πεπεισμένως
From LSJ
Ἓν οἶδα, ὅτι οὐδὲν οἶδα → I know only one thing, that I know nothing | all I know is that I know nothing.
English (LSJ)
Adv.
A confidently, π. διεγγυώμενος D.L.9.71, cf. 4.56 ; from conviction, Ptol.Alm.2.6, Iamb.VP30.175 : f.l. in Str.15.1.24 (ἀπεφεισμένως cj. Mein.).