What is Thomism? The Twenty-Four Thomistic Theses

“If they deviated so much as a step, in metaphysics especially, from Aquinas, they exposed themselves to grave risk.”

St Thomas Aquinas

St Thomas, Universal Doctor – Fr Edward Leen CSSP
The Holy Wrath of St Thomas Aquinas – G.K. Chesterton
On the Five Qualities of Prayer – St Thomas Aquinas
True Law – According to the Teaching of St Thomas Aquinas
What is Thomism? The Twenty-Four Thomistic Theses

St Thomas Aquinas and the Church – His Intrinsic Authority
St Thomas Aquinas and the Church – His Extrinsic Authority

The “Angelic Warfare Confraternity” of the Cord of St Thomas – Translation of an 1863 pamphlet
“The Angelic Warfare Confraternity” – Robinson OP, 1941

The Fioretti of St Thomas:
Part I: His Life
Part II: His Death
Part III: The Miracles after his Death

Image: Pope St Pius X, Wiki Commons.

In his classic encyclical against modernism, Pascendi Dominici Gregis, St Pius X wrote:

“We will and ordain that scholastic philosophy be made the basis of the sacred sciences.”[1]

But what is meant here by “scholastic philosophy”? Fr Pedro Lumbreras OP, in an article from 1923, wrote the following:

“Scholastic philosophy, however, is a very large name. For there were many who strove in the Middle Ages for the establishment of a rational philosophy in conformity with dogma and with a view of affording assistance to the theological studies. Since then we have had several systems of philosophy among the schoolmen. And each system has its opinions. And these opinions are never uniform, often contradictory.

“When the Pope, therefore, decrees the teaching of Scholastic Philosophy, does he mean indifferently any of those systems of philosophy? Are all the scholastic teachings, in the mind of the Pope, on an equal basis in this regard?

“Certainly not. For there is one schoolman specially mentioned in the pontifical documents; and there is a system of scholastic philosophy, which is individually praised, and praised with special recommendation by the Roman Pontiffs.”[2]

And who is this one schoolman mentioned, and what is this one system of philosophy praised and recommended by the popes? The schoolman is St Thomas Aquinas, as St Pius X himself tells us:

“Let it be clearly understood above all things that the scholastic philosophy We prescribe is that which the Angelic Doctor has bequeathed to us.”[3]

But what of the school? As Lumbreras notes, “St Thomas did not write a textbook on philosophy, neither did he draw up a list of the fundamental principles of his philosophy.”[4]

This gave rise to problems. St Pius X writes:

“Now because the word we used in the text of that letter recommending the philosophy of Aquinas was ‘particularly,’ and not ‘exclusively,’ certain persons persuaded themselves that they were acting in conformity to our will or at any rate not actively opposing it, in adopting indiscriminately and adhering to the philosophical opinions of any other Doctor of the School, even though such opinions were contrary to the principles of St. Thomas. They were greatly deceived.

“In recommending St. Thomas to our subjects as supreme guide in the Scholastic philosophy, it goes without saying that our intention was to be understood as referring above all to those principles upon which that philosophy is based as its foundation.”[5]

St Pius X concludes:

“We therefore desired that all teachers of philosophy and sacred theology should be warned that if they deviated so much as a step, in metaphysics especially, from Aquinas, they exposed themselves to grave risk. –We now go further and solemnly declare that those who in their interpretations misrepresent or affect to despise the principles and major theses of his philosophy are not only not following St. Thomas but are even far astray from the saintly Doctor.

“If the doctrine of any writer or Saint has ever been approved by Us or Our Predecessors with such singular commendation and in such a way that to the commendation were added an invitation and order to propagate and defend it, it may easily be understood that it was commended to the extent that it agreed with the principles of Aquinas or was in no way opposed to them.”[6]

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But even once St Thomas is accepted as the authority on which a system is based, the term “Thomism”, can mean different things in different contexts. Lumbreras writes:

“[W]e have many philosophical books, which claim to reflect the mind of St. Thomas, though they contain opinions contrary to each other. We know of several scholastic doctors, who appropriate for themselves the title of Thomists and whose teaching is contradictory in many points. And we are aware that some of the doctrines, which by one school are supposed to be fundamental in the Thomistic Philosophy, are neglected and may be rejected by another school. […]

“Hence a further official declaration was necessary.”[7]

It is indeed necessary, not least because the 1917 Code of Canon Law enjoins the “rational theology and philosophy” of St Thomas on both seminarians and religious.[8] Had the Church made such a law, whilst leaving the matter unclear?

