Who is Thomas Aquinas?

St. Thomas Aquinas (1224/5–1274) is a Catholic theologian (philosopher?*) and Doctor of the Catholic Church. In recognition of his saintly life, he was canonized a saint of the Catholic Church on July 18, 1323. He has received the honorific titles Angelic Doctor, Universal Doctor, and Doctor of Humanity and is regarded as one of the most influential and authoritative theologians in Church history as well as one of the most important philosophers in the history of philosophy. Catalyzed by the publication of Pope Leo XIII's encyclical letter Aeterni Patris (1879), there has been an enormous and long-lasting renewal in interest in and study of St. Thomas's life and works both within the Catholic Church and the secular academy.

Outline of His Life

Born at the castle of Roccasecca in the County of Aquino, Thomas was sent as a child to be educated by the Benedictine monks of Monte Cassino, where it was hoped he would eventually exercise an important role over the political landscape of central Italy. As a teenager, Thomas went to the newly founded secular University of Naples, where he studied the liberal arts (grammar, logic, rhetoric arithmetic, geometry, astronomy, and music); was introduced to the scientific works of the great ancient Greek philosopher, Aristotle, which were just becoming available in the Latin West; and encountered the newly founded Order of Preachers [OP] (=Dominican Order). His family objected to him joining this new religious order of friars, who, as mendicants (beggars), renounced all property and did not settle in a single place like the old monastic orders. After a long imprisonment by his family, Aquinas was released to continue his life with the Dominicans.

He was sent to Paris, the center of European intellectual life, where he met his future mentor, the German Dominican and renowned natural scientist and theologian, Albert the Great (c. 1200–1280). Albert took Thomas with him to Cologne, where Thomas studied Aristotle's scientific works as well as Neoplatonic metaphysical works with Albert while also undertaking his formal bachelor studies by lecturing on the Bible.

After completing his studies in Cologne, St. Thomas returned to the University of Paris, where he began studying to become a Master in Theology (the highest degree attainable in theology), a course of study, which required him to lecture on the standard collection of patristic sources at the time, the Sentences of Peter Lombard. Having attain the rank of Master of Theology, he took up the Dominican Chair in theology at the University of Paris. His career as theologian would take him away from Paris to Rome and the Papal States (central Italy), back to Paris for another tenure as Dominican Chair in theology, and finally back to Naples. He died on his way to the Second Council of Lyon in 1274.

It is for good reason that St. Thomas is generally recognized by Christian theologians as the preeminent authority on nearly every theological topic and by philosophers at large as one of the greatest minds in history. Even if he didn't say all there is to say by any measure and was wrong about some things, the breadth, depth, accessibility, and internal coherence of his theological and philosophical output is simply incomparable. 

One of the perennial mysteries in studying St. Thomas's life and works is the sheer size of his works. Somehow in a brief period of about twenty years he produced a greater quantity of high quality, densely written philosophical and theological material than nearly anyone will have the time to read—let alone study—in a full lifetime.

For a full biography of St. Thomas, see the Biography section under Books about Aquinas.

Outline of His Works

Commentaries on Aristotle, Boethius, Dionysius, Liber de Causis

As the great twentieth-century Thomist, Ralph McInerny, has noted, if all St. Thomas did was write his commentaries on Aristotle, he would have won lasting fame as a great philosopher. Despite his ignorance of Greek, aided by exemplary, literal translations of Aristotle's works into Latin, a photographic memory of Aristotle's major works, and outstanding genius, St. Thomas remains to this day arguably the best guide to understanding Aristotle's major works. Yet, his commentaries on Aristotle are far from his only work. Indeed, they were not even his only commentaries.

He also commented on two metaphysical-theological treatises by the late Christian statesman-philosopher, Boethius (c. 480–524): the De trinitate (Super Boetium De Trinitate: where we find some of Aquinas's best discussions of faith and reason and the division of the academic disciplines) and De hebdomadibus (Expositio libri De ebdomadibus: where we find some of Aquinas's fundamental metaphysical principles worked out). 

Besides his commentaries on Boethius, he also wrote a massive commentary on the work of the anonymous, Christian Neoplatonist, Pseudo-Dionysius's Divine Names (Super De divinis nominibus), where we find his principles for rational discourse about the divine nature explained. Like all his contemporaries, St. Thomas took the author of the Divine Names to be the disciple of the Apostle Paul, converted in Athens (Acts 17:32–34). As such, Aquinas accords this author more authority than anyone else. 

Finally, St. Thomas also wrote a commentary on the anonymous (possibly Muslim or Jewish) Neoplatonic treatise, The Book of Causes (Super librum De causis). Prior to Aquinas, most Latins thought that this treatise on intellectual substances (roughly God and the angels) was written by Aristotle, but Aquinas showed that it was written by a later Neoplatonist, who was paraphrasing parts of Proclus. Despite disagreeing with the author of this work on several matters, St. Thomas incorporated many of its insights into his work.

