Joseph Ratzinger recommends the study of Saint Thomas Aquinas as a necessary corrective to the present intellectual crisis. "Since Thomas can no longer be presupposed, he should now be discussed especially as a contrast to Bonaventure."
Joseph Ratzinger, Dogma and Preaching (first German ed., 1973), San Francisco: Ignatius, 2005, 143.
A philosopher who holds all of the theses listed below is called a Thomist.
THE 24 THOMISTIC THESES
A number of popes and church law direct that the method, doctrines, and principles of St. Thomas Aquinas be taught in schools and especially in seminaries. After a special statement on this matter by Pope Pius X (Motu Proprio Doctoris Angelici June 29, 1914) a number of philosophy professors met, drew up a list of the principles and major tenets of St. Thomas, and submitted the list to the Sacred Congregation of Studies. On July 27, 1914, this Congregation declared that in their judgment this list contained the principles and major tenets of St. Thomas' philosophy, especially in metaphysics.
The Congregation itself, in 1916, declared that these were safe, directive norms. Though the list often does not give the exact wording of St. Thomas, it is sure that the ideas are St. Thomas'. Hence, if St. Thomas is the safe, approved teacher of philosophy for Catholics, his ideas must be safe and approved norms. A philosopher who intellectually accepts all of these theses is named a Thomist; and this meaning of the term Thomist is about the only definite meaning that can be assigned to it. The theses are given here for convenient reference.
"We admonish professors to bear well in mind that they cannot set aside St. Thomas, especially in metaphysical questions, without grave disadvantage". --Pope St. Pius X (1903-1914), Pascendi Dominici Gregis, September 8, 1907
These 24 propositions are a concise guide of the whole philosophy and can be divided as follows:
Ontology (Th. 1 – 7) ; Cosmology (Th. 8 – 12) ; Psychology (Th. 13 – 21) ; Theodicy (Th. 22 – 24)
ONTOLOGY
1 . Potency and Act divide being in such a way that whatever is, is either pure act, or of necessity it is composed of potency and act as primary and intrinsic principles.[1]
2. Since act is perfection, it is not limited except through a potency which itself is a capacity for perfection. Hence in any order in which an act is pure act, it will only exist, in that order, as a unique and unlimited act. But whenever it is finite and manifold, it has entered into a true composition with potency.[2]
3. Consequently, the one God, unique and simple, alone subsists in absolute being. All other things that participate in being have a nature whereby their being is restricted; they are constituted of essence and being, as really distinct principles.[3]
4. A thing is called a being because of being ("esse"). God and creature are not called beings univocally, nor wholly equivocally, but analogically, by an analogy both of attribution and of proportionality.[4]
5. In every creature there is also a real composition of the subsisting subject and of added secondary forms, i.e. accidental forms. Such composition cannot be understood unless being is really received in an essence distinct from it.[5]
6. Besides the absolute accidents there is also the relative accident, relation. Although by reason of its own character relation does not signify anything inhering in another, it nevertheless often has a cause in things, and hence a real entity distinct from the subject.[6]
7. A spiritual creature is wholly simple in its essence. Yet there is still a twofold composition in the spiritual creature, namely, that of the essence with being, and that of the substance with accidents.[7]
8. However, the corporeal creature is composed of act and potency even in its very essence. These act and potency in the order of essence are designated by the names form and matter respectively.[8]
COSMOLOGY
9. Neither the matter nor the form have being of themselves, nor are they produced or corrupted of themselves, nor are they included in any category otherwise than reductively, as substantial principles.[9]
10. Although extension in quantitative parts follows upon a corporeal nature, nevertheless it is not the same for a body to be a substance and for it to be quantified. For of itself substance is indivisible, not indeed as a point is indivisible, but as that which falls outside the order of dimensions is indivisible. But quantity, which gives the substance extension, really differs from the substance and is truly an accident.[10]
11. The principle of individuation, i.e., of numerical distinction of one individual from another with the same specific nature, is matter designated by quantity. Thus in pure spirits there cannot be more than individual in the same specific nature.[11]
12. By virtue of a body's quantity itself, the body is circumscriptively in a place, and in one place alone circumscriptively, no matter what power might be brought to bear.[12]
