De Vulgari Eloquentia by Dante Alighieri is a philosophical treatise written in Latin between 1302 and 1305. It discusses the evolution of language and the search for a common, illustrious vernacular language that could be used for literary purposes. Dante examines the different dialects of Italy and argues that none of them is inherently superior to the others. He also discusses the role of grammar and rhetoric in the development of a literary language. Although never finished, the treatise is an important work in the history of linguistics and literary theory.