Thomas Aquinas

Thomas Aquinas
Institutions	University of Paris; University of Naples Federico II
School tradition	Scholasticism; Thomism; Aristotelianism
Known for	Integrating Aristotelian philosophy with Christian doctrine
Occupation	Philosopher; theologian
Notable works	Summa Theologiae; Summa contra Gentiles
Era	Medieval philosophy
Notable ideas	Natural law; Five Ways; Analogy of being
Field	Philosophy; theology
Wikidata	Q9438

Thomas Aquinas (1225–1274) was an Italian Dominican friar, philosopher, and theologian whose comprehensive writings became a cornerstone of medieval scholasticism. He carefully blended the newly rediscovered works of the ancient Greek philosopher Aristotle with Christian doctrine, showing that faith and reason could work together. Aquinas’s most famous book is the Summa Theologiae, a systematic presentation of Christian theology organized in question-answer form. Among his ideas, he offered logical “proofs” of God’s existence, formulated a notion of natural law (the view that basic moral truths can be known by human reason from nature), and described how human virtues lead to happiness. Celebrated as a saint and “Doctor of the Church” (an honorary title for great Catholic teachers), Aquinas profoundly influenced Catholic theology and remains an important figure in Western philosophy and ethics.

Early Life and Education

Thomas Aquinas was born around 1225 into a noble family at Roccasecca, in what is now Italy. As the youngest of several sons, he was expected to enter the Church. At about age five he was sent to the Benedictine abbey of Monte Cassino to begin his education. He learned Latin, logic, and other basic subjects there. Political conflicts in Italy (between the Holy Roman Emperor and the Pope) forced the monks to leave Monte Cassino, and in 1239 Thomas was moved to the University of Naples to continue his studies. At Naples he studied the arts and philosophy, including the newly arrived translations of Aristotle’s works and related commentaries. He soon became proficient in logic and loved mathematics, but under the influence of Dominican and Franciscan friars he felt called to join the Dominican Order of Preachers – a new mendicant (begging) religious order dedicated to teaching and evangelism.

In 1244 Thomas entered the Dominican convent at Naples, but his decision angered his family. His mother and brothers tried to change his mind. They even kidnapped him and held him near Roccasecca for about a year, hoping he would renounce his vows. Legend tells that they once sent a prostitute to tempt him, but Thomas was resolute and reportedly chased the woman away with a burning firebrand, then felt a mystical protection. The stories emphasize his determination to live a celibate life. Eventually his family relented and allowed him to return to study with the Dominicans.

In the autumn of 1245, the Dominicans sent Aquinas to the University of Paris, the leading center of theology in Europe. There he studied under Albertus Magnus (Albert the Great), a renowned scholar of Aristotle and theology. When Albertus Magnus moved to the University of Cologne in 1248, Thomas went with him and became his assistant. Fellow students nicknamed Thomas the “dumb ox” because of his quiet, serious manner, but Albert praised him, saying that one day he would “bellow” so loudly that the world would take notice. Thomas learned Aristotle’s philosophy from Albert and applied it to theology. By 1252 he returned to Paris to pursue his masters in theology and to teach.

Thomas spent 1252–1256 teaching at Paris and writing a commentary on Peter Lombard’s Sentences (a standard theological textbook). In 1256 he became a regent master (professor) of theology at Paris, meaning he was one of the university’s leading teachers. During these Paris years, he also wrote De ente et essentia (On Being and Essence), a short treatise for fellow Dominicans. In 1259–1261 Aquinas moved to Italy (Naples), then served as a papal chaplain in Orvieto (1261–1265) and in Rome (1265–1268). In those years he began his magnum opus, the Summa Theologiae. In 1268–1272 he returned to teach at Paris, defending the academic freedom of the mendicant orders there. Late in 1272 he was sent back to Naples, where he completed the first two parts of the Summa Theologiae and began the third.

