In his critique of the language and thought of the Scholastics, Lorenzo Valla contrasts classical Latin as a natural, common language to the so-called artificial, technical, and unnatural language of his opponents. He famously champions Quintilian’s view that one should follow common linguistic usage. Scholars, however, have disagreed about the precise interpretation of these qualifications of Latin. This article argues that, depending on the historical, rhetorical, and argumentative contexts, Valla uses notions such as common and natural in different ways to suit different purposes. Such a contextualized reading has repercussions for an evaluation of the coherence of Valla’s humanist program.