"It is clear that those who corrupted the Corinthians were not from among them, but outsiders. Of course, they boasted that the Apostles taught imperfectly, while they, by contrast, brought something greater. For probably, while speaking idly about many things, they introduced foolish trifles into the dogmas of the faith. Therefore, since they used external wisdom and, as is likely, spoke much emptiness, the Apostle says: if they had told you something beyond this, and had preached another Christ, more fully, while we had kept silence, 'you might well have endured it.' But if they have the same foundations of faith, what advantage is there? However much they speak, they will not say more than what we have already said. Why, then, do you listen to them?"
Yet because the false teachers, despite teaching empty things, boasted that they were better than the Apostles, Paul was unwillingly compelled to speak of his relation to the Apostles chosen before him. He says, first, that he is in no way less than the other Apostles. Second, he understands Christ's teaching just as they do. St. John Chrysostom explains this: "See what modesty there is here also. He does not say, 'The Apostles have said no more than I.' Rather, he says, 'I think,' that is, 'I think that I have in no way fallen short of the chief Apostles.' Since the Corinthian false teachers also imagined they could compare themselves with the Apostles, St. Paul compares himself with the Apostles in a way fitting for him. Therefore he speaks of them with praise, calling them not simply Apostles, but chief, having Peter, James, and John in view."
Turning again to compare himself with those who had deceived the Corinthians, the Apostle says that he is unskilled in speech. Yet he was far from being such. He had studied in Hebrew schools, not Hellenic ones. For this reason he could seem ignorant of Greek eloquence. Yet he possessed the power of speech common to all mankind. Above all, he had a true understanding of everything necessary to know for salvation. The Greek sophists, the talkers, knew how to speak elegantly and smoothly, but they preached false teachings (cf. 1 Cor. 1:2). According to blessed Theodoret, St. Paul is saying to them, as it were: "Though my tongue is not learned, my mind is adorned with the knowledge of God."