The philosopher Donald Davidson has argued in an influential article, “On the Very Idea of a Conceptual Scheme,” that there is no intelligible basis on which to distinguish between conceptual schemes that Kuhn and Feyerabend have treated as incommensurable or incompatible. He concludes that, given the underlying methodology of interpretation of speech behavior, we cannot be in a position to judge that others have concepts or beliefs radically different from our own. Thus, he adds, we cannot talk meaningfully about the existence of conceptual schemes. I offer a historical rejoinder to Davidson, focusing on the famous seventeenth-century debate between Descartes and Gassendi regarding the use of the first-person pronoun. I show that, in this particular debate, their failure to translate the pronoun “I” was so basic and fundamental a failure that, although it turned on just one word, it forced Gassendi to question the longstanding Renaissance humanist principle of the intertranslatability of all natural languages. Could the Gassendi-Descartes debate similarly challenge Davidson’s assertion of the intertranslatability of all natural languages and his consequent denial of the existence of conceptual schemes?