Who Was Thomas Aquinas?

Understanding Romans 1:20 (KJV)

Thomas Aquinas is the most important systematic theologian in the history of Christianity. His Summa Theologica — an unfinished work spanning thousands of pages — attempted nothing less than the comprehensive organization of all Christian truth, integrating Scripture, patristic tradition, Aristotelian philosophy, and rational argument into a single coherent system. His achievement was so monumental that the Catholic Church declared him the Angelic Doctor and the Common Doctor of the Church, and his thought remains the official philosophical foundation of Catholic theology.

Early Life

Thomas was born around 1225 at Roccasecca, a castle between Rome and Naples, to a family of minor Italian nobility. His family intended him for a career as a Benedictine abbot — a respectable and influential position. At age five, he was sent to the Benedictine monastery of Monte Cassino for his education.

But at the University of Naples, Thomas encountered two things that changed his life: the recently rediscovered works of Aristotle and the Dominican Order. The Dominicans — the Order of Preachers, founded just a decade earlier — were mendicant friars committed to poverty, study, and preaching. They were intellectuals who lived like beggars. Thomas was captivated.

When he announced his intention to join the Dominicans, his family was horrified. The Dominicans were wandering beggars — a social disaster for a noble family. His brothers kidnapped him and held him captive in the family castle for over a year, attempting to change his mind. Thomas held firm. He eventually escaped (or was released) and entered the Dominican Order.

He studied under Albert the Great (Albertus Magnus) at Cologne and then at Paris — the two intellectual centers of medieval Europe. His fellow students reportedly called him 'the Dumb Ox' because of his large size and quiet demeanor. Albert allegedly responded: 'You call him the Dumb Ox, but I tell you that the whole world will one day hear his bellowing.'

The Aristotelian Revolution

To understand Aquinas, one must understand the intellectual crisis of the 13th century. For a thousand years, Christian theology had been conducted primarily within a Neoplatonic framework inherited from Augustine. Knowledge came from divine illumination, the material world was a shadow of higher spiritual reality, and faith provided the primary framework for understanding.

Then, in the 12th and 13th centuries, the full corpus of Aristotle's works — previously lost to Western Europe — was rediscovered through Arabic translations and commentaries (especially those of Averroes). Aristotle offered a complete philosophical system based on empirical observation and logical reasoning. His metaphysics, physics, ethics, and logic were comprehensive and compelling — but they were entirely pagan.

This created an existential crisis for the medieval university: Was Aristotle compatible with Christianity? Some thinkers (the 'Latin Averroists') argued for a 'double truth' theory — that something could be true in philosophy and false in theology. Conservative theologians wanted Aristotle banned. Aristotle's works were periodically condemned at Paris.

Aquinas took a different path: he argued that truth cannot contradict truth. If Aristotle's philosophy is genuinely true (and much of it is), it cannot contradict divine revelation, because both come from the same God. Where Aristotle was wrong (such as his belief in the eternity of the world), Scripture corrects him. Where Aristotle was right (such as his metaphysics of act and potency, substance and accident, the four causes), his insights can be baptized into Christian service.

This synthesis — the harmonization of faith and reason, revelation and philosophy, Augustine and Aristotle — was Aquinas's great achievement.

The Five Ways

Aquinas's most famous contribution to philosophy of religion is the Five Ways (Quinque Viae) — five arguments for God's existence presented in Summa Theologica I, Question 2, Article 3. These are not 'proofs' in the modern scientific sense but rational demonstrations based on observable features of the world:

1. The Argument from Motion. Everything that is in motion is moved by something else. But there cannot be an infinite regress of movers. Therefore, there must be a First Mover — unmoved itself — that initiates all motion. This is God.

2. The Argument from Efficient Causality. Every effect has a cause. But there cannot be an infinite regress of causes. Therefore, there must be a First Cause that is itself uncaused. This is God.

3. The Argument from Contingency. Everything we observe in nature is contingent — it could exist or not exist. If everything were contingent, there was once nothing, and nothing could have come from nothing. Therefore, there must be a Necessary Being whose existence is not contingent on anything else. This is God.

4. The Argument from Degrees of Perfection. We observe degrees of goodness, truth, and nobility in things. Degrees require a maximum — a standard of perfection against which lesser degrees are measured. There must be a being that is the maximum of all perfection. This is God.

