The Summa Theologica is divided into three parts, and each of these three parts contains numerous subdivisions. Part 1 deals primarily with God and comprises discussions of 119 questions concerning the existence and nature of God, the Creation, angels, the work of the six days of Creation, the essence and nature of man, and divine government. Part 2 deals with man and includes discussions of 303 questions concerning the purpose of man, habits, types of law, vices and virtues, prudence and justice, fortitude and temperance, graces, and the religious versus the secular life. Part 3 deals with Christ and comprises discussions of 90 questions concerning the Incarnation, the Sacraments, and the Resurrection. Some editions of the Summa Theologica include a Supplement comprising discussions of an additional 99 questions concerning a wide variety of loosely related issues such as excommunication, indulgences, confession, marriage, purgatory, and the relations of the saints toward the damned. Scholars believe that Rainaldo da Piperno, a friend of Aquinas, probably gathered the material in this supplement from a work that Aquinas had completed before he began working on the Summa Theologica.
The Summa Theologica, as its title indicates, is a “theological summary.” It seeks to describe the relationship between God and man and to explain how man’s reconciliation with the Divine is made possible at all through Christ. To this end, Aquinas cites proofs for the existence of God and outlines the activities and nature of God. Approximately one-half of the Summa Theologica then examines the nature and purpose of man. Finally, Aquinas devotes his attention to the nature of Christ and the role of the Sacraments in effecting a bridge between God and man. Within these broad topical boundaries, though, Aquinas examines the nature of God and man in exquisite detail. His examination includes questions of how angels act on bodies, the union of body and soul, the cause and remedies of anger, cursing, and the comparison of one sin with another. Aquinas is attempting to offer a truly universal and rational view of all existence.
Adopting Aristotelian principles and concepts, Aquinas attempts to explain the origin, operation, and purpose of the entire universe and the role that everything in the universe plays in the attainment of that purpose. Aquinas never doubts the truth of the tenets of his faith. Rather, he employs techniques of argument that he learned in the disputatios to state, defend, and elaborate those tenets. The grandiose scope of the Summa Theologica derives from Aquinas’s belief that a very significant portion of theology can be expressed and codified in a comprehensive and rational system.
Aquinas writes not only as a philosopher who is intellectually interested in the pursuit of truth, he writes primarily as a Catholic who is convinced that the salvation of humanity itself is at stake. This conviction propels him toward a rational exegesis of topics the truth of which is ultimately derived and founded on divine revelation. When a specific topic so allows, Aquinas uses philosophical concepts and vocabulary to examine that topic. The primary topics admitting of such philosophical examination are the existence of God, the nature and limits of human knowledge, and the purpose of man. For most other topics, Aquinas articulates a decidedly Catholic position on issues of Christian interest, such as the Holy Trinity, original sin, and the like.
At first glance, it would seem astonishing and even counterintuitive that Aquinas reframes much of Catholic theology in terms of Aristotle’s pre-Christian philosophy. The pursuit of philosophy traditionally requires one to enter into debates with an open mind and to identify and re-examine one’s own core assumptions about a given issue, yet Aquinas enlists Aristotle not for his aid in the unbiased critical examination of the tenets of Catholic belief but rather for the explication and defense of those tenets. At the same time, though, Aquinas’s enlistment of Aristotle reveals Aquinas to be a remarkably fair, open minded, and indeed tolerant medieval thinker. He apparently believes that the fruits of the exercise of reason are not necessarily corrupt if the thinker is a non-Christian. This suggests that Aquinas believes that every human being, regardless of his or her beliefs, shares in humanity through the possession and use of reason. In this, Aquinas again reveals his indebtedness and allegiance to Aristotle, who had maintained that reason is the essential quality of humanity: it is that without which man cannot be man.
An indefatigable student, teacher, and writer, St. Thomas Aquinas was the greatest Christian theologian of the Middle Ages. He was born at Roccasecca, Italy, as the youngest son of Count Landolfo of Aquino and Countess Teodora of Teano. At age five, he began his studies at the Benedictine monastery in Monte Cassino. From there, he went on to study at the University of Naples and, over the objections of his family, became a Dominican friar in 1244. He continued his studies in philosophy and theology at Paris and then, from 1248 to 1252, at Cologne with Albert the Great. After further study and teaching at the University of Paris, he returned to Italy in 1259 and spent nearly ten years teaching and working at Dominican monasteries near Rome.
Back at the University of Paris in 1268, he became embroiled in arguments with clerics and theologians who opposed his philosophical positions. He returned to Italy in 1272 and taught for one year at the University of Naples before declining health forced him to quit teaching in 1273. While en route to a church council in Lyon, he fell gravely ill and died not far from the town of his birth early in 1274. He was declared a saint by Pope John XXII in 1323, pronounced the “Angelic Doctor” by Pope Pius V in 1567, and named Patron of Catholic Schools by Pope Leo XIII in 1879.
