Identify the sentiment Macbeth expresses at the end of Act Two, scene two in Shakespeare's Macbeth—what does this reveal about Macbeth's character, and why would it be necessary for Shakespeare to emphasize this point?
At the end of Act Two, scene two, of Shakespeare's Macbeth, Macbeth closes the scene (when he hears a knocking at the castle gate) by saying:
Wake Duncan with thy knocking! I would thou couldst! (93)
Very simply, Macbeth is saying, "Go ahead and wake Duncan with your knocking...I wish you could." He wishes that Duncan was not dead. I think Macbeth's first response is remorse. (Remember, this was not only his King he killed; Duncan was also his friend and his cousin.) Throughout the scene, once Macbeth returns to his bedroom with blood on his hands and the murder weapons in his hands, he has exhibited the signs of a man who is unraveling (mentally)—caused by the terrible crime he has committed. He obsesses at first that when the guards mumble "Amen" in their sleep, he cannot call down a blessing on himself as well.
Macbeth also seems to be hearing things—but I think it's impossible to know for sure whether they are supernatural occurrences or auditory illusions. He says...
Methought I heard a voice cry “Sleep no more!
Macbeth doth Murder sleep”... (46-47)
Then, when Lady Macbeth notes that he has brought evidence of their conspiracy and crime back with him, she orders him to take the daggers back and smear the drugged guards with blood to make them look guilty. Macbeth refuses, outright:
I'll go no more:
I am afraid to think what I have done;
Look on't again I dare not. (64-66)
This all just emphasizes Macbeth's original uncertainty about killing Duncan in Act One, scene seven. The last time he and his wife spoke, he had said that he wanted to wait before killing the King: Macbeth explained the he was still enjoying all the rewards that the King had showered him with for his part in the recent war. At that point, Lady Macbeth literally harassed him into agreeing, calling him names and insulting his manhood, his bravery. She knew exactly what she was doing—and he agreed to go ahead with the plan.
Macbeth's distress at the end of this scene shows that while he gave in to his wife's demands, his heart was not in it. I believe that Shakespeare emphasizes this so that the audience can see just how far Macbeth is willing to go to become and remain King, all because of his tragic flaw—his vaulting ambition. We also recognize a certain frailty in face of his wife's displeasure, for at the start of the play, they are deeply in love. (By the end, he is a tyrant, and she goes insane reliving their murderous acts.)
By seeing Macbeth this way in Act Two, scene two, we can gauge the change in the man as he arranges for the murders of his friend Banquo and the Macduff family, and his willingness to kill Young Siward (in the young man's first battle) at the end of the play. Macbeth has sold his soul to the "enemy" (the devil) by killing the King. He believes killing will get easier with time, and he seems to be correct. We are better able to see his absolute moral deterioration by the play's end. The only thing left to him is his valor—his bravery. In face of all else, he will not beg for his life, but dies in battle—the only honor left to him.