How does Shakespeare present the theme of guilt in Macbeth?

[Point 1]
In 'Macbeth', one of the ways in which guilt is presented is through the reoccurring image of blood. In Act 2 Scene 2, the blood on Macbeth’s hands after his murder of Duncan is both literal and a metaphor for his guilt: “Will all great Neptune’s ocean wash this blood / Clean from my hand? No, this my hand will rather / The multitudinous seas incarnadine”. Shakespeare juxtaposes blood with water, represented through “Neptune’s ocean”, to contrast the ideas of guilt and purity.

[Point 2]
He further emphasises this through the use of a rhetorical question and hyperbole, “the multitudinous seas”, to highlight the immorality of the murder and Macbeth’s regret and desperation, in that nothing will be able to cleanse him. In fact, the blood will turn the seas “incarnadine”, suggesting that the act of murder and the resulting blood will change nature, further symbolising Macbeth’s guilt. Macbeth’s desperate and regretful words are especially poignant considering his previous portrayal as a brave and fearless soldier.

[Point 3]
Similarly, Shakespeare uses the image of blood to highlight how guilt can erode sanity. In Act 5 Scene 1, Lady Macbeth appears fragile and broken by guilt as she attempts to wash imaginary blood from her hands while sleepwalking: “Out damned spot! Out I say! […] What need we fear who knows it, when none can call our power to account?”. Shakespeare juxtaposes Lady Macbeth’s power and fearlessness in earlier scenes - “Unsex me here!” - to highlight how guilt can erode a character to the extent that she becomes a shadow of her former self. The imperative and repetition of "Out" suggests that Lady Macbeth continues to attempt to grip on to power, but also highlights her desperation as she struggles to wash the blood from her hands, a parallel to Macbeth in Act 2 Scene 2.

[Point 4 - historical context]
This is significant in that Shakespeare highlights how unnatural the act of regicide is to his audience, since his patron, James I of England, had an assassination attempt made against him through the Gunpowder Plot of 1605.

[Conclusion]
Through the images of blood, Shakespeare presents guilt as a destabilising force that makes people desperate and powerless, and further emphasises the immorality of Duncan’s murder.