In addition to questioning his manhood and his love for her, Lady Macbeth also bombards her husband with rhetorical questions loaded with innuendo and suggestion about his supposed feebleness. Her tone is thick with sarcasm when she, for instance, asks:
Art thou afeard
To be the same in thine own act and valour
As thou art in desire?
In this case, she wants to know whether Macbeth is afraid to exercise the same courage and willingness to perform the deeds that he so desperately feels he wants to commit. She immediately follows this up by asking him if he would have the crown but then, by not acting, see himself as a coward.
Wouldst thou have that
Which thou esteem'st the ornament of life,
And live a coward in thine own esteem,
She alludes to a popular adage in support of her question and wants to know whether Macbeth would rather choose not to take the risk than just do what he wants to. In the saying, the cat wants to eat fish but is afraid of getting into the water.
Letting 'I dare not' wait upon 'I would,'
Like the poor cat i' the adage?
Lady Macbeth later states that when Macbeth previously expressed his desire to kill Duncan, he was not limited by time nor place. He was prepared to create the ideal conditions to perform his dastardly deed. Now, however, when these ideal conditions do exist, it seems as if they have driven fear into him.
Nor time nor place
Did then adhere, and yet you would make both:
They have made themselves, and that their fitness now
Does unmake you.
She questions his integrity and suggests that he cannot keep a promise. She uses a most horrific example to illustrate her determination in maintaining a pledge. She states that she would remove her breastfeeding baby from her nipple and bash out its brains if that is what she has promised to do. She is urging Macbeth to do the same because he has made a vow to kill Duncan.
I have given suck, and know
How tender 'tis to love the babe that milks me:
I would, while it was smiling in my face,
Have pluck'd my nipple from his boneless gums,
And dash'd the brains out, had I so sworn as you
Have done to this.
Macbeth, though, is still not entirely convinced and expresses doubt by asking what would happen if they should fail. Lady Macbeth responds as follows:
But screw your courage to the sticking-place,
And we'll not fail.
Her allusion here could be military or musical and can refer either to the setting of a bowstring or the screwing of chords on a musical instrument. What she means is that Macbeth should be resolute and determined enough to go through with the murder. She will ensure the success of their devious endeavor.
Lady Macbeth describes how she will ply Duncan's two guards with wine and potions until they are in a drunken stupor. They will be so fast asleep during the murder that they won't see or remember anything afterward. The guards will then be held responsible for the killing.
At this point, Macbeth compliments his wife and seems willing to proceed. He suggests that they should use the sleeping guards' daggers to kill Duncan and then smear his blood on them. Duncan's sentinels will immediately be implicated in his death.
Lady Macbeth agrees that it is an excellent addition to their plan for there will be no doubt about the guards' guilt. For their part, she and her husband will put on such a great show of grief that no one will question their love and loyalty for the then slain Duncan.
Who dares receive it other,
As we shall make our griefs and clamour roar
Upon his death?
Macbeth is finally convinced and states:
I am settled, and bend up
Each corporal agent to this terrible feat.
He is finally prepared to commit his entire being to the execution of their foul plot.