5. The Argument from Design (Teleological Argument). Natural things that lack intelligence act toward ends — they behave purposefully. Things that lack intelligence cannot direct themselves toward ends unless directed by an intelligent being. Therefore, there must be an intelligent being who directs all natural things toward their ends. This is God.

Each argument concludes with the phrase 'and this everyone understands to be God' — Aquinas is not claiming to have proven the full Christian doctrine of God but only that reason can establish the existence of a being with certain attributes (necessary, uncaused, perfect, intelligent) that corresponds to what people call 'God.' The fuller knowledge of God's nature — Trinity, Incarnation, grace — comes only through revelation.

The Summa Theologica

The Summa (1265-1274) was intended as a textbook for theology students — 'beginners,' as Aquinas says in the prologue. It is organized into three parts:

Part I (Prima Pars): God — God's existence, attributes, Trinity, creation, angels, and humanity. Part II (Secunda Pars): Ethics — human happiness, virtues, vices, law, grace, and the specific moral virtues and commandments. This is further divided into Part I-II (general ethics) and Part II-II (specific virtues and their opposing vices). Part III (Tertia Pars): Christ and the Sacraments — the Incarnation, life of Christ, sacraments, and eschatology. (This part was left unfinished.)

The Summa uses a consistent format called the 'disputed question' method. For each topic, Aquinas:

1. States the question
2. Presents objections (arguments against his position)
3. Presents a 'sed contra' ('on the contrary') — usually a Scripture text or patristic authority
4. Gives his own answer (the 'respondeo' — 'I respond that...')
5. Replies to each objection individually

This method — fair, systematic, and thorough — allows Aquinas to take opposing arguments seriously, state them fairly (often more clearly than their original proponents), and then respond with precision.

Key Theological Contributions

Nature and grace. Aquinas's most famous axiom is 'Grace does not destroy nature but perfects it.' Reason and faith, philosophy and theology, nature and the supernatural are not opposed but complementary. Human reason can know certain truths about God (God's existence, basic attributes) through natural revelation. But saving knowledge — the Trinity, the Incarnation, the way of salvation — requires supernatural revelation. Faith completes and elevates reason; it does not replace it.

Analogy. How can we speak meaningfully about God when God infinitely transcends human language? Aquinas answers with the doctrine of analogy: when we say God is 'good' or 'wise,' we do not mean exactly what we mean when we say a human is good or wise (univocal predication), nor do we mean something entirely different (equivocal predication). We mean something analogous — God's goodness is like human goodness but infinitely greater. This doctrine preserves both the reality of our knowledge of God and the mystery of God's transcendence.

Natural law. Aquinas developed the most influential natural law theory in Western history. The natural law is humanity's participation in the eternal law of God through reason. Humans can discern basic moral truths — do good, avoid evil; preserve life; educate the young; seek truth; live in community — through rational reflection on human nature. This natural law is accessible to all people regardless of revelation and provides the foundation for civil law and universal human rights.

Eucharistic theology. Aquinas provided the philosophical framework for transubstantiation — the teaching that in the Eucharist, the substance of bread and wine is changed into the body and blood of Christ while the accidents (appearance, taste, texture) remain. Using Aristotelian categories of substance and accident, he gave the Church a precise vocabulary for articulating what it believed happened in the Mass.

The End

On December 6, 1273, while saying Mass, Aquinas had a mystical experience that caused him to stop writing. When urged to continue the Summa, he replied: 'I cannot, because all that I have written seems like straw to me.' He never wrote again.

Three months later, on March 7, 1274, Thomas Aquinas died while traveling to the Second Council of Lyon. He was 49 years old. The Summa Theologica remained unfinished — its final section on the sacraments and eschatology was later completed by his students from his earlier lecture notes.

Aquinas was canonized in 1323 and declared a Doctor of the Church in 1567. In 1879, Pope Leo XIII's encyclical Aeterni Patris declared Thomistic philosophy the official philosophy of the Catholic Church. His thought remains the foundation of Catholic seminary education and continues to influence Protestant, Orthodox, and secular philosophers who engage with natural law, virtue ethics, and the relationship between faith and reason.