St. Thomas Aquinas & the Culture of Life

Upon this 45th annual March for Life, I read a line of attack against the Church’s pro-life stance that I had not heard before now. Some pro-choice advocates use the Church’s greatest theologian, St. Thomas Aquinas, to argue in favor of abortion. Nicholas Kristof did it in a May 2017 N.Y. Times column about Dr. Willie Parker, an oxymoronically called “Christian Abortion Provider.” Mr. Kristof falsely claimed that St. Thomas Aquinas “believed that abortion was murder only after God imbued fetuses with a soul, at 40 days or more after conception.” Moreover, Aquinas even made it into the Supreme Court’s landmark Roe v. Wade decision, citing “the 40-80 day view, and perhaps to Aquinas’ definition of movement.”

What they are both referring to is the mistaken notion that the unborn baby receives its soul (“ensoulment”) 40-80 days after conception depending upon gender. In the pre-scientific mind, this was generally thought to be recognized in the baby’s movements, or “the quickening” around 20 weeks after conception.  Aquinas’ apparent false opinion was based upon the primitive science of his day (13th century), which was notably still rooted in the ancient writings (4th century B.C.) of Aristotle.

St. Thomas actually never wrote anything explicitly on abortion. So, to say that he approved of abortion is utterly false. In fact, he did condemn it implicitly in his magnum opus, Summa Theologica. For example, in his commentary on murder, he states: “He that strikes a woman with child does something unlawful: wherefore if there results the death either of the woman or of the animated fetus, he will not be excused from homicide.” (ST II-II, q.64, a.8)  In another section he addresses various scenarios of whether to baptize a baby in the mother’s womb, saying: “If, however, the mother die while the child lives yet in her womb, she should be opened that the child may be baptized.” (ST, III, q.68, a.11)

St. Thomas’ underlying philosophy is correct: to kill an unborn baby is murder. He ran into some ambiguity with his era’s limited understanding of embryology. It is very clear that if St. Thomas had lived in the modern scientific age of biology, genetics and sonograms he would have concluded beyond a doubt that life begins at conception. Natural science clearly demonstrates the existence of a new genetic individual at fertilization. He was, in this respect, a victim of his time.

Nevertheless, St. Thomas did touch on this indirectly again in the third part of Summa Theologica while discussing the Immaculate Conception of Mary. He certainly argued that the human soul is present by the time of the quickening.  On the other hand, he did not think philosophy itself could say definitively whether or not the soul is present before any observable body movements in the fetus.  To reiterate, he did not say the soul was definitely not there, only that he could not prove it was there.  In the case of the Virgin Mary’s Immaculate Conception, he argued that we do not know exactly when she was sanctified (i.e., received her soul), so the Church correctly celebrates her sanctification from the time of conception. (ST, III, q. 27, a.2, ad.3)  We can infer through his conclusion that he considered ensoulment possible from the moment of conception, and thus, making any abortion tantamount to murder.

The idea of “delayed ensoulment” is a red herring, however.  The Church has always taught that abortion is intrinsically evil, and is not dependent upon the idea of ensoulment.  The Church’s position is built upon Scripture, Tradition, and natural law, which St. Thomas surely knew and accepted.  The prophet Jeremiah wrote, “Before I formed you in the womb I knew you, and before you were born I consecrated you.” (Jer. 1:5) The prophet Isaiah similarly wrote, “Thus says the Lord, your Redeemer, who formed you from the womb.” (Is. 44:24)  The Didache, a vade mecum written sometime near the end of the first century states, “Thou shalt not murder a child by abortion.” Abortion is similarly condemned throughout the writings of the Apostolic Fathers, from Clement to St. Jerome, and so many more.  St. Basil the Great wrote in the fourth century that those who have “deliberately destroyed a fetus has to pay the penalty of murder.” St. Thomas knew extraordinarily well all of these ancient Church teachings on abortion, and that it was forbidden at any stage of development.

The Catechism too is clear on this: “Since the first century the Church has affirmed the moral evil of every procured abortion. This teaching has not changed and remains unchangeable.  Direct abortion . . . is gravely contrary to the moral law.” (CCC 2271)  St. Pope John Paul discussed ensoulment too as a red herring in Evangelium Vitae: “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.” (EV, 61) In our era today, with the force of modern scientific evidence of D.N.A. analysis and 3D ultrasounds, we can understand without question a person is a person from the moment of conception.

This is why in light of modern science the permissive acceptance of abortion is so scandalously pernicious. This callous perniciousness of the culture of death is crystallized in the fascinating case of Dr. Stojan Adasevic. Dr. Adasevic was an infamous Serbian doctor who performed abortions in the communist country of Yugoslavia for a couple of decades, killing in utero somewhere between 48,000 to 62,000 babies. His abortion mill even killed up to 35 babies in one day.

That all changed one night when he began to have a profound reoccurring dream that haunted him for weeks and weeks on end. In the dream he was in a beautiful sunlit meadow full of flowers with many children playing and laughing. All of the children were from four to 24 years of age. Whenever he would try to approach and speak to the children they would run away screaming in terror. Despite the idyllic setting of the dream, he felt oppressed and would wake up in a cold sweat each night. The recurring scene was watched over by a figure in a black and white habit who would stare silently at him.

Eventually one night, he was able to catch one of the children, and the child cried out in terror: “Help! Murderer!” At that moment, the man in the black and white habit turned into an eagle and swept down to pull the child away.  The next night the doctor decided to ask the man who he was. The man replied, “My name is Thomas Aquinas.”  Stojan then asked, “Who are these children?” St. Thomas answered, “These are the ones you killed with your abortions.” With that, Stojan woke up in shock, refusing to participate in any more abortions. There were many other details involved revealing this as something more than just a dream. Since that time, Dr. Adasevic became heavily involved in the pro-life movement and reverted back to the Orthodox faith of his childhood. Stojan has since apparently had a great devotion to St. Thomas Aquinas. He wonders now, having read the Summa Theologica and St. Thomas’ ambiguous writing on Aristotle’s idea of ensoulment, if “the saint wanted to make amends for that error.”

