Last month on this blog we spent a good deal of time discussing the proposed constitutional amendment in Mississippi to change the legal definition of personhood to include fertilized human eggs. The amendment would have outlawed all abortions (including those resulting from rape or incest), many forms of birth control (including IUDs and morning-after pills), and embryonic research. Fortunately, it was rejected.

Yet while it might seem like common sense to most people that fertilized eggs are not persons, such thinking has important implications for the logic of the abortion debate, according to philosopher Gary Gutting:

The basic problem is that, once we give up the claim that a fertilized egg is a human person (has full moral standing), there is no plausible basis for claiming that all further stages of development are human persons.  The DNA criterion seems to be the only criterion of being human that applies at every stage from conception to birth.  If we agree that it does not apply at the earliest stages of gestation, there is no basis for claiming that every abortion is the killing of an innocent human person.

Those convinced that abortion is murder can, of course, maintain that this entire line of argument merely shows that we must hold that the fertilized egg is a human person: abortion is always wrong and it wouldn’t be if the fertilized egg weren’t a person. But what the Mississippi referendum showed was that many of those strongly opposed to abortion do not believe this.  They were not willing, for example, to forbid aborting pregnancies that result from rape or incest or that are necessary to save the mother’s life.  Many were also unwilling to charge fertility doctors who destroy frozen embryos with murder or to forbid after-fertilization birth control devices such as I.U.D.’s.

Couldn’t proponents of a personhood amendment allow exceptions for such cases?  Yes, but this would destroy the logic behind the amendment.

You can read Gutting’s full post on the New York Times’ philosophy blog here.