'Till death do us part." Those are the immortal words we say to the person who we hope will be our husband or wife for the rest of our lives. But with people living longer than ever, we are making a commitment that will last for many decades. Is the fact of our increased life span setting many marriages up for failure and, as a result, is monogamy past its sell-by date?
Now the actress Emma Thompson, herself happily married to actor Greg Wise, has stepped into the debate saying more choices are needed than just for and against.
She says that she felt monogamy was "an odd state for women" and wondered about "alternatives, and about whether our fury and rage and disbelief and horror about infidelity is quite realistic".
"I understand the feelings very well, but, as I get older and think about long-term relationships, I do see that they can change." Her suggestion is that we have "three relationships over the three stages of your life; your young life, your middle life and your late life".
Everywhere we look from films to advertisements, the idea of meeting the 'One' is all pervasive. This notion that your soulmate is somewhere out there is everywhere in popular culture.
And yet marital breakdown is a fact of life, with the most recent figures showing the rate of breakdown at 9.7pc. The headline-grabbing figure from the Census of 2011 was the fact that since 2002 the number of Irish people who have been through a divorce has soared by 150pc to a little under 88,000 people.
Divorce has changed the marital landscape as has our increased longevity. According to Elizabeth Abbott, author of A History of Marriage, the 20th Century ushered in the most extraordinary rise in life expectancy in human history, from 46 years to about 74 for men and from 48 years to 80 for women. And, she says, if spouses were living much longer so were marriages.
According to Elizabeth, the idea that romantic love has an important or even foundational role in marriage is a relatively modern one.
"In the days of arranged marriages, you did not expect great love and a soulmate, and so you judged your marriage by different standards. But with love playing a huge role in modern marriage, the likelihood of love burning brightly and constantly and faithfully is greatly decreased as marriages -- like spouses -- live on and on and on," she says.
"So without perhaps realising the significance of our likely longevity, people often prefer to collapse a marriage that is no longer underpinned by romantic love, and often this is because they feel cheated without that love, and are highly motivated to find it in another partner.
"Other people, however, either manage to maintain and nourish what they consider love over their long lifetimes or -- more commonly -- they accept that the passage of time changes people and their feelings but they work around that and stay together for other core reasons: they are happy and fulfilled in their lives despite these changes; they are guided by financial common sense; they are not wedded to some ideal of perfection in relationships but are prepared to accommodate change and incorporate it into their lives. Many are also influenced by their desire not to hurt their children," says Elizabeth.
Paul Ryan, a lecturer in sociology at NUI Maynooth, says there are two conflicting messages at play when it comes to monogamy. He believes that from a young age we buy into the idea of romance and, central to this, monogamy is seen as the ideal.
However, he says the other message is one of self-fulfilment and reaching your full potential as a person with constant scrutiny of the self, adding that these two ideas are clashing more than ever as society throws off its traditional shackles.
When it comes to monogamy, Paul says that we don't tend to jump into it, with Irish men and women marrying later than many of our European counterparts. We're also more likely to live together before marriage.
Women are much more likely to initiate divorce or separation proceedings than men, and the idea of a man in the relationship running off and having an affair as part of a midlife crisis is overblown, he adds.
Bernadette Ryan, a relationship counsellor with Relationships Ireland, says that we are hardwired for monogamy but marriages can get rattled by many things and not just infidelity.
"I would be of the view that infidelity is just a symptom of what's going on in the relationship. When somebody goes outside the relationship, their needs are not being met in the relationship they're in. When a couple comes in after an affair a lot of trust has been broken but sometimes it can be the catalyst to address their issues."