Putnam’s Twin-Earth thought experiment has been hugely influential as an argument in favor of semantic externalism. In this article, I argue that the Twin-Earth thought experiment relies on some previously unnoticed metaphysical assumptions about how to individuate words. My aim is not to argue that semantic externalism is false. Rather I aim to show that Putnam’s thought experiment is only effective as an argument for semantic externalism if we also are committed to certain additional highly controversial and/or implausible claims within the metaphysics of words. I close by arguing that a similar argument for semantic externalism by Burge also relies on unnoticed metaphysical assumptions in the metaphysics of words.
