The soul and modern medicine

[tacf]

Curious what others here thought about ensoulment and modern medical observations. Given trends in modern medicine, a more developed Catholic framework is needed (unless someone knows a source I haven't heard of). Below I tried to work out what I thought were complicated cases.

Background information:

God infuses the soul when a properly disposed body is generated, i.e., a body reaches the term of natural generation, i.e., is a body with a sensitive soul, which we will call a "potentially human body". It is in this sense we understand "the soul is created together with the body." (De Eccl. Dogmat. xiv, xviii. Cf St Thomas, Summa Theologica, Book 1, Question 118.) A potentially human body has as its material causes the oocyte and sperm and as its proximate efficient cause the seminal power of the sperm.

For clarification, sperm is not living, but functions like a instrument. It's local motion is like that of a thrown stone, from an intrinsic principle imparted by the agent (father), but it's motion is generation, not change of place.
St Thomas, On the Soul, Question 11:

"The power existing in the semen which is derived from the father is a permanent intrinsic power, not one coming from an extrinsic principle, just as the power of the mover which exists in the thing thrown is intrinsic. Hence the power which is in the semen operates no matter how far away the father may be. For the active power which is in the semen cannot be caused by the mother (although some indeed maintain this), because the woman is not an active principle but a passive one. Nevertheless there is some similarity here, because, just as the thrower's power, which is finite, moves an object to a definite place some distance away by local motion, so does the power of one generating move a thing to a determinate form by the movement of generation."

Sperm does have life potentially/virtually, which is why the seminal power can confer vegetative and sensitive souls to properly disposed matter.
St Thomas, Summa Contra Gentiles, Book 2, Chapter 89:

"about the life of the semen at the beginning of its severance, it is clear from what has been said that it is not living except potentially. Therefore, it has a soul then not actually, but virtually. In the process of generation, it has a vegetative and a sensitive soul by the virtue of the semen, which do not remain but pass away when the rational soul takes their place."

The fact that sperm are not living is in accord with modern observation; they do not have all the actual powers of even a nutritive soul: 
Jones S, et al. Intracellular translocation and differential accumulation of cell-penetrating peptides in bovine spermatozoa: evaluation of efficient delivery vectors that do not compromise human sperm motility. Hum Reprod. 2013 Jul;28(7):1874-89.

"The fully differentiated male gamete is usually a highly polarized and motile cell type specialized for the single function of oocyte fertilization. Associated with a much reduced internal volume, the mature sperm cell lacks a variety of organelles, including endoplasmic reticulum, Golgi apparatus and cytosolic ribosomes, which are not required for those processes leading up to and including fertilization. Moreover, as recently reviewed, at the time that mammalian sperm are released into seminiferous tubules the processes of genomic transcription and translation have largely been silenced; though it is likely that sperm deliver a variety of RNA species into the fertilized oocyte that may modulate early events in embryogenesis."

Perhaps more evidently, we see they cannot perform acts of generation - and this is not a power incapacitated by chance (per accidens), but a per se absence - so a sperm is not living.

For each act of nature, there is a corresponding natural power that is the efficient cause. For the act of generation, the production of the potentially human body has as its proximate efficient cause the seminal power.
St Thomas, Summa Contra Gentiles, Book 2, Chapter 89:

"Accordingly, the human body is fashioned at the same time both by the power of God as the principal and first agent, and by the power of the semen as secondary agent, but God's action produces the human soul, which the seminal power cannot produce, but to which it disposes."

We know the generation has reached the term of its act when the subject X has at least virtually present all the powers of the sensitive soul. To be virtually present means to be present in the intrinsic causes of a thing, although not actually present from some material indisposition or external obstacle.
Dictionary of Scholastic Philosophy, Page 131:

"by way of active potency or efficacy; after the manner of a cause. Not actually, but equivalently and implicitly".

See Summa Theologica, Book 1, Question 76, Articles 3 and 4. Example is a blind man virtually possessing sight, able to have children with sight. It is observed that the zygote has all the material powers of the human soul (nutritive and sensitive) at least virtually present. This is because the material powers of the soul have as their proximate efficient cause the DNA, RNA, and any epigenetic regulators of the cell. It is also observed that some powers are actually present, such as nutrition. Given time and continued proper material cause, the material powers of the human soul will be manifested. This is in accord with observations, where we note even a single cell can have a sensitive soul. For example, certain single cell organisms even have sight.^1
1Schuergers N. Cyanobacteria use micro-optics to sense light direction. Elife. 2016 Feb 9;5:e12620.

