Without belief, can we go on cursing our enemies or blessing our friends?

as the power to curse lost its meaning for modern man? Might we, in losing it, lose something precious: the power to bless?

I was made to think about this last week, in Bristol, recording for later broadcast a couple of programmes in a series I present for BBC Radio Four. Off the Page is a modest little affair in which three writers discuss with each other and with me the short columns I have commissioned from them on a single, simple subject. Each week we take a different topic and I invite different writers (some famous, some new or unknown) to join me in talking and writing about it. The result is discursive, very informal, sometimes rambling, often sharp, never thoughtless or dim. At its best it is like half an hour with The Spectator.

I learn so much from my guests: what they think makes me think. Indeed, so absorbing are their thoughts that it sometimes slips my notice that I am presenting a radio programme and I find myself staring into the middle distance, rapt in thought as my worried guests wonder what they're supposed to do next.

This happened on Thursday afternoon as. with George Dobell (a freelance journalist and broadcaster), Lilian Pizzichini (a biographer) and Tony Cassidy (a soulband singer and short-story writer), I discussed our chosen subject: Superstition.

Like many lapsed Roman Catholics, Tony Cassidy had a wry and spirited view of his old faith, tinged both with bitterness and mockery. He was inclined to see the whole Roman edifice as an elaborately constructed web of superstition. George Dobell had no axe to grind against any particular Church, but took a witheringly rationalistic view of all otherworldly and spirit-worldly beliefs. He was a young Gradgrind but a funny one. He wondered how a rabbit's foot could be lucky. It had not been lucky for the rabbit, he pointed out.

Lilian Pizzichini felt more troubled by our subject. With her rational side she rejected superstition, but could not quite bring herself to speak ill of magpies on a broadcast programme — just in case.

I sympathise. I give money to beggars, just in case, and touch wood, just in case. A nervousness of the dangers of tempting Fate was instilled in me in childhood and I go through life forever glancing sideways lest any lapse into hubris annoys some minor god. I cannot shake it off. I try never to use words which assume that a planned course will run smoothly.

We managed to tease from Lilian a confession which she only half thought was funny. She has been cursed. In Wales.

Out of courtesy to those who may want to listen to the programme I shall say no more about this; but Lilian Pizzichini's admission began a small discussion of the concept of cursing, to which, in idle moments, I keep finding myself returning. The curse is a half-disregarded, half-buried part of our philosophical heritage. As a living sinew within our 21st-centuty liberal culture, it maybe dying.

What is it, or was it, to curse? Two elements are essential to the action, properly understood. A real curse is, first, more than a strong expression of antipathy; it is an attempt to harm its object, or put them in fear of harm. Second, it involves more than the curser and the cursed, for there is a third party: to curse is to invoke — or at least call upon — an external power to do the harm.

Of course much of what we call 'cursing' amounts to little more than the verbal shell of what was once an inhabited belief. 'Damn you' or 'Go to Hell' no longer express anything but anger or rejection, but they express it through a sort of metaphor: a metaphor which would have no meaning shorn of its reference to an underworld or place of damnation. We do not, most of us, believe in Hell any longer; still less that any spell, incantation or form of words could assist another soul's passage there. But we know what the idea means. When in the Old Testament Job curses his fate, curses life and curses God himself, the words still prickle the back of the neck. A Jewish curse against enemies — used as part of the Passover ceremony and too long to quote here — is chilling. I know from my former work on the Broadcasting Standards Council that any broadcast reference to the use of dark powers gets a powerful reaction from a surprisingly distressed minority.

And, disproportionately, they will be Christians. Given that Manicheanism or dualism is, strictly speaking, a heresy, it is worth asking why. I suspect it is because, despite Jesus's evident intention to free his followers from fear, a belief in the forces of light comes most readily to those inclined to believe in dark forces too — and vice versa. Those who suspect they are capable of being cursed, and perhaps capable of cursing others too, will be readier to hope that they are also capable of being blessed, and perhaps of blessing others.

'Bless you' still has, to me, great beauty both as a phrase and as an idea. I find some of the Christian blessings among the most moving passages in literature, as is that old Irish blessing 'May the road rise to meet you,' etc., which people love to quote. But if we entirely lose our sense of even the possibility of a power outside ourselves which might be called upon to help and protect those we love, then these words and phrases may one day come to seem as meaningless as the casting of bones or invocation of tree-spirits in pagan cultures: an amusing, senseless oddity.

To call upon a great external power — supernature itself — to intercede to protect or to harm another is just about the most thrilling expression of love or hate that has been available to human beings. As belief in the very existence of such a power diminishes, so does the taproot of both the blessing and the curse: different flowers on the same tree. A tree can survive for some time after its root is cut but it must wither in the end; and perhaps our age finds itself in just such a case. Curses and blessings retain their vigour for us, but the philosophical energy that created and sustained them may be drying up.

If so, I am sorry. As George Dobell drily observed, it is not an argument for the existence of a force that if we ceased to believe in it there would be adverse consequences; but a world without blessings or curses would seem a flatter, deader, greyer place.

Matthew Parris is a political columnist of the Times. The new series of Off the Page begins on Friday, 25 July at 11 p.m.