She had not. The further official declaration came in 1914 when the Congregation of Studies published what has come to be known as “The Twenty-Four Thomistic Theses”. The introduction to this document tells us that, following St Pius X’s 1914 Motu Proprio Doctoris Angelici, several professors from different institutions drew up a set of philosophical theses – particularly to do with metaphysics – which they had been teaching and defending as St Thomas’s principles.

The Sacred Congregation then states that it had examined the theses and submitted them to the Pope, who had commanded that they be published as “clearly contain[ing] the principles and major propositions of the holy Doctor.”[9]

In 1916, they “were all officially declared to contain the genuine teaching of St. Thomas.”[10] This later document said that they were to be proposed as safe norms – and Lumberas notes that they were to be “[p]roposed, not imposed: since it is philosophy, not faith, which is concerned.”[11]

Lumberas continues:

“But they must be proposed; namely, taught. For we have such an interpretation in the following words of Pius X:

“’The chief doctrines of St. Thomas’ philosophy cannot be regarded as mere opinions – which anyone might discuss pro and con, but rather as a foundation on which all science of both natural and divine things rests. If they are taken away, or perverted in any way, then this necessarily follows: that the students of sacred studies will not perceive even the meaning of those words whereby the divinely revealed dogmas are uttered by the teaching of the Church.’

“’These theses must be taught as a sure guide of direction; sure guide of direction on the philosophical official teaching in the Church; sure guide of direction on the support, which faith derives from philosophy; and sure guide of direction on philosophical truth.’” [12]

Lumbreras concludes his article by noting that these twenty-four theses all concern metaphysics, “since it was chiefly upon the metaphysical teaching of St. Thomas that the Popes insisted.”[13]

These are those theses.

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Decree of Approval of some theses contained in the Doctrine of St. Thomas Aquinas and proposed to the Teachers of Philosophy

Sacred Congregation of Studies

27 July 1914

B. Card Lorenzelli, Praefectus

Ascensus Dandini, a Secretis

The theses are presented in Alan Aversa’s version of Hugh MacDonald’s translation, along with Lumbreras’s commentaries included in Garrigou-Lagrange’’s The Essence and Topicality of Thomism. We have done our best to contact Hugh MacDonald but have been unable to do so.

After our most Holy Father Pius X ordered, in the Motu Proprio Doctoris Angelici on 29 June 1914, that in all schools of philosophy the principles and main teachings of Thomas Aquinas be held, some teachers from various institutions proposed some theses for this Sacred Congregation to examine, which theses they had been accustomed to teach and defend as being those of the Holy Teacher [St. Thomas], especially in metaphysics.

This Sacred Congregation, having duly examined the aforementioned theses and having presented them to the Holy Father, by the mandate of His Holiness, declares that they clearly contain the principles and more important thoughts of the holy Doctor [St. Thomas].

They are as follows:


Thesis I

Potency and Act so divide being that whatsoever exists either is a Pure Act, or is necessarily composed of Potency and Act, as to its primordial and intrinsic principles.


Commentary: Every actual subsisting being – inanimate bodies and animals, men and angels, creatures and Creator – must be either Pure Act – a perfection which is neither the complement of Potency, nor the Potency which lacks further complement – or Potency mixed with Act – something capable of perfection and some perfection fulfilling this capacity. This statement is true both in the existential and in the essential order. In each of these orders the composition of Act and Potency is that of two real, really distinct principles, as Being itself; intrinsic to the existing being or to its essence; into which, finally, all other principles can be resolved, while they cannot be resolved into any other. [Summa Theologiae, Iª q. 77 a. 1; Sententia Metaphysicae, lib. 7 l. 1 et lib. 9 l. 1 et l. 9]

Thesis II

Act, because it is perfection, is not limited except by Potency, which is capacity for perfection. Therefore, in the order in which the Act is pure, it is unlimited and unique; but in that in which it is finite and manifold, it comes into a true composition with Potency.


Commentary: Since Act means perfection, perfection belongs to Act by reason of itself; imperfection, then, by reason of something else. Limits, therefore, belong to Act but on account of Potency. Consequently, if an Act is pure, it is perfection without limits, and gives no ground for distinction and multiplicity. On the contrary, any finite or manifold Act is mixed with Potency: for it is only as subjected in Potency that it is limited and multiplied according to the capacity of the subject. [Summa Theologiae, Iª q. 7 a. 1 et a. 2; Contra Gentiles, lib. 1 cap. 43; Super Sent., lib. 1 d. 43 q. 2]

Thesis III

Wherefore, in the exclusive domain of existence itself God alone subsists, He alone is the most simple. Everything else, which participates in existence, has a nature whereby existence is restricted, and is composed of essence and existence as of two really distinct principles.


