Lady Macbeth and the Tragic Flaw Are to Blame
"...Go pronounce his present death,/ And with his former title greet Macbeth." (Act 1, Scene 2, 64-65) Though the word "death" in this sentence refers to the former thane of Cawdor's demise, Shakespeare uses the clever trick of foreshadowing Macbeth's downfall by coupling the word "death" with the word "Macbeth" so early in the tragedy. The quote has another importance it introduces the ideas of treachery and personal gain from less-than-legitimate means, two characteristics Macbeth picks up on as the story advances. We are introduced to Macbeth as a hero, a slayer of the Norweyans, even "Bellona's bridegroom, lapped in proof" (Act 1, Scene 2, 54), but by the end of the play Macbeth is a ruthless killer of his own people and possibly cannibalistic*. The cause of Macbeth's downfall is due to both the unhealthy influence Lady Macbeth has on him and his tragic flaw.
In scene 7 of the first act, we see a hesitant, nervous Macbeth with a calm, bloodthirsty Lady Macbeth. Macbeth's doubts about killing the king reside in the fact that Duncan is a good king, an honest man and a relative of Macbeth. When Macbeth registers his doubts with the Lady, she scolds him for breaking a vow:
"...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 plucked my nipple from his boneless gums,
And dashed the brains out, had I so sworn as you
Have done to this."
(Act 1, Scene 7, 54-59)
We see what power and conviction Lady Macbeth has in her persuasion of Macbeth. But she is not all talk; as Macbeth forgets and fears to return the daggers to the murder scene, the Lady carries them and smears the king's grooms with blood. She then remarks, "My hands are of your color; but I shame/ To wear a heart so white" (Act 2, Scene 2, 64-65). During the famed banquet scene, the Lady again saves Macbeth by covering up his fear of Banquo's ghost. However by this time, her ruthlessness has taken root in Macbeth and to the end of the play, her mental state deteriorates from clear-headed to death, hitting the intermediary stages of remorse, insanity and sleepwalking.
In the third scene of the first act, Banquo** asks, "...have we eaten on the insane root that takes the reason prisoner?" in response to the witches' prophecies. ...