Lear, the King of Britain, is a powerful and important man. But he's getting near retirement age. Lear thinks he can hand over the hard work of ruling the kingdom to his children and relax. He wants to enjoy the power of still being king without any of the responsibility.
That's Lear's first mistake, separating power and responsibility. His two eldest daughters are ready to run their own lives – and their own kingdoms. They resent Lear acting as if he is still in charge. Yet the King is shocked when his daughters assert their independence from him. After all, he gave them everything they have.
Lear's second mistake is to exile the people who love him the most. He chooses to stage a "love test" among his three daughters so he can give the biggest slice of the kingdom to the one who loves him most of all. When Cordelia refuses to participate, Lear is so angry that he orders her out of the kingdom. And when his advisor, Kent, warns him that this is a terrible idea, Lear throws him out, too.
So Lear has to deal with the power struggle his retirement sparked without two of the people who could have smoothed the transition. (Kent does come back disguised as Caius, a peasant, but this means he only has a peasant's power – enough to take care of Lear, but not enough to soothe his political worries.)
Lear realizes his stupidity soon enough. His retirement starts a series of conflicts that lead the whole country to civil war. Two of Lear's own children turn against him, and Lear goes mad and wanders around in a thunderstorm, shouting at the sky. In some sense, what happens to Lear is tragic. He ends up suffering in ways that elderly people are not supposed to. Worst of all, Lear is betrayed by his own flesh and blood, which you can read more about by going to our theme discussion of "Family."
Yet Lear also experiences an incredible transformation. Through adversity, Lear gains a new perspective on life. He rejects power and politics and decides that what really matters is being with the people he loves. For the first time, Lear also feels sympathy for the hardship undergone by others – especially the homeless that wander about the kingdom. His strange journey makes Lear a much better person.
But, who is Lear? This question is really the heart of the play. King Lear is, in a way, an experiment in identity loss. Most of the characters in the play go through an "Argh, who am I?" moment. The characters in the play keep asking the same question: What makes me who I am? And when one's identity is taken away, what's left? When everything else is stripped away – social position, family, memory – who are you? Lear himself loses the most: his kingship, his relationship to his daughters, and eventually, his mind.
When Lear looks at the shivering, half-naked body of Poor Tom the beggar and concludes that this is true humanity, without the perfumes and fancy clothes that society uses to hide what people are really like. "Thou art the thing itself," Lear tells Poor Tom. "Unaccommodated man is no more but such a poor, bare, forked animal as thou art" (3.4.10). Lear suggests that people are, at the core, no different – and certainly no better – than animals. As Lear mourns over Cordelia's body, he asks bitterly, "Why should a dog, a horse, a rat have life / and thou no breath at all?" (5.3). What's tragic about this line is that Lear has already provided an answer to his question. If people are really just "poor, bare, forked animals," there's nothing to separate Cordelia from a dog or a horse or a rat. She has no special claim on life. There's no reason that Cordelia should have breath while a dog, a horse or a rat doesn't. This is an unbearable thought, and, perhaps, this is why Lear dies of a broken heart.