It is important to tie the pro-choice violinist analogy back to Marquis's pro-life future like ours argument.
If many pregnancies are analogous to Thompson's violinist analogy, then Marquis is wrong. Marquis may be right that it is prima facie immoral to kill a fetus, but in many cases a mother's right to determine what happens in and to her body trumps what right, and in those cases abortion is not immoral.
In effect, Thomson is rejecting the following claim made by Marquis: In order for the mother's right to self determination to override her obligation not to destroy the fetus, the loss she suffers if she remains pregnant must be greater than the loss suffered by the fetus if it is destroyed.
Thomson seems to intend the violinist analogy to cover the case of pregnancy by rape.
However, she offers a challenge to those who say (a) in general abortion is wrong because a fetus is a person with a right to life and (b)_ abortion in the case of rape is morally permissible.
She writes,
Can those who oppose abortion on the ground I mentioned make an exception for a pregnancy due to rape? Certainly. They can say that persons have a right to life only if they did come into existence because of rape or they can say that all persons have a right to life, but that some have less of a right to life than others. In particular that those who came into existence because of rape have less. But these statements have a rather unpleasant sound. Surely the question of whether you have a right to life at all, or how much of it you have, shouldn't turn on the question of whether or not you are the product of a rape.
So if we read Thomson as if she were responding to Marquis, her challenge would be something like " a fetus still has a future like ours even if it was created by way of rape. If the central reason that the abortion is wrong is that it deprives a being of a future like ours, how can we allow abortion in the case or rape but not also allow it in other cases?
