St. Thomas Aquinas – Intro to the Summa Theologica


Tomorrow, January 28 is the Feast Day of St. Thomas Aquinas…

In honor of the occasion, we offer an introduction to his most important work, the Summa Theologica,

This introduction was written by D.J. Kennedy, O.P. and appeared in his 1919 book, St. Thomas Aquinas and Medieval Philosophy [ Download the book in full from Google Books ]

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Overview of the Book


Question I. Sacred Doctrine. — After these few preliminary remarks, which, by the way, contain more than many a long-winded preface, as prefaces are often written, the Angelic Doctor enters into the consideration of his subject, beginning with an introductory question on Sacred Doctrine, by which term he means either revelation in general, or theology in particular.

Besides philosophy which can be known by reason, he says, revelation is also necessary for the human race, first because without revelation men could know nothing of the supernatural end to which they must tend, and secondly, without revelation even the truths concerning God which could be proved by reason, would be known only by a few, after a long time and with the admixture of many errors (Art. I, cf. Vat. Council, Const. “Dei Filius,” c.2).

What is Scholastic Theology? — The principles of revelation having been once received, the mind of man proceeds to explain them and to draw conclusions from what was revealed. From this results in man’s mind theology properly so-called, which is a science, speculative and practical, higher in dignity than the other sciences, deserving to be called wisdom, because the principles from which it proceeds are made known by revelation which manifests God as the highest cause of all things (art. 2, 3, 4, 5, 6). The object, or subject, of this science is God; all other things are treated in it only in so far as they relate to God (art. 7). Reason is used in theology not to prove the truths of faith — which are accepted on the authority of God — but to defend, explain and develop the doctrines which have been revealed (art. 8). Revelation is made known to us by the Sacred Scriptures. God, the author of the Scriptures, embraces all things in His infinite mind; and when He deigns to speak to man, if we take into account the intention of God, considering the spiritual or mystical as well as the literal sense of the words, a single text of Scripture may contain a world of meaning (art. 9, 10).

Plan of the Summa. — Having laid down these principles, St. Thomas announces the order he intends to observe in his theology. This is one of the most important features of the Summa. In ten lines of a half column, as the words are printed in the Migne edition of his works, the Angel of the Schools sketches that wonderful plan which introduced unity into all theological treatises. Under three headings he classifies all the parts of dogmatic and moral theology; not one of them can be omitted in a complete theology; it is not necessary to add another, because they embrace everything, they cover the whole field.

General Outlines. — Now, what are those three headings, those three leading ideas? “Since the principal object of sacred doctrine is to give the knowledge of God, not only as he is in Himself, but also as He is the Beginning of all things and the End of them all, especially of rational beings, we shall treat first, of God; secondly, of the tendency of the rational creature to God, and thirdly, of Christ, who as man is the way by which we tend to God.” This is the grand division, these are the general outlines of the “Summa Theologica.” God in Himself and as He is the Creator; God as the End of all things, especially of man; God as the Redeemer — these are the leading ideas under which all that pertains to theology is contained.

Subdivision; 1a Pars. — The First part, of God in himself and of God as Creator, is subdivided into three tracts. (1) Of those things which pertain to the essence of God, (2) the distinction of persons in God, i.e., on the Trinity, (3) of the procession of creatures from God; under which St. Thomas treats (1) of the production of creatures, (2) of the distinction of creatures, (3) of the preservation and government of creatures. Under the heading of the distinction, he treats of the distinction of creatures, (1) in general and (2) in particular, i.e., of good and evil, of creatures that are purely spiritual (the angels), of creatures that are purely corporeal (the material world), and of man, who is composed of body and spirit. This makes in all nine tracts in the first part: (1) On the essence of the one God. (2) On the Trinity. (3) On the creation. (4) On the distinction of things in general. (5) On the distinction of good and evil. (6) On the angels. (7) On purely corporeal creatures. (8) On Man. (9) On the preservation and government of the world.

2a Pars. — The Second part, which treats of the tendency of rational creatures to God, i.e., of God as He is the end of man, contains the moral theology of St. Thomas or his treatise on the end of man and on human acts. It is subdivided into two parts knowns as the 1a 2ae and the 2a 2ae, or the First of the Second, and the Second of the Second. The first five questions of the 2a pars are devoted to proving that man’s last end, or his beatitude, consists in the possession of God. Man attains to that end or deviates from it by human acts, of which he treats, first in general (in all but the first five questions of the prima secundae), secondly, in particular (in the whole of the 2a 2ae).