Commentary: If there is any being, the actuality of whose existence – for existent means actual – is not received into the potentiality of essence, such a being subsists of itself, because it is perfection without limits; it is unique, because it excludes composition of any kind; it is the most simple Being: God. All other things, the actuality of whose existence is received into the potentiality of the essence, participate in existence according to the capacity of the essence, which limits in this way the actuality of existence. Essence and existence hold in them the place of Potency and Act in the existential order, and are two real and really distinct principles, which intrinsically constitute the compound, the existing being, in the order of existence. [Summa Theologiae, Iª q. 50 a. 2 ad 3; Contra Gentiles, lib. 1 cap. 38 et cap. 52 et cap. 53 et cap. 54; Super Sent., lib. 1 d. 19 q. 2 a. 2; De ente et essentia, cap. 5; De spiritualibus creaturis, a. 1; De veritate, q. 27 a. 1 ad 8]

Thesis IV

Being, which derives its name from existence, is not predicated univocally of God and creatures; nor yet merely equivocally, but analogically, by the analogy both of attribution and of proportionality.


Commentary: If the actuality of existence is in God a Pure Act and is in creatures an Act mixed with Potency, Being cannot be predicated of God and creatures in an identical way: God is self-existing, creatures have their existence from God. Still, because the effect in some manner reproduces its cause, Being does not belong to God and creatures in a totally different sense. Being, as predicated of God and creatures is an analogous term. Its analogy is first that of attribution, since Being appertains to creatures as far as they have it from God, to whom it appertains by essence; and is secondly that of proportionality, since the actuality of existence is intrinsic to God and creatures as existing beings. [Summa Theologiae, Iª q. 13 a. 5; Contra Gentiles, lib. 1 cap. 32 et cap. 33 et cap. 34; De potentia, q. 7 a. 7]

Thesis V

There is, moreover, in every creature a real composition of subsisting subject with forms secondarily added – that is, accidents; but such a composition could not be understood unless the existence were received into a distinct essence.


Commentary: The compound of essence and existence is itself the subject or Potency of a further complement or Act: this Act or complement is but an accidental perfection. The new composition is a real one, as the addition itself is real. It can be observed in every creature. Bodies have quantity, spirits have faculties and operations upon which, furthermore, quality follows; every creature has some relation to the Creator. But this real composition of accidents and subsisting compound lacks a philosophical basis if we put aside the composition of essence and existence. The subsisting being cannot be the subject of accidental Act except in so far as it is Potency; but existence is not Potency. The actuality, then, of existence and that of accident come together in the same substantial essence only because this essence is a Potency really distinct from both Acts. [Summa Theologiae, Iª q. 3 a. 6; Contra Gentiles, lib. 1 cap. 23; Contra Gentiles, lib. 2 cap. 52; De ente et essentia, cap. 5]

Thesis VI

Besides the absolute accidents there is also a relative accident, or ‘toward something.’ For although ‘toward something’ does not mean, by its own nature, anything inhering in something, frequently, however, it has a cause in things, and, therefore, a real entity distinct from the subject.


Commentary: In addition to the absolute accidents – which modify the subject in itself – there is a relative accident – which affects the subject with respect to something else. The proper nature of predicamental relation consists in the very habitude to something else; relation, as relation, does not indicate inherence in something, but reference toward something. We may think of a merely logical relation. This is not always the case. For often we have a real subject, and a real and distinct term, and a real foundation, no one of which, however, is that very habitude which relation means. [Summa Theologiae, Iª q. 28 a. 1]

Thesis VII

The spiritual creature is as to its essence altogether simple. Yet there remains a twofold composition in it: that, namely, of essence with existence and that of substance with accidents.


Commentary: The essence of angels is only Act, for the actuality of the form is not received into the potentiality of matter. Angels, indeed, are but intellectual substances, since to understand is a wholly immaterial operation. The last statement of the thesis has already been justified. [Summa Theologiae, Iª q. 50 a. 1 ff.; De spiritualibus creaturis, a. 1]


Thesis VIII

The corporeal creature, on the contrary, is in its very essence composed of Potency and Act. Such a Potency and Act of the essential order are designated by the names of matter and form.


Commentary: Besides the composition in the existential and accidental order, bodies are composed also in the order of essence. Bodies, indeed, are extended and active, divisible and yet one, multiplied in individuals while keeping specific unity, subject to substantial changes, which by different and often contrary successive properties are made known. Consequently, there must be in bodies an intrinsic principle as the basis of extension, division, numerical multiplicity, the permanent subject of the substantial change; and another intrinsic principle as the foundation of the activity, unity, specific likeness, the successive phases of the change. The first principle, passive, undetermined, incomplete, potential, the root of extension, the support of the substantial change, is material and substantial. The second, active, determining, completing, term of the substantial change, is substantial and formal. Matter and form, then, constitute the essence of bodily substance: neither one is an essence, a substance, a body: each is but a part of the compound, which is a single essence, a single substance, a single body. [De spiritualibus creaturis, a. 1]

Thesis IX

Neither of those parts has existence, properly speaking; nor is produced or destroyed; nor is placed in a Category except by way of reduction, as a substantial principle.


