He does not know how much he does not know

Sam Leith IN GOD WE DOUBT by John Humphrys Hodder, £18.99, pp. 336, ISBN 9780340951262 £15.19 (plus £2.45 p&p) 0870 429 6655 There's a wonderful story in this book, told by the biologist Lewis Wolpert, about a vistor to the office of the physicist Niels Bohr. The visitor, a fellow scientist, was astonished to see a horseshoe nailed above the Nobel laureate's desk. 'Surely you don't believe that horseshoe will bring you luck?' he said. 'I believe no such thing, my good friend,' replied Bohr. 'Not at all. I am scarcely likely to believe in such foolish nonsense. However, I am told that a horseshoe will bring you good luck whether you believe in it or not.'

As John Humphrys says, that's 'funny and profound in the same breath'. I wish the same could be said for In God We Doubt, a book that does the Today programme inquisitor we all so admire no favours at all.

Not long ago, Humphrys presented a radio series, Humplays in Search of God in which he interviewed a number of senior religious figures and invited them once and for all to persuade him, live on air, of the existence of the Almighty. Oddly enough, they failed. But the programme earned him the biggest postbag of his career and so In God We Doubt — a book-length shrug of the shoulders — is his follow-up.

He begins with some musings about the Big Questions, enlivened by a personal sketch of his dutiful, church-going childhood. Then he makes the reasonable point that the Enlightenment has failed to kill off religious faith, and that the angry thunderings of Dawkins, Hitchens and Onfray don't address the enduring human disposition to belief.

He meanders through ethics, ontology and sociology. He reproduces some passages of his interviews with the Archbishop of Canterbury, the Chief Rabbi, scientists and others, and talks about them. He hands the mike over to the audience a bit, too, with one section that anthologises the best bits of his postbag from the radio show. Then he draws his conclusion, which is that God doesn't exist — 'or does he?'

The God over whose existence he muses is mostly Anglican, sometimes Catholic, occasionally Jewish, more seldom Muslim. Humphrys's notion of prayer is more or less indistinguishable from cosmic ordering. 'As for the concept of the Holy Trinity, I still don't understand it. Does anyone?' His own doubts about the existence of God, he tells us more than once, were exacerbated by his experiences as a reporter. He kept going to foreign countries, seeing kids with flies in their eyes and so forth, and got to thinking about the Problem of Evil.

In this book Humphrys selfconsciously revels in the role — to adapt Flann O'Brien — of the Plain People of Wales. His language is littered with phrases such as 'that's all very well, but', 'so much for the physics', 'offhand I can't think of', 'as far as I'm concerned', 'those of us who take a less intellectual approach', 'I'm no theologian, but', and 'who knows?'

The correlative of this persona is a faintly phoney deference to 'clever people like Roy Hattersley'. Humphrys is a great dispenser of the chat-show compliment. Richard Dawkins: 'handsome, charming and married to a lovely actress'; Stephen Hawking. 'a powerful brain'; Rod Liddle: 'one of the cleverest and best-read men I know'; Jonathan Sacks: 'very clever and immensely knowledgeable'; Rowan Williams: 'in fairness to the Archbishop, he's not a man for the glib answer'; Douglas Adams. 'more than capable of giving plenty of philosophers a run for their money'; God: 'exactly the sort of person you'd want your daughter to marry if he were human'.

But the charm of this plain-man folksiness wears off, not least because it becomes an excuse for Humphrys to congratulate himself on shallow thinking, skimpy research and the exercise of 'common sense' rather than argument. When his interviewees give him subtle or complex answers — as both the Archbishop of Canterbury and the Chief Rabbi do — he makes little or no attempt to tease their meanings out. He seems oddly uninterested in his subject.

Alongside the Problem of Evil, he presents us with the Problem of Andrex. 'My own house had an outdoor lavatory and we used the evening paper rather than enjoy the luxury of lavatory rolls,' he writes of his childhood in west Wales, tut at least we had running hot water.' He invites us to think by contrast of the generation that came before — sustained through a war by their simple faith and without a scrap of quilted threeply in sight.

