1. Most reverend fathers, this is not something which I have instigated nor is it a mark of my own presumption, but rather, as you yourselves recognize, it is of the most dire and even desperate necessity that I now appear. Indeed, I have been forced to do this because of an injustice done to me, and now I stand not only as a defender of my faith but also as a witness to another's faithlessness. [...]
Orosius defends the necessity to defend the Catholic faith against heretics, especially the Origenists, Priscillianists, Jovinianists, and Pelagians. He refers to the biblical passages, and compares himself to David fighting "the Goliath of heresies."
3. [...] It was you who wanted me to be a participant in your struggle, to come as a helper, not as the champion. In as much as I lay in obscurity at Bethlehem, a foreigner, penniless and unknown, why am I, an unfortunate man speaking this way, perhaps to be reprimanded again for boasting? Indeed, David himself was also such a man and he, too, came from that place. So, I lay in obscurity at Bethlehem, having been instructed by father Augustine to learn the fear of the Lord by sitting at the feet of Jerome. From there I travelled to Jerusalem, called by your summons. After this I came up to your assembly, together with you, on the orders of Bishop John. There all of you requested from my insignificant person that I disclose truthfully and simply whether I knew anything that had occurred in Africa concerning that heresy which Pelagius and Caelestius have sown. [...]
(trans. Hanson 1999: 118)