Science of Discworld III

and his crew came through in that most unlikely of passages. There is a sense, of course, in which every sea passage is equally unique, just as every deal of cards is unique; but Odysseus’s journey, like a one-suit-per-player deal of cards, is totally remarkable too. Looking back into history, can we find journeys, events, and processes so remarkable that they seem to be the results of previous acts of free will?
    What, then, is causality? For Damasio-like reasons, we tend to think that what gives history its dynamic is the big events, the ‘pivot points’. The fallacy is that we think big causes are needed to produce big effects. This is false (butterfly) but there is a problem: choosing the right tiny change (which butterfly?). And there are always billions of new butterflies, dragging new changes out from previously invisible differences ‘in the 13th decimal place’, unobservable until their effects show up.
    Real history is like this; causes are often distributed, with huge numbers of tiny events all coming together. It is just this problem that leads Ridcully to employ such a huge number of wizards, doing such a bizarre set of trivial things, merely to get The Origin written.
    We only justify this sort of causality in retrospect: history didn’t know ‘where it was going’. So changing the past creates a context for the future, not a causal chain, and this is how the wizards must operate, which is why we have thousands of them making endless trivial changes to Victorian history, instead of, say, assassinating Queen Victoria. Any Victorian, perhaps particularly the well-trained nursemaid, will tell you just that about your personal history: your heart must be pure (context) rather than your plans being subtle.
    1 Counterfactual: a more acceptable word for what has for a long time been a very common feature of science fiction, the ‘alternate world’ or ‘worlds of if’ story (there was a pulp SF magazine in the 1950s called Worlds of If , in fact). ‘Counterfactual’ is now used when said stories are written by real writers and historians, to save them the indignity of sharing a genre with all those strange sci-fi people.
    2 Well, there might be …

SEVENTEEN
GALÁPAGOS ENCOUNTER
    C HARLES D ARWIN WAS SITTING ON a grassy bank. Three types of bee buzzed among the flowers, and overhead examples of Hirundo rustica swooped after miscellaneous Ephemeroptera .
    His thoughts were complex, as human thoughts tend to be when the mind is idling, but included: this is an interesting bank of astonishing complexity; there might be fish for lunch; he had a sore throat; he hoped never to receive another letter about barnacles; the rash seemed to be getting worse; there was a strange buzzing sound; had he really experienced that apparition?; homeopathy transcended all common sense; he really should find out where the ovaria were situated in Phyllosoma; it really was a very loud buzzing …
    Something like a yellow-brown smoke was issuing from a hole in the bank a few yards away, and resolved itself into a cloud of angry Vespula vulgaris . It bore down on the horrified Darwin –
    ‘Over here, waspies!’
    Darwin stared.
    This mission had created a difficult decision for Rincewind, when he’d been presented with the task of preventing Charles Darwin being stung to death by wasps. Right from the start it was obvious that Darwin would see him, and if Rincewind was invisible the wasps wouldn’t see him . He’d therefore undertaken the mission carryingtwo buckets of warm jam and wearing a pink tutu, an acid-green wig and a red nose, reasoning that (a) Darwin wouldn’t believe that he had seen him and in any case (b) wouldn’t dare tell anyone …
    Darwin watched the apparition skip away over the fields. It was quite astonishing. He’d never seen wasps swarm in such a manner.
    A piece of paper fluttered to the ground. The curious clown must have dropped it.
    Darwin picked it up and read, aloud, ‘“Return me, Hex”. What does—?’
    The afternoon dozed on. The grassy bank went back to its buzzing, humming, flowering busyness.
    On the forlorn shore, a man appeared, hid two buckets behind a rock, and removed his false nose.
    Rincewind scanned the landscape while extracting his hat from inside his shirt.
    This was one of the most famous islands in the history of technomancy? It looked, frankly, rather dull.
    He’d been expecting forests and streams and a riot of creatures. You couldn’t move for vibrant,