13. Bodies are divided into two groups; for some are living and others are devoid of life. In the case of the living things, in order that there be in the same subject an essentially moving part and an essentially moved part, the substantial form, which is designated by the name soul, requires an organic disposition, i.e. heterogeneous parts.[13]
PSYCHOLOGY
14. Souls in the vegetative and sensitive orders cannot subsist of themselves, nor are they produced of themselves. Rather, they are no more than principles whereby the living thing exists and lives; and since they are wholly dependent upon matter, they are incidentally corrupted through the corruption of the composite.[14]
15. On the other hand, the human soul subsists of itself. When it can be infused into a sufficiently disposed subject, it is created by God. By its very nature, it is incorruptible and immortal.[15]
16. This rational soul is united to the body in such a manner that it is the only substantial form of the body. By virtue of his soul a man is a man, an animal, a living thing, a body, a substance and a being. Therefore the soul gives man every essential degree of perfection; moreover, it gives the body a share in the act of being whereby it itself exists.[16]
17. From the human soul there naturally issue forth powers pertaining to two orders, the organic and the non-organic. The organic powers, among which are the senses, have the composite as their subject. The non-organic powers have the soul alone as their subject. Hence, the intellect is a power intrinsically independent of any bodily organ.[17]
18. Intellectuality necessarily follows upon immateriality, and furthermore, in such manner that the father the distance from matter, the higher the degree of intellectuality. Any being is the adequate object of understanding in general. But in the present state of union of soul and body, quiddities abstracted from the material conditions of individuality are the proper object of the human intellect.[18]
19. Therefore, we receive knowledge from sensible things. But since sensible things are not actually intelligible, in addition to the intellect, which formally understands, an active power must be acknowledged in the soul, which power abstracts intelligible likeness or species from sense images in the imagination.[19]
20. Through these intelligible likenesses or species we directly know universals, i.e. the natures of things. We attain to singulars by our senses, and also by our intellect, when it beholds the sense images. But we ascend to knowledge of spiritual things by analogy.[20]
21. The will does not precede the intellect but follows upon it. The will necessarily desires that which is presented to it as a good in every respect satisfying the appetite. But it freely chooses among the many goods that are presented to it as desirable according to a changeable judgment or evaluation. Consequently, the choice follows the final practical judgment. But the will is the cause of it being the final one.[21]
THEODICY
22. We do not perceive by an immediate intuition that God exists, nor do we prove it a priori. But we do prove it a posteriori, i.e., from the things that have been created, following an argument from the effects to the cause: namely, from things which are moved and cannot be the adequate source of their motion, to a first unmoved mover; from the production of the things in this world by causes subordinated to one another, to a first uncaused cause; from corruptible things which equally might be or not be, to an absolutely necessary being; from things which more or less are, live, and understand, according to degrees of being, living and understanding, to that which is maximally understanding, maximally living and maximally a being; finally, from the order of all things, to a separated intellect which has ordered and organized things, and directs them to their end.[22]
23. The metaphysical motion of the Divine Essence is correctly expressed by saying that it is identified with the exercised actuality of its won being, or that it is subsistent being itself. And this is the reason for its infinite and unlimited perfection.[23]
24. By reason of the very purity of His being, God is distinguished from all finite beings. Hence it follows, in the first place, that the world could only have come from God by creation; secondly, that not even by way of a miracle can any finite nature be given creative power, which of itself directly attains the very being of any being; and finally, that no created agent can in any way influence the being of any effect unless it has itself been moved by the first Cause.[24]
In 1917, publishing the Canon Law, Pope Benedict XV ordered the method, doctrines and principles of St Thomas to be followed (Code, can. 1366, § 2) and gave as reference the decree of the Sacred Congregation approving the 24 Thesis.
