Aquinas on the Beginning and End of Human Life

Fabrizio Amerini, Mark Henninger

• Publisher: Harvard University Press
• Year: 2013
• ISBN:
  9780674073463
• Topic: Philosophy
• Subtopic: Medieval & Renaissance Philosophy

In contemporary discussions of abortion, both sides argue well-worn positions, particularly concerning the question, When does human life begin? Though often invoked by the Catholic Church for support, Thomas Aquinas in fact held that human life begins after conception, not at the moment of union. But his overall thinking on questions of how humans come into being, and cease to be, is more subtle than either side in this polarized debate imagines. Fabrizio Amerini—an internationally-renowned scholar of medieval philosophy—does justice to Aquinas' views on these controversial issues.Some pro-life proponents hold that Aquinas' position is simply due to faulty biological knowledge, and if he knew what we know today about embryology, he would agree that human life begins at conception. Others argue that nothing Aquinas could learn from modern biology would have changed his mind. Amerini follows the twists and turns of Aquinas' thinking to reach a nuanced and detailed solution in the final chapters that will unsettle familiar assumptions and arguments.Systematically examining all the pertinent texts and placing each in historical context, Amerini provides an accurate reconstruction of Aquinas' account of the beginning and end of human life and assesses its bioethical implications for today. This major contribution is available to an English-speaking audience through translation by Mark Henninger, himself a noted scholar of medieval philosophy.

CHAPTER FIVE

The Identity of the Embryo

Before discussing some possible bioethical implications of this account of the process of human generation, we must clarify Thomas’s position on what is perhaps the most important philosophical issue involved in these discussions: the identity or continuity of the subject of the embryogenetic process. As we have seen, Thomas’s explanation of embryogenesis is reached partly by rejecting the idea that generation is a continuous process. Such a stance becomes necessary once one affirms theses (F1)–(F3), which concern the nature of substantial form, and one affirms the difference between substantial generation on the one hand and quantitative and qualitative alteration on the other (G1). In particular, Thomas rejects the idea that there exists a formal continuant within the generative process, that is, that there is a form that remains numerically the same throughout the whole process.¹ Nevertheless, he does admit that the formative power or its subject, the “spirit” (spiritus), which the semen derives from the soul of the father, remains throughout the entire process.² If the process of generation is discontinuous, with an alternation of generations and corruptions, how can one defend the identity or continuity of the subject of this process? The identity of the subject of the process, however, must to some degree be admitted, for otherwise one could not even assert that the embryo becomes a human being, nor could one speak of human embryos.

1. The Identity and Continuity of the Embryo

In general, the question of the continuity of the embryo in the generative process is to be kept distinct from the question of its identity or unity. In the first case, we are called to demonstrate that the embryo does not completely cease existing at a certain moment of the process for the good of something else. Abstractly, this continuity could be proven in two ways: either (1) by demonstrating that there is something of the embryo (an organic part of it or a portion of its matter) that remains exactly as it is, unmodified from the beginning to the end of the process, or (2) by demonstrating that the process of the embryo’s transformation does not include temporary halts or have interruptions. Thomas’s conclusion that the process of generation is not continuous, as opposed to the process of alteration, seems to leave little room, however, for defending the embryo’s continuity throughout the entire process. A follower of Thomas could admit his conclusion that the process is discontinuous but limit it to the formal plane. The embryo in the very first phases of development can be considered as formally different from the embryo endowed with vital organs. But on the material plane, she/he could be less inclined to concede that the process is totally discontinuous, not only because it seems necessary that there be one and the same matter that gradually becomes organized and grows in quantity but also because there is no observable evidence of any substantial interruption in the process.

The question of the identity or unity of the embryo brings up a different problem: whether we can demonstrate, beyond the transformations that the embryo undergoes and the continuity of these transformations, that the process involves one and the same entity. On closer look, this question includes two different problems. One must first establish when the embryo can be considered an entity distinct from the mother, and second, one must ascertain whether in the generative process one can speak of a transtemporal numerical identity of the embryo so that one can affirm that the baby just born is the same entity as that embryo from which it came when it was first conceived.

Obviously, the questions of identity and continuity are not completely unconnected. If one succeeds in proving that the embryo maintains its identity throughout the process of generation, one has also proven a type of continuity of the process itself and of the subject of that process. Therefore, in what follows, even with this difference in mind, we will talk at times of the identity or continuity of the subject in a way that is substantially equivalent. More particularly, in this chapter we will be concentrating above all on the question of the identity of the embryo.

