αἱρεῖν
From LSJ
αὐτὸν κέκρουκας τὸν βατῆρα τοῦ λόγου → you have struck the very threshold of the argument, you have struck the most important and chiefmost point
Greek > English (Woodhouse Verbs Reversed)
(see also αἱρέω): capture, catch, condemn, convict, entrap, overtake, surprise, take, catch in the act, come upon suddenly, find guilty, get a person convicted, get into one's power, nip in the bud, secure a verdict against a person, take in the act