Counterpart theory and modal realism aren't incompatible

Abstract

Jim Stone has recently argued that counterpart theory and modal realism are incompatible. His argument relies on a particular modal claim about the nature of the Lewisian pluriverse: I argue that the person who believes in counterpart theory and modal realism ought not to accept this claim though. I conclude that Stone has not shown that counterpart theory and modal realism are incompatible. Jim Stone (2009: 650–51) presents the following argument against the compatibility of Lewisian modal realism and counterpart theory: Let a situation S be one at any possible world where someone finds a wallet and is free to choose whether or not to return that wallet; and let someone be free to choose to return a wallet iff if they return the wallet they could have not returned it and if they don’t return the wallet they could have returned it. It’s possible that every person in S (no matter what possible world they’re in)1 freely returns the wallet.