How is theme of betrayal and ambition represented in Macbeth?
Both Macbeth and Lady Macbeth shed light on the themes of betrayal and ambition. Macbeth betrays his friend, kinsman, and king, Duncan, as a result of his ambition. After the Weird Sisters tell him he will be king, he can think of little else and grows ruthless in pursuit of his new, ambitious goal. His wife adds fuel to this fire with her own monstrous ambition. Without her mocking and convincing, it seems unlikely Macbeth would have gone through with Duncan's murder (since he told her they would proceed no further with that business). Early on, however, Macbeth's ambition served him well in war, and when accompanied by his feelings of loyalty toward Duncan and Banquo, he made himself a hero. This change allows us to see how ambition, when unchecked by other virtues, can actually become a destructive vice.
Macbeth betrays Banquo, too. The sisters told Banquo he would father kings, and as a result of this prophecy and Banquo's own noble nature, he poses too much of a threat to Macbeth's security on the throne. Macbeth's ambition has grown; it is no longer enough to get the throne, but now he wants to keep it and pass it on to his own heirs (which he doesn't even have yet). Again, unchecked by loyalty, Macbeth's ambition leads him to betray his best friend.
Throughout the play Macbeth betrayal and ambition are two important that themes that often work together. Macbeth's ambition drives his betrayals. As soon as the witches predict that he will one day be the king, Macbeth's mind begins wandering with the possibilities. When Macbeth learns that Malcolm has been named the Prince of Cumberland, and thus will inherit his father's throne, his first thoughts are that he will have to move Malcolm out of his way.
Macbeth betrays his king and leader when he kills him. He also betrays his friendship when he hires murderers to kill Banquo and his son. These betrayals are vindicated in the eyes of Macbeth because he is doing what he think he must in order to ensure his power.