Acta Apostolicae Sedis, Vl (1914), 38386, is the source of the list of theses. It evaluates them as a good statement of the principles and major views of St. Thomas' philosophy. The same Acta, VII (1916), 15758, refers to them as safe, directive norms.
[1] St Th. Ia. Q.77, a.1 ; Metaph. VII, 1 and IX, 1 and 9
[2] St Th. Ia. Q.7, a.1-2 ; Cont. Gent. I, c.43 ; I Sent. Dist.43, Q.2
[3] St Th. Ia. Q.50, a.2, ad 3 ; Cont. Gent. I, c.38,52,53,54 ; I Sent. Dist.19, Q.2, a.2 ; De Ent. et Ess. c.5 ; De Spir. Creat. a.1 ; De Verit. Q.27, a.1, ad 8
[4] St Th. Ia. Q.13, a.5 ; Cont. Gent. I, c.32,33,34 ; De Pot. Q.7, a.7
[5] St Th. Ia. Q.3, a.6 ; Cont. Gent. I, c.23 ; Cont. Gent. II, c.52 ; De Ent. et Ess. c.5
[6] St Th. Ia. Q.28, mainly a.1
[7] St Th. Ia. Q.50 and ff ; De Spirit. Creat. a.1
[8] St Th. De Spirit. Creat. a.1
[9] St Th. Ia. Q.45, a.4 ; De Pot. Q.3, a.5, ad 3 ;
[10] St Th. Cont. Gent. IV, c.65 ; I Sent. Dist. 37, Q.2, a.1, ad 3 ; II Sent. Dist. 30, Q.2, a.1
[11] St Th. Cont. Gent. II, c.92-93 ; Ia. Q.50, a.4 ; De Ent. et Ess. c.2
[12] St Th. IIIa. Q.75 ; IV Sent. Dist. 10, a.3
[13] St Th. Ia. Q.18, a.1-2 and Q.75, a.1 ; Cont. Gent. I, c.97 ; De Anima everywhere
[14] St Th. Ia. Q.75, a.3 and Q.90, a.2 ; Cont. Gent. II, c.80 and 82
[15] St Th. Ia. Q.75, a.2 and Q.90 and 118 ; Cont. Gent. II, c.83 and ff. ; De Pot. Q.3, a.2 ; De Anim. a.14
[16] St Th. Ia. Q.76 ; Cont. Gent. II, c.56, 68-71 ; De Anim. a.1 ; De Spirit. Creat. a.3
[17] St Th. Ia. Q.77-79 ; Cont. Gent. II, c.72 ; De Anim. a.12 and ff. ; De Spirit. Creat. a.11
[18] St Th. Ia. Q.14, a.1 and Q.74, a.7 and Q.89, a.1-2 ; Cont. Gent. I, c.59 and 72, and IV, c.2
[19] St Th. Ia. Q.79, a.3-4 and Q.85, a.6-7 ; Cont. Gent. II, c.76 and ff. ; De Spirit. Creat. a.10
[20] St Th. Ia. Q.85-88
[21] St Th. Ia. Q.82-83 ; Cont. Gent. II, c.72 and ff. ; De Verit. Q.22, a.5 ; De Malo Q.11
[22] St Th. Ia. Q.2 ; Cont. Gent. I, c.12 and 31 and III c.10-11 ; De Verit. Q.1 and 10 ; De Pot. Q.4 and 7
[23] St Th. Ia. Q.4 , a.2 and Q.13, a.11 ; I Sent. Dist. 8, Q.1
[24] St Th. Ia. Q.44-45 and 105 ; Cont. Gent. II, c.6-15 and III c.66-69 and IV c.44 ; De Pot. mainly Q.3, a.7
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