In late medieval England, textual production in English developed considerably, in literary, devotional or didactic areas, in the context of the extension of literacy. This production is both a symptom and a driving force of the formation of a specific culture, mostly lay and non-chivalric. It can be studied through the analysis of textual contents and diffusion, but also through linguistic transformations. One can enquire, especially, into how the English language comes to have a status of authority, relative to the scholarly language of the time, Latin. At the end of the fourteenth century, the English poet Geoffrey Chaucer preoccupied himself with this question, notably in two of his works, the Treatise on the Astrolabe and The House of Fame. Their study suggests that Chaucer, in consciously questioning medieval authorities, wanted to legitimate both his work and the English language, to contribute to the creation of a more open intellectual space, one which would correspond with a dynamic society.