Who is the Id, Ego, and Super-ego in Macbeth and why?
The id represents the unconscious portion of our brains that just wants to act on impulse and for pleasure; it is antisocial and can be aggressive, sexually or otherwise. Macbeth, then, seems most fitting for this particular part of ourselves. He reaches a point where, like the id, he does not consider the moral or social consequences of his behavior, and he simply acts in accordance with his own desires. For example, by the time he has Macduff's innocent wife and children brutally slain in their own home, he is no longer worrying about covering his tracks or making it seem as though he is innocent (as he at least attempted to do with the murder of Banquo, a short time earlier).
The superego is the conscious part of us that is most concerned with morality, with how our behavior makes us guilty or bad or shameful in the eyes of society and ourselves. This part of us is best represented by Malcolm, Duncan's older son and heir to the throne. When Macduff goes to England to collect Malcolm and bring him home, Malcolm tests his sincerity by saying how horrible he is when, in reality, Malcolm is the opposite of all the terrible things he claims. He eventually tells Macduff this, once he is convinced of Macduff's truthfulness. Malcolm seems to be ruled by his superego, making him a good embodiment of the concept.
The ego is the part of us that is most concerned with reality, with somehow reconciling the desires and impulses of the unconscious id with restrictions of the conscious superego, the part that mediates between the two. For these reasons, I agree with the other poster who identified Macduff as the play's ego because he balances between impulse and morality. At first, when he leaves for England, he only wants to bring Malcolm back to unseat Macbeth and put Duncan's rightful heir back on the throne, saving the country from the ruin Macbeth's reign has brought. After Macbeth kills his family, however, Macduff seems to allow his id more freedom and brutally kills Macbeth in order to satisfy his need for revenge. We might also perceive of Lady Macbeth as the play's ego: she tries to unleash her id prior to the murder of Duncan, but she finds that her conscience becomes too burdened by her transgressions, and her superego seems to gain power over her by the time the doctor sees her sleepwalking (and we learn of her guilt).
From Feud’s perspective Macbeth represents the Id, Macduff represents the Ego, and Lady Macbeth represents the Super-ego.
Lady Macbeth is often considered to represent the Super-ego. The Super-ego is Freud’s term for wanting to satisfy your own narcissistic tendencies. She seems to think that she should be queen, and therefore her husband should kill Duncan to get her what she wants—but she does not want to do it herself.
Had he not resembled
My father as he slept, I had done't. (Act 2, Scene 2, enotes etext p. 29)
Lady Macbeth giddily talks about cracking her baby’s head open after nursing it, but she can’t kill Duncan. She sets everything up, but then makes him do it!
Macbeth represents the Id from Feud’s perspective. The Id is the pleasure center of our consciousness, according to Feud. Macbeth always acts on impulse. He wants to be king because the witches told him he would be king, and his wife is egging him on. Macbeth is impressed with his wife’s ruthlessness.
Bring forth men-children only,
For thy undaunted mettle should compose
Nothing but males. (Act 1, Scene 7, p. 24)
Between the two forces of encouragement, Macbeth can’t say no. He does kill Duncan to get the throne, and then finds himself in an endless cycle of killing in order to keep it.
At stark contrast to Macbeth and his wife, Macduff represents the Ego. The Ego represents reality, and Macduff is always rooted in reality. He is honest and loyal, and while he is sensitive and compassionate he is also intelligent. When Macbeth drives Malcolm out, Macduff works hard to help him gather an army to retake the throne, even after Macbeth kills his entire family.
But, gentle heavens,
Cut short all intermission; front to front
Bring thou this fiend of Scotland and myself;(270)
Within my sword's length set him; if he 'scape,
Heaven forgive him too! (Act 4, Scene 3, p. 74)
Even though his family is dead and he wants to grieve, he realizes that he has to keep going. The only way to end Macbeth’s tyranny is to help Malcolm retake the throne.