When and how, we might ask, did this temperamental, politically-obsessed and sexually driven man, who spent much of his life wandering from place to place, ever find the time or conditions to write “The Divine Comedy,” the greatest masterpiece of Italian literature?

Neither of those questions has a certain answer. Nobody knows precisely when Dante started writing his “Commedia,” although he seems to have begun work on it in Florence, before his exile. (The title doesn’t refer to humor in the modern sense, but is a more ancient use of the word, meaning a work with a good or happy ending.)