I need help with a debate on how Macbeth's ambition led to his downfall. I need points proving this as well as quotes from Macbeth.

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lsumner eNotes educator| Certified Educator

In the beginning, Macbeth appeared to be a content soldier. He was fierce on the battlefield. After he talked with the witches, he began changing. In Act 1, Scene 4, Macbeth begins plotting. Duncan makes Malcolm Prince of Cumberland. Macbeth states to himself that Malcolm is in his way and he will have to jump over Prince Malcolm or else fall on that step. He admits to himself that his desires and black and deep:

[Aside.] The Prince of Cumberland! I must fall down on that Step, or jump over it, For it’s in my way. Stars, put out your light! Don’t let anyone see my black and deep desires. It could happen in an instant Yet let that go, That thing that the eye is afraid to see when it is done.

Here, Macbeth admits to himself that his desires are black and deep. This happens right after he has been named Thane of Cawdor. Although he has been honored by Duncan, Macbeth is plotting to be king in Duncan's place.
Macbeth and his wife, Lady Macbeth, begin discussing plans to murder Duncan. Then, in Act 1, Scene 7, Macbeth changes his mind:
We will proceed no further in this business. He has recently honored me, and I now have the Golden opinions from all sorts of people, Which I want to enjoy for a bit longer, and Not cast them aside so soon.
Of course, Lady Macbeth challenges Macbeth's manhood and convinces him to proceed with murdering King Duncan.
Eventually, Lady Macbeth talks Macbeth into following through with the murder:
I’m convinced, and I commit Every part of my body to this terrible event. Let’s go and pass the time by pretending to be happy. False faces must hide what the false heart knows.