PROSPER OF AQUITAINE: Champion of the theology of Augustine; b. in Aquitaine probably about 390; d. after 455. Of his life little is known. His full name seems to have been Prosper Tyro, as is stated both by the Brussels manuscript of his chronicle and by Bede (De arte metrica, xxii.). He was apparently the author of the Poema conjugis ad uxorem, which seems to have been written about 415, and his works show that he received the customary rhetorical education. Theologically he was a disciple of Augustine, though the two never met, and his entire theological activity consisted in the adaptation and defense of Augustinian ideas.
The first relatively certain date in the life of Prosper is that be was in southern Gaul in 428. He seems to have lived in the closest association with the monastic circles of Marseilles, of which his phraseology clearly shows that he regarded himself a member. This was possible even if Prosper's wife were still living, provided be voluntarily subjected himself to continence, as did Paulinus of Nola or Salvianus. Marseilles, however, was the fountain head of the theological tendency later designated as Semi Pelagianism. Prosper felt it his duty to oppose this movement and accordingly requested the aid of Augustine, who responded with the De prædestinatione sanctorum and De dono perseverantiæ. During the ensuing period of somewhat profitless controversy Prosper wrote his poem, De ingratis, devoted to a refutation of Pelagianism and to an account of Semi-Pelagian doctrines, so presented as to emphasize their relationship to Pelagianism itself. Although of little poetic value, it can not be denied that the De ingratis gives a warm and lively expression of its author's convictions.
After Augustine's death, Prosper wrote in defense of his teacher's doctrines on predestination his Pro Augustino responsiones ad capitula objectionum Gallorum calumniantium, in which he merely accepts or rejects the deductions drawn from Augustine's writings without attempting to solve the difficulties involved, his formula being, "A thing must not be condemned because it cannot be understood." Prosper was now considered the leading representative of Augustinian doctrine, and two Genoese monks, Camillus and Theodorus, appealed to him for an explanation of certain obscurities in Augustine's De prædestinatione sanctorum and De dono perseverantiæ, his answer being his Responsiones ad excerpta Genuensium. About the same time he was forced to defend himself against certain opinions attributed to him, in a captious and prejudiced fashion, by a certain Vincentius who is probably to be identified with Vincent of Lerins (q.v.). This attack Prosper easily met, but despite all his energy he was unable to ensure the victory of Augustine's doctrines in Marseilles. He and Hilarius accordingly went to Romee, at latest by the spring of 432, to secure aid from Celestine I. (see SEMI-PELAGIANISM), and on his return he wrote, in 433 or 434, a reply to the critics of Johannes Cassianus (q.v.) on the teachings of Augustine, his refutation being entitled De gratia Dei et libero arbitrio. As a bit of polemics the work is not unskilful, although it does not solve its problem, not only because Prosper failed to recognize the relative justice of his opponent's position, but also because he contented himself with a mere logical demonstration of discrepancies between Pelagianism and Semi-Pelagianism. To this same period belongs the worthless Epitaphium Nestorianæ et Pelagianæ hæreseon, occasioned by the condemnation of Nestorius and Celestius at the Synod of Ephesus in 431.
Shortly after his attack on Cassianus Prosper left Gaul for Rome. This fact is clear from a study of his chronicle, the first part of which (to the death of Valens in 378) is excerpted from Eusebius and Jerome, with a few additions from Augustine's Hær.; the second part, however, is by Prosper himself. The first section of this latter portion extends to 433, and a third of the notices refers to Gaul, where it was composed. The second and third sections (to 445 and 455 respectively), on the other hand, were written altogether from the standpoint of a Roman, and evidently at Rome.
That Prosper ever remained devoted to Augustine is shown by his book of epigrams, clothing Augustine's ideas in poetic form, and probably written after the Council of Chalcedon. For this collection of 106 poems Prosper had already made preparation in his Liber sententiarum, an anthology based partly directly and partly indirectly on Augustine and probably compiled after the condemnation of Nestorius.
A number of writings are incorrectly ascribed to Prosper: the De vocatione gentium, composed by a less cumbrous Augustinian than Prosper; the Carmen de providentia, written about 417; the De promissionibus et prædicationibus of an African adherent of Augustine; and the De vita contemplativa of Julianus Pomerius (q.v.). The Confessio, on the other hand, assigned to Prosper on manuscript authority was probably written by him.