The difficulty in ascertaining the identity of the embryo is dependent on another difficulty, i.e., that of establishing what exactly happens, according to Thomas, before the coming of the rational soul. It is certain that this difficulty is not encountered with formed embryos, that is, those following the fortieth day. Thomas upholds that these embryos are ensouled and so are entities completely distinct from the mother, although they continue to be materially connected to her in the maternal womb; after the fortieth day, the process of generation is formally ended and the process of growth properly speaking begins. Often Thomas fixes this watershed while discussing whether original sin is transmitted to the one to be born through its conception.³ At other times it is fixed when he discusses the question of whether by baptizing a pregnant mother the effects of baptism are also passed on to the child in her womb.⁴

But things are different before the coming of the substantial form, for during that time the embryo does not yet have a stable species, as it is incessantly changing form and continuously transforming its matter. The embryogenetic process, which brings the female material inseminated by the male semen to become an embryo at first lacking in form and then endowed with form, seems to encounter problems with both types of continuity, i.e., formal and material. When, then, does the embryo become an entity formally or materially independent? How can one account for the identity that the embryo is supposed to maintain throughout the generative process, from conception to birth?

The impression one has reading Thomas’s texts is that there is no one response that he gives to these questions. As just mentioned, after the infusion of the rational soul the embryo is certainly an autonomous entity in all respects.⁵ But before that point, Thomas’s response is conditioned by the ephemeral status of the embryo, by its unfinished state and potentiality. The principle that Thomas often uses—that if an embryo carries out vital operations, it is necessary that it have an internal principle of ensoulment—does not decide the issue in favor of immediate human ensoulment rather than delayed. As we have said, one could explain the vital principle as a “power of the soul” (virtus animae) rather than as a real and proper soul and so concede to the embryo (which is not rationally ensouled) at any rate an improper and imperfect ensoulment. The immanence of a principle of ensoulment, therefore, does not furnish us with a criterion of identity. What is more, in what follows, we shall see that the embryo escapes all the criteria for transtemporal identity that Thomas elaborates in his works.

The vacillation found in Thomas’s texts does not help us in answering our two questions. We have seen that at times Thomas concedes that the vegetative soul exists potentially in the semen, while at other times that it exists potentially in the menstrual blood. If we assume that the vegetative and sensitive souls, which characterize the first moments of the embryo’s life, are potentially present in the male semen, then the full independence of the embryo could take place only when the formative power of the semen ceases its activity, and so only at the moment of the infusion of the rational soul. But on the other hand, we could assume, following instead Thomas in the Summa theologiae, that the vegetative and sensitive souls that the embryo possesses are potentialities of the embryonic matter.⁶ In this case, the embryo could be considered as something formally independent from the moment of conception, for right from the first moment the embryo has a soul or a power of the soul, i.e., vegetative, that guides the process of nutrition, growth, and qualitative differentiation of the embryonic matter.⁷ Even though Thomas’s arguments for rejecting the idea that the ensoulment of the embryo comes from the mother’s soul are not completely conclusive as we have seen, it remains true for Thomas that an embryo must have an internal principle of ensoulment. For otherwise we cannot explain why the embryo carries out operations that, if it were truly part of the mother, are not also carried out by her entirely. And so, if the actualization of the potentiality to nourish itself, which the matter of the mother possesses, thanks to the action of the formative power of the male semen, is nothing other than the appearance of the vegetative soul, we have to conclude that the embryo takes on its own identity as an entity formally independent from the mother already with the coming of the vegetative soul.

