Email question of the day:
"So I take it you have no argument against marriage between two consenting adults, even if these adults are, for example, brother and sister?"
It's the question of the day because it sent me off to do a bit of research on incest in order to challenge/re-affirm my position. (Freedom won again...)
I also discovered a curious thing about Rhode Island law...they have an exception to incest laws that allows "any marriage which shall be solemnized among the Jewish people, within the degrees of affinity or consanguinity allowed by their religion".
My response to the questioner:
While I personally find the concept of marrying a sibling, etc. rather "icky", there are lots of things that I find "icky" that aren't necessarily immoral and that society has no business restricting. My aversion is something that most of us experience and it's known as the "Westermarck effect" but that's not the case for everyone.
There are certainly biological reasons to avoid inbreeding, but marriage isn't necessarily about procreation. There are also psychological issues that surround taboo relationships (both contributing psychological issues and psychological issues that result from such unions) but we have to be very careful to distinguish between issues caused by societal disdain for something (as was/is the case with inter-racial marriages) and psychological harm that is intrinsic to the relationship (a daughter raised segregated from societal influence in order to 'brainwash' an incestuous spouse).
I think there's a compelling argument that we should generally discourage incestuous marriage in order to minimize the risk of birth defects and psychological trauma, but that we are probably not justified in prohibiting those unions as a matter of law. I'm also convinced that this issue isn't compelling enough to spend much time on...as the percentage of the population interested in such a relationship is negligible.
Our ability to discern the moral evaluation of something like incestuous marriage is restricted we just don't have enough information and there are too many possible scenarios. It may be that the unions are, in and of themselves, detrimental to the couples and to society - or it may be the case that there's no significant harm. I'm not convinced that we have enough information to make any such determination, but I haven't spent any significant time studying the subject. Until such time as we have compelling evidence (and not just a visceral aversion), I'm not sure that I can support laws against such marriages but I'm in favor of discouraging it by education and investigating such relationships to ensure that we have true, informed consent.
Finally, there are a number of scenarios where people meet, fall in love and later learn that they are siblings or otherwise closely related. I'm of the opinion that it would be more immoral to prevent their marriage that to allow it...and that colors the entire spectrum of possible incestuous relationships...especially when you consider that some people get married, lead happy lives and find out about their kinship years later.
It may be the case that this is quite often a morally neutral issue along the lines of a victimless crime (a term I'm not fond of, but fits as we often criminalize things which are victimless). As a matter of personal freedom, unless someone can demonstrate clear harm, I don't see a compelling reason to disallow it.
I've since done a bit more thinking and I'll amend the above a bit...
Re-reading that, it looked like I was in favor of discouraging a loving relationship between people who happened to be related and that's not the case. The education comment was intended to address the real risks and not be a pronouncement about whom you should/shouldn't love or marry.