How does the prophecy of the three witches affect the actions of Macbeth?

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teachertaylor eNotes educator| Certified Educator

In The Tragedy of Macbeth, the three witches offer Macbeth premonitions on two occasions that cause Macbeth to tempt fate and act rashly in order to ensure that the prophecies come true.  When Macbeth and Banquo first meet the witches, they proclaim that Macbeth will become the Thane of Cawdor and then become King afterwards, but Macbeth has some doubt.  Soon after, he learns that Duncan has named him the Thane of Cawdor as a reward for his valiant service on the battlefield, and this news spurs Macbeth into believing that there is truth in the prophecy.  Rather than waiting to see how fate will lead to his becoming King, Macbeth is fueled by his own greed and ambition to make the prophecy happen quicker, so he plots to kill Duncan.  

Later in Act 4, Macbeth seeks out the witches to get another prophecy to confirm that he will remain King.  But this time, all that Macbeth reasons from the prophecy is that he needs to beware Macduff, so he plots to have Macduff and his family killed.  Macbeth does not consider that the other parts of the prophecy could be true, so he initially ignores them, feeling secure in his position as King.  Macbeth's greed and arrogance ultimately leads to his downfall.