The landmark Roe v. Wade decision, handed down by the United States Supreme Court in 1973, touched off a divide deep within the American culture that shows little signs of healing. The reason is not necessarily that people have intransigent views when it comes to abortion. Instead, the issue is genuinely hard to grapple with, even from a moral standpoint, as Harvard Law Professor and bioethicist Glenn Cohen explains.
The first question we face when deciding whether abortion is immoral is this: are fetuses persons? That may seem like a straightforward question, but determining personhood requires understanding the distinction between a person, a human being, and being alive.
Certainly not all things that are alive are persons. A dog, for example, is very much alive and very lovable indeed, but not a person. As simple as this distinction seems, it has its detractors. The philosopher Peter Singer, for example, says that distinguishing between what is human life and inhuman life is an example of speciation — an act of discrimination that is ultimately logically untenable (and we should therefore abandon it).
According to Cohen, some scholars say that stem cells and embryos are human beings, but not persons. They are made of human being stuff but they do not have the moral and legal rights — namely, the right of inviolability — that we accord to individual persons.
Those who believe the granting of rights is more a political act than a natural one may look toward what Cohen calls a "capacity 'x'," i.e. some other quality that more accurately defines what a person truly is. Examples of such a capacity 'x' include experiencing a continuity of identity, or possessing self-knowledge. While these qualities form more naturally than the granting of political rights, they open the door to difficult-to-justify actions like infanticide (since the infant brain is insufficiently developed to have the concept of an identity, or to articulate self-knowledge).
If one decides to stick with a definition of "person" that is determined by the existence of moral and legal rights, thinkers such as Judith Jarvis Thomson point out that the rights of a mother countervail — she is a person, too, after all. Thomson's famous thought experiment, "the famous violinist" has become perhaps the most recognizable philosophical defense of abortion.
Glenn Cohen's book is Patients with Passports: Medical Tourism, Law, and Ethics.