In Act 1, Scene 3, Macbeth sees the three witches for the first time and they tell him the prophecy that sets the entire bloody play in action: “All hail Macbeth, that shalt be king hereafter” (act 1, scene 3, line 50). Despite the ambiguous nature of the play, Macbeth takes these words at face value and interprets them literally, including the second half of the prophecy:
1 WITCH: Lesser than Macbeth, and greater.
2 WITCH: Not so happy, yet much happier.
3 WITCH: Thou shalt get kings, though thou be none:
So all hail Macbeth, and Banquo (act 1, scene 3)
Macbeth hears this prophecy and immediately begins plotting in his mind as soon as he sees part of it has come true. However, as it is seen in Act 4, Scene 1, the witches’ prophecies are a sort of riddle, which true meanings are only discovered after the prophecies have come true. Though Macbeth seems to complete the prophecy by killing Duncan and becoming the king himself, he does so by taking fate into his own hands and forcing the prophecy forward despite being aware that things might fall into place if he sits idly by: “ If chance will have me king, why chance may / crown me, without my stir” (act 1, scene 3, line 146 - 148). My theory is that Macbeth was never meant to become king in the way that he does, and because he does take his own course of action he causes a sort of “disruption of reality” within the play.