I answer that, It is impossible for an active power existing in matter to extend its action to the production of an immaterial effect. Now it is manifest that the intellectual principle in man transcends matter; for it has an operation in which the body takes no part whatever. It is therefore impossible for the seminal power to produce the intellectual principle.
Again, the seminal power acts by virtue of the soul of the begetter according as the soul of the begetter is the act of the body, making use of the body in its operation. Now the body has nothing whatever to do in the operation of the intellect. Therefore the power of the intellectual principle, as intellectual, cannot reach the semen. Hence the Philosopher says (De Gener. Animal. ii, 3): "It follows that the intellect alone comes from without."
Again, since the intellectual soul has an operation independent of the body, it is subsistent, as proved above (Question 75, Article 2): therefore to be and to be made are proper to it. Moreover, since it is an immaterial substance it cannot be caused through generation, but only through creation by God. Therefore to hold that the intellectual soul is caused by the begetter, is nothing else than to hold the soul to be non-subsistent and consequently to perish with the body. It is therefore heretical to say that the intellectual soul is transmitted with the semen. (Summa I.118.2.0)
The soul is the substantial form of the human being. A substantial form requires matter capable of receiving it. In the case of the human being this means that the human soul can exist only in a highly organized body. What is being presented here is a theory of serial ensoulment -- first a vegetative soul, then a sentient soul, and finally a rational soul. The animation of the new being is immediate at fertilization. But the soul that animates the body is commensurate with the kind of life lived by the body and the degree of organization of the body. So in the early stages the body of the human being is animated by a vegetative soul which organizes the operations of nutrition and growth -- vegetative activities. As the new being develops in complexity and activities, such as sensation a new soul, an animal soul, replaces the vegetative soul. As the development in complexity continues and as the development of sense organs and nervous system progresses, another threshold is crossed. When the material substratum is sufficiently disposed, the rational soul appears and the human being as human being is constituted. (Medical Ethics / Abortion)
So much for the philosphical or purely rational aspect of Creationism; as regards the theological, it should be noted that while none of the Fathers maintained Traducianism -- the parental generation of the soul -- as a certainty, some of them, notably St. Augustine, at the outbreak of Pelagianism, began to doubt the creation by god of the individual soul (there was never any doubt as to the created origin of the souls of Adam and Eve), and to incline to the opposite opinion, which seemed to facilitate the explanation of the transmission of original sin. Thus, writing to St. Jerome, St. Augustine says: "If that opinion of the creation of new souls is not opposed to this established article of faith [sc. original sin] let it be also mine; if it is, let it not be thine" (Ep. clxvi, n.25). Theodorus Abucara (Opusc. xxxv), Macarius (Hom. xxx), and St. Gregory of Nyssa (De Opif., Hom., c. xxix) favoured this view. Amongst the Scholastics there were no defenders of Traducianism. Hugh of St. Victor (De Sacr., VII, c. xii) and Alexander of Hales (Summa, I, Q. lx, mem. 2, a. 3) alone characterize Creationism as the more probable opinion; all the other Schoolmen hold it as certain and differ only in regard to the censure that should be attached to the opposite error. Thus Peter Lombard simply says: "The Catholic Church teaches that souls are created at their infusion into the body" (Sent. II, d. xviii); while St. Thomas is more emphatic: "It is heretical to say that the intellectual soul is transmitted by process of generation" (I, Q. cxviii, a. 2). For the rest, the following citation from the Angelic Doctor sums up the diverse opinions: "Regarding this question various opinions were expressed in antiquity. Some held that the soul of a child is produced by the soul of the parent just as the body is generated by the parent-body. Others maintained that all souls are created apart, moreover that they are united with their respective bodies, either by their own volition or by the command and action of God. Others again, declared that the soul in the moment of its creation is infused into the body. Though for a time these several views were upheld, and though it was doubtful which came nearest the truth (as appears from Augustine's commentary on Genesis 10, and from his books on the origin of the soul), the Church subsequently condemned the first two and approved the third" (De Potentiâ, Q. iii, a. 9). Others (e.g. Gregory of Valencia) speak of Generationism as "certainly erroneous", or (e.g. Estius) as maxime temerarius. It should, however, be noted that while there are no such explicit definitions authoritatively put forth by the Church as would warrant our calling the doctrine of Creationism de fide, nevertheless, as a recent eminent theologian observes, "there can be no doubt as to which view is favoured by ecclesiastical authority" (Pesch, Præl. Dogm., V, 3, p. 66). Leo IX (1050), in the symbol presented to the Bishop Peter for subscription, lays down: "I believe and profess that the soul is not a part of God, but is created out of nothing, and that, without baptism, it is in original sin" (Denzinger, Enchir., n. 296). That the soul sinned in its pre-existent state, and on that account was incarcerated in the body, is a fiction which has been repeatedly condemned by the Church. Divested of this fiction, the theory that the soul exists prior to its infusion into the organism, while not explicitly reprobated, is obviously opposed to the doctrine of the Church, according to which souls are multiplied correspondingly with the multiplication of human organisms (Conc. Lat. V, in Denzinger, op. cit., 621). But whether the rational soul is infused into the organism at conception, as the modern opinion holds, or some weeks subsequently, as the Scholastics suppose (St. Thomas, Q. i a. 2, ad 2), is an open question with theologians (Catholic Encyclopedia)
The argument is (again quoting Hogan):
First because the soul is the substantial form of the body, the rational soul cannot be present until there is a body present that is significantly complex and organized to receive the soul. Second, a formal cause is present only in a finished product. An actual human soul cannot be united with a virtual human body. Third, there is no human body in the zygote. Fourth inasmuch as all the positive features of the human body derive from the soul, until the soul is present there is no human being.
- Professor Pennington's list of church positions through time
- Religious Tolerance's list of Catholic positions
- Wikipedia, Christianity and abortion
- Bishops Respond to House Speaker Pelosi’s Misrepresentation of Church Teaching
- Cardinal Justin F. Rigali and Bishop William E. Lori Response from Catholic Bishops. This response is misrepresenting her argument.