Given that the zygote has the powers of the sensitive soul at least virtually present, it is the proper term of the seminal power in the act of generation, i.e., it is the final cause. As established above, this is the properly disposed matter for ensoulment, so at the moment of its generation, God creates a soul together with it.
St Thomas, On the Soul, Question 11:

"the generation of an animal is not one simple generation alone, but that many generations and corruptions follow one another. For it is said that first the animal has the form of semen, then the form of blood, and so on successively until generation is completed. And therefore since corruption and generation do not take place without the loss of one form and the acquisition of another, the imperfect form which first exists within the embryo must be discarded and a more perfect one assumed. This continues until the thing conceived has acquired its perfect form. Consequently it is said that the vegetal soul first exists in the semen, but that it is lost in the process of generation, and that another soul succeeds it which is not only vegetal, but also sentient. Then another soul is added to this which is at once vegetal, sentient, and rational."

This explanation preserves the notion that human life begins at conception, although it is debatable if that is the moment the sperm contacts the oocyte, the moment their membranes join, the moment their DNAs join, or the moment the epigenetic regulators are properly placed, or some other point.

Case 1 - post-zygotic / identical twinning:

For the case of post-zygotic twinning, we say the seminal power is not lost at the exact instant a zygote is formed. As long as the zygote has the capacity to have another zygote formed from it, we say that the seminal power must still be present. It is then simply a case of observation to determine when this normally is no longer present. Since post-zygotic twinning is not observed past the blastomere stage, we say this is the time when the seminal power is no longer present. And we hypothesize the seminal power to have as its formal cause in the epigenetic regulators of the sperm DNA, or in the RNA which also accompanies the sperm, or some combination. Some arrangement of the material in the sperm gives it the power to induce a being with a sensitive soul given proper matter; this material and its arrangement persists even after the formation of the zygote. If one identified what material and its arrangement were the necessary and sufficient cause for making a cell totipotent, then one would have identified the seminal power. Just as the seminal power persists in the sensitive souled potentially human body, so it can persist in the rationally souled human.

Case 2 - Human chimeras:

In this case there is twins in which one dies in utero and the remaining living one absorbs some of his cells. How many souls are present? We say that the cells after death have vegetive lives. Since normal digestion is bypassed, this is a per accidens result when the very specific material cause of once human vegetive life is introduced into the body accidentally. It is the same as a heterologous bone marrow transplant except that is done through art. However, because the body's immune system must learn "self" from "non-self" during growth, if this occurs before the immune system has developed these cells will not be recognized as foreign. So the fact that chimeras do not need immunosuppression is because of the material indisposition of the immune system at the time of the accident. To reiterate, these cells are not incorporated into the soul/body composite, but that the human lives the majority of his life with commensal vegetive organisms (for the absorbed cells are dispersed in the absorbers body, analogous to bacteria in the gut). Heterologous bone marrow transplants requiring continued immune suppression is then a similar situation but in this case the body's immune system recognizes the matter as foreign.

Case 3 - Fetal cells in mothers, forming chimeras:

In some cases, fetal cells may stay in a woman's body for years. In a 2012 study, researchers analyzed the brains of 59 women ages 32 to 101, after they had died. They found 63 percent of these women had traces of male DNA from fetal cells in their brains. The oldest woman to have fetal cells in her brain was 94 years old, suggesting that these cells can sometimes stay in the body for a lifetime.^2
2Scientific American. "3 Human Chimeras that already exist." Rachel Rettner, August 8, 2016. https://www.scientificamerican.com/article/3-human-chimeras-that-already-exist/
The answer to this is the same as above, except now the per accidens failure of the immune system is occurring in an adult female.

Case 4 - Conjoined twins:

It is clear that each has some control over definite parts of the conjoined body. So we say there are in fact two bodies present, contacting in a manner which per accidens would result in death if separation occurred. Each cell would be traceable to one of the persons, and the extracellular components would be traceable to a particular cell. And the blood would be constituted of extracellular components similarly traceable or the matter of nutrition which has not yet reached the term of the act of nutrition, i.e., not yet fully incorporated into the composite, and so would not truly be a part of either - or would be classified as a part of whichever person's body was controlling that material.

Case 5 - Pluripotent stem cells (hPSCs):

What if babies in the future can be derived from pluripotent stem cells using in vitro fertilization? At what point are they human? If hPSCs can be induced to a state were they are functionally equivalent to a zygote, they are human. The father and mother in that case would be the persons who donated the stem cells.
Current state of research: Yamashiro C, Sasaki K, Yabuta Y, Kojima Y, Nakamura T, Okamoto I, Yokobayashi S, Murase Y, Ishikura Y, Shirane K, Sasaki H, Yamamoto T, Saitou M. Generation of human oogonia from induced pluripotent stem cells in vitro. Science. 2018 Oct 19;362(6412):356-360. doi: 10.1126/science.aat1674. Epub 2018 Sep 20. PMID: 30237246.

