3 Cyprian, a man renowned both for his eloquence and for his martyr's death, was assailed— so Firmian tells us — for having used in his treatise against Demetrius passages from the Prophets and the Apostles which the latter declared to be fabricated and made up, instead of passages from the philosophers and poets whose authority he, as a heathen, could not well gainsay. Celsus and Porphyry have written against us and have been ably answered, the former by Origen, the latter by Methodius, Eusebius, and Apollinaris. Origen wrote a treatise in eight books, the work of Methodius extended to ten thousand lines while Eusebius and Apollinaris composed twenty-five and thirty volumes respectively.
Read these and you will find that compared with them I am a mere tyro in learning, and that, as my wits have long lain fallow, I can barely recall as in a dream what I have learned as a boy. The emperor Julian found time during his Parthian campaign to vomit forth seven books against Christ and, as so often happens in poetic legends, only wounded himself with his own sword. Were I to try to confute him with the doctrines of philosophers and stoics you would doubtless forbid me to strike a mad dog with the club of Hercules.
It is true that he presently felt in battle the hand of our Nazarene or, as he used to call him, the Galilæan, and that a spear-thrust in the vitals paid him due recompense for his foul calumnies. To prove the antiquity of the Jewish people Josephus has written two books against Appio a grammarian of Alexandria; and in these he brings forward so many quotations from secular writers as to make me marvel how a Hebrew brought up from his childhood to read the sacred scriptures could also have perused the whole library of the Greeks. Need I speak of Philo whom critics call the second or the Jewish Plato?
Source: Letters (New Advent)