I think the fact that the multiverse is deterministic does play a role, since if an agent’s utility function covers the entire multiverse and the agent cares about the other branches, its decision theory would suffer paralysis since any action have the same expected utility—the total amount of utility available for the agent within the multiverse, which is predetermined. Utility functions seem to only make sense when constrained to one branch and the agent treats its branch as the sole universe, only in this scenario will different actions have different expected utilities.
You are not entitled to the assumption that the other parts of the multiverse remain constant and uncorrelated to what you do. The multiverse could be superdeterministic. Failing to take into account your causes means you have a worldview in which there are two underdetermined events in the multiverse, the big bang and what you are about to do. Both versions can not be heeding local causation and everything is connected.
It makes life a whole lot more practical if you do assume it.
I think the fact that the multiverse is deterministic does play a role, since if an agent’s utility function covers the entire multiverse and the agent cares about the other branches, its decision theory would suffer paralysis since any action have the same expected utility—the total amount of utility available for the agent within the multiverse, which is predetermined. Utility functions seem to only make sense when constrained to one branch and the agent treats its branch as the sole universe, only in this scenario will different actions have different expected utilities.
You are not entitled to the assumption that the other parts of the multiverse remain constant and uncorrelated to what you do. The multiverse could be superdeterministic. Failing to take into account your causes means you have a worldview in which there are two underdetermined events in the multiverse, the big bang and what you are about to do. Both versions can not be heeding local causation and everything is connected.
It makes life a whole lot more practical if you do assume it.