On this problem, I mention in passing that the contrast “immediate ensoulment versus delayed ensoulment” does not entirely capture the core of Thomas’s position. On the one hand, there is no doubt that Thomas defends some type of immediate ensoulment of the embryo, rejecting both (1) that the soul of the female is the factor responsible for the vital operations of the embryo, and (2) that this factor is exclusively the formative power of the male semen. In both cases, the reason is that the two principles are external to the embryo. As a consequence, Thomas admits that the embryo possesses right from conception at least vegetative ensoulment. But on the other hand, he rejects (3) that such ensoulment is from the beginning rational (i.e., human) and (4) that this ensoulment is of itself complete and perfect. More particularly, we have seen that this second denial is reached by his rejecting certain theses. The first thesis is that there are really distinct souls copresent in the human being or in the embryo, for then the souls coming after the first would end up being accidental forms of the body, granted that the soul is the substantial form of the body. The second thesis is that there is in the human being or in the embryo a soul that over time has assumed different degrees and perfections, since then (a) the substantial form would change in intensity, contrary to (F3) that “substantial form does not admit of degrees”; (b) generation would turn out to be indistinguishable from alteration, contrary to (G1) that “natural generation, as opposed to the change of qualities or of quantity (alteration) and that of place (locomotion), is a discontinuous process”; (c) the generation of a human being would not be a true and genuine generation; and (d) the immortality of the rational soul would not be reconciled with the mortality of the vegetative and sensitive souls.⁸ What remains after these denials is the idea that there is in the process of generation a continuous substitution of forms. Assuming from now on in our discussion that the Summa theologiae expresses Thomas’s final position, namely, that the embryo can be considered an entity formally independent from the mother right from conception, since right from the very start the embryo exhibits vital operations that cannot be superimposed on or reduced to those of the mother, the problem of the transtemporal identity concerns the embryo right from conception. How then is it possible to safeguard the identity of the embryo from conception up to the formation of the basic vital organs?

The answer that Thomas’s interpreters commonly give to this is that the process of human generation is materially continuous and formally discontinuous. This is intuitively clear and makes sense of many of Thomas’s claims. But how are we to understand the continuity and identity of matter? Which matter is responsible for the continuity and identity of the subject and how is the identity of the matter to be established if every process of identifying a thing, whether on the metaphysical or cognitive plane, requires a form? Since we are dealing after all with a process of generation, someone could point out how, in an obvious sense, there can be nothing, either on the formal or material plane, that from the start of the process to its end remains exactly as it is. As we have mentioned, Thomas himself holds that one should not be surprised that the process of generation is not continuous. If it were, it would be indistinguishable from a process of nourishment or growth, since if the process were continuous, there would be a subject that is already generated in act from the first moment. But on the other hand, it is undeniable that the process of generation, even if it admits of differentiated subprocesses, is on the whole a process that takes place without interruptions or gaps, and therefore a certain continuity of the process must be guaranteed even if in a rather tenuous way. Thomas’s problem is precisely this: how to reconcile the formal discontinuity of the subject with its presumed material continuity. If the criterion for identifying a thing is given by its form, when the form is changed, also the identity of the thing ceases. Consequently, if the criterion for ascertaining the continuity of a thing is given by matter, it seems impossible to set aside the form, since the matter itself is identified with recourse to form. How, then, can we talk of continuity of matter without talking of identity of form?

In what follows, we shall first show how Thomas explains the identity of the subject of a process of generation, and then we shall show how one can speak of identity and continuity with regard to matter.

2. The Identity of the Subject of Generation

When one begins to give an answer to these questions, the first thing to do is to consider what criteria Thomas himself developed for determining the identity of a thing. As it turns out, this task is especially arduous. One reason is that in his works Thomas formulates criteria for establishing the identity of a thing that are quite diverse. In addition, such criteria are not always formulated uniformly and, moreover, one realizes that strictly speaking they are applicable only to entities that already exist in act. For example, Thomas often discusses the question of whether someone’s body is numerically the same after the human soul is separated from it, and if such a body remains numerically the same at the moment of the final resurrection at the end of time. Evidently, these questions are meaningful since they are asking about an identity between two things that, though at different times, nevertheless exist in act. Similarly, Thomas asks if Socrates and this white thing are the same entity, and again the question makes sense since “Socrates” and “this white thing” refer to things that, at the same time, exist in act. But in the case of an embryo, any criterion of identity seems to fail. For example, when we ask if a given embryo and a given human being are numerically the same thing, the question does not seem germane, since we have seen that Thomas conceives of the embryo as something that does not exist in act, not having a perfect and complete form of its own. Hence, it does not seem that one can say that the embryo is either numerically the same nor numerically different from the human being.

Certainly there is an obvious sense in which an embryo and a human being can be called the same entity, given that a human comes from an embryo. But this sense is of little relevance, for a table can also be said to come from the wood of a tree, but the table and tree cannot be called for this reason the same entity. The case of the embryo is more complex. In this case, it is not enough to say that the human comes from the embryo; we must add that the embryo becomes a human being, while we cannot say of the tree that it becomes a table. In other words, a simple “principle of traceability,” by which it would be possible to determine the identity of a changing subject in whatever phase of the process of change, once the rule of change is known, does not seem sufficient to determine the identity of the subject within a process of generation. Besides admit...