Plato, Laws 677a

ἆρʼ οὖν ὑμῖν οἱ παλαιοὶ λόγοι ἀλήθειαν ἔχειν τινὰ δοκοῦσιν; ποῖοι δή; τὸ πολλὰς ἀνθρώπων φθορὰς γεγονέναι κατακλυσμοῖς τε καὶ νόσοις καὶ ἄλλοις πολλοῖς, ἐν οἷς βραχύ τι τῶν ἀνθρώπων λείπεσθαι γένος. πάνυ μὲν οὖν πιθανὸν τὸ τοιοῦτον πᾶν παντί. φέρε δή, νοήσωμεν μίαν τῶν πολλῶν ταύτην τὴν τῷ κατακλυσμῷ ποτε γενομένην. τὸ ποῖόν τι περὶ αὐτῆς διανοηθέντες;

Do you consider that there is any truth in the ancient tales? What tales? That the world of men has often been destroyed by floods, plagues, and many other things, in such a way that only a small portion of the human race has survived. Everyone would regard such accounts as perfectly credible. Come now, let us picture to ourselves one of the many catastrophes,—namely, that which occurred once upon a time through the Deluge. And what are we to imagine about it?