Ethica Thomistica. A summary of the thought of St. Thomas AquinasThomistic Philosophy Page
Summa TheologicaSumma Contra Gentiles"The Five Ways"
Aquinas was ordained a priest about 1250, and he began to teach at the University of Paris in 1252. His first writings, primarily summaries and amplifications of his lectures, appeared two years later. His first major work was Scripta Super Libros Sententiarum (Writings on the Books of the Sentences, 1256?), which consisted of commentaries on an influential work concerning the sacraments of the church, known as the Sententiarum Libri Quatuor (Four Books of Sentences), by the Italian theologian Peter Lombard. In 1256 Aquinas was awarded a doctorate in theology and appointed professor of philosophy at the University of Paris. Pope Alexander IV (reigned 1254-61) summoned him to Rome in 1259, where he acted as adviser and lecturer to the papal court. Returning to Paris in 1268, Aquinas immediately became involved in a controversy with the French philosopher Siger de Brabant and other followers of the Islamic philosopher Averroës. In 1274 Thomas fell ill and died in the Cistercian abbey of Fossanova on March 7.
Aquinas was influenced by the writings of Aristotle, the Muslim Aristotelians Averroës and Avicenna, and the Jewish philosopher Maimonides. Unlike many theologians, he welcomed the Latin translation of Aristotle's complete writings. Aquinas meant to take Aristotle's philosophical arguments to their deepest level, not just to fit them into the existing theological framework. He pressed the distinction between potentiality and actuality and defended immortality without diminishing the doctrine that the soul is embodied.
His definition of philosophical disciplines starts with logic, which are the mental constructions we place on our experience. Theoretical philosophy isolates what is constant in changing facts, and is divided into 1) natural philosophy, the study of objects of material processes, 2) mathematical philosophy, the study of quantity without need to appeal to the sensible world, and 3) metaphysical philosophy, the study of the non-material. Moral philosophy studies personal ethics, economics, and politics.
Aquinas insisted that the truths of faith and those of sense experience, as presented by Aristotle, are fully compatible and complementary. Some truths, such as that of the mystery of the incarnation, can be known only through revelation, and others, such as that of the composition of material things, only through experience; still others, such as that of the existence of God, are known through both equally. All knowledge, Aquinas held, originates in sensation, but sense data can be made intelligible only by the action of the intellect, which elevates thought toward the apprehension of such immaterial realities as the human soul, the angels, and God. To reach understanding of the highest truths, those with which religion is concerned, the aid of revelation is needed. Aquinas's moderate realism placed the universals firmly in the mind, in opposition to extreme realism, which posited their independence of human thought. He admitted a foundation for universals in existing things, however, in opposition to nominalism and conceptualism.
Aquinas saw ideas as embodied here and now about us. Substance and accidents are the first categories of the material world, and material processes are shaped by the four causes - material, formal, efficient, and final. All material substances are composed of matter and form. His rejection of Neoplatonism scandalized some of his contemporaries; he was critical of the conception of humans as rational souls inhabiting powerless, material bodies. Like Aristotle, he saw the human being as a complete union of soul and body, of matter and form. Thus, in addition to the survival of the soul after death, the resurrection of the body seemed philosophically appropriate as well as religiously true.
In Part I of his great work, Summa Theologica, he provides his proof of the existence of God as the uncaused cause, existent in pure actuality without potentiality, an absolutely necessary being, an absolutely perfect being, and a rational designer. From these the thoughts of the unity, infinity, unchangeableness, and goodness of the highest being are deduced. God's knowledge is absolutely perfect since He knows Himself and all things as appointed by Him. God wills good to every being which exists; that is, He loves it, and love is the fundamental relation of God to the world. Aquinas goes beyond traditional negative theology and states that to say God is good means more than He is not evil, or that He is the cause of the goodness we see about us.
In Part II he discusses his system of ethics. In acts of will man strives for the highest end, which are free acts insofar as man has in himself the knowledge of their end and therein the principle of action. Whether the act be good or evil depends on the end. Human acts are good if they promote the purpose of God and His honor. By repeating a good action man acquires a moral habit which enables him to do the good gladly and easily. This is true only of the intellectual and moral virtues; the theological virtues are imparted by God to man as dispositions toward good and evil. An act becomes evil through deviation from the reason and the divine moral law. Sin has its origin in the will, which decides, against reason, for a changeable good. As God rules in the world, the "plan of the order of things" preexists in Him. Hence follows predestination; from eternity some are destined to eternal life and others fall short. Determinism is deeply grounded in his system, and on moral grounds Aquinas advocates freedom energetically; but, with his premises, he can have in mind only the psychological form of self-motivation. Nothing in the world is accidental or free.
The theme of Part III is Christ. He states that it cannot be asserted that the incarnation was absolutely necessary, "since God in His omnipotent power could have repaired human nature in many other ways," but it was the most suitable way both for the purpose of instruction and of satisfaction. All human potentialities are made perfect in Jesus by the vision of God. Christ's human nature was imperfect, partly to make His humanity evident, partly because He would bear the general consequences of sin for humanity. Christ experienced suffering, but blessedness reigned in His soul, which, however, did not extend to His body. Christ as head of humanity imparts perfection and virtue to His members. He is the teacher and example of humanity; His whole life and suffering as well as His work after He is exalted serve this end. Christ's suffering bore personal character in that it proceeded out of love and obedience. It was an offering brought to God, which as personal act had the character of merit. Thereby Christ "merited" salvation for men. As Christ, exalted, still influences men, so does He still work in their behalf continually in heaven through the intercession. In this way Christ as head of humanity effects the forgiveness of their sins, their reconciliation with God, their immunity from punishment, deliverance from the devil, and the opening of Heaven's gate.
Aquinas' synthesis of the divisions of Law dominates his political philosophy. Law is rational, it is for the common good of a communion of people. The Eternal Law in the mind of God is the exemplar of all law and is impressed on human minds as Natural Law. In contrast stands Positive Law which may sometimes reinforce Natural Law as pragmatic supplements to make the good life easier or to safeguard public order. He departed from the traditional Augustinian view that civil power was a remedy against our antisocial appetites, and revived Aristotle's idea of the State meeting the essential demands of human nature. Human legislation should know its limits, and not seek to cover the whole field of morality.
Aquinas's accomplishment was immense; his work marks one of the few great culminations in the history of philosophy. After Aquinas, Western philosophers could choose only between humbly following him and striking off in some altogether different direction. In the centuries immediately following his death, the dominant tendency, even among Roman Catholic thinkers, was to adopt the second alternative. Interest in Thomist philosophy began to revive, however, toward the end of the 19th century. In the encyclical Aeterni Patris (Of the Eternal Father, 1879), Pope Leo XIII recommended that St. Thomas's philosophy be made the basis of instruction in all Roman Catholic schools. Pope Pius XII, in the encyclical Humani Generis (Of the Human Race, 1950), affirmed that the Thomist philosophy is the surest guide to Roman Catholic doctrine and discouraged all departures from it. Thomism remains a leading school of contemporary thought. Among the thinkers, Roman Catholic and non-Roman Catholic alike, who have operated within the Thomist framework have been the French philosophers Jacques Maritain and Étienne Gilson.
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