What's the greatest betrayal a person can inflict on his or her romantic partner? In the United States, having sex with someone else is pretty much the officially sanctioned worst-thing-you-can-do. Of course, there are a few even-more-terrible things--criminal offenses involving broken bones, nonconsensual sex, and abuses of children. But those matters aside, adultery is the reigning champion of romantic transgression, a sin guaranteed to permanently cripple a committed relationship, if not kill it altogether.

At the risk of calling into question one of the few rules of conduct that most Americans actually seem to agree on, I have to ask: why does the physical act of sex trump all other forms of human connection? Of course we all learned the answer in high school health class. Sex between two people is the most intimate activity they can share. It creates a bond, however ephemeral, that has lasting ramifications, some of which are so abstract and elusive that only the subconscious can be trusted to fathom them completely. We're told there is an inherent depth to sex, a gravitas unmatched by more cerebral activities. Therefore, to stray beyond the bed to which one is committed is to undermine all levels of trust, all levels of shared experience, friendship, and love.

Really? I've spent more than a few vermouth-intoned evenings discussing with friends the subject of whether or not adultery is all it's made out to be. Admittedly, I've never been married and I've never cheated on anyone or been cheated on in any manner that might make me especially qualified to fashion an argument for either side. My inquiry is hypothetical and is, more importantly, simply an inquiry. But speaking as a relatively observant person who knows a relatively large number of people, married and unmarried, I can't help but wonder if we're living in a time and place where the institution of marriage has been burdened by absurdly unrealistic expectations.

It seems to me that there are myriad ways to be unkind to your spouse. You can consistently ignore what he or she has to say, put your own needs first at every turn, refuse to pull your weight, abuse your body, your money, or anything else that affects your relationship. But despite the endless opportunities life gives us to be bad marriage partners, having sex with another person, even if the encounter is singular, brief, and unrelated to any larger marital crisis, is, by common consensus, the least pardonable sin. I'm always amazed by the way Americans use sexual fidelity as the chief barometer for marital stability. It's as if the couple who never speaks to each other yet never sleeps with anyone else is healthy, whereas the couple who love each other for the long haul yet respect each other's freedom enough to tolerate an occasional dalliance are aberrant and demented.

Forgive me for bringing up the Clintons (I'll be brief), but nowhere is there a more prominent example of a marriage that, in all likelihood, has a lot going for it and yet has ceased to be recognized by a large number of Americans because sexual fidelity is not a component of it. Here is a couple that shares a profound intellectual kinship, a long-standing commitment to a number of social and political issues, and a respect for each other's ambitions, not to mention an obvious love for their child. That kind of dynamic requires being both deeply invested in the other person and allowing that person a long enough leash to pursue his or her dreams and ambitions. It's a delicate combination, and I daresay that most of us would be hard pressed to pull it off.

That's because it just might be easier to not sleep with other people than to honor our partners with more complex and, quite often, richer gestures of love. When we deem physical betrayal the ultimate betrayal, we lessen our accountability for other aspects of our partner's well-being. I always cringe when I hear praise heaped on a long-unhappily married couple in the form of "They can't stand each other, but neither one has ever strayed." One can only wonder what would have happened if they had strayed. Would they have channeled the resentment in a different direction? Would they have realized that they'll always have more love for the person who gets their joke than the person who gets them off? Maybe they would even have discovered that they in fact can stand each other, that the world is not comprised of either/or scenarios but is instead a place where proper perspective can take us a long way. Maybe it would occur to them that, in some cases, having a really great conversation with someone--the kind of conversation you thought you could have only with your husband or wife--might constitute a far worse betrayal than a night of one-dimensional, visceral pleasure in a place that's nothing like home.

Again, this is just conjecture, but I suspect that we make commitments to the people we love for a variety of complicated reasons and that we sometimes have sex with people we don't love for fairly uncomplicated reasons. Despite the fact that we live amid a certain hysteria about sex, the great irony is that, in the end, the physical act, unaccompanied by deeper emotion, is a physical process that's probably less significant than, say, peristalsis (though I'm not a doctor). Most people who have tried it know that, which is why adultery is not all it's cracked up to be.