The Summa Theologica of Thomas Aquinas

The Summa Theologica of Thomas Aquinas (1225–1274) is one of the most influential works in the history of Western thought. Written in the late thirteenth century, the Summa was an encyclopedic work that attempted to synthesize the whole of Christian theology with the philosophy of Aristotle, and it became the standard work of Catholic theology for centuries. The Summa is remarkable for its clarity, its logical rigor, and its breadth of learning, and it has been studied and commented on for over seven hundred years. The Summa remains a major work of Catholic theology in the modern era, and it continues to shape the intellectual and religious life of the Western world.

The standard English translation of the Summa Theologica is the Dominican Province edition (1920; rev. 1981). The modern English translation of the Summa contra Gentiles is the one of the English Dominican Fathers (1923). Étienne Gilson, “The Christian Philosophy of St Thomas Aquinas” (1956), is the standard introduction. The page below treats the structure of the Summa, the five ways, and the place of the work in the history of Western thought.

The Composition of the Summa

The Summa Theologica was begun in 1265 and was left unfinished at the death of Aquinas in 1274. The Summa was intended to be a comprehensive treatise on the whole of Christian theology, and it was planned in three parts: the first part on God, the second part on man and his moral life, and the third part on Christ and the sacraments. The Summa was written in the form of questions, with each question divided into articles, and each article following the scholastic method: objections, sed contra (the opposing argument), the body of the article, and replies to the objections.

The first part of the Summa treats of God and the creation of the world. It includes questions on the existence and nature of God, the divine attributes, the Trinity, the creation, the angels, the work of the six days, and man. The first part was completed and is one of the most impressive achievements of medieval thought, with the famous Five Ways (the five proofs of the existence of God) as a major feature.

The second part of the Summa treats of man and his moral life. It includes questions on the end of man, the human acts, the passions, the habits and virtues, the vices and sins, the law, the grace of God, and the theological and moral virtues. The second part is the longest part of the Summa and the most detailed treatment of moral theology in the history of Western thought.

The third part of the Summa treats of Christ and the sacraments. It includes questions on the incarnation, the life of Christ, the sacraments in general, baptism, confirmation, the Eucharist, penance, extreme unction, holy orders, and matrimony. The third part was left unfinished at Aquinas’s death, and a supplementary section on the purgatory, the resurrection, and the last things was added later (the Supplementum).

The Five Ways

The Five Ways of Aquinas are perhaps the most famous part of the Summa. The Five Ways are five arguments for the existence of God that Aquinas presents in the Summa (I, q. 2, a. 3). The Five Ways are:

The argument from motion: Things in the world are in motion, and motion requires a mover. There cannot be an infinite regress of movers, so there must be a first unmoved mover, which is God.
The argument from efficient causation: Things in the world are caused, and causes require prior causes. There cannot be an infinite regress of causes, so there must be a first uncaused cause, which is God.
The argument from possibility and necessity: Things in the world are possible (they can exist or not exist), and they come into being and pass out of being. If everything were merely possible, there would be a time when nothing existed. But since something exists now, there must be a necessary being, which is God.
The argument from gradation: Things in the world exhibit degrees of perfection (more or less good, true, noble, etc.). These degrees imply a maximum, which is the cause of being and goodness in all things, which is God.
The argument from governance: Things in the world act for an end, and they achieve their end through intelligent direction. The regularity of natural processes implies an intelligent governor, which is God.

The Five Ways are major contributions to the philosophy of religion and the natural theology, and they have been the subject of extensive philosophical and theological debate for centuries. The Five Ways are often cited as examples of the classical arguments for the existence of God, and they continue to be discussed and debated in the modern era.

The Synthesis of Faith and Reason

The Summa is a major work of synthesis that attempts to bring together faith and reason, theology and philosophy, revelation and natural knowledge. Aquinas argued that faith and reason are compatible, that natural reason can discover truths that are consistent with the truths of faith, and that the ultimate truth of God is accessible to both reason and faith. This synthesis was a major contribution to the development of Western thought, and it became the dominant intellectual tradition of the late medieval Church.

The synthesis of faith and reason in the Summa was based on the integration of Aristotelian philosophy with Christian theology. Aquinas accepted the basic framework of Aristotelian philosophy — the doctrine of the four causes, the doctrine of the mean, the doctrine of the soul as the form of the body, the doctrine of the unmoved mover — but he modified it in ways that were consistent with Christian doctrine. Aquinas’s synthesis was a major intellectual achievement, and it became the standard interpretation of Christian theology for centuries.