Commentary: Since existence is the Act of essence, neither matter nor form can be granted an existence of its own; the existence belongs to the compound. And because production brings things into existence, and destruction deprives them of it, the term of production or destruction is likewise the compound. Finally, since matter and form are substantial principles, they cannot be collocated among accidents. But neither can they be placed directly in the category of substance, for it is the complete substance, which is classed there. They fall, then, into the category of substance by reduction, as principles of substance, as substantial Potency and substantial Act. [Summa Theologiae, Iª q. 45 a. 4; De potentia, q. 3 a. 5 ad 3]

Thesis X

Although extension into integral parts follows corporeal nature, it is not, however, the same for a body to be a substance and to be extended. For substance of itself is indivisible; not certainly after the manner of a point, but after the manner of that which is outside the order of dimension. On the other hand, quantity, which makes substance to be extended, really differs from substance, and is a veritable accident.


Commentary: To have integral parts – homogeneous, distinct and outside of each other, united together at the extremities – is a proper sequence of matter, one of the essential principles of body. Still, body as a substance implies only essential parts, matter and form – heterogeneous, within each other, united together by compenetration. Substance, of itself, is indifferent to any quantity, and may even exist, miraculously, without any quantity. It is, then, of itself indivisible: not simply as a point – unextended by privation,  – but as something devoid of dimension – unextended by negation. Substance is indebted to quantity for its integral parts; but as there is a real distinction between subject-of-existence and extended-into-parts, between the persevering support of successive quantities and these quantities in succession, substance is not really identical with quantity. Faith teaches us that in the Holy Eucharist the substance of bread disappears, but not its quantity. Quantity, therefore, is a genuine accident. [Contra Gentiles, lib. 4 cap. 65; Super Sent., lib. 1 d. 37 q. 2 a. 1 ad 3; Super Sent., lib. 2 d. 30 q. 2 a. 1]

Thesis XI

Matter as subjected to quantity is the principle of individuation or numerical distinction – impossible among pure spirits – whereby individuals of the same species are distinct from each other.


Commentary: The principle of individuation cannot be the essence, for Peter is not humanity; nor some extrinsic mode added to the composite substance, for this mode, if accidental, cannot constitute an individual which is a substance and substantially differs from other individuals, and, if substantial, cannot be received but into some already constituted individual substance; nor the existence, for existence actualizes, does not modify reality and is received, moreover, into a substance which is an individual substance. Though that principle must be intrinsic to the substance, it is not the form, because form is a principle of specific and common unity rather than of numerical multiplicity and incommunicability. This principle is matter. Yet not matter of itself, since of itself it is undetermined and capable of being in this and that individual, while the principle of individuation is a determining principle, and renders the subject incommunicable. Matter, as subjected to quantity, is such a principle. For, as related to quantity, it is conceived as divisible into homogeneous parts, and, as related to this quantity, it is conceived as incapable of some other quantity, and, then, as incommunicable to anything else related to different quantity. It is because pure spirits are not composed of matter and form, but are simple forms, Act only which exhausts by itself all the perfection of the essential order, that they cannot be multiplied in the same species: the individuals, indeed, would differ on account of their form, and a difference on the part of the form makes a difference in the species. [Contra Gentiles, lib. 2 cap. 92 et cap. 93; Summa Theologiae, Iª q. 50 a. 4; De ente et essentia, cap. 2]

Thesis XII

It is also quantity that makes a body to be circumscriptively in one place and to be incapable, by any means, of such a presence in any other place.


Commentary: Since quantity makes a body to be extended, and, thus, to have its parts outside of each other, it makes the whole body to occupy some place so that each part of the body occupies a different portion of the place. We have, therefore, some commensuration of the dimensions of the body with the dimensions of the place; and this we call a circumspective presence. But just on account of this commensuration quantity makes a body to be incapable of circumscriptive presence in more than one place; for the dimensions of the body are equal, not greater than the dimensions of the first place, and, since those dimensions are exhausted by this place, it is not possible for the same body to occupy simultaneously a second place. This impossibility is, therefore, a metaphysical one: not even by a miracle can we conceive of any such bilocation. [Summa Theologiae, IIIª q. 75; Super Sent., lib. 4 d. 10 q. 1 a. 3]


Thesis XIII

Bodies are divided into two classes: some are living, others without life. In living bodies, in order to have intrinsically a moving part and a moved part in the same subject, the substantial form, called the soul, requires an organic disposition, or heterogeneous parts.


