Macbeth's strong desire to become King drives him to murder Duncan, but that is not the only source of his evil. Lady Macbeth also wants Macbeth to become King and therefore she uses her evil desires to convince Macbeth that he must murder Duncan. Lady Macbeth just strengthens Macbeth's lust for power. Excessive ambition was Macbeth's only source of evil until Macbeth spoke with Lady Macbeth. She made Macbeth's desire for power even stronger and she pushed him to murder Duncan by calling him a coward and not a man if he did not do so. Macbeth's sources of evil are the prophecy, his lust for power, and his wife.
             The fact that the witches told Macbeth that he would become King made him more evil because he knew that he would be King one day. He used the prophecies to somewhat defend his reasons for killing Duncan. If Macbeth had never known about the prophecy of him becoming King and if his wife never knew, then they would not have murdered Duncan because they would never have had the idea that one day Macbeth would be King. Since Macbeth knows that he will one day have power, he wants it even sooner. Lady Macbeth just encourages Macbeth because she wants to have power too.
             When a person has a desire for power and is encouraged by others to take power away from somebody else, they start to desire it even more, which leads them to do evil things. Macbeth was not an evil person, but his excessive ambition to become King and the prophecies that the witches told him made him desire the power even more because he knew that one day he would have it. He was not sure if he was supposed to kill Duncan to become King or if it would just happen, but his desire for power and the words of his wife took over him and he killed Duncan. When evil takes over someone, it clouds their judgment and all they think about it getting what they want.
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