Plato, Meno 84c

ᾤετʼ ἂν εὖ λέγειν περὶ τοῦ διπλασίου χωρίου, ὡς δεῖ διπλασίαν τὴν γραμμὴν ἔχειν μήκει. ἔοικεν. οἴει οὖν ἂν αὐτὸν πρότερον ἐπιχειρῆσαι ζητεῖν ἢ μανθάνειν τοῦτο ὃ ᾤετο εἰδέναι οὐκ εἰδώς, πρὶν εἰς ἀπορίαν κατέπεσεν ἡγησάμενος μὴ εἰδέναι, καὶ ἐπόθησεν τὸ εἰδέναι; οὔ μοι δοκεῖ, ὦ Σώκρατες. ὤνητο ἄρα ναρκήσας; δοκεῖ μοι. σκέψαι δὴ ἐκ ταύτης τῆς ἀπορίας ὅτι καὶ ἀνευρήσει ζητῶν μετʼ ἐμοῦ, οὐδὲν ἀλλʼ ἢ ἐρωτῶντος ἐμοῦ καὶ οὐ διδάσκοντος·

that the double space must have a line of double the length for its side. It seems so. Now do you imagine he would have attempted to inquire or learn what he thought he knew, when he did not know it, until he had been reduced to the perplexity of realizing that he did not know, and had felt a craving to know? I think not, Socrates. Then the torpedo’s shock was of advantage to him? I think so. Now you should note how, as a result of this perplexity, he will go on and discover something by joint inquiry with me, while I merely ask questions