One of my regular correspondents comes back with this:

Didn’t like that other guy’s lack of logic ok, how about this:
I’m against incest laws simply because those people in incestous relationships are citizens, human beings, taxpayers etc. I don’t have to dig everything they do to recognize this fact.
Assuming the incest is between Adults, you in favor of repealing incest laws? If your an 18 man/woman and consent to doing your mother/father or sister/brother or daugther/son…neiter of you are a victim. Since having sex with children is already illegal, should we allow brothers and sisters to have a go at it. Least you’d know what your children would look like.

My response: As a matter of logic this is a tougher one, I confess. First, I would say that whether legal or illegal, I think social stigma and expressions of disgust should still and always apply to incest. I also think that if we repealed the incest laws we wouldn’t see a spike in brothers and sisters getting it one, precisely because those cultural controls are still there. I sincerely doubt that there many siblings out there cursing the government from keeping them apart with those tyrannical incest laws. Indeed, this is why I never thought it was all that necessary to fight sodomy laws — they don’t do much and are almost never enforced. Also, Incest is not a widespread vice. And if keeping the incest laws on the books keeps it that way, that’s fine with me.

There are other factors. Incest can lead to horribly handicapped children. I’m opposed to cloning right now for among other reasons any human cloned child will undoubtedly be deformed. Something similar would apply to incest.

But ultimately, I’m not sure I have to be 100% consistent here. Cultures and values should be informed by reason but they don’t have to be completely bound by it either. Many of our customs would seem highly irrational to outsiders and some of them may in fact be irrational. That doesn’t mean that we should abandon them. Chesterton noted that the merely rational man will not marry and

the merely rational soldier will not fight. For example, I’m at a loss to tell you why exactly I favor laws forbidding consensual incest between homosexual brothers, but I am.

I will say the best pragmatic argument in favor of sodomy laws was from a Marine reader. He noted that sodomy laws are useful to prosecutors as “lesser included offenses.” If you can’t prove a guy did something really horrible, you can still get him on the lesser offense of sodomy (this is also one of the advantages of drug laws by the way. A lot of these poor “non-violent drug offenders” plead down to drug trafficking in order to avoid murder or assault charges). This is a perfectly legitimate practical point. But standing alone, I’m not sure I think it justifies keeping a law on the books which shouldn’t be enforced by itself.

But look, it’s Friday night and we’re not in prison, so I don’t have to think about sodomy any more if I don’t want to. So I’m done with this for now.