Howard Jacobson: The Ten Commandments would have faded long ago if they sounded like a self-help book

What is revealed in the grandeur of the writing is the grandeur of man's conception of his being

We've done Dawkins already in this column, and like to think that what we've done stays done. There is intellectual justification, sometimes, for breaking a butterfly on a wheel, but to break it twice is sadism. Which said, Dawkins' rewriting of the Ten Commandments in his latest blind foray into theology, The God Delusion, cannot be allowed to pass without remark.

We will take just one Commandment. The Seventh. "Thou shalt not commit adultery." Leaving aside the retributive consequences if you do commit adultery - the small print, as it were - the Seventh is a Commandment that has a lot going for it. It is unambiguous. It is sonorous. It tells you, should you be thinking of taking up adultery but feel in need of further guidance, everything you ought to know - DON'T!

Unlike several of the other Commandments, such as remembering the Sabbath day to keep it holy, and not taking the name of the Lord thy God in vain, it has gone on finding resonance with human experience in most parts of the world and throughout centuries of fluctuating faith. Of course it hasn't stopped us committing adultery; but we rarely - swinging, dogging and daisy-chaining notwithstanding - believe we are unequivocally right in our adulterousness. We pause on its threshold and think twice before we enter. And even when our last compunctions capitulate before a seemingly irresistible force, that is seldom the end of it. A Commandment can have a retrospective urgency. I committed adultery but I should not have done. Or, I committed adultery and in the same circumstances would commit adultery again, but I acknowledge the misery and havoc I have caused.

Actions have their consequences, that too is what a Commandment teaches. And in those consequences we need not, if we do not care to, see the unsmiling face of God. Let a man be the most confirmed atheist who ever held a Chair in the Public Understanding of Science, he will still know the anguish of adultery if he is its victim, or the alternating joys and woes if he is its instigator, unless he is without feeling altogether. God, it seems to me, need hardly enter into it. Paolo and Francesca, the adulterous lovers whom Dante comes upon in the fifth Canto of the Inferno, entwined in an embrace of eternal weeping, are in a hell of their own making, not God's.

"Amor condusse noi ad una morte, Francesca tells the poet - "Love led us to one death". For ever together - that is the consequence of their adultery; not a finger coming out of angry clouds, but their consummation itself, repeated and repeated and repeated. Not only is this not a story of divine retribution, it is not a morality tale either. Adulterous loves works out its logic, that is all there is to say. And before the sadness of it, Dante falls, "come corpo morto cade" - "as a dead body falls".

A solemn business, then, adultery. As is all fornication, no matter what the circumstances. Eroticism has a terrible potential for tragedy. We take it lightly at our peril.

So what is Professor Dawkins' take on these exhilarations and sorrows, their todays, tomorrows, and eternities? What is his alternative Seventh Commandment, emptied of the interferences of a non-existent God? Reader, believe me when I say I have not made up the words I am about to quote. And do not think me callous: what follows is not my doing or my fault.

Here then - and you can always look away if you can't bear it - is "Thou shalt not commit adultery" in Dawkinsese. "Enjoy your own sex life (so long as it damages nobody else) and leave others to enjoy theirs in private whatever their inclinations, which are none of your business."

As a reader, I look for one thing above all others in a writer, whether that writer is a poet, a novelist, or a scientist on a polemical errand. I look for language with deep roots. The better the writer, the deeper into the soil of thought and imagination does his language seem to reach. The poorer the writer, the more scattered on the surface, as though pulled out and discarded long ago, are his words.

This is not simply a matter of aesthetics. When Nietzsche - no lover of God himself - finds in the Old Testament "men, things and speeches of so grand a style that Greek and Indian literature have nothing to set beside it", he is not admiring mere expression. "One stands in reverence and trembling," he goes on, "before these remnants of what man once was."

What is revealed in the grandeur of the writing is the grandeur of man's conception of his being. We don't have to like it or approve it, we just tremble. As we tremble before that dread injunction, brought down from a burning mountain - "Thou shalt not commit adultery".

Words strike us as commonplace when the thoughts they express are commonplace. Or when they are inadequate to the complexities of the subject. "Enjoy your own sex life" might pass muster as an expression of easy-going liberalism in the company of unexacting friends, but as a guide to behaviour it dishonours us. It assumes there's nothing to us.

Do not mistake me. I am no more censorious of other people's inclinations or their acting on them than is the Professor. Indeed the more outlandish their inclinations the better, I say. So it is not in the name of divine prohibition or prudery that I diss Dawkins. His Seventh Commandment is feeble not because there is no God in it but because there is no human in it. The man writes as though he has never lived.

And never read, come to that. Would "Enjoy your own sex life" (so long as no one gets hurt, naturally) have been helpful advice to Madame Bovary, who if anything enjoyed it too much when she could get it? Was an enjoyable "sex life" all that stood between Anna Karenina and happiness? Is it true that our actions have neither value nor repercussion in themselves, but acquire them only by the harm we do or don't do to others? Does sex resist all philosophic and ethical enquiry beyond the requirement to have fun but practise damage limitation?

"Thou shalt not commit adultery" is a Commandment most of us will disobey. But it shakes us to the core. There is reverence and trembling in it. "Enjoy your sex life" makes sex sound like a good breakfast. A thing necessary to our well-being but uncomplicated and soon forgotten, like Dawkins-man himself.

It is not God that Dawkins cannot find, it is us.