Plato, Epinomis 977d

δὲ ἄλλην ἀρετήν, ἀνδρείαν καὶ σωφροσύνην, οὐδὲν ἀποκωλύει. στερόμενος δὲ ἀληθοῦς λόγου σοφὸς οὐκ ἄν ποτε γένοιτο, ὅτῳ δὲ σοφία μὴ προσείη, πάσης ἀρετῆς τὸ μέγιστον μέρος, οὐκ ἂν ἔτι τελέως ἀγαθὸς γενόμενος εὐδαίμων ποτὲ γένοιτο. οὕτως ἀριθμὸν μὲν ἀνάγκη πᾶσα ὑποτίθεσθαι· διότι δὲ τοῦτο ἀνάγκη, λόγος ἔτι πλείων πάντων γίγνοιτʼ ἂν τῶν εἰρημένων. ἀλλὰ καὶ ὁ νῦν ὀρθῶς ῥηθήσεται, ὅτι καὶ τὰ τῶν ἄλλων τεχνῶν λεγόμενα, ἃ νυνδὴ διήλθομεν ἐῶντες εἶναι πάσας τὰς

courage and temperance—it is certainly not debarred: but if a man is deprived of true telling he can never become wise, and he who has not the acquirement of wisdom—the greatest part of virtue as a whole—can no more achieve the perfect goodness which may make him happy. Thus it is absolutely necessary to postulate number; and why this is necessary can be shown by a still fuller argument than any that has been advanced. But here is one that will be particularly correct—that of the properties of the other arts, which we recounted just now in granting the existence of all the arts,