We've piled on to elves and yetis and all the other supernatural aspects of ourselves; we're happier to say that monsters are out there in the deep dark forest than locked in here with us. Yet we need them, in a way we find hard to articulate; the witch Granny Weatherwax tried to summarise it in Carpe Jugulum, when she said 'We need vampires, if only to remind us what garlic is for'. G.K. Chesterton did rather better when, in an article defending fairy stories, he disputed the suggestion that stories tell children that there are monsters. Children already know there are monsters, he said. Fairy stories tell them that monsters can be killed.

We need our stories to understand the universe, and sometimes we forget that they're only stories. There is a proverb about the finger and the moon; when a wise man points at the Moon, the fool looks at the finger. We call ourselves Homo sapiens, possibly out of a hope that this may be true, but the storytelling ape has a tendency to confuse moons and fingers.

When your god is an ineffable essence that exists outside of space and time, with unimaginable knowledge and indescribable powers, a god of boundless sky and high places, belief slips easily into the mind.

But the ape isn't happy with that. The ape gets bored with things it can't see. The ape wants pictures. And it gets them, and then a god of endless space becomes an old man with a beard sitting in the clouds. Great art takes place in the god's honour, and every pious brush gently kills what it paints. The wise man says 'But this is just a metaphor!', and the ape says 'Yeah, but those tiny wings couldn't lift a cherub that fat!' And then not so wise men fill the pantheon of heaven with hierarchies of angels and set the plagues of man on horseback and write down the dimensions of Heaven in which to imprison the lord of infinite space.78 The stories begin to choke the system ...

Seeing is not believing.

Rincewind knows this, which is why he encourages Shakespeare to make elves real. Because once you're called Mustardseed, it's downhill all the way ...

The elves cannot understand Rincewind's ploy. Not until his thoughts give it away to the Queen of the Elves, and the salvation of the world rests upon 300 pounds of plummeting orangutan.

Nevertheless, the plan worked very well. This is Oberon, near the end of the play: Through the house give glimmering light, By the dead and drowsy fire; Every elf and fairy sprite Hop as light as bird from brier; And this ditty, after me, Sing and dance it trippingly.

There's no hope for them. Next stop, nursery wallpaper. Whereas witches, now: Scale of dragon, tooth of wolf, Witch's mummy, maw and gulf Of the ravin'd salt-sea shark, Root of hemlock digg'd I'th' dark, Liver of blaspheming Jew, Gall of goat, and slips of yew Silver'd in the moon's eclipse, Nose of Turk, and Tartar's lips, Finger of birth-strangled babe Ditch-delivered by a drab—

Make the gruel thick and slab; Add thereto a tiger's chaudron, For th' ingredience of our cauldron.

No contest. What's a chaudron? Entrails. Definitely no contest. The witches appear on stage in Macbeth only three times, but they steal the show. They probably got fan mail. The fairies are present for a large part of A Midsummer Night's Dream, but it is Bottom that steals the show and only Puck has a glimmer of the old evil. They've been parcelled, stamped and sent on their way to Tinkly Wood.

To be sure, Shakespeare's Oberon is not all sweetness and light. He uses the juice of a herb, the flower known as Love-in-idleness, to enchant Titania, Queen of the Fairies, because she has gained possession of a changeling child, and he wants it. He makes her fall in love with Bottom, who at that point in the story is an ass. And he is appeased, and she is entirely happy with the turn of events, when she gives him the child. But that's low-level, sanitised nastiness, a fretful squabble, not a war.

The allure of the unknown fades into the tawdry reality of a specific representation, once you see it dripping sequins. Abraham's God of Extelligence was far more compelling than a few golden

(probably just gold leaf) idols. But when the Renaissance artists started to paint God as a bearded man in the clouds, they opened the way to doubt. The image just wasn't impressive enough. The pictures on radio are always so much better than those on TV.

For the last few hundred years, humanity has been killing its myths. Faith and superstition have been giving way, slowly and against considerable resistance, to the critical assessment of evidence. They may, perhaps, be enjoying a bit of a revival: many rational thinkers have bemoaned the slide into cults and the weird offshoots of New Ageism ... But those are all very subdued versions of the old myths, the old beliefs; their teeth have been drawn.

Science alone is not The Answer. Science too has its myths. We have shown you some of them, or at least what we believe to be some of them. The misuse of anthropic reasoning is a clear example, as in the case of the carbon resonance, but argued with no thought for the fudge-factor of the red giant.

The ideal of the scientific method is often not realised. Its usual statement is an oversimplification in any case, but the basic worldview captures the essence. Think critically about what you are told. Do not accept the word of authority unthinkingly. Science is not a belief system: no belief system instructs you to question the system itself. Science does. (There are many scientists, however, who treat it as a belief system. Be wary of them.)

The most dangerous myths and ideologies, today, are the ones that have not yet been destroyed by the rising ape. They still strut their stuff on the world's stage, causing grief and havoc -and the tragedy is that it's all to no purpose. Most of it doesn't matter. Issues like abortion do matter, to some extent; even 'pro-choice' adherents would prefer that the choice should not be necessary.

Issues like short skirts or lengths of beards do not matter, and it's foolish and dangerous to make a big fuss about them on a planet that is bursting at the seams with an excess of people. To do so is to promote the memeplex above the good of humanity. It is the action of a barbarian mind, a mind sufficiently removed from reality that the consequences of its resident memeplex do not affect it directly. It is not the actions of the naive young men who carry the suicide bomb, or fly the airliner into a skyscraper, that are the root of the problem; it is the actions of the evil old men who lead them to behave like that, all for the sake of a few memes.

The key memes are not religious, in this case, we suspect, even though religion is often blamed: that's mostly a smokescreen. Those old men are motivated by political memes, and the religious memeplex is merely another of their weapons. But they are also trapped in their own stories, and this is high tragedy. Granny Weatherwax would never make that mistake.

The elves are still with us, in our heads. Shakespeare's humanity, and the critical faculties encouraged by science, are two of our weapons against them. And fight them we must.

And to achieve that, we need to invent the right stories. The ones we've got have brought us a long way. Plenty of creatures are intelligent, but only one tells stories. That's us, Pan narrans.

And what about Homo sapiens? Yes, we think that would be a very good idea ...

1 And in this short statement may be seen the very essence of wizardry.

2 This one was apparently the result of a curse some 1,200 years ago by a dying Archchancellor, which sounded very much like 'May you always teach fretwork!'

3 Lord Vetinari, the Patrician and supreme ruler of the city, took proper food labeling very seriously. Unfortunately, he sought the advice of the wizards of Unseen University on this one, and posed the question thusly: 'Can you, taking into account multi-dimensional phase space, meta-statistical anomaly and the laws of probability, guarantee that anything with absolute certainty contains no nuts at all?' After several days, they had to conclude that the answer was 'no'. Lord Vetinari refused to accept 'Probably does not contain nuts' because he considered it unhelpful.