This is the turning point in the play. MacBeth realises that things are going to get very tough from now on. He fears for his own safety, but also worries about the immorality of his deeds. Killing Duncan was an act of selfishness. MacBeth was driven on by his ambition and by the persuasive powers of Lady MacBeth. Now he has had Banquo killed which was also selfish as MacBeth had it done as he worried about the implications for him if Banquo was allowed to live. MacBeth uses an extended metaphor comparing Banquo to a "grown serpent" and Fleance to a "worm" as he will breed and his children would be kings. This shows that MacBeth is becoming a sociopath
No sooner has MacBeth said this than the ghost of Banquo appears and sits in the place that has been reserved for MacBeth. MacBeth has not yet spotted the ghost and says how much he misses Banquo, which is very ironic as MacBeth is the one who has just had Banquo killed. Ross invites MacBeth to sit down and it is at this point that MacBeth sees Banquo's ghost, "the table's full". The others do not see the ghost and so Lennox points to the free seat and says to MacBeth, "Here is a place reserved, sir". MacBeth thinks initially that the ghost is a hoax set up by the others there, but then he realises that it is not. MacBeth shakes his fist at it. As the guests realise that there is something very wrong with MacBeth, Lady MacBeth lies to cover for her husband in the hope that no one will realise what is really the matter. She tells them that MacBeth always got like this from time to time and that there is nothing to worry about.
The king points at the apparition in horror and accuses his guests by asking, "Which of you have done this?” He then incriminates himself publicly by denying any wrongdoing: "Thou canst not say I did it.” The irony of the moment lies in the fact that none of the other guests, not even Lady MacBeth, can see the ghost; neither do any of them know about Banquo's murder. They can only assume he is referring to Duncan's recent execution, and at this point in time the common belief is that it was accomplished at the hand of Malcolm and Donaldbain.
Lady Macbeth, in her old, controlling manner, tries to save the situation for her husband and herself by explaining to the guests that Macbeth has had "fits" since his youth. She claims they are always momentary in nature and insists that the guests stay seated for dinner, even though the nobleman Ross has suggested they all leave. The irony is that by keeping the guests in the banquet hall, she is insuring her husband's ruin. His fit is not momentary, but a true sickness of his soul that he can no longer hide. The confident Lady Macbeth, unknowing of her husband's latest blood letting, is certain that through her typical chiding, she can bring her husband around. She begins by asking MacBeth; " Are you a man?” a question that always seems to get to him. She then reminds him that all of his visions, such as the air-born dagger in an earlier scene, have been his imagination run wild, and she tries to convince him that this one is the same. She summarizes her tirade by saying that his folly is making him unmanly and closes by saying, "Shame on you”, the image once again of a mother scolding her child. Later in the scene she pouts to Macbeth that he has spoiled the party, "displaced the mirth."
There are three possible reasons as to why MacBeth keeps seeing the ghost of Banquo. These visions could be caused by guilt; his evil nature or they could even be connected to the evilness of the witches and the fact that MacBeth cannot see the witches for what they really are. I think that these visions are most likely to be caused by his guilty conscience. This scene enhances my understanding of the play as a whole as this scene clearly shows in itself what the play is about, evil, the unnatural and ambition.
In Act 3, scene 4 MacBeth realises that he has done wrong and his conscience starts to get the better of him, hence the ghost of Banquo which he thinks he sees. This conscience and MacBeth trying to rid himself of evil influences such, as the witches and Lady MacBeth are central to the development of his character.
Banquo's ghost is also very symbolic. MacBeth had already "murdered" sleep when he murdered the sleeping Duncan, but until the appearance of Banquo's ghost, he had thought that the dead slept well for eternity, but now he has discovered for himself that they can rise again. This destroys MacBeth’s sense of security as he fears that he will not be able to hide from his treacherous deeds even when he is dead. Lady MacBeth tells him that he needs lots of sleep but MacBeth is now scared of it.
The supernatural element of the scene could also be a symbol of evil. The panic that MacBeth causes in the scene is similar to the disaster that his reign will turn out to be. MacBeth is not an evil person, but his surroundings and ambition can cause him to engage in evil acts. The many references to blood in the scene also further illustrate the evil atmosphere of the play.
In conclusion, I think that this scene is a key stage in the play due to the wide range of emotions expresses and the suggestion of evil, which compliments the story line as a whole. This scene dramatizes the fact that although MacBeth and Lady MacBeth have what they wanted, they cannot enjoy it.
