Are we our “brother’s” keeper? Does what affects one affect us all?
I place the moral responsibility primarily on the cheater. They are the one with a primary relationship. If they look for someone else, that person has no responsibility to the person who is being cheated on. If that person is a friend, then it is a different story. Then they do have a responsibility to their friend, and if the affair goes on, the cheatee is being betrayed by both people. Of course, when the shit hits the fan, the boyfriend is usually the one to go, and the friend will be kept. Friends, it seems, are much harder to lose.
Suppose the other person does not know that their lover has an SO at the beginning, but finds out later. Should the “other” back out? On the one hand, it would probably be causing the least harm to back out in favor of the existing relationship. On the other hand, the “other” has a right to happiness, too.
I guess this comes down to why you think the cheater is cheating. Most people, it seems to me, think that the cheater is just out for some extra fun, or they are morally deficient. Others believe that no one would cheat if there were no problems with their SO.
However, people mostly seem to believe that if the primary relationship is bad, then the cheater should break off the relationship before taking up with the new person. In an ideal world, this seems like a good idea, but the world isn’t ideal. People don’t know whether if they break off they will ever find someone new. It makes more sense to find someone new and then break off the old relationship—tactically speaking.
Personally, I think morality works on a basis that is pretty much like the way the economy works. It is a way of helping people figure out what they want. Except that while it feels ante hoc, it really is post-hoc—based on lessons learned before.
In the moral economy, we are looking at a kind of Willsian greatest good calculation. Usually, the current relationship has more at stake than the new relationship. Based on that, the responsible thing is to save the existing relationship. On the other hand, the new relationship may have more potential good than the existing relationship. Which good is larger? Well, no one can tell since we can’t see the future.
For the “other” it is clear that there is more good in a future relationship, except if the existing relationship includes their friend. Then you have to ask if a lover is worth a friend. As I said before, that’s a tough calculation, but it usually ends up in favor of the friend.
But if there is no friend of the “other,” then I think they are off the hook. The moral responsibility lies purely on the cheater. The cheater obviously wants no trouble. They want to have their cake and eat it. If they are caught, then it is hard to say where their loyalty will go, but if there is a lot more at stake with the existing relationship, they will probably try to repair that. If not, they may go with the “other.”
Except that in our society (US, I mean), there is such a moral outrage at a cheater, that the cheatee is strongly encouraged never to let the cheater back. No one ever understands why the cheatee gets back together with the cheater. After all, they were so wronged. Some even look down on the cheatee for letting the cheater come back.
I think people underestimate the importance of children, family and resources on people. Couples are very reluctant to give up things they have built for all of their married lives.
Of course, to get back together and stay together, they would have to solve the problems that led to the cheating. If that doesn’t happen, then, as the saying goes, “once a cheater, always a cheater.” But, with counseling and hard work by both people in the couple, I don’t think that saying is true.