ἐλέγχειν
From LSJ
τους φίλους λόγων τέχναιν επαίδευσας → Using 2 artifices, you educated (taught) those who love rhetoric.
Greek > English (Woodhouse Verbs Reversed)
(see also ἐλέγχω): accuse, confute, convict, cross-question, disprove, examine, prove, question, test, bring home, call in question, cross examine, find guilty, ply with questions, bring a charge home to a person
Lexicon Thucydideum
arguere, to convict, prove, 1.131.2, [vulgo commonly αὺτῶν] 6.38.4, 6.86.1.