'Dawkins and company may find this risible,' writes Humphrys. 'They may scoff or even sneer. But if they do they should be ashamed of themselves. Believers have every right to be treated with respect.' As a plea for politeness, this is persuasive. But as an argument for or against the existence of God, it doesn't do a thing. Having wiped your bum on newspaper, it shouldn't be necessary to point out, doesn't make your beliefs about the set up of the universe one jot more or less credible.

Humphrys's arguments are riddled with unexamined assumptions, category errors and missed points. For unexamined assumptions, the discussion of ethics (he believes that moral truths are fundamental, universal and self-evident) is a doozy. Having pointed out that the ten commandments have nothing in them about racial or sexual discrimination, he writes: Any decent moral code that takes account of our more enlightened approach would put the torch to some of the rubbish spouted by certain fundamentalists.

Note 'decent', 'enlightened' and 'rubbish' — the muzzy-minded, bootstrap-pulling circularity of it. You're reminded of the sketch in which a man seeks to demonstrate the superiority of the English language: holding a fork, he explains that in French it's called 'tine fourchette', in German 'eine Gabel; and in Italian `ttna forcella' — tut in English we call it "a fork" which is plainly what it is.'

Accordingly, even as he sets out the tenets of 'any decent moral code', Humphrys starts to scrabble and slip. Among the Humphrys commandments is: 'It is not wrong to allow a woman to have an abortion so long as the rules set by society are observed.' Again, a mare's nest of philosophical difficulties not so much skated over as entirely unnoticed.

The question 'why is there something instead of nothing?' is attributed on page 4 to Leibniz and on page 225 to Jean-Paul Sartre. The political philosopher John Gray is described as a 'historian'. Humphreys thinks theodicy is a 'doctrine'. Having watched Titanic, he says, 'I still marvel at the way two third-class passengers' were able to caper at the prow of the boat without being told off by an officer. (Kate Winslet, as any fule kno, was a first-class passenger — rather the point of the film ) At one point he announces 'from this you and I might conclude three things', followed by bullet-points numbered from one to four.

He makes non-cosmetic errors too. 'One of the ways [genes] make sure they survive is by programming their organism to be selfish,' he writes when explaining Dawkins — which is rather to miss Dawkins's point: it's the genes that are selfish, the organisms only incidentally so. 'The thing about good science,' he writes elsewhere, 'is that it can be proved' — again, more or less the opposite of the truth. Good maths can be proved. Good science, as Karl Popper argued, can be disproved.

When he's not flat wrong, he's inane 'The first thing to exist was what they call a singularity,' he explains, 'which means everything in existence was concentrated into something so small you could put it in your eye and not notice it was there'. Trillions of years, he advises in the authentic voice of Alan Partridge, 'might seem a long time to you and me but presumably is no more than a blink in God's eternity'. Isn't 'presumably' great?

He counts as a point against the scientists the fact that one can ask them what happened before the Big Bang and in the end their answers boil down to not much more than Dunno really . . . Just happened didn't it.'

Actually, as Stephen Hawking once elegantly dispatched the question, to ask what came before the Big Bang is like asking what's north of the North Pole.

When Humphrys asks what he calls `the really, really Big Question —why?', he entirely collapses the purposive and causative senses of 'why', despite the fact that the gap between the two of them is where more or less the entire debate takes place.

I myself come to the question from a more or less mild version of the Dawkins camp. The idea that there is a personal God taking a benign interest in my affairs strikes me as perfectly absurd, but it's one among an infinity of hypotheses that strike me as absurd, and one I reject with no more or less firm grounds than the others.

I'm not hostile to Humphrys's book because I disagree with its conclusions. I'm hostile to it because he does neither the atheist nor the theologian the courtesy of troubling to understand the contours of their arguments. You may believe — indeed, you're pretty much required to accept — that these towers are built in the air; but they are delicately built by clever and serious people. Humphrys investigates their architecture with a wrecking ball.

It is fine to take a stand for common sense and plain talking. It is fine to hook your thumbs into your braces and announce that you don't know much about art but you know what you like. But it is not fine to take this as the starting point for a guide to the Uffizi.