Another branch of Christian literature was addressed to those outside the church in order to explain to them the Christian religion and to defend it against attacks from all quarters. The need of this apologetic literature was all the greater, as no other ancient religion had to encounter a more sustained opposition. The earliest Christian apologies of which we have notice (by Aristides and by Melito, bishop of Sardes) belong to the reign of Antoninus. Under M. Aurelius, attacks by two literary men, Cornelius Fronto and Celsus, drew several rejoinders, among which the dialogue named Octavius, by Minucius Felix, is the most ancient surviving specimen. In the fourth century, an intensified onslaught by the later neo-Platonist philosophers was capped by a redoubled Christian propaganda, culminating in the De Civitate Dei of St. Augustine (354-430), which was accepted as the classic justification of the Christian faith. Though the Christian apologists occasionally lost their patience – examples of harmful recrimination will be found in the Apologia of the African rhetorician Tertullian (c. 160-230) – they maintained, on the whole, a tone of studious moderation and met their antagonists point by point. No other ancient religion was as fortunate as Christianity in the manner of its presentation.
From: A History of Rome Down to the Reign of Constantine by M. Cary; 2nd edition (London: Macmillan & Co., Ltd., 1954), p. 764. The first edition was published in 1935.