Major Works and Ideas

Aquinas was an extraordinarily productive writer. His major works are grand theological syntheses and detailed commentaries. The Summa Theologiae (1265–1274) was intended as a comprehensive guide for theology students. It covers all main Catholic doctrines: God’s nature, faith, the sacraments, ethics, and the destiny of humankind. It is organized by parts, each containing numbered questions and articles. Each article poses objections, cites authoritative opinions, and then gives Aquinas’s answer, followed by replies to each objection. Intended as a teaching tool, the Summa uses clear logical structure and draws on Scripture, Church Fathers, and Aristotle to explain Christian beliefs. He did not quite finish it before his death (he left the final questions on the sacraments unfinished).

Another major work is the Summa Contra Gentiles (c.1259–1265), written primarily to explain and defend the Christian faith to non-Christians (such as Jews, Muslims, or unbelieving scholars). It is also systematic but more philosophical, starting from natural reason to reach truths about God, creation, and morality. Earlier, in the 1250s, Thomas wrote the Scriptum super libri Sententiarum Physicarum Luminarium (a commentary on Peter Lombard’s Sentences) as was common for theologians earning degrees. He also wrote important political and ethical treatises, such as De Regimine Principum (“On the Governance of Rulers,” c.1266–1267), offering advice to a king of Cyprus on just rule and virtue.

Aquinas wrote extensive commentaries on Aristotle’s works (for example, on Aristotle’s Nicomachean Ethics, Metaphysics, Physics, and De Anima). By doing so, he helped bridge Greek philosophy and Christian theology. Thomas learned Aristotle’s science and logic (often through Arabic or Latin translations) and believed these tools could serve Christian truths. He often began theological topics by appealing to reason and nature (Aristotle’s realm) before moving to faith-based conclusions.

One of Aquinas’s distinctive philosophical contributions is his famous “Five Ways” (quinque viae) to demonstrate that God exists. These are logical arguments based on everyday observations: * The First Way (from motion): things in the world move or change, and whatever moves must be moved by something else; tracing this chain leads to a “first Mover,” which is God.

The Second Way (from cause): every effect has a cause, and there must be a first uncaused cause (God).

* The Third Way (from contingency): many things come into and go out of existence, so there must be a necessary being that causes contingent beings (God).

The Fourth Way (from degrees): we judge things as better or worse, but there must be a maximum standard (the perfect being, God) that makes these comparisons possible.

* The Fifth Way (from design): natural bodies act toward ends (like an arrow to a target) that seem purposeful even without intelligence; thus there must be an intelligent director (God). These arguments are often cited as examples of natural theology (reasoned reflection on God’s existence without appeal to revelation). For Aquinas, the conclusion of all five was simply that God exists and is the ultimate source of all being.

Aquinas deeply engaged in metaphysics (the study of reality and existence). He followed Aristotle in distinguishing between the *essence of a thing (what it is) and its existence (that it is real). Aquinas taught that in God alone are essence and existence identical (God’s essence is to exist), whereas in all created things existence is something they receive. This idea underlined God’s uniqueness. He also taught that creatures are composites of matter and form: for humans, our body is the matter and the soul is the form. In his view the soul is an immaterial, rational form that gives life and identity to the body. Unlike some earlier ideas, Aquinas argued the soul could exist apart from the body after death (supporting the Christian hope of resurrection). He believed human reason and experience from the senses are the starting points of knowledge, but the intellect can abstract universal concepts (for example, from seeing many trees we grasp the idea of “treeness”).

In ethics and political philosophy, Aquinas is known for articulating an early natural law theory. He proposed a hierarchy of law: eternal law (God’s plan for all creation), natural law (the moral principles imprinted in human nature that we can discover by reason), divine law (God’s revealed law in Scripture), and human law (rules created by society). The natural law, he taught, consists of self-evident moral principles such as “shun evil, do good.” From these first principles derive more specific precepts (for example, preserving life, educating offspring, living peacefully in society, worshiping God). Thomas held that humans have an innate inclination toward the good (happiness and union with God) and can know basic right and wrong by reflecting on human nature. He classified human virtues into two sets: the theological virtues (faith, hope, charity) which orient us directly toward God, and the cardinal virtues (prudence, justice, temperance, fortitude) which govern moral life. Living virtuously, for Aquinas, leads to true human flourishing or beatitude, which ultimately means seeing and loving God. In moral decisions, Aquinas introduced the principle of double effect: a good action may be permissible even if it has a bad side-effect, provided the bad effect is not intended (an idea still influential in Catholic ethics).

