I'm fairly certain that the Catholic Church has issued a definitive teaching on this subject. That the soul is created at the moment of conception. Ideally an answer would cover every created soul (including me, you, Adam, Eve, Jeremiah, David, The Blessed Virgin Mary and Jesus Christ)

To answer fully your question, let me affirmed first that Origen view on pre-existence was truly condemned by the Catholic Church.

The Origenistic doctrine of pre-existence was condemned by the Church as incompatible with revelation. A Council of Constantinople (543 A.D.) anathematized those who "assert the fabulous pre-existence of souls, and the doctrine of the Apocatastasis, which logically flows therefrom...- Fr. Hardon thesis: In man there is one rational soul, which is immortal and imediately created by God alone.

To answer Canonically your question let's isolate first Adam & Eve as the Church Teaching decreed by Pope Pius XII declared in his encyclical “Humani Generis:” that a soul was immediately created at the moment of conception will not be appropriate.

"As Pope Pius XII declared in his encyclical “Humani Generis:” “The teaching authority of the church does not forbid that, in conformity with the present state of human sciences and sacred theology, research and discussions on the part of men experienced in both fields, take place with regard to the doctrine of evolution, insofar as it inquires into the origin of the human body as coming from pre-existent and living matter - for Catholic faith obliges us to hold that souls are immediately created by God.” (n,36)

But, pondering on Genesis1:27 after God had formed Adam;when the word stated was "formed" is this the equivalent of "conception" when the Church teaches the soul was immediately created and infused?

The answer is YES! Looking at Jeremiah1:5 passage God also used the word "formed";.."Before I formed you in the womb....the action of God were the same for Adam & Jeremiah.

"And the Lord God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul."(Genesis1:27)

It would be wise to accept that when God formed Adam, it means while the body is being formed the soul was also formed immediately too, but only devoid of "sanctifying grace" until God breathe in Divine Life that makes Adam a Living soul meaning the "sanctifying grace or the spirit of God was poured into his soul in a degree of Original Holiness Justice only God knows.

This reflection is supported by numerous passages in scriptures;

"The Spirit of God has made me, and the breath of the Almighty gives me life.(Job 33:4)

"But it is the spirit in man, the breath of the Almighty, that makes him understand.(Job 32:8)

"The natural person does not accept the things of the Spirit of God, for they are folly to him, and he is not able to understand them because they are spiritually discerned."(1 Corinthians 2:14)

So the first man Adam was composed of body & soul with the spirit of God poured into his soul.

So, in Job passages we can see although Adam was already formed having "body & soul", this state is a dead soul without the "spirit of God or the sanctifying grace imparted into the soul" for it to enable to commune,understand the things of God and enjoy the friendship with God.

This is also very clear when Adam fall as the lost of 'sanctifying grace" brings death to the soul of Adam.

"For as the body apart from the spirit is dead, so also faith apart from works is dead."(James2:26)

"And you were dead in the trespasses and sins in which you once walked, following the course of this world, following the prince of the power of the air, the spirit that is now at work in the sons of disobedience— among whom we all once lived in …"(Ephesians 2:1–5)

How about Eve? since she was also formed, it follows that her soul was immediately formed too like Adam, but we can see that Eve was already pre-existed in the prophetic mind of God when he said the prophetic word "male & female He created them" although in reality Eve does not yet exist.

We can view the passage in the Day 6 of God creation when He uttered the creative word;

"Then God said, “Let us make mankind in our image, in our likeness, so that they may rule over the fish in the sea and the birds in the sky, over the livestock and all the wild animals,[a] and over all the creatures that move along the ground.” So God created mankind in his own image, in the image of God he created them; male and female he created them."

But since the Church condemned Origen view of pre-existent created soul separated from the body, this God word "male & female He created them" on Day 6 following a Day of Rest in the 7th day is only a prophetic word as Jesus revealed that the Abba Father continue to work in the Gospel of John;

“My Father is always at his work to this very day, and I too am working.” (John5:17)

The closest analogy we can have is with Mary, as scriptures stated that She is also a creature conceived and born in a Mother's Womb, the only difference is Mary was conceived free from original sin.

