Plato, Letters 343d

τῶν ἐρωτώντων, δυναμένων δὲ τὰ τέτταρα διαρρίπτειν τε καὶ ἐλέγχειν· ἐν οἷς δʼ ἂν τὸ πέμπτον ἀποκρίνασθαι καὶ δηλοῦν ἀναγκάζωμεν, ὁ βουλόμενος τῶν δυναμένων ἀνατρέπειν κρατεῖ. καὶ ποιεῖ τὸν ἐξηγούμενον ἐν λόγοις ἢ γράμμασιν ἢ ἀποκρίσεσιν τοῖς πολλοῖς τῶν ἀκουόντων δοκεῖν μηδὲν γιγνώσκειν ὧν ἂν ἐπιχειρῇ γράφειν ἢ λέγειν, ἀγνοούντων ἐνίοτε ὡς οὐχ ἡ ψυχὴ τοῦ γράψαντος ἢ λέξαντος ἐλέγχεται, ἀλλʼ ἡ τῶν τεττάρων φύσις ἑκάστου, πεφυκυῖα

we being capable of analysing and convicting the Four. But in all cases where we compel a man to give the Fifth as his answer and to explain it, anyone who is able and willing to upset the argument gains the day, and makes the person who is expounding his view by speech or writing or answers appear to most of his hearers to be wholly ignorant of the subjects about which he is attempting to write or speak; for they are ignorant sometimes of the fact that it is not the soul of the writer or speaker that is being convicted but the nature of each of the Four, which is essentially defective. But it is the methodical study