Is adultery really immoral? The act itself is mostly legal, so why can't it be mostly moral? I'm a male bachelor, so I can only argue from my point of view. Adultery is a simple biological urge that manifests itself onto two persons, one or both of whom are married. Marriage today is becoming more and more a simple legal contract, routinely terminated and routinely redefined by judges and plebiscites. The ease with which marriages can be terminated either on paper or in practice is just a reflection of the fact that people often change in their feelings towards one another--love fades within marriage and sometimes erupts outside marriage. Making it with a married woman can be very thrilling and the same woman would not be equally exciting if she were single; the supposedly unavailable is always more desirable than the easily attainable. Married women accept advances because their husbands can no longer give them excitement, romance or adventure, so why not a net utilitarian gain for two people, and no change for the unknowing cuckold?

Let's stipulate: adultery isn't always immoral. You're pitching the idea that it's usually not immoral ("mostly moral," as you put it.) Your argument, however, doesn't seem to me to be strong enough for that conclusion.

Start with something obvious: when people get married, they make promises to one another. Typically, one of those promises is a promise of faithfulness. Not all promises are binding in all circumstances, but in general promise-breaking isn't morally trivial. And encouraging people to break promises isn't trivial either. But set that aside.

Let's suppose that adultery is the result of a biological urge, as you say. Since morality often calls for us not to act on our urges, that doesn't tell us much. Your legal/sociological analysis strikes me as a bit thin, but I'm more worried about this: "Making it with a married woman can be very thrilling and the same woman would not be equally exciting if she were single; the supposedly unavailable is always more desirable than the easily attainable. " By analogy, some thieves might be attracted to the idea of stealing things that are hard to steal. Psychologically interesting, perhaps, but not relevant to whether it's okay to steal those things. You seem pretty confident about why married women (what about married men?) commit adultery. I have no such confidence, but whether you're right or not, your parting thought strikes me as unconvincing: "why not a net utilitarian gain for two people, and no change for the unknowing cuckold?" This raises a couple of points.

First, the fact that the adulterers get pleasure from what they do doesn't carry any moral weight if it happens that what they're doing is wrong. It's a problem with crude versions of utilitarianism that they don't make room for this point. Although the disanalogies matter, if a Mafia enforcer enjoys beating up his victims, that doesn't make things better than they'd be if he did it with a heavy heart.

Now you might reply that there's a big disanalogy: the "cuckold" is none the wiser, and so isn't harmed. That's often just wishful thinking. It suppose that people can just wall off their behavior in one circumstance from what goes on in nearby circumstances. If one partner in a relationship is cheating, there are often signs that the other partner picks up on, often to his or her distress. And if the couple have children, things are even more complicated.

So one thing that can make adultery bad is that it hurts other people. If you make advances to a married woman, you're running exactly that risk. And if you're in it just for the "excitement," it may well be that that's not really what's going on with your paramour; you may end up hurting her too. The attitude you describe, frankly, sounds manipulative and callous. It doesn't sound like it would pass the test of asking honestly how you'd feel if you were the cuckold.

Marriages are complicated. Relationships are complicated in general. I'd suggest that the right way to think about adultery isn't to focus on marriage as such. It's to pay attention to the complications, to drop the illusion that no one is going to get hurt, and to keep in mind that if I'm asking whether what I'm doing is morally acceptable, it's not all about me. It's about the whole tangled web. Nothing I've said shows that adultery is not generally alright, but I'll admit that I'd be really surprised if it turned out that way.

Because, for every X, there is a philosophy of X, it should come as no surprise that a well-known philosopher has written a book on this subject! I refer you to Richard Taylor's Having Love Affairs (Buffalo: Prometheus Books, 1982), isbn 0-87975-186-X, http://www.amazon.com/Having-Love-Affairs-Richard-Taylor/dp/087975186X

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