"Human in vitro gametogenesis may transform reproductive medicine. Human pluripotent stem cells (hPSCs) have been induced into primordial germ cell-like cells (hPGCLCs); however, further differentiation to a mature germ cell has not been achieved. Here, we show that hPGCLCs differentiate progressively into oogonia-like cells during a long-term in vitro culture (approximately 4 months) in xenogeneic reconstituted ovaries with mouse embryonic ovarian somatic cells. The hPGCLC-derived oogonia display hallmarks of epigenetic reprogramming-genome-wide DNA demethylation, imprint erasure, and extinguishment of aberrant DNA methylation in hPSCs-and acquire an immediate precursory state for meiotic recombination. Furthermore, the inactive X chromosome shows a progressive demethylation and reactivation, albeit partially. These findings establish the germline competence of hPSCs and provide a critical step toward human in vitro gametogenesis."

Case 6 - Human-pig and Human-cow chimeras:

In this case, a human cell or collection of cells is injected into the embryo of a pig or cow. This is intended for transplants - for example, pancreatic cells are injected into a pig, are dispersed into the pig pancreas, grow with that pancreas, and once the pig is full grown its pancreas can then be transplanted to a human and perform human pancreatic functions. Is the animal then a human? I say that if the injected human stem cell could have been implanted and given rise to a human baby, we say a human was injected into a pig, struggled to survive, and died, leaving once human vegetive cells in its place. These may then form commensal, mutual, or parasitic relationships with the pig.
Current state of research: Wu et al., 2017, Cell 168, 473–486. January 26, 2017 ª 2017 Elsevier Inc. http://dx.doi.org/10.1016/j.cell.2016.12.036

"Interspecies blastocyst complementation enables organ-specific enrichment of xenogenic pluripotent stem cell (PSC) derivatives. Here, we establish a versatile blastocyst complementation platform based on CRISPR-Cas9-mediated zygote genome editing and show enrichment of rat PSC-derivatives in several tissues of gene-edited organogenesis-disabled mice. Besides gaining insights into species evolution, embryogenesis, and human disease, interspecies blastocyst complementation might allow human organ generation in animals whose organ size, anatomy, and physiology are closer to humans. To date, however, whether human PSCs (hPSCs) can contribute to chimera formation in non-rodent species remains unknown. We systematically evaluate the chimeric competency of several types of hPSCs using a more diversified clade of mammals, the ungulates. We find that naïve hPSCs robustly engraft in both pig and cattle pre-implantation blastocysts but show limited contribution to post-implantation pig embryos. Instead, an intermediate hPSC type exhibits higher degree of chimerism and is able to generate differentiated progenies in post-implantation pig embryos."

Case 7 - Mitochondria donors

In an instance of in vitro fertilization, a man and woman each donated their gametes, but the mitochondria were removed from the oocyte and a second woman contributed her mitochondria. Who is the father and mother(s) in this situation?
First we must clarify what it means to be a father and mother:
St Thomas, Summa Contra Gentiles, Book 4, Chapter 11.

"Now we must observe that the carnal generation of animals is effected by an active and a passive function. The father takes an active part, while the mother's part is passive, so that the begetting of offspring belongs to the father as regards certain conditions, and to the mother as regards others. It belongs to the father to give his offspring its nature and species, while conception and gestation belong to the mother, whose part is passive and receptive. ... ...conception and birth in corporeal beings include movement and consequently some kind of succession—since the term of conception is the existence in the conceiver of that which has been conceived, and the term of birth is the separate existence of the offspring apart from the parent"

This is an instance of an external agent introducing a material indisposition into the body. The conceptus' or oocyte's mitochondria must be removed first, which is a mutilation. Because we do not see our cells taking up mitochondria for the most part, this is a per accidens event (instigated by human art).³ Per se acts are prior to per accidens, so the per se acts of the mitochondria cannot fulfill the role of per se acts for the cell, as its relation to the cell was a per accidens occurrence.⁴ The fact that the mitochondria is not rejected by the cell is from a defect of the cell. The fact that the implanted mitochondria performs functions useful to the cell is a fortunate event (and all fortunate events are chance events, i.e., per accidens). Thus we do not have to conclude that the donated mitochondria is assimilated into the form of the person. So there is only one father and mother.
³ Commentary on the Physics, Book 2, Lecture 9:

fortune is rightly said to be without reason. For we can reason only about those things that happen always or in most instances. But fortune lies outside of both of these. And so, since such causes, which occur in exceptional cases, are per accidens and infinite and without reason, it follows that causes by fortune are infinite and without reason. For every per se cause produces its effect either always or in most cases.

