Final answer:
Macbeth's evil side is associated with 'night and darkness' as seen through Shakespeare's use of dark imagery to symbolize his moral corruption and the concealment of his malevolent acts.
Step-by-step explanation:
In Shakespeare's Macbeth, the main character's evil side is most closely associated with night and darkness. This motif is evident throughout the play as Macbeth's moral descent coincides with the imagery of darkness, nightfall, and obscured vision, all of which symbolize deceit, mystery, and the supernatural. Passages such as Macbeth's hallucination that he cannot sleep (“Sleep no more! Macbeth does murder sleep”) and constant references to night and dark actions (“by the clock, 'tis day, And yet dark night strangles the travelling lamp”) serve as metaphors for his inner turmoil and the evil acts he commits. The darkness is not just a literal absence of light but also a representation of the absence of moral and ethical light within Macbeth's character, further reinforced by scenes set at night or in dimly lit locations, which often precede or follow his darkest deeds.