In what ways were the Italian poetry and the humanist philosophy significant in history?
Italian poetry and humanist philosophy significant as ushering in what is termed the "Renaissance" or "rebirth". The Renaissance marked a widespread transformation in European culture.
First, in the middle ages, Church Latin, a form of late antique popular speech, with a prosody based on stress rather than quantity, became the international language of European culture and official communication. The Renaissance was marked by a rediscovery and revival of classical Latin ("Ciceronianism") for educated correspondence. The humanists, including Petrarch, wrote letters and poetry in two languages, classicizing Latin, and there local vernaculars. Thus another major Renaissance shift was the rise of vernacular literacy and literature.
The Renaissance was also marked by a revival of ancient learning (especially Greek) and a turn to the secular.