Plato, Laws 818a

πορεύεσθαι. ταῦτα δὲ σύμπαντα οὐχ ὡς ἀκριβείας ἐχόμενα δεῖ διαπονεῖν τοὺς πολλοὺς ἀλλά τινας ὀλίγους— οὓς δέ, προϊόντες ἐπὶ τῷ τέλει φράσομεν· οὕτω γὰρ πρέπον ἂν εἴη—τῷ πλήθει δέ, ὅσα αὐτῶν ἀναγκαῖα καί πως ὀρθότατα λέγεται μὴ ἐπίστασθαι μὲν τοῖς πολλοῖς αἰσχρόν, διʼ ἀκριβείας δὲ ζητεῖν πάντα οὔτε ῥᾴδιον οὔτε τὸ παράπαν δυνατόν. τὸ δὲ ἀναγκαῖον αὐτῶν οὐχ οἷόν τε ἀποβάλλειν,

All these sciences should not be studied with minute accuracy by the majority of pupils, but only by a select few—and who these are we shall say when we have come near the end,—since that will be the proper place: but for the bulk of the pupils, while it would be shameful for most of them not to understand all those parts of them that are most truly termed necessary, yet it is not easy nor even at all possible for every student to go into them minutely. The necessary part of them it is impossible to reject, and probably this is what was in the mind