Summarizing the Summas, or, the Simplicity of Saint Thomas Aquinas

Oct 8th, 2009 | By | Category: Blog Posts

The names “Thomas Aquinas” and “Summa,” when they spark recognition, can also produce rather visceral reactions. St. Thomas’ meticulous, dialectic method of exploring theological questions (the “scholastic” method) probably has something to do with the more than (and less than) intellectual reactions to the man and his works. Many folks find the scholastic method to be frustrating, while others find it distinctly illuminating. Aquinas’ preferred method of theological exposition, which is often considered to be dry and difficult, coupled with his immense influence on Catholic theology, gives him the not rare enough distinction of being both famous for his writings and rarely read or understood. In my opinion, when carefully read and rightly understood, Thomas Aquinas is a winsome and uncomplicated Christian thinker in his own right, and not an inexplicable of shibboleth of “manualist” or “traditionalist” or “anti-modernist” Catholicism. In what follows, I want to offer a glimpse of the simplicity of St. Thomas by way of some summary reflections upon the famous “Summas”, i.e., his Summa Theologiae and Summa contra Gentiles, which are his best known and most representative writings.

Thomas Aquinas is one of thirty-three Doctors of the Catholic Church. St. Thomas is further marked for distinction by Pope Leo XIII, who wrote that “he is rightly and deservedly esteemed the special bulwark and glory of the Catholic faith” (Aeterni Patris, 17). This recommendation notwithstanding, the Angelic Doctor has recently fallen upon hard times. Fergus Kerr’s sometimes snarky epitome, Twentieth-Century Catholic Theologians (Malden, MA: Blackwell, 2007), could have been appropriately subtitled “The Escape from Thomism.” It is surely no coincidence that the modern theologians’ marked departure from “the special bulwark and glory of the Catholic faith” has been accompanied by some significant slippage from that faith within the ranks of Catholic academia. This is of course most unfortunate, but I am not here concerned to chart or specifically respond to recent developments in Catholic theology. I will only note, autobiographically, that in times of real spiritual and intellectual need, St. Thomas has indeed proven to be a bulwark against confusion and unbelief, while his modern detractors have been of minimal service in this regard.

Still, I can understand why not everyone finds St. Thomas easy to appreciate. One can become befuddled by the very table of contents to the Summas, much more the dialectic attention to detail in the bodies of those works. This was certainly my experience as a Protestant. What in the world are these books about? They are not exactly arranged like Evangelical textbooks in systematic theology, nor do they read anything like Bible commentaries, or even the Church fathers. In short, if one is not over-burdened with background in medieval theology and philosophy, the Summas can be a bit much. If you, like me have been reared on Evangelical (or some form of contemporary existentialist) theology, the long sections and sub-sections on acts, habits, virtues, and vices might seem to constitute a dull, misplaced, and potentially disastrous slide from theology (especially soteriology) into ethics. It can seem like the only distinctively Christian doctrines come at the end of both works, and are there marred (at least in Protestant eyes) by sacramentalism. So, Thomas Aquinas seemingly suffers from the worst of two worlds: dry and academic on one hand, superstitious and sacerdotal on the other–a sad wedding of philosophy and priestcraft.

Well, things are not as bad or as complicated or as hodgepodge as they might appear. Here is the content of the Summas, in a nutshell, which highlights the fundamental simplicity of St. Thomas:

1. God exists.
2. Human beings want to be happy.
3. These two facts are intimately related.

Herein lies a clue to the seemingly disproportionate space spent on human psychology (in an older sense of the word, which includes ethics and what we call “epistemology”) in the Summas. Thomas is not particularly concerned with abstractions. He is concerned with real and practical things. Few realities are as practical to us humans as the facts that there are such things as human beings and these desire happiness. Aquinas, like everybody else, knows that people want to be happy. But he also wants to know:

1. Why is there such a thing as man, who desires happiness?
2. What sort of thing is man, and in what does his happiness consist?
3. What hope is there for man to find happiness?