Commentary: Not all bodies are endowed with life: but some are. As living bodies, they have within themselves the principle and the term of their movement. This is to be understood, not as if the whole body, or one and the same part of the body, were both the mover and the moved, but that by nature one part is ordained to give and another part to receive the motion. The different parts, then, must be arranged into some hierarchy, and must be coordinated, not only as regards the whole, but even with respect to each other: all the parts, accordingly, cannot be homogeneous. The soul, substantially informing the organism, informs all the parts, and each of them according to the function each has in the whole. [Summa Theologiae, Iª q. 18 a. 1 et a. 2 et q. 75 a. 1; Contra Gentiles, lib. 1 cap. 97; Sententia De anima]

Thesis XIV

Souls of the vegetative and sensitive order, properly speaking, do not subsist and are not produced, but merely exist and are produced as a principle whereby the living thing exists and lives. Since they depend entirely on matter, at the dissolution of the compound, they are indirectly destroyed.


Commentary: The substantial form does not subsist in the organic bodies of plants and irrational animals, because it has no operation independent of matter; it is but a principle of substance. A principle, however, that, in giving matter the complement wanted by matter for making up the compound – which properly exists and lives – is called the principle of existence and life. Its relation to production and destruction has been previously explained. [Summa Theologiae, Iª q. 75 a. 3 et q. 90 a. 2; Contra Gentiles, lib. 2 cap. 80 et cap. 82]

Thesis XV

On the contrary, the human soul subsists by itself, and is created by God when it can be infused into a sufficiently disposed subject, and is incorruptible and immortal by nature.


Commentary: The human soul, independent of material conditions for some of its operations, is by itself a simple and complete substance. It is, then, produced from nothing, or created, and created by God, as we shall see. Naturally ordained to inform the human body, it is created when infused into the body. But, since the reception of any form presupposes a convenient disposition in the receiving matter, the infusion of the human soul implies a sufficient disposition of the human body. Such a disposition is not likely to be found in a body recently formed: vegetative and sensible souls would precede the human soul, as the servants precede the master for preparing a lodging worthy of him. Being simple, the human soul cannot be directly destroyed. Being subsisting, it can neither be destroyed indirectly upon the destruction of the compound. [Summa Theologiae, Iª q. 75 a. 2 et q. 90 et q. 118; Contra Gentiles, lib. 2 cap. 83 ff.; De potentia, q. 3 a. 2; Sententia De anima, a. 14]

Thesis XVI

This same rational soul is so united to the body as to be its single substantial form. By it man is man, and animal, and living, and body, and substance, and being. Soul, therefore, gives man every essential degree of perfection. It communicates to the body, furthermore, the act of existence whereby itself exists.


Commentary: Every one is aware of the intrinsic and mutual influence, which exists in man between body and soul. Their union is not accidental. Body and soul come together as two constituent principles of a single nature, that of man. The human soul, the substantial form of body, gives matter, the substantial potency of soul, the first substantial act. By itself, then, it informs and determines the undetermined matter to a particular species. It gives to the compound all the perfection, which is implied in this species. And it is subsisting; it communicates its existence directly to the compound, indirectly to the body. [Summa Theologiae, Iª q. 76; Contra Gentiles, lib. 2 cap. 56 et cap. 68 et cap. 69 et cap. 70 et cap. 71; Sententia De anima, a. 1; De spiritualibus creaturis, a. 3]

Thesis XVII

Faculties of a twofold order, organic and inorganic, naturally spring from the human soul. The subject of the organic, to which sense belongs, is the compound. The subject of the inorganic is the soul alone. The intellect, then, is a faculty intrinsically independent of any organ.


Commentary: The immediate principles of operation are distinct from the soul: they are accidents, as the operations themselves. But their root is the soul, for they are vital faculties, and the soul is the principle of life. They are divided into two classes, according to the mode in which they spring from the human soul; subsisting by itself, and the form of body. In the latter case we have those faculties whose act is performed by means of bodily organs. Not only the vegetative faculties, but the sensitive likewise, are among them; for their object is extended. As organic faculties, they have for their subject the animated organism, which is neither the soul alone, nor the body alone, but the compound. There are some other faculties whose operations are far above matter, and, accordingly, cannot be subjected in the organism, even as animated: they are termed inorganic and are subjected in the soul alone. Intellect is such a faculty. Though extrinsically dependent on the imagination and indirectly on the organism, it is intrinsically independent of them. [Summa Theologiae, Iª q. 77 et q. 78 et q. 79; Contra Gentiles, lib. 2 cap. 72; Sententia De anima, a. 12 ff.; De spiritualibus creaturis, a. 11]

Thesis XVIII

Intellectuality necessarily follows immateriality, and in such a manner that the degree of intellectuality is in proportion to the remoteness from matter. The adequate object of intellection is being as such; but the proper object of the human intellect, in the present state of union, is restricted to the essences abstracted from material conditions.