His Day Job: Scriptural Commentaries and Disputed Questions

St. Thomas's primary task as Master of Theology was to comment on the sacred scriptures and to hold regular disputations in which theological matters would be debated and magisterially settled in a public setting. Thus, we have from him a series of commentaries on scripture—the most noteworthy of which are his commentaries on the letters of St. Paul and on the Gospel of John—as well as a series of "Disputed Questions" (on truth, on evil, on the power of God, on virtues, on the soul, etc.), edited by him into written from from his public disputations. Some of St. Thomas's most nuanced philosophical discussions are found within his commentaries on scripture and his disputed questions.

Apart from his regular work commenting on scripture and overseeing theological disputations, he was also personally commissioned by the pope to collect quotations and paraphrases of the Church Fathers into a line-by-line commentary on the four Gospels. This work, which, again, by itself, would have secured St. Thomas a place among the preeminent theologians in Church history, is known as the Catena Aurea (Golden Chain).

Theological Syntheses

As already noted, to receive the title, Master of Theology, St. Thomas had to lecture on the whole of the standard theological textbook of the day, the Sentences of Peter Lombard. This book, which mainly consists in quotations of the Church Fathers with brief commentary, covered every major theological topic, and Aquinas's youthful commentary on it (Scriptum super Sententiis) amounts to an enormous, finely argued examination of the whole range of theological and philosophical topics studied in the thirteenth century. 

Sometime during his Italian sojourn, St. Thomas began a second commentary on the Sentences of Peter Lombard (Lectura Romana in primum Sententiarum Petri Lombardi), but soon abandoned the project—presumably judging that Lombard's text was too poorly organized. He, thus, went about writing his own brand new textbook for beginner theologians, the Summa theologiae (=Summa theologica), commonly recognized as his most important work. This massive textbook, which he died before completing, is divided into three parts: 

Apart from the completed commentary on the Sentences and the Summa theologiae, St. Thomas has a third major theological work, covering all areas of theology. This is his Summa contra Gentiles, a shorter and more philosophically oriented textbook commissioned for missionaries needing to know how to answer the arguments of Islamic, Jewish, and pagan philosophers against the Christian faith. 

Although it is often included among his short works (opuscula), not his major theological syntheses, St. Thomas's short and unfinished catechetical summation of the faith, the Compendium theologiae, contains many insights not found in his outside works or not expressed in the same way.

Quodlibetal Questions

As a Master of Theology at Paris, Aquinas had the option of hosting, twice yearly, a set of open-ended debates or—to put it in terms of a modern analogue—Q&A sessions. These were called "quodlibetal questions" (literally "whatever questions"). During them, anyone from the public could ask St. Thomas whatever question they wanted, however obscure or difficult, and he had to answer it. In Aquinas's quodlibetal questions, therefore, we find his answers to some of the most difficult and bizarre questions, and we see him making fine theological or philosophical distinctions found nowhere else in his writings.

Other Works

Apart from the works described above, we have several other forms of works by Aquinas: sermons, private letters (which sometimes take the form of short philosophical treatises), small philosophical works (such as his introduction to metaphysics, On Being and Essence [De ente et essentia] and his introduction to natural philosophy, On the Principles of Nature [De principiis naturae]), commentaries on various prayers, original or edited prayers and liturgies, and polemical treatises. 

Controversies

Great Parisian Controversies

In Paris, Thomas was beset by two great controversies: the mendicant controversy and the Averroist controversy. 

The Mendicant Controversy

During his first stay, the newly founded mendicant (=beggar) orders—the Order of Preachers [OP] (=Dominicans) (of which Aquinas was a member) and the Order of Friars Minor [OFM] (=Franciscans)—armed with novel papal privileges at the University of Paris, were under attack physically and intellectually by the diocesan clergy. These diocesan clergy saw the mendicant orders as stealing chairs at their own diocesan university (the University of Paris) and usurping the right order of society by offering spiritual goods to the laity outside the regular diocesan hierarchy. Moreover, monks by nature belong in one place—a monastery—not wandering about as itenerant preachers and fundraisers. Against this attack, St. Thomas and his older contemporary, St. Bonaventure, OFM (1221–1274), defended the papal privileges of the mendicant orders and elaborated the special missions of a mendicant friar in contradistinction from those of the more familiar monk.

