Thomas Aquinas

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Thomas Aquinas (TAHM-uhs uh-KWI-nuhs) is generally agreed to be the towering figure in medieval theology, and to him goes the principal credit for applying the philosophical doctrines of Aristotle to Christianity. The joining of these seemingly divergent streams of thought in the philosophical movement known as Scholasticism has had tremendous influence on subsequent theological and philosophical thinking.{$S[A]Aquinas, Thomas;Thomas Aquinas}

Thomas was well prepared by his background for the work that was to engage far and away the major portion of his efforts. Born at Roccasecca, near Aquino, Italy, in 1224 or 1225, the son of Count Landolfo of Aquino, he was raised in an atmosphere of ease. Having studied at the Abbey of Monte Cassino, he went from there, in 1239, to Naples to study the liberal arts. He then entered the Order of St. Dominic (c. 1243), abandoning his life of privilege to become a “begging friar.”

Thomas was fortunate to be able to study under Albert the Great (Albertus Magnus) in Paris from 1245 to 1248. While with Albert in Cologne, after his studies in Paris, he was ordained to the priesthood. Shortly thereafter he received advanced degrees in theology. He spent the rest of his life teaching and writing his great treatises—such as his commentary on the Sentences of Peter Lombard (c. 1100-c. 1160)—in Rome, Paris, and Naples.

Of his works, the two most important are his Summa contra gentiles, which defends Christianity in the area of natural theology, and Summa Theologica, a work whose three divisions are related to God, Man, and Christ and in which Thomas attempted to summarize all human knowledge. This monumental treatise was left unfinished when he died of a sudden illness on March 7, 1274, at Fossanova, Italy, while traveling to the General Council of Lyons. St. Thomas Aquinas, canonized in 1323, remains a central thinker in Christian theology because of his synthesization of past knowledge and his application of the principles of scholastic reasoning to religion.


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The moral life, for Thomas Aquinas, consists in each person achieving human fulfillment through freely chosen actions. Presupposed is a human nature with a given, determinate structure and a corresponding determinate fulfillment or perfection. Actions are morally good if they promote this fulfillment and bad if they hinder it. In this sense, Aquinas’ ethics are teleological and eudaimonistic, but unlike classical utilitarianism, the end of good action is not simply pleasure, but the perfection of the human being. Being naturally social, persons cannot attain their perfection alone, but only in community. Consequently, although the ethical life is ordered to promote personal fulfillment, it is not individualistic. Every aspect of Aquinas’ ethics (good action, virtue, law, and so forth) is understood in the light of achieving one’s fulfillment.

Happiness and Beatitude

Aquinas recognized two levels of human fulfillment or happiness. First is the perfection of human nature simply on the natural level, which is the object of philosophical ethics. Second is the Christian understanding of human nature as raised by divine grace and destined to a supernatural end. Theological ethics treats the latter and was Aquinas’ major concern. At both levels, happiness lies primarily in intellectual activity, that of knowing God. The natural end consists in knowing God by philosophical investigation, while the supernatural end consists in a direct vision of God, which is possible only after death.

Good and Evil Actions

Actions such as studying, educating, praying and temperate eating are good because they are intrinsic to true human fulfillment, while acts like murder, stealing, or adultery hinder it and therefore are evil. Besides choosing and performing a good act, a person must intend a good...

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end; friendship in itself is good, but it would not be morally good if it were chosen for the sake of vanity or ambition. Morally good action requires a good act, the right circumstances, and a good intention.

Virtue and Vice

An integral part of Aquinas’ ethics is his theory of virtue and vice. Both virtue and vice are “habits,” steady inner dispositions inclining an agent to a certain mode of action. The virtue of courage inclines one to face dangers when reason judges that good action requires it; under the influence of the vice of cowardice, one would tend to commit evil action rather than face danger. Hence, all habitual tendencies toward perfective activities are virtues and their opposites are vices. There are many different moral virtues and vices corresponding to the many different spheres of moral action: the virtue of religion is a disposition to be properly related to God, liberality is the virtue of being generous with one’s wealth, truthfulness concerns speaking the truth, and so on. The chief moral virtues are the four cardinal virtues: temperance, the right disposition toward pleasures (opposed vices: gluttony, drunkenness, sexual promiscuity); courage, the right disposition toward fearful dangers (opposed vices: cowardice, recklessness); justice, the disposition to respect the rights of others and to treat them fairly (opposed vice: injustice); and prudence, the disposition to deliberate well about moral action. Since all good action requires a good judgment about what should be done, every other virtue depends upon prudence. These moral virtues are acquired by repeatedly performing appropriate virtuous actions.