Commentary: Intellectuality means ability to reproduce in oneself the forms of the objects known, without any injury to the proper form. Matter determines forms to be but in this individual: no form can be known except as abstracted from matter; no subject can be intelligent except as independent of matter. A greater intellectuality corresponds to a greater immateriality, and, since matter stands for potency, to a greater act. In the summit of intellectuality the Pure Act is fixed; next, the Act mixed with Potency in the order of existence; then, the Act mixed with Potency in the very order of essence. A form cannot be reproduced except in so far as it is. Being is knowable in itself, and everything is knowable in so far as it is being. Still, the mode of operation is according to the mode of being, and since the being of our soul, in the present condition, communicates with the body, the connatural object of our knowledge is now the forms taken from the matter. [Summa Theologiae, Iª q. 14 a. 1 et q. 89 a. 1 et a. 2; Contra Gentiles, lib. 1 cap. 59 et cap. 72 et lib. 4 cap. 2]

Thesis XIX

We, therefore, receive our knowledge from sensible things. But since no sensible thing is actually intelligible, besides the intellect which is properly intelligent we must admit in the soul an active power which abstracts the intelligible forms from the phantasms.


Commentary: Our knowledge proceeds, at present, from sensible things. This gives a reason for the union of soul and body. Upon the injury of some organs our mental operation becomes impossible; nor is it by chance that this is associated with sensible images. A sensible image, however, is not intelligible; for intelligible means immaterial. The intellect, which properly understands is a passive faculty: it receives the intelligible forms, and does not make the forms to be intelligible. The abstractive faculty, notwithstanding, belongs to the soul alone, for it brings its object to the realm of the immaterial. It is, moreover, an intellectual faculty, for its function is to make something intelligible. It is called the active intellect. [Summa Theologiae, Iª q. 79 a. 3 et a. 4 et q. 85 a. 6 et a. 7; Contra Gentiles, lib. 1 cap. 76 ff.; De spiritualibus creaturis, a. 10]

Thesis XX

Through these species we directly know the universal; the singular we know by the senses, and also by the intellect through a conversion to the phantasms; we rise by analogy to the knowledge of the spiritual.


Commentary: Since matter individualizes the forms, the forms become universal when abstracted from matter: it is the universal, then, we know directly. The singular implies material conditions and is known directly by the senses, dependent on matter themselves, and indirectly by the intellect, which, in taking the universal from the individuals, perceives the individuals, which offer the universal. Starting from the material abstracted essences we arrive at the nature of pure spirits. We affirm of those spirits some positive perfections noticed in the inferior beings, and these we affirm of them in a higher degree, while we deny of them some, or all, the imperfections to which those perfections were associated in the material objects. [Summa Theologiae, Iª q. 85 et q. 86 et q. 87 et q. 88]

Thesis XXI

The will follows, does not precede, the intellect; it necessarily desires that which is offered to it as a good which entirely satisfies the appetite; it freely chooses among several good things that are proposed as desirable by the wavering judgment. Election, then, follows the last practical judgment; still, it is the will which determines it to be the last.


Commentary: Will is not prior but posterior to the intellect, in dignity, in origin, in acting. The posteriority in acting is chiefly intended here. Every act of the will is preceded by an act of the intellect; for the act of the will is a rational inclination, and while inclination follows a form, rational inclination follows the intellectually apprehended form. The intellect, in presenting to the will some apprehended good, moves it as to the specification of its act. If the presented good is the absolute or universal good, the will desires it of necessity. If it is good mixed with evil, relative or particular good, it is partially attractive and partially repulsive. The will may desire it, or may not. Once the intellect has settled on the practical excellency of some particular good, the will must accept such an object. Yet, it is the will, which freely committed itself to the determination of the intellect; it is the will, which freely sustained the intellect in its unilateral consideration; and it is the will, which freely wants the process not to be submitted to a further revision. [Summa Theologiae, Iª q. 82 et q. 83; Contra Gentiles, lib. 2 cap. 72 ff.; De veritate, q. 22 a. 5; De malo, q. 11]


