Evil twins and the multiverse: distinguishing the world of difference between epistemic and physical possibility

Abstract

Physicists Brian Greene and Max Tegmark both make variants of the claim that if the universe is infinite and matter is roughly uniformly distributed that there are infinitely many “people with the same appearance, name and memories as you, who play out every possible permutation of your life choices.” In this paper I argue that, while our current best theories in astrophysics may allow one to conclude that we have infinitely many duplicates whose lives are identical to our own from start to finish, without either further advances in physics or advances in fields like biology, psychology, neuroscience, and philosophy, Greene’s and Tegmark’s claims about the ways in which our duplicates lives will differ from our own are not a consequence of our best current scientific theories. Rather, I argue that Greene and Tegmark’s conclusions rely on philosophically imprecise usages of the language of “possibility.”