The Life and Influential Works of Thomas Aquinas

Thomas Aquinas is one of the most important figures in the history of Western thought. Born in 13th-century Italy, he spent his relatively short life bridging two intellectual worlds – the traditions of Christian theology and the philosophical system of Aristotle. His work reshaped how the medieval Church understood the relationship between faith and reason, and his ideas continue to shape philosophy and theology today. This post covers his early life, education, and the two monumental works that secured his legacy: the Summa contra Gentiles and the Summa Theologiae.

Early life and family background 🔗

Thomas Aquinas was born around 1225 in Roccasecca, near Aquino, in what is now southern Italy. His family belonged to the lower ranks of the nobility. His father, Landulf, Count of Aquino, served Emperor Frederick II, and his mother, Theodora, was the Countess of Teano. Thomas was the youngest of nine children, and while his older brothers pursued military careers, his family had very different plans for him.

At just five years old, Thomas was sent to the nearby Benedictine abbey of Monte Cassino – one of the oldest and most prestigious monasteries in Europe, founded by St. Benedict himself. The family hoped Thomas would one day become abbot there, a position that carried significant political influence. For about a decade, young Thomas received his initial education under the Benedictine monks, laying the groundwork for his later intellectual achievements.

University education and encounter with Aristotle 🔗

Around 1239, Thomas was sent to the University of Naples for further studies. This proved to be a transformative period. The medieval university curriculum included training in the seven liberal arts – grammar, logic, rhetoric, arithmetic, geometry, music, and astronomy – followed by philosophy and theology. It was at Naples that Thomas first encountered the newly translated works of Aristotle, which were filtering into Europe through Arabic translations and commentaries by scholars like Avicenna and Averroes.

Most of Aristotle’s writings had been lost to the Latin-speaking West for nearly a thousand years. Arab philosophers had preserved and commented on these texts, and their arrival in European universities sparked both excitement and controversy. Aristotle’s ideas about the eternity of the world and the mortality of the soul appeared to conflict with Christian teaching. Thomas would spend much of his career showing that these apparent contradictions were either misreadings of Aristotle or conclusions that could be challenged on philosophical grounds.

Joining the Dominicans 🔗

While at Naples, Thomas was drawn to a relatively new religious order: the Order of Preachers, commonly known as the Dominicans. Founded by St. Dominic de Guzman around 1216, this order prioritized preaching, teaching, and intellectual work – a sharp departure from the cloistered monastic life Thomas had known at Monte Cassino. In 1244, Thomas received the Dominican habit.

His family was not pleased. They had envisioned a prestigious position for Thomas as a Benedictine abbot, not life in a mendicant order that depended on begging for sustenance. His brothers intercepted him on the road to Paris and brought him back to the family castle, where he was held under a form of house arrest for roughly a year. Despite prolonged pressure, Thomas refused to abandon his new vocation. His family eventually relented, and he returned to the Dominicans.

Studies under Albert the Great 🔗

The Dominicans recognized Thomas’s exceptional intellect early on and sent him to study under Albert the Great (Albertus Magnus) at the University of Paris around 1245, and then at Cologne. Albert was the foremost Aristotelian scholar in the Christian world at the time, and he became a decisive influence on Thomas’s intellectual development. According to a well-known anecdote, Thomas’s classmates in Cologne initially mocked him as a “dumb ox” because of his large, quiet presence. Albert is said to have responded that this “dumb ox” would one day make his voice heard across the world.

Teaching career and rising influence 🔗

Thomas returned to Paris around 1252 to work toward his Master of Theology degree. He earned the licentia docendi (license to teach) in 1256 and began lecturing as a Master of Theology at one of the Dominican schools within the University of Paris. At the remarkably young age of 32, he was already one of the most respected theologians in Europe.

After three years at Paris, Thomas returned to Italy, teaching at Naples, Orvieto, and Rome over the next decade. In 1265, Pope Clement IV summoned him to Rome to serve as a papal theologian. He also taught at a newly established Dominican school at Santa Sabina. In 1268, he was called back to Paris for a second regency, this time partly to combat the growing influence of Averroism – a heterodox interpretation of Aristotle that claimed philosophical truths could contradict theological ones.

Thomas spent his final years back in Naples, where he founded a new Dominican university and continued his writing. In 1274, while traveling to the Second Council of Lyons at Pope Gregory X’s request, Thomas suffered an accident, fell ill, and died on March 7, 1274, at approximately 49 years of age.

The Summa contra Gentiles 🔗

The Summa contra Gentiles, written between approximately 1259 and 1265, is one of Thomas’s most important works. It stands as a landmark in Christian apologetics and natural theology. According to a long-standing tradition, it was composed at the request of Raymond of Peñafort, a fellow Dominican, to assist missionaries working to convert Muslims and Jews in Spain. Whether or not this origin story is entirely accurate, the work’s approach supports it: the first three books rely almost entirely on philosophical reasoning rather than Scripture, making arguments that could, in principle, be accepted by any rational person regardless of religious background.

Structure and content 🔗

The Summa contra Gentiles is divided into four books. Book One examines God’s existence, nature, and attributes – His perfection, knowledge, will, and love – using arguments grounded in reason. Book Two deals with creation, exploring God’s power as the source of all things and the nature of the human being, particularly the relationship between soul and body. Book Three addresses divine providence, the hierarchy of creation, and the relationship between human beings and God, arguing that genuine happiness can only be found in the contemplation of God. Book Four turns to matters of revealed theology – the Trinity, the Incarnation, and the sacraments – topics that go beyond what reason alone can demonstrate.

