Instead of arguing whether or not the fetus is a person or when life starts she grants the fetus temporary personhood for the sake of the argument.
She makes the distinction between an acorn and an oak tree. An acorn has the ‘potential’ to be an oak tree but is not considered one. Similarily a fetus has the potential to be a person, but is not one yet.
She argues that there are two prima facie moral truths at stake:
1) Every person has the right to life (the fetus has been granted personhood for the argument)
2) The mother has a right to decide what happens to her body
One might presume that the life of a person(1) is most important, but Thomson intends to show that special circumstances of a pregnancy where the life of the mother is in danger make the life of the fetus less important than #2
The Violinist Analogy:
Imagine that someone was plugged into unwillingly to use your kidneys or whatever in order to survive. You were an unwilling participant. You have the ability to unplug the person at any time, but if you do it will end the life of that person because they are unable to live unplugged. Surely #1 is a moral consideration here, the life of the violinist plugged into you is of moral value and would be considered immoral to unplug him. Your right to your own body, #2, is being violated but it does not outweigh the moral value of #1. (There is much to argue with this, but we will grant it truth just because it is a maybe)
If you change the scenario and make it that if you don’t unplug the violinist that you will die. Now not only is your right to your body being violated (#2) but also someone is forcibly taking your right to your own life, violating the moral principle laid down in #1. Thomson says that you can’t justify violating two moral principles in order to keep one.
unplugging the violinist = is a moral bad in that it violates #1, everyone has a right to life
Taking the life of the unwilling person plugged into the violinist = is a moral bad on both #1 and #2. It takes the life of the person plugged in while at the same time violating #2 by not allowing someone to decide what happens to their body.
“If anything in the world is true, it is that you do not commit murder, you do not do what is impermissible, if you reach around to your back and unplug yourself from that violinist to save your life.”(94)
If you compare this analogy to abortion for the sake of the mother, then surely the mother has the right to defend her own life against someone forcibly trying to take it. Or in other words, if the life of the mother is in jeopardy if she carries the fetus to term then she should have the right to opt for an abortion to save her own life.
She then talks about what right to life the fetus has and modifies #1. One may have the right to life, but this does not entail that everyone has the right to everything that they need and that we ought to provide it for them. For example, if someone I don’t know somewhere I don’t know ‘needs’ a kidney to survive, I have no moral obligation to give him that kidney. It might be very kind of me to do so, but nobody has the right to hold me down and take my kidney.
The burglar analogy:
“If the room is stuffy, and I therefore open a window to air it, and a burglar climbs in it would be absurd to say, “Ah now he can stay, she’s given him a right to the use of her house- for she is partially responsible for his presence there, having voluntarily done what enabled him to get in, in full knowledge that here are such things as burglars, and that burglars burgle.” It would be still more absurd to say this if I d had bars installed outside my windows, precisely to prevent burglars from getting in , and a burglar got in only because of a defect in the bars…after all you could have lived out your life with bare floors and furniture, or with sealed windows and doors. But this won’t do – for by the same token anyone can avoid a pregnancy due to rape by having a hysterectomy, or anyway by never leaving home without a (reliable!) army.”(97)
She wraps up her position by stating that she thinks that there are circumstances where an abortion is morally permissible but that there are also situations where it is not especially if the reason for an abortion is not because there is any great burden being placed upon the mother. “It would be indecent in the woman to request an abortion, and indecent in a doctor to perform it, if she is in her seventh month, and wants the abortion to avoid the nuisance of postponing a trip abroad.”(100)