Petilianus, an eminent Donatist bishop, probably a native of Constantina
or Cirta, chief town of Numidia, born of parents who were Catholics; but while
still a catechumen carried off against his will by the Donatists, received by
baptism into their community, and subsequently made, between 395 and 400, their
bishop in Cirta. (Aug. c. Lit. Petil. ii. 104, 238; Serm. ad pleb. Caesar. de Emerito, 8.) He had practised as a lawyer with great success, so as to obtain the name of the Paraclete, the identity of which name with that of the Holy Spirit, if we may believe St. Augustine, was flattering to his vanity (c. Lit. Petil. iii. 16, 19). He took a prominent part in the Conference, 411, as one of the seven managers on the Donatist side, but after this we hear no more of him. (Aug. Retract. ii. 34; c. Lit. Petal. ii. 40, 95; iii. 57, 69; Optatus, Opp. Mon. Vet. Don. liii.) About 398 or 400, Augustine in a private letter invited some of the leaders of the Donatist sect in Cirta to discuss the questions at issue between them and the church, an invitation rejected by them with contempt. But when he was in the church of that place, together with Absentius (Alypius) and Fortunatus its Catholic bishop, a letter addressed by the Donatist bp. (Petilianus, but without a name) to his own clergy, proposing to cut off communion with the Catholic church, was put into Augustine's hands. This proposal seemed so monstrous as to make him doubt whether the letter could have proceeded from a man of Petilian's reputation, until he was assured that this was the case. Lest his silence should be misunderstood, he undertook at once to reply to it, though it was plainly imperfect and ought to be presented in a complete state. The writer accuses the Catholics of making necessary a repetition of baptism, because, he says, they pollute the souls of those whom they baptize. The validity of baptism in his view depends on the character of the giver, as the strength of a building depends on that of the foundation. He quotes Ecclus. xxxiv. 30 [25], applying to his own sect the words "wise men" (Matt. xxiii. 34), and interpreting the word "dead" to mean an ungodly person; he charges the Catholics with persecution and "tradition," and makes an insinuation about Manicheism. To these charges, Augustine replied in his first book against Petilian.
In his second book, for the benefit of the less acute among his brethren
(tardiores patres) he takes one by one the charges of Petilian, whose
letter had by that time been received in a complete state. The statements, 108
in number, including applications of Scripture passages, and an appeal to the
Catholics, are answered by Augustine seriatim. The arguments used by
Petilian come under two principal heads, but are much intermixed, and contain
much coarse vituperation. (1) The inefficacy of baptism by ungodly persons. (2) The iniquity of persecution. In his reply Augustine shews, (1) The true nature of baptism. Those who fall away after baptism must return, not by rebaptism, but by repentance. (2) As to persecution. Augustine denies the charge, and retorts it upon his adversary, whose partisans, the Circumcellions and others, were guilty of persecution. (3) In near connexion with the last question comes that of appeal to the civil power; Augustine shews that the Donatists themselves appealed to Constantine, and took advantage of the patronage of Julian. (4) Language of Scripture and of the church perverted.
Of a second letter from Petilian only some passages quoted by Augustine are
extant, but it appears from Augustine's reply to have contained no new arguments
but much personal abuse (Possidius, Indiculus, iii.).
In close connexion with these letters is the treatise of St. Augustine on
the Unity of the Church, written between the second and third of them, and intended to answer the question, "Where is the church?"