In February 2012, the Journal of Medical Ethics (JME) published a scholarly article  defending infanticide (“after-birth abortion”). It stirred considerable controversy. The authors, Alberto Giubilini and Francesca Minerva (GM), argued as follows: a fetus is not an actual person but a potential person; killing a potential person does not harm an actual person, it merely prevents an actual person from coming into existence; no one is harmed by being prevented from becoming an actual person; therefore killing a fetus harms no one; the moral status of a newborn is not different from a fetus; therefore killing a newborn harms no one; the interests of actual people over-ride the interest of merely potential people to become actual ones; therefore “killing a newborn should be permissible in all the cases where abortion is [permissible], including cases where the newborn is not disabled.”
The GM argument for killing infants, as shocking as it sounds, is nothing more than a variation of a weak and weary but common philosophical argument going back to the 1980s denying that fetuses and newborns are “persons.”
That argument hinges on a “developmental” definition of personhood and not a species-specific or metaphysical definition. Most all pro-infanticide philosophers argue that personhood is not a property that one possesses by virtue of being a living member of the species Homo sapiens; it is a property that human individuals acquire at some point in their development. They acquire it in virtue of their ability to express consciousness. What degree of consciousness? Pro-infanticide philosophers disagree among themselves. But they commonly correlate personhood with the ability to express self-consciousness, a sense of time, or to be in possession of non-momentary interests. Fetuses and newborns express and possess none of these. Human individuals come into possession of a “right to life” only when they achieve the stage of personhood. Although we might have good reasons for not killing them before they are persons, killing them would not contravene any fundamental right not to be killed.
The JME, in May 2013, dedicates an entire issue  to the GM argument. The journal prints over a dozen replies from both philosophical defenders of infanticide (e.g., Peter Singer) and from prominent opponents, including John Finnis and Robert P. George.
Michael Tooley of the University of Colorado, Boulder, bats first for the defenders. Tooley is the most widely published  defender of infanticide in the English-speaking world. His JME article  criticizes several arguments put forward by what he calls “extreme antiabortionists” (i.e., people who think that intentionally killing born and unborn children is always wrong). I want to consider here one of those arguments.
Tooley takes aim at the traditional concept of the soul. He says plausibly that antiabortionists think abortion is wrong because they think that humans are endowed with an immaterial soul, the chief function of which is rationality. (He uses the terms soul and mind more or less interchangeably.) But if the concept of “soul” is a fiction, then the antiabortionist argument is unsound. Tooley argues that the concept is indeed a fiction and therefore it cannot plausibly be used in antiabortion arguments. Let’s look at his argument more closely.
He argues that if we subject the hypothesis of an immaterial soul to scientific scrutiny, we find it to be false. For example:
If we had an immaterial soul and we received a severe blow to the head and ceased to be conscious, we would expect that we would continue to have thoughts, since the blow obviously would not affect the soul (mind); but thought ceases until our brain recovers.
Further, traumatic brain injuries cause disabilities that correspond precisely and only to the operations of the regions of the brain that control those abilities and that suffer damage; but if the soul (mind) was immaterial, then damage to the brain would not affect the mind, and we would expect the mind to function even if the brain did not; but it does not.
Further, Alzheimer’s disease and other age-related degenerative diseases alter personality and decrease cognitive function; but if we had an immaterial soul (mind), we would expect that it would not decrease in function when the brain degenerates; but it does.
Finally, scholars who study the mind (e.g., research psychologists and evolutionary biologists) agree with Tooley and think the idea of an immaterial soul is a fiction.
Therefore, the hypothesis of an immaterial soul is unsound.
Tooley is part of a generation of philosopher who thinks that anyone who defends the existence of an immaterial soul must be defending the account of “substance dualism” proposed by René Descartes. Descartes indeed argued for two anthropological realities co-existing in human individuals, one immaterial (soul) and the other material (body). But he argued that they were radically distinct. The soul (or mind) accounted for personal identity (“I am my soul”), while the body was a kind of material add-on; both were—in the language of philosophy—“complete substances.” But if they are both complete substances, how do they interrelate? Descartes’ account gives rise to insuperable philosophical problems related to how the interaction of the two distinct principles could account for all the phenomena and acts of human cognition. And understandably, because his account is badly flawed.
As I said, Tooley believes that all defenders of the rational soul must be Cartesians. Unfortunately, his myopic materialism prevents him from engaging the older and more persuasive defense of the soul set forward by Thomas Aquinas (following Aristotle). Aquinas’ account is manifestly non-Cartesian. Aquinas does not argue that soul and body are radically distinct, but that they are indivisibly one. They are not two complete substances, but together they constitute the single substance we call the person.
The body accounts for the person’s material particularity; the soul is the principle of the continuity of identity; that in virtue of which we can say that we are the same person today that we were when we were children, even though the matter of our body has been replaced many times over. Body and soul are naturally inseparable, each incomplete without the other.
How do soul and body interact? Aquinas argues that all the living operations of the soul are carried out through organs and organ systems of the body, all, that is, but the power of abstract reasoning. Reasoning, he argues, cannot be carried out by any material organ. Although bodily operations can account for the complex acts of sensible cognition (perception, memory, imagination, dreaming, etc.), the act by which sensible objects are understood—acts of intellection or the formation of universalized concepts—cannot be accounted for within a materialist system.
In my next brief, I will summarize Aquinas’ account of why the soul (mind) must be immaterial.