Recently , on the Savage Lovecast, Dan Savage's podcast about sex and relationships, a woman called to ask advice about her feelings for her brother-in-law.
"I have a bit of dilemma," she said. "My sister is a few years older than me and I'm in love with her husband. Her husband loves me back. I don't want to lose either of them. What should I do?"
Dan's advice was short, and to the point. "Stay the f*** away from your sister's husband."
And to me, the outsider, it seemed fantastically simple. The affair would destroy her sister's marriage, destroy her relationship with her sister, anguish their parents, and distress their family and friends. So why was this even a dilemma? Why would they not just stay the f*** away?
Well, we may ask ourselves the same thing about every couple who have ever had an affair. Let's take, for example, Barnaby Joyce, who has thrown a hand grenade into his life and is now watching it explode.
Barnaby had a relationship with a younger ex-staffer, and the staffer is now pregnant with his child. Joyce's wife of 24 years, Natalie, has confirmed that she is "devastated" at the betrayal. But the fallout doesn't end there. The Joyce's four daughters are now dealing with a separation, their dad's new girlfriend, a pregnancy and the public maelstrom. And, of course, there's the blow to Joyce's reputation; the politician has been a passionate advocate of the sanctity of marriage and has outed himself as a hypocrite by blowing his own marriage to pieces.
So why do it? Why risk the complete devastation to one's family, the public humiliation and scrutiny, and the financial hit of divorce, for an affair?
The answer is simple. Lust.
Lust is a powerful force, perhaps the most powerful force we experience. Most of us find lust exceptionally hard to resist. Think of King Edward, who abdicated the throne to pursue a relationship with a divorcee. Think of Garry Lyon, who sacrificed his marriage, best friend and reputation to have a relationship with Billy Brownless's wife. Think of Bill Clinton, who risked impeachment to pursue a sexual relationship with a young intern.
Think of all the men and women you know who have risked their marriages, familial relationships, friendships and sometimes reputations, to have affairs. And for what?
"To be wise and love, exceeds man's might," wrote Shakespeare, and he is right. Love makes us do ridiculous things. Love makes fools of us all.
But is it love, or is it lust? Barnaby Joyce is reportedly "madly in love" with his new partner. The caller to the Savage Lovecast described her feelings for her brother-in-law as "love", and no doubt they are.
But let's be clear: the feelings didn't begin as love. One cannot grow to love someone without allowing oneself to love them. All romantic love begins with feelings of attraction, and love may grow from that when the attraction is nurtured. If you limit contact after realising you're attracted to someone, love won't be able to develop.
In both Joyce's new relationship, and the caller's relationship with her brother-in-law, both parties were unwilling or unable to resist the pull of the initial attraction and stop it in its tracks.
I have heard Joyce's relationship described as a midlife crisis and a cliche. I've heard Clinton's affairs described as an abuse of power. I've read analysis of Tiger Woods' sexual proclivities as an exercise in self-destruction. All these analyses no doubt have merit.
But ultimately, these behaviours all boil down to one thing: the prioritisation of lust over all other considerations.
"If you put love and lust together," writes Rabbi Shmuley Boteach in 'Kosher Sex', "love stands no chance." Sadly, this seems to be true.
I don't doubt for a second that Joyce loves his four daughters, and, possibly, even his ex-wife. I don't doubt that many people who have affairs are still deeply attached to their families, and their friendships, their reputations, their lives.
But lust seems to be a more powerful force than any other attachment most of us can have. And until we learn how to control it, and how to turn away from its lure, affairs will continue to wreak havoc, and the fallout will endure.