Someone posted this question in another forum, and I thought it such a great inquiry, I wanted to discuss it here as well. Reposted with permission.
Yeah it's not a logical criterion. It's like saying to allow abortions for those over 40 because they're more likely to have chromosomal abnormalities. I'm prochoice because embryos don't have minds and it doesn't need to be more complicated than that except in allowing it even after a mind exists (which is late) to save the mother.
Why is there even a distinction between the categories of "rape" and "incest" when it comes to exceptions for prohibitions on abortion? Why is incest not catalogued under rape, since both are forcible crimes against another that cannot be consented to by the victim?
Incest is not automatically a forcible crime. In reality, two related adults can and have legitimately given consent. If you talk about legal minors, then by law consent cannot be given, whether they are blood related or not, which is part of your point. Even if you want to call coercion between adults, that too is illegal regardless of blood. Again part of your point. But you cannot claim that all consent between adults is coerced. You would need to prove that statement.
WHY should there be exceptions for either rape or incest ? Abortion in the case of rape or consensual sex is EXACTLY the same, same procedure, same outcome. Why do some people think a "life" that came about due to rape is less "precious" than one that came about due to consensual sex???
If we made an exception for incest, there's always the possibility a woman might specifically decide to sleep with her brother (rather than some other man in general), knowing that if any pregnancy resulted she could always get an abortion.
I was going to point out the blatant "Slippery Slope" fallacy, but you just decided to go straight to jumping the shark...
Well, this is a concern in general if we start making exceptions. The existence of those very exceptions could start driving women in those directions. (And it is probably the primary explanation why they never created an interracial exception in the 60s, when abortion was first becoming a thing, though that's a different topic)
We could create all sorts of extreme ideas, but the chances of a woman committing consensual incest for the ability to have an abortion is in the ridiculous neighborhood.
This is ridiculous! Your premise says that women have sex because they want abortions. Are you crazy? Most normal people are not sexually attracted to their siblings.
Technically not true. It isn't being siblings that causes the aversion. It's growing up in close proximity to each other. It is why arranged marriages in India where the promised bride ends up living with the parents of and the promised groom have issued (part of the studies that provides evidence of the effect), and why siblings who have grown up apart never knowing each other can meet and marry, and have kids. It is an aversion that develops based on proximity, not genetics. There is actually nothing abnormal about siblings being attracted to each other absent said situation. The situation occuring might be unusual, but the attraction is normal in such a case.
Myth. No one has been able to prove such a thing in any kind of study. And if scent was the factor then the siblings who have been raise apart from each other, never knowing each other, would never be attracted, marry and have kids. Yet it has happened and been documented.