I have a strong disagreements against St. Thomas Aquinas for three of his teachings

  1. Aquinas (and St. Agustine also) said that early gestation unborn babies are vegetable and animals before becoming human. Pro-abortion Catholic President Biden and Catholic Speaker Pelosi both quoted this in their defense of early legal abortion.

  2. Aquinas said that “conscience” must always be followed. This is absolutely contrary to Catholic teaching, but some people still cite this as justification for abortion.

  3. Aquinas said that lying is never permissible. Imagine the classic situation that you are hiding Jews in your attic during WW2 and the Nazis ask you if you are hiding Jews. According to Aquinas you must tell the Nazis “Yes they are in the attic” which results in the murder of the Jews.

Thank you.

Hi Cris 93,
I haven’t read Aquinas, but I would have to see, the quoted text, before I would believe that he said these things in the context you mentioned…


Hi Eugene,

In response to your request for verification of my three Aquinas positions I submit these reliable sources since I am not able to do so directly.

  1. Aquinas, in his main work, the Summa Theologica , states (Part I, question 118, article 2 ad 2)“…that the intellectual soul is created by God at the end of human generation”.[28]
    Although Jesus may have been exceptional, Aquinas did believe that the embryo first possessed a vegetative soul, later acquired sensitive (animal) soul, and after 40 days of development, God gave humans a rational soul.[29]

Ensoulment - Wikipedia

2.see well known A_Z quotes of Aquinas

  1. Therefore every lie is a sin, as also Augustine declares (Contra Mend. i).

SUMMA THEOLOGIAE: The vices opposed to truth, and first of lying (Secunda Secundae Partis, Q. 110) (newadvent.org)

I hope this satisfies your inquiry. May I hear back from you?

I expect that Aquinas’s views on prenatal development reflected the limited knowledge of the times. Also, he was a saint, but that doesn’t mean that everything he wrote was correct.

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Hi Literalman,

Aquinas ignored the Bible which says in the Psalms that King David had sin while in the womb and also there were Catholic Saints before Aquinas that published abortion was murder but Aquinas deliberately ignored both of these in favor of his own opinions.

I can only say that you should read Aeterni Patris by Leo XIII. It’s on the Vatican website. The encyclical is about the importance to the faith of Philosophy. His praise of St. Thomas begins in section 17.
The use of Thomas by people like Biden and Pelosi should have no bearing on judging him. Acceptance of his conclusions concerning ensoulment implies by necessity acceptance of his understanding of conception, which acceptance makes the named politicians’ arguments absurd. We know that conception immediately produces an independently living being because contemporary medical science has provided us with knowledge that was not available to St. Thomas. And, since it is Catholic doctrine (and Aquinas’ teaching) that the soul is the form of the body, there must be a body, which people of his time could not know for sure before it started kicking.
With respect to the authority of conscience, about which Thomas said a lot more that gives his conclusion context, I suggest the Catholic Catechism #1776 and following.
Was he wrong sometimes? Of course, he was a human being. Even Pope’s and Councils are wrong sometimes. Infallibility as a doctrine of the Church has very precise limits and exists only when those who possess the Magisterium clearly and unequivocally assert that authority.
I think that last statement about infallibility is correct, but, then, I’m a human being too.

@ jmj,

Thanks for the reply. Per your suggestion I did read AETERNI PATRIS . It was interesting but exaggerated. Obviously, Aquinas was a great theologian, but he was not without fault as no person is perfect.

Am I, little old nobody Chris, able to correctly criticize Aquinas? Well…let us see.

Aquinas said early gestation babies were vegetables (having a vegetable soul) and the animals (having an animal soul) and later in gestation a human soul. This is a historical fact of his own writing. He ignored two Bible verses that teach human ensoulment at conception…

Behold, I was shapen in iniquity; and in sin did my mother conceive me. Psalm 51:5 (original sin)

For as the body without the spirit is dead James 2:26 (humans are of only one spirit)

Plus I have quotes from 11 Church Fathers hundreds of years before Aquinas lived that taught the embryo is always a living human being, which Aquinas ignored. Biden and Pelosi are idiots but Aquinas gave them ammunition to say the idiotic things they say.

Secondly, Aquinas quote… “every judgment of conscience being right or wrong, is obligatory in such that he who violates conscience always sins” can never, never be true. It is as if to say that a pregnant woman believes in conscience that she should have an abortion then she must have the abortion or she sins. This is ludicrous per Pope John Paul II in Evangelium Vitae…

When conscience, this bright lamp of the soul (cf. Mt 6:22-23), calls “evil good and good evil” (Is 5:20), it is already on the path to the most alarming corruption and the darkest moral blindness. 24

No circumstance, no purpose, no law whatsoever can ever make licit an act which is intrinsically illicit, since it is contrary to the Law of God which is written in every human heart, knowable by reason itself, and proclaimed by the Church. 62

Your reference to CCC1776 is true enough but CCC 1800 is corrupted by Aquinas thinking to say the opposite of 1776…

1776 "Deep within his conscience man discovers a law which he has not laid upon himself but which he must obey. Its voice, ever calling him to love and to do what is good and to avoid evil, sounds in his heart at the right moment… For man has in his heart a law inscribed by God… His conscience is man’s most secret core and his sanctuary.

1800 A human being must always obey the certain judgment of his conscience.

Thanks for being patient with me this far. Please let me know what you think.


In the shorter Summa, he also taught against the Immaculate Conception, which would make him a heretic if he were alive today and didn’t recant his position. It is rumored that he changed his thinking on this prior to his death, but I haven’t seen anyone produce any hard evidence.