The theological virtues are infused by God and are dispositions toward actions directed to the supernatural end. By means of the three theological virtues, faith, hope, and charity (love), a person believes, hopes in, and loves God. These virtues, for Aquinas, are higher than the moral virtues, and among them charity is the highest. Ultimately, every virtuous action is done for the love of God and therefore depends upon the virtue of charity.

Moral Law

Moral law is a rational principle that directs actions toward their proper ends. Lacking animal instinct, free, rational, moral agents direct themselves toward an end according to a rational conception. This is supplied by the law, which commands good acts and prohibits bad acts. Since action always occurs in singular, concrete circumstances, however, law alone is an insufficient rule. Every particular action requires a prudential judgment as its proximate rule.

There are several kinds of law. First is the divine law, the explicit commands of God, such as the Ten Commandments or the Beatitudes, which direct persons to their supernatural end. Second is the natural law, consisting of general principles of right action that are discovered by reason, which reflects on human experience and learns over time what leads to fulfillment and what does not. Because human nature is determinate and is shared by all, the general principles of the natural law are valid for everyone and for all times. Finally, there are human positive laws, the civil laws enacted by society. These are part of the moral law in that they direct moral actions, especially those related to life in society. If, however, a civil law contradicts the natural law or the divine law, it is not a true law and has no binding force. All law, Aquinas said, is ultimately part of the eternal law, the ordering wisdom of God by which he governs the whole of creation.


Bradley, Denis J. M. Aquinas on the Twofold Human Good: Reason and Human Happiness in Aquinas’s Moral Science. Washington, D.C.: Catholic University of America Press, 1997. Bradley argues that Saint Thomas Aquinas was a theologian first and philosopher second. He contends that to avoid misinterpretation, Aquinas’s writings should be approached from a theological, rather than a philosophical, approach.

Chesterton, G. K. St. Thomas Aquinas. New York: Sheed and Ward, 1933. A superb introduction to the life and thought of Thomas, “the Angelic Doctor.” Aimed at non-Christian readers, or those with little experience in theology.

Davies, Brian. Aquinas. New York: Continuum, 2002.

Inglis, John. On Aquinas. Belmont, Calif.: Wadsworth/Thompson Learning, 2002.

Kenny, Anthony. Aquinas. New York: Hill and Wang, 1980. This volume in the Past Masters series covers Thomas’s life in fewer than one hundred pages. Thomas’s theories are explored, including his conception of Being (which Kenny believes is hopelessly flawed) and his notion of the nature of Mind (which Kenny praises for the questions Thomas asks). Latter chapters introduce the reader to medieval categories of thought, but Thomas the Christian is almost submerged.

McInerny, Ralph. Ethica Thomastica: The Moral Philosophy of Thomas Aquinas. 1982. Rev. ed. Washington, D.C.: Catholic University of America Press, 1997. This work is one of the finest introductions to Thomas’s moral philosophy. Covers selected themes in Thomistic moral thinking, including moral goodness, judging good and evil moral actions, work of virtues, functions of conscience, and relation of ethics to religious belief.

McInerny, Ralph. St. Thomas Aquinas. Boston: Twayne, 1977. An accessible study of Thomas’s thought in chapters dealing with Aristotle, Boethius (whose philosophy was introduced to modern times through Thomas’s writings), and Platonism. In a chapter on the tasks of theology, the author explains Thomas’s distinction between believing and knowing. The book is filled with examples and includes a useful chronology of Thomas’s life plus a short, annotated bibliography.

Milbank, John. Truth in Aquinas. New York: Routledge, 2001.

Nichols, Aidan. Discovering Aquinas: An Introduction to His Life, Work, and Influence. London: Darton Longman & Todd, 2002.

Oguejiofor, J. Obi. The Philosophical Significance of Immortality in Thomas Aquinas. Lanham, Md.: University Press of America, 2001.

Pope, Stephen, ed. The Ethics of Aquinas. Washington, D.C.: Georgetown University Press, 2002.

Shanley, Brian J. The Thomast Tradition. Boston: Kluwer, 2002.

Sigmund, Paul E., ed. St. Thomas Aquinas on Politics and Ethics. New York: W. W. Norton, 1987. An introduction to Thomas, with eighty pages devoted to pertinent excerpts of Thomas’s work, newly translated by the editor. Selections are generally quite short and range from Thomas’s writings on government to selections from his treatise on God in Summa Theologica. Excerpts from background sources are also presented, with the remainder of the volume devoted to interpretations of Thomas.

Wippel, John F. The Metaphysical Thought of Thomas Aquinas: From Finite Being to Uncreated Being. Washington, D.C.: Catholic University of America Press, 2000.