Thomas Aquinas’s Summa Theologiæ

The Nature of Sacred Doctrine

The late, Medieval theologian, Thomas Aquinas, stands as one of the brightest minds in Christian theology. Perhaps his most known work is his Summa Theologiæ. This work, though difficult, is very rewarding, especially his treatment on the nature of doctrine and the doctrine of God. As his readers will notice, Thomas’s writings are obviously influenced by Aristotle. Nevertheless, Scripture fills the pages—whether it be parenthetical citations or quotes. Though we, as the hearty Protestants that we are, would not agree with everything in Thomas’s work, we certainly would benefit at least interacting with him. He has a helpful approach to theology and, again, his treatment on the doctrine of God is quite impressive. So, how does Thomas structure this massive work?

The Structure of the Summa Theologiæ

Thomas breaks his Summa Theologiæ (ST) down into three divisions, called parts:

1. Prima Pars (Part 1), which deals with God
2. Prima/Secunda Secundæ (Part 2), in two sections, deals with humanity and morality
3. Tertia Pars (Part 3), which focuses on Christ

In each part, Thomas includes many questions. For example, in Part 1, there are 119 questions! To make this even more profound, each question has multiple articles. For example, Question (Q.) 1 has 10 articles. To break this down even more, each question has a few objections, an “on the contrary” (sed contra) statement, an exposition of Thomas’s thought, and then replies to each objection. So, we can break it down like this, starting from largest to smallest (see Thomas Aquinas chart link).

Thomas Aquinas Chart

Citing the Summa Theologiæ

Citing the ST can be tricky, but after a couple citations, you’ll get the gist. Here’s an example: Ia.1.7

- Ia refers to the the part (Part 1)

- 1 (or any number in the middle refers to the question number)

- 7 refers to an article within the question, so here, it's article 7.

So, Ia.2.3 would be part 1, question 2, article three.

To add on one more thing, you’ll sometimes see “sed contra” or “ad. 1” after a citation. Sed contra stands for the “on the contrary” statements; “ad. 1” stands for the reply to objection 1, or. “ad. 2” would be the reply to objection 2.

Introducing the Summa Theologiæ

I’ll be plugging my way though Thomas’s ST, so I’m planning on putting up some of my favorite quote(s) from each article of Part 1. Hopefully this will serve as sort of summary. Additionally, I’ll add brief commentary at times. This is not meant to be an exhaustive explanation, but simply an introductory taste to Thomas’s work. Much will be missing, but hopefully it will whet the intellectual appetite.

As noted above, Part 1 deals with God. But to begin his massive work, Thomas first asks about the nature of sacred doctrine or theology. So, let’s  dive into his thoughts.


Question 1: On Sacred Doctrine

Article 1: Whether, besides Philosophy, any Further Doctrine Is Required?

“It is useful that besides philosophical science, there should be other knowledge, i.e., inspired of God.” (Ia.1.1, sed contra)

“In order that the salvation of men might be brought about more fitly and more surely, it was necessary that they should be taught divine truths by divine revelation.” (Ia.1.1)


Article 2: Whether Sacred Doctrine Is a Science?

“Sacred doctrine is a science because it proceeds from principles established by the light of a higher science, namely, the science of God and the blessed.” (Ia.1.2)


Article 3: Whether Sacred Doctrine Is One Science

“Because Sacred Scripture considers things precisely under the formality of being divinely revealed, whatever ahs been divinely revealed possesses the one precise formality of the object of this science; and therefore is included under sacred doctrine as under one science.” (Ia.1.3)

“Sacred doctrine does not treat of God and creatures equally, but of God primarily, and of creatures only so far as they are referable to God as their beginning or end.” (Ia.1.3, ad. 1)


Article 4: Whether Sacred Doctrine Is a Practical Science?

“Sacred doctrine is chiefly concerned with God, whose handiwork is especially man. Therefore it is not a practical but a speculative science.” (Ia.1.4, sed contra)

“Sacred doctrine, being one, extends to things which belong to different philosophical sciences because it considers in each the same formal aspect, namely, so far as they can be known through divine revelation.” (Ia.1.4)


Article 5: Whether Sacred Doctrine Is Nobler than Other Sciences?

“Since this science is partly speculative and partly practical, it transcends all others speculative and practical.” (Ia.1.5)

“The fact that some happen to doubt about articles of faith is not due to the uncertain nature of the truths but to the weakness of human intelligence; yet the slenderest knowledge that may be obtained of the highest things is more desirable than the most certain knowledge obtained of lesser things.” (Ia.1.5, ad. 1)

“This science can in a sense depend upon the philosophical sciences, not as though it stood in need of them, but only in order to make its teaching clearer. For it accepts its principles not form other sciences, but immediately from God, by revelation. Therefore it does not depend upon other sciences as upon the higher, but to the defect of our intelligence.” (Ia.1.5, ad. 2)


Article 6: Whether This Doctrine Is the Same as Wisdom?

“He who considers absolutely the highest cause of the whole universe, namely God, is most of all called wise. Hence wisdom is said to be the knowledge of divine things.” (Ia.1.6)

“Sacred doctrine derives its principles not from any human knowledge, but form the divine knowledge, through which, as through the highest wisdom, all our knowledge is set in order.” (Ia.1.6, ad. 1)


Article 7: Whether God Is the Object of this Science?

“The object of the science is that of which it principally treats. But in this science, the treatment is mainly about God; for it is called theology, as treating of God. Therefore God is the object of this science.” (Ia1.7 sed contra)

“In sacred science, all things are treated of under the aspect of God: either because they are God Himself or because they refer to God as their beginning and end.” (Ia.1.7)

“Of all these things, in truth, we treat in this science, but so far as they have reference to God.” (Ia.1.7)


Article 8: Whether Sacred Doctrine Is a Matter of Argument?

“Since therefore grace does not destroy nature but perfects it, natural reason should minister to faith as the natural bent of the will ministers to charity.” (Ia.1.7, ad. 2)


Article 9: Whether Holy Scripture Should Use Metaphors?

“It is befitting Holy Writ to put forward divine and spiritual truths by means of comparisons with material things.” (Ia.1.9) 

“Similitudes drawn from things farthest away from God form within us a truer estimate that God is above whatsoever we may say or think of Him.” (Ia.1.9, ad. 3)


Article 10: Whether in Holy Scripture a Word May Have Several Senses?

“The author of Holy Writ is God, in who power it is to signify His meaning, not by words only (as man also can do), but also by things themselves.” (Ia.1.10)