Leon Battista Alberti’s vernacular treatise on painting, Della Pittura (1436), is usually characterized as a translation, aimed at artists, of his Latin De Pictura. Questioning that premise, this article situates the volgare treatise and its attached dedication letter to the architect Filippo Brunelleschi within the 1430’s language debates over the role and status of the vernacular, commonly referred to as the Questione della lingua. In this context, Della Pittura served as a persuasive rebuke to humanists who suspected the young language, without a basis in ancient texts, was unable to give voice to a learned treatise. Alberti cleverly argues that the stupendously novel topics and techniques he addresses in the treatise (fifteenth-century painting and linear perspective) and in the letter (the Cathedral of Florence dome and its inventive construction) require an equally innovative language, his lingua toscana. Rather than striving to restore ancient Latin and in turn revive ancient culture, Alberti calls his contemporaries to build a modern language, capable of capturing and conveying the artistic and architectural innovations of his age.