But they understood fiction perfectly.

What does this tell us? Not just that we can rewrite that scene with the boss in our minds. Not even that we can go and see her, and discuss what happened. Its most important implication is that the distinction between fiction and fact sits at the base of language, not at the pinnacle.

Verbs and nouns are the most rarefied of abstractions, not the original raw material. We do not acquire stories through language: we acquire language through stories.

In the heat of the night, magic moved on silent feet.

One horizon was red with the setting sun. This world went around a central star. The elves did not know this. If they had done, it would not have bothered them. They never bothered with detail of that kind. The universe had given rise to life in many strange places, but the elves were not interested in that, either.

This world had created lots of life, too. None of it had ever had what the elves considered to be potential. But this time ...

It had iron, too. The elves hated iron. But this time, the rewards were worth the risk. This time ...

One of them signalled. The prey was close at hand. And now they saw it, clustered in the trees around a clearing, dark blobs against the sunset.

The elves assembled. And then, at a pitch so strange that it entered the brain without the need to use the ears, they began to sing.

'Chmmmmph!' said Archchancellor Ridcully, as a heavy body landed on his back and clamped a hand over his mouth, forcing him back down into the long, dewy grass.

'Listen very carefully!' hissed a voice in his ear. 'When you were small, you had a one-eared toy rabbit called Mr Big Pram! On your sixth birthday your brother hit you on the head with a model boat! And when you were twelve ... do the words "jolly lolly" ring a bell?'

'Mmph!'

'Very well. I'm you. There's been one of those temporal things Mister Stibbons is always goin' on about. I'm taking my hand away now and we'll both quietly crawl away without the elves seeing us. Understand?'

'Mmp.'

'Good man.'

Elsewhere in the bushes the Dean whispered into his own ear: 'Under a secret floorboard in your study—'

Ponder whispered to himself: 'I'm sure we both agree that this should not really be happening ...'

In fact the only wizard who did not bother with concealment was Rincewind, who tapped himself on the shoulder and evinced no surprise at seeing himself. In his life he had seen far more unusual things than his own doppelganger.

'Oh, you,' he said.

"fraid so,' he said glumly.

'Was it you that turned up just now to tell me I should hold my breath?'

'Er ... possibly, but I think I've been superseded by me.'

'Oh. Has Ponder Stibbons being talking about quantum again?'

'You got it in one.'

'Another mess up?'

'More or less. It turns out stopping the elves is a really bad idea.'

'Typical. Do we both survive? There's not much room in the office, what with all the coal—'

'Ponder Stibbons says we may end up remembering everything, because of residual quantum infraction, but we'll sort of be the same person.'

'Any big teeth or sharp edges involved?'

'Not so far.'

'Could be worse, then, all things considered.'

In pairs, the wizards assembled as quietly as they could. Apart from Ridcully, who seemed to quite enjoy his own company, they tried not to look at their doppelgangers; it's quite embarrassing being in the company of someone who knows everything about you, even if that person is yourself.

A few feet away, with the suddenness of lightning, a pale circle appeared on the grass.

'Our transport is here, gentlemen,' said Ponder. One of the Deans, who was standing well apart from the other Dean, raised his hand.

'What happens to the ones of us that stay behind?' he said. 'It won't matter,' said Ponder Stibbons.

'They'll vanish the moment we do, and the ones of us who end up in the, er, other trouser leg of time will have the memories of both of us. I think that's right, isn't it?' 'Yes,' said Ponder Stibbons. 'A pretty good summation for the layman. So, gentlemen, are we ready? One of everyone, into the circle now, please.'

Only the Rincewinds did not move. They knew what to expect. 'Depressing, isn't it,' said one of them, watching the fighting. Both Deans had managed to knock one another out of the circle on the very first charge.

'Especially the way one of the Stibbonses has just laid out the other one with a left hook,' said the other Rincewind. 'An unusual skill in a man of his education.'

'Doesn't give you a lot of confidence, I admit. Toss a coin?' 'Yes, why not ...' They did so.

'Fair enough,' said the winner. 'Nice to have met me.' He picked his way delicately across the groaning bodies and the last couple of struggling wizards, sat down in the centre of the circle of light, and pulled his hat as far down over his head as possible.

A moment later he became, very briefly, a six-dimensional knot and became untied again on a wooden floor in a library.

'Well, that was relatively painful,' he murmured, and looked around. The Librarian was sitting on his stool. The wizards were around Rincewind, looking amazed and, in some cases, slightly bruised. Dr Dee was watching them with concern.

'Oh dear, I see it did not work,' he said, and sighed. 'It never works for me, either. I will instruct the servants to fetch some food.' When he'd gone, the wizards looked at one another. 'Did we go?' said the Lecturer in Recent Runes. 'Yes, but we came back at the same time,' said Ponder.

He rubbed his chin.

'I can remember everything,' said the Archchancellor. 'Amazin'! I was the one that got left behind and the one that—'

'Let's just not talk about it, shall we?' said the Dean, brushing his robe.

There was the sound of a muffled voice trying to make itself heard. The Librarian opened his paw.

'Attention please. Attention please,' said Hex.

Ponder took the sphere.

'We're listening.'

'Elves are approaching this property.'

'What, here? In broad daylight?' said Ridcully. 'On our damn world? While we're actually here?

The nerve!'

Rincewind looked out of the window on to the drive below.

'Is it me,' said the Dean, 'or has it got colder?'

A carriage was rolling up, with a couple of footmen trotting along beside it. It was a fine one, by the standards of the city. There were plumes on the horse. And everything about it was either black or silver.

'It's not just you,' said Rincewind, backing away from the window.

There were sounds at the front door. The wizards heard the distant voice of Dee, and then the creak of the stairs.

'Brethren,' he said, pushing open the door. 'There appears to be a visitor for you downstairs.' He gave them a worried smile. 'A lady.'