The treatise on human acts in general is divided into two parts, (1) on human acts in themselves, (2) on the principles or causes of those acts. Of the acts performed by man some are peculiar to him as man, others are common to him and the lower animals; hence St. Thomas speaks, (1) of human acts, (2) of the passions. Here I may pause to remark that in these two tracts, St. Thomas, following Aristotle, gives the most perfect description and the keenest analysis of the movements of man’s mind and heart that ever came from the pen of man.

The principles (or causes) of human acts are intrinsic or extrinsic. The intrinsic principles are the faculties of the soul and habits. The faculties of the soul were explained in the first part, in treating of the soul of man; hence in the prima secundae St. Thomas considers habits, first, in general, then, in particular, i.e., the virtues and vices, in explaining which his power of analysis is again displayed in a remarkable manner. The extrinsic principles of human acts are the devil who tempts us, and God, who instructs us by His laws and moves us by His grace. Of the temptation of the demons St. Thomas treated in the first part, when he was explaining God’s manner of governing the world. The prima secundae closes with the treatise on laws and on grace.

2a 2ae. The second part of the second treats of the virtues and vices in particular. In it St. Thomas treats first of those things which pertain to all men, no matter what may be their station in life; secondly, of those things which pertain to some men only. Things that pertain to all men are reduced by St. Thomas to seven headings: faith, hope and charity — the three theological virtues — prudence, justice, fortitude and temperance — the four cardinal or principal moral virtues. Under each title St. Thomas, in order as he himself tells us, to avoid frequent repetitions, treats not only of the virtue itself, but also of the vices opposed to it, of the commandment given to practise it, and of the gift of the Holy Ghost which corresponds to it. Under the second heading — of those things which pertain to some men only — St. Thomas treats first of the graces freely given by Almighty God, to certain individuals for the good of the Church, such as the gift of tongues, prophecy, the power to work miracles, etc. Secondly, of the active and contemplative life. Thirdly, of particular states in life, and of the duties of those who are in different stations, especially of bishops and religious.

3a Pars. — In the third part of his Summa, St. Thomas treats of our Blessed Redeemer and of the benefits which he confers upon man; hence the three tracts; first, on the Incarnation and on what our Saviour did and suffered when He was on earth; second, on the Sacraments, which were instituted by our Saviour and have their efficacy from his merits and sufferings; and the third, on the end of the world, the resurrection of our bodies, judgment, the punishment of the wicked, and the everlasting happiness of those who through the merits of Christ are brought back to the bosom of God.

These are the grand outlines of the Summa, which was the first, and which remains to this day the most perfect, scientifically arranged theology that was ever written. I have said nothing of the subdivisions under each grand heading; they bear the impress of the same all-embracing and penetrating mind which conceived the general plan. The Summa contains 38 tracts, 631 questions and about 3,000 articles, in which more than 10,000 objections are answered. Take up any one of these articles, and by referring to the beginning of the treatise you can see at a glance what place it occupies in the general plan, which embraces all that can be known of God, of man, and of their mutual relations. This scientific arrangement of questions is one of the most prominent features of the Summa, and the making out of this plan was in itself a greater benefit to theology than anything that had been done before or has been done since the time of St. Thomas. Writers who preceded St. Thomas had deserved well of religion and of the Church; they had written wisely and well, and to some of those who immediately preceded him or were contemporary with him must be given the credit of having prepared the way for the Summa by collecting the materials which he moulded into one vast synthesis; but they had not written a scientific theology. Those who came after St. Thomas have deemed it an honor and a pleasure to follow the order of the Summa. They may have added some new developments or cited some facts and definitions which came after the thirteenth century, but they have never dreamed of attempting to write a better theology. St. Thomas remains the master and the model; the nearer they approach to him, the better right they have to be considered good theologians.

It must not be supposed, however, that all the excellencies of the Summa have been enumerated when the general plan has been pointed out and a short list has been given of the principal questions treated in it. St. Thomas was not only a great architect, he was also a practical builder and he attended with the greatest diligence to every detail of the grand edifice which he constructed. Reading over his works we involuntarily exclaim: Verily Pope John XXII expressed a truth when he said that St. Thomas wrought as many miracles as he wrote articles.

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