'quantum wave-function' of every single subatomic particle in the cat. Having done this, you apply a mathematical rule known as Schrodinger's equation, which physicists tell us will predict the future state of the cat.70

However, no sensible physicist would attempt any such thing, because the wavefunction is far too complicated. The number of subatomic particles in a cat is enormous; even if you could measure their states precisely -which of course you can't do anyway -the universe does not contain a sheet of paper big enough to list all the numbers. So the calculation can't even get started, because in practical terms the present state of the cat is indescribable in the language of quantum wavefunctions. As for plugging the wavefunction into Schrodinger's equation, well, forget it.

Agreed, this is not a sensible way to model the behaviour of a cat. But it does make it clear that the usual physicists' rhetoric about quantum mechanics being 'fundamental' is at best true in a philosophical sense. It's not fundamental to our understanding of the cat, although it might be fundamental to the cat.

Despite these difficulties, cats generally manage to behave like cats, and in particular they discover their own futures by living them. Down on the philosophical level, again, this may be because the universe is a lot better at solving Schrodinger's equation than we are, and because it doesn't need a description of the quantum wavefunction of the cat: it's already got the cat, which is its own quantum wavefunction from this point of view.

Let's accept that, even though it's rather likely that the universe doesn't propagate a cat into its future by applying anything that corresponds to Schrodinger's equation. The equation is a human model, not the reality. But even if Schrodinger's equation is what the universe 'really' does -and more so if it's not -there's no way that we limited humans can follow the 'calculation' step by step. There are too many steps. What interests us about cats occurs on the system level: things like purring, catching mice, drinking milk, getting stuck in the catflap. Schrodinger's equation doesn't help us understand those phenomena.

When the logical chain that leads from an entity-level description of a complex system to system-level behaviour is far too complicated for any human being to follow it, that behaviour is said to be an emergent property of the complex system, or just to be 'emergent'. A cat drinking milk is an emergent property of Schrodinger's equation applied to the subatomic particles that make up the cat. And the milk, and the saucer ... and the kitchen floor, and ...

One way to predict the future is to cheat. This method has many advantages. It works. You can test it, so that makes it scientific. Lots of people will believe the evidence of their own eyes, unaware that eyes tell lies and you'll never catch a competent charlatan in the act of cheating.

The wizards got Shakespeare right, aside -at a late stage -from the minor matter of sex. When it comes to a baby's sex, the Grand Master of Foretelling the Future was 'Prince Monolulu'. He was a West African who wore very impressive tribal gear and haunted (in a very material sense) the markets in the East End of London in the 1950s. Prince Monolulu would accost pregnant women with the cry 'I will tell you the sex of your baby, money back guarantee!' Many ladies fell for this ploy, and paid a shilling, then about a fiftieth of one week's wages.

Level One of the trick is that random guesses would guarantee the Prince 50 per cent of the money, but he was much more cunning than that. He improved the scheme to Level Two by writing the prophecy on a note, putting it into an envelope, and getting the sucker to sign across the seal. When it turned out that the anticipated John was really Joan, or Joan was John, the few who bothered to return to reclaim their money found that, on opening their envelope, it contained a correct prediction. They didn't get their money back, because Prince Monolulu insisted that what was in the envelope was what he had originally told them; the sucker must have remembered it wrong. In reality, the envelope always contained the opposite prediction to the verbal one.

History is a complex system; its entities are people, its rules of interaction are the complicated ways in which human beings behave towards each other. We don't know enough sociology to write down effective rules at this entity level. But even if we did, the system-level phenomena, and the system-level rules that govern them, would almost certainly be emergent properties. So the rule that propagates the state of the entire system one step into the future is not something we can write down. It is an emergent dynamic.

When the system-level dynamic is emergent, then even the system itself does not 'know' where it is going. The only way to find out is to let the system run and see what happens. You have to allow the system to make up its own future as it goes along. In principle only one future is possible, but there is no short cut that lets you predict what will happen before the system itself gets there and we all find out. This behaviour is typical of complex systems with emergent dynamics. In particular, it is typical of human history and of biological evolution. And cats.

Biologists learned long ago not to trust evolutionary explanations in which the evolving organisms 'knew' what they were trying to achieve. Explanations like 'the elephant evolved a long trunk in order to suck up water without bending down'. The objectionable item here is not the reason why the elephant's trunk is long (though, of course, that can be debated): it is the phrase 'in order to'. This endows elephants with evolutionary prescience, and suggests (wrongly)

that they can somehow choose the direction in which they evolve. All this is obvious nonsense, so it's not sensible to have a theory that attributes purpose to elephant evolution.

Unfortunately, a dynamic looks remarkably like purpose. If elephant evolution follows a dynamic, then it looks as if the end result is predetermined, in which case the system 'knows' in advance what it ought to be doing. The individual elephants need not be conscious of their objective, but the system in some sense has to be. That would be a good argument against a dynamic description if the evolutionary dynamic for elephants was something we could prescribe ahead of time. However, if that dynamic is emergent, then the system itself, along with the elephants, can find out where it's headed only by going there and discovering where it gets to.

The same goes for history. Being able to put a name to a historical period only after it's happened looks remarkably like what you'd observe if there is a historical dynamic, but it is emergent.

This far into the discussion, it may seem that an emergent dynamic is no better than no dynamic at all. Our task now is to convince you that this is not so. The reason is that although an emergent dynamic cannot be deduced, in complete logical detail, from entity-level rules, it is still a dynamic. It has its own patterns and regularities, and it may be possible to work with those directly.

Exactly this is going on when a historian says something like 'Croesus the Unprepared was a rich but weak king who never maintained a sufficiently large army. It was therefore inevitable that his kingdom would be overrun by the neighbouring Pictogoths, and his treasury would be plundered'. This kind of story proposes a system-level rule, a historical pattern, which can sometimes be compelling. We can question how scientific such stories are, because it is always easy to be wise after the event. But in this case the story generalises; rich weak kings are asking to be invaded by mean, poor barbarians. And that's a prediction, wisdom before the event, and as such it is scientifically testable.71