In the next place, as he represents the Jews accounting in a way peculiar to themselves for their belief that the advent of Christ among them is still in the future, and the Christians as maintaining in their way that the coming of the Son of God into the life of men has already taken place, let us, as far as we can, briefly consider these points. According to Celsus, the Jews say that “(human) life, being filled with all wickedness, needed one sent from God, that the wicked might be punished, and all things purified in a manner analogous to the first deluge which happened.”
And as the Christians are said to make statements additional to this, it is evident that he alleges that they admit these. Now, where is the absurdity in the coming of one who is, on account of the prevailing flood of wickedness, to purify the world, and to treat every one according to his deserts? For it is not in keeping with the character of God that the diffusion of wickedness should not cease, and all things be renewed. The Greeks, moreover, know of the earth's being purified at certain times by a deluge or a fire, as Plato, too, says somewhere to this effect: “And when the gods overwhelm the earth, purifying it with water, some of them on the mountains,” etc., etc.
Must it be said, then, that if the Greeks make such assertions, they are to be deemed worthy of respect and consideration, but that if we too maintain certain of these views, which are quoted with approval by the Greeks, they cease to be honourable? And yet they who care to attend to the connection and truth of all our records, will endeavour to establish not only the antiquity of the writers, but the venerable nature of their writings, and the consistency of their several parts.
Source: Against Celsus (New Advent)