Thomas Aquinas on Ensoulment

In our parish, we have a Q&A feature in our bulletin. The fodder for this is mined from a question container we keep in the student lounge. The question I drew for consideration last month was, “Didn’t St Thomas Aquinas teach that the human embryo didn’t receive a soul right away?”

Thomas based his stance on ensoulment on the rational beliefs of his day. The 13th century had no modern science as we understand it, and scholars of the time held that life arose spontaneously from non-living matter. When God infused a human soul into non-living matter, identifiably human qualities would appear. Without the benefit of microscopes and other techniques of observation within the human body, people of centuries ago were simply ignorant of the facts of conception. They had no knowledge of the genetic make-up of embryos. In the earliest stages of gestation, they did not perceive the human qualities that would be present if a human soul were there.

That said, Thomas held, as did most moral theologians, that abortion still constituted a grave sin. Despite not being perceived to have a soul, the contents of a woman’s womb and the semen of a man were still considered the “non-living” material that would produce a human being. This would be at the root of the Church’s teaching on masturbation: a moral Christian should honor what contributes to human life as she or he would honor human life itself.

Ensoulment has never been the Church’s main objection to abortion. It should also be pointed out that conception doesn’t always produce a unique human being. We know that twins or other multiples can emerge from a single fertilized human egg, or even that very early-stage multiples can fuse into one being. These facts do not detract from our moral beliefs on abortion.

Within my word-limit, did I cover the bases adequately? I’ve heard the quote (?) that Thomas held that male ensoulment took place at forty-day’s gestation and female at eighty. I’m leery about repeating that without attribution, so I didn’t mention it in my answer.

I continue to be perplexed by the focus on ensoulment in discussing what the Church has discussed on the nature of unborn life. On the other hand, it is fascinating conjecture to consider when we become ensouled beings. Neil and others may have more scholarly resources to offer in terms of what philosophers and theologians today are thinking. I step back from the limits of my own expertise on this one and concede the floor to others.


About catholicsensibility

Todd lives in the Pacific Northwest, serving a Catholic parish as a lay minister.
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13 Responses to Thomas Aquinas on Ensoulment

  1. Kevin in Texas says:

    That’s a fine answer, and none too general, either, Todd. Like so many issues in the moral sphere, it’s easy to miss the forest for the trees, and many who seek to push the limits of moral reasoning use that fact to great advantage to cloud what are often simple concepts to grasp from a natural law perspective.

    The ensoulment “debate” among Catholic abortion rights advocates and pro-lifers is one specific example of this muddying the waters. Leave the heavy lifting of ensoulment to moral philosophers, but also avoid making the simple mistake of attributing too much weight to centuries-old speculations based on understandings of science that were even older than that!

  2. Liam says:

    From the science side: modern mammalian embryology only dates as far back as the work of Karl Ernst von Baer in the latter half of the 1820s.

  3. Neil says:

    Dear Todd,

    I hope that this comment finds you both happy and well. I can’t claim to have read all the literature on the subject – nor do I have the literature that I have read close at hand. But I do think that your answer is quite good – you note that, for Aquinas, early abortion was always a grave sin, and that Aquinas’ metaphysics (if not his embryology!) can still be upheld.

    I don’t think that I would say that, for Aquinas, “life arose spontaneously from non-living matter.” The instrumental cause of human life for Aquinas is a “formative power” (virtus formativa) in the sperm, acting in conjunction with the sun. Furthermore, there were critics of delayed hominization and the “formative power,” and eventual changes in Catholic moral teaching, well before the advent of modern genetics.

    The key things, then, are

    1) As you imply, the recognizably human organization of the body occurs before Aquinas thought it did, so the rational soul can be present before he thought that it could.

    2) The development of the human organism is self-development that occurs from fertilization onwards, not the eventual result of the workings of a “formative power.” (See Richard Stith on the significance of this distinction, for instance, in my post here.)

    Incidentally, I don’t think that I’d bring up masturbation, either.


  4. Jim McK says:

    Dear Neil,

    This is A minor quibble, probably irrelevant to everything, but it is a slow morning so I am writing it.

    Aquinas distinguishes among types of souls. (probably in an attempt to reconcile Aristotle and the more common understandings of his time?) “There are five genera of powers of the soul. Of these, three are called souls, and four are called modes of living.” (ST I.78.1)

    Souls are typed by their “operations”, and so are called vegetative, sensitive and rational. A human fetus has a vegetative soul, meaning a soul that gives it life. At some point, he begins to react to his environment, signifying a ‘sensing’ soul. (I gender the child male so that female can be used of the mother if needed, but I mean boy or girl) A rational soul exists when the mind begins to work; this is what is called ensoulment.

