Argh. I hate ambiguously worded questions.Do I believe in it? Well, the concept exists, so yeah I believe in the concept.
Do I believe that humans are capable of it? When it comes to SEX? In general, no.
It may sound sexist or as if I am man-bashing...but if we look at it from an evolutionary standpoint, it's just part of the male DNA, his biological imperative, to spread his spunk as far and wide as possible. And while females tend to invest more time/energy into their offspring and (according to biologists) therefore only need the one male, I think it makes a heck of a lot more sense for there to be multiple partners (and thus multiple possible fathers) to assist in providing for the family unit.**
(Or, that could just be my kinky brain trying to promote a more widespread acceptance and/or adoption of polyamorous polyandry. *wink*)
Now, that's not to say that I don't know a dozen people who've been married to (or dating exclusively) ONE PERSON for years upon years and neither of them have strayed (or so they say).
Unfortunately, for every ONE of them that I truly believe, I know THREE others who just don't have it in them. I gotta say, I might be one of them.
To me, sex is sex; it's a biological function.
But love? Love is what matters.
(**And of course this only applies to heterosexual relationships. I'll leave the homosexual argument up to someone who's had more experience with it than I have...because I know not everyone believes, like I do, that sex is sex and the parts don't matter.)*********************
That being said:
Your challenge flisters (if you choose to accept it) is to crawl into the mind of your favorite character (or the one you write most often), ferret out exactly what you think they believe, and post me comment fic AS THEM in order to give me their answer!