The Middle Ages has been characterized as a period of cultural dualism. From at least the twelfth to the fourteenth centuries medieval authors and intellectuals were operating in a diglossic situation where Latin and the vernaculars were clearly demarcated. The distinction continued to be maintained long into the period when the European vernaculars were being used, often routinely, for functions traditionally occupied by Latin. For the fifteenth-century author Alain Chartier, prolific in both Latin and French, there was a marked divergence in the transmission of his works in either language, and his authorial identity functioned differently in each case. Chartier's Latin works were transmitted alongside classical and earlier medieval Latin texts, accruing legitimacy as a recent link in the chain leading back to antiquity. His French works meanwhile were collected with French-language texts by his contemporaries or successors; here, it was Chartier's own authority which legitimized subsequent French literary production. In a gloss to Jean Josse de Marville's De modis significandi, Henri de Crissey conceptualizes the diglossic difference as follows:

Henri posits a diglossic difference between two types of language: the single “ydioma” of the clerics, taught in educational establishments, contrasts with the “ydiomata multiplicia” that laypeople learn at home. The unified nature of Latin serves to define a clerical caste in society, differentiating them from the wider population, yet it also, implicitly, unites the disparate groupings of that wider lay population into a single entity, the “Latins.”