Throughout Christian history theologians have wrestled with the question of when the fetus becomes a human being. The early Fathers of the Church typically distinguished an unformed fetus from one that is more fully formed, assigning greater blame to aborting a more developed fetus. For example, St. Basil the Great (d. 391) condemned abortion at all stages of development, but called aborting a formed fetus “premeditated murder.”
Influenced by the philosophy and the biology of Aristotle, Thomas Aquinas (d. 1274) taught that the developing fetus is successively animated by a vegetative soul, an animal soul and finally by a human soul, in a process called “ensoulment.” This theory had a certain plausibility given the prevailing understanding of the reproductive process that the male sperm had in potential a new human being and that this development occurred in the female uterus. It was not until the 1870s that a scientific consensus emerged that babies were produced by joining the male sperm with the female egg or ovum. This process produced a new tiny single cell entity called a “zygote,” which travels from one of the two fallopian tubes to the uterus and implants itself in the lining of the uterus in a process called “implantation.”
These discoveries of reproductive biology have moved Catholic theologians to question whether an individual human life is present immediately after fertilization. For example, Karl Rahner asserts that the claim that a fetus from the first moment of conception is a human being can no longer “be held with certainty and is open to positive doubt.” Richard McCormick describes the embryo during the first two weeks as “nascent human life” which then develops later into an “individual human life.” Charles Curran notes that during the first two weeks of pregnancy a zygote can split into two viable embryos in a process called “twinning,” which raises a “speculative doubt” about the humanity of the zygote at this stage of development, although in practice it should be treated as having a human soul. It is important to note that all of these influential theologians have consistently supported the Church teaching that abortion is intrinsically evil and morally wrong.
In a June 2021 New York Times Op/Ed, provocatively titled: “The American Bishops Are Wrong About Biden And Abortion,” the Catholic historian Garry Wills includes a critique of the bishops’ teaching that fetal life is human life from the moment of conception. In what might be considered an extension of the Thomistic ensoulment argument, Wills makes these points: Neither Augustine or Aquinas were sure when fetal life acquired a human soul; most fertilized ova are spontaneously aborted; the Church does not baptize miscarriages; and polls show most Catholics do not accept the teaching of their bishops that human life begins at conception.
In response to the Wills op-ed, The National Review published an article “Garry Wills is Wrong About the Bishops and Abortion,” which claims he “grotesquely manipulates the facts,” offers a “sloppy defense of abortion,” employs “sophomoric arguments” and distorts the views of Augustine and Aquinas.
Whatever merits of these broad criticisms, Garry Wills has made a contribution to the public debate on abortion by bringing to the attention of a wide audience the important ongoing discussion within the Catholic community on ensoulment and when human life first begins in the reproductive process.
Does the scientific knowledge of fetal development influence my view on the morality of abortion?