Commentary Par VI 34

The Eagle is marked by virtù (usually 'power' but, at times, as here, 'virtue'), precisely what the opposing Italian political parties lack.  The ensuing list of virtuous founding presences harps upon the moral virtues that separated Romans from their enemies.  See Convivio (Conv.IV.iv.11) for an earlier expression of Dante's firm belief in the moral superiority of the Romans: 'Therefore, since this office [rulership] could not be attained without the greatest virtue, and since its exercise required the greatest and most humane kindness, this was the people best disposed to receive it' (tr. R. Lansing).