Plato, Meno 85c

οὔκ, ἀλλʼ ἑαυτοῦ. καὶ μὴν οὐκ ᾔδει γε, ὡς ἔφαμεν ὀλίγον πρότερον. ἀληθῆ λέγεις. ἐνῆσαν δέ γε αὐτῷ αὗται αἱ δόξαι· ἢ οὔ; ναί. τῷ οὐκ εἰδότι ἄρα περὶ ὧν ἂν μὴ εἰδῇ ἔνεισιν ἀληθεῖς δόξαι περὶ τούτων ὧν οὐκ οἶδε; φαίνεται. καὶ νῦν μέν γε αὐτῷ ὥσπερ ὄναρ ἄρτι ἀνακεκίνηνται αἱ δόξαι αὗται· εἰ δὲ αὐτόν τις ἀνερήσεται πολλάκις τὰ αὐτὰ ταῦτα καὶ πολλαχῇ, οἶσθʼ ὅτι τελευτῶν οὐδενὸς ἧττον ἀκριβῶς

No, they were all his own. But you see, he did not know, as we were saying a while since. That is true. Yet he had in him these opinions, had he not? Yes. So that he who does not know about any matters, whatever they be, may have true opinions on such matters, about which he knows nothing? Apparently. And at this moment those opinions have just been stirred up in him, like a dream; but if he were repeatedly asked these same questions in a variety of forms, you know he will have in the end as exact an understanding