Aquinas was a prolific writer. His most extensive work is the Summa Theologica, which he probably wrote between 1265 and 1272 but left unfinished. This imposing set of tomes, which comprises thousands of pages of tightly-reasoned responses to an astonishing range of questions about church theology and doctrine, is not only the crown jewel of Scholasticism, that is, of medieval theology and philosophy, but one of the crown jewels of Western culture. His Summa contra Gentiles is remarkable as an attempt to demonstrate to nonbelievers the reasonableness of the Christian faith. In addition to these two most famous works, Aquinas also wrote commentaries on numerous treatises by Aristotle; various Bible commentaries; records of theological and philosophical disputes; and sundry treatises, letters, and notes. This prodigious output is especially impressive because Aquinas achieved it all within the span of about twenty years.
Aquinas lived during an age when the Catholic Church was the overwhelmingly dominant wielder of political and religious power in most of Europe. The Protestant Reformation, which established a rival alternative to the Catholic Church, was still some 250 years off when Aquinas was alive. Church and state were not separated and, in fact, were largely identical. There were no European nations in the modern sense of fully sovereign countries that determine their own economic, political, and social agendas.
Clerics, who were usually the only people who could read and write, possessed a monopoly on the world of learning. Education was necessarily Catholic learning and took place almost exclusively in monasteries. Very few universities existed, and most of these were institutions for the training of future clerics. For six years, candidates for a bachelor’s degree studied the seven liberal arts: geometry, grammar, logic, rhetoric, astronomy, music theory, and arithmetic. After completing this course of study, students could continue studying law, medicine, or theology for up to another twelve years in pursuit of a master’s degree or doctorate degree. Theology was the most difficult and prestigious field.
One of the distinctive features of universities in Aquinas’s day was the so-called scholastic method, which was embodied in the disputatio. The disputatio was a public debate among scholars on a particular topic or question and took place according to a strict procedural format. First, a teacher posed a previously announced question to an advanced student. This student then took a position with respect to the topic in question. Other teachers and students subsequently countered the advanced student’s responses with objections, which the advanced student then attempted to rebut. On a day soon afterward, the teacher summarized the various arguments for and against the debated question and rendered his own decision in the determinatio. This culture of spirited public debate led to the development of refined techniques of argumentation and rhetoric. Trained in this arena of intellectual jousting, Aquinas proved himself to be one of its foremost practitioners. The structure and topics of the Summa Theologica and the Summa Theologica contra Gentiles are derived directly from this tradition, and both works are essentially transcripts of debates conducted according to the rigid rules of the disputatio.
Aquinas’s greatest influence on intellectual history was his shifting attention from the works of Plato to those of Aristotle. Much of the history of Western philosophy involves the elaboration and development of ideas that are either explicit or implicit in the writings of these two great ancient Greek philosophers. Plato was particularly influential among thinkers in the church’s early history, and St. Augustine (A.D. 354–430), one of the church Fathers, derived many of his views from Plato’s writings. Plato had maintained that an unbridgeable divide separates the transient, illusory, material world that we perceive with our senses and the changeless, eternal world of transcendent reality. For Plato, the realm of eternal and perfect Forms is the only proper object of study, containing as it does the only true reality. St. Augustine saw Plato’s philosophy as profoundly congenial to Christianity in that Plato’s concept of two worlds, one eternally perfect and the other inherently imperfect, mirrors Christianity’s own postulation of two worlds, earthly and divine.
In contract, Aristotle had drifted into obscurity, if not outright oblivion, as far as the church was concerned, and it is thanks only to the efforts of Jewish and Arabic scholars that his writings survived at all until Aquinas came along. Thus, the teachings of Plato reigned supreme in church orthodoxy when Aquinas was studying. Aquinas bucked this tradition, recovering Aristotle for the West and virtually single-handedly assimilating him into Catholic orthodoxy.
Aquinas’s views are of more than merely philosophical interest, as they are official Catholic doctrine and thus represent a living set of traditions and beliefs. The Roman Catholic Church is one of the world’s most ancient, enduring, and powerful institutions, spanning nearly two thousand years and claiming some one billion adherents all over the globe. In 1879, Pope Leo XIII declared Aquinas’s teachings to be official church doctrine, cementing Aquinas’s status as one of the most influential philosophers and theologians ever. The question of whether Aquinas’s writings represent the achievement of human reason or the products of divine inspiration has been the subject of fierce debate, and one’s answer to that question is likely to depend on whether one accepts church teachings in the first place. Within the church, it is safe to say that Aquinas’s significance is inescapable.