Plato, Epinomis 978b

κεκοινώνηκέν τινος, ἐπιλέλειπται παντὸς ἀριθμοῦ, καὶ δεῖ τοῦθʼ οὕτω διανοεῖσθαι τὸν μέλλοντα εὐδαίμονα τελευτήσειν· καὶ τό γε δὴ δίκαιόν τε καὶ ἀγαθὸν καὶ καλὸν καὶ πάντα τὰ τοιαῦτα οὐδείς ποτε μὴ γιγνώσκων, ἀληθοῦς δόξης ἐπιλαβόμενος, διαριθμήσεται πρὸς τὸ ἑαυτόν τε καὶ ἕτερον πεῖσαι τὸ παράπαν. ἴωμεν δὴ σκεψόμενοι πρὸς τοῦτʼ αὐτό, πῶς ἐμάθομεν ἀριθμεῖν. φέρε· τὸ γὰρ ἓν δὴ καὶ δύο γέγονε πόθεν ἡμῖν

is deficient in number altogether; and in this light must the matter be regarded by him who means to end his life in happiness. And no one who does not know the just, the good, the honorable and all the rest of such qualities, with a hold on true opinion, will number them off so as fully to persuade both himself and his neighbor. Now let us go on to inquire into the actual question of how we learnt to count in numbers. Tell me, whence have we got the conception of one and two, a natural gift that