A key theme in William Shakespeare's Macbeth is ambition. Ambition finds its most significant expressions in the plays two main characters, Macbeth and Lady Macbeth. It is also in the lesser characters of Macduff and Malcolm. The catalyst for Macbeth's ambition is the witches interference in Macbeth's life and their prophesies which pervade his mind. Lady Macbeth, whose ambition is even stronger than Macbeth's, often persuades Macbeth to act on his ambitions. It is Macbeth's mission to gain power - his ambition - which ultimately leads to his tragic demise.
Macbeth was a brave, valiant warrior who was not naturally inclined to perform evil deeds, yet he desperately sought power and success. Before Duncan's murder, Macbeth questions and second-guesses his ambitious tendencies and actions. "We will proceed no further in this business/He hath honoured me of late, and I have brought/golden opinions from all sorts of people" (Act 1, Scene 7, 31 - 33).
Despite his anxiety he succumbs to his desires. After performing the evil deeds Macbeth was responsible for, Macbeth was not happy with what he has accomplished, "I am afraid to think what I have done/look on 't again I dare not" (Act 2, Scene 2, 55 - 56).
It is obvious that Macbeth begins the play as a noble man. He risks his own life to protect Scotland from Norway and the traitorous Thane of Cawdor. King Duncan acknowledged Macbeth's bravery by naming him the new Thane of Cawdor, "What he hath lost, noble Macbeth hath won," (Act 1, Scene 2, 67). One would think that such an accomplishment as Thane of Cawdor would satisfy Macbeth's ambition. However, this is not the case. He kills Duncan in his ambitious quest to gain even more power and later is consumed by paranoia and guilt.