That the children of the poor under-achieve in later life, and thus remain poor themselves, is one of the enduring problems of society. Sociologists have studied and described it. Socialists have tried to abolish it by dictatorship and central planning. Liberals have preferred democracy and opportunity. But nobody has truly understood what causes it. Until now, perhaps.

The crucial breakthrough was made three years ago, when Martha Farah of the University of Pennsylvania showed that the working memories of children who have been raised in poverty have smaller capacities than those of middle-class children. Working memory is the ability to hold bits of information in the brain for current use - the digits of a phone number, for example. It is crucial for comprehending languages, for reading and for solving problems. Entry into the working memory is also a prerequisite for something to be learnt permanently as part of a declarative memory - the stuff a person knows explicitly, like the dates of famous battles, rather than what he knows implicitly, like how to ride a bicycle.

Mr. Bate explores a different Shakespeare,one Jonson described as "Soul of the Age!", the man who stood for and expressed the essence of his generation.

The effect, curiously, is not to distance the man, but to sharpen him. Approaching him locally, with connections to specific places and people, with certain books on his desk, and an eye out for particular political and diplomatic pitfalls - all this brings Shakespeare into focus. Not that any biographer has much hard fact to work on. As Mr Bate says, Shakespeare is elusive in every way: in his politics, religion, sexuality and in everything else that matters. The trick, it seems, is to pay very close attention to what evidence there is, not to take anything for granted and, well, to know a great deal about this world.