Dialogue: And what is more, I firmly believe that pigs might fly ...

A pig's orgasm lasts for half an hour.

I learned this splendid nugget a couple of weeks ago and it has since become a fixture in my conversational repertoire.

It sparks a lively response at any social event but is best reserved for formal dinner parties. It goes down particularly well with loin of pork.

I learned about the pig from Pat, a music teacher who has never to my knowledge or suspicion been in a position to verify the truth of his assertion. But that doesn't stop me believing it. The nub of the matter is not that I think it is true, but that I want it to be true.

There is probably a word for this tendency of mine, but I suspect it is a Greek word and I'm afraid all Greek is Greek to me. The word I'm looking for isn't stupidity and it isn't credulousness. I want a word to describe something altogether more wilful which has been the mainstay of my intellectual life. I want a word to describe the tendency of human beings to prefer the excitingly improbable idea to the dull and more probable one.

Why is it, for example, that for 30 years or so I have believed that glass is a liquid? It looks and feels like a solid, it sounds like a solid when I tap it, when I tap it too hard it slices my flesh, and yet I have told innumerable people that it is a liquid and for evidence I have pointed out that ancient windows are thicker at the bottom than at the top because over the course of the centuries the glass has slowly dripped.

Of course, I have never examined ancient windows to see if it is so, but someone whom I can no longer remember once told me it was so, and it sounded exciting to me and so I decided it was so.

And while I am at it, why should I and so many other people have believed that powdered glass in coffee is a recognised method of murder? Powdered glass in coffee would settle as sludge at the bottom of the cup and the victim would have to spoon the murder weapon down his throat himself. And even if he did so, the glass would pass harmlessly though his gut.

Nevertheless, for years I have believed the irrational, exciting opposite of the truth.

Just as when people come across flattened wheat, they presume not that wind has laid it low or that people or animals have trodden it down but that aliens have travelled hundreds of light years across the galaxy in order to crush a fraction of a cereal crop before going home. And how we all would like it to be true.

And why, when a friend is late for a meeting, do I always imagine that something disastrous has happened, that a car crash has left him mangled in a ditch? And if I am alone in a house at night, why, when I hear a noise, do I assume that it is not a possum on the roof or a creak in the weatherboards but rather an intruder with a baseball bat and malice, or a ghost with the face of a skull, so that I withdraw whimpering beneath the blankets?

And why, when probability theory tells the plainest story of folly, do a million people troop to the Lotto shop every Saturday to hand over money they love in the strange conviction that they have been singled out?

And why do people who know that we live in a galaxy of cooling lumps of matter circling other cooling lumps of matter cling to the belief, the hope, that destiny is written in the heavens, that the orbit of the planets somehow impinges on the fate of each of us?

And why when Elvis is dead, for which relief much thanks, should he reappear so frequently in the supermarkets of Tennessee?

Why should these and a thousand other superstitions, myths and fallacies so grasp our minds? For sure the wish is father to the thought, but why should the wish exist? Why should we want the world to be more than it is, to offer greater delights, stranger truths, greater mysteries?

Could it be that the miraculous truth of life is essentially a mundane miracle and we cannot accept that dust returns to dust, that the great random concatenation of chance and carbon and other stuff is ultimately barren, explicable and purposeless?

Is it that our consciousness, that gift which is both boon and burden, cannot be satisfied by brutal fact, cannot accommodate our own mortality, cannot accept that what is, is and there's an end to it?

I'm afraid I do not know. The only thing I know for sure is why pigs appear always to be grinning.