`I'm afraid it is looming, sir, yes.'

Ridcully stood up, gathering his robes about him. `Ah. I think I heard the gong for dinner, gentlemen. Just as well, really.'

The moon rose. At midnight, Ponder Stibbons read what Hex had written, wandered across the dewy lawn to the Library, woke the Librarian, and asked for a copy of a book called The Origin of Species.

Two hours later he went back, woke the Librarian again, and asked for Theology of Species. As he left with it, he heard the door being locked behind him.

Later still, he fell asleep with his face in a cold pizza and both books open on his desk, dripping with bookmarks and stray pieces of anchovy.

Beside him, Hex's writing table whirred. Twenty quill pens flashed back and forth and gyrated on spring-loaded arms, making the table look like several giant spiders on their backs. And, every minute, a page dropped onto the pile that was forming on the floor ...

Ponder dreamed fitfully of dinosaurs trying to fly. They always splashed when they reached the bottom of the cliff.

He woke up at half past eight, read the accumulated papers, and voided a small scream.

All right, all right, he thought. There is no actual hurry, as such. We can change it back any time we like. That's what time travel means.

But although the brain can think that, the panic gland never believes it. He snatched up the books and as many notes as he could carry and hurried out. We have heard the chimes of midnight, the saying goes. The wizards had not only heard them but also the ones at one, two and three a.m. They certainly weren't interested in hearing anything at half past eight, however. The only occupant of the tables in the Great Hall was Archchancellor Ridcully, who liked an unhealthy breakfast after his early morning run. He was alone at the trestle tables in the big hall.

`I've found it!' Ponder announced, with a certain nervous triumph, and dropped the two books in front of the astonished wizard.

`Found what?' said Ridcully. `And mind where you're putting stuff, man! You nearly had the bacon dish over!

'I have put my finger,' Ponder declared, `on the precise split in the Trousers of Time!'

`Good man!' said Ridcully, reaching for the flagon of brown sauce. `Tell me about it after breakfast, will you?'

`It's a book, sir! Two books in fact! He wrote the wrong one! Look!'

Ridcully sighed. Against the enthusiasm of wizards there was no defence. He narrowed his eyes and read the title of the book Ponder Stibbons was holding:

`Theology of Species. And?'

`Archchancellor, it was written by a Charles Darwin, and caused rather a row when it was published, since it purported to explain the mechanism of evolution in a manner which upset some widely held beliefs. Vested interests railed against it, but it prevailed and had a significant effect on history. Er ... the wrong one.'

`Why? What is it about?' said Ridcully, carefully taking the top off a boiled egg.

`I've only glanced at it, Archchancellor, but it appears to describe the process of evolution as one of permanent involvement by an omnipotent deity.'

`And?' Ridcully selected a piece of toast and began to cut it into soldiers.

`That's not how it works on Roundworld, sir,' said Ponder, patiently.

`That's how it does here, more or less. There's a god who sees to it.

`Yes, sir. But, as I am sure you will remember,' said Ponder, using the words in the sense of `as I know you have forgotten', `we have not found any traces of Deitium on Roundworld.'

`Well, all right,' the Archchancellor conceded. `But I don't see why the man shouldn't have written it, even so. Good solid book, by the look of it. Took some thinkin' about, I'll be bound.'

`Yes, sir,' said Ponder. `But the book he should have written ...' he thumped another volume onto the breakfast table, `... was this.'

Ridcully picked it up. It had a much more colourful cover than `Theology', and the title: Darwin Revisited THE ORIGIN OF SPECIES

by The Rev. Richard Dawkins

`Sir, I think I can prove that because Darwin wrote the wrong book the world took a different leg of the Trousers of Time, and humanity didn't leave the planet before the big freeze,' said Ponder, standing back.

`Why did he do that, then?' said Ridcully, mystified.

`I don't know, sir. All I know is that, until a few days ago, this Charles Darwin wrote a book that said that evolution all worked naturally, without a god. Now it turns out that he didn't. Instead, he wrote a book that said it worked because a god was involved at every stage.'

`And this other fella, Dawkins?'

`He said Darwin had pretty much got it right except the god part. You didn't need one, he said.'

`Didn't need a god? But it says here he's a priest of some sort!'

`Er ... sort of, sir. In the ... history where Charles Darwin wrote Theology of Species, it had become more or less compulsory to take holy orders in order to attend university. Dawkins said evolution happened all by itself.'

He shut his eyes. Ridcully alone was a much better audience than the senior faculty, who'd taken cross-purposes to the status of a fine art, but his Archchancellor was a practical, sensible man and therefore found Roundworld difficult. It wasn't a sensible place.

`You've foxed me there. How can it just happen?' said Ridcully. `It makes no sense if there isn't someone who knows what's going on. There's got to be a reason.'

`Quite so, sir. But this is Roundworld,' said Ponder. `Remember? 'But surely this other feller, Dawkins, made it all right again?'

Ridcully floundered. `You did say it was the right book.'

`But at the wrong time. It was too late, sir. He didn't write his book until more than a hundred years later. It caused a huge row-'

`An ungodly one, I suspect?' said Ridcully cheerfully, dipping the toast in the egg.

'Haha, sir, yes. But it was still too late. Humanity was well on the road to extinction.'

Ridcully picked up Theology and turned it over in his hands, getting butter on it.

`Seems innocent enough,' he said. `Gods making it all happen ...

well, that's common sense.' He held up a hand. `I know, I know!

This is Roundworld, I know. But where there's something as com plicated as a watch, you know there must be a watchmaker.' `That's what the Darwin who wrote the Theology book said, sir, except that he stated that the watchmaker remained part of the watch,' said Ponder.

'Oilin' it, and so forth?' said Ridcully, cheerfully. `Sort of, sir. Metaphorically.'

`Hah!' said Ridcully. `No wonder there was a row. Priests don't like that sort of thing. They always squirm when things get mystical.' `Oh, the priests? They loved it,' said Ponder. `What? I thought you said vested interests were against it!'

`Yes, Sir. I meant the philosophers and scientists,' said Ponder Stibbons. `The technomancers. But they lost.'