Celsus next proceeds to say, that the system of doctrine, viz., Judaism, upon which Christianity depends, was barbarous in its origin. And with an appearance of fairness, he does not reproach Christianity because of its origin among barbarians, but gives the latter credit for their ability in discovering (such) doctrines. To this, however, he adds the statement, that the Greeks are more skilful than any others in judging, establishing, and reducing to practice the discoveries of barbarous nations.
Now this is our answer to his allegations, and our defence of the truths contained in Christianity, that if any one were to come from the study of Grecian opinions and usages to the Gospel, he would not only decide that its doctrines were true, but would by practice establish their truth, and supply whatever seemed wanting, from a Grecian point of view, to their demonstration, and thus confirm the truth of Christianity. We have to say, moreover, that the Gospel has a demonstration of its own, more divine than any established by Grecian dialectics.
And this diviner method is called by the apostle the “manifestation of the Spirit and of power:” of “the Spirit,” on account of the prophecies, which are sufficient to produce faith in any one who reads them, especially in those things which relate to Christ; and of “power,” because of the signs and wonders which we must believe to have been performed, both on many other grounds, and on this, that traces of them are still preserved among those who regulate their lives by the precepts of the Gospel.
Source: Against Celsus (New Advent)