After the witches tell Macbeth and Banquo their prophecies about fate in the first act, the whole play is encompassed by fate as a theme. One common question is asked about this: would Macbeth have killed Duncan if he were not told of his fate by the witches? As we read in the play, Macbeth tried to master his own fate by killing Duncan and then he tried to force fate to do what he wanted by trying to prevent some of the prophecies that could have led to his downfall. He became so obsessed with fate and trying to control it that he started to go crazy, and he did things that he would not have done if he had not been told the prophecies. Macbeth essentially destroyed himself by trying to master fate. The prophecies of the witches gave Macbeth the confidence to kill Duncan, which led to more killing and a war which, in the end, killed Macbeth.