What would you do?

[promethean75]

When faced with questions like this, i aks myself WWJD, obviously.

[LuckyR]

The reason is in the OP. It would destroy the family.

Your reasoning that a friend should tell a friend because the friend is a true friend, is rather circular.

So, you think it's preferable that a family should be destroyed to affirm your notions of true friendship?

Is ending a relationship with a person you don't want to be with, a bad thing? The friend didn't "destroy" the relationship, the cheater did. Talk about blame the messenger. Keep your eye on the ball.

Sort of like if the doctor doesn't tell you that you have cancer, you're fine. Illogical.

What kind of "friend" let's their friend continue a relationship that's fake? No friend of mine.

You're stepping outside the parameters of the OP and adding subjective information to expand your point of view, which is fine as an expression of who you are, but may not apply as a principle relevant to the parameters of the OP.

Friends are not licensed to meddle in people's lives. Doctors are licensed to do that.

Sorry Charlie, you're not the OP, so your interpretation of the "parameters" is no more valid than mine.

The OP clearly feels that friends are "licensed" to give friendly advice, otherwise why posit the question at all.

[Iwannaplato]

Doesn't matter.

well, that last point matters to me and then to the others, if they were real.

That's all you've got to work with in unveiling a definitive principle.

Oh, what we've been given to work with entails we are a clairvoyant, telepathic para-deities...
(viewtopic.php?p=714419&sid=1ffca434beec ... 09#p714419)

Adding more doesn't help.

More is already built in, a lot more. I'm not adding, I'm pointing at the rest of the iceberg, below the water.

One can certainly unveil a principle. But it wouldn't be connected to my world. It's be like a Dungeons and Dragons principle. Interesting, perhaps fun.

Likely misleading in real world contexts.

(and I suppose I am also subtracting. Some things in the OP look like information, but they're not really. 'destroyed' is an example.)

[nelmasri]

Thank you for all who replied to the post. I wanted just to clarify that this is a thought experiment so you can make your own assumptions about the situation. What I am proposing in the thought experiment is that:
(a) You are very close to your friend and you can tell him about this
(b) You are almost sure that this cheating act will never happen, because your friend's partner was drunk [or make any other assumption that makes sense]
(c) If your friend know this, most probably, he/she will never tolerate it and they will end up by getting a divorce

[LuckyR]

Thank you for all who replied to the post. I wanted just to clarify that this is a thought experiment so you can make your own assumptions about the situation. What I am proposing in the thought experiment is that:
(a) You are very close to your friend and you can tell him about this
(b) You are almost sure that this cheating act will never happen, because your friend's partner was drunk [or make any other assumption that makes sense]
(c) If your friend know this, most probably, he/she will never tolerate it and they will end up by getting a divorce

I assumed as much (that you'd be "almost sure" about a recurrence, and that "most probably" there'd be a divorce), in other words there's no magical certainty, just routine assumptions. Thus I stand by my original answer.