Aquinas on the Beginning and End of Human Life, by Fabrizio Amerini

December 2, 2014

It is a well-known and somewhat em­barrassing fact that Thomas Aquinas does not agree with the current Catholic view that from the moment of conception a human being exists, with all the moral weight that such a designation implies. For Aquinas, there is no human being until later in gestation, with the coming of the rational soul. This is called the delayed hominization view.

Those who are interested in reconciling the Angelic Doctor’s position with current Catholic claims argue either that he was mislead by the rudimentary state of embryology at the time or that a careful reading of various texts can offer a philosophic rapprochement. Fabrizio Amerini, professor of classics at the University of Parma, has written an extraordinarily important analysis of Aquinas. His account creates precision about Aquinas on beginning-of-life issues that is often lacking in philosophical analysis and certainly in abortion polemics. Al­though the title promises discussion of the end of life, Aquinas actually said very little on the subject, and Amerini follows suit.

Amerini is steadfast in rejecting attempts to find a philosophical resolution to the conflict. The presumed reconciliations cannot be derived from Aquinas’s texts. Can one, then, discount Aquinas’s views because of bad embryology? Would he have opted for immediate hominization had he known about DNA and the genetic code? Amerini argues persuasively that the crux of Aquinas’s view is fundamentally metaphysical and that defects in the science of embryology were not determinative. Aquinas’s metaphysics is Aristotelian and thus can still have a profound impact on the moral assessment of abortion.

The word metaphysics suggests some kind of airy abstraction. The aim of metaphysics can, however, be re­garded as answering the question: What is the ultimate subject of science? The problem with understanding Aquinas is the radical change since his day in how we answer that question. For Aquinas and his philosophical model, Aristotle, the ultimate subject of science is natures (plural) and how they are defined. Modern science, on the other hand, aims at a unified science of nature (singular). Aquinas, following Aristotle, rejects any unified science in favor of differing sorts of inquiry according to the nature of different things. He would agree with a present-day philosopher of science, Nancy Cartwright, that we live in a “dappled world.”

Why opt for such a world? Because a unified science of nature tends to distort what Aristotle regarded as a most obvious physical reality: change. In On Generation and Corruption he wrote: “For those who say that the universe is one something (i.e., those who generate all things out of one thing) are bound to assert that coming-to-be is alteration.” There are two ways to have a unified science: reduce everyday phenomena to ultimate parts (ancient and modern atomism), or insist that everyday phenomena can be understood only as functions of an ultimate whole (Plato’s “the Good”; Spinoza’s “God or Nature”). What we perceive as change does not touch ultimate reality; atoms and God remain unchanging. Change is merely alteration, rearrangement of unchanging atoms or variations in modes of eternal God or nature.

Aquinas’s allegiance to Aristotle’s dappled world of nonreducible substances could well seem contrary to faith—and did so to many at the time. You can understand why Christian thinkers have been so attracted to some version of the Platonic idea.

What does all this metaphysics have to do with abortion? In a world of many different natures there are also different sorts of change (Socrates grows older; I paint the chair red). What sort of change occurs in biological generation? For Aristotle and Aquinas, generation is a unique change not to be confused with some other sort of change. The typical case of change is when the substance remains the same while change happens to it. Socrates is the same but happens to grow older; the chair is the same but is now painted red. Aquinas rejects the view that in generation there is a fixed substance that remains the same from embryo to birth: generation cannot start with a completed substance; it proceeds toward a completed substance.

The human being, then, is not a variation on the embryo-substance in the way in which Socrates is the same even as he grows older. In the case of humans it is only when the rational soul comes into being that one is a human being. Soul is not an essentially theological term. Vegetables and animals have souls, their actual living function. As Aristotle said, “If the eye were the whole body, then seeing would be its soul”—that is, it would be what it does. For humans, the human soul is the special human body with its developed organs of vegetable digestion, animal motion, and capacity for reason. The soul of human beings exists when all the organs become capable of doing their thing. Until this level of development is reached, there is no proper human person with full moral weight.

Aquinas’s problem is establishing an identity between the embryonic state and the fully realized state toward which the process tends. The direct solution would be to say that the soul is somehow fully present from the beginning. That position was known to him in such writers as Gregory of Nyssa and his near contemporary, Robert Grosseteste. The problem with immediate hominization is that it reduces generation to mere growth: the embryo is a substance that remains the same, that will be altered, not developed. For Aquinas the continuity of generation is sufficient to establish an identity without having to posit that the full human soul, or substance, is present from implantation.

To illustrate what concerned Aristotle and Aquinas, consider how things went wildly wrong in embryology and metaphysics for the 18th-century spermatists. These thinkers held that the male sperm was a homunculus, a small man. Given that view of the sperm, the function of the female egg was to feed the little being until it was big enough to be born. The spermatists thus asserted that from the beginning a human being existed. (But what was the fate of all the spermatic homunculi that were ejected and did not get implanted?) The problem with such a view—and with the current church claim about immediate personhood—is that it seems impossible to distinguish generation from growth. Aristotle, Aquinas, and lots of common sense distinguish be­tween generation, the process in which an embryo becomes a baby, and growth, when the baby becomes bigger, stronger, and older.

I suspect that the current Catholic position is closer to a Platonic metaphysics than to Aquinas’s Aristotelian realism. There are no substances in Plato’s metaphysics. Things are distinguished by their participation in ideas—we would say that they happen to have such and such properties. From an Aristotelian point of view, all such attribution is accidental. There is an X that has certain properties—for example, this particular DNA structure. Is that enough to say that it is a human being, or would we want additional properties? Thus the difficult issue of deciding when X has enough properties to fully earn the label human. X at various stages could be said to be more or less human. Aristotelian substance—that is, human being—cannot be more or less human. Socrates is not more human (substance) than Alcibi­ades; the born child is not simply more a human being than the embryo.

Whatever one may think of Aquinas’s metaphysics and the special character of generation, his opting for delayed homi­nization gave him justification for church practices and beliefs. Although it is claimed that the embryo is in some sense a full human being, we do not hold that miscarried fetuses share in the general resurrection or, as Aquinas notes, have a personal guardian angel. Accep­tance of delayed hominization would also conform to common law and to the one passage in the Bible about abortion, Exodus 21:22–25, which treats it as less than homicide.

If we were to accept Aquinas’s view of the process of generation, how would it change the abortion debate? Abortion would still be viewed as a morally grave act because of continuity toward a body capable of having a rational soul. On the other hand, if in the early stages we are dealing with something that is not yet a perfected human being, I think Amerini is correct; we would “look in a less dramatic way upon the fate of the embryo . . . and approach bioethically certain critical cases with greater adaptability to difficult circumstances.” I agree and would fault much of the official antiabortion rhetoric for overdramatization, which creates a level of moral rhetoric that resists reason and discussion.

Amerini’s book, with its long Latin quotations from Aquinas in footnotes to substantiate his analysis, is not for the casual reader. If the proper characterization of generation is ultimately metaphysical, a decision between nature and natures, someone unused to the complexity and profound consequences of metaphysical differences will find the book a challenge. It is, however, worth the effort.