CCC492 The "splendor of an entirely unique holiness" by which Mary is "enriched from the first instant of her conception" comes wholly from Christ: she is "redeemed, in a more exalted fashion, by reason of the merits of her Son".136 The Father blessed Mary more than any other created person "in Christ with every spiritual blessing in the heavenly places" and chose her "in Christ before the foundation of the world, to be holy and blameless before him in love".137

The most Blessed Virgin Mary was, from the first moment of her conception, by a singular grace and privilege of almighty God and by virtue of the merits of Jesus Christ, Savior of the human race, preserved immune from all stain of original sin.(Pope Pius IX, 1854)

Viewing Jesus soul was "begotten" and Mary's soul was immediately infused from the moment of conception. We can see that Jeremiah case was no different, the only word that bring some additional pondering is the word "Before I formed you in the womb, I knew you"

The word "I knew you" cannot be clearly seen as "pre-existent soul" as it implied more on God talking about He knew what purpose or mission He would give to Jeremiah as clear out by the following words;

...And before you were born I consecrated you; I have appointed you a prophet to the nations."(Jeremiah1:5)

and the above passages speak of God pouring the "sanctifying grace" to Jeremiah's soul in advance by virtue of God's appointing his mission.

The only question I have with this passage is, does Jeremiah sanctification includes cleansing not just of original sin but even removal of the stain of sin? The passage is not clear whether Jeremiah's soul was cleanse from the "stain of original sin" as we know that Baptism only cleanses us of Original Sin but not the complete removal of the stain.

We can likened Jeremiah to St.John the Baptist as they were both in the Womb when they received sanctifying grace only difference is St.John the Baptist was already six months old.

But the big difference here is,God is the one who consecrated Jeremiah while St.John the Baptist sanctification happened due to the Presence of Mary bearing the Child Jesus and the Holy Spirit overshadowing Her and Mary's FIAT accepting the Will of the Father. So, the Trinitarian Faith and Witnessing of Mary enables Her to impart the Sanctifying Grace needed by St.John the Baptist. Could this event speak also of Mary's pre-figuring Her role as Mediatrix of All Graces. As we can see from the life of St.Joseph, he also is a receiver of all the Graces that is Overflowing from the Theotokos. As the name of St.Joseph means;

Joseph is a masculine given name originating from Hebrew, recorded in the Hebrew Bible, as יוֹסֵף‬, Standard Hebrew Yossef, Tiberian Hebrew and Aramaic Yôsēp̄. The name can be translated from Hebrew יוסף יהוה‬ yosef YHWH as signifying "Yahweh/Jehovah shall increase/add". ... In Persian the name is called "Yousef".

St.Joseph increasing his graces due to the presence of Mary Mediatrix of All Graces as Jesus had not yet received the Anointing from the Baptism in the River Jordan.

**In conclusion, I embraced the teaching of the Catholic Church that the souls of all man including Jesus,Mary, St.Joseph,St.John the Baptist,Jeremiah, David, and all human being. Also by virtue of the word "formed" likened to "conception" we can also view Adam & Eve soul was immediately formed alongside of the their body. So, the point of reference of the exact time soul was infused for all Mankind including Jesus,, Mary, St.Joseph and all the rest of Mankind including our first parent eventhough they were not conceived in the Mother's Womb but God had "formed" them also was likened to "conception" thru His Hands where Creation emanates.

Lastly, to provide a basis that Jesus although composed of Two Natures (Human & Divine) follows the universal law of conception subject to all mankind. As Archangel Gabriel revealed in the Mystery of the Annunciation;

"Behold, you will conceive and give birth to a son, and you shall give Him the name Jesus.(Luke1:31)

Jesus human but divine soul was definitely not "created" as the Church teaches that Jesus was "begotten" not made co-substantial with the Father. Jesus revealed that He became man in all things except sin.

St. Paul in his letter to the Philippians, we read, “Christ Jesus, though he was in the form of God, did not regard equality with God something to be grasped. Rather, he emptied himself, taking the form of a slave, coming in human likeness; and found human in appearance, he humbled himself, becoming obedient to the point of death, even death on a cross.”

Jesus human but divine soul "pre-existed in the bosom of the Father in eternity but infusion is the same to all mankind as Archangel Gabriel also used the word "conceived/conception".

The Great Mystery is the "pre-existence" of the soul of Mary if there's an official Church doctrine that explicitly said Mary's soul pre-existed in eternity too like Jesus. If Jesus divine soul pre-existed in the bosom of the Father, does Mary "Immaculate Soul" also pre-existed in the Will/Heart of the Father in the beginning before creation time begin?

To support the reflections on Mary's soul pre-existence as the word in Ephesians1:3-5 might also includes other Prophets,Patriarchs and Saints in the list of chosen or predestined souls before the foundation of the world. Mary had to surpassed pre-destination and must prove that She is above not only to man but even to all the angels.

We know that Genesis1:3 is the start of Creation Time, when God said "LET THERE BE LIGHT".

