Unfortunately, it does reduce the scope for asking interesting questions. Most of them have already been answered. Certainty rules. Mustrum Ridcully is not the kind of person who would tolerate an Uncertainty Principle, after all.
Back in Roundworld, there is perhaps one point worth making.
Just suppose there is nothing else. Arguments about intelligent life on other worlds have always been highly biased by the desires of those doing the arguing that there should be intelligent life on other worlds, and we three are among them. But the argument is a house of cards with no card on the bottom. We know of life on one world. Everything else is guesswork and naked statistics. Life may be so common through the universe that even the atmosphere of Jupiter is alive with Jovian gasbags and every cometary nucleus is home to colonies of microscopic blobuies. Or there may be nothing alive at all, anywhere else but here.
Perhaps intelligent life arose before humanity, and perhaps it will again when humanity's span has become a rather complex layer in the strata. We can't tell. Time does not simply, as the hymn says, bear all its sons away, it can easily see the disappearance of the entire continent on which they stood.
In short, in a universe a billion Grandfathers long and a trillion Grandfathers wide, there may be just a few hundred thousand years on one planet where a species worried about something other than sex, survival, and the next meal.
This is our Discworld. In its little cup of spacetime, humanity has invented gods, philosophies, ethical systems, politics, an unfeasible number of ice-cream flavours and even more esoteric things like 'natural justice' and 'boredom'. Should it matter to us if tigers are made extinct and the last orangutan dies in a zoo? After all, blind forces have repeatedly erased species that were probably more beautiful and worthy.
But we feel it does matter, because humans invented the concept of things 'mattering'. We feel we ought to be brighter than a mile of incandescent rock and a continent-sized glacier. Humans seem to have created, independently, in many pkces and at various times, a Make-a-Real-Human-Being Kit, which begins with prohibitions about killing and theft and incest and is now groping towards our responsibilities to a natural world in which, despite its ability to hurt us mightily, we nevertheless have a godlike power.
We advance arguments about saving rainforests because 'there may be undiscovered cancer cures in there', but this is because extelligence wants to save rainforests and the cancer-cure argument might convince the bean-counters and the fearful. It might have a real basis in fact, too, but the real reason is that we feel that a world with tigers and orangutans and rainforests and even small unobtrusive snails in it is a more healthy and interesting world for humans (and, of course, the tigers and orangutans and snails) and that a world without them would be dangerous territory. In other words, trusting the instincts that up until now have generally seen us through, we think that Tigers Are Nice (or, at least, Tigers Are Nice In Moderation And At A Safe Distance).
It's a circular argument, but in our little round human world we've managed to live on circular arguments for millennia. And who else is going to argue with us?
AS ABOVE, SO BELOW
RINCEWIND WALKED VERY GINGERLY towards his office, the globe of the project held carefully in his hands.
He would have expected an entire universe to be heavier, but this one seemed on the light side. It was probably all that space.
The Archchancellor had explained at length to him that although he would be called the Egregious Professor of Cruel and Unusual Geography, this was only because that was cheaper than repainting the title on the door. He was not entitled to wages, or to teach, or express any opinions on anything, or order anyone around, or wear any special robes, or publish anything. But he could turn up for meals, provided he ate quietly.
To Rincewind, it sounded like heaven.
The Bursar appeared right in front of him. One moment there was an empty corridor, the next moment there was a bemused wizard.
They collided. The sphere went up in the air, turning gently.
Rincewind rebounded from the Bursar, looked up at the ball curving through the air, flung himself forward and down with rib-scraping force and caught it a few inches from the stone floor.
'Rincewind! Don't tell him who he is!'
Rincewind rolled over, clasping the little universe, and looked back along the passage. Ridcully and the other wizards were advancing slowly and cautiously. Ponder Stibbons was waving a spoonful of jelly invitingly.
Rincewind glanced up the Bursar, who was looking perplexed.
'But he's the Bursar, isn't he?' he said.
The Bursar smiled, looked puzzled for a moment, and vanished with a 'pop'.
'Seven seconds!' shouted Ponder, dropping the spoon and pulling out a notebook. 'That'll put him in ... yes, the laundry room!'
The wizards hurried off, except for the Senior Wrangler, who was rolling a cigarette.
'What happened to the Bursar?' said Rincewind, getting to his feet.
'Oh, young Stibbons reckons he's caught Uncertainty,' said the Senior Wrangler, licking the paper. 'As soon as his body remembers what it's called it forgets where it's supposed to be.' He stuck the bent and wretched cylinder in his mouth and fumbled for his matches. 'Just another day at Unseen University, really.'
He wandered off, coughing.
Rincewind carried the sphere though the maze of dank passages and into his office, where he cleared a space for it on a shelf.
The ice age had cleared up. He wondered what was happening down there, what gastropod or mammal or lizard was even now winding up its elastic ready to propel itself towards the crown of the world. Soon, without a doubt, some creature would suddenly develop an unnecessarily large brain and be forced to do things with it. And it'd look around and probably declare how marvellous it was that the universe had been built to bring forward the inevitable development of creature-kind.
Boy, was it in for a shock ...
'Okay, you can come out,' he said. 'They've lost interest.'
The Librarian was hiding behind a chair. The orangutan took university discipline seriously, even though he was capable of clapping someone on both ears and forcing his brain down his nose.
'They're busy trying to catch the Bursar right now,' said Rincewind. 'Anyway, I'm sure it couldn't have been the apes. No offence, but they didn't look the right sort to me.'
'Ook!'
'It was probably something out of the sea somewhere. I'm sure we didn't see most of what was going on.'
Rincewind huffed on the surface of the globe, and polished it with his sleeve. 'What's recursion?' he said.
The Librarian gave a very expansive shrug.
'It looks okay to me,' said Rincewind. 'I wondered if it was some sort of disease ...'
He slapped the Librarian on the back, raising a cloud of dust. 'Come on, let's go and help them hunt ...'
The door shut. Their footsteps died away.
The world spun in its little universe, about a foot across on the outside, infinitely large on the inside.
Behind it, stars floated away in the blackness. Here and there they congregated in great swirling masses, spinning about some unimaginable drain. Sometimes these drifted together, passing through one another like ghosts and parting in a trailing veil of stars.
Young stars grew in luminous cradles. Dead stars rolled in the glowing shrouds of their death.
Infinity unfolded. Walls of glittering swept past, revealing fresh fields of stars ...
... where, sailing through the endless night, made of hot gas and dust but recognizable nevertheless, was a turtle.