Legalizing Incestuous and Polygamous Marriage

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In this post, I am continuing to look at the fifth policy objective in Sean Faircloth's new atheist strategy - marriage equality.

One of the arguments we hear against gay marriage goes like this:

If we accept these arguments in favor of gay marriage as valid, we must also permit incestuous and polygamous marriages that involve consenting adults. Obviously, legalized incestuous and polygamous marriage is unacceptable, so gay marriage must also be unacceptable. You must vote against gay marriage or find yourself surrounded by incestuous and polygamous marriage.

Now, I can interpret thus argument in one of two ways.

Interpretation 1: So, you are telling me that you believe legalized incestuous and polygamous marriage will significantly improve the quality of some lives and do no harm to anybody. Yet, we must prohibit it nonetheless and eagerly do violence to those who would practice it.

Why? This sounds like a policy of harming others simply because one has a gotten into the habit of or developed a fondness for that which harms others.

Interpretation 2: If we legalize gay marriage, we must legalize incestuous and polygamous marriage. However, these others come with all sorts if harms we must avoid. Therefore, we must not legalize gay marriage.

Against this, the question is: Why not use these harms as reasons to keep incestuous and polygamous marriages illegal? Nobody claims that the fact that homosexual marriage involves consenting adults is a sufficient reason to permit such marriage, only that it provides a relevant difference between gay marriage and marriage between adults and children or adults and animals.

On the issue of polygamous marriage, perhaps this should be legal. They have one significant advantage over the "traditional family."

With a traditional family - one breadwinner, one caregiver, and children (or elderly parents, or those for whom care is needed) - if anything happens to either the breadwinner or the caregiver the results are much likely to be catastrophic. If we increase the number of breadwinners and caregivers, we can reduce the chance of a catastrophic result. There is always a "backup" to fall back on.

On the other hand, managing so many personalities may well be impossible. It may require an unhealthy level of submission to a ruling patriarch that robs the other members if their personality and autonomy, or disintegrate into factions. I will have to leave it up to experts to answer those questions.

On the issue of incestuous marriage, I would argue that we do have good reason for a prohibition - a reason that does not apply to gay marriage.

Before I go into this objection, I want to discuss two objections to incestuous marriage between consenting adults that fail.

The first is the genetic argument. This argument claims that a prohibition against incest is justified because it reduces the chance of genetically deformed or defective children. Incestuous reproduction increases the possibility if realizing recessive genetic traits. These are most often harmful. This is because it is more likely that a sibling shares one's recessive trait than a member of the population at large.

The problem is that we no longer need to rely on a prohibition on incest to reach this objective. We now have much more effective ways to determine if couples risk producing offspring with genetic defects. If this is a valid argument, we should now give up the crude "incest" test and use more scientific genetic tests. We can require that couples undergo genetic screening, and prohibit sex between those who are judged genetically incompatible. Where these genetic tests determine that siblings share no recessive traits, then they can be allowed to marry. Whereas non-siblings that share recessive traits can be prohibited from marriage (or sex).

Furthermore, the genetic argument provides no objection to incestuous gay marriage or incestuous marriage among sterile family members.

The other failed argument against incestuous marriage says that evolution has given us a disposition to avoid incest that manifests itself culturally as an incest taboo - social and legal prohibitions on incest.

However, an evolved disposition to avoid something is not an evolved disposition to do violence to those who do not avoid it. And an evolved disposition to do violence to those who do not avoid something is not a justification for doing violence to them. The inference from, "I have evolved a disposition to do violence to people like you," to "You deserve to be treated violently" is wholly invalid - even if the first part happens to be true. In the case of an incest taboo, the first part itself has not been demonstrated, even if we have a natural aversion to incest.

So, these common objections to incest do not work.

However, there is an argument that does work.

Promoting a society-wide aversion to incest is almost certainly an effective tool for preventing the sexual abuse of children.

People act so as to fulfill the most and strongest of their desires, given their beliefs. We know that manifestations of human desires cause a certain amount of childhood sexual abuse - we have observed physical evidence that this is the case. Now, take our current set of human desires and remove from it the aversion to incest - holding all other desires constant.

A very likely result - in fact, I would say a certain result - of this would be an increase in incidents of child sexual abuse. Given our current manifestation of desires, the aversion to incest is preventing some incidents of child sexual abuse that would otherwise take place in its absence. A great deal of sexual abuse is perpetrated by family members, and a great deal of sexual abuse that does not occur may be attributed to an aversion to incest.

Our interest in preventing childhood sexual abuse gives us reason to promote an aversion to incest. In this respect, evolution may have given us the raw tools to work with, but evolution does not justify its use. Nor does eugenics. It is the prevention of childhood sexual abuse that justifies its use.

One of the social tools for promoting this aversion - as well as one of its effects - is a social intolerance of incestuous marriage. Permitting these marriages would require reducing the social aversion to incest - telling community members that it is okay and nothing to feel bad about. Whereas a prohibition communicates to society at large that it is something to feel bad about, which promotes this aversion, and reduces incidents of childhood sexual abuse.

This objection does not apply to gay marriage because the relationship between gay sex and the sexual abuse of children is exactly the same as the relationship between heterosexual sex and the sexual abuse of children. There is no relevant difference between the two - and, thus, no moral difference stemming from this objection to incestuous relationships.