Two of your friends are dating. You know without a doubt that one of them is cheating on the other. Should you tell the person who's being cheated on about it?
If your friends are actually married should you tell the person who's being cheated on about it?
I know a lot of the time it's more complicated than just 'yes' or 'no' but I want to know generally how you think something like this should be dealt with. I'd love to hear about the only ifs and unlesses and such in comments, though. And, no, I'm not seeking advice for a situation I'm in personally. Two different friends both told me similar stories about things like this today and they handled it in opposite ways and now I'm curious about what a wider selection of people would do.