No, I understand this part. My understanding of acausal trade is that it might work precisely because it does not require communication—I can imagine a sort of bargain I might have wanted to make with beings I cannot interact with causally, imagine the sorts of commitments they would have required of me, argue that they could have been full enough of foresight to imagine the same sorts of commitments, and thus act according to commitments that I know I would have made with such beings and that I know they would have made with me. The main point is this: by merely imagining that I want to make a trade, I have narrowed the class of entities I can trade with from “all plausible entities” to “entities who would accept the trade I want to make”. (There are some other nitpicks, I think acausal trade becomes nonsense if the causal isolation is two-way, but that doesn’t matter for this argument.)
If by communication you really mean information transfer, I think it’s fairly obvious that this isn’t possible. Say there is some proposition I’m uncertain about even upon strong reflection. How can spinning up another mind help? That I’m uncertain means I can imagine worlds containing minds resembling mine in which the proposition is either true or false. Can spinning up a mind from one of those worlds help me determine which of those types of worlds I’m in? Of course it cannot, I either sample minds according to my present understanding of the distribution of such minds and gain nothing or I sample minds according to another distribution and am predictably misled. If I spin up a mind to talk to, there is no constraint whatever on the sort of mind I will spin up, and so it’s impossible to predictably get information out of this mechanism.
What would it take to predictably spin up minds which can resolve a present state of uncertainty? Precisely a further constraint on which types of minds experience that uncertainty. That is, in principle, acausal communication can only predictably tell you things you already know, and must mislead you as often as it leads you right. A discerning being could design tests to filter the applicable ideas from the non-applicable, but only weakly slower than a similarly discerning being could without acausal communication, because we cannot get information from an acausal mechanism (indeed quantum-mechanically I think this is the definition of acausal!) This just isn’t what communication means to me, and I don’t think this is what it means to acausal trade theorists either.
There are sorts of things I can learn from simulating other minds which might know them. I don’t know the millionth digit of pi, so maybe I can spin up a mind which I know will know it. Doing this is obviously as hard as computing it directly so I don’t see why I would do this. Maybe there are lots of things I don’t know and so I want to spin up a mind which will know all of them at once. Doing this is called creating artificial intelligence and I don’t see how it’s meaningful to think of it as acausal communication with an entity from a different possible universe rather than as causal communication with an entity I’ve created in this universe. Can you describe a situation in which I might do acausal communication that is not actually causal communication, or where this framing could in principle be useful? I still feel that I might be missing something.
Comment withdrawn ◉
No, I understand this part. My understanding of acausal trade is that it might work precisely because it does not require communication—I can imagine a sort of bargain I might have wanted to make with beings I cannot interact with causally, imagine the sorts of commitments they would have required of me, argue that they could have been full enough of foresight to imagine the same sorts of commitments, and thus act according to commitments that I know I would have made with such beings and that I know they would have made with me. The main point is this: by merely imagining that I want to make a trade, I have narrowed the class of entities I can trade with from “all plausible entities” to “entities who would accept the trade I want to make”. (There are some other nitpicks, I think acausal trade becomes nonsense if the causal isolation is two-way, but that doesn’t matter for this argument.)
If by communication you really mean information transfer, I think it’s fairly obvious that this isn’t possible. Say there is some proposition I’m uncertain about even upon strong reflection. How can spinning up another mind help? That I’m uncertain means I can imagine worlds containing minds resembling mine in which the proposition is either true or false. Can spinning up a mind from one of those worlds help me determine which of those types of worlds I’m in? Of course it cannot, I either sample minds according to my present understanding of the distribution of such minds and gain nothing or I sample minds according to another distribution and am predictably misled. If I spin up a mind to talk to, there is no constraint whatever on the sort of mind I will spin up, and so it’s impossible to predictably get information out of this mechanism.
What would it take to predictably spin up minds which can resolve a present state of uncertainty? Precisely a further constraint on which types of minds experience that uncertainty. That is, in principle, acausal communication can only predictably tell you things you already know, and must mislead you as often as it leads you right. A discerning being could design tests to filter the applicable ideas from the non-applicable, but only weakly slower than a similarly discerning being could without acausal communication, because we cannot get information from an acausal mechanism (indeed quantum-mechanically I think this is the definition of acausal!) This just isn’t what communication means to me, and I don’t think this is what it means to acausal trade theorists either.
There are sorts of things I can learn from simulating other minds which might know them. I don’t know the millionth digit of pi, so maybe I can spin up a mind which I know will know it. Doing this is obviously as hard as computing it directly so I don’t see why I would do this. Maybe there are lots of things I don’t know and so I want to spin up a mind which will know all of them at once. Doing this is called creating artificial intelligence and I don’t see how it’s meaningful to think of it as acausal communication with an entity from a different possible universe rather than as causal communication with an entity I’ve created in this universe. Can you describe a situation in which I might do acausal communication that is not actually causal communication, or where this framing could in principle be useful? I still feel that I might be missing something.