even Shakespeare's own reflections on the act of writing, began to infuse each other". In the early 17th century, Shakespeare wrote the so-called "problem plays" Measure for Measure, Troilus and Cressida, and All's Well That Ends Well and a number of his best known tragedies. Many critics believe that Shakespeare's greatest tragedies represent the peak of his art. The titular hero of one of Shakespeare's greatest tragedies, Hamlet, has probably been discussed more than any other Shakespearean character, especially for his famous soliloquy which begins "To be or not to be; that is the question". Unlike the introverted Hamlet, whose fatal flaw is hesitation, the heroes of the tragedies that followed, Othello and King Lear, are undone by hasty errors of judgement. The plots of Shakespeare's tragedies often hinge on such fatal errors or flaws, which overturn order and destroy the hero and those he loves. In Othello, the villain Iago stokes Othello's sexual jealousy to the point where he murders the innocent wife who loves him. In King Lear, the old king commits the tragic error of giving up his powers, initiating the events which lead to the torture and blinding of the Earl of Gloucester and the murder of Lear's youngest daughter Cordelia. According to the critic Frank Kermode, "the play...offers neither its good characters nor its audience any relief from its cruelty". In Macbeth, the shortest and most compressed of Shakespeare's tragedies, uncontrollable ambition incites Macbeth and his wife, Lady Macbeth, to murder the rightful king and usurp the throne until their own guilt destroys them in turn. In this play, Shakespeare adds a supernatural element to the tragic structure. His last major tragedies, Antony and Cleopatra and Coriolanus, contain some of Shakespeare's finest poetry and were considered his most successful tragedies by the poet and critic T. S. Eliot. In his final period, Shakespeare turned to romance or tragicomedy and completed three more major plays: Cymbeline, The Winter's Tale, and The Tempest, as well as the collaboration, Pericles, Prince of Tyre. Less bleak than the tragedies, these four plays are graver in tone than the comedies of the 1590s, but they end with reconciliation and the forgiveness of potentially tragic errors. Some commentators have seen this change in mood as evidence of a more serene view of life on Shakespeare's part, but it may merely reflect the theatrical fashion of the day. Shakespeare collaborated on two