⁴ Summa Contra Gentiles, Book 2, Chapter 39:

An essential cause is before an accidental cause. Hence if later things are from a determinate essential cause, it is unfitting to say that the first things are from an indeterminate accidental cause. Now the distinction of things naturally precedes their movements and operations, since determinate movements and operations belong to things determinate and distinct. But movements and operations of things are from essential and determinate causes, since we find that they proceed from their causes in the same way either always or for the most part. Therefore, the distinction of things is also from an essential determinate cause, and not from chance, which is an indeterminate accidental cause.

Case 8 - Hydadiditform moles

Are molar pregnancies human? I say no. In the case of a complete mole, two sperm unite with an empty egg, so no zygote is formed. Thus the cell is not human, but has vegetive life. In the case of a partial mole, the most common scenario is a duplication in the sperm genome before union with the oocyte genome, resulting in a triploid cell. Thus, no conception has occurred as there was never proper material cause for infusion of the soul.
Slim R, Mehio A (January 2007). "The genetics of hydatidiform moles: new lights on an ancient disease". Clinical Genetics. 71 (1): 25–34.

"A small percentage of hydatidiform moles have biparental diploid genomes, as in normal living persons; they have two sets of chromosomes, one inherited from each biological parent. Some of these moles occur in women who carry mutations in the gene NLRP7, predisposing them towards molar pregnancy. These rare variants of hydatidiform mole may be complete or partial."

Even in these cases, the proper material cause was lacking for infusion of a soul (in this case from the partial absence of a genome of the mother), and so no infusion of soul or conception occurred.

[Geremia]

Was St. Thomas not a preformationist?

[tacf]

Yes, man has only one soul, a rational one. He is a substance, not a collection of accidental forms. Substantial change is instantaneous. I don't see how my explanations disagree with that.

And I'm following St. Thomas' explanation:
St. Thomas, On the Soul, Question 11

Therefore our explanation must be different, namely, that the generation of an animal is not one simple generation alone, but that many generations and corruptions follow one another. For it is said that first the animal has the form of semen, then the form of blood, and so on successively until generation is completed. And therefore since corruption and generation do not take place without the loss of one form and the acquisition of another, the imperfect form which first exists within the embryo must be discarded and a more perfect one assumed. This continues until the thing conceived has acquired its perfect form. Consequently it is said that the vegetal soul first exists in the semen, but that it is lost in the process of generation, and that another soul succeeds it which is not only vegetal, but also sentient. Then another soul is added to this which is at once vegetal, sentient, and rational.

And this doesn't mean I'm saying it's not a substantial change, or that the substantial change is not instantaneous, only that each composite undergoes alteration before being the proper matter for a further substantial change, which St Thomas clearly allows:
De Potentia, Disputed Questions, Question 3, Article 11:

"... a substantial form is brought into act not continuously or by degrees but instantaneously (else movement would needs be in the genus of substance just as it is in that of quality)... Thus the form of fire is not produced in the air so as gradually to advance from imperfection to perfection, since no substantial form is subject to increase and decrease, but it is the matter alone that is changed by the previous alteration so as to be more or less disposed to receive the form; and the form does not begin to be in the matter until the last instant of this alteration."

St Thomas would not call the thing with only a vegetative or sensitive soul a human, just like he wouldn't call the former eye of a corpse an eye, except only equivocally. And neither do I - so there is no "human fetus with a vegetative soul" or "human fetus with a sensitive soul". Just like there's no oocyte human fetus.

St. Thomas, Summa Contra Gentiles, Book 2, Chapter 72

That it is the substantial form both of the whole and of the parts is clear from the fact that both the whole and the parts take their species from it. Hence, when it departs, neither whole nor parts retain the same species: for the eye or flesh of a dead person are only so called equivocally. Accordingly, if the soul is the act of each part, and an act is in the thing of which it is the act, it follows that it is by its essence in each part of the body.

From what I could tell, "preformationism" says there was an inanimate body and then a rational souled body. Please correct me if I'm wrong. If true, then I don't see how to say St. Thomas was a preformationist given the quote from On The Soul above.

[Geremia]

From what I could tell, "preformationism" says there was an inanimate body and then a rational souled body.

That's epigeneticism.

[tacf]

Well then, I guess great. I agree with preformationism.