Written c. 400 A.D., some say 398 A.D., but Augustin places it some time after the treatise on Baptism: Retractt. Bk. ii. xxv. From the same, we gather the following points as to the origin of this treatise: Before A. had finished his books on the Trinity and his word-for-word commentary on Genesis, a reply to a letter which Petilian had addressed to his followers, only a small part of which however had come into A.'s hands, demanded immediate preparation. This constitutes Book First. Subsequently the whole document was obtained, and he was engaged in preparing the second Book, c. 401; but even before the full treatise of Petilian had been secured, the latter had obtained A.'s first book, and afterwards put an epistle abusive of A. in circulation. The answer to this latter is Book Third, c. 402. Petilian. was originally an advocate. The opponents charged him with having become a Donatist by compulsion, with assuming the title of Paraclete, and with endeavoring to prevent all access on their part to his writings.