The Big Read: Lucky I'm not superstitious

What I'm about to say will upset some of you, and you'll be quite right. What I did was irresponsible and wrong and you shouldn't do it, and I don't mean to set a bad example to the kids and I'm not trying to glorify crime.

I don't think the rules don't apply to me. Okay? Also, if you're one of those people who require apologies, then sorry.

So here's what happened: I was once on a trip to the Cederberg mountains and I visited an area where some archaeologists were sifting and digging. It was at the confluence of two ancient rivers, where a number of ancient folk had made a seasonal dwelling and where floods over thousands of years had washed down and deposited flints and stones worked for use as rudimentary tools. I don't mean to minimise my crime when I say there were several hundred thousand of these things lying around and crunching underfoot. You couldn't throw a stone without hitting an ancient tool, and it turns out there was at least one modern tool as well, because the fever overcame me and I pocketed a good one to take home and place on the shelf of treasures in my study.

Everyone should have a shelf of treasures. Mine includes a vulture feather and the bleached-white vertebra of a lioness from the Serengeti plains (which I gave to my friend Henrietta for luck) and a blue-black batch of brittle lava from an Indian Ocean volcano and an unopened Bucanero Fuerte beer from Cuba and some frankincense and myrrh from Yemen and a trilobite in its bed of rock and a rusted ancient horseshoe I found in the overgrown garden of Napoleon's house on the island of St Helena. There's a vulture's feather, and a Maasai blade and a paper fan from Shanghai. And also the arrowhead-shaped cutting tool that I carried home from the Cederberg.

Those treasures mean more to me than just souvenirs or keepsakes; I suppose they're there to remind me that the world is interesting and that I can participate in its interestingness, and those are important things to remember on grey days when the blues brush against you with their wet, folded wings.

Perhaps I also keep them as talismans - they bring me luck, they make me brave. I don't actually believe in luck, or in talismans or superstitions, but I've found that life is more interesting if I sometimes live as though I do, because life is also more interesting when you acquire the trick of believing two opposed things at the same time.

I showed the tool to a friend and she said: "Oh, that's bad karma, you should give it back." I roll my eyes at the word karma, but it reminded me of the story about the Petrified Forest National Park in the Painted Desert in Arizona.

It's called Petrified Forest because there are trees and shards of wood from the Triassic period that have turned to stone. The park receives a good many visitors and at one point officials began to fret that too many people were taking away bits of petrified wood they found lying about on the desert floor.

They publicised a letter they'd received from a fellow in India, returning the chip of wood he'd taken, claiming it had caused him terribly bad luck. They actively encouraged the rise of the superstition that wood from the petrified forest brought bad luck, making up urban legends and anecdotes, and soon there was a deluge of wood pouring back from around the world, accompanied by tearful letters of confession from people who had just lost a job, or a marriage, or their health.

Very often the wood had been taken on a family holiday five, 10, 20 years before. It must come as an overwhelming relief to be sitting with bad news and racking your brain for what may have caused it - have I walked under any ladders? Do I have a tribe of Israelites imprisoned at the bottom of my garden? It can't be random, can it? It can't just be how the wheel spun, or a consequence of my choices? - and then to suddenly remember: Ah! The wood! Yes! The wood!

Human beings will make meaning out of anything. It's a particularly modern idea but also an especially primitive one, that everything happens for a reason. It's nonsense, of course, but perhaps it's more helpful than harmful. I have lucky underwear that I use for travelling, a lucky T-shirt that I use on hot days when I want to seem cool. Ever since I picked up that sharp-edged tool I haven't - knock on petrified wood - had anything seriously go wrong in my life. Maybe I'll hold onto it a little bit longer.