    But the soul is there from the first moment of life, operating first as life, then also as sensing, and then rationally. It is a single soul, but operating in more ways as it grows. I think Aquinas would say it is always a human soul, but does not become a ‘rational soul’ until it begins to operate rationally, though there might be problems with that formulation.

    Thanks. now that I have thought that through, I understand some things better.


  5. Neil says:

    Dear Jim,

    Thanks, as always, for writing. I would agree with much of what you write. However, you claim that, “[The soul] is a single soul, but operating in more ways as it grows.” I think that Aquinas – and Aristotle – would suggest that we see a succession of souls as the matter of the fetus develops and becomes capable of receiving new formative principles.

    Eventually, then, the fetus becomes capable of receiving a rational soul, which is directly infused by God. This is the human soul.

    Thus, for Aquinas, early abortion is not homicide if it occurs before ensoulment, even if it is still a grave sin.


  6. Jim McK says:

    Dear Neil,

    That is where I started out yesterday, but I am not so sure after reading some Aquinas and Aristotle. I think it is a “succession of souls” in the same sense that child, adolescent, adult is a succession of people. It probably comes down to defining ‘soul’ more precisely, since my naive idea was somewhat different from Aristotle’s.

    In any event, the important thing is that a human soul exists from conception onwards, on which we agree. Would Aquinas agree with us? I think yes, but it is a complex issue on which there are different opinions, so don’t rely on my inexpert answer.

  7. Neil says:

    Dear Jim,

    If we look at the Summa Contra Gentiles, Aquinas writes,

    Therefore in the generation of animal and man, — these having the most perfect form, — there occur many intermediate forms and generations, and consequently destructions, because the generation of one being is the destruction of another. The vegetative soul therefore, which is first in the embryo, while it lives the life of a plant, is destroyed, and there succeeds a more perfect soul, which is at one nutrient and sentient, and for that time the embryo lives the life of an animal: upon the destruction of this, there succeeds the rational soul, infused from without, whereas the preceding two owed their existence to the virtue of the male semen.

    He seems to reject (what I take to be) your view earlier, when he writes:

    Upon this view [again, which I take to be yours – N]it would follow that numerically the same active power was now a vegetative soul only, and afterwards a sentient soul; and so the substantial form itself was continually more and more perfected: it would further follow that a substantial form was educed from potentiality to actuality, not instantaneously, but successively; and further than generation was a continuous change, as is alteration, — all so many physical impossibilities. There would ensue even a still more awkward consequence, that the rational soul was mortal.

    (See here for the text.)

    Regarding your question about a human soul existing from conception onwards, Aquinas would disagree based on medieval embryology. But we can suppose that a contemporary Aquinas, with the same metaphysics, would tend to agree.

    Thanks again.


  8. Jim McK says:

    Dear Neil,

    Thanks. Obviously, Aquinas disagrees.

    I was looking at the Summa Theologica, where the presentation is somewhat different, but not inconsistent with this. But I am not about to try parsing the problems of defining parts of souls!


  9. Rev. Leslie allen Stelter says:

    I am a truly 100% pro-life, Roman Catholic priest. I have always been so, since I became a priest on June 9, 1984. All Christians, all Jews, all Muslims, all Buddhists, must agree on this: The immortal, spiritual, rational, human person first exists between 130-140 days after conception, when “upper brain birth” happens. St. Thomas Aquinas said a person dies because his or her body looses this natural dispostion to keep the soul and body together. All throughout a person’s life span this natural disposition is only in that upper body organ we know as the “upper brain.” So the time of “upper brain death” is the time when a human person leaves their body behind and goes into eternity. We priest must know when that happens, because we can only give the Sacrament of Anointing to a living human person. The misuse of this sacrament would be a “sacrilege” which would be more evil than a procured abortion is or murder is. Mary’s pregnancy was only about 139 days long, because Jesus assumed our human flesh, our human nature, and not the mortal, human nature of a human zygote, mortal human embryo, or unformed human, mortal fetus. All these natures are mortal, just like the nature of the sperm being or the ovum being, even though they too are human, are mortal. They must cease to exist, so that, by nature, our human, immortal nature can exist. So, if we celebrate the Feast of the Annunciation on Marcy 25, we must, if we want to be 100% pro-life, protecting every human person’s right to life, we need to change the Church’s liturgical calendar completely so that Advent starts in June, Christmas is celebrated August 8th. Mary’s birth is only about 139 days after Dec. 8th and the Birth of John the Baptist is only about 14 days before August 8th. Jews say ensoulment happens 266 days after conception. That is about 130-140 days after “upper brain” birth. The common Catholic opinion of ensoulment is also about 130-139 days before “upper brain” birth. It is just as dangerous, because both positions have to maintain that the “upper brain” is not the organ that contains the natural dispostion of the body which is necessary to be in the body to keep body and soul together, that is, to make rational, immortal life possible. WE say that both wrong opinions put all the lives of all human person’s living on earth, at risk! That is why the Church must proclaim as a dogma that ensoulment happens 130-139 days after conception, somewhere, for each person, within only that time frame. They must also define the time of death as the time of “upper brain death,” that is, when a person leaves his body behind and goes into eternity. I ask people to please inform the Pope and all Christians and all Jews, and all Muslims, etc. that this now must be done in order to safeguard the right to life of every human person equally.

