I, like Mr. Alura, am no christian. In fact I probably fall under the agnostic category. My feelings on the subject lean more toward seeing the stories relayed in the bible as allegorical. Much like Aesop, the stories are designed primarily to reinforce social mores and promote common sense. 4,000 years ago in small isolated villages, where sex was primarily for procreation (See Abraham bedding his wife’s slave to produce an heir) sexual monogamy was a necessity. Even if procreation wasn’t the only motivating factor, without birth control, it was quite often the end result. It was to the benefit of the tribe to know exactly whose offspring belonged to whom. You wouldn’t want have brothers and sisters creating branchless trees so to speak.
Additionally, in that time, marriages were more of a business contract than an enterprise based love, desire and mutual respect. Almost all business partnerships have built in non-compete clauses.
It would appear to me that this commandment, adultery, is designed solely to preserve the family unit and the stability of the community. In my observation of the good people on this board and the few that we’ve met in person is that their extramarital adventures have posed no threat to either their “family unit” or to society as a whole. In fact, with a greater than 50% divorce rate in this country, it would appear that the communication and trust needed to engage in this lifestyle might actually be serving a greater societal good.