Also known as Tiro. Confessor of the faith. Born c.400in Gascony; died c463 A layman, he lived in Provence (where he probably died). Here his teachings on grace and free will were opposed by the monks of Marseilles and neighborhood. He was an ardent disciple of Saint Augustine, whom he defended chiefly by writing, during his lifetime and after his death, when Pope Celestine, at Prosper's behest, upbraided the bishops of Gaul and upheld Saint Augustine. Prosper unceasingly combated semi-Pelagianism, his most important prose work, On the grace of God and Free Will, refuting Collator (c.433), being directed against Cassian's ("Collator's") Conferences. Feast, June 25,.