But let us now return to where the Jew is introduced, speaking of the mother of Jesus, and saying that “when she was pregnant she was turned out of doors by the carpenter to whom she had been betrothed, as having been guilty of adultery, and that she bore a child to a certain soldier named Panthera;” and let us see whether those who have blindly concocted these fables about the adultery of the Virgin with Panthera, and her rejection by the carpenter, did not invent these stories to overturn His miraculous conception by the Holy Ghost: for they could have falsified the history in a different manner, on account of its extremely miraculous character, and not have admitted, as it were against their will, that Jesus was born of no ordinary human marriage.
It was to be expected, indeed, that those who would not believe the miraculous birth of Jesus would invent some falsehood. And their not doing this in a credible manner, but (their) preserving the fact that it was not by Joseph that the Virgin conceived Jesus, rendered the falsehood very palpable to those who can understand and detect such inventions. Is it at all agreeable to reason, that he who dared to do so much for the human race, in order that, as far as in him lay, all the Greeks and Barbarians, who were looking for divine condemnation, might depart from evil, and regulate their entire conduct in a manner pleasing to the Creator of the world, should not have had a miraculous birth, but one the vilest and most disgraceful of all?
And I will ask of them as Greeks, and particularly of Celsus, who either holds or not the sentiments of Plato, and at any rate quotes them, whether He who sends souls down into the bodies of men, degraded Him who was to dare such mighty acts, and to teach so many men, and to reform so many from the mass of wickedness in the world, to a birth more disgraceful than any other, and did not rather introduce Him into the world through a lawful marriage? Or is it not more in conformity with reason, that every soul, for certain mysterious reasons (I speak now according to the opinion of Pythagoras, and Plato, and Empedocles, whom Celsus frequently names), is introduced into a body, and introduced according to its deserts and former actions?
It is probable, therefore, that this soul also, which conferred more benefit by its residence in the flesh than that of many men (to avoid prejudice, I do not say “all”), stood in need of a body not only superior to others, but invested with all excellent qualities.
Source: Against Celsus (New Advent)