The first question leads St. Thomas to consider the existence, nature, and acts of God. The second question leads him to consider human psychology. The third question leads him to Christ, who is fully God and fully human. Both Summas cover roughly the same ground: God, creation, angels, man, law and grace, Incarnation, sacraments, last things. The main difference between them is that the Summa Theologiae was written for beginners (!) in the study of theology (see the prologue) while the Summa contra Gentiles is a sort of apologetics manual with an emphasis on religious epistemology. (Perusing the outlines provided below, you will notice that the Summa Theologiae features more analysis of habits, virtues (both cardinal and theological) and vices than does the Summa contra Gentiles. The latter work has more of an eschatological emphasis, focusing on final causality and the Beatific Vision.)

You might wonder, as I have, why there are no major sections in the Summas dedicated to Scripture (“bibliology”) and the Church (“ecclesiology”). But this is easily understandable when we consider that, for St. Thomas, the Church, with her Sacred Scripture and Holy Tradition, is not primarily an object of speculation. Rather, divine revelation as interpreted by the Catholic Church is the lens by which St. Thomas sees. Aquinas is the most dogmatic of theologians operating in the simplest faith. This can be appreciated by perusing his unblushing appeals to authority by way of providing premises for his own arguments. But Aquinas is not simple-minded. His mental make-up prompts him to ask fundamental questions in a most thorough way. That is to say, St. Thomas was a philosopher as well as a theologian.

Most people are not philosophers. Many theologians are not philosophers. Some of these have not had the opportunity to become so, others are not so made. But some people are philosophers, by nature and training, and this is just to say that they think about fundamental things in a particularly thorough way. By “thorough” I do not mean “pagan” or “unbiblical” or “unbuttered toast.” I mean thorough, and that is perfectly compatible with Christianity and the Bible and breakfast foods. St. Thomas is thorough in his consideration of things. That makes him kind of difficult for many of us, which is our problem, not his. This problem is susceptible of a simple, though time-consuming, solution: Tolle, lege.

Not everyone is called to study Aquinas, nor is anyone required to be a Thomist. But those who want to understand him can begin by reading his stuff. The Summa Theologiae and the Summa contra Gentiles are the best places to start. Both works are available online in English translation (links below). And the best way to start starting to read the Summas is by having some idea of what you are getting into. Among many fine introductory works, I particularly appreciate this book, which is heavy with primary texts and explanatory footnotes. G.K. Chesterton’s biography of St. Thomas, like anything written by Chesterton, is also worthwhile, and very accessible (both materially, as being available for free online, and intellectually, as being written on a popular level).

St. Thomas was a Christian theologian and a mystic, which is really (traditionally) pretty much saying the same thing. People sometimes oppose Aquinas’ published works to his famous mystical visions, but these are not really at odds. The visions are simply greater than the writings, as the Beatific Vision is greater than theological accounts of the Beatific Vision. May we all, with St. Thomas, be granted that Vision. In the meantime, we have access to the written works (and the prayers) of this particular Saint, which are so highly recommended by the Catholic Church.


The Summa Theologica is comprised of three main parts, the second being subdivided into two parts and a supplement being appended to the third part.

First Part  (QQ. 1–119)

Sacred Doctrine  (1)

God  (2–43)

God’s Existence (2)
God’s Perfections (3–26)
Trinity (27–43)

Creation  (44–102)

Angels  (50–64)
Six Days  (65–74)
Man  (75–102)

Divine Government  (103–119)

Effects in Creation  (103–106)
Angelic Order  (107–114)
Corporeal Creatures / Man  (115-119)
First Part of the Second Part  (QQ. 1–114)

Human Acts  (1–48)

Happiness (1–5)
Voluntary and Involuntary Acts (6–48)

Habits  (49–89)

Habits (49–54)
Virtues (55–67)
Gifts (68–70)
Vices (71–89)

Law  (90–108)

Kinds of Law (90–97)
Old Law (98–105)
New Law (106–108)

Grace  (109–114)

