Can you be happily married and have a good sex life?
The story goes like this: two men are in a pub when a beautiful woman walks through the door. Conversation stops. Every male eye swivels in her direction.
Then one of the men leans over and whispers to his friend: 'Somewhere, there's a man who's bored out of his mind with making love to her.'
Or, to put it another way: when it comes to the bedroom, familiarity breeds contempt.
A new book, Mating In Captivity: Reconciling The Erotic + The Domestic, which has shocked and gripped America in equal measure, claims the problem at the heart of modern marriage, and the reason for our current sky-high divorce statistics, is that domesticity destroys sexual desire, no matter how loving a couple may be. In other words, sex and marriage are not naturally compatible.
Its author, Esther Perel, says: 'There is a paradox between our need for security, familiarity and predictability, which is what we see in our long-term relationships, and the fact that eroticism thrives on novelty, mystery and risk. It creates a tension between our need for security and our need for adventure. Love and desire: they relate and they conflict.'
In chapters with titles such as Democracy Versus Hot Sex and Sex Is Dirty: Save It For Someone You Love, the Belgian-born therapist argues that, unlike love, sexual excitement doesn't always play by the rules of good citizenship. It thrives on power plays, unfair advantages, role reversals, seductive manipulations and subtle cruelties.
We throw all this aside the moment a wedding-ring slides on our fingers. But the fundamental nature of desire doesn't change.
Perel, 48, who lives with her husband of 21 years and two sons, says her intention in writing the book is simply to 'put the issue out there, so that it's discussed around the table.
'Perhaps in some relationships, it may become a tipping-point. We all experience the ebb and flow; in more than two decades of marriage to same man, I certainly have.
'Sometimes it's just about hanging in there a bit longer. Lots of couples who split are no less good than those who stay together. The others were just able to wait a little longer, and had some glimmer of hope.
'Every so often they experienced the spark just long enough to know that it will come back. What people flee from is the sense of deadness. The opposite of connecting with someone is when you lay next to them and you just experience deadness, and that's terrifying. But we all go through it.'
Articulate, warm and extraordinarily empathetic, within ten minutes of talking to her, I'm confiding in her as if I were in the confessional.
Perel suggests that the secret of marital success is not the modern mantra of 'intimacy, intimacy, intimacy', but to treat your spouse like a stranger.
Modern culture, she argues, constantly tells us that the solution for the conflict between love and desire is increased closeness. If we talk more, share more, and communicate more, it will lead to better sex.
But Perel says just the opposite is true. 'It's not the lack of intimacy that inhibits desire, but too much. In our love life we want closeness, but desire needs space. There's nothing wrong with living in close proximity, but it doesn't bode well for eroticism. Our partner becomes known and fraternal, and sex needs the unknown, the risky, to thrive.
'If you can look at your partner and there is something about them that surprises you, even if it's just fleeting, then you can recapture what you have lost,' she says.
But staying mysterious and alluring is easier said than done when you're sharing a bathroom or breast-feeding the baby.
'Yes, the tension between security and adventure is doubled when kids come along,' she agrees. 'I have two sons aged ten and 13, so trust me, I know. Family life needs consistency and regularity and routine. Eroticism resists constraining. But what you notice about families with children is that the energy hasn't really gone from the house, it's just been redirected towards the kids.
'You need to refocus that energy back on your partner. Not all the physical contact in the house, like hugs and kisses, should be with children at the expense of the two of you.'
She says: 'Don't forget, children need the stability of a family. It's in their interests, too, if you put your relationship with each other first.'
With her common-sense approach, Perel, who lives with her family in New York, unexpectedly reminds me of my mother, who always made it clear to my siblings and me that, much as she loved us, her marriage to our father took priority.
'Your mother wasn't exceptional for her time, though her view is generally regarded as taboo these days,' Perel observes. 'Our society has become totally child-centered, putting children at the top of the pyramid instead of the bottom, where they belong.'
So what does Perel suggest to bring back the magic for a couple who've grown to treat each other, as she puts it, like a comfortable, worn-out sofa?
'First of all, the spark doesn't come naturally!' she says. 'You have to be wilful and intentional about desire. If you wait for the right moment, it will never come. You have to make it happen, you have to be pre-meditated about it.'
Much of what she suggests is standard rekindle-the-spark fare: meeting your partner for a lunch date, for example, or pretending to be strangers in a bar. But she doesn't claim to be saying anything new: 'We all know the answer, yet everyone tells me it sounds so fresh and bold.'
She advises couples to go away together, without the children, as often as you can, so that you can remember why you are together in the first place.
She is only too aware of the problems of our nuclear, rather than extended, families, which lack the support network of grandparents and aunts to babysit. But she refuses to allow this to be an excuse.
'Take turns with friends. Make time. Your children need you to have a healthy sex life.'
Part of the problem, she says, is that we are asking one person to provide 'what an entire community used to give. So, talk to other people. Have a best friend.
'Maintain your own interests. Go on trips, even if your partner doesn't want to go. Create some freedom from each other, so you have something to talk about when you meet again.'
Keeping something back, having some secrets, she says, is vital for a healthy marriage. After all, no one wants to read the same book again and again.
Like Perel, I'm now married to an American; the culture gap alone ensures that, even after six years, he is still full of surprises. Nonetheless, at the end of our interview, I ring our babysitter and spend a pink-cheeked hour trawling through a few unfamiliar websites.
Just in case.