Thomas Aquinas held that revelation was essential for grasping truth of faith but he relied on reason to understand the world that God created. Mindful of this division, Thomas warned against dogmatic interpretations in areas of faith that might have to be abandoned if subsequent natural evidence falsified them. Convinced that Aristotle's (384–322 B.C.E.) natural philosophy provided the most accurate interpretation of cosmic operations, Thomas refused to Christianize natural philosophy and, to the greatest extent possible, he applied reason to both science and theology.

Life and works

Thomas Aquinas was born near Monte Cassino, Italy, around 1225. He was the youngest of nine children. After elementary education in the abbey of Monte Cassino, Thomas was sent to Naples in 1239, where he studied at the University of Naples. In 1244, while still at Naples, Thomas entered the Dominican order, contrary to the wishes of his family. From 1245 to 1252, Thomas studied at Paris and then Cologne. At Cologne, and perhaps at Paris, Thomas's teacher was Albert the Great (Albertus Magnus) (c. 1206–1280), one of the great scientists and natural philosophers of the Middle Ages and a thorough student of Aristotle's writings. After training as a theologian, Thomas became a professor of theology at the University of Paris (1256–1259). He spent the years between 1259 and 1268 in Italy serving different popes at their papal courts. During 1269 to 1272, Thomas returned to another professorship at the University of Paris, after which he returned to Naples, where his health began to fail. Thomas died in 1274 while on his way to the second Council of Lyons.

Thomas was a prolific author who left approximately fifty works that have been thus far identified. He wrote on numerous topics, the most significant of which are his theological treatises, especially his famous Summa of Theology (Summa theologiae), commentaries on books of the Bible, and commentaries on various works of Aristotle, especially those on natural philosophy, which include Aristotle's Physics, On the Heavens, On Generation and Corruption, Meteorology, and On the Soul. In addition, Thomas composed sermons, letters, and replies to queries.

Thomas on the relationship of faith and reason

Issues of science and religion in the Middle Ages involve the relationship between natural philosophy and religion. By the time Thomas began writing, Aristotle's works on logic and natural philosophy had been adopted as the basic curriculum in faculties of arts of medieval universities. Because Aristotle's natural philosophy raised issues that were directly relevant to theology and the Catholic faith, it was inevitable that Thomas, who was both a theologian and a natural philosopher, would have to confront those issues in his works on theology and natural philosophy.

When Thomas dealt with issues of science and religion, he was guided by his overall view of the relationship between faith and reason. Thomas emphasized the importance and power of reason, but insisted that it was inadequate to gain knowledge of unseen things, such as God, for which faith and divine revelation are essential. For knowledge of the physical cosmos and its regular operations, however, reason—embodied in the works of Aristotle—was Thomas's instrument for understanding those operations. But reason was also an instrument for the study of theology. In the very first question of his Summa of Theology, Thomas asked whether theology is a science and replied affirmatively. He is usually regarded as the scholar who gave credence to the claim that theology is a science, a claim that was widely assumed in the late Middle Ages.

Two principles derived from the early Christian leader Augustine of Hippo (354–430 C.E.) and expressed in the Summa of Theology, guided Thomas in his explanations of natural phenomena. He insisted: (1) that the truths of Scripture must be held inviolate, but that (2) no passage in Scripture should be interpreted rigidly and dogmatically because it might later be proved false by convincing arguments, thus leading to a loss of credibility that would inhibit nonbelievers from adopting the faith.

Thomas and Aristotle

Although Aristotle's natural philosophy formed the basic curriculum in the arts faculties of medieval universities, those aspects of his work that conflicted with basic Christian beliefs evoked opposition through most of the thirteenth century. In the 1260s, and 1270s, when Thomas was writing, the opposition was led by the Franciscan theologian Bonaventure (1221–1271), whose neoconservative Augustinian colleagues eventually prevailed upon the bishop of Paris to condemn certain of Aristotle's articles deemed offensive to the faith; thirteen articles were condemned in 1270 and 219 articles were condemned in 1277, three years after the death of Thomas. Since Thomas was a supporter of Aristotle's philosophy, as were many Dominicans, some of the hostility was plainly directed against him and his colleagues. It was not until 1325, two years after the canonization of Thomas Aquinas, that the bishop of Paris, Stephen Bourret, revoked the condemnation of all articles condemned in 1277 that were directed against the teachings of Thomas.

