So ... we come full circle. Does an innovative idea change the world, or does a changing world generate the idea?

Yes.

It's complicity. Both of these things happen - not once, but over and over again, each progressively altering the other. Innovations redirect the course of human civilisation. New social directions encourage further innovation. The world of human ideas, and the world of things, recursively modify each other.

That is what happens to a planet when a species evolves that is not merely intelligent, but what we like to call extelligent. One that can store its cultural capital outside individual minds. Which lets that capital grow virtually without limit, and be accessible to almost anybody in any succeeding generation.

Extelligent species take new ideas and run with them. Before the ink was dry on Origin, biologists and laymen were already trying to test its ideas, shoot them down, push them further. If Darwin had written Ology, and if nobody else had written something like Origin, then Victorian extelligence would have been enfeebled, and perhaps the modern world would have taken longer to arrive.

But it was evolution time. Somebody would have written such a book, and soon. And in that alternat(iv)e world of if, he or she would have got the credit instead.

So it's only fair to give Darwin the credit in this world. Steam engine time notwithstanding.

LIES TO DARWIN

ARCHCHANCELLOR RIDCULLY'S MOUTH DROPPED OPEN.

`You mean killed?' he said.

+++ No +++, Hex wrote, +++ I mean vanished. Darwin disappears from Roundworld in 1850. This is a new development. That is to say, it has always happened, but has always happened only for the last two minutes +++

`I really hate time travel,' sighed the Dean.

`Kidnapped?' said Ponder, hurrying across the hall.

+++ Unknown. Phase space currently contains proto-histories in which he reappears after a fraction of one second and others where he never reappears at all. Clarity must be restored to this new node +++

`And you only tell us this now?' said the Dean.

+++ It has only just happened +++

`But,' the Dean attempted, `when you looked at this ... history before, this wasn't happening!'

+++ Correct. But that was then then, this is then now. Something has been changed. I surmise that this is as a result of our activities. And, having happened, it has always happened, from the point of view of an observer in Roundworld +++

`It's like a play, Dean,' said Ponder Stibbons. `The characters just see the act they're in. They don't see the scenery being shifted because that's not part of the play.'

+++ Despite being wrong in every important respect, that is a very good analogy +++ Hex wrote.

`Have you any idea where he is?' said Ridcully. +++ No +++

`Well, don't just sit there, man, find him!' Rincewind reappeared above the lawn, and rolled expertly when he hit the ground. Other wizards, nothing like so experienced at dealing with the vicissitudes of the world, lay about groaning or staggered around uncertainly.

`It wears off,' he said, as he stepped over them. `You might throw up a bit at first. Other symptoms of rapid cross-dimensional travel are short-term memory loss, ringing in the ears, constipation, diarrhoea, hot flushes, confusion, bewilderment, a morbid dread of feet, disorientation, nose bleeds, ear twinges, grumbling of the spleen, widgeons, and short-term memory loss.'

`I think I'd like to ... thing ... end of your life thing ... ' murmured a young wizard, crawling across the damp grass. Nearby, another wizard had pulled off his boots and was screaming at his toes.

Rincewind sighed and made a grab at an elderly wizard, who was staring around like a lost lamb. He was also soaking wet, having apparently also landed in the fountain.

He looked familiar. It was impossible to know all the wizards in UU, of course, but this one he had definitely seen before.

`Are you the Chair of Oblique Frogs?' he said.

The man blinked at him. `I ... don't know,' he said. `Am I?'

`Or the Professor of Revolvings?' said Rincewind. `I used to write down my name on a piece of paper before this sort of thing. That's always a help. You look a bit like the Professor of Revolvings.'

`Do I?' said the man.

This looked like a very bad case. `Let's find you your pointy hat and some cocoa, shall we? You'll soon feel-'

The Luggage landed with a thump, raised itself on its legs, and trotted away. The possible Professor of Revolvings stared at it.

`That? Oh, it's just the Luggage,' said Rincewind. The man didn't move. `Sapient pearwood, you know?' Rincewind carried on, watching him anxiously. `It's very clever wood. You can't get the very clever wood any more, not around here.'

`It moves about?' said the possible professor.

`Oh, yes. Everywhere,' said Rincewind.

`I know of no plant life that moves about!'

`Really? I wish I didn't,' said Rincewind, fervently, gripping the man a little tighter. `Come on, after a nice warm drink you'll-'

`I must examine it closely! I am aware, of course of the so-called Venus Fly-'

`Please don't!' Rincewind pleaded, pulling the man back. `You cannot botanise the Luggage!'

The bewildered man looked around with a desperation that was shading into anger.

`Who are you, sir? Where is this place? Why are all these people wearing pointy hats? Is this Oxford? What has happened to me!'

A chilly feeling was creeping over Rincewind. Quite probably, he alone of all the wizards had read Ponder's briefings as they arrived by surly porter; it paid to know what you might have to run away from. One had included a picture of a man who looked as if he was evolving all by himself, an effect caused by the riot of facial hair. This man was not that man. Not yet. But Rincewind could see that he would be.

`Um,' he said, `I think you should come and meet people.'

It seemed to the wizards that Mr Darwin took it all very well, after the initial and quite understandable screaming.

It helped that they told him quite a lot of lies. No one would like to be told that they came from a universe created quite by accident and, moreover, by the Dean. It could only cause bad feeling. If you were told you were meeting your maker, you'd want something better.

It was Ponder and Hex who solved that. Roundworld's history offered a lot of opportunities, after all.

`I didn't feel any lightning strike,' Darwin said, looking around the Uncommon Room.

`Ah, you wouldn't have done,' said Ponder. `The whole force of it threw you here.'

`Another world ... ' said Darwin. He looked at the wizards. `And you are ... magical practitioners ...'

`Do have a little more sherry,' said the Chair of Indefinite Studies. The sherry glass in Darwin's hand filled up again. `You create sherry?' he said, aghast.

`Oh no, that's done by grapes and sunshine and so on,' said Ridcully. `My colleague just moved it from the decanter over there. It's a simple trick.'

`We're all very good at it,' said the Dean cheerfully.

`Magic is basically just movin' stuff around,' said Ridcully, but Darwin was looking past him. The Librarian had just knuckled into the room, wearing the old green robe he wore for important occa sions or when he'd had a bath. He climbed into a chair and held up a glass; it filled instantly, and a banana dropped into it.

`That is Pongo pongo!' said Darwin, pointing a shaking finger. `An ape!'

`Well done that man!' said Ridcully. `You'd be amazed at how many people get that wrong! He's our Librarian. Very good at it, too. Now, Mr Darwin, there's a delicate matter we-'

`It's another vision, isn't it?' said Darwin. `It's my health, I know it. I have been working too hard.' He tapped the chair. `But this wood feels solid. This sherry is quite passable. But magic, I must tell you, does not exist!' Beside him, with a little gurgle, his glass refilled.