She desperately wants Macbeth to be King and she calls upon evil spirits to help Macbeth become King. Lady Macbeth obviously has a very different reaction to Macbeth's. She seems more bloodthirsty. Already we can see that she is very keen for Macbeth to fulfil this prophecy.
Lady Macbeth requests evil spirits to make her insensitive by blocking up all the pathways by which remorse can reach her heart, so that no natural feelings of conscience make her hesitate in her wicked plans, or come between her scheme and the carrying-out of this scheme:
Come, you spirits
That tend on mortal thoughts! Unsex me here,
And fill me from the crown to the toe top-full
Of direst cruelty; make thick my blood
She approaches Macbeth with her intent to kill King Duncan. Macbeth, although wanting the prophecy to come true, and become king, lacks the enthusiasm of his wife to commit the murder. Lady Macbeth urges her husband to act on his desires or he will think of himself as a coward. All of this goes straight into Macbeth’s mind, which is full of ideas of glory and honour.
King Duncan is invited to Macbeth’s castle, and it is there that he will be killed. Lady Macbeth wants Macbeth to act as he normally would, to appear to be happy with the King’s visit and to keep his evil plan in his mind.
‘Look like the innocent flower,
But be the serpent under it.’
Macbeth still has reservations about killing the king but Lady Macbeth has already prepared for the immoral act, and his mind begins to wander. Macbeth shows signs of insanity, as he follows a dagger up the stairs to King Duncan’s bedroom:
‘Is this a dagger which I see before me,
The handle toward my hand? Come, let me clutch thee.’
Evil takes over Macbeth. Soon King Duncan’s reign as King of Scotland ends. Macbeth murders Duncan under a cover of darkness.
There are three factors that lead to Macbeth murdering Duncan. The first factor is the witches. The witches place ideas into him that are already in his head. He has great ambition and may already want to be king so the witches therefore could not be totally responsible and just act as a catalyst. The witches change Macbeth’s outlook upon the crown, but are not directly involved while they do this. We can see it is quite easy to resist the witches as demonstrated by Banquo. This shows us he can control his thoughts, but Macbeth, however, has a weak point and cannot control his vaulting ambition.
The second factor is Lady Macbeth. Macbeth writes a letter to her telling her of the witches' prophecies. He writes this letter because he wants the crown and knows she will have to push him to get it. She drives him to the murder. She bullies him, emotionally blackmails him and knows he is morally sensitive. She starts to mock his bravery. When Macbeth is having doubts she says,
'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.’
She means that if he murders Duncan, he will be more of a man.
She answers every objection he comes up with. Before the murder Macbeth says:
'If we should fail-'
Lady Macbeth replies:
‘We fail?'
She is surprised by him thinking negatively because she believes there is no way that they will fail. However, Macbeth doubts their ability to cover up the truth. Lady Macbeth organises the fine details of the murder. The main part is when she goes to put the daggers back. Macbeth has returned from the murder scene and brought the daggers with him. She is annoyed with him because he is being careless and is too scared to go back after the murder. She goes and puts them back herself. Lady Macbeth plays a key role as she removes her feminine compassionate feelings so she can push Macbeth to carry out the murder. Despite this, she does show a moment of humanity, when saying she cannot murder Duncan, for the fact he resembles her father.
The third and final factor is Macbeth himself. He is the one who actually commits the murder. He is driven to the murder because of the thought of being king. It is the ambition in his mind that is the key. He knows that Duncan is a good man and has never done any wrong to him. He owes him gratitude for the honours he has given him. Macbeth is his kinsman, one of the elite and one of his generals. He is his subject, and should not murder his ruler if he has done nothing wrong. He is also the host and should prevent someone murdering Duncan and not do it himself. He also says:
'He hath honour'd me of late'
He is saying that he has received the title of Thane of Cawdor. He says that he should enjoy all the praise he receives and not throw it away. All this shows us that Macbeth is simply too intelligent to be a puppet being used. He is aware of all the consequences but still wants to be king. Moreover, he could have withdrawn at any point.
I feel the Macbeth’s ambition was the main reason why he killed Duncan. Macbeth committed the murder and let ambition rule him despite knowing the consequences. His ambition pushed his intent I believe the other two factors are less important. They only acted as catalysts for the murder.
