What language or languages were spoken and written in different social situations in Italy during Dante's time? ‘Italian’, namely a common language used across the whole peninsula, clearly did not exist, neither as the language spoken by the entire population, nor even as the language of culture shared by intellectuals coming from all of Italy's regions and used in written communication from the Alps to Sicily. Literary language was not standardized until the sixteenth century, between two and two and a half centuries after Dante had written the Commedia. From the Cinquecento onwards, Italian intellectuals throughout Italy wrote essentially in the same Italian language, while the uneducated, who were for the most part illiterate, continued to communicate orally – and exclusively – in their own dialects for all the practical needs of day-to-day life. It has been estimated that when Italy achieved political unification in 1861, only 10 per cent of its population spoke Italian, so that the language could only be considered national on the literary level. However, the presence of a unified state put social processes in motion that gradually led to Italian becoming the spoken language of all, or nearly all, Italians.

Indeed, it is justifiably asserted that Dante was ‘the father of the Italian language’, since Italian does not predate him. This fact inevitably raises the question in just what language did Dante write the Commedia and his other vernacular works. The correct response is that Dante wrote the poem in the Florentine vernacular, his mother tongue, which later was to become Italian through a process that would take more than two centuries. It would do so by imposing itself on the vernaculars of other Italian cities, thanks primarily to the prestige of the great Florentine writers of the Trecento, especially Dante himself, but also Petrarch (1304–74) and Boccaccio (1313–75). It can thus be claimed that Dante is ‘the father of the Italian language’ because, by writing his masterwork in the Florentine vernacular, he increased the expressive and communicative capacity of this language to such a degree that it was given a very powerful push towards becoming the future hegemonic literary and national language of the entire country.