And deciphering Genesis1:1 word "In the beginning God created the Heavens and the earth" translating this to Hebrew word is "BERESHIT BARA ELOHIM" and would reveal the Secrets of God's Divine Plan or God's Blueprint for the Salvation of Mankind.

The Hebrew word "BERESHIT BARA ELOHIM" in tetragrammaton means "The Son of the Almighty God offers His life on the Cross and the graces flowed thru the sea".

Jesus in Genesis: 1. The First Word of the Bible (YouTube)

This prove the Primacy of Jesus Humanity and pre-existence of His soul before creation time begin. But look at the mystery word "sea", when we translate this to Hebrew it would become Miryam or Mary.

Does it speak of Mary's pre-existence? lets continue.. Genesis1:2 is where Mary's presence was revealed in the prophetic mind of God.

"Now the earth was formless and empty, darkness was over the surface of the deep, and the Spirit of God was hovering over the waters."(Genesis1:2)

Now the word "hovers" also means "overshadowing", and the waters that the Holy Spirit is hovering is in the Pure Womb of Mary to form the Logos.

With this two passages, I embraced the reflections that Mary's "IMMACULATE SOUL" pre-existed in the Will/Heart of the Abba Father.

Genesis1:1 ; is the "Way of the Cross" offered by Jesus for the Salvation of Mankind, meaning Jesus was already crucified in the prophetic Mind of God even before the Creation Time Begin.

Genesis1:2; Is the "Mystery of the Incarnation" following the revelation that all the graces won by Jesus Christ on the Cross flowed thru the Sea or flowed thru Mary. That's why Mary is called Mediatrix of All Graces a vessel/sea.

So, this answer is Full and Complete telling the time of the soul was infused at the moment of conception and proving the Jesus and Mary's soul 'PRE-EXIST" in the beginning.

Jesus human soul "pre-existence" is at the bosom of the Father means apart or co-substantial that's why His origin was Divine. And I remember the word of Blessed Archbishop Sheen on the Blessed Virgin Mary, Mary is God's Dream. When God Almighty Dream, He Dream in eternity outside of time. God already possessed Mary in eternity. She is already a reality in God's Volition. But unlike Jesus, Mary was not co-substantial as "To Dream" means an object is not part of you but something you DESIRE to have. But since God creative word cannot return to Him void (Isaiah55:11).All His creative word that was uttered from Day1 to Day6 of creation will all unfold in the fullness of time not at once as God planted seeds with the cooperation of and governance of created man.

**The Creation was finished in six days and God rested in the 7th Day. The Divine Plan of Salvation will end also in 7 Days meaning 7,000 years as 1,000 years is only 1 Day to God.(1Peter3:8)

2,000 years God the Father RENEWED the earth with Flood. (Baptism with Water)

2,000 years God the Son RENEWED the earth with Blood. (Baptism with Blood)

2,000 years God the Holy Spirit will RENEW the earth with FIRE. (Second Pentecost/Baptism with Fire as Jesus wanted to see our Hearts already burning when He return.)

How about the 1,000 years, what is the purpose of Eucharistic Era where Satan will be chained for a thousand years?**

This is MEAT and not milk and can only be fathom by matured christian.

Brothers, I could not address you as spiritual, but as worldly—as infants in Christ. I gave you milk, not solid food, for you were not yet ready for solid food. In fact, you are still not ready,(1Corinthians3:2)

At what point is a new soul created according to the Catholic Church?

Short Answer

1. DIVINE TRUTH

Based on the on the direct WORD of the Abba Father the Maker of Heaven and Earth when He sent Archangel Gabriel to the Blessed Virgin Mary to relay His message.

"And, behold, thou shalt "CONCEIVE" in thy womb, and bring forth a son, and shalt call his name Jesus.(Luke1:31)

Almighty God Maker of Heaven and Earth said Mary will "CONCEIVE" first.

So, it's very clear that the point of reference where human life begins must be at the moment of "CONCEPTION".

2. APOSTOLIC TRUTH

The Faith of the Apostles was Decreed in the Council of Nicea 325AD.

"I believe in God the Father Almighty Creator of Heaven and Earth.And in Jesus Christ His only Begotten Son who was "CONCEIVED" by the power of the Holy Spirit...."

3.DOGMATIC TRUTH

Since, God only said "you will CONCEIVE first" but did not clarify when is the period of conception, then God inspired & explicitly defined the point of reference thru His Wisdom on the birth of the Blessed Virgin Mary.

The Catholic Church defined the Immaculate Conception "at the FIRST INSTANCE of conception"

Now, that the point of reference where human life begins is dogmatically clear. there's should be no more further discussion as this was already proclaimed a DOGMATIC TRUTH.

