Generally in the argument for abortion I see the idea bandied about that ownership means I get to control the use of the things that I own. I need to add a caveat to this notion: ownership means you get to control the use of the things you own so long as you do not use the things you own to destroy what someone else owns.
For example, you may freely use your guns to shoot targets. You may freely hunt animals that no one else owns. You may not use your gun to shoot me or to threaten me.
…how else [but involuntary servitude or slavery] would you describe forcing a woman to turn her uterine lining over to the use of a fetus (or, rather, a bunch of grown men purporting to act on the fetus’s behalf)? The only thing that could make the use of force here legitimate would be for the fetus, or someone else other than the woman, to own the woman’s reproductive organs. And for anyone to claim that just is to claim ownership over the woman’s body—which is another quick elucidation of what it means to claim that someone is your slave.
RadGeek makes an error here. He says that the foetus could only claim the use of the woman’s organs if the foetus had a claim of ownership in them. That’s not correct.
In libertarian theory, a person may compel a person to fulfill their duties, which includes what happens when person injures another person or places them in danger. The first duty of these two we call the Duty to Restore; the second we call the Duty to Rescue. When a person has acquired one of these duties, it is just to compel them to fulfill it. It it were not just to compel them to do it, they couldn’t be called duties!
Bound up in the notion of duty is the notion that one person may compel another to take particular actions. That means that, if I were to knock someone off a boat who couldn’t swim, it would be just to compel me to take actions to rescue them. If I could rescue them myself, I should take the action of diving in and saving them. If I can’t, I should take the action of dragging them back into the boat, or calling for help, or doing something to rectify the situation.
In all of this there is no claim that the drowning man has ownership over my body. What he does have is a claim on me due to my actions. There is no transfer of ownership here – my body is still mine – but I now have acquired a duty to use it in a certain fashion. My example at the top also illustrates this point: the person who is threatened with a gun by someone else isn’t claiming ownership over the threator’s gun or his body, simply demanding that his rights be recognised.
What this means is that RadGeek can’t use the argument that abortion ought to be outlawed because compelling a woman to carry a foetus to term is slavery. He instead needs to argue that the mother has no duty to the foetus. In light of how foetuses come to be, this is a much more difficult argument.