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σοι

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.

French (Bailly abrégé)

dat. enclit. de σύ.