Thomas Aquinas and the Summa Theologica: Faith Meets Reason

The Summa Theologica (also called the Summa Theologiae) is the great unfinished work of the Italian Dominican friar Thomas Aquinas, begun around 1265 and abandoned in December 1273. Written as a textbook for students of theology, it set out the whole of Christian doctrine in a strict question-and-answer form and used the newly recovered philosophy of Aristotle to explain it. The Summa became the foundation of the school of thought known as Thomism and remains one of the most influential books in the history of Western philosophy.

Background: Aristotle comes to the West

For most of the early Middle Ages, Latin Christians knew only a few of Aristotle’s logical works. In the twelfth and thirteenth centuries that changed. Translators in Spain, Sicily and elsewhere turned his writings on nature, the soul, ethics and metaphysics into Latin, often together with the commentaries of Muslim and Jewish thinkers such as Averroes (Ibn Rushd) and Maimonides.

The new texts arrived at a time when universities were taking shape. At the University of Paris, masters debated how far a pagan philosopher’s account of the world could be reconciled with Christian belief. Church authorities at times restricted the teaching of Aristotle’s natural philosophy, but by the 1250s his works were standard reading in the Paris arts faculty.

This was the setting of scholasticism, the method of medieval schools that tested ideas by careful definition, the citing of authorities and formal debate. The friars of the new mendicant orders, especially the Dominicans and Franciscans, became leading scholastic teachers.

Thomas Aquinas: life and career

Thomas was born around 1225 at Roccasecca, between Rome and Naples, into a noble family related to the counts of Aquino. As a boy he was placed in the Benedictine abbey of Monte Cassino, and he later studied the liberal arts at the University of Naples, where he first met Aristotle’s works and the Dominican friars.

In 1244 he joined the Dominicans, against his family’s wishes. His brothers seized him on the road and held him at the family’s castles for about a year before he was allowed to return to the order. He then studied in Paris and in Cologne under Albert the Great, one of the most learned men of the age.

Thomas became a master of theology at Paris in 1256. Over the following years he taught in Paris, at several Dominican houses in Italy, including Orvieto and the convent of Santa Sabina in Rome, and finally in Naples. He wrote at an extraordinary pace: commentaries on Scripture and on Aristotle, disputed questions, and the Summa contra Gentiles, a defence of Christian belief finished in the mid-1260s.

Writing the Summa

Thomas began the Summa Theologica around 1265, probably while running a Dominican house of studies at Santa Sabina in Rome. In its prologue he explained that existing textbooks confused beginners with useless questions, repetition and a poor order of topics. He wanted a clear, orderly guide for students.

The work has three parts. The First Part, largely written in Italy by about 1268, deals with God, the Trinity, creation, angels and human nature. The Second Part, written mostly during his second period in Paris from 1268 to 1272, deals with human action, happiness, law, grace and the virtues; it is so long that it is divided into two sections. The Third Part, begun around 1272 at the end of his Paris years or soon after his move to Naples, deals with Christ and the sacraments.

On or around 6 December 1273, while celebrating Mass in Naples, Thomas had an experience that made him stop writing. According to testimony collected for his canonisation, he told his companion Reginald of Piperno that everything he had written now seemed to him like straw compared with what he had seen. He left the Third Part unfinished in the middle of the treatment of penance.

How the Summa works

The Summa is divided into questions, and each question into articles. Every article follows the same pattern. It asks a precise question, such as whether God exists, and first lists objections against the answer Thomas will give. A brief contrary statement, usually from Scripture or a respected authority, follows. Thomas then gives his own reasoned answer and finally replies to each objection in turn.

This format reflected the disputations held in medieval universities. It forced the author to state opposing views fairly before answering them, and it lets readers find a single topic easily. Aristotle appears simply as “the Philosopher”, and Averroes as “the Commentator”.

Thomas’s central conviction was that faith and reason cannot truly contradict each other, because both come from God. Reason can show some truths, such as the existence of God, while other truths, such as the Trinity, are known only through revelation. Philosophy, in this view, is a servant of theology rather than a rival.

Key ideas

The best-known passage is the Five Ways (in Latin, quinque viae), five short arguments for the existence of God in the First Part. They reason from the existence of motion, causation, contingent things, degrees of perfection and the ordered behaviour of natural things to a first cause that, Thomas says, all people call God.

In the Second Part, Thomas develops a theory of law. He distinguishes eternal law, natural law, human law and divine law, and argues that human laws are legitimate only insofar as they agree with reason and the common good. His account of natural law shaped later Catholic moral teaching and the European tradition of legal and political thought.

The Summa also sets out conditions for a just war: lawful authority, a just cause and right intention. It discusses the virtues at length, combining Aristotle’s ethics with Christian ideas of faith, hope and charity.

Controversy and reception

Thomas’s use of Aristotle was not universally welcomed. At Paris he argued both against conservative theologians suspicious of philosophy and against “radical Aristotelians” such as Siger of Brabant, whose reading of Averroes seemed to deny individual immortality. In 1270 Thomas wrote a treatise against their view.

Thomas died on 7 March 1274 at the Cistercian abbey of Fossanova, south of Rome, while travelling to the Second Council of Lyon. In 1277 the Bishop of Paris, Étienne Tempier, condemned 219 propositions, a few of which touched positions held by Thomas, and the Archbishop of Canterbury issued a similar condemnation at Oxford. The Dominicans nevertheless defended his teaching, and Pope John XXII canonised him in 1323.

Later popes raised his standing further. Pius V declared him a Doctor of the Church in 1567, and Leo XIII’s encyclical Aeterni Patris (1879) urged Catholic schools to make his philosophy the basis of their teaching.

Myths and facts

Myth: the Summa was placed on the altar beside the Bible at the Council of Trent. This story is often repeated, but it rests on later reports rather than clear evidence from the council itself. What is certain is that Trent drew heavily on Thomas’s theology.

Myth: Aquinas tried to prove all of Christianity by reason. In fact he held that the central mysteries of faith go beyond reason and can only be accepted through revelation, even if reason can answer objections to them.

Fact: the work is unfinished. The Supplement found in many editions was compiled after his death, largely from his early commentary on the Sentences of Peter Lombard.

Timeline

• c. 1225: Thomas is born at Roccasecca in the Kingdom of Sicily.
• 1244: He joins the Dominican order and is detained by his family for about a year.
• 1256: He becomes a master of theology at the University of Paris.
• c. 1265: He begins the Summa Theologica, probably in Rome.
• 1268–1272: Second period of teaching in Paris; most of the Second Part is written.
• 6 December 1273: After an experience at Mass in Naples, he stops writing.
• 7 March 1274: Thomas dies at Fossanova Abbey.
• 1323: Pope John XXII canonises him.
• 1879: Leo XIII’s encyclical Aeterni Patris promotes his philosophy.

Legacy

The Summa gave the medieval West a model of how a vast body of knowledge could be ordered by argument. Dante placed Thomas among the wise spirits in the heaven of the Sun in his Divine Comedy, and Thomist ideas spread through universities across Europe.

Its influence reaches well beyond the Catholic Church. Philosophers still discuss the Five Ways, historians of law trace natural law theory through Thomas, and modern debates on just war and human dignity often begin with his definitions.

Why it matters

The Summa Theologica was the most ambitious attempt of the Middle Ages to show that faith and reason belong together. By joining Aristotle’s philosophy to Christian theology, Thomas Aquinas shaped Catholic teaching for centuries and left a lasting mark on Western ethics, law and philosophy.