clandestinely
From LSJ
ἔοικα γοῦν τούτου γε σμικρῷ τινι αὐτῷ τούτῳ σοφώτερος εἶναι, ὅτι ἃ μὴ οἶδα οὐδὲ οἴομαι εἰδέναι → I seem, then, in just this little thing to be wiser than this man at any rate, that what I do not know I do not think I know either