The defined dogma of the Immaculate Conception states:

We declare, pronounce, and define that the doctrine which holds that the most Blessed Virgin Mary, in the first instance of her conception, by a singular grace and privilege granted by Almighty God, in view of the merits of Jesus Christ, the Saviour of the human race, was preserved free from all stain of original sin, is a doctrine revealed by God and therefore to be believed firmly and constantly by all the faithful."(1854 Pope Pius IX, declared ex cathedra)

With these three Divine Revelation pointing clearly to "conception" as the point of reference where soul is immediately infused whether created, formed or pre-existent. The DIVINE TRUTH, APOSTOLIC TRUTH and DOGMATIC TRUTH clearly is the basis of the succeeding Pope pronouncement that Life is Sacred and must be respected and protected at the moment of conception.

4. Catechism of the Catholic Church, Pope Encyclicals

St.Pius XII (Humani Generis), St.Pope Paul VI (Humanae Vitae) and St,John Paul II the Great (Evangelium Vitae) and the Catholic for 2000 years clearly upheld the teaching that;

CCC 366: "The Church teaches that every spiritual soul is created immediately by God - it is not "produced" by the parents - and also that it is immortal: it does not perish when it separates from the body at death, and it will be reunited with the body at the final Resurrection.

Since the Clergy and the Laity are guided by Canon Law, all the faithful must assent to the faith of the Church as written in Canon750

Can. 750 §1. A person must believe with divine and Catholic faith all those things contained in the word of God, written or handed on, that is, in the one deposit of faith entrusted to the Church, and at the same time proposed as divinely revealed either by the solemn magisterium of the Church or by its ordinary and universal magisterium which is manifested by the common adherence of the Christian faithful under the leadership of the sacred magisterium; therefore all are bound to avoid any doctrines whatsoever contrary to them.

Further more:

The featured question wanted to include the soul of Jesus,Mary, Adam & Eve, Jeremiah, David and all mankind.

Proposed Dogmatic definition;

"all the souls of mankind are immediately created or immediately infused at the moment of conception or at the moment of formation."

1. Jesus & Mary is defined by "immediately infused" at the moment of conception. (the word INFUSED is needed as Jesus & Mary's soul was pre-existent the Church Teaches they are the New Adam & New Eve, they are created in the "order of grace" and not in the "order of nature" like the rest of mankind starting from Adam.)

2.Adam & Eve was defined by "immediately created at the moment of formation.(to accomodate their unique creation by formation and not thru the womb by conception.) The word "formed" by God will be supported by the Catholic Church teaching on CCC365;

365 The unity of soul and body is so profound that one has to consider the soul to be the "form" of the body:234 i.e., it is because of its spiritual soul that the body made of matter becomes a living, human body; spirit and matter, in man, are not two natures united, but rather their union forms a single nature.

3. Jeremiah, David and all mankind by "immediately created at the moment of conception."

In closing, the Divine Truth alone alone straight from the mouth of an Archangel Gabriel is enough to convince us that human life started right at the moment of conception and even further clarified by the Church thru Dogmatic Definition stating that "at first instance of conception" the soul was immediately created or infused.

So, all the People of God must assent to the Church Teaching of St.John Paul II the Great that life must be protected at the moment of conception.

TL;DR

The last official pronouncement on this issue by the Catholic Church was in 1987 by the Congregation for the Doctrine of the Faith, which reaffirmed the value of life from conception but did not settled the issue of the time of infusion of the soul in the body.

The second edition of the New Catholic Encyclopedia (published in 2003) has a comprehensive article on the soul. One of the subsections is titled "Time of Soul's Origin". I quote in extenso from it. The article first discards the view of the pre-existence of the soul (i.e the existence of the soul before being united with matter), which is officially considered heretical (Enchiridion symbolorum, 403, 456). Thus, it follows that

The soul is created by God at the time it is infused into matter, i.e., when it is substantially united with an embryo appropriately disposed to receive it and form a man. ... Exactly when this happens is more controversial, and still an open question with scholastic philosophers of high standing on both sides. All agree that since the soul is the principle of vital operations, the human soul is present when there is specifically human operation. Because there is evidence of specifically human operations from the first moment of conception, a majority assert that the human soul is present then.

Then the article mentions the debate on when one can refer to the embryo as "human". This is relevant because having a soul is essential for the human being. The article says:

Aristotle thought that he was unjustified in asserting true human life in the male before the embryo was 40 days old and in the female, before 80 to 90 days. St. Thomas followed him in teaching a succession of forms, the embryo having first a vegetative soul and later a sensitive one, before the human soul finally arrives. Modern studies in embryology reveal that at the moment sperm and ovum unite and the two pronuclei fuse, an orderly process of development begins with a definiteness governed by the pattern of the DNA molecule. The new individual is characterized by the resulting unique constellation of genes and chromosomes before the zygote divides for the first time. ... Embryology considers the living body from the one-cell stage onward to be a human individual, not some general plant or animal that will become human in 40 or 80 days.

