Fear, this motivates us to do many things no matter if they are right or wrong. In the play Macbeth it was fear that was the main motivating factor that influenced the outcome of the play. This can be proved by the subsequent murders that followed after Duncan's, why were these committed?
Because Macbeth was scared of being caught and having to pay for the wrongs he had done. Also look at Lady Macbeth, he constant washing of her hands, sleepwalking and other behavior like this. These acts are all done out of fear. The final piece of proof I offer is Macbeth's actions, they were all due to fear, not only of being caught but of the witches' prophecies, he was scared of them coming true and tried to stop them from happening. This whole play was inspired by fear and what it and do to a person.
To begin, we'll address Macbeth's subsequent murders, following Duncan's murder. For Macbeth, he's just killed the King of Scotland and blamed it on his son. It worked and he became King, however he remembered the witches' prophecies. They claimed that Macbeth would be King, but it would be Banquo's children that would follow after him. This made Macbeth very angry, he risked everything to become King and after him none of his family will follow.
Only for them; and mine eternal jewel
Given to the common enemy of man,
To make them kings, the seeds of Banquo kings!
[Act III, S I, L 72-75]
Here Macbeth realizes that if something is not done to Banquo, then his sons will become King. Macbeth can't have this because he's worried that his soul will go to hell for what he's already done. His fear become evident in this scene also, "But to...