King Lear, Acts IV, V
Gloucester (pronounced Gloster) and his two sons mirror Lear and his three daughters. In Lear's case, the daugher, Cordelia, who seems to him unloving is the truly loving child; In Gloucester's case, the son, Edgar, who seems unloving (the son Gloucester believes is trying to kill him) is the truly loving child.
Lear: Goneril and Reagan pretend to love him but only want his lands and power
Gloucester: Edmund pretends to love him but only wants the lands to which his brother, the legitimate Edgar, is heir.
Both Lear and Gloucester are fooled by language: Lear is fooled by his two oldest daughters' verbal protestations of love; Gloucester is fooled by the written word, the letter Edmund gives him that is supposedly written by Edgar. Lear is fooled into thinking Goneril and Regan love him; Gloucester is fooled into thinking Edgar hates him and seeks his death. Ironically, Shakespeare, who earned his living writing and speaking words as playwright and player, seems to be suggesting that language can be dangerous when used by the unscrupulous.
Both men are punished: Lear loses his sanity; Gloucester loses his eyes.