Final answer:
The phrase 'Fair is foul and foul is fair' is a theme in the play Macbeth by William Shakespeare, representing the inversion of morality and deception.
Step-by-step explanation:
The phrase 'Fair is foul and foul is fair' is a line from the play Macbeth by William Shakespeare. It is a theme in the play and captures the idea of deception and the inversion of morality. Throughout the play, the characters and events challenge the audience's understanding of what is fair and what is foul.
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