The “pure” case of complete causal separation, as with civilizations in separate regions of a multiverse, is an edge case of acausal trade that doesn’t reflect what the vast majority of real-world examples look like. You don’t need to speculate about galactic-scale civilizations to see what acausal trade looks like in practice: ordinary trade can already be modeled as acausal trade, as can coordination between ancestors and descendants. Economic and moral reasoning already have elements of superrationality to the extent that they rely on concepts such as incentives or universalizability, which introduce superrationality by conditioning one’s own behavior on other people’s predicted behavior. This ordinary acausal trade doesn’t require formal proofs or exact simulations—heuristic approximations of other people’s behavior are enough to give rise to it.
The “pure” case of complete causal separation, as with civilizations in separate regions of a multiverse, is an edge case of acausal trade that doesn’t reflect what the vast majority of real-world examples look like. You don’t need to speculate about galactic-scale civilizations to see what acausal trade looks like in practice: ordinary trade can already be modeled as acausal trade, as can coordination between ancestors and descendants. Economic and moral reasoning already have elements of superrationality to the extent that they rely on concepts such as incentives or universalizability, which introduce superrationality by conditioning one’s own behavior on other people’s predicted behavior. This ordinary acausal trade doesn’t require formal proofs or exact simulations—heuristic approximations of other people’s behavior are enough to give rise to it.