The most significant idea condemned in 1277 was Aristotle's claim for the eternity of the world, which was denounced at least twenty-seven times in a variety of contexts. In a treatise he titled On the Eternity of the World, Thomas neither rejected nor accepted the eternity of the world. By absolute power, God could have created a world that was coeternal with God. For as Thomas argued, "The statement that something was made by God and nevertheless was never without existence . . . does not involve any logical contradiction." If God wishes, God can choose not to precede any effect God decides to produce, and thus God can make the world eternal. Although God could make the world coeternal with God, an eternal world would still be a created effect, because it is wholly dependent on an immutable God, thus guaranteeing that the world cannot be coequal with God. Of the articles condemned in 1277, Article 99 was probably directed against Thomas's interpretation of the eternity of the world. Thomas's approach to the question of the world's duration proved popular and found supporters up through the Renaissance. Bonaventure and others were convinced that Aristotle had denied the personal immortality of the soul, but Thomas thought Aristotle had believed it.

Since Aristotle firmly believed that every material thing is derived from previous matter, he would have been opposed to the Christian doctrine of creation from nothing. Article 185 condemned the view that something could not be made from nothing. Indeed, the Fourth Lateran Council of 1215 had declared belief in creation from nothing to be an article of faith. On this issue, Thomas, and all Christians, were compelled to reject Aristotle's interpretation.

Thomas's conception of the physical world and its operations was basically the same as that held by Aristotle, from whom he derived it. In his commentaries on Aristotle's natural philosophy, Thomas considered the numerous problems Aristotle presented, accepting most of Aristotle's solutions, but disagreeing on some important issues. Although Thomas believed with Aristotle that the existence of void spaces was impossible, he disagreed with the absurd consequence Aristotle deduced from the assumption of motion in a vacuum, namely that because of an absence of material resistance, a body would move instantaneously in a vacuum and, as a consequence, no ratio could obtain between motions in a hypothetical void and motions in a space filled with matter. Thomas rejected these conclusions. A body falling or moving in a void space would have a definite speed and take a definite time to move successively between two distant points. This is so, argued Thomas, because any distance in a three-dimensional void has prior and posterior parts that a body must traverse to get from one point to another, which requires time. Hence there could indeed be a ratio between motions in a vacuum and motions in a plenum.

In a letter to a soldier, Thomas explained how bodies could perform actions that do not follow from the nature of their constituent elements, as, for example, the attraction of a magnet for iron. Thomas regarded such actions as occult, explaining the causes of such phenomena by the behavior of two kinds of superior agents: (1) celestial bodies, or (2) separate spiritual substances, which included celestial intelligences, angels, and even demons. A superior agent can either communicate the power to perform the action directly to an inferior body, as is the case with the magnet; or the superior agent can, by its own motion, cause the body in question to move, as, for example, the moon causes the ebb and flow of the tides.

Whatever disagreements Thomas had with Aristotle, whether doctrinal or otherwise, it is obvious that Thomas was an Aristotelian in natural philosophy. As an Aristotelian natural philosopher and a professional theologian, one may appropriately inquire how Thomas related natural philosophy and theology, the medieval equivalent of the relations between science and religion. Thomas followed in the path of his teacher, Albert the Great, and generally refrained from introducing theological ideas into his treatises on natural philosophy, whereas he did not hesitate to introduce natural philosophy to elucidate his theological discussions. As a theologian doing natural philosophy, Thomas could easily have resorted to theological appeals and arguments in his natural philosophy, but he did not think it appropriate to do so. As he explained in a reply to one of forty-three questions sent to him by the master general of the Dominican order, "I don't see what one's interpretation of the text of Aristotle has to do with the teaching of the faith." Thomas refused to Christianize Aristotle's natural philosophy and to confuse natural philosophy with theology. In this, Thomas followed the practice of most medieval theologians and natural philosophers.

See also ARISTOTLE; AUGUSTINE; CHRISTIANITY, ROMAN CATHOLIC, ISSUES IN SCIENCE AND RELIGION; CREATIO EX NIHILO; CREATION; GOD

EDWARD GRANT