Plato, Meno 96d

οὐκ ἔοικεν, εἴπερ ὀρθῶς ἡμεῖς ἐσκέμμεθα. ὥστε καὶ θαυμάζω δή, ὦ Σώκρατες, πότερόν ποτε οὐδʼ εἰσὶν ἀγαθοὶ ἄνδρες, ἢ τίς ἂν εἴη τρόπος τῆς γενέσεως τῶν ἀγαθῶν γιγνομένων. κινδυνεύομεν, ὦ Μένων, ἐγώ τε καὶ σὺ φαῦλοί τινες εἶναι ἄνδρες, καὶ σέ τε Γοργίας οὐχ ἱκανῶς πεπαιδευκέναι καὶ ἐμὲ Πρόδικος. παντὸς μᾶλλον οὖν προσεκτέον τὸν νοῦν ἡμῖν αὐτοῖς, καὶ ζητητέον ὅστις ἡμᾶς ἑνί γέ τῳ τρόπῳ βελτίους

It seems likely, if our investigation is correct. And that makes me wonder, I must say, Socrates, whether perhaps there are no good men at all, or by what possible sort of process good people can come to exist? I fear, Meno, you and I are but poor creatures, and Gorgias has been as faulty an educator of you as Prodicus of me. So our first duty is to look to ourselves, and try to find somebody who will have some means or other of making us better.