But MW is deterministic. Under single universe determinism, you can’t actually choose to perform an action you would not have performed. (Decision theory is either a step in the process or irrelevant). What MWI adds to that inability is a further inability to refrain. If MWI allowed freely willed agents to change the measures of their actions, then they could lower the measures of the less favoured ones...but it doesn’t.
But MW is deterministic. Under single universe determinism, you can’t actually choose to perform an action you would not have performed. (Decision theory is either a step in the process or irrelevant). What MWI adds to that inability is a further inability to refrain. If MWI allowed freely willed agents to change the measures of their actions, then they could lower the measures of the less favoured ones...but it doesn’t.
Probability is still a well-defined concept, even in a deterministic many worlds model
And you still can’t refrain.