St. Thomas Aquinas (AKA Thomas of Aquin or Aquino) (c. 1225 – 1274) was an Italian philosopher and theologian of the Medieval period. He was the foremost classical proponent of natural theology at the peak of Scholasticism in Europe, and the founder of the Thomistic school of philosophy and theology.
The philosophy of Aquinas has exerted enormous influence on subsequent Christian theology, especially that of the Roman Catholic Church, but also Western philosophy in general. His most important and enduring works are the «Summa Theologica», in which he expounds his systematic theology of the «quinquae viae» (the five proofs of the existence of God), and the «Summa Contra Gentiles».
Aquinas was born around 1225 to a noble family in the small town of Roccasecca, near Aquino, Italy, in what was then the Kingdom of Sicily. His father was Count Landulph and his mother was Theodora, Countess of Theate. His uncle, Sinibald, was abbot of the original Benedictine monastery at Monte Cassino and Aquinas was expected to follow his uncle into that position. At the age of 5, Aquinas began his early education at a monastery, and at the age of 16 he continued his studies at the University of Naples.
At Naples, Aquinas soon began to veer towards the Dominican Order, much to the deep chagrin of his family (who at one point seized and held him captive in an attempt to force him to toe the family line). However, after the intervention of Pope Innocent IV, he became a Dominican monk in 1242.
In 1244, the promising young Aquinas was sent to study under Albertus Magnus in Cologne and then in Paris, where he distinguished himself in arguments against the University’s celebrated champion Guillaume de St Amour (c. 1200 – 1272). Having graduated as a bachelor of theology in 1248, he returned to Cologne as second lecturer and magister studentium and began his literary activity and public life.
In 1256 Aquinas began many years of travel and lecturing on theology throughout France and Italy, along with his friend St. Bonaventure of Bagnoregio (1221 – 1274). During this period, he was often called upon to advise the reigning pontiff and the French King Louis VIII on affairs of state, and to represent the Dominican Order in meetings and discussions. Despite preaching every day, he found time to write homilies, disputations and lectures, and continued to work diligently on his great literary work, the «Summa Theologica».
Aquinas was characterized as a humble, simple, peace-loving man, given to contemplation, and a lover of poetry. He always maintained self-control and won over his opponents by his personality and great learning. There were various reports by friars and monks of minor miracles concerning Aquinas (ranging from levitation to voices from Heaven). He refused to participate in mortification of the flesh, which as a Dominican Friar he was supposed to observe. He also refused out of hand such prestigious positions as Archbishop of Naples and Abbot of Monte Cassino (although he was persuaded back to the University of Naples in 1272).
In 1270, the Bishop of Paris issued an edict condemning a number of teachings derived from Aristotle or from Arabic philosophers such as Averros which were then current at the university, and the teachings of Aquinas were among those targeted. The Dominican Order prudently moved him to Italy while the investigations proceeded in Paris. In 1274, en route to attend the Second Council of Lyons to attempt to settle the differences between the Greek and Latin churches, Aquinas fell ill and eventually died at the nearby Cistercian monastery of Fossa Nuova.
In 1277, three years after Aquinas’ death, the Bishop of Paris and the Bishop of Oxford issued another, more detailed, edict which condemned a series of Thomas’s theses as heretical, on the grounds of the orthodox Augustinian theology which considered human reason inadequate to understand the will of God. As a result of this condemnation, Aquinas was excommunicated posthumously (a landmark in the history of medieval philosophy and theology), and it took many years for his reputation to recover from this censure.
In 1324, fifty years after Thomas Aquinas’ death, Pope John XXII in Avignon pronounced him a saint of the Catholic church, and his theology began its rise to prestige. In 1568, he was named a Doctor of the Church. In 1879, Pope Leo XIII stated that Aquinas’ theology was a definitive exposition of Catholic doctrine, and directed clergy to take the teachings of Aquinas as the basis of their theological positions. Today, he is considered by many Catholics to be the Catholic church’s greatest theologian and philosopher.
Aquinas was a Christian theologian, but he was also an Aristotelian and an Empiricist, and he substantially influenced these two streams of Western thought. He believed that truth becomes known through both natural revelation (certain truths are available to all people through their human nature and through correct human reasoning) and supernatural revelation (faith-based knowledge revealed through scripture), and he was careful to separate these two elements, which he saw as complementary rather than contradictory in nature. Thus, although one may deduce the existence of God and His attributes through reason, certain specifics (such as the Trinity and the Incarnation) may be known only through special revelation and may not otherwise be deduced.
His two great works are the «Summa Contra Gentiles» (often published in English under the title «On the Truth of the Catholic Faith»), written between 1258 and 1264, and the «Summa Theologica» («Compendium of Theology»), written between 1265 and 1274. The former is a broadly-based philosophical work directed at non-Christians; the latter is addressed largely to Christians and is more a work of Christian theology.
Aquinas saw the raw material data of theology as the written scriptures and traditions of the Catholic church, which were produced by the self-revelation of God to humans throughout history. Faith and reason are the two primary tools which are both necessary together for processing this data in order to obtain true knowledge of God. He believed that God reveals himself through nature, so that rational thinking and the study of nature is also the study of God (a blend of Aristotelian Greek philosophy with Christian doctrine).
