other · 431 · Rome
Prosper was not a cleric and never became one. He was a married layman of Aquitaine living at Marseille, and when the monks around him — Cassian's houses among them, refined in this dataset at seed 170 — began arguing that Augustine had gone too far on grace and predestination, he wrote to Augustine himself while Augustine was still alive, and then, after his death, travelled to Rome with his friend Hilary to ask Celestine to intervene. He got a letter defending Augustine's memory and pointedly declining to condemn anyone by name, which is roughly the outcome the case deserved. He spent the next thirty years softening his own position until it was closer to the men he had attacked. Gennadius, writing at Marseille a generation later, lists his chronicle and the anonymous book against Cassian, and adds a claim worth having: that the letters of Leo against Eutyches — including, by implication, the Tome that Chalcedon accepted — were dictated by Prosper. He was by then a secretary in the papal chancery, so it is not a wild attribution.
Augustine is dead a year and the monks of Provence are picking his doctrine apart. Who answers?
A layman with no office at all, who goes to the pope in person.