1224-1274. The greatest philosopher and theologian of the medieval church. Born in Italy, he studied at the University of Naples and became a Dominican in 1244. Later he studied under at Paris, and also at Cologne. Most of the remainder of his life was spent as a teacher in Paris. In 1273 he had to discontinue his Summa Theologica due to ill health. He died the following year.
His thought is expressed in an enormous literary output, not only the Summa contra Gentiles (1261-64), intended as a manual of apologetics and doctrine for missionaries, and the Summa Theologica (1265-73), on which his reputation as a theologian and philosopher chiefly rests, but also in commentaries on Scripture, and on Aristotle,* and a variety of miscellaneous discussions. The Summa Theologica must be seen as a marvelous systematizing of the data of Christian revelation (as understood by Aquinas) along Aristotelian lines, impressive in the thoroughness and the success with which the program was executed. The Augustinian contrast between the certainty of the intelligible order (known through intellectual illumination) and the uncertainty (and hence/unreliability) of sense impressions was replaced by the Aristotelian contrast between “form” and “matter.” All human knowledge is regarded as being sensory in origin, and the human understanding, through abstraction, is able to build up knowledge of the forms of things. But if knowledge is sensory in origin, how may God be known? Much of Thomas's work may be considered an answer to that question.
He made a sharp distinction between “sacred doctrine” and philosophy. Sacred doctrine proceeds from the data of revelation, philosophy from data accessible to (and acceptable to) all men. It is a mistake to think of Aquinas as a Christian philosopher if by this is meant someone who elaborates answers to philosophical questions on the basis of Christian revelation. The different places assigned to philosophy and theology may be vividly illustrated by Thomas's view of creation. Philosophically the universe might be eternal. But the Christian believes from revelation that creation is an act of God.
Aquinas claimed that God's existence can be established philosophically. His famous “Five Ways” are five a posteriori arguments (some say, five variants of one basic argument) based on God's effects in the world, data open to all men. The Five Ways may be seen as an effort to fill a gap in explanation, to show that if certain contingent states of affairs exist, there must be some necessary ground for their existence. How much Thomas's arguments depend on outmoded science, whether the arguments are sound, and whether, if at least one of them is sound, the God whose existence is established is the god of Christian revelation-these are all debatable and much-debated questions.
The Five Ways provide a part of one answer to the question, How may God be known? He is knowable only by His effects. Yet not only by His effects in nature, but also by His revelation in Scripture, to the acceptance of which the Five Ways are a natural, rational preamble. Not only was Aquinas a natural theologian, he was an eminent philosopher of revelation, employing philosophical concepts in elucidating the propositions and notions of revealed truth.
Despite the elaborateness of his theological discussions, Thomas's stress was on how little God is known. God is categorically distinct from His creatures, unique, transcendent. How then can He be spoken about? Only imperfectly. Such speech is by means of analogy (God's wisdom is in some respects the same as Solomon's wisdom, in some respects different) and negation (God is not embodied, He does not exist in time) from speech about finite things. Hence the doctrine of analogy (in particular) plays a crucial role in Thomas's account of the knowledge of God.
He distinguished between faith, opinion, and knowledge. Faith, an act of the mind, is stronger than opinion. It involves a firm assent to its object. But because it lacks full comprehension (vision) it is less than knowledge. Religious faith is a species of this genus. (Aquinas knows nothing of faith as a “leap in the dark” or as “personal but not propositional.”) The disposition to have faith in divinely revealed matters is a product of God's grace.
God's sovereignty is expressed by saying that He is the “first cause” of all that is, evil (regarded by Aquinas, following Augustine, as a privation of goodness) excepted. Does this mean that God is the efficient cause of all that is? If so, what about human freedom? Aquinas is firmly Augustinian as well in his insistence on God's providential ordering of human actions, and of his foreknowledge of them. Foreknowledge does not causally necessitate actions, it makes them certain, as from God's point of view all actions take place in an “eternal present.”
In ethics Thomas's thinking stresses the purposive, end- directed character of human action. He distinguishes between moral theology (action viewed in accordance with divinely revealed law) and general ethical principles which, through an appreciation of natural law, are accessible to all. In his account of human action Aquinas stresses voluntariness (not freedom in the sense of indeterminacy) as a necessary condition of fully human (i.e., responsible) action.
The influence of Aquinas on the Christian Church has been enormous, although the acclaim his work received was not instantaneous (several of his teachings were condemned as errors after his death, a decision later reversed). The strong modern revival of his influence and of “Thomism” dates from the publication of the encyclical Aeterni Patris by Leo XIII in 1879, praising and endorsing Thomism and giving it an “official” (though not exclusive) place in the thinking of the Roman Catholic Church.
The influence of Aquinas on Protestantism must not be minimized. Though what were regarded as his (and others') speculative excesses and unbiblical errors were repudiated at the Reformation, the Augustinian character of much of his theology was gratefully recognized. Post-Tridentine Protestant systematic theologians such as F. Turretin were obviously indebted to him both methodologically and for detailed arguments on points held in common. Similarly, Thomas's view of apologetics-the sharp distinction between “nature” (accessible to all) and “grace” (derived from revelation, but perfecting, not repudiating, the conclusions of reason)-has been a recurring theme in Protestantism, which the strong post-Kantian tradition, culminating in the work of
Opera omnia (Parma ed., 25 vols., 1852-72); A. Pegis (ed.), Basic Writings (1945); G.K. Chesterton,