Lionardo Salviati (1539–89), arbiter of literary and linguistic taste in Florence as well as outside Florence — Tasso and Guarini consulted him — left behind an oeuvre of great verbal art (orations, poetry, theatre pieces, and philosophical treatises), but especially a commentary on the language of Boccaccio (1313–75) which, beneath its philological appearance, hides a theory of language and a grammar of Florentine. In addition, he inspired the Accademia della Crusca which, in 1612, was to publish the first edition of its famous Vocabulary, model for the Dictionnaire of the Académie Française and other works of its kind. The paper shows how Salviati’s Avvertimenti della lingua sopra’l Decamerone (1584/86) attempt to reconcile, in a traditionalist and inoffensive manner, the diverse tendencies of the debate concerning the Italian language and to propose new, frequently revolutionary solutions. Thus Salviati proposed a model of language based on the twofold choice between contemporary popular usage and literary eclecticism and opened the theoretical possibility to linguistic innovation within the continuity of the old language. An analysis of the Avvertimenti is offered which is careful to point out the subtle relationships between philological and linguistic themes. With the help of lengthy quotations from Salviati’s treatment of the definite and indefinite articles it is shown how he reorganized the traditional grammatical schemes and how he tried to lay bare the linguistic structure of diverse facts of observed speech.