We can now examine the way in which those who adopt the liberal or “pro- choice” position will respond to the conservative or “pro-life” argument as it has just been spelled out. The second premise should not be a subject for controversy, given our definition of abortion. Nor does it seem likely that the fourth premise will be attacked on the ground that the fetus is not innocent. How could a fetus be guilty of anything?
This leaves three strategies for the liberal: (1) Further modify the moral principle in the first premise to allow more exceptions. (2) Deny the third premise—that the fetus is a human being. (3) Oppose this conservative ar- gument with a different argument based on a different moral principle.
FURTHER MODIFICATIONS. Even if it is agreed that abortion is justified when it saves the mother’s life, we still need to ask whether this is the only excep- tion or whether abortion is justified in other cases as well. Many pro-life con- servatives admit that abortion is also justified when the pregnancy results from rape or incest. It is not easy to see how to modify the moral principle against killing to allow an exception in cases of rape and incest, so this exception is controversial. We will return to this issue later. But even if exceptions are made both for life-threatening pregnancies and for pregnancies due to rape and incest, the range of morally permissible abortions will still be very small.
Pro-choice liberals can, however, argue for a wider range of morally per- missible abortions by extending the self-defense exception. It can be argued that a woman has a right to defend not only her life but also her physical and psychological well-being. Liberals can also argue that the exception of rape shows that abortion is allowed when the woman is not responsible for her pregnancy, and this might include cases in which the woman tried to prevent pregnancy by using contraceptives. Granting exceptions of this kind does not provide the basis for an absolute right to an abortion, but it does move things away from a “pro-life” position in the direction of a “pro-choice” position.