Thesis XXII

That God exists we do not know by immediate intuition, nor do we demonstrate it a priori, but certainly [and] a posteriori, that is, by things which are made, arguing from effect to cause. Namely,

  1. From things which are in movement and cannot be the adequate principle of their motion – to the first mover immovable;
  2. From the procession of worldly things from causes which are subordinated to each other [causes subordinated intrinsically, as opposed to temporally] – to the first uncaused cause;
  3. From corruptible things, which are indifferent alike to being and non-being [i.e. they can either be or not be, they are not necessary beings] – to the absolutely necessary being;
  4. From things, which, according to their limited perfection of existence, life, intelligence, are more or less perfect in their being, their life, their intelligence – to Him who is intelligent, living, and being in the highest degree;
  5. Finally, from the order, which exists in the universe – to the existence of a separate intelligence which ordained, disposed, and directs things to their end. [Numbers added]

Commentary: Since the proper object of our intellect is the essences of material things, it is clear we have no immediate intuition of God’s spiritual essence, and, consequently, neither of His existence. Since the notion we have of His essence is an abstract notion, the existence implied in that notion belongs to the essential order and in no way to the actual. Still, we can demonstrate His existence with a rigorous demonstration, which goes from the effects to their ultimate cause. St. Thomas furnishes five proofs, already classical. Things are in movement; whatsoever is moved is moved by something else; above the moved-movers is some immovable-mover. Things are efficient causes of others; they are not the efficient cause of themselves; outside the caused-causes is some uncaused-cause. Some beings did not always exist, some will not always exist: their existence is not essential to them; above beings, which do not exist of necessity, is a necessary being. Things are more or less perfect than others; the less perfect has not in itself the reason of that perfection; above things, which are limited in their perfection is some being supremely perfect. Things which lack intelligence act for some end; an intelligent being only could adapt and direct them to this end; there is an universal governing intelligence. [Summa Theologiae, Iª q. 2; Contra Gentiles, lib. 1 cap. 12 et cap. 31 et lib. 3 cap. 10 et cap. 11; De veritate, q. 1 et q. 10; De potentia, q. 4 et q. 7]

Thesis XXIII

The Divine Essence is well proposed to us as constituted in its metaphysical concept by its identity with the exercised actuality of its existence, or, in other terms, as the very subsisting being; and by the same token it exhibits to us the reason of its infinity in perfection.


Commentary: Nothing in the Divine Essence itself can have the character of a constituent, for the Divine Essence is most simple. It is only according to our mode of understanding that we may ask which among the different perfections attributed to God is conceived as first, so as to distinguish God from creatures and to give ground to all the other divine perfections. That first perfection is the real identity of essence and existence: the subsisting being. By that God is distinct from creatures. In that is based any other perfection belonging to Him; for existence means act, and existence which is not received into essence means act without potency, perfection without limits. [Summa Theologiae, Iª q. 4 a. 2 et q. 13 a. 11; Super Sent., lib. 1 d. 8 q. 1]

Thesis XXIV

By the very purity of His being God is, therefore, distinguished from all finite beings. Hence, in the first place, it is inferred that the world could not have proceeded from God except through creation; secondly, that the creative power, which directly ‘affects being as being,’ cannot be communicated, even miraculously, to any finite nature; and, finally, that no created agent exercises any influence on the being of any effect except through a motion received from the first cause.


Commentary: God’s essence is God’s existence; God is distinct from creatures whose essence is potency for existence. The world proceeds from God as the contingent from the necessary being. It proceeds by means of creation, for no emanation is possible in the pure act. Since creation implies the production of being from non-being, it is contradictory to suppose a creature exercising any causality in creation; it could not exercise that causality which belongs to the principal cause, for being is an universal effect, above the proportion consequently of any particular cause; not that causality which belongs to the instrumental cause, for there is nothing presupposed to creation upon which the instrument could exercise its efficiency. Finally, since every agent, by its act, moves toward the effect, this movement cannot be conceived independently of the first mover. The agent depends on God for its existence, for its powers, for the conservation of that existence and of these powers. It depends also on God for the very exercise of these powers. Because in exercising these powers the agent passes from Potency to Act, its faculties do not move except in so far as they are moved; there must be a motion coming from the immovable mover. This motion is received into the agent previously to the agent’s motion; it is properly called pre-motion. And since it moves the agent to the exercise of its powers, it is properly called physical pre-motion. [Summa Theologiae, Iª q.44 et q. 45 et q. 105; Contra Gentiles, lib. 2 cap. 6 et cap. 7 et cap. 8 et cap. 9 et cap. 10 et cap. 11 et cap. 12 et cap. 13 et cap. 14 et cap. 15 et lib. 3 cap. 6 et cap. 7 et cap. 8 et cap. 9 et lib. 4 cap. 44; De potentia, q. 3 a. 7]

Concluding thoughts

Let’s end with the words of Pope St Pius X in Doctoris Angelici:

“These are the theses Catholic professors must teach. They are the foundation upon which all the philosophical teaching must be based. And if professors recommend to their students any textbook that does not correspond to these theses, they must point that out. Because Catholic professors are reminded not only that ‘they cannot set St. Thomas aside, however slightly, especially in Metaphysics, without grave detriment,’ but also that ‘they did not receive the faculty of teaching to communicate to their pupils their own opinions, but to impart to them the doctrines most approved by the Church.'”

