What is the role of madness in Hamlet and King Lear?
I would argue that madness in Hamlet and King Lear ironically allows characters to more clearly understand truth. In Hamlet, Hamlet's decision to feign madness (although, to be sure, it's unclear whether he actually is pretending; he might very well be mad) allows the prince to discretely investigate his uncle Claudius' crimes. After all, no one would expect a crazy adolescent to be capable of snooping around. Thus, though it might take him an agonizingly lengthy time, Hamlet is able to discern the truth of his father's murder and Claudius' treachery. Similarly, in King Lear, Lear only understands the true nature of his daughters' affection (or, in the case of Regan and Goneril, the lack thereof) once he goes mad and wanders the wilderness. Not only that, but Lear's madness also enables him to come to some pretty insightful (and depressing) conclusions regarding human nature, as he posits the possibility that humans are the victims of the uncaring, meaningless, and vindictive whims of the universe. Thus, both Hamlet and Lear's bouts of madness allow the characters to experience a special epiphany.