"Fair is foul and foul is fair". Actually, there is no "exact" meaning for this quote. Shakespeare's words are seldom meant to be able to be explained "exactly". He leaves a lot of ambiguity and room for interpretation in much of what he writes. But in this case the ambiguity is deliberate. The three weird sisters always speak in riddles. Nothing they say has one clear meaning. "Fair is foul and foul is fair"... it does refer to the action of the play itself. Nothing is clear in the play. Things are seldom what they seem. The play is filled with magic and the supernatural. Do the witches just make predictions or are they the cause of Macbeth's actions? Who is the third murderer? How does Lady Macbeth die? Does Macbeth actually see Banquo's ghost or is it all in his mind? Things are seldom what they seem. Perhaps they are referring to Macbeth himself. "Fair is foul" - He starts the play as a strong, loyal, trustworthy thane and general, a cousin and favorite of King Duncan. Clearly "fair". Yet inside him there is ambition triggered by the witches and encouraged by Lady Macbeth; he becomes a murderer, over and over, in pursuit of his ambition and fear and guilt over his actions - very "foul" indeed. "Foul is fair"... more difficult maybe... is there anyone or anything in the play that seem evil or on the wrong side at the beginning that becomes an agent of good by the end? What about the witches? Are they fair or foul?