The relationship between blindness and madness can also be seen in the abundant figurative language that links the two, often ironically.  When professing her love for her father, Goneril says her love for him is “dearer than eyesight” (1.1.56), and shortly afterwards, when Cordelia refuses to play this “love-game,” Lear says to her, “Hence and avoid my sight” (1.1.125). Kent then tells Lear after the King banishes him, “See better, Lear, and let me still remain / The true blank of thine eye” (1.1.160).  Responding to Kent, Lear swears by “Apollo,” known as an archer for being clear-sighted (161).  Lear goes mad because he is “blind”—he does not see, understand (as the other responder clearly explains); Gloucester loses his sight literally because of his friendship for and loyalty toward the mad Lear, acting as a kind of doppelganger to him.  Studying the pattern of language in relation to blindness and madness shows the structure of the double plot that shapes the themes of the play.

The madness of Lear and the confusion in his mind represents the chaos of Lear's kingdom and the hidden wisdom that Lear never learned as a king. England is in chaos because Lear misjudged the love and loyalty of his daughters. He then goes from being figuratively insane to being actually insane, and Lear learns humility when his madness strips him of his royal trappings, realizing he's been oblivious to the basic realities of mankind. It is only through his madness that he realizes how foolish he has been to betray Cordelia's love for him.

Gloucester's physical blindness symbolizes the figurative blindness of both Lear and Gloucester. Only when Gloucester goes blind and Lear goes mad do they realize how wrong they have been about their children. Both men have been blinded to the truth of their children's love and loyalty. They banish their loyal children and make the wicked children their heirs. 

Discuss how madness and blindness are an intertwined metaphor in King Lear.

In William Shakespeare’s King Lear, there is literal blindness and figurative blindness. In act 3, scene 7, Gloucester is physically blinded after Goneril orders Cornwall to “pluck out his eyes.” Gloucester could also be called figuratively blind. Here, blindness is a metaphor for Gloucester’s inability to perceive certain things, like the real identity of Poor Tom.

Unlike Gloucester, King Lear doesn't suffer physical blindness. As with Gloucester, he is beset by metaphorical blindness. Lear's failure to discern between the true love of Cordelia and the superficial love of Goneril and Regan sets in the motion the events that draw out a type of madness.

In Lear’s character, the blindness and madness metaphors entwine. Lear’s lack of perception leads him to divide his kingdom between Goneril and Regan. The ensuing strife compromises the “delicate” king further. The dislocation and disharmony exacerbate the “tempest” in his mind.

For madness to work as a metaphor, one should think about how Lear, for all his stormy behavior, isn’t genuinely mad. He's not literally insane or detached from reality; his conduct is a reflection of his unruly reality. His daughters are scheming against him and Gloucester’s son, Edgar, actually is pretending to be a homeless person. He’s not imagining these occurrences; they’re happening. It's as if Lear's madness is a metaphor for what's become of his kingdom. Of course, if Lear could have seen through his daughters’ sham displays of love, there would have been less to be mad about.