A statement that seems to contradict itself or common sense, but which, on reflection, reveals a truth.
In Othello
... I am not what I am.
The formula "I am not what I am" seems to deny itself, since it asserts an identity and undoes it in the same sentence. Iago confesses to Roderigo, in the form of a riddle, that what he shows outwardly is not what he carries within.
Act I: Venice, the Night Accusation and the Senate's Judgment, Iago