How do human souls relate to the truth?

Socrates likens the souls of men and gods to chariots led by two winged horses. The gods possess horses of entirely good breed and are thus able to fly in heaven eternally. The souls of men, however, are all burdened by the combination of a good and a bad horse: inevitably, they are dragged down to earth. Once on earth, all souls must wait ten thousand years before growing back their wings—except for the philosophers, who can sprout wings and return to heaven in three thousand years. The human soul plays a crucial role in the Phaedrus because it is linked to both eros and rhetoric; can these things keep both horses, or at least one or the other, under control? Taking a correct approach to eros and rhetoric qualifies a soul as philosophic, and such a soul is consequently granted the summum bonum of an early return to heaven.