Abstract

A novel puzzle for the notion of probability in the Many-Worlds interpretation of quantum mechanics is presented. The puzzle makes use of a thought experiment that some have claimed would provide empirical support for Many-Worlds over alternatives. It is argued that, if the predictions of Many-Worlds do indeed differ from other interpretations as claimed, then Born’s rule must generally be invalid in Many-Worlds. It is shown that the thought experiment provides a counter example for recent decision-theoretic arguments that purport to establish Born’s rule. Finally, it is shown that the puzzle can be grounded in general considerations regarding the nature of prediction in Many-Worlds.