Like all of Shakespeare's tragedies, the action of Macbeth is based around the fatal flaw of the man who would otherwise be a hero. For Macbeth, his flaw is his ambition. He allows his ambition to drive him and this overcomes his reason. In doing so, he chooses the path of evil over the path of good. In the end though, he cannot live with his own choice and his good side becomes his underdoing. In this way, Macbeth is not only the story of a man choosing evil, but also the story of a man who cannot be driven to ignore his good side. This makes Macbeth a unique play because it shows both sides of the struggle between good and evil and makes it a human struggle. This major theme in the play is expressed in several ways. This will now be discussed in detail to show how Shakespeare expresses the theme.
The first important point of the play occurs when Macbeth meets with the three witches. As witches, this is a clear representation of evil. The idea of witchcraft also suggests that Macbeth is acting against what is natural. This is something Macbeth himself seems to know, since he does not accept what the witches are saying at first. However, the witches describe Macbeth as king. Since this is what Macbeth desires, it sparks his ambition. It is this ambition that drives Macbeth to consider what the witches are saying. In this way, his ambition is what pushes him toward evil. This is noted by Bradley (232), who describes how the witches do not actually cast any type of evil spell on Macbeth. Instead, they just appeal to the evil part of him and use his own capacity for evil against him. Considering that the witches represent evil, this also shows how people will naturally reject evil, but how they can also be attracted to evil if provided with the right motivation. Essentially, the witches know what Macbeth wants are able to use his desire against him. He then becomes driven by desire and his emotional needs overcome his rational side. This shows how his desires are a flaw able to be used by evil to push him towards evil. This is exactly what happens when Macbeth listens to the witches and then chooses to commit murder. This shows how good and evil exist within a person and struggle against each other.
Shakespeare also provides further insight on the struggle between good and evil by the metaphors he uses in the play. One of these is based around images of blood and battle. Blood and battle are linked to Macbeth throughout the play and used to represent his character. However, these same images shift from being a positive characteristic to being a negative one. At the start of the play, Macbeth's bravery in battle is described as one of his strengths. This includes the description of his sword smoking "with bloody execution" (Shakespeare I, ii). In this case, this reference to blood and battle is used to show how brave and capable Macbeth his. His ability to take action and spill blood is considered a sign of strength. Macbeth then takes a similar action when he kills Duncan. In this case, he also spills blood. However, rather than be a sign of his strength, it is now a sign of his weakness. This shows that an individual's actions are determined by the circumstances of them, as well as the action itself. The most important point is that Macbeth's action in both cases are based on his own personal qualities. On the battlefield, he is effective because his ambition drives him to swift action. In killing Duncan, it is his ambition that drives him. This shows how an individual's personal qualities can be either good or evil depending on how they are used. This suggests that good and evil are at battle within a person. In short, it is not Macbeth's ambition that makes him evil. Instead, it is that in a particular circumstances, his ambition overcomes this. This means that individuals cannot ever escape from evil completely. Instead, good and evil both exist within a person and are part of life. This is also suggested by the metaphor of blood, since blood represents both what gives a person life and what takes a person's life. This shows that evil is a necessary part of life, but also represents a danger.
Images of blood also continue throughout the play. When Macbeth takes the action to kill Duncan, he sees a bloody dagger and it lures him into killing Duncan. This suggests that blood has been spilled even before Macbeth actually commits the murder. This is partially true, since as soon as Macbeth decides to take the action, he has already allowed the evil part of himself to take over. This also suggests that Macbeth is operating in the same way as he operated in battle. As noted, in battle his actions were justified and even honored. As long as Macbeth sees killing Duncan as part of a battle, the warrior part of himself is allowed to take over and the action seems justified. With Macbeth driven by his ambition, the action is part of his battle to be king. This shows that Macbeth's action is not one where good has to be completely rejected. Instead, it is one where he is able to understand his actions in a way that changes how they appear to him. This means that his good part remains, but his evil side finds a way to justify his actions. In this way, he is still good but has pushed his goodness to the side. This shows the complexity that exists in determining actions as good and evil. As has been seen, actions that are evil in one circumstance are honored in another. This does not mean that Macbeth was right in taking this action, but it does not mean that he was able to justify it to himself.
The reference to blood then occurs again after Macbeth has killed Duncan and as his conscious begins to haunt in. At one point, he describes himself by saying, "I am in blood, stepped in so far that returning were as tedious as go o'er'" (Shakespeare III, iv). In this statement, he is not only saying that he is in blood, but is saying that he has stepped in too far to be able to return. This links back to the idea of evil as being part of his character. At the start of the play, there was evil in his character but it was contained and controlled. By this time in the play, he has allowed his evil side to rule and determine his actions. This creates a spiral effect, where he is drawn into his own evil. The suggestion is that once an individual allows evil to control them, the evil takes over and can no longer be contained. In Macbeth's case, it seemed that he initially ignored the evil of his actions by justifying his decision to kill Duncan. This allowed him to take the action without fully realizing the consequences. It is only after the event that he realizes what he has done and that he has gone too far. This shows the human struggle that is at the heart of the struggle between good and evil.
Another important concept in the play is the idea of Macbeth being a man. This is first seen when Lady Macbeth prompts Macbeth by telling him to be a man and take the throne of king. In Lady Macbeth's view, being a man means being king and having the ultimate power. Mary Ellen Lamb (530) notes that Lady Macbeth always criticizes Macbeth and spurs him into actions by attacking his masculinity. Macbeth is influenced by her views and this is part of what drives him. After all, Macbeth's ambition is to be king, which is the highest position that a man can reach. This makes this argument effective on him. However, there is also the issue raised of what really defines a man. Lady Macbeth says that a man is someone who will do anything to achieve what they want. However, other people would define a man in different ways. For some, a man might be someone who is king, but someone who has earned the position, not killed to achieve it. For others, a man might be someone who lives morally regardless of their position in society. The main point is that there is no one single definition of a man. What an individual has to do to be considered manly also depends on the situation. This shows that Macbeth is also struggling with a basic problem related to who he is. Clearly, he wants to be a man. The problem is that he does not know what being a man means. This allows him…