Necessity  (109)
Nature, Cause, Effects  (110–113)
Merit  (114)
Second Part of the Second Part  (QQ. 1–189)

Theological Virtues  (1–46)

Faith (1–16)
Hope (17–22)
Charity (23–46)

Cardinal Virtues  (47–170)

Prudence (47–56)
Justice (57–122)
Fortitude (123–140)
Temperance (141–170)

Peculiar Gifts and States of Life  (171–189)

Gratuitous Graces (171–178)
Active and Contemplative Life (179–182)
Various States of Life (183–189)
Third Part  (QQ. 1–90)

Incarnation  (1–59)

Fitness (1)
Mode of Union (2–26)
Blessed Virgin (27–30)
Conception (31–34)
Life (35–45)
Passion (46–52)
Resurrection (53–56)
Ascension (57–59)

Sacraments  (60–90)

General (60–65)
Baptism (66–71)
Confirmation (72)
Eucharist (73–83)
Penance (84–90)
Supplement to the Third Part  (QQ. 1–99)

Sacraments, cont.  (1–68)

Penance, cont. (1–28)
Unction (29–33)
Order (34–40)
Matrimony (41–68)

Last Things  (69–99)

Intermediate State (69–74)
Resurrection (75–87)
Judgment (88–90)
Heaven and Hell (91–99)

The Summa contra Gentiles is divided into four books, the third book being subdivided into two parts.

Book One: God  (Ch. 1–102)

Faith and Reason  (1–12)
Existence of God (13)
Properties of God (14–102)

Book Two: Creation  (Ch. 1–101)

God and Creation (1–45)
Intellectual Substance (46–55)
Intellectual Substance and Body (56–90)
Separate Substances (91–101)

Book Three: Providence  (Ch. 1–83)

God the End of All  (1–63)

Final Causality (1)
Teleology and Act (2–3)
Evil and Act (4–15)
God and Act (16–25)
Human Happiness (26–44)
Knowledge of Separate Substances (45–50)
The Beatific Vision (51–63)

God the Governor of All  (64–163)

Divine Providence (64–76)
Providence and Secondary Causes (77–82)
Hierarchy of Causes (83)

Book Three: Providence  (Ch. 84–163)

Causal Relations and Human Acts (84–113)
God’s Law and Human Ends (114–146)
God’s Grace and Human Happiness (147–163)

Book Four: Salvation  (Ch. 1–97)

Divine Revelation and Human Happiness (1)
Divine Generation (2–14)
Holy Spirit (15–25)
Trinity (26)
Incarnation (27–55)
Sacraments (56–78)
Last Things and Human Ends (79–97)


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  1. I would definitely check out a couple of works by Fr. Brian Davies (a Dominican Priest at Fordham University in the Philosophy Dept.):

    The Thought of Thomas Aquinas

    Aquinas (Continuum Compact)

    Of course, if you’re in NYC, sitting in on one of his classes is an absolutely enlightening experience.

  2. As someone who has not been formally trained in philosophy but finds herself married to a philosopher, I have found the writings of Walter Farrell,O.P. to be extremely helpful. The first link below is a wonderful work that is almost devotional in nature and is very easy to read and understand. The second link is Fr. Farrells’s 4 volume summary that is now completely online for download.

  3. I should clarify that I am also not very computer savvy :)

    Here are the links:

    My Way of Life: The Summa Simplified for Everyone

    A Companion to the Summa

  4. Sean,

    Thanks for the links.

    Of course, if you’re in NYC, sitting in on one of his classes is an absolutely enlightening experience.

    I take it that you are so situated?

  5. Carol,

    Thanks for the references. I will look at Farrell. You mentioned a couple of links, but I do not see them.

  6. Ah, they were sitting on the dashboard waiting for approval. Any comment with links has to be specifically approved by an administrator, I think. Thank you.

    I took the liberty, as with Sean’s links, to change the text of the web address into the title of the work referenced, while maintaining the exact links that you both submitted. This makes it easier for folks to see what they are linking to. Hope that you don’t mind.