Throughout his works, Aquinas insisted that truth is unified. He famously said that “grace perfects nature,” meaning that Christian faith (God’s revelations and gifts) does not destroy human reason and the natural world but builds on them. He argued that those truths the human mind can reach by reason are not truly in conflict with the truths revealed by God’s Word; if conflict appears, it is due to misunderstanding. In sum, Aquinas’s ideas represent a grand synthesis: he took Aristotle’s logic, science, and metaphysics and applied them to explain Christian doctrines. His thought produced a systematic theology and philosophy where God is the ultimate cause and final end of everything, and where human beings use reason and faith together to understand their place in creation.

Method

Aquinas was a leading representative of the scholastic method, the medieval style of learning that emphasized logical analysis of theological and philosophical questions. In this method, issues are discussed as objections and replies, much like a debate. For example, in the Summa Theologiae each article (topic) begins with objections stating possible counter-arguments, then a brief statement “I answer that” where Thomas gives his conclusion, followed by detailed explanation, and finally replies to each objection. This rigorous question-and-answer style (often called a quodlibet or disputation) allowed him to address objections from different authorities or philosophical schools and then clarify why his answer holds. He used Aristotelian logic and categories in his arguments, respecting principles like non-contradiction (“something cannot both be and not be in the same way”) and syllogistic reasoning.

Aquinas distinguished between different ways of knowing. He held that reason alone (natural philosophy) can reach many truths about God and the world (like God’s existence, basic moral truths), but some mysteries (e.g. the Trinity, Incarnation) are beyond unaided reason and require divine revelation. Nonetheless, he argued that even revealed truths must not contradict reason, for “all truth is from the Holy Spirit.” In practice, when theological doctrine seemed puzzling, Aquinas would often consult philosophy to clarify and vice versa. He said wisdom is like the blending of two streams that are both from God. In this sense, his method was to respect both faith (answers known from Scripture and Church teaching) and reason (logical arguments, sense experience, and philosophy) as paths to truth.

Influence

Aquinas’s influence was immense and long-lasting. Within decades of his death, the Dominican Order defended his teachings vigorously, and by the late 13th century many of his ideas became standard in the Catholic theological curriculum. In 1323 (less than 50 years after his death) Aquinas was canonized a saint by Pope John XXII, and in 1567 he was proclaimed a Doctor of the Church. The Catholic Church formally honors him as the “Angelic Doctor” and the model of Catholic theologians. His works became required reading for priests and scholars.

In the centuries after Aquinas, Thomism (the school of thought following Aquinas) shaped Western thought in many areas. Medieval and Renaissance thinkers debated his views and wrote extensive commentaries. For example, in the 14th century Jean Capréolus defended Aquinas’s ideas against rival theologians. In the 16th and 17th centuries, scholars at the University of Salamanca (Spain) like Francisco de Vitoria and Domingo de Soto applied Aquinas’s natural law ideas to justice, war, and the rights of indigenous peoples, pioneering ideas later found in international law. His thoughts on morality, government, and natural rights influenced notions of human dignity; some see Aquinas’s natural law as a distant ancestor of modern human rights.

Even Protestant thinkers engaged with Aquinas. Martin Luther and John Calvin, though often critical of scholasticism, were trained in Aquinas’s works and responded to his ideas about free will and grace. Calvin’s own theological education came through Aquinas’s legacy. In the Enlightenment and modern era, Aquinas was less of a dominant force (many philosophers turned to science and rationalism), but interest in him revived in the 19th and 20th centuries. In 1879, Pope Leo XIII encouraged a “Thomistic revival” in his encyclical Aeterni Patris, urging Catholic schools to study Aquinas as a corrective against what he saw as modern errors. Catholic scholars like Étienne Gilson and Jacques Maritain in the early 20th century reintroduced Aquinas’s ideas to contemporary philosophy and theology, making him a figure of interest even beyond strictly religious circles.

Today Aquinas is widely studied in theology and philosophy departments worldwide. His concepts of being, causality, and law still play roles in metaphysics, ethics, and natural law theory. The principle that an unjust law is no true law (from Aquinas’s theory of law) is reflected in many legal and political writings. Catholic universities and seminaries often teach Thomistic philosophy and theology, and he is the patron saint of students and Catholic schools. In the Western tradition, Aquinas is regarded as one of the great medieval thinkers, ranking alongside Augustine or Anselm. His footsteps are seen in later philosophical movements, and he continues to be a reference point in debates on faith and reason, ethics, and the nature of knowledge.

Critiques

Throughout history, Aquinas’s work has been praised and criticized. Even soon after his time, some of his ideas were controversial. In the 1270s, while Aquinas was still alive or shortly after his death, theologians at the University of Paris and some bishops condemned a few propositions associated with his philosophical interpretations (for instance, about the soul’s knowledge of God or aspects of divine foreknowledge). These condemnations arose because some saw his use of Aristotle and certain Islamic-influenced ideas as a threat to official doctrine. However, these objections were minor in scope, and generally the Church affirmed Aquinas’s orthodoxy.

Other medieval and early-modern critics took issue with parts of his system. A rival medieval philosopher, William of Ockham, objected to Aquinas’s realism about universals and his synthesis of philosophy with theology. Ockham and nominalists argued differently about how concepts correspond to reality. In the 17th century there was a famous debate (the Congregatio de Auxiliis) between Dominicans and Jesuits over grace and free will: Aquinas’s followers (Dominicans) and the Jesuits each claimed his views, but eventually the Pope forbade either side from condemning the other, leaving some questions unanswered.

When Protestant Reformers opposed scholastic intellectualism, they often rejected Aquinas’s methods. Martin Luther famously declared that reason could never yield faith. In practice, many Protestant theologians found Aquinas’s emphasis on Aristotle and papal authority too much and preferred Scripture as the sole source of truth. Over time, outside of Catholicism, Aquinas’s direct influence waned, though his ideas still had indirect impact through general Christian culture.

In modern times, some secular philosophers criticize Aquinas. Critics say his “proofs” for God rely on outdated premises or that he assumes conclusions in his premises. New scientific understanding replaced much of Aristotle’s physics (for example, the idea of fixed natural places or an unmoving celestial sphere), and with it some of Aquinas’s natural philosophy became obsolete. Many view his concept of essence and final causes as irrelevant to contemporary physics. Ethical ideas like slavery or class hierarchy that Aquinas did not challenge are condemned today; indeed, he accepted (as most in his day did) that slavery resulted from war, a view now rejected as unjust. His statements about women reflect medieval sexism: Thomas wrote that women were somehow “imperfect” versions of men, a view that modern readers find offensive and false. In general, aspects of his thought mirror the limits of 13th-century society: for example, he assumed a strict social order of ranks, which clashes with modern ideas of equality. Contemporary theologians sometimes see his system as too general or abstract for the complexities of modern life, and some Catholic thinkers after Vatican II sought new approaches to theology.

Nevertheless, many critiques of Aquinas acknowledge that he was writing before empirical science developed. His emphasis on reason and observation was itself revolutionary in the Middle Ages. Even if some specifics are outdated, much of Aquinas’s approach (valuing both reason and moral goodness) remains influential. Today, critics and admirers alike recognize Aquinas as a product of his time, but also as a thinker who asked questions that still matter: What can human reason discover? How are we to live? The debate over his ideasshows their enduring energy, even after 800 years.

Legacy

Thomas Aquinas’s legacy is vast. In the Catholic Church, he is commemorated every year on January 28 (his feast day). Churches, schools, and charities around the world bear his name. The Pontifical University of St. Thomas Aquinas in Rome (the Angelicum) is a major center of Thomistic studies. Popes often refer to his authority: for example, Pope John Paul II and Pope Benedict XVI praised his vision of faith and reason. Outside the Church, Aquinas’s name appears in legal theory on natural law and in philosophy discussions about metaphysics and ethics.

Academically, Aquinas remains a central figure in the study of medieval philosophy. Scholars continue producing new translations and analyses of his texts. His clear writing style and logical method help make him accessible even to beginners in philosophy. In Catholic theology, scholastic education still often begins with Aquinas. Even nonreligious philosophers note Aquinas’s rigor; for instance, many metaphysicians discuss his ideas on being and causality, and ethicists refer to his virtue-centered approach.

Perhaps one of his greatest legacies is the model of dialogue between faith and reason. Aquinas showed that one could be a devout Christian and an avid intellectual simultaneously. His thought paved the way for the later development of universities and for a tradition of academic theology. The persistence of Thomistic philosophy into the 21st century – in debates over law, morality, and science – testifies that Aquinas’s integration of different sources of knowledge continues to inspire. In a broader sense, nearly every discussion of medieval philosophy or theology has to begin with Aquinas, so his influence as “a teacher of the West” is secure.

Selected Works

Summa Theologiae (1265–1274) – Aquinas’s magnum opus, an unfinished but massive systematic theology in a question-and-answer format, covering God, Christ, sacraments, and Christian living.
Summa contra Gentiles (c.1259–1265) – A logical exposition of Christian doctrine aimed at non-believers, explaining God, creation, and morality by reason and faith.
Commentary on the Sentences (1250s) – A four-volume commentary on Peter Lombard’s Sentences, the standard theology textbook of the time, which gained Aquinas his master’s degree.
Commentaries on Aristotle – Line-by-line commentaries on several of Aristotle’s works (such as Nicomachean Ethics, Metaphysics, De Anima), helping integrate Aristotelian thought into Christian theology.
De Regimine Principum (1266–1267) – A political treatise “On the Governance of Rulers,” offering moral advice to a king, including the importance of justice and temperance in leadership.
De ente et essentia (On Being and Essence, c.1256) – A concise philosophical essay distinguishing what a thing is (its essence) from the fact that it exists, anticipating later metaphysical debates.
Quaestiones Disputatae (“Disputed Questions”) – Collections of shorter treatises responding to specific theological or philosophical questions (e.g. On Evil, On Truth) in a disputation style.
On Law, Morality, and Political Obligation – Various sections of the Summa and other writings where he defines natural law, argues that unjust laws aren’t true laws, and discusses conscience and duty.
Hymns and Prayers – Aquinas also wrote devotional works, including the Eucharistic hymns Adoro te devote and Tantum ergo, still used in Catholic liturgy.

Timeline

1224/1225 – Born in Roccasecca, near Aquino (Kingdom of Sicily, now Italy).
1230 – Sent as a child to study at the abbey of Monte Cassino.
1239 – War forces Monte Cassino to close; Thomas enrolls at the University of Naples.
1244 – Joins the Dominican Order in Naples, taking religious vows.
1244/1245 – Family detains him to prevent joining, but he is released and allowed to continue.
1245 – Sent to the University of Paris; begins studies under Albertus Magnus.
1248 – Follows Albertus Magnus to the studium in Cologne, Germany; earns first teaching posts.
1252–1256 – Returns to Paris as a Bachelor of Sentences; teaches theology and writes his Sentences Commentary.
1256 – Becomes a Master of Theology (professor) at the University of Paris (regent master).
1259–1261 – Returns to Italy; teaches in Naples and Orvieto, continues writing commentaries.
1265 – Moves to Rome as papal theologian; begins writing the Summa Theologiae.
1268–1272 – Returns to Paris as a regent master once more; continues teaching and writing.
1272–1273 – Back in Naples; writes parts I and II of Summa Theologiae.
Late 1273 – Experiences a mystical vision and abruptly stops writing (reportedly saying his work was “straw” compared to what he saw).
1274 (March 7) – Dies in a monastery at Fossanova, Italy, while en route to the Second Council of Lyon.
1323 – Canonized as a saint by Pope John XXII.
1567 – Declared Doctor of the Church by Pope Pius V, granting him an official title as a key teacher of Catholic doctrine.
1879 – Pope Leo XIII issues the encyclical Aeterni Patris, calling for a revival of Aquinas’s philosophy in Catholic education.