Plato, Laws 689b

τὸ γὰρ λυπούμενον καὶ ἡδόμενον αὐτῆς ὅπερ δῆμός τε καὶ πλῆθος πόλεώς ἐστιν. ὅταν οὖν ἐπιστήμαις ἢ δόξαις ἢ λόγῳ ἐναντιῶται, τοῖς φύσει ἀρχικοῖς, ἡ ψυχή, τοῦτο ἄνοιαν προσαγορεύω, πόλεώς τε, ὅταν ἄρχουσιν καὶ νόμοις μὴ πείθηται τὸ πλῆθος, ταὐτόν, καὶ δὴ καὶ ἑνὸς ἀνδρός, ὁπόταν καλοὶ ἐν ψυχῇ λόγοι ἐνόντες μηδὲν ποιῶσιν πλέον ἀλλὰ δὴ τούτοις πᾶν τοὐναντίον, ταύτας πάσας ἀμαθίας τὰς πλημμελεστάτας

for the part of the soul that feels pain and pleasure corresponds to the mass of the populace in the State. So whenever this part opposes what are by nature the ruling principles—knowledge, opinion, or reason,—this condition I call folly, whether it be in a State, when the masses disobey the rulers and the laws, or in an individual, when the noble elements of reason existing in the soul produce no good effect, but quite the contrary.