Shakespeare creates dramatic effect in Act I Scene 7 first by revealing the tension between Macbeth's ambition and his qualms about committing the murder and then by contrasting these doubts with Lady Macbeth's chilling, even wicked resolve. The scene begins with a soliloquy in which Macbeth's conscience is torn over the weighty deed he is contemplating. He acknowledges that he is unjustified in committing the murder, and fears divine and earthly retribution:
But in these cases
We still have judgement here, that we but teach
Bloody instructions, which being taught return
To plague the inventor. This even-handed justice
Commends the ingredients of our poison'd chalice
To our own lips.
When his wife enters the room, he announces that he will not, after all commit the murder. His conscience has won out in the first conflict of the act. Lady Macbeth's response creates another conflict, this time between his vacillating nature and her ambition. In a passage that must have been very provocative to Shakespeare's audiences, she challenges first his courage:
Art thou afeard
To be the same in thine own act and valor
As thou art in desire? Wouldst thou have that
Which thou esteem'st the ornament of life
And live a coward in thine own esteem,
Letting “I dare not” wait upon “I would”
Like the poor cat i’ the adage?
Then she challenges his masculinity and his honor:
When you durst do it, then you were a man;
And, to be more than what you were, you would
Be so much more the man... 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.
This shocking statement not only creates one of the tensest and most dramatic scenes in all of Shakespeare's dramas, it also raises the central question of whether Macbeth or his wife (or, the audience remembers, the witches) are responsible for the bloody events that transpire. In many ways, it is the most important scene in the play, because Macbeth emerges from these conflicts, quite literally, a murderer.