Plato, Letters 341b

Διονύσιος ἐδεῖτο· πολλὰ γὰρ αὐτὸς καὶ τὰ μέγιστα εἰδέναι τε καὶ ἱκανῶς ἔχειν προσεποιεῖτο διὰ τὰς ὑπὸ τῶν ἄλλων παρακοάς. ὕστερον δὲ καὶ ἀκούω γεγραφέναι αὐτὸν περὶ ὧν τότε ἤκουσε, συνθέντα ὡς αὑτοῦ τέχνην, οὐδὲν τῶν αὐτῶν ὧν ἀκούοι· οἶδα δὲ οὐδὲν τούτων. ἄλλους μέν τινας οἶδα γεγραφότας περὶ τῶν αὐτῶν τούτων, οἵτινες δέ, οὐδʼ αὐτοὶ αὑτούς. τοσόνδε γε μὴν περὶ πάντων ἔχω φράζειν τῶν γεγραφότων

for he claimed that he himself knew many of the most important doctrines and was sufficiently informed owing to the versions he had heard from his other teachers. And I am even told that later on he himself wrote a treatise on the subjects in which I then instructed him, composing it as though it were something of his own invention and quite different from what he had heard; but of all this I know nothing. I know indeed that certain others have written about these same subjects; but what manner of men they are not even themselves know. But thus much I can certainly declare