to your decision until after it’s made.
But there is a fact of the matter for realists, using their definitions of truth and fact. So your conclusion isn’t coming from metaphysics alone, it’s coming from epistemology as well.
Not quite. “There is some kind reality” is true in all realities.
There are a lot of shades and variations to realism and anti realism.
The possibility of empirically indistinguishable realities limits empiricism.
It doesn’t give you ontological anti realism, that there is no reality.
It doesn’t give you a firm conclusion that you can never have a true belief about reality, because if you assume a small world base level reality, it could be true.
(As you say: “There is only one universe containing entities subjectively indistinguishable from us, or there are so few universes that we can effectively ignore them (MWI, or any other Big world theory implies otherwise)”)
It doesn’t give you the conclusion that there is no way of placing credences on empirically indistinguishable models, because you can still use non empirical criteria such as simplicity.
It doesn’t tell you anything about semantics, which statements are meaningful.
The minimal concession realists need to make is that empirically indistinguishable distinguishable theories are harder to judge between. That’s more sceptical than the High Rationalist ideas, that you can solve everything with Bayes and Solomonoff. But it’s less sceptical than verificationism and instrumentalism.
Realists believe in a fact of the matter, but not necessarily a verifiable fact of the matter.