@ MDD2299
I agree that Aquinas was wrong on IC from what I have read of others who are experts on this topic.

Also I too have been mystified by the account of Aquinas last days. He reportedly told a friend “I adjure you by the living almighty God, and by the faith you have in our order, and by charity that you strictly promise me you will never reveal in my lifetime what I tell you. Everything that I have written seems like straw to me compared to those things that I have seen and have been revealed to me.”
This is a mystery to me.

With respect to the final quote from St. Thomas - that was made after he had had a revelation during mass in which God showed him some eternal truths. Of course he was wrong about the Immaculate Conception because Pius IX infallibly declared the dogma in the nineteenth century.
But there seems to be some misapprehension that I was suggesting that St. Thomas approved of abortion. There is no such indication in his writings. The Church and its saints have, from the beginning to the present day, condemned abortion.
The philosophical debate, which modern medical science has solved for us, was when the fetus became a body that could support a soul. The quote from James goes along with the comment I made about the soul as the form of the body. They simply didn’t know when that happened. God is free and can ensoul us when He pleases. The Church insists that we treat the fetus as ensouled at conception, but, so far as I know, it has never formally declared when that is. It seems to me - and this is purely my human reasoning - that too certain an assertion, without the Church’s proclamation, that the immortal soul is instantly there at conception risks the heresy condemned in the early Church that the soul is the product of sexual intercourse. Here are 2 propositions from St. Thomas that Rome, during the reign of St. Pius X, approved:
“Among the living bodies, the substantial form, called the soul, demands organic disposition, or heterogeneous parts, in order for there to be independently in the same subject a moving part and a part moved.”
“…the human soul subsists by itself. When it can be infused into a subject adequately disposed, it is created by God, and by its nature is incorruptible and immortal.”
Obedience to a certain conscience, whatever that conscience declares, is a firm proposition of Church morality. It is in the act of conscience that we are free agents responsible to God. If the conscience is mistaken because someone has not bothered to seek the truth, but, like Adam and Eve, decides the truth according to his or her own desires, then, of course, that person will have to answer to God. It is, after all, my act of conscience that leads me to look to the Church for the truth. Here is a quote from Sirach: “God in the beginning created human beings and made them subject to their own free choice.” (15:11 - New Amer. Bible - rev. ed.)
The interpretation of the quote from Psalm 51 is not certain. The Psalmist COULD have meant (and I’m not saying he did) that his mother had sinned when conceiving him. The only text the Church has declared as referring to Original Sin is Romans 5:12. That was at the Council of Trent.
I have to disagree about 2 things: ccc1800 does not contradict 1776, and Biden and Pelosi, unfortunately, are not idiots.
One other point: Obeying your conscience implies a command of conscience. Some use the expression when all they mean is, “I don’t see anything wrong with that.” Such people, it seems to me, fit into the following observation by Charles Dickens:
“Conscience is an elastic and very flexible article, which will bear a
deal of stretching and adapt itself to a great variety of circumstances.
some people by prudent management and leaving it off piece by piece
even contrive, in time, to dispense with it altogether.” (The Old
Curiosity Shop, Chapt. 6)
I hope that in the rush to deal with several issues, I have been coherent.

I know it was not formally defined until recent times. My point is that so much of the Western Church looks to Aquinas (and philosophy) as an authority. It seems problematic to me though that his approach to philosophy lead him to be on the wrong side of Dogma. If he was wrong about something so fundamental to the Faith that it would later be Dogmatically defined, then what else could he have been wrong about? Maybe it’s my Protestant upbringing, but I’ve always been suspicious of philosophy.

@ jmj

Aquinas having a revelation at Mass is “private revelation” which I do not believe.

My point about Aquinas is that such a so-called “brilliant” theologian should call unborn babies vegetables and animals is a black mark on his record. This black mark has nothing to do with his lack of medical knowledge rather it stems from following Aristotle and ignoring 11 Saints prior to him.

This is the definition of ensoulment/person according to the Pope…

”The soul is not a person, but the soul, joined to the body, is a person.” Pope Pius XII, Munificentissimus Deus, 32.

Obedience to a certain conscience has never been and will never be Catholic teaching because of 3 major, huge insurmountable exceptions to it:

  • Conscience is binding only when coming to God.
  • A person should never follow a “seared” (1 Tim 4:2) conscience.
  • Conscience can never be followed into intrinsic evil, AKA murder/abortion

Therefore CCC 1800 ‘A human being must always obey the certain judgment of his conscience.” Is horribly wrong and is another black mark on Aquinas.

CCC 1800 contradicts any other entry that may be true.

Additional edit: CCC1800 is not Catholic teaching because it is not in any Encyclical, nor any Magisterium document nor Sacred Tradition. You will notice that it has no footnotes, no references, no verification and no documentation because there isn’t any.

I confirm that the direct and voluntary killing of an innocent human being is always gravely immoral. EV 57
No circumstance, no purpose, no law whatsoever can ever make licit an act which is intrinsically illicit, since it is contrary to the Law of God which is written in every human heart, knowable by reason itself, and proclaimed by the Church. EV 62
The commandment “You shall not kill”, even in its more positive aspects of respecting, loving and promoting human life, is binding on every individual human being. EV 77

“When conscience, this bright lamp of the soul (cf. Mt 6:22-23), calls “evil good and good evil” (Is 5:20), it is already on the path to the most alarming corruption and the darkest moral blindness”. EV #24 (conscience can be corrupt and in the darkest moral blindness therefore is not to be obeyed)