Expert Answers

An illustration of the letter 'A' in a speech bubbles

Macbeth is put on the path to murder when he encounters the witches, who greet him with three titles: "thane of Glamis," "thane of Cawdor" and "king hereafter." At this point in the play, he has not yet received news that he's been granted the thaneship of Cawdor. This would come soon after, when Ross and Angus arrive after the witches depart.

Prophecy is a critical theme in Macbeth. It is prophecy that sets in motion Macbeth's usurpation of Duncan, and Macbeth's belief in prophecy also drives the death of Banquo. Still later in the play, Macbeth is given more prophesies, this time regarding his demise.

Ultimately, though, it is Macbeth's own ambition and his desire for kingship (a desire which the Lady Macbeth shares) which is responsible for the murder of Duncan. For example, in Act 1 Scene 4, Macbeth refers to his "black and deep desires." Later, in Act 1 Scene 7, he refers to his "vaulting ambition, which o'erleaps itself."

In addition, we should also add the influence of Lady Macbeth, who is fully committed to killing Duncan and rebukes her husband when he expresses second thoughts about the murder.

Approved by eNotes Editorial Team
An illustration of the letter 'A' in a speech bubbles

Macbeth kills Duncan because the witches first give him the idea, his wife gives him the plan, and both (idea and plan) reinforce his blind ambition to be king.

Macbeth has doubts about killing Duncan: he is his kinsman (relative); he has honored Macbeth of late (given him the title Thane of Cawdor for valor in battle); plus, Macbeth is his host and subject.  Murder obviously violates the Thane-King bond ("comitatus").  Not to mention that Duncan is meek and virtuous.

But, against all this Macbeth says (Act I, scene vii):

I have no spur / To prick the sides of my intent, but only / Vaulting ambition, which o'er-leaps itself, / And falls on the other.

Also, Lady Macbeth challenges Macbeth's manhood and stirs up his bloody courage ("screw your courage to the sticking place").  She calls him a coward if he doesn't go through with her plan.  She says he is "too full the milk of human kindness" and admits that she would "dash out the brains" of her own child "had I sworn as you / Have done to this."  Such is her resolve.

After this, Macbeth agrees to kill Duncan, saying:

I am settled, and bend up Each corporal agent to this terrible feat.  / Away, and mock the time with fairest show: / False face must hide the false heart doth know.

In other words, Macbeth knows he must go against Time and put on an act to cover up his heinous intentions.

Approved by eNotes Editorial Team

We’ll help your grades soar

Start your 48-hour free trial and unlock all the summaries, Q&A, and analyses you need to get better grades now.

  • 30,000+ book summaries
  • 20% study tools discount
  • Ad-free content
  • PDF downloads
  • 300,000+ answers
  • 5-star customer support
Start your 48-Hour Free Trial