If one were to wait for clear evidence of rational activity before concluding belief in the existence of a human soul, it would not be a matter of days, but of years. As long as the embryo is clearly the product of human generation, it has a human nature even if severe organic defect prevents it from ever exercising any rational activities, as in the case of some developmentally disabled individuals. Examination of the fetus through its early stages gives no clue as to when one can draw the line. The available evidence seems to force one back to the very moment of conception.

A minority view points to the problems of fragmentary life, transplants, divisibility of lower animals such as worms, and human identical twins as arguments in favor of the mediate animation held by St. Thomas Aquinas, which seems to handle these difficulties more neatly.

Then, there is the question on the Church pronouncing on these issues:

The debate over whether the soul is immediately infused or arrives at some later point in embryological development was not the most pressing moral problem faced by the Church during the rise of legalized abortion. Nonetheless, the much referenced footnote 19 of the Declaration on Procured Abortion (1974) took note of the debate between proponents of immediate and delayed hominization and stated that:

It is not within the competence of science to decide between these two views, because the existence of an immortal soul is not a question in its field. It is a philosophical problem from which our moral affirmation remains independent . . . supposing a later animation, there is still nothing less than a human life, preparing for and calling for a soul in which the nature received from parents is completed. One finds here two important points: the question of when the soul is infused is not one that can be decided by any empirical means, and even if the soul were to be infused at some later point in embryological development, the zygote that is present at fertilization is surely a human life. As such it deserves the same respect as is due to any other human being.

With the discovery of human genome, and the recognition that it contains the entire code for the epigenetic unfolding of the human being, there was a growing conviction among many Catholic theologians that personhood must begin at conception. Others, in spite of this new evidence, insisted that the lack of individuality in the early embryo, which is capable of twinning in its earliest stages, or the supposed absence of a proper material foundation to support the human soul, such as the ‘‘primitive streak’’ (primitive spinal cord and brain), which appears at approximately 14 days, left the question at best undecided or perhaps even settled in favor of delayed hominization on scientific grounds.

In 1987 the Congregation for the Doctrine of the Faith entered this debate with Donum vitae: Instruction on Respect for Human Life in its Origin and on the Dignity of Procreation. The document addressed a panoply of moral issues related to modern reproductive technologies, but it took special note of the question of the origin of the human soul. The Congregation stated that it was ‘‘aware of the current debates concerning the beginning of human life, concerning the individuality of the human being and concerning the identity of the human person’’ and then, calling attention to recent findings of science that indicated that a ‘‘new human individual’’ is constituted at the moment of conception, remarked:

Certainly no experimental datum can be in itself sufficient to bring us to the recognition of a spiritual soul; nevertheless, the conclusions of science regarding the human embryo provide a valuable indication for discerning by the use of reason a personal presence from this first appearance of a human life: how could a living human creature not be a human person? The Magisterium has not expressly committed its authority to an affirmation of a philosophical nature, but it constantly reaffirms the moral condemnation of any kind of procured abortion.

The entry concludes:

Thus, while leaving the door open for the possibility of later animation, Donum vitae placed the weight of the Vatican on the side of those who view a personal presence in the human zygote; however, because this document did not make its judgment definitive, the debate on this important topic continues. What is clear beyond any doubt is that, in the view of the Church, ‘‘the fruit of human generation, from the first moment of its existence, that is to say from the moment the zygote is constituted, demands the unconditional respect that is morally due to the human being in his bodily and spiritual totality.’’

Finally, it is clear that this issue is to remain central in theological and philosophical debate. The article ends with the following passage:

The prospect of so-called therapeutic human cloning, in which human clones are made and destroyed for research purposes, and the desire among certain members within the scientific community to exploit the unfortunate plight of frozen human embryos, has greatly heightened the stakes in this debate and promises to keep the question at the forefront of philosophical and theological discussion well into the twenty-first century.

