I think it’s pretty unclear that MSR is action-guiding for real agents trying to follow functional decision theory, because of Sylvester Kollin’s argument in this post.
Tl;dr: FDT says, “Supposing I follow FDT, it is just implied by logic that any other instance of FDT will make the same decision as me in a given decision problem.” But the idealized definition of “FDT” is computationally intractable for real agents. Real agents would need to find approximations for calculating expected utilities, and choose some way of mapping their sense data to the abstractions they use in their world models. And it seems extremely unlikely that agents will use the exact same approximations and abstractions, unless they’re exact copies — in which case they have the same values, so MSR is only relevant for pure coordination (not “trade”).
Many people who are sympathetic to FDT apparently want it to allow for less brittle acausal effects than “I determine the decisions of my exact copies,” but I haven’t heard of a non-question-begging formulation of FDT that actually does this.
I think it’s pretty unclear that MSR is action-guiding for real agents trying to follow functional decision theory, because of Sylvester Kollin’s argument in this post.
Tl;dr: FDT says, “Supposing I follow FDT, it is just implied by logic that any other instance of FDT will make the same decision as me in a given decision problem.” But the idealized definition of “FDT” is computationally intractable for real agents. Real agents would need to find approximations for calculating expected utilities, and choose some way of mapping their sense data to the abstractions they use in their world models. And it seems extremely unlikely that agents will use the exact same approximations and abstractions, unless they’re exact copies — in which case they have the same values, so MSR is only relevant for pure coordination (not “trade”).
Many people who are sympathetic to FDT apparently want it to allow for less brittle acausal effects than “I determine the decisions of my exact copies,” but I haven’t heard of a non-question-begging formulation of FDT that actually does this.