Plato, Letters 340c

καὶ διʼ ὅσων πραγμάτων καὶ ὅσον πόνον ἔχει. ὁ γὰρ ἀκούσας, ἐὰν μὲν ὄντως ᾖ φιλόσοφος οἰκεῖός τε καὶ ἄξιος τοῦ πράγματος θεῖος ὤν, ὁδόν τε ἡγεῖται θαυμαστὴν ἀκηκοέναι συντατέον τε εἶναι νῦν καὶ οὐ βιωτὸν ἄλλως ποιοῦντι· μετὰ τοῦτο δὴ συντείνας αὐτός τε καὶ τὸν ἡγούμενον τὴν ὁδόν, οὐκ ἀνίησιν πρὶν ἂν ἢ τέλος ἐπιθῇ πᾶσιν, ἢ λάβῃ δύναμιν ὥστε αὐτὸς αὑτὸν χωρὶς τοῦ δείξοντος δυνατὸς εἶναι ποδηγεῖν.

and what its character, and how many preliminary subjects it entails and how much labor. For on hearing this, if the pupil be truly philosophic, in sympathy with the subject and worthy of it, because divinely gifted, he believes that he has been shown a marvellous pathway and that he must brace himself at once to follow it, and that life will not be worth living if he does otherwise. After this he braces both himself and him who is guiding him on the path, nor does he desist until either he has reached the goal of all his studies, or else has gained such power as to be capable of directing his own steps without the aid of the instructor. It is thus,