The Averroist Controversy

The second great controversy Thomas encountered in Paris arose just before his second tenure as Dominican Chair in theology. This controversy concerned to what extent Aristotle's scientific works could be received and studied in a Catholic university. Aristotle was an ancient Greek pagan and his scientific works were often accompanied by the commentaries of the twelfth-century Islamic philosopher, Averroes (Ibn Rushd) (1126–1198). But Averroes denied many Christian doctrines and argued that Aristotle denied these doctrines as well—the creation of the world from nothing, the beginning of the world in time, and the survival of the individual human soul after death. Moreover, he viewed the sacred texts of Islam as for the ignorant multitudes, incapable of philosophy and, therefore, dependent on myths and fables for right order. Some in the arts faculty at the University of Paris seemed to view the Christian scriptures in a similar way. Thus, although Aristotle had by the late-thirteenth century become an accepted part of the university curriculum, many theologians began to see the study of Averroes and Aristotle as dangerous to the Catholic faith. St. Thomas sought a middle way (via media) between the theologians who sought to eradicate the study of Aristotle's scientific works, on the one hand, and the masters in the Arts Faculty at the University of Paris, who generally agreed with Averroes's interpretation of Aristotle, on the other. As St. Thomas tried to make clear through extensive commentaries on Aristotle's works as well as a handful of polemical treatises, Averroes had not been entirely correct in his interpretation of Aristotle, and Aristotle's scientific works were actually far more consistent with the faith and helpful for expounding it than either the theologians or the arts masters had previously realized.

Philosophers and Theologians Who Influenced St. Thomas

This chronology is not a scientific or anywhere near an exhaustive list of authors writing before Aquinas who influenced his work. The dates have not been collected in a scholarly fashion, but from here and there on the internet, including Wikipedia or other reference sources. I have even simplified some of the dates for the sake of making the page more readable. This chronology is merely meant merely to serve as a helpful devise for visualizing and becoming familiar with some of the prominent names associated with Aquinas as his sources and their relative times in history. I have also indicated their religious tradition and primary language (see key below) to give a visual illustration of the great diversity of sources from which Aquinas drew inspiration.

Plato (428/23–348 BC)

Aristotle (384–322 BC)

Marcus Tullius Cicero (106–43 BC)

Alexander of Aphrodisias (fl. 200)

Porphyry (c. 234 – c. 305)

Ambrose of Milan (c. 339–397)†

John Chrysostom (d. 407)†

Jerome (c. 342/47–420)†

Augustine of Hippo (354–430)†

Pope Leo I (the Great) (c. 400–461)†

Proclus (412–485)

Ammonius Hermiae (c. 435–517/26)

Boethius (480–524)†

Benedict of Nursia, OSB (480–547)

Priscian Caesariensis (fl. c. 500)

Simplicius of Cilicia (480–560)

Pseudo-Dionysius the Areopagite (late-5th–early-6th cent.?)†

Pope Gregory I (the Great) (540–604)†

Isidore of Seville (c. 560–636)†

Venerable Bede, OSB (d. 735)†

John Damascene (c. 675–749)†

John Scottus Eriugena (c. 800 – c. 877)†

Alfarabi (al-Farabi) (c. 870– c. 950)¶

Avicenna (Ibn Sina) (980–1037)¶

Avicebron (Ibn Gabirol) (c. 1021–1050/70)••

Anselm of Canterbury, OSB (1033/34–1109)†

Algazel (Al-Ghazali) (1057–1111)••

Peter Abelard, OSB (c. 1079–1142)†

Gilbert of Poitiers (Gilbert de la Porrée) (1085–1154)†

Bernard of Clairvaux, O. Cist. (1090–1153)†

Peter Lombard (c. 1096–1160)†

Hugh of St. Victor (c. 1096–1141)†

Gratian (c. 1100–mid-1100s)†

Richard of St. Victor (d. 1173)†

Dominicus Gundissalinus (1115–1190)†

Averroes (Ibn Rushd) (1126–1198)

Moses Maimonides (Moses ben Maimon; the Rambam) (1138–1204)••

William of Auxerre (1140/50--1231)†

Philip the Chancellor (1160--1236)†

Robert Grosseteste (c. 1168–1253)†

Dominic de Guzmán, OP (1170–1221)†

William of Auvergne (1180/90–1249)†

Alexander of Hales, OFM (c. 1185–1245)†

Hugh of Saint-Cher, OP (1200–1263)†

Peter of Ireland (Petrus de Ibernia) (fl. mid-thirteenth century)†

William of Sherwood (c. 1200– c. 1272)†

Albert the Great, OP (Albertus Teutonicus / Albertus Magnus) (c. 1200–1280)†

Peter of Spain, OP (?) (fl. mid-13th cent.)†

Bonaventure of Bagnoregio, OFM (Giovanni di Fidanza) (1221–1274)†


To show the diversity of the influences on Aquinas, I have color coded the names above by their principal language: Greek, Arabic, Latin. † = Christian; •• = Jewish; ¶ = Muslim