Wikipedia: "In the play, the Three Witches represent darkness, chaos, and conflict, while their role is as agents and witnesses.[2] Their presence communicates treason and impending doom. During Shakespeare's day, witches were seen as worse than rebels, "the most notorious traytor and rebell that can be." They were not only political traitors, but spiritual traitors as well. Much of the confusion that springs from them comes from their ability to straddle the play's borders between reality and the supernatural. They are so deeply entrenched in both worlds that it is unclear whether they control fate, or whether they are merely its agents. They defy logic, not being subject to the rules of the real world.[7] The witches' lines in the first act: "Fair is foul, and foul is fair: Hover through the fog and filthy air" are often said to set the tone for the remainder of the play by establishing a sense of confusion. Indeed, the play is filled with situations in which evil is depicted as good, while good is rendered evil. The line "Double, double toil and trouble," (often sensationalized to a point that it loses meaning), communicates the witches' intent clearly: they seek to only trouble for the mortals around them.[8]
While the witches do not directly advise Macbeth to kill King Duncan, they use a subtle form of temptation when they inform Macbeth that he is destined to be king. By placing this thought in his mind, they effectively guide him on the path to his own destruction. This follows the pattern of temptation many believed the Devil used at the time of Shakespeare. First, they argued, a thought is put in a man's mind, then the person may either indulge in the thought or reject it. Macbeth indulges in it, while Banquo