Why We Shouldn’t Pity Schrödinger’s Kitty: Revisiting David Lewis’ Worry About Quantum Immortality in a Branching Multiverse

David Lewis cautions that although a no-collapse interpretation of quantum mechanics entails immortality for trans-world selves, the nature of the branching leaves us crippled, lonely, deathly ill (although never dead), and mentally infirm, meaning that immortal life, on such terms, amounts to an existence in eternal torment. This paper argues that the problem Lewis points to is in fact one of individuation and that a synthesis of Lewis’ own notion of perdurance and Robert Nozick’s closest continuer theory, when cast in the mould of a deterministic multiverse (as conceived by the Oxford quantum physicist David Deutsch), individuates trans-world selves in such a way as to allow to prune the infinitesimal expectation of a miserable eternal existence from the histories of most trans-world agents. Thus, contrary to Lewis’ warning that if personal identity is a trans-world notion, then we should all shake in our shoes, this paper argues that even if we are trans-world selves, we almost certainly have nothing to worry about.