The Magisterium of the Catholic Church has not made a definitive pronouncement about the precise moment in which the soul is infused to the embryo. The most current magisterial document on the subject is the 1995 Encyclical Evangelium Vitae by Pope John Paul II [1], dealing with abortion, where he wrote:

Furthermore, what is at stake is so important that, from the standpoint of moral obligation, the mere probability that a human person is involved would suffice to justify an absolutely clear prohibition of any intervention aimed at killing a human embryo. Precisely for this reason, over and above all scientific debates and those philosophical affirmations to which the Magisterium has not expressly committed itself, the Church has always taught and continues to teach that the result of human procreation, from the first moment of its existence, must be guaranteed that unconditional respect which is morally due to the human being in his or her totality and unity as body and spirit: "The human being is to be respected and treated as a person from the moment of conception; and therefore from that same moment his rights as a person must be recognized, among which in the first place is the inviolable right of every innocent human being to life".59

[...]

Throughout Christianity's two thousand year history, this same doctrine has been constantly taught by the Fathers of the Church and by her Pastors and Doctors. Even scientific and philosophical discussions about the precise moment of the infusion of the spiritual soul have never given rise to any hesitation about the moral condemnation of abortion.

59 Congregation for the Doctrine of the Faith, Instruction on Respect for Human Life in its Origin and on the Dignity of Procreation Donum Vitae (22 February 1987), I, No. 1: AAS 80 (1988), 79.

Thus, there is no Catholic de fide doctrine about the moment of the infusion of the spiritual soul. Notably, St. Thomas Aquinas held the Aristotelian notion that the spiritual soul was infused 40 days after conception in male embryos and 90 days after conception in female embryos, and devotes an article of his Summa Theologica to defend this notion in view of its evident incompatibility with magisterial and patristic statements about the Incarnation of the Word (ST III, q.33, a.2) [2].

The patristic and magisterial statements in question, as presented by St. Thomas himself in Objections 1 and 2, are:

For Pope Leo says (Ep. ad Julian.): "Christ's flesh was not of another nature than ours: nor was the beginning of His animation different from that of other men."

what Augustine says (De Trin. iv), where he proves that Christ was in the Virgin's womb for the space of nine months:

what Pope Leo says (Serm. iv in Epiph.): "They found the child Jesus nowise differing from the generality of infants."

Then St. Thomas, after stating (correctly) in the answer that "in the first instant of its conception Christ's body must needs have been animated by the rational soul", then tries to argue, in the answers to objections 1 and 2, that this is compatible with the infusion of the soul 40 days after conception in ordinary human embryos, by positing that Jesus was conceived with his body in an initial state of development which was the same as that of an ordinary 40-day embryo. But it is evident that this necessarily implies one of the following:

• either Jesus' pregnancy lasted 40 days less than an ordinary human pregnancy, against Augustine's statement,

• or Jesus was born with the size and weight of a 40-day old baby, against Pope Leo's statement in Serm. iv in Epiph.

This is simple logic and there is no way to circumvent it. The argument that St. Thomas presents to escape from this unavoidable conclusion fails by self-contradiction, as anyone taking the time to follow it can verify by themselves.

Conversely, the magisterial and patristic statements quoted by St. Thomas, while not definitive, show that the Catholic most probable theological position on the moment of the ensoulment is that it occurs at conception.

References:

[1] EVANGELIUM VITAE

[2] Whether Christ's body was animated in the first instant of its conception?

At what point is a new soul created according to the Catholic Church?

The Church has not pronounced definitively on this question because at present the Church does not know. The Magisterium of the Catholic Church has not made a definitive pronouncement about the precise moment in which the soul is infused into the fetus. Pope John Paul II is very clear on this matter in his encyclical letter, Evangelium Vitae.

Although the Church as of yet, has not made an infallible statement on this subject, it is obvious that the Church at the present moment in time favours the position that the human immortal soul is created at the very moment of it's conception within the womb.

Even though the Catechism of the Catholic Church (October 11, 1992) points towards human life starting at the very moment of conception; this subject has not been taken up in a papal encyclical letter or bull. Let us not forget that even Pope St. John Paul II stated that the Church had not made any affirmations on this subject in his encyclical letter, Evangelium Vitae (March 25, 1997).

Throughout Christianity's two thousand year history, this same doctrine has been constantly taught by the Fathers of the Church and by her Pastors and Doctors. Even scientific and philosophical discussions about the precise moment of the infusion of the spiritual soul have never given rise to any hesitation about the moral condemnation of abortion.

60 Furthermore, what is at stake is so important that, from the standpoint of moral obligation, the mere probability that a human person is involved would suffice to justify an absolutely clear prohibition of any intervention aimed at killing a human embryo. Precisely for this reason, over and above all scientific debates and those philosophical affirmations to which the Magisterium has not expressly committed itself, the Church has always taught and continues to teach that the result of human procreation, from the first moment of its existence, must be guaranteed that unconditional respect which is morally due to the human being in his or her totality and unity as body and spirit: "The human being is to be respected and treated as a person from the moment of conception; and therefore from that same moment his rights as a person must be recognized, among which in the first place is the inviolable right of every innocent human being to life".

