On Eloquence in the Vernacular (De vulgari eloquentia)
Dante Alighieri
This book is in Latin.
Dante’s unfinished Latin treatise on the vernacular (c. 1303-1305): Book I on the origin of languages and the search for the illustrious vernacular through the dialects of Italy (19 chapters); Book II on the art of the canzone and the tragic style (14 chapters, breaking off mid-argument). The Latin text is the one on The Latin Library (Società Dantesca Italiana tradition).