 Hi, I'm Peter Adamson and you're listening to the History of Philosophy podcast, brought to you with the support of the Philosophy department at King's College London and the LMU in Munich, online at www.historyoffilosophy.net. Today's episode, The Ox Heard Round the World, Thomas Aquinas. Albert the Great was a keen-eyed observer, not only of nature but also of talent. His classes were attended by a young man of quiet disposition who was, shall we say, big-boned. The other students called him dumb ox. But Albert was impressed by him and, so the story goes, remarked that this dumb ox would one day produce such a bellowing that it will be heard throughout the world. And so it has proved. That student, Thomas Aquinas, would become the most famous medieval philosopher, to the point where he almost needs no introduction. In this episode, I'm going to introduce him anyway by looking at his life, his works, and his approach to the vexed question of how Aristotelian philosophy could be made compatible with Christian theology. Like most of the 13th century thinkers we've met, Aquinas plied his trade in a university setting and wrote, indeed no doubt thought, using the Scholastic Method. Born in the mid-1220s, he came from a wealthy family in Naples. He was first educated at the Abbey of Monte Cassino. Bonus points if you remember that name. Monte Cassino was also the home of the recipient of Peter Damian's letter on restoring virginity covered back in episode 203. Aquinas didn't need to have his virginity restored. A famous anecdote has his brothers seeking to dissuade him from signing up to the Dominican order, sending a prostitute to show young Thomas what he'd be missing out on. Aquinas simply chased her away. Like most students of the age, Aquinas was only a teenager when he began his university training, in his case at the University of Naples. He joined the Dominicans in the early 1240s, over his family's creatively expressed objections, and escaped from their influence when he moved to Paris in 1244. His further studies also brought him to Cologne, where he worked with Albert the Great, but it was in Paris that he became a master of theology in 1256. This inaugurated the first two stints at Paris. At other times we find him working at Dominican priories in Ovieto, Rome, and back in Naples before dying in 1274 while en route to a council at Lyon. Given that he lived to be only about 50 years old, Aquinas's output was prodigious. His most famous work, the Summa Theologiae, is a sprawling text which remained unfinished at death, but still contains three sizable sections, with the second subdivided into two parts. It was only the third of three synoptic works that covered the whole of theology, the first being his commentary on the sentences of Peter Lombard, written, as was standard, upon his taking up the post of master at Paris, and the second being his Summa Consurgentiles. There is some debate about what, if any, title Aquinas himself gave to that work, and how it relates to the Summa Theologiae. The consurgentiles of the traditional title would mean against the non-Christians, and it has been read as a manual for use in converting Muslims and Jews in Spain. But if so, it seems odd that Aquinas devotes so much space to arguing for ideas that Jews and Christians would readily have admitted, such as the existence of God. Rather, the summa consurgentiles may have been an attempt to show how Christian belief can be placed on rational foundations, a project of at least as much interest for Aquinas's fellow Christians as for representatives of other faiths. Only in the fourth and final book does Aquinas turn to aspects of the Christian religion that cannot be established by rational argument, like the doctrine of the Trinity. The consurgentiles is also noteworthy in that it simply lays out arguments one after another, rather than using the disputed question structure of the more famous Summa Theologiae. With this structure, the Summa Theologiae imitates classroom disputation, though in a streamlined or idealized fashion. Aquinas also held a number of actual disputed questions, with each question containing a large number of arguments for or against the various theses being considered. The Summa is different. Its three parts deal respectively with God, humankind, and Christ. These parts are then divided into numerous questions, each of which contains a number of articles, and it is within each article that the disputed question structure comes to the fore. Each article usually gives only a small number of objections, mostly drawn from authoritative sources, before citing another such source against these objections, introduced by said contra, on the other hand. This is followed by a response in Aquinas' own name, and finally he gives answers to the objections to the extent that these are not already obvious from his response. The cited authorities are carefully chosen. Aquinas uses them to show how Christian sources like Augustine, the Greek church fathers, and the Bible itself can be integrated with Aristotle and other philosophical sources, like the Muslim thinkers Avicenna and Ivarroes, and the Jewish Maimonides. Platonist sources are also important for Aquinas. He continues to use the book of causes, even after realizing that it is based on Proclus rather than Aristotle, and he is also powerfully influenced by the pseudo-Dionysius. It's even been suggested that the whole Summa has a structure inspired by the Neoplatonic theme of precession and return, beginning from God as the first cause of all things, and then following the path that leads back to him through the virtues and the grace offered by Christ. Alongside the three Summas and his sets of disputed questions on topics like virtue, truth and evil, Aquinas' commentaries give us another sign of his intellectual inheritance. He commented on books of the Bible and on works of Christian and non-Christian Platonism, including two treatises by Boethius, The Divine Names of the Pseudo-Dionysius and The Book of Causes. Finally, he followed his teacher Albert's example by writing several commentaries on Aristotle. As this choice of subjects already suggests, Aquinas saw no unbridgeable chasm between reason and religion. Such a harmonizing view was, of course, as typically medieval as knights in shining armor, or alarmingly low standards of sanitation. From rationalists like Abelard to mystically-leaning Augustinians like Bonaventure, we've found widespread agreement that Aristotle and other philosophers could at least be reconciled with the Christian faith. But Aquinas proposes a new way of conceptualizing this relationship. He defines very clearly the differences between theology and philosophy, a methodological distinction that reflects the division between the theology and arts faculties within the universities. We see this in a commentary written during his first period in Paris devoted to Boethius's On the Trinity. It does not cover most of the text, and in fact doesn't really get to the part about the Trinity, instead lavishing attention on Boethius's remarks concerning philosophical method. Aquinas's commentary explains Boethius's meaning line by line, but then steps back to consider the issues at stake by raising a number of difficulties which are handled using what else? The disputed question structure. Already in the prologue to his commentary, Aquinas points to a difference between the method of philosophy and that of theology. The philosopher begins with things in the created world and proceeds to God, whereas the theologian goes the other way around. But the difference is more than direction of travel. The philosopher moves along the lower road of natural reason. He must base himself solely on what he can glean from the senses, since all natural reasