Justinian is the emperor who speaks the whole of canto VI, in the heaven of Mercury, where those who acted for honor and fame are. He speaks without interruption by Dante, by Beatrice, or by any other spirit. He introduces himself with two tenses of the verb: he was Caesar, he is Justinian, and he says that, by the will of the first love he feels, he removed from the laws what was superfluous and vain.
He tells how, before the work on the laws, he believed in a single nature in Christ, until Pope Agapetus guided him to sincere faith, and how he handed the arms over to Belisarius. Then he narrates the history of the Roman eagle, from Aeneas to Charlemagne, passing through Constantine, who turned it against the course of heaven. The history is not chronicle, it is argument: Justinian wants Dante to see with how much reason someone moves against the sign when he appropriates it and when he opposes it.
The judgment is symmetrical: one side opposes the public sign with the yellow lilies, the other takes it for a party, and it is hard to see who errs more. The canto closes with Mercury and with Romeo, a humble pilgrim who made the four daughters of the count queens, was badly paid, and left poor. In Mercury, the difference of seat is harmony: diverse voices make sweet notes.