The De vulgari eloquentia is an essay about language usage, written in Latin. It’s composed by two books and is unfinished.
This work can be considered as the first work of literary criticism and the first history of Italian literature. Moreover, Dante shows his ideas about the problem named "questione della lingua" in it. He states that it’s time to use Italian dialects also in literature, and not only in spoken language. Latin should be used only in technical works (such as essays).
To explain these ideas, he first distinguishes between the natural language (locutio prima) which everybody learns directly from his parents, and the secondary language (locutio secundaria or gramatica) which is the language used to study and learnt at school (that is the Latin). In Dante’s opinion, the first language is nobler than the other, since it’s more natural and is better for art. He assures that a technical language is needed anyway, but this language (the Latin) must not be used in literature. Then, Dante explains how, according to the Bible, many different languages have derived from an ancient unique language (to do this, he use the story of the Tower of Babel). Dante wants also to choose which language is the best to be used in literature. He analyzes all the Italian dialects (they were 14) but he rejects them all, since they’re not good enough. In fact, he thinks that the ideal language should have four basic features: it must be eminent (illustre), cardinal (cardinale), aulic (aulico) and courtly (curiale). Since such a language doesn’t exist, Dante states that it must be created by poets and used by them in their works.
Despite these ideas, Dante is usually influenced by the Florentine dialect in his works, even if by its most affected aspects.
From this time on, the questione della lingua will be discussed in Italy for the following centuries, and there will be different theories and different dialects will be used. There won’t ever been a definitive solution to the problem, at least until after the second World war. After that, the spread of the television will finally set a common ground for the language used by all Italians, in both the written and oral forms.