I was reading the comments at one of PZ’s posts when I thought of this:
1. Anti-abortionists often ask the rhetorical question, “What if your parents had chosen to abort you?” to implicitly assert that abortion is wrong because a hypothetical past abortion would result in the non-existence of a fully sentient person in the present.
2. Many people are the product of premarital sex.
3. If the parents of these people had chosen premarital abstinence instead of having sex, they would not exist, therefore hypothetical past abstinence would result in the non-existence of a fully sentient person in the present.
4. Therefore, by the same logic, abstinence before marriage is immoral. And yet, belief that abortion is immoral quite often coincides with a belief that premarital abstinence is a moral obligation.
Of course, the “logic” is absurd and relies on a variation of the Historian’s Fallacy, viewing past decisions as if the participants had the same hindsight a person from the present does, instead of judging the decisions based on the information available to the people at the time they made their decisions. We do not have the luxury of being able to see into the future to see which sex acts will result in the next generation. This is the real world, not Star Trek: we don’t have people from the future popping in to inform us which decisions are the “right” ones.
All I know for sure is that the past and present contain real people. The people of the future are on much shakier ground. If the future’s fixed, the question is moot, since there’s nothing that will prevent them from becoming real. If it isn’t fixed, why should one possible future person have superior rights to another possible future person?
If the future isn’t fixed, every decision, not just abortion or contraception, has an impact on which future is realized. This would mean that if abortion is “murder” because it prevents a future person from developing, so would seemingly inconsequential decisions that end up doing the same thing. Staying home on a Saturday instead of going out and unintentionally meeting the woman of my dreams and thus potentially raise a family would have the same sort of consequences for potential people as aborting them. Even if you enter explicit intention into it, it gets into the problem in the opening of this post: Abstinence would be “murder” because it’s an act that would obviously prevent the development of potential persons.
Of course, a big part of the main debate is about whether zygotes/fetuses/embryos are “persons” or not, or about when in development they become persons, but that’s a different argument for a different post. This one’s specifically about the fallacious rhetorical value of the “potential person” argument.