This answer to this question is related to another important issue surrounding Macbeth, namely the extent to which Macbeth is responsible for his own actions. Many argue that he is ultimately the victim of sinister, supernatural forces beyond his control, and that these forces result in his downfall. Others point out that it was Lady Macbeth who set him on the path to destruction. But a persuasive case can also be made that it is Macbeth's own ambition that drives him to commit the evil deeds he does. He says himself that he has no reason to kill Duncan other than his own "vaulting ambition." Yet he does so, even if it requires some goading from his wife. Upset by the idea that Banquo's progeny might eventually take the throne, he has his old friend murdered, and only just missed killing Fleance. These actions created a cycle of destruction that eventually destroy Macbeth, his wife, and others. From the moment Macbeth meets the witches, he is aware of his "black and deep desires." It is precisely these desires that are Macbeth's ultimate undoing.