A statement that seems to contradict itself or common sense, but which, when thought through, reveals a truth.
In Macbeth
Fair is foul, and foul is fair: / Hover through the fog and filthy air.
The verse says that "the beautiful is rotten, and the rotten can be beautiful," and the swap of places between the two terms contradicts common sense: the spectator no longer knows what is good and what is evil, and the play begins in that doubt.
Act I: The Prophecy and the Temptation, The three witches, in chorus
Lesser than Macbeth, and greater. [...] Thou shalt get kings, though thou be none.
Act I: The Prophecy and the Temptation, The witches (the first and the third)
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