    My email is My address is Rev. Leslie Stelter, P. O. Box 37, Coloma, WI 54930-0037 USA I also want the Pope to define Full of Grace, the ever-Virgin Bride of Our Lord Jesus Christ, in the order of grace, as our Co-Redemptrix and as our Spiritual Mother. That is why the arch-angel addressed her with the new name of Zion, Full of Grace, instead of saying “Hail, Mary,” which is a big mistake on our part; it should be, “Rejoice, Full of Grace! The Lord is with Thee! Blessed art thou amonst women!” Zion was the Bride of the Lord in the OT. Full of Grace is the ever-Virgin Bride of Our Lord Jesus Christ in the NT, and she is the New Eve in this way. She was united to her Bridegroom at the Last Supper, when the New Adam gave her his entire body and blood, not just a rib from his side, so that when his heart was pierced, blood and water could flow out to us through the Immaculate Heart of His Bride, Full of Grace. That is why Jesus said to St. John, only from the cross, (My)”Son, behold Thy Mother!” St. Paul calls Christ our spiritual father.

    God keep you all safe until you are with him in heaven,
    Fr. Leslie Allen Stelter

    “Evil triumphs when good men do nothing!” So let us all make these changes for the better together. Let us do this now.

  10. Scott Thomas says:

    I hope I am neither out of line nor wrong, BUT:

    There is no Catholic church in Coloma, Wisconsin. The nearest two Catholic churches to Coloma are Saint Paul’s in Plainfield, Wisconsin and Saint Joseph’s in Wautoma, Wisconsin. I have attended mass at both many times; in fact, the pastor of both, Father Robert Stegmann, married my wife and me. I am aware that the church in Plainfield has had a lot of different “guest” priests due to Father Stegmann’s cancer situation and that a deacon basically runs that parish. I am also aware that Waushara County, Wisconsin is popular with retirees and summer home owners, perhaps to include retired priests.

    Coloma, Wisconsin is in the Diocese of Green Bay. I could not find any record of a Father Leslie Allen Stelter in the Diocese of Green Bay.

    As I read “Father Stelter’s” rhetoric in his last paragraph, it seems to have the ring and tone of Old Catholic Church rhetoric. The Old Catholic Church is NOT part of the Roman Catholic Church, but a small splinter group. Central Wisconsin is a hotbed of the “Old Catholic Church,” the centerpiece of which is a “shrine” in Necedah, Wisconsin that has been condemned by bishops of the La Crosse Diocese from Bishop Treacy to then-Bishop/now-Cardinal Burke. I don’t know that the “post-Burke” bishops have issued any statements upon said “shrine.” (Necedah’s in the Diocese of La Crosse and just 30 miles down Highway 21 from Coloma.)

    I also wonder if the above is a Halloween prank, posted at two-something in the morning on Halloween, no less.

    I have heard many a homily in my four-plus decades that repeatedly refer to Christmas as the Incarnation…it seems to me that this position gives solace to “Catholics” like those on the U.S. Supreme Court and “Catholic” pro-choicers everywhere. I think it would be more coherently pro-life to say that the Annunciation (on March 25th, nine months before Christmas) is the Incarnation…but I’m a mere layperson.

    Interesting piece on ensoulment — I’m trying to get a better grip on Saint Thomas Aquinas as I have a number of friends who are staunch Thomists and my Catholic background has this big gap between the last book of the Bible and Vatican I in the 1870’s. Thank you!

