A great perturbation in nature, to receive at once the benefit of sleep, and do the effects of watching.
Act V, Scene 1
Context
The Doctor describes Lady Macbeth's sleepwalking condition after the Gentlewoman reports that Lady Macbeth performs complex actions while apparently asleep.
Analysis
The oxymoronic pairing—receiving sleep's 'benefit' while doing waking's 'effects'—is framed as a 'perturbation in nature,' placing Lady Macbeth's condition within the play's broader pattern of natural order being violated. The clinical, wondering tone (the Doctor is observing a medical curiosity) contrasts with the moral horror of what has caused this state, positioning readers between scientific detachment and ethical judgment.
Essay Tip
Support a thesis that Shakespeare consistently links the Macbeths' moral transgressions to breakdowns in natural categories—just as their regicide violated political nature, Lady Macbeth's sleepwalking violates the nature of sleep itself, suggesting guilt corrupts reality at every level.