How does filial ingratitude leads to suffering in King Lear? In what way does this relate to his unjust decision?  

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thanatassa eNotes educator| Certified Educator

William Shakespeare's King Lear is a play that centers around themes of filial ingratitude. At the beginning of the play, Lear decides to divide his kingdom among his three daughters. Rather than following the advice of his advisers, he asks each daughter to declare her love for him. The evil sisters Regan and Goneril flatter the king outrageously, conniving to inherit his estate, but Cordelia, the honest daughter speaks simply and plainly. Lear foolishly divides his estate between the two evil sisters, assuming that out of gratitude they will care for him in his old age.

Instead, he discovers that they are mean-spirited and lacking in filial piety, gradually stripping him of his escort and privileges and leaving him to starve. Thus his sufferings are due to lack of filial piety but also to his unjust decision to spurn his truly loving daughter Cordelia in favor of her dishonest, flattering sisters. 

The subplot concerning Gloucester and Edmund is similar, with Gloucester first favoring the evil Edmund, his illegitimate son, who turns on him causing him to suffer only to be rescued by his spurned son Edgar. 

The theme of filial ingratitude is best expressed in the famous exclamation:

"How sharper than a serpent's tooth it is to have a thankless child!"