Plato, Letters 321d

περί τε τῶν ἄλλων ὧν ἂν φράζῃς καὶ ὡς Εὐφραίῳ δεῖ τὰ νῦν χρῆσθαι. πολλὰ μὲν γὰρ ὁ ἀνὴρ χρήσιμος, μέγιστον δὲ οὗ καὶ σὺ νῦν ἐνδεὴς εἶ διά τε τὴν ἡλικίαν καὶ διὰ τὸ μὴ πολλοὺς αὐτοῦ πέρι συμβούλους εἶναι τοῖς νέοις. ἔστιν γὰρ δή τις φωνὴ τῶν πολιτειῶν ἑκάστης καθαπερεί τινων ζῴων, ἄλλη μὲν δημοκρατίας, ἄλλη δʼ ὀλιγαρχίας, ἡ δʼ αὖ μοναρχίας·

both about the other matters you mention and as to how you ought now to make use of Euphraeus. For the man is useful for many things, the most important being that in which you yourself are deficient owing to your youth, and also because it is a matter about which there are not many counsellors available for the young. For forms of government, like animals, have each their own kind of language, one for democracy, another for oligarchy, and a third kind for monarchy; and though a vast number of people would assert that they understand these languages, yet all but a few of them