Whether or not that was, in fact, one of St. Thomas’ errors remains debatable.  Clearly, he thought ensoulment was possible from the moment of conception, but he left some ambiguity in regards to the provability of that belief.  Unfortunately, the primitive “science” of St. Thomas’ day could not establish that as empirical fact.  Yet, he unquestionably followed the Church’s teaching on the evils of abortion, so that those who use him to promote the culture of death are wrong.  We can infer that St. Thomas, the Angelic Doctor, was unwaveringly pro-life, condemning abortion as murder.  And, if he were alive today, St. Thomas would clearly stand with those who accept modern science that life begins at conception.

image: Andreas F. Borchert [CC BY-SA 3.0 de, CC BY-SA 4.0-3.0-2.5-2.0-1.0 or GFDL], via Wikimedia Commons

Brian Kranick


Brian Kranick is a freelance writer focusing on all things Catholic. In addition to other studies, he has a master's degree in Systematic Theology from Christendom College.  He has spent years working as an analyst in the Intelligence Community, and currently resides with his wife and three children in the Pacific Northwest.  He is the author of the blog:

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  • LentiFruvous

    The bizarre thing (in my view) about these sorts of arguments is that they always center around whether or not St. Thomas would have considered an unborn child to be human before quickening. On an Aristotelian biology, it makes sense that before the mother could feel movement the child wouldn’t be considered human, because the infusion of the soul granted the power of movement. However, we know Aristotle was wrong about this now. Aquinas, however (even on Aristotelian biology), still would have considered any act that interfered with the normal progression of pregnancy to be an act of contraception and still wrong (see Summa Contra Gentiles Book 3, 122). It is thus stupid to say that Aquinas would have been “pro-choice” even if Aristotelian biology were true.

  • Vernon Chism

    abortion is murder the bible says we shall not kill


    I am a 100% pro-life Roman Catholic priest. The two ideas of ensoulment at conception(Catholic idea) or ensoulment at birth(Jewish idea) are both equally dangerous to all human persons after their Creation day, which is about 137 days before natural birth in a full term pregnancy. St. Thomas said the soul exits the body because the body loses the natural disposition to remain united to the soul. Death, the separation of the soul from the body) tells us the time in pregnancy ensoulment happens. Where is this natural disposition in the body? It is in the “upper brain,” from which the intellect of the soul receives a “sense image” so the intellect can know the truth about a thing. The danger of the idea of ensoulment at conception lies in the fact that conception happens 125-139 days before “upper brain” birth. So, this heretical idea says the “upper brain” has nothing to do which keeping body and soul together during a person’s life. This means that it is not the whole that can’t be sacrficed, and it is only a part that can be sacrficed, like a leg, kidney, heart, lung, etc. to save a person’s life. However, since the natural disposition of the body to have the soul is in the “upper brain” only, removing it would cause the separation of the person’s soul from his or her body, even if the other body organs are still in tact and alive. The Jewish idea of ensoulment at birth is just as dangerous, because it holds that ensoulment happens 137 days after the time of “upper brain” birth. For moral persons to follow the rule correctly that the part can be sacrificed in order to save the whole, so a person can go on living and not die, the “upper brain” should be known by all as the “whole” and everything outside the “upper brain”, including the brain stem, or even the “middle brain”, are the parts of the body that can be removed and even replaced with something mechanical or electronic. Not only that, if the Holy Father teaches the dogma of a person’s creation day to be in the 5th month of pregnancy, we can save all of those persons in the womb from the first moment of their existence so they can all develop good bodies and have their own birthdays. This dogma will save all of their lives. This is the best reason why we need this dogma now. The Blessed Virgin Mary’s pregnancy was only 137 days or only 4 1/2 months long. All of us in a normal full term pregnancy were in the womb of our respective mothers for the same length of time. The Catholic liturgy needs to be changed so Christmas is celebrated on the liturgical calendar 137 days after the celebration of the Feast of the Annunciation. Furthermore, the Solemnity of the Immaculate Conception has to be moved so it is 137 days before the celebration of the birth of Mary. The celebration of the birth of St. John the Baptist has to be moved so it is about 2-3 weeks before the celebration of Jesus’ birth. All the wrong idea’s about ensoulment are dangerous and can’t be tolerated because the have to deny where the real natural disposition of the human body is for the soul to animate it. It is not in the DNA at conception. It is not in the human breathe of a new born baby, that has started to breathe on it’s own. That is why the baby quickens because “upper brain” birth has happened. Thank you. Fr. Leslie Allen Stelter. Also, Full of Grace, the Virgin Bride of Our Lord Jesus Christ, is our Blessed Mother because she became the Bride of Jesus at the Last Supper when He gave her, not one of his ribs, as did Adam for Eve, but he gave his entire body and soul to her in Holy Communion and espoused her in the order of grace, by the power of this Holy Sacrament of the Altar, so that, being one with Jesus, as Jesus became our Redeemer, she became our Co-Redemptric, so that Jesus, her Bridegroom at the Last Supper, could say to her from His cross, “Woman, (Gen. 3:15), behold your son! and Jesus could say to St. John, “Son, behold your mother.! The name of our Blessed Mother is not Mary, but it is “Full of Grace.” This name was given to her by the Holy Trinity, (see Is. 61:1-5) AT THE TIME OF THE ANNUNCIATION! My email address is and my address is N556 1st Drive, Coloma, WI 54930-9048. God bless you. Fr. Leslie Allen Stelter