  7. Dear Andrew,

    Thanks for this great post! When you mentioned Aquinas’ ecclesiastical views, I remembered his CONTRA ERRORES GRAECORUM (Against the errors of the greeks). In chapters 33 through 38 of that work, Aquinas discusses his views on the nature of the papacy (jurisdiction, necessity of being subject to the papacy for salvation, etc). Another source for his views on the papacy would be his actions in response to various papal requests.

    Here’s the link to his “Against the errors of the greeks”:

    I’ve heard that Presbyterians sometimes view Aquinas as a Calvinist before Calvin. Surely they are referring to interpretations of some his theological views about predestination, not of his views on Church authority, right? In light of Aquinas’ seemingly clear views on the papacy, I would assume so at least. Does anyone know what the Presbyterians do with his non-Presbyterian ecclesiology?


    K. Doran

  8. K. Doran,

    Thanks. Thanks especially for the link. I have always wanted to read that particular work.

    Sometime in the 1990s, the late John Gerstner wrote an article in the Westminster Theological Journal to the effect that “Thomas Aquinas was a Protestant.” I do not think that many people bought into the notion. A follow-up piece, citing much evidence to the contrary, was published (I cannot remember the author’s name) in a subsequent issue of WTJ.

    I attended a “Thomistic” Evangelical Seminary. We ignored St. Thomas’s ecclesiology. There was an occasional shake of the head over his occasional outburst of unmistakable papistry. But, we supposed, he was in this respect a product of his times. Where else could he have gone to church?

    Does anyone know what the Presbyterians do with his non-Presbyterian ecclesiology?

    Book Four of Calvin’s Institutes gives some answer to the question. To be sure, it seems that Calvin usually had St. Thomas in mind when wrote (in other connections) of the “more sober” among the sophists. Gerstner was of the opinion that St. Thomas, had he been around in the 16th century, would have put his oar in with the Protestants and shoved off from the Barque. If so, I wonder why he did not take up the cause when he was on point?

    As to predestination, providence, Calvinism and Thomism: I can recommend some stuff ready to hand, here and here.

  9. If anyone knows of some particularly good works on either Summa, or Thomism in general, please feel free to pipe up in the combox.

    In the Thomism in general category, I can recommend these books:

    The Aquinas Catechism: A Simple Explanation of the Catholic Faith by the Church’s Greatest Theologian
    by Thomas Aquinas

    Sophia Institute Press, Manchester, New Hampshire, USA

    ISBN-10: 1928832105
    ISBN-13: 978-1928832102

    The retail list price for this book is $17.95 – a good deal at the list price, and available through internet booksellers at a discount.

    Amazon lists 22 books by Etienne Gilson, several specially dealing with Thomism. I have found this book helpful:

    Elements of Christian Philosophy
    “A master philosopher and historian illuminates the key ideas which form the foundation of the theology of St. Thomas Aquinas” by Etienne Henry Gilson, Member of the Pontifical Academy of St. Thomas Aquinas

    This is the editorial review from

    “[A] textbook in Thomistic metaphysics… It was prepared for those who read St. Thomas on theological topics without having had training in his metaphysical distinctions. It follows the sequence of the Summa in taking up these `elements’: the nature of Christian doctrine (philosophy and theology), God, the transcendentals, causation, and man (knowledge, will and society. – Christian Century

    Admittedly, the Angelic Doctor has fallen upon hard times. You would have to cast a wide net to catch a Thomist in a modern Catholic university.

    This two volume work is available from TAN Books and Publishers, Rockford Illinois:

    The Three Ages of the Interior Life, Prelude of the Eternal Life, by Fr. Reginald Garrigou-Lagrange O. P (The summary of a course in ascetical and mystical theology given for over twenty years at the Angelicum in Rome.

