But the Greeks will say that these accounts are fabulous, although two whole nations are witnesses to their truth. But why may we not consider the accounts of the Greeks as fabulous rather than those? Perhaps some one, however, wishing not to appear blindly to accept his own statements and reject those of others, would conclude, after a close examination of the matter, that the wonders mentioned by the Greeks were performed by certain demons; those among the Jews by prophets or by angels, or by God through the means of angels; and those recorded by Christians by Jesus Himself, or by His power working in His apostles.
Let us, then, compare all these accounts together; let us examine into the aim and purpose of those who performed them; and let us inquire what effect was produced upon the persons on whose account these acts of kindness were performed, whether beneficial or hurtful, or neither the one nor the other. The ancient Jewish people, before they sinned against God, and were for their great wickedness cast off by Him, must evidently have been a people of great wisdom. But Christians, who have in so wonderful a manner formed themselves into a community, appear at first to have been more induced by miracles than by exhortations to forsake the institutions of their fathers, and to adopt others which were quite strange to them.
And indeed, if we were to reason from what is probable as to the first formation of the Christian society, we should say that it is incredible that the apostles of Jesus Christ, who were unlettered men of humble life, could have been emboldened to preach Christian truth to men by anything else than the power which was conferred upon them, and the grace which accompanied their words and rendered them effective; and those who heard them would not have renounced the old-established usages of their fathers, and been induced to adopt notions so different from those in which they had been brought up, unless they had been moved by some extraordinary power, and by the force of miraculous events.
Source: Against Celsus (New Advent)