Some defenders of abortion assert that viability—when an unborn child can survive, albeit with assistance, outside of the womb—marks the point at which the child deserves protection. Before then, abortion is permissible.
But is viability plausible as a criterion for basic rights? Does it affect the moral status of a human being?
The answer to those questions is certainly no. Viability depends on the medical technology, resources, and doctors that are available. Viability changes, then, from one time period to the next, and from one geographical location to another. An unborn child can be viable in one country (where technology is advanced) but become non-viable when moved to another country (where medical care is inferior). These external factors surely do not determine whether someone has a right not to be killed.
Moreover, viability is a measure of a child's dependency. But we are all dependent on other people and things in various ways. Many of us, for example, depend on parents or caregivers. Some people depend on respirators or pacemakers, and premature infants cannot survive without the help of an incubator. More broadly, as philosopher Francis J. Beckwith writes, we are all "nonviable" relative to our environment. Just as a 15-week-old fetus would die if removed from her natural environment (the womb), an adult man would die if removed from his natural environment and placed in outer space. Dependency, in short, has nothing to do with someone's value.
Nevertheless, viability is important, some have argued, because a non-viable child is not just generally dependent but rather dependent on one particular person.* How, though, does the dependence of one human being on another entail that it's permissible to kill the first? Conjoined twins are sometimes "nonviable" apart from the bodies of each other, but they are still valuable persons who may not be killed. As Princeton ethicist Peter Singer (a defender of abortion and infanticide on grounds other than viability) observes:
A newborn baby is totally dependent on its mother if it happens to be born in an isolated area in which there is no other lactating woman or the means for bottle feeding. An elderly woman may be totally dependent on her son looking after her, and a hiker who breaks her leg five days' walk from the nearest road may die if her companion does not bring help. We do not think that in these situations the mother may take the life of her baby, the son the life of his aged mother, or a hiker the life of her injured companion. So it is not plausible to suggest that the dependence of the nonviable fetus on its mother gives her the right to kill it.
Independence does not somehow confer dignity and rights on a human being. The strong and capable do not matter more than the weak and needy. Indeed, the viability argument isn't merely mistaken—it turns basic morality on its head. That's because the unique dependency and vulnerability of some members of the human family call for our special concern and regard. They call for more from us, not less. "Utter helplessness," said the German philosopher Hans Jonas, "demands utter protection." Helplessness is not a rationale for dismembering and killing.
The U.S. Supreme Court has ruled that viability is the point at which government first has good reason to protect the life of a human being. But the Court has never been able to offer any justification (whether constitutional or moral) for that claim. Why not? Because there is none.
* Some who think viability is important acknowledge that it doesn't affect the value or rights of an unborn child, but argue that killing the child before viability is justified on the basis of bodily autonomy. These arguments are addressed elsewhere.