The synthesis of the Summa was not without its critics. The Augustinians criticized Aquinas’s reliance on Aristotle, and the mystics criticized his emphasis on reason. The condemnations of 1277 by the bishop of Paris condemned several Aristotelian propositions, including some that Aquinas had defended. Yet the condemnations did not stop the integration of Aristotle into Christian thought, and Aquinas’s synthesis became the dominant intellectual tradition of the late medieval Church.

The Theological Method

The theological method of the Summa is the scholastic method in its most mature form. The method is based on the systematic analysis of questions through the disputative process, with objections, sed contra, the body of the article, and replies to the objections. The method is designed to be rigorous and systematic, and it produces a work of great clarity and precision.

The scholastic method of the Summa involves several steps. First, the master states the question to be resolved. Second, the master presents the objections to the proposed answer, drawing on the authorities and the arguments of the opponents. Third, the master presents the sed contra — the strongest argument for the opposite position. Fourth, the master presents the body of the article, with the systematic presentation of the position. Fifth, the master replies to the objections, refuting the counter-arguments. This method is rigorous and systematic, and it is designed to address all the major arguments for and against a position.

The theological method of the Summa is a major contribution to the development of Western thought, and it became the standard method of theological inquiry in the medieval university. The method was applied not only to theology but also to philosophy, law, medicine, and the natural sciences, and it was a major factor in the development of the Western intellectual tradition.

The Content of the Summa

The content of the Summa is vast, and it covers virtually every aspect of Christian theology and philosophy. The Summa includes detailed discussions of the existence and nature of God, the Trinity, the creation of the world, the angels, the work of the six days, the nature of man, the soul, the human acts, the passions, the habits and virtues, the vices and sins, the law, the grace of God, the theological and moral virtues, the incarnation, the life of Christ, the sacraments, and the last things. The Summa is a comprehensive treatise on the whole of Christian theology, and it is a major work of systematic thought.

The content of the Summa is organized in a systematic way, with the questions and articles arranged in a logical order. The first part treats of God and the creation, the second part treats of man and his moral life, the third part treats of Christ and the sacraments, and the supplementary section treats of the last things. The organization of the Summa is a major contribution to the systematic theology, and it is a major example of the scholastic method in its most mature form.

The content of the Summa also includes discussions of natural philosophy, metaphysics, and ethics that are independent of the theological context. Aquinas’s discussions of the soul, the human acts, the virtues, the law, and the grace of God are major contributions to philosophy as well as to theology. The Summa is a major work of philosophy as well as a major work of theology, and it is a major source for the study of medieval philosophy.

The Influence of the Summa

The influence of the Summa is immense. The Summa became the standard textbook of Catholic theology for centuries, and it is still a major work of Catholic theology in the modern era. The Summa was widely studied in the medieval universities of Europe, and it was the subject of extensive commentary by medieval and early modern scholars. The Summa was also a major influence on the theology of the Catholic Reformation and the Protestant Reformation, and the Council of Trent (1545–1563) drew on Aquinas’s theology in its decrees and reforms.

The Summa was declared the standard theological text of the Catholic Church by Pope Leo XIII in his encyclical Aeterni Patris of 1879, and the Summa has been a major work of Catholic theology ever since. The Summa is studied in Catholic seminaries and universities around the world, and it continues to shape the theology and philosophy of the Catholic Church. The Summa is also a major work of philosophy that is studied in secular universities and philosophy departments, and it continues to shape the debates of Western philosophy.

The Summa is a major work of Catholic theology and philosophy that has had an immense influence on the intellectual tradition of the Western world. The Summa is a major subject of modern theological and philosophical study, and it is a subject of ongoing research in the modern era. The Summa is a major monument of the medieval world, and it continues to inspire and challenge theologians and philosophers in the modern era.

Sources

Principal sources used in this article:

R. W. Southern, The Making of the Middle Ages (Yale, 1953).

Further reading:

Étienne Gilson, The Christian Philosophy of St Thomas Aquinas (Random, 1956).

For a recent single-volume synthesis with full scholarly apparatus, see the relevant chapter of Barbara H. Rosenwein, A Short History of the Middle Ages (University of Toronto Press, 2014).