This is an extremely interesting question to ponder. It is worth noting that in fact the play was re-written by Nahum Tate in 1681 to include a happy ending, where Lear is restored to his throne and Cordelia, too, does not die, but instead finds love with Edgar. This version of the play supplanted Shakespeare’s on the stage for many years. Tate’s revision had much to do with social and cultural tastes of the time in which it was written: the Restoration period which saw the re-establishment of the monarchy with Charles II after the execution of Charles I some years earlier which touched off the English Civil War. The idea of depicting the restoration of a deposed and cruelly-treated monarch had obvious attraction in the context of the politics of the time. But the extent of Shakespeare’s tragic ending has always provoked debate and disturbed not a few audiences.
In adding the tragic ending Shakespeare also went against his source material, the old legend of King Lear as re-told by Geoffrey of Monmouth and Holinshed among others. In these older versions, the outcome sees Lear restored to his throne. Shakespeare’s treatment of the story was therefore quite radical. Many critics agree that the overwhelming sense of the tragedy in King Lear goes beyond that of all his other tragic works. There are some observers, indeed, who feel that there are few, if any, bleaker endings to be found in all literature.
What would have been the effect if Shakespeare had retained a happy ending, as in preceding and subsequent versions of the tale? The most obvious one would be to considerably diminish the overall sense of despair that hangs heavy over the close. A few good men survive, and Edgar is left to pronounce a mournful epilogue, but there is nothing to abate the overall sense of suffering, the sense of utter waste caused by the unnatural severance of family bonds, bonds which should have been sacred. Evil has turned on itself and has been finally punished, but it has dragged the good down with it: Cordelia’s forgiveness, Lear’s final repentance, the loyalty of the Fool, of Edgar. All these seem buried alike under the overwhelming ruin. There seems to be no justice in this universe where such outstanding qualities are seen to achieve so little. In a happier ending of the tale, namely with the restoration of Lear and Cordelia, this sense of utter bleakness would naturally be removed. Good would be seen to triumph, and reward would come after suffering. Certainly a happy ending would also comfort many audiences.
However, a happy ending might also seem in danger of appearing somewhat trite, and rather unsuitable to the material overall. (Certainly Nahum Tate’s version attracted not a few charges of sentimentality.) The play, after all, is a searing exploration of a family breakdown which also impinges on the political state; it plumbs the depths of psychological torment, of madness, violence, and bitter struggle, raising fundamental questions about family, society, human relationships in general and the condition of humanity itself. To impose a happy ending on this darkest of material might, to employ a colloquial phrase, have appeared as something of a cop-out.
To make a final observation, the play, if it had a happy ending, would undoubtedly lose some of its potency – most of all, I think, in relation to the portrayal of Cordelia’s redemptive love and her reconciliation with her father. This is perhaps the most moving aspect of a profoundly affecting play. In this dark world, dominated by hate, fear, treachery and violence, their love and reconciliation shines all the brighter, as encapsulated in Lear’s poignant image: ‘we two alone will sing like birds i’th’ cage’. (V.iii.10). If things had come right for them after all, the image of their love – isolated yet strong – would not be so memorable.
King Lear and Gloucester had to die. Shakespeare was mainly interesting in dramatizing the painful truth that each generation is inevitably supplanted by the generation behind it. In Measure for Measure the Duke tells the condemned Claudio:
Friend hast thou none;
For thine own bowels, which do call thee sire,
The mere effusion of thy proper loins,
Do curse the gout, serpigo, and the rheum,
For ending thee no sooner.
That is to say, your own children are only waiting for you to die so that they can get their hands on your property. This is the case with Goneril and Regan and it is also the case with Edward the bastard son of Gloucester. All three of these younger characters actually manage to get possession of everything that belonged to their respective fathers, and the old men both ended up living in the open fields.
As spectators we may not like to see this happening to King Lear. We feel more pity for him than we do for Cordelia, because she is only a minor character who appears in the opening scene and then disappears until the end. But if we feel pity for Lear it is because Shakespeare intended for us to feel that pity. What happens to Lear is symbolic of what happens to every generation. In As You Like It, Jacques describes the seven ages of man, concluding with the last stage of all:
Last scene of all,
That ends this strange eventful history,
Is second childishness and mere oblivion;
Sans teeth, sans eyes, sans taste, sans everything. (2.7)
Lear has to die because his time is up. This chain of generations has been going on among us Homo sapiens for something like seven thousand generations, and a great many generations have passed away since the time of Lear. We may not like it, but we can't change it in fact, so we shouldn't wish to change it in fiction. A happy ending to King Lear would seem like an atrocity. Cordelia dies with her old father--but Cordelia only symbolizes one of the many precious things he loses when he goes into oblivion "sans everything."