The letter-writer says he is friends with "Jane" and also, secondarily, with Jane's husband "Peter." He writes,
Jane is having an affair with ‘‘Martin,’’ whom Jane has known most of her adult life. I know about the affair because Jane confided in me years ago. In fact, this affair was also a part of Jane’s previous marriage, and Jane confided this to me as part of her divorce from her first husband, whom I did not know. Jane thinks Martin is her true life’s ‘‘soul mate,’’ and I think she may be right. Peter does not know about the affair. If he knew about it, I think he would divorce Jane in a minute.The letter-writer feels vaguely uncomfortable about actively helping Jane deceive Peter, but he's mostly inclined to justify and continue it. The so-called ethicist advises him to go ahead and continue helping Jane deceive Peter, but commends him for bothering to feel guilty about it. Really, how does the mere act of feeling guilty about it help anything if he goes on doing it?
Here is what the letter-writer ought to have done from the beginning: When Jane went through her divorce from her first husband and confessed to the letter-writer that she was having an affair with Martin - who is married - the letter-writer should have realized that it does not make sense to want to count among one's friends a person who cheats on their spouse (with another married person, at that). Why would you want to be friends with a liar who damages multiple people's marriages and puts multiple people at risk of STDs without their knowledge or consent? If you have a spouse or partner yourself - or if you ever might in the future - why would you expect Jane to have any more respect for your marriage than she has for Martin's or her own? Why would you expect Jane to have any more respect for anything about your life than she has for Peter's life or Martin's wife's life?
At this point it's going to be a bit more complicated for the letter-writer to extract himself from the situation ethically than it would have been back then. Still, though, an important part of the solution has to be "Stop being friends with known cheaters!" Being friends with them morally compromises you and gives them the idea that cheating isn't that bad - since, by remaining friends with them, you are indeed conveying the sense that you don't think their behavior is bad enough to make you want to dissociate yourself from them. Have higher standards than that!
Will it be sad to lose a longstanding friendship if your friend starts cheating on their spouse? Sure. But if your friend is not the quality of person who deserves to have you as a friend, you're better off facing that fact rather than continuing to trust a person who has shown themself to be untrustworthy.
And what if your friends go ahead and cheat on their spouses but simply don't tell you about it because they know you won't accept them as friends anymore under those conditions? Well, that means (a) your friends won't morally compromise you by enlisting you as co-conspirators in deceiving their spouses, and (b) your friends won't be able to take comfort in the sense that cheating must not be that bad because they can tell all their friends about it and their friends all go on being friends with them anyway. So . . . that's good.
Also: What right does the letter-writer (or Jane either, for that matter) have to decide for Peter that Peter is supposedly better off remaining in this marriage in which he's being lied to and cheated on, when Peter himself is likely to think otherwise and has not been given the opportunity to decide for himself? This amounts to the letter-writer having a low opinion of Peter, believing that Peter couldn't do any better for himself in the marriage market than to remain married to someone who's cheating on him.
The letter-writer could ask Peter for advice here: Make up a friend, mention him to Peter on a few separate occasions, make him seem believable, then tell Peter you found out that this friend's wife is cheating on him. What does Peter think you should do? If Peter thinks your friend should be told, then I think Peter should be told. Ideally not by the letter-writer, though . . . I would very much prefer that Jane be the one to tell Peter. I would tell Jane, "You need to tell Peter or else I will tell Peter." Jane would not be my friend anymore after this. But that's just fine, because I would have no interest in being friends with Jane anyway.
The ways we react to other people cheating matter. People whose parents cheat are more likely to cheat, because seeing that one's parents cheated tends to create the impression that cheating is relatively more normal, less shocking, less scandalous than one would tend to believe if cheating is something one only reads about in newspaper articles about political scandals. But we form our impressions of what's considered socially acceptable based not only on our parents but also on our friends. This means that friends also have the power to alter our understanding of the degree to which cheating is acceptable or unacceptable. So you're responsible for the impressions you create. And don't you want them to be anti-cheating impressions?
A relationship should stand or fall on its own merits. If it isn't working, leave! But leave when you decide it's not working - don't string someone along for years while looking for someone better. Anyone who's truly better is going to think less of you if you start romancing them while you're in a relationship with someone else. And the person you're in a relationship with deserves to know that it's time to consider themself single at the same moment that you start behaving as if you're single yourself.
And what if you haven't thought your relationship was in bad enough condition to justify breaking up, but you suddenly find yourself attracted to someone else? Three things. First, have enough respect for your existing partner to recognize that you don't know the someone else well enough to be able to fairly compare them, and that the excitement of meeting a new person is likely to create an inaccurate and short-lived impression that the someone else is better than they actually are. Second, have enough respect for the someone else to realize they deserve better than the kind of person who would destroy an existing relationship to be with them. And third, start working on fixing your relationship with your existing partner . . . starting by telling your existing partner what you're feeling for this other person. The way to restore a sense of trust and emotional intimacy is to actually trust your partner and actually allow your partner emotional intimacy. That means you tell your partner whatever you've been hiding. That's the only way to fix things. Candlelight dinners and fancy jewelry and exciting vacations do not create trust and emotional intimacy. Honesty does.