"What then does the god mean saying that I am the wisest (of men)?"
Liddle and Scottλέγω(B),
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III. say, speak, first in Hes.Th.27 (v. supr.11.2): fut. “λέξω” Emp.38.1, [...]
9. wish to say, mean, “οὔτοι γυναῖκας ἀλλὰ Γοργόνας λέγω” A.Eu.48; τί τοῦτο λέγει, πρὸ Πύλοιο; what does “πρὸ Πύλοιο” mean? Ar.Eq.1059, cf. 1021, 1375, Ec.989, Pl. Phd.60e: freq. in Platonic dialogue, πῶς λέγεις; how do you mean? in what sense do you say this? Ap.24e, al.; ἢ πῶς λέγομεν; or what do we mean to say? Grg.480b;
He thinks he knows something when he does not, whereas I, as I do not know anything, do not think (I know).
http://en.wikipedia.org/wiki/I_know_that_I_know_nothingin Apology, Plato relates that:[3]
[…] οὖτος μὲν οἴεταί τι εἰδέναι οὐκ εἰδώς, ἐγὼ δέ, ὥσπερ οὖν οὐκ οἶδα, οὐδὲ οἴμαιThe impreciseness of the paraphrase of this as I know that I know nothing stems from the fact that the author is not saying that he does not know anything but means instead that one cannot know anything with absolute certainty but can feel confident about certain things
– This man, on one hand, believes that he knows something, while not knowing [anything]. On the other hand, I – equally ignorant – do not believe [that I know anything].