    From the flyleaf: “Fr. Reginald Marie Garrigou-Lagrange, O. P (1877-1964) was one of the great Catholic Theologians of the 20th century and during his life was undoubtably the greatest living Dominican theologian. … A thoroughgoing Thomist in the classic Dominican tradition, Fr. Reginald Garrigou-Lagrange had both a deep appreciation for the enduring vitality of St. Thomas Aquinas’s work and a real understanding of the spiritual needs of his own time. Having steeped himself in Thomistic principles, he thought through virtually ever aspect of the Faith in light of these principles, producing over 500 books and articles …

    The entire content of The Three Ages of the Interior Life, Prelude of the Eternal Life can be found online here:

    The above is linked to this website:

    The Summa and other matters … dedicated to the legacy of St. Thomas Aquinas

    This site is dedicated to the teaching of St Thomas Aquinas. In particular, the site aims to offer online the commentaries on the Summa written by Pere Reginald Garrigou-Lagrange, O.P.

  10. It’s out of print and hard to find, but I’ve seen some excellent Thomists recommend Sertillanges, “Foundations of Thomistic Philosophy.” I just started reading it in our “Catholic Philosophy Group.” (And if any Catholic is interested in learning more about Thomism, you can let us know if you want to be part of that group.)

  11. Tim,

    Good call. This gives me the chance to make it clear that by recommending a theologically-oriented introduction to the Summas I was not denying the importance of understanding where Thomas is coming from philosophically. This is essential for profitable reading of the Summas.

    Oh and a re-shout out to K. Doran for the Contra Errores Graecorum link. It led me to the site with the most extensive online library of Aquinas’ works in English translation [yes!] that I have yet found:

    Thomas Aquinas’ Works in English

    A huge thank you to Joseph Kenny, O.P., for making these writings available in electronic format (in some cases he has even supplied translations for parts of a work).

  12. Hello mateo.

    Thanks for the references. According to Fegus Kerr (Twentieth-Century Catholic Theologians), the regime of Garrigou-Lagrange had a lot to do with putting modern Catholics off their St. Thomas. His notion of intellectual formation for seminarians at one time ruled supreme, and things were rather too high and dry for a lot of young intellectuals in an evolutionary age; eventually, historicism and existentialism beat out Thomism. By “Thomism,” I mean moderate realism, which is a living philosophy, not a dead letter. Too often, apparently, Thomism was presented according to the letter–something to be learned by rote.

    Here are some more links to Garrigou-Lagrange’s theological works, including a commentary on the Summa Theologica:

    Select Works of Reginald Garrigou-Lagrange

    Prominent among the highly readable, though quite challenging, Thomists of the Twentieth-Century stand Etienne Gilson and Jacques Maritain. These men were Thomists in the best sense, knowing that it is living philosophy. Gilson’s brand of “existential” Thomism has been particularly formative in my own (still very undeveloped) intellectual life. Three of his philosophical works on the history of philosophy stand out in my mind. Here they are in ascending order of difficulty:

    God and Philosophy

    The Unity of Philosophical Experience

    Being and Some Philosophers

    Each book tackles the question of why philosophers have tended to botch, and then give up (and then return to) metaphysics. The difficulty comes down to a category mistake. Gilson argues that the first thing in reality, even more primary than being (that which is), is fundamentally an act of existence (that act which makes something real, as opposed to merely ideal) and cannot be conceptualized. Existence is not a property among other properties. It lies altogether beyond our intellectual capacity in that sense. Kant recognized this and gave metaphysics the boot. Gilson recognized this and and stated that metaphysics depends upon our ability to affirm the act of existence, not through conceptualization, but by means of an intellectual judgment. In theology proper, this distinction is expressed thusly: We cannot say what God is (e.g., God is x), but we can say that God is. Our acts of predication concerning God (e.g., God is infinite) are fundamentally concerned to state what God is not (e.g., circumscribed). This does not, however, render God-talk equivocal. In affirming that God is (in fact, in knowing that anything is) the intellect is aware of (even if in an inchoate way) something that it cannot comprehend or conceptualize: an unlimited act of existence.

