Dante Alighieri's Divine Comedy, written in the early 14th century, merged a medieval world view with classical ideals. Another promoter of the Italian language was Boccaccio with his Decameron. The application of the vernacular did not entail a rejection of Latin, and both Dante and Boccaccio wrote prolifically in Latin as well as Italian, as would Petrarch later (whose Canzoniere also promoted the vernacular and whose contents are considered the first modern lyric poems). Together the three poets established the Tuscan dialect as the norm for the modern Italian language.
Who could write in latin and Italian besides Boccaccio and Petrarch?
Dante