to the south, separated into three Romance languages identified by their word for 'yes': oc language (from ), oïl language (from ) and sì language (from ). He then discusses gramatica, "grammar", which is a static language consisting of unchanging rules, needed to make up for the natural languages. In chapters ten to fifteen of the first book, Dante writes about his search for the illustrious vernacular, among the fourteen varieties he claims to have found in the Italian region in Book 1 (X,9): "Quare ad minus xiiii vulgaribus sola videtur Ytalia variari." ("Hence, Italy alone appears to display a variation of at least 14 vulgar languages.") In the second book, Dante deals with literary genres, specifying which are the ones that suit the vernacular. Models Dante took inspiration from rhetorical essays written in Latin, Occitan, Sicilian, and Italian, and from philosophical readings. The main classical rhetorical texts from which he drew information were the Ars Poetica by Horace, the Rhetorica ad Herennium by an anonymous author, and De Inventione by Cicero. About the philosophical works, it is important to know that Dante read not only first hand texts, but also summaries that sometimes were not of the original work, but of an intermediary one. The influence and importance of the contribution of the Sicilian language is emphasized by his assertion that "the first hundred and fifty years of Italian poetry was written in Sicilian". The major Occitan work that influenced Dante was probably Razós de trobar by the Catalan troubadour Raimon Vidal de Bezaudun. The Vers e regles de trobar is an amplification of Vidal's manual, by Jofre de Foixà. Both works were Occitan manuals of grammar for troubadour poetry. They implicitly and explicitly defended Occitan as the best vernacular for song and verse, prompting Dante to come to the defence of his beloved Tuscan tongue. The popularity of both singing and composing in Occitan by Italians prompted Dante to write: , meaning "To the perpetual shame and lowness of the wicked men of Italy, that praise somebody else's vernacular and despise their own, I say..." (Convivio, treatise I, XI). Dante became familiar with Saint Augustine's works, the De Consolatione Philosophiae by Boëthius, Saint Thomas Aquinas's works and some encyclopedic dictionaries like the Etymologiae by Isidore of Seville and the Livre du Tresor by Brunetto Latini. He takes also inspiration from Aristotelian philosophy, and references to texts by representatives