The Catechism of the Catholic Church states the following:

366 The Church teaches that every spiritual soul is created immediately by God - it is not "produced" by the parents - and also that it is immortal: it does not perish when it separates from the body at death, and it will be reunited with the body at the final Resurrection. Catechism of the Catholic Church

**Only Rome can interpret Vatican legislative texts and unclear statements in doctrine, either through the Pontifical Council for Legislative Texts or the Congregation for the Doctrine of the Faith. Here is what Nathaniel's comment, which I would like to add, has to say:

Based on my reading of Ludwig Ott, "created immediately by God" in §366 seems to mean "created at the moment of the soul's unification with the body." So it's a much clearer statement than it might look. The relevant section of Ott is page 100; he says that this is sent certa but perhaps it's at a higher level now that it appears in the Catechism (not sure how that works).

A much clearer statement than this is needed in order to pinpoint the time when the soul and the body are united. The Catechism of the Catholic Church §366 does not state when this happens, only that the spiritual soul is created immediately by God. The statement "immediately created by God" implies that only God and God alone creates human immortal souls yet does not say when that precise moment in time their souls were infused into their bodies.

In any case the Church demands that respect of human life from the very moment of it's conception until it's natural end must be maintained by all Catholics.

Human life must be respected and protected absolutely from the moment of conception.

From the first moment of his existence, a human being must be recognized as having the rights of a person - among which is the inviolable right of every innocent being to life.

Before I formed you in the womb I knew you, and before you were born I consecrated you. - Catechism of the Catholic Church (2270)

Thus the Catholic Church has not pronounced on this subject, modern theologians are now in favour of the idea that human life commences at the very moment of conception. Human life is not human unless the immortal soul and the body are united.

It is sometimes claimed that Thomas Aquinas believed that the unborn did not acquire a soul until several weeks after conception. This is not true. Aquinas believed that the unborn had a soul (a rational, human soul) from the time it was conceived. However, following Aristotelian science, he (and a few other Western writers) thought that conception was an extended process that did not finish until forty or ninety days into the pregnancy: "The conception of the male finishes on the fortieth day and that of the woman on the ninetieth, as Aristotle says in the IX Book of the Animals" (Aquinas, Commentary on III Sentences 3:5:2).

Aquinas was correct that the unborn receive their souls at conception; he was merely mistaken on when conception was finished, due to the lack of available science. As modern medicine has shown, conception in humans occurs almost instantaneously, as soon as the sperm and the ovum unite. This joining may occur as soon as twenty minutes after the marital act.

Aquinas and a few other medieval Western writers held the forty-to-ninety-day conception theory, but the biological discoveries of the nineteenth century proved it wrong. The view provides little comfort for abortion advocates today for a variety of reasons. It was based on primitive science. It draws a distinction between males and females that many today would regard as sexist. It was held by only a few writers. No single theologian (even Aquinas) speaks for the Church. The writers who favored the theory also opposed abortion as intrinsically evil at any stage.

The Didache, one of the earliest Christian writings outside the New Testament (c. A.D. 70) states, "You shall not procure an abortion, nor destroy a newborn child" (2:1). The Letter of Barnabas (c. A.D. 74) states, "You shall not murder a child by procuring abortion; nor, again, shall you destroy it after it is born" (19). Numerous other references in the early Christian writers condemn abortion as murder. - When Babies Get Their Souls

Whatever St. Thomas truly thought on the subject modern science is making great headway in the field of studies of the unborn.

Summa Theologica delineates St. Thomas Aquinas’s opinion on the moral status of the embryo or fetus and the act of abortion. His discussion of sin, morality, and murder indicates his views on the development of life within the womb. These sections show that Aquinas believed in the progression of life from a “vegetable”-like, unanimated state to an animal life and finally to a human, animated state. Summa Theologica offers no defense of abortion as a permissible act at any stage in the pregnancy, but it does specify that once the fetus has become animated (when he believed ensoulment of the living human being took place), it is homicide to kill it. This measure of ensoulment or delayed hominization (the belief that the embryo or fetus was not a human life with a soul until a particular event after conception) is typically equated with the stage at which quickening took place—defined by Aristotle as forty days for boys and eighty days after conception for girls.

