The majority of people have no understanding of the things with which they daily meet, nor, when instructed, do they have any right knowledge of them, although to themselves they seem to have.
οὐ γὰρ φρονέουσι τοιαῦτα [οἱ] πολλοί, ὁκόσοι ἐγκυρεῦσιν, οὐδὲ μαθόντες γινώσκουσιν, ἑωυτοῖσι δὲ δοκέουσι.
Original text (Ancient Greek)
Notes from Wikiquote
Fragment 5, as translated by G. W. T. Patrick