    — In Christ Jesus Through Mary,

    Scott Thomas

    • Rev. Leslie Allen Stelter says:

      Dear Scott Thomas, I am Father Leslie Allen Stelter. I am 66 years old. I was born into a German family. I was a member of the Missouri Lutheran Church until age 23. My friend, Fr. Ronald Tangen helped me become a Roman Catholic when we were in the Air Force. I went to Rome Italy and was taught Thomism and Scolastic Philosopy and Theology at the Angelicum. I have a M.A. in Sacred Theology. I was taught by some of the greatest teachers in the Order of Preachers. I built a retirement home in Coloma Wisconsin. I am a missionary priest of the Thare-Nongseng Archdiocese in northeastern Thailand. I was ordained on June 9th, 1984 in Milwaukee by Most Rev. Lawrence Khai. I worked with the the Propagation of the Faith Society and did mission appeals for 26 years and never took a salary from the Archdiocese of Thare and paid for for the mission expenses so that every penny of the collections went to the Archdiocese of Thare to help the poor people. The reason why I did this is I practice True Devotion to Mary as taught by St. Louis De Montfort. When Archbishop Khai offered to give me a yearly salary of $1200 a year, (not a month), I asked him, instead, to give my salary to the Rector of our seminary so he could buy more food for the seminarians who has to fast 10 days every month because the funds for food always ran out before the 20th of every month. I told him that Jesus had said to a holy nun, “If you promise to spend all your time carrying for others, I promise you I will spend all my time caring for you!” I said to Archbishop Khai, “If Jesus can do this for a sister, he can do this also for a priest.” My Archbishop Khai told my friend, Miss Agnes J. Ryan, who got the “Lumen Christi” award, for my “golden mouth”, and in a letter to Bishop Fabian, Bishop of Lincoln, his friend, he said to Bishop Fabian in a letter to him that I was a treasure to the Archdiocese. I am totally 100% Pro-Life and abortion is an abominiable crime and is a problem of moral theology. Respecting every persons right to life is what motivates me and when the Church teaches as a dogma that ensoulment happens within a 10 day period, no sooner than 130 days after conception to no later than 140 days after conception, probably around 137-39 days after conception for most of us, as Blessed Catherine Emmerich also said, in her topic of “More about the Immaculate Conception” in Vol. I of her revelations printed by Tan books, not only will Roman Catholics have to agree on this to protect all the lives of the 7 billion plus people now living on earth, but also all Protestants, all Jews, all Moslems, all Buddahests, etc. Excuse my spelling mistakes. I make it clear, we must resolve the problem of when God creates the soul and puts it into the body now. If you want a copy of my letter, which I have been writing to the Pope now for the last 13 years, my email address is and you can send me a voice mail to 715-254-6287.
      That is a magic jack number and it sends me a voice message. You can give me your email address or mailing address and I can put a pdf document on a cd or dvd.. I wrote a 200 page letter to the Pope and I need someone who has contact with the Pope to help me to get it into his hands. I repeat, the moment of “upper brain birth” IS THE TIME OF ENSOULMENT ABOUT 139 DAYS AFTER CONCEPTION. THE TIME OF “UPPER BRAIN dEATH TELLS US THE TIME OF ENSOULMENT..

      tHANK YOU.


      In Jesus through Full of Grace, our Co-Redemptrix and our Spiritual Mother.

      Fr. Leslie Allen Stelter

      • Allen Dworakowski says:

        I will pray for your work and your commitment to Our Lord’s message. How I came upon your site is that I am trying to find contact information for Fr. Ronald Tangen. I listened to his message on prayer on Catholic Prayer MP3 and would like to ask him to do a mission at Our Lady Of Fatima parish in Aliquippa, PA. If you have any contact information on him I would greatly appreciate it.
        God Bless you

  11. Rev. Leslie Allen Stelter says:

    My creation day as an immortal person was 137 days before my birth day, July 9, 1946. God gave me my greatest right on my creation day, 137 days before i was born: my right to life. I also have an obligation to preserve my life using ordinary means. All human persons have the obligation to respect my greatest right. Therefore they must know during what time span they must do that. We all have to follow the same rules of argumentation and terms to all be in agreement about this. So, Pope Francis can guarantee my safety as a living person throughout my entire natural life span, the Holy Father must define as “of the faith” that ensoulment of the human body happens 139 days after conception and each of us as persons are in the wombs of our mothers for only 137 days in a normal pregnancy of 9 months or 276 days. This dogma is now necessary to ensure the safety and to protect all human persons in the womb and in the universe. My new address is Rev. Leslie Stelter, N556 1St Dr., Coloma, WI 54930-9048. I trust everyone will not be guilty of negligent misconduct and be of good character, and do the right thing, the will of God, by observing the word of God as they live as persons in this world. Fr. Les

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