Pro-life
We can begin to understand this problem if we reconstruct the main argument against abortion, using the method sketched in Chapter 5. Most opponents of abortion call themselves “pro-life” and base their position on an appeal to a moral principle involving the “right to life.” Of course, most op- ponents of abortion are not opposed to killing weeds, germs, or even fish. What they have in mind, then, is probably a principle such as this:
It is always morally wrong to kill a human being.
This principle by itself does not rule out abortion. To reach this conclusion, we need further premises of the following kind:
Abortion involves killing a human fetus.
A human fetus is a human being.
With these premises, the anti-abortion argument will have the following form:
(1) It is always morally wrong to kill a human being. (2) Abortion involves killing a human fetus. (3) A human fetus is a human being.
(4) Abortion is always morally wrong.
This argument is valid and reasonably charitable, so we have completed the first stage of reconstruction.
We next ask if the premises of this argument are true. The second premise is not controversial, given our definition of abortion; but the third premise raises many problems. Much of the debate concerning abortion turns on the question of whether a fetus is a human being. We will examine this question later on. For now, we will assume for the sake of argument that a fetus is a human being. That leaves only the first premise.
Some people—for example, strong pacifists—accept premise (1), but most people who adopt strong anti-abortion positions do not. This comes out in the following way. Many of those who oppose abortion are in favor of the death penalty for certain crimes. Therefore, they do not accept the general principle that it is always wrong to take a human life. What they need, then, is a principle that allows taking a human life in some instances but not in others. In an effort to achieve this, those who oppose abortion could refor- mulate the first premise in these words: