If a fetus is a parasite. . .

This morning somebody made the argument that if a mother doesn't want their fetus, then the fetus is a parasite. Although he didn't explicitly say so, he seemed to think that was some kind of justification for abortion. Even if that's not what he meant to imply, I have seen people who use this is an argument in favor of abortion.

The assumption behind this argument is that the fetus is a distinct organism from the mother. I don't know if pro-choice people think about that when they make this argument. A parasite is a distinct organism that invades another organism, so if you say the fetus is an organism, then you'd have to give up the idea that in having an abortion, a woman is doing what she wants with her own body. She's doing something to a different organism.

Whether the fetus is a parasite or not doesn't have anything to do with whether it's wanted or not. Think of people with body dysmorphic disorder where they are sometimes so uneasy with their own body parts that they try to amputate them. A person will cut off their own leg. Well, the leg isn't a parasite just because it's unwanted and it's taking nutrients from your body or using the rest of your body to stay alive. Your leg is part of your body. The fact that you might not want it is irrelevant.

And a parasite doesn't stop being a parasite just because a person does want it. There's some medical procedure I heard about a few years ago where people intentionally have themselves infected with a worm temporarily. Then there's also leaches, which people use to get the blood flowing again once they've reattached a severed limb. In both of these cases, people want the parasite. But just because they want them doesn't mean they're not parasites.

So desire has nothing to do with whether or not the unborn are parasites. If you define a parasite as a living thing that is using your body to stay alive or drawing nutrients from your body, then your hands are parasites. All of your body parts are parasites. But if you define a parasite as a distinct organism that uses your body to stay alive, then yes, a fetus is a parasite, whether it's wanted or not. That also implies that it's a distinct organism from the mother, and we have to ask the question of what kind of organism it is.

I don't think a fetus can properly be called a parasite, though. Using the body of another organism is a necessary condition for being a parasite, but it's not a sufficient condition. Something more is needed. A fetus is the mother's own offspring. The womb is its natural habitat. Reproduction is the natural means by which humans propagate. So I don't think it's proper call a fetus a parasite. But if somebody does use this move, I'd be sure to point out the implications of it since it does tacitly support the pro-life argument that the unborn is a distinct organism from its mother.