What is the significance of sleep in Macbeth?
Sleep and sleeplessness in Macbeth represent peace of mind and the lack of it. As Macbeth spirals further into a cycle of guilt, he finds that sleep no longer comes easily to him. At the same time, he is keenly aware that perhaps sleep, which "knits up the ravell'd sleeve of care," is exactly what he needs to calm his nerves.
Macbeth "does murder sleep" in the sense that he has destroyed his own chances of resting easily forever, but this line also recalls the fact that he has also—with the help of Lady Macbeth—murdered King Duncan as he slept.
Duncan, the peacefully sleeping king, represented the rightful state of a king, of sound conscience and able to sleep deeply. In colluding in the murder of a sleeping king, the Macbeths have not only killed a man in no fit state to resist but have also symbolically destroyed the country's potential stability, as embodied by its peaceful king. Following Duncan's murder, there is no question that civil war must follow.
Hallucinations also play a significant part in Macbeth, never more indicative of a disturbed state of mind than when coupled with sleep. While Macbeth cannot sleep in act 5, scene 1 we see Lady Macbeth in arguably a worse state: even though she is asleep, sleepwalking and hallucinations mean that sleep can no longer perform its function of soothing the mind. The Doctor notes that it is "a great perturbation in nature, to receive at once the benefit of sleep, and do the effects of watching."
In fact, the viewer can see that Lady Macbeth is not receiving the benefit of sleep, as she performs fretful tasks such as the writing and sealing of letters, as well as rubs at her hands as if to wash out the stain of having murdered the king. After having observed Lady Macbeth bemoan the fact that "these hands will ne'er be clean," the doctor then says that "unnatural deeds do breed unnatural troubles / Infected minds to deaf pillows will discharge their secrets." This again connects sleep and disturbed sleep to a disturbed mind, indicating that the worst possible state is for sleep itself to be disturbed as guilt rises to the surface through the "infected" subconscious.
In Macbeth, sleep symbolizes clear conscience, peace, and innocence. Sleep is vital when it comes to good health and well-being of characters. Sleep is a significant symbol in the play because it tells us more about the inner state of characters. When Macbeth kills king Duncan, he is aware of the fact that he will never be able to enjoy the benefits of clear conscience and inner stability like he used to:
Methought I heard a voice cry 'Sleep no more!
Macbeth does murder sleep', the innocent sleep,
Sleep that knits up the ravell'd sleeve of care,
The death of each day's life, sore labour's bath,
Balm of hurt minds, great nature's second course,
Chief nourisher in life's feast...
He voluntarily deprives himself of the opportunity to lead a healthy and normal life. Now that he "does murder sleep," he will have to deal with hallucinations and visions which are the results of his guilt-ridden conscience.
Lady Macbeth's lack of good sleep and her episodes of sleepwalking and hallucinations suggest that when one gets involved in corruption and abnormality, one must suffer. She suffers because her peace of mind is taken away from her forever. In fact, she took it away when she manipulated her husband into murdering king Duncan.
So, sleep, as a symbol, serves as a reminder that both Macbeth and Lady Macbeth have irrevocably stepped into the realm of darkness and corruption. The play shows us that they soon lose their stability and peace, so their deaths are inevitable.