Discuss Macbeth as a penetrating psychological study of guilt. Give examples from the text to prove your point.

A challenging question indeed!

Macbeth, the shortest but darkest Shakespearean tragedy, is an implicit study of guilt resulted in penetration and psychosis. Fear, madness, death, and illusion or hallucination - all these are enough to prove this point.

Macbeth is a play of power-game, where the protagonist turns out to be a "butcher" driven by the force of ambition. Gluttony makes him terminate all the people whom he finds as threats to his way to the royal throne. Neither he hesitates to murder his heavenly master Duncan, the king of Scotland, nor he wavers to kill many other innocent humans. Lady Macbeth works as an instigator to push him ahead. But as it is said, crime does not spare even the criminal, so, both of them not only summon their disaster, but also bring about terrible misery for themselves. Macbeth is found many a times going through dilemma, fear and illusion because of his mental stress occurred as a consequence of his heinous deed. And then, Lady Macbeth's ambition leads herself to insomnia, insanity and death.

Guilt is the cause of marring peace in Macbeth. Macbeth's "vaulting ambition" kills his peace for good as well. In scene 2 of the second act, Macbeth, out of his guilt and stress, hears a voice crying "Sleep no more;/ Macbeth does murder sleep... Macbeth shall sleep no more"; and we find out that, sleep, which symbolises tranquility here, disappears from the lives of Macbeth and his wife in reality. Macbeth, while running after ambition, loses mental tranquility. Lady Macbeth, simultaneously, could no longer bear her guilt. It is because of the guilt she sees the hallucinatory blood in her hands which she wants to clean up, but can not. Her inability to wash the blood away symbolises her feeling that the crime she committed is also irremovable. Because of the sense of guilt, she loses her sanity and is compelled to commit suicide.

Guilt evokes different hallucinations and illusion in Macbeth. Macbeth hallucinates the ghost of Banquo in act 3, scene 4. This ghost is nothing but "the very painting of fear", an illusion created by his fear as a result of his guiltiness for murdering innocent Banquo. Besides, in the first scene of act 2, before going to murder Duncan, Macbeth sees an illusory dagger which stands for his internal fear and dilemma "proceeding from the heat-oppressed brain".

Besides, some speeches in the play like Macbeth's disability to say 'Amen' in 2.2 ('Amen' stuck in my throat), and Lady Macbeth's utterances "who would have thought the old man to have had so much blood in him", "No more o'that my lord, no more o'that", and "what's done, cannot be undone" in 5.1 expose the characters' feeling of guiltiness.

Different images like raven, bell, drum- all are indication of Macbeth's internal alarming fear and suppressing guilt.

Moreover, Lady Macbeth's death is the greatest proof of the terrible tormenting aspect of guilt. Her becoming mentally imbalanced is nothing but the consequence of her inner trauma.

Hopefully you have got some ideas and textual references through this answer.