Plato, Letters 313a

οὐδὲν ἱκανῶς ἔχει. τοῦ δὴ βασιλέως πέρι καὶ ὧν εἶπον, οὐδέν ἐστιν τοιοῦτον—τὸ δὴ μετὰ τοῦτο ἡ ψυχή φησιν— ἀλλὰ ποῖόν τι μήν; τοῦτʼ ἐστίν, ὦ παῖ Διονυσίου καὶ Δωρίδος, τὸ ἐρώτημα ὃ πάντων αἴτιόν ἐστιν κακῶν, μᾶλλον δὲ ἡ περὶ τούτου ὠδὶς ἐν τῇ ψυχῇ ἐγγιγνομένη, ἣν εἰ μή τις ἐξαιρεθήσεται, τῆς ἀληθείας ὄντως οὐ μή ποτε τύχῃ. σὺ δὲ τοῦτο πρὸς ἐμὲ ἐν τῷ κήπῳ ὑπὸ ταῖς δάφναις αὐτὸς ἔφησθα ἐννενοηκέναι

whereof none is fully perfect. But as to the King and the objects I have mentioned, they are of quite different quality. In the next place the soul inquires—Well then, what quality have they? But the cause of all the mischief, O son of Dionysius and Doris, lies in this very question, or rather in the travail which this question creates in the soul; and unless a man delivers himself from this he will never really attain the truth. You, however, declared to me in the garden, under the laurels, that you had formed this notion yourself and that it was a discovery of your own;