Commentary by Pedro Lumbreras, “The Twenty-Four Fundamental Theses of Official Catholic Philosophy,” The Homiletic and Pastoral Review 23 (July 1923): 1040–53. Latin translation of theses by Hugh McDonald, trans., “Sacred Congregation of Studies – Theses Contained in the Doctrine of St. Thomas Aquinas,” accessed January 31, 2020, http://scholastic.us.to/24Thomisticpart2.htm. Citations of St. Thomas from Fr Édouard Hugon, Les vingt-quatre thèses thomistes (Paris: Téqui, 1946), https://archive.org/details/SelectionsFromTheRevueThomiste

Further Reading

Supporting The WM Review through book purchases
As Amazon Associates, we earn from qualifying purchases through our Amazon links. Click here for The WM Review Reading List (with direct links for US and UK readers).

St Thomas Aquinas – Summa Theologica Trans. by the Fathers of the English Dominican Province, (5 vols.) Ave Maria Press, Hardback (and UK readers) and Paperback (and UK readers). Also online at New Advent and iPieta.

Mgr Paul J. Glenn Introduction to Philosophy. Get this book. If you read nothing else, at least read this – it summarises all of the following books. Internet Archive. Reprint (better quality) from Gyan Books.

Rev Henri Grenier’s Thomistic Philosophy

Volume I: Logic and Philosophy of Nature (and for UK readers)

Volume II: Metaphysics (and for UK readers)

Volume III: Moral Philosophy (and for UK readers)

More reading suggestions on this topic available here:

Learning Sacred Theology I: Preliminaries, Catechism, Latin, Philosophy and the Magisterium.

St Thomas Aquinas

St Thomas, Universal Doctor – Fr Edward Leen CSSP
The Holy Wrath of St Thomas Aquinas – G.K. Chesterton
On the Five Qualities of Prayer – St Thomas Aquinas
True Law – According to the Teaching of St Thomas Aquinas
What is Thomism? The Twenty-Four Thomistic Theses

St Thomas Aquinas and the Church – His Intrinsic Authority
St Thomas Aquinas and the Church – His Extrinsic Authority

The “Angelic Warfare Confraternity” of the Cord of St Thomas – Translation of an 1863 pamphlet
“The Angelic Warfare Confraternity” – Robinson OP, 1941

The Fioretti of St Thomas:
Part I: His Life
Part II: His Death
Part III: The Miracles after his Death


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[1] Pope St Pius X, Encyclical Pascendi Dominic Gregis, 1907, n. 45. Available at https://www.vatican.va/content/pius-x/en/encyclicals/documents/hf_p-x_enc_19070908_pascendi-dominici-gregis.html

[2] Pedro Lumbreras, ‘The Twenty-Four Fundamental Theses of Official Catholic Philosophy,’ The Homiletic and Pastoral Review 23 (March 1923): 588-98, contained within Reginald Garrigou-Lagrange’s The Essence and Topicality of Thomism, trans. Alan Aversa, 2013, pp 51-82. P 55. (UK link here)

[3] Pascendi n. 45

[4] Lumbreras, in Garrigou-Lagrange, 59.

[5] Pope St Pius X, Motu Proprio Doctoris Angelici, 1914. Available at: https://web.archive.org/web/20220311230024/https://sspx.org/en/motu-proprio-doctoris-angelici

[6] Ibid.

[7] Lubreras 59-60.

[8] Canons 1366 §2 and 589, from The 1917 or Pio-Benedictine Code of Canon Law, in English Translation with Extensive Scholarly Apparatus, trans. Dr Edward Peters, Ignatius Press, San Francisco, 2001

[9] Sacred Congregation of Studies, Decree of Approval, in Garrigou-Lagrange, 63.

[10] Lumbreras, in Garrigou-Lagrange, 60 – citing AAS May 1916.

[11] Lumbreras, in Garrigou-Lagrange, 60

[12] Ibid, 60-1 citing Doctoris Angelici.

[13] Lumbreras, in Garrigou-Lagrange, 60.

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