simply
Ἓν οἶδα, ὅτι οὐδὲν οἶδα –> I know only one thing, that I know nothing | all I know is that I know nothing.
Diogenes Laertius, Lives of the Philosophers, Book 2 sec. 32.English > Greek (Woodhouse)
adverb
guilelessly: P. ἀδόλως, P. and V. ἁπλῶς.
absolutely: Ar. and P. ἀτεχνῶς, P. ὅλως.
nothing but: P. and V. οὐδὲν ἄλλο πλὴν (gen.).