The Theme in the Work
Macbeth's ambition begins before it becomes a decision. In scene 3 of Act I, right after the witches' prophecy is partly confirmed by the title of Cawdor, he already speaks of a thought that welcomes a murder still in the realm of fantasy. In scene 4 of Act I, the naming of Malcolm as Prince of Cumberland shows him a step in his path, and he asks the stars to hide their light so that the light will not see his dark desires.
Macbeth:
Stars, hide your fires; / Let not light see my black and deep desires.
In scene 5 of Act I, Lady Macbeth describes her husband as ambitious but too full of the milk of human kindness to take the short cut, and she calls on spirits for herself. In scene 7 of Act I, he lists the reasons against the crime, and only ambition pushes him on; Lady Macbeth answers with the accusation of cowardice and the plan for the night, and he gives in.
Lady Macbeth:
Glamis thou art, and Cawdor, and shalt be / What thou art promised. Yet do I fear thy nature; / It is too full o' th' milk of human kindness / To catch the nearest way.
After the crime, ambition becomes everyone's topic. In scene 4 of Act II, Ross and an Old Man discuss the omens of the night, and Ross, thinking of the princes who fled, calls ambition prodigal, consuming the very source of its life, while Macduff reports that Macbeth was elected and left for Scone to be crowned.
In the play, ambition does not need to be invented by the witches: they give the title, and it is up to Macbeth and Lady Macbeth to commit the crime. What scene 4 of Act I adds to scene 3 of Act I is the obstacle, and what scene 7 of Act I adds to the obstacle is the shame of drawing back. Ross's line in scene 4 of Act II, said about the princes, fits Macbeth better and sums up what follows: ambition consumes what feeds it.
Where It Appears
- Scene 3 of Act I: Macbeth welcomes a thought of murder that is still fantastical right after the title of Cawdor.
- Scene 4 of Act I: Duncan names Malcolm Prince of Cumberland, and Macbeth, seeing in the title a step in his path, asks the stars to hide their light.
- Scene 5 of Act I: Lady Macbeth finds her husband too good for the short road to the crown and calls on spirits to empty him of pity.
- Scene 7 of Act I: Macbeth weighs the reasons against killing Duncan, his kinsman, king, and guest, and only ambition pushes him, until Lady Macbeth accuses him of cowardice and he is convinced.
- Scene 4 of Act II: Macduff reports that Macbeth was elected and left for Scone to be crowned, and in the scene ambition is called prodigal, for it consumes its own source of life.
Passages
Macbeth asks the stars to hide the light from his desires:
Stars, hide your fires; / Let not light see my black and deep desires.
Lady Macbeth describes her husband as ambitious but too good for the short cut:
Glamis thou art, and Cawdor, and shalt be / What thou art promised. Yet do I fear thy nature; / It is too full o' th' milk of human kindness / To catch the nearest way.
Ross, thinking of the princes who fled, sees in ambition what devours the source of its own life:
'Gainst nature still! / Thriftless ambition, that will ravin up / Thine own life's means!(II.4)