  13. Andrew Preslar:

    …the regime of Garrigou-Lagrange had a lot to do with putting modern Catholics off their St. Thomas. His notion of intellectual formation for seminarians at one time ruled supreme, and things were rather too high and dry for a lot of young intellectuals …

    This is from Wikipedia’s article on Fr. Reginald Marie Garrigou-Lagrange, O.P.:

    He taught many eminent Catholic theologians during his academic career, the most illustrious being the future Pope John Paul II. … Comment on an early draft of Karol Wojtyla’s (later Pope John Paul II) thesis, of which Fr. Garrigou-Lagrange was the director: “Writes much; says little.”[citation needed]

    That snarky comment from Wikipedia reminds me of this scene from Amadeus:

    Emperor Joseph II: My dear young man, don’t take it too hard. Your work is ingenious. It’s quality work. And there are simply too many notes, that’s all. Just cut a few and it will be perfect.

    Mozart: Which few did you have in mind, Majesty?

    John Janaro writes in his brief biography of Father William G. Most that Fr. Most wrestled with the writings of Garrigou-Lagrange on the issue of grace and predestination :

    … Fr. Most confronted his most difficult and troubling challenge, a disturbance that touched the very heart of his presentation of the faith. He had been studying the treatises of the great theological schools, and was reflecting on their presentations of the mystery of grace and predestination. One day in 1952, he was reading a commentary on St. Thomas Aquinas by the great Dominican Reginald Garrigou-Lagrange. The style was fluid and convincing, the thought logical and penetrating, but its implication was distressing. Pere Garrigou-Lagrange’s explanation of divine providence, in its attempt to be philosophically consistent, seemed to say that God reprobates and elects “blindly”-that is, He saves or damns without any concern for the individual soul. How then can it be said that God, who cannot change or be moved by anything, really cares about each and every man, and if He does, how is it that any are eternally lost? Does not God “will that all men be saved and come to the knowledge of the truth” (1 Tm. 2:4)?

    FR. WILLIAM G. MOST by John Janaro ( )

    I am hoping that someone at CTC will write a “lead article” (or series of articles) on the topic of predestination. Personally, I would like to see the theses of Fr. Garrigou-Lagrange’s book Predestination and Fr. William G. Most’s book Grace Predestination & Salvific Will God: New Answers To Old Questions compared to Calvin’s ideas about predestination.

    As long as I am making a wish list of articles from CTC, I would also like to see a “blog entry article” that comments on this article by Fr. Most about the “Thomism” of Garrigou-Lagrange on the issue of predestination:

    by Fr. William G. Most

    … we ask: Was St. Thomas a Thomist? Our answer is no for two reasons.

    FIRST REASON: St. Thomas follows excellent theological method. In approaching the problem of predestination, he looked for more than one starting point, and seemed to have found two. …

    Andrew Preslar:

    …Gilson argues that the first thing in reality, even more primary than being (that which is), is fundamentally an act of existence (that act which makes something real, as opposed to merely ideal) and cannot be conceptualized. Existence is not a property among other properties. It lies altogether beyond our intellectual capacity in that sense. Kant recognized this and gave metaphysics the boot. Gilson recognized this and stated that metaphysics depends upon our ability to affirm the act of existence, not through conceptualization, but by means of an intellectual judgment.…

    It seems to me that you must understand and appreciate Etienne Gilson’s book Thomas Realism & the Critique of Knowledge. I bought that book, but soon realized that I was floundering in deep waters. Perhaps someday you can write a blog entry article commenting on the topic that you have raised here. I really appreciate the ability of the writers at CTC to bring these kinds of topics down to earth.

    God bless CTC and their good work!

  14. Hello mateo.

    Never read that book. Gilson was a marvel. A couple ‘a posts on predestination would seem appropriate at some point, no? Some of the scheduled articles will deal with the topic. It is very difficult, and I hope not to be the one to give it a go. We have trained philosophers here (praise God). They can have it.

  15. Andrew,

    Thanks for the response. I used to be so situated. I’m doing my PhD at Fordham (now on the dissertation end and living in Chicago), so I was fortunate to be able to take an Anselm and Aquinas course from Fr. Davies and sit in on his Intro to Aquinas course.

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