Will Aliens have a Different Logic?

Abstract What kind of logic could beings totally alien to us possess? Could it be an unexpected variation on our logic, e.g. with modus ponens replaced by affirming the consequent ? In this paper, I argue that as no logic which has affirming the consequent in place of modus ponens can exist, the aliens’ logic cannot be exotic in this way. (Sure, the aliens could lack anything that we would call logic, but assuming they had a logic, it could not be too far-fetched vis-à-vis ours.) Moreover, I argue that our logical vocabulary has its function, and it must be such as to fulfill this function. This conclusion does not, I believe, tell us anything that is very profound about the (possible) aliens, but it does tell us something profound about logic itself.