From his consideration of what God is not, Aquinas proposed five positive statements about the divine qualities or the nature of God:
- God is simple, without composition of parts, such as body and soul, or matter and form.
- God is perfect, lacking nothing.
- God is infinite, and not limited in the ways that created beings are physically, intellectually, and emotionally limited.
- God is immutable, incapable of change in respect of essence and character.
- God is one, such that God’s essence is the same as God’s existence.
Aquinas believed that the existence of God is neither self-evident nor beyond proof. In the «Summa Theologica», he details five rational proofs for the existence of God, the «quinquae viae» (or the «Five Ways»), some of which are really re-statements of each other:
- The argument of the unmoved mover (ex motu): everything that is moved is moved by a mover, therefore there is an unmoved mover from whom all motion proceeds, which is God.
- The argument of the first cause (ex causa): everything that is caused is caused by something else, therefore there must be an uncaused cause of all caused things, which is God.
- The argument from contingency (ex contingentia): there are contingent beings in the universe which may either exist or not exist and, as it is impossible for everything in the universe to be contingent (as something cannot come of nothing), so there must be a necessary being whose existence is not contingent on any other being, which is God.
- The argument from degree (ex gradu): there are various degrees of perfection which may be found throughout the universe, so there must be a pinnacle of perfection from which lesser degrees of perfection derive, which is God.
- The teleological argument or argument from design (ex fine): all natural bodies in the world (which are in themselves unintelligent) act towards ends (which is characteristic of intelligence), therefore there must be an intelligent being that guides all natural bodies towards their ends, which is God.
Aquinas believed that Jesus Christ was truly divine and not simply a human being or God merely inhabiting the body of Christ. However, he held that Christ had a truly rational human soul as well, producing a duality of natures that persisted even after the Incarnation, and that these two natures existed simultaneously yet distinguishable in one real human body.
Aquinas defined the four cardinal virtues as prudence, temperance, justice and fortitude, which he held are natural (revealed in nature) and binding on everyone. In addition, there are three theological virtues, described as faith, hope and charity, which are supernatural and are distinct from other virtues in that their object is God. Furthermore, he distinguished four kinds of law: eternal law (the decree of God that governs all creation), natural law (human «participation» in eternal law, which is discovered by reason), human law (the natural law applied by governments to societies) and divine law (the specially revealed law in the scriptures).
For St. Thomas Aquinas, the goal of human existence is union and eternal fellowship with God. For those who have experienced salvation and redemption through Christ while living on earth, a beatific vision will be granted after death in which a person experiences perfect, unending happiness through comprehending the very essence of God. During life, an individual’s will must be ordered toward right things (such as charity, peace and holiness), which requires morality in everyday human choices, a kind of Virtue Ethics. Aquinas was the first to identify the Principle of Double Effect in ethical decisions, when an otherwise legitimate act (e.g. self-defense) may also cause an effect one would normally be obliged to avoid (e.g. the death of another).
See the additional sources and recommended reading list below, or check the philosophy books page for a full list. Whenever possible, I linked to books with my amazon affiliate code, and as an Amazon Associate I earn from qualifying purchases. Purchasing from these links helps to keep the website running, and I am grateful for your support!
- Opera Omnia (Latin Edition)
by Horace (Creator), Wilhelm 1810-1882 Dillenburger Ed (Creator)
- Thomas Aquinas: Selected Writings (Penguin Classics)
by Thomas Aquinas (Author), Ralph McInerny (Editor)
- Aquinas’s Shorter Summa: Saint Thomas’s Own Concise Version of His Summa Theologica
by St. Thomas Aquinas (Author)
- Selected Philosophical Writings (Oxford World’s Classics)
by Thomas Aquinas (Author), Timothy McDermott (Translator)
- Summa Theologiae: A Concise Translation
by Thomas Aquinas (Author), Timothy McDermott (Editor)
- An Aquinas Reader: Selections from the Writings of Thomas Aquinas
by Mary T. Clark (Author)
- by Thomas Aquinas (Author), William P. Baumgarth (Editor), Richard J. Regan (Translator)
On Law, Morality and Politics, 2nd Edition (Hackett Classics) 2nd Edition
- The Philosophy of St. Thomas Aquinas
by Etienne Gilson (Author)
- The Cambridge Companion to Aquinas (Cambridge Companions to Philosophy) 1st Edition
by Norman Kretzmann (Editor), Eleonore Stump (Editor)
- St. Thomas Aquinas
by Ralph McInerny (Author)
- The Christian Philosophy Of St Thomas Aquinas
by Etienne Gilson (Author), L.K. Shook (Translator)
- Truth in Aquinas (Routledge Radical Orthodoxy) 1st Edition
by John Milbank (Author), Catherine Pickstock (Author)
- Thomist Realism and the Linguistic Turn: Toward a More Perfect Form of Existence 1st Edition
by John P. O’Callaghan (Author)
- Thomas Aquinas on Human Nature: A Philosophical Study of Summa Theologiae, 1a 75-89
by Robert Pasnau (Author)
- Ethica Thomistica: Moral Philosophy of Thomas Aquinas
by Ralph McInerny (Author)