It is the concept of delayed hominization that seemingly pits these comments of St. Thomas Aquinas against the modern Roman Catholic Church; when it comes to ensoulment, the Church now defends the position that an embryo is infused with a human soul upon fertilization, making any intentionally procured abortion a sin of murder (because it kills a living being with a human soul). St. Thomas Aquinas’s opinion on abortion and fetal development receives much attention from people on both sides of the debate over abortion. Typically, pro-choice advocates claim that Aquinas’s position shows an inconsistency in Church belief throughout history on the topic and a defensible option for pro-choice Catholics, while pro-life advocates point out that Aquinas never discusses abortion as an acceptable option and furthermore would most likely not have maintained his delayed hominization theory had he been privy to the marvels of modern science. - The Embryo Project Encyclopedia

As for Adam and Eve, the when their souls entered their bodies, the Church has of yet not even declared that they were created as the Book of Genesis states or whether they were born as a matter of course through evolution.

Pope Pius XII in his encyclical letter Humani Generis permits Catholics to believe that both Adam and Eve may have been born through a process of evolution and if this were to be the case, both would be the soul would be infused into their souls at the same time as the rest of the human race:

36. For these reasons the Teaching Authority of the Church does not forbid that, in conformity with the present state of human sciences and sacred theology, research and discussions, on the part of men experienced in both fields, take place with regard to the doctrine of evolution, in as far as it inquires into the origin of the human body as coming from pre-existent and living matter - for the Catholic faith obliges us to hold that souls are immediately created by God. However, this must be done in such a way that the reasons for both opinions, that is, those favorable and those unfavorable to evolution, be weighed and judged with the necessary seriousness, moderation and measure, and provided that all are prepared to submit to the judgment of the Church, to whom Christ has given the mission of interpreting authentically the Sacred Scriptures and of defending the dogmas of faith. Some however, rashly transgress this liberty of discussion, when they act as if the origin of the human body from pre-existing and living matter were already completely certain and proved by the facts which have been discovered up to now and by reasoning on those facts, and as if there were nothing in the sources of divine revelation which demands the greatest moderation and caution in this question. - Humani Generis

Here too we see that the souls of Adam and Eve were immediately created by God implies that only God and God alone creates human immortal souls yet does not say when that precise moment in time their souls were infused into their bodies.

Nota Bene (Liturgical Note):

We must take into account that the Church declared Mary's Immaculate Conception a dogma of the Catholic Church in 1854, by Pope Pius IX. This is a binding doctrine on all Catholics and is not open to negotiation.

The Church in her great joy celebrates the Immaculate Conception of Mary with a great solemnity on December 8. In was declared a doctrine on December 8, 1854 by Pope Pius IX in his encyclical letter Ineffabilis Deus.

The defined dogma of the Immaculate Conception states:

We declare, pronounce, and define that the doctrine which holds that the most Blessed Virgin Mary, in the first instance of her conception, by a singular grace and privilege granted by Almighty God, in view of the merits of Jesus Christ, the Saviour of the human race, was preserved free from all stain of original sin, is a doctrine revealed by God and therefore to be believed firmly and constantly by all the faithful.

Declaramus, pronuntiamus et definimus doctrinam, quae tenet, beatissimam Virginem Mariam in primo instanti suae Conceptionis fuisse singulari omnipotentis Dei gratia et privilegio, intuitu meritorum Christi lesu Salvatoris humani generis, ab omni originalis culpae labe praeservatam immunem, esse a Deo revelatam, atque idcirco ab omnibus fidelibus firmiter constanterque credendam. Quapropter si qui secus ac a Nobis.

Original Sin affects the soul. Mary received the gift of the Immaculate Conception at the very moment of her conception, nine months before her birth (September 8). Thus it seems to follow that Mary's soul was created at the moment of conception.

There also exists a medieval pious legend or tradition that Our Lord died on March 25, the Feast of the Annunciation. (It is simply a pious legend). Although simply legend, it would mean that Our Lord had a human life here on earth of exactly 34 years , from the moment of conception to His dead on the Cross.

Both Jesus and Mary had real rational human souls! The soul of Mary would follow it's infusion of her soul as the rest of the human race. Our Lord's human soul most likely was infused at the moment of the Annunciation.

Is March 25 the historical date of the crucifixion?

Did the Annunciation and Good Friday coincide?

Even though the Church has not pronounced definitively on the precise moment in which the soul is infused into the fetus, it is all too obvious that the Church very strongly points to the very instant the sperm and egg are united within a woman.

The Catholic Church has not issued a definitive teaching on this topic. There are certain boundaries that have been established, e.g. that our souls have not always existed but rather were created by God, and that the soul is definitely present within the body at conception. The exact timing, however, is not known, and, indeed, the Church has no firm opinion on how, exactly, time works, or what, exactly, it is. For further reference, see the Time entry at New Advent.