This article analyzes some of the reasons that led to the adoption of vernacular languages as philosophical languages between the 14th and 17th centuries in France and Italy. The article focuses on Descartes’s Discours de la méthode (1637), Sperone Speroni’s Dialogo delle lingue (1542) and Dante Alighieri’s Convivio (circa 1304-1307). The three works not only chose to write philosophy in a language with no philosophical tradition, but also offered a philosophical rationale for this decision. The article exposes and analyzes that (...) set of arguments. Key words: philosphy, vernacular language, Descartes, Sperone Speroni, Dante Alighieri. (shrink)