Imagine the following scenario. You're a young man from rural England. Your girlfriend is having a baby. For some unfathomable reason, the pair of you have decided that it's best if the baby is born in a mountain village in eastern Turkey. You entrust the delivery of the child to a 17- year-old girl who has recently arrived in the village. She doesn't talk. At all. But no matter, people talk too much about babies anyway.

INVENTING GOD
Nicholas Mosley
Secker & Warburg
296 pp
£16.99 The birth goes well, as you knew it would — this is just what happens when you're away from the trappings of modern medicine. Girlfriend and baby asleep, you go outside, to find your silent, seventeen year old midwife sitting by a nearby river. And she speaks, for the first time ever, as far as you know. So what do you say to her? How about: "Bloody hell, you can talk!" or "Hey, thanks for the baby thing!"? No, you say: "Oh Gaby, did you want to save the world? All proper people want to save the world!"

Of course, if you went around saying this kind of thing in real life, pretty soon, and for good reason, nobody would talk to you at all. But in the world of Nicholas Mosley's Inventing God, this is how people speak – and think – all the time. So here's Gaby, later in the story, explaining how she escaped from an unfortunate burial incident: "But I did get out, I don't know how; does one know one's birth? Or what has been going on before it? It is as if chances have come together from the ends of the earth – to make a construction equal to the great Temple of Solomon, the Dome of the Rock — I know so few wonders! — but how wonderful is a human embryo!"

So what's going on here? Why do Mosley's characters speak in this way? Partly, it is just that they are very silly. What other conclusion is it possible to draw, for example, about a woman who looks at the display on her mobile phone, and thinks that it is "the sort of porthole through which you view strange creatures at some unimaginable depth of the sea"; or about a man who responds to a woman's fear of being alone in a strange place by telling her not to worry, because "these people believe in angels"?

But it's not just that they are silly. It is also because this is a 'novel of ideas'. The characters, who are assorted scientists, philosophers, anthropologists, theologians and mystics, spend their time ruminating on the nature of God, morality, freedom, religious tolerance and sexual politics. The trouble is that they seem to have so few good ideas between them.

One of the central themes in the book is that in a secular age of great technological power, it is necessary for humans to "invent" God, in order to attain the kind of autonomy that grounded choices bring. OK, so you might get some kudos for floating this idea at a Hampstead garden party, but it certainly isn't something you'd want to commit to print. After all, why on earth would anyone believe it? Sure, if the claim is simply that freedom without constraint doesn't amount to much, then that's true, but obvious. But if it is that human autonomy requires that we tell ourselves stories about a transcendent being or realm, then not only is no good reason proffered in Inventing God for believing such a thing, but there is no good reason for believing it.

Part of the difficulty with Mosley's book is that his characters are mostly so dim-witted that even when they have moments of lucidity one cannot take them seriously. Near the beginning of the book, for example, we find out that Masie, clearly having failed her GCSE biology, wants to die because she feels that every part of her body is occupied in surviving at the expense of every other part and, indeed, at the expense of everything else in the world. If she believes such an incoherent notion, why should we take notice of anything else she says later in the novel?

At this point, no doubt, more sophisticated readers will complain that Mosley's technique is being misconstrued here. Probably they'll insist that his novels should not be taken so literally; and that it is the maelstrom of ideas, rather than the dramatic structure, characterisation or speech patterns, which is important. This may be true, but in the case of Inventing God, it is besides the point. The problem with this novel is not that it is not realistic — though it isn't — it is simply that so many people say so many daft things so frequently.

Inventing God is available from Amazon (UK).