Personal desire can cause a man to do horrible things. Once he desires something such as power, he will likely go to any extent to achieve it. In the beginning of Macbeth, three witches predict futures for Banquo and Macbeth. When Macbeth discovers that he shall be thane of Cawdor he believes it to be a temptation. Soon after, when he is officially named thane of Cawdor, Macbeth realizes that the witches might be right. "...Two truths are told/As happy prologues to the swelling act/...This supernatural soliciting/Cannot be ill, cannot be good. If ill,/ Why hath is given me earnest of success/...If good, why do I yield to that suggestion." At this moment he is thinking about murdering Duncan but decides that he would be unable to do it. As the play moves forward his desire increases. He wants the power. He is not fine with Duncan being king anymore. He knows that in order to be king, Duncan is the only man in his way. With the murder of Duncan, Macbeth's desire overtakes his ability to live in reality.
Macbeth's attitude changes rapidly from the opening of the play to the death of Duncan. This happens because of