Being asked what learning is the most necessary, he replied, "How to get rid of having anything to unlearn."
ἐρωτηθεὶς τί τῶν μαθημάτων ἀναγκαιότατον, “τὸ περιαιρεῖν,” ἔφη, “τὸ ἀπομανθάνειν.”
Original text (Ancient Greek)
Notes from Wikiquote
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