John T. Noonan, “An Almost Absolute Value in History,” in Larry May and others, Applied Ethics: A Multicultural Approach, Prentice Hall, 2011, 5th ed., pp. 430-434.
Noonan describes a basis for a right to life on the issue of abortion. He considers a number of criteria for assigning human status to the fetus. He rejects six but he accepts two such criteria.
Noonan rejects various historical reasons for considering the fetus a human being: 1) ensoulment, 2) viability, 3) impact on adult sentiments, 4) sight, 5) touch, and 6) social visibility.
He notes that Aristotle regarded ensoulment (having a soul) as a mark of humanness, but ensoulment can have different meanings. It may mean one thing to a humanist and another to a theologian.
Viability (ability to live outside the womb) is a problem, since it varies over time and with developing technologies. A complete artificial womb could render viability unworkable as a mark of when an embryo becomes human.
Impact on adult sentiments is also a problem. Some people may feel grief at the loss of an early fetus, but others may not.
Sight and touch (if the fetus cannot be seen and touched, it cannot be perceived as human). Sight is a weak criterion for humanness. People have been regarded as subhuman by racists, for example, because they didn’t measure up to what a “human” should look like.
Social visibility (the fetus is not socially perceived as human). Slaves have been denied rights once they were classified as slaves–that is, less than human)
Noonan accepts the genetic make-up of the fetus as the decisive criterion for humanness. He considers that the sperm and egg also contain human genetic material, but he regards the high probability (80%) that an embryo will naturally come to term as a supporting argument that the fetus is entitled to be classified as a human being.
The fetus qualifies as human. As such, it is covered by the injunction in Christian tradition to “Love thy neighbor.” Noonan’s reasoning clearly reflects a communitarian view. A member of the human community has special entitlements, including the privilege to be treated as a neighbor.