What makes the Summa contra Gentiles distinctive is its engagement with Greek and Arabic philosophical traditions. Thomas did not simply dismiss non-Christian thinkers. He took their arguments seriously and incorporated their insights where he found them compatible with Christian truth. The work represents a sustained effort to demonstrate that rational philosophy and Christian faith are not enemies but allies.

The Summa Theologiae 🔗

Thomas began his most famous work, the Summa Theologiae (sometimes called the Summa Theologica), around 1265 while teaching in Rome. He continued working on it until December 1273, when he abruptly stopped writing after a mystical experience during Mass. He reportedly said that everything he had written seemed like “straw” compared to what had been revealed to him. The work was left unfinished – he had reached the section on penance in Part III – and his students later completed it using material from his earlier commentary on Peter Lombard’s Sentences.

Structure and scope 🔗

The Summa Theologiae is organized into three major parts. Part I (Prima Pars) covers God’s existence and nature, creation, angels, and the nature of human beings. Part II is divided into two sub-parts: the Prima Secundae addresses general moral theory, including happiness, law, virtues, and sin, while the Secunda Secundae examines specific virtues and vices in detail. Part III (Tertia Pars) treats Christ, the sacraments, and the path to salvation.

The method Thomas uses throughout is the scholastic disputation format. Each topic is framed as a question, followed by a series of objections, a response (the sed contra), and then Thomas’s own reasoned answer, concluding with replies to each objection. This rigorous structure allowed him to address virtually every major question in Christian theology systematically.

The Five Ways 🔗

Perhaps the most famous section of the Summa Theologiae is Question 2 of Part I, where Thomas presents his Five Ways – five arguments for the existence of God. Each draws heavily on Aristotelian philosophy:

The argument from motion: Everything in motion must be moved by something else. This chain cannot go back infinitely, so there must be a first unmoved mover – God. The argument from efficient causation: Every effect has a cause, and the chain of causes cannot regress infinitely, so there must be a first uncaused cause. The argument from contingency: Things in the world come into and go out of existence. If everything were contingent, nothing would exist now. Therefore, there must be a necessary being. The argument from degrees of perfection: Things exhibit varying degrees of goodness and perfection, pointing to a supreme standard of perfection, which is God. The argument from final causes: Natural things that lack intelligence act toward ends, implying an intelligent being that directs them – and this is God.

These arguments were not entirely original to Thomas – they drew on Aristotle, Avicenna, and earlier Christian thinkers – but Thomas synthesized them into a coherent framework that became foundational for natural theology in the Western tradition.

Integrating Aristotle with Christian theology 🔗

The central achievement of Thomas’s career was his synthesis of Aristotelian philosophy with Christian doctrine. In the 13th century, this was a bold and controversial project. Many theologians in the Augustinian tradition were deeply suspicious of Aristotle’s “pagan” philosophy. On the other side, followers of the Arab commentator Averroes argued that philosophy and theology could reach contradictory conclusions – the so-called doctrine of double truth.

Thomas rejected both positions. He argued that faith and reason are complementary because both ultimately derive from God. Reason, working through philosophical methods, can establish certain truths about God – His existence, unity, and goodness. These are what Thomas called the “preambles of faith” – truths accessible to reason that prepare the mind for revealed truth. But reason has its limits. Doctrines like the Trinity and the Incarnation surpass what philosophy can demonstrate and must be accepted through faith.

Thomas’s approach did not subordinate philosophy to theology or reduce theology to philosophy. Instead, he gave each discipline its proper domain and showed how they could work together. Philosophy provided the rational tools and conceptual vocabulary – drawn largely from Aristotle – while theology provided access to truths revealed by God that reason could not reach on its own.

Legacy and lasting impact 🔗

Thomas Aquinas was canonized in 1323, less than fifty years after his death. In 1567, he was named a Doctor of the Church. His influence grew dramatically in 1879, when Pope Leo XIII issued the encyclical Aeterni Patris, which declared Thomas’s theology a definitive expression of Catholic doctrine and directed all Catholic seminaries to teach his philosophy.

His intellectual system, known as Thomism, remains one of the most studied philosophical traditions in the world. The Summa Theologiae continues to serve as a standard reference in Catholic theological education, and his arguments for God’s existence remain central to discussions in the philosophy of religion. Beyond theology, his writings on ethics, natural law, political philosophy, and the philosophy of mind continue to attract scholarly attention across disciplines.

What makes Thomas enduringly relevant is not simply the conclusions he reached, but the method he modeled: a fearless willingness to engage with the best ideas available – regardless of their source – and to test them rigorously against both reason and faith.

What do you think? Was Thomas Aquinas right that faith and reason can never truly contradict each other, or are there areas where philosophy and theology must simply part ways? And does his method of engaging seriously with non-Christian thinkers offer a model for intellectual dialogue today?

References

1. https://www.britannica.com/biography/Saint-Thomas-Aquinas
2. https://iep.utm.edu/thomas-aquinas/
3. https://plato.stanford.edu/entries/aquinas/
4. https://www.biography.com/religious-figure/saint-thomas-aquinas
5. https://faith.nd.edu/saint/st-thomas-aquinas/
6. https://thegreatthinkers.org/aquinas/biography/
7. https://www.britannica.com/topic/Summa-contra-gentiles
8. https://undpress.nd.edu/blog/2024/09/06/st-thomas-aquinas-and-summa-contra-gentiles/
9. https://en.wikipedia.org/wiki/Summa_Theologica
10. https://www.britannica.com/topic/the-Five-Ways
11. https://philopedia.org/arguments/five-ways-of-aquinas/