Rowan Pelling: Don't go on about religion. Just decide, do you believe in fairies or not?

The debate about Narnia completely misses the point, as any seven-year-old could tell you

I am amused by the ferocious battle that is currently being fought between the forces of good and evil, Enlightenment atheists and Christian moralists, over the new Narnia film. In one corner stands Polly Toynbee, who writes in The Guardian that The Lion the Witch and the Wardrobe is an insidious example of, "the perfect Republican, muscular Christianity... heavily laden with guilt, blame, sacrifice and a suffering that is dark with emotional sadism." Crikey! It's The Passion of The Christ crossed with Nightmare on Elm Street. Cover your infants' eyes before they're gouged out! The other camp is cheer-led by church groups and the Daily Mail with the headline, "At last! A film that champions faith and morality." Jesus wept! The David Davis of Hollywood blockbusters. Let's all watch King Kong instead.

It was left to a letter writer to The Independent to strike a blow for common sense and point out that CS Lewis's Narnia books are, for most of their young readers, primarily about the belief in imaginary or hidden worlds. Hear, hear. You're more likely to become a nun after watching The Sound of Music. The question posed by Lewis is not: do you subscribe to Christianity? It is: are you prepared to make the leap of faith that says the realm of the imagination is every bit as real, as vivid, as profound and sacred as the physical world that lies around you? Do you want to visit magic snowbound realms where animals can talk and milk-skinned witches dispense Turkish delight?

For most children the answer is "yes". The membrane between fact and fiction is so porous before puberty that the leap of faith from imaginary friends to the land beyond the wardrobe is easily made. Lewis's Narnia is the classic fudge between Christian and pagan myth, where the so-called propagandist cannot help but be seduced by elements of older and even more compelling stories. Both traditions are fused with equal success in John Masefield's The Box of Delights and Susan Cooper's brilliant The Dark is Rising series.

The wrath directed against CS Lewis has much to do with the fact that he's now viewed as cruel and misogynistic on the grounds that the older Pevensie sister, Susan, is ultimately stranded outside Narnia because she's stopped believing and has taken to wearing lippie. I can't help wondering whether Lewis's critics would've been quite so livid if it had been Peter disbarred from paradise because he'd started in the City and was saving for a Rover. In any case Lewis makes it clear that it is Susan's free decision to deny herself the other world. Like most of us as we step on to the threshold of adulthood, she has to decide whether to relegate the world of untrammelled imagination or defend it against the derision of an increasingly sceptical world. It's a brave person indeed who declares in mixed company, "I keep fairies at the bottom of my garden." It's not religious belief that divides most readers so much as tolerance of, or belief in, the magical.

I was recently a guest on Radio 4's Saturday Review when one of the topics under discussion was the extraordinary Hemingford Grey Manor in Cambridgeshire, home to the late children's author Lucy Boston and one of the oldest continuously inhabited houses in the country. I told a true story about the house, but one that runs contrary to most people's notion of "the truth" or even what passes for a medically acceptable definition of sanity. My husband visited the Manor several times as a small boy and once found himself standing alone in the hallway by the open front door. As he gazed at the topiary chess figures that are the garden's striking feature he saw a small white horse with a horn on it's forehead appear and flit from bush to bush before disappearing. In his dazed state he heard footsteps behind him and turned to see Lucy Boston (then in her seventies). She said calmly, "You've just seen the unicorn, haven't you?"

As I recounted this tale I could sense that thepresenter, Tom Sutcliffe, was clenching his buttocks with embarrassment. I have some sympathy. But personally when I hear some fantastical story (spontaneous combustion, aliens, telepathy), I find myself of much the same mind as Lewis's Professor Kirke after he is approached by Peter and Susan to see what he makes of Lucy's tale of discovering Narnia. The old man asks if she is generally truthful. On being told she is he says he sees no good reason then to disbelieve her. That makes utter sense to me. Other people's versions of reality are surely their own business and, in any case, fiendishly hard to disprove. Some believe in string theory, others in God, and yet others in David Cameron's vision of a Tory Britain. I prefer to put my faith in the transporting power of magical fiction. And unicorns.