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 try to calm his nerves. Macbeth "does murder sleep" in the sense that he has destroyed his...

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 try 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 Duncan, the king, 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 but 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, and 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, and indicates that the worst possible state is for sleep itself to be disturbed as guilt rises to the surface through the "infected" subconscious.