Thomas of Aquino (1225 – 1274) was a Dominican friar, university professor, and one of the most brilliant minds that Christianity has ever produced. Little is known about his life and times, but the few stories we do have paint a picture of a brilliant, and occasionally brilliantly eccentric, man. 

Thomas was born to a wealthy noble family near the town of Aquino in modern-day Italy. Since medieval Europeans did not have last names, we often use his town as a last name. Thus he is usually called “Thomas Aquinas” or just “Aquinas” today. Some modern scholars will refer to him as “Thomas” since that was his actual name, which has the additional benefit of making it sound as though this brilliant thinker is a close personal friend – perhaps a regular attendee at your Dungeons and Dragons game nights. 

Aquinas’s family had great plans for him. As was common for sons of wealthy families, he was expected to join a monastic order, where he would likely rise through the ranks and come to control the enormous wealth that many monasteries enjoyed. But Aquinas had a change of heart, and at age 19 he decided to join a new religious order called the Dominicans. Unlike monasteries, the Dominicans were a mendicant (traveling) order who moved from place to place and were generally quite poor. Aquinas’s family was furious. When he snuck away to join the Dominicans, they captured him and returned him to the family castle by force. They locked him in his room for about a year and hired a local prostitute to seduce him, apparently imagining this would cool his zeal for the Dominicans. Why the family thought an experience with a sex worker would convince Aquinas to take a monastic vow of celibacy instead of a Dominican vow of celibacy is anybody’s guess, but regardless Thomas was not persuaded. He grabbed a poker, heated it in the fire, and chased the poor woman around the room (being careful not to actually strike her) until she fled. She informed the family in no uncertain terms that she did not need their money. The family relented and Thomas was allowed to join the Dominicans. 

Dominicans highly valued learning, and Thomas went to study at the University of Paris with the brightest minds of his age. While at Paris, Aquinas was introduced to the work of Aristotle, whose writings had only recently become available in Latin (the predominant scholarly language of medieval Europe). Aquinas would have a lifelong fascination with Aristotle, and he is well-remembered for synthesizing Aristotle’s philosophy with the dominant theologies of his day. Thomas was apparently quite quiet and rather heavy-set, leading the class bullies to nickname him “The Dumb Ox.” One of Thomas’s teachers famously chided them that he would “fill the world with his bellowing.” 

And bellow he did. Thomas produced a remarkable body of work that is still read and reflected on today. Although I do not have space to describe all of his extraordinary theology, I want to touch on two major contributions: his doctrine of God, and his ethics. 

Aquinas is best known for his famous five proofs for the existence of God. We are not entirely sure what Aquinas meant by calling them “proofs” or demonstrations. Aquinas might not have imagined that a nonbeliever would collapse in tears and repentance at the sheer force of his logic. The “proofs” may simply be useful starting-points for students who already believe and want to reflect critically on God. 

Three of the five proofs are variations on the famous “cosmological argument,” which argues for God on the basis of various kinds of causes. In our world, things are caused by other things; I am caused by my parents, who are caused by my grandparents, etc. Now there are two options. Either this chain of causes goes backwards into infinity, or it stops with a being who causes other beings but is not caused. Aquinas thinks that the former option is impossible for a variety of complicated reasons, and so it must be that there is some being who causes others but is not caused by anything else. This being is God. The fourth argument notes that we compare things’ invisible attributes. We can say that one law is more just than another, or that one person is more righteous than another. But we can only say this if we have some maximum to compare them to. Therefore there must be a being who is maximally good, righteous, true, etc. This being is God. The fifth way is sometimes called the “argument from design.” Aquinas points out that the natural world acts in ways that seem goal-oriented. Symbiosis between animal species and the way conditions on earth seem precisely right for life to grow are but two examples. Now goal-oriented behavior is the sign of an intelligence at work. So some intelligence must be directing the world, and this is called God. 

If these are not arguments designed to convince an atheist that God exists (medieval Europe was not exactly brimming with atheists to convert in any case) but starting points for faithful reflection, we learn something very interesting about Thomas’s theology. In each of these arguments, we reflect on God by noticing the effect that God has on the world. By contrast, the arguments say very little about the kind of being God is. God is an uncaused cause, a source of order, and maximally perfect; but that is all Aquinas will say. This is intentional. Thomas tells us that we can know that God is, but it is impossible to know what God is. God’s being is incomprehensible to us. 

God’s incomprehensibility entails that we should not attribute any creaturely characteristics to God. For instance, God does not have human emotions or human thoughts any more than God has a human body. Aquinas is not saying that God is some kind of unfeeling, unsympathetic robot. Rather, he is saying that the theologian needs to treat God’s being with humble acceptance of the limits of our knowledge. Attributing human emotions or thoughts to God is ultimately a kind of projection – making God into a creature like us. The work of theology is not to pierce the mysteries of God’s being, but to faithfully describe how God operates in our lives and in the world. 

Aquinas also made important contributions to Christian ethical thought. Aquinas represents a tradition called virtue ethics that hearkens back to Aristotle. Rather than attempting to come up with a universally-applicable set of moral rules (deontology) or assuming that what is right is what produces the best consequences (utilitarianism), virtue ethics focuses on describing the character traits (virtues) that people need to acquire to behave ethically. For Aquinas there are seven such virtues. Four of them, called the “cardinal” virtues, are available to all people regardless of their faith: prudence, courage, justice, and temperance (self-control). Three of them are specifically directed toward God and hence require belief in God known through Christ: faith, hope, and love. 

As we pursue these goals, we are guided by something that Aquinas calls “natural law.” Natural law is one of the most famous (and famously controversial) aspects of Thomas’s thought. To make a long story short, Aquinas thinks that God has implanted a desire for good things and a repulsion to bad things in our souls. While this desire must be guided by the church and trained through the virtues, it prompts human beings to naturally seek out certain social arrangements and behave in certain ways that bring us closer to God. To become more virtuous, we must stay alive, and so humans seek life and avoid death. Parenting is a source of spiritual and moral growth, and so many people desire to be parents. Humans are naturally social and are commanded to love God and their neighbors, and so we naturally build societies and seek out community. 

Natural law is a controversial idea in part because it can be used to justify oppression. For example, two homosexual people in a partnership might be told they are “unnatural” because they are in a relationship that cannot produce children – in other words, they contravene the natural law that orients marriage toward childrearing. I consider myself a Thomist and think this is a cruel and incorrect thing to tell someone, but some Thomists think in this way. Regardless, Thomas’s main point is that human beings have certain built-in tendencies that help them achieve the good God has destined for them – a hopeful view of human ethical nature.  

Aquinas is one of the most important theologians today, especially in Roman Catholic circles. His importance is one of the things that makes him so difficult to understand. 

You see, in 1879, Pope Leo XIII issued a letter titled Aeterni Patris (the title just means “Of the Eternal Father,” but it sounds much more impressive in Latin). In this letter, Leo XIII stated that Thomas Aquinas’s theology was the quintessential work of Catholic thought. In fact, Leo XIII goes at lengths to tell us how all the Catholic universities that taught Thomism were wonderful, harmonious places, and that it would just be really great if there was a revival of Thomism in modern Catholic universities. Hint, hint. 

Because of this encyclical, there was immense pressure for Catholic theologians to prove that their teachings were in harmony with Thomas Aquinas. If you have spent any time around academics, you know that they do not particularly like being told what to think. So the result of this was not that Roman Catholic theologians all decided to change their thinking to agree with Thomas. Instead, they continued to teach and write about their own beliefs, and simply produced interpretations of Thomas that happened to agree with what they already thought. Some theologians who genuinely agreed with Aquinas produced very thoughtful and insightful interpretations. In other cases, theologians produced breathtakingly poor interpretations that do not hold up under close scrutiny but allowed them to claim that Aquinas was on their side. So if you read about Thomas, it is very important to choose a good interpreter. One excellent Thomist who writes in plain English is Herbert McCabe. God Matters is a good place to start learning about a Thomist’s view of reality. Denys Turner’s Thomas Aquinas: A Portrait is another excellent book.  

Still, the best way to become acquainted with Aquinas is to read him for yourself. You can find his primary works – the Summa Theologiae and Summa Contra Gentiles – online in English for free. Most of Thomas’s works are structured in question-and-answer format. Thomas will pose a question. Then, ever the gentleman, he first lists out all the reasons why you might disagree with him. Once he has listed those out, he states his own position and all the reasons he believes it to be correct. Aquinas is a dense writer, and you are likely to find his work slow going at first. Aquinas will never just tell you what he thinks. He will also tell you what those who disagree with him think, and why. But whether you agree with him or not, you will learn much from his thoughtful and detailed writing. He will show you how he thinks about God – and in the process of studying him, it’s hard not to find yourself a better theologian no matter your conclusions. 

Thomas Aquinas gave opposing views a say in his writings because what mattered to him is what matters to every theologian worth their salt. He cared more about knowing the real God than defending his opinions about God. In fact, Thomas Aquinas’s greatest work, the Summa Contra Gentiles, was left unfinished for this reason. The story goes that one day Thomas was writing when he was overtaken by a sudden mystical vision of God. Afterwards he reportedly said, “I can write no more. After what I have seen, all my writings look like straw.” The church has since found plenty of gold in that self-described straw, not least of which is its author’s insistence that no word or doctrine can ultimately encompass the mysterious, overabundant Goodness that it attempts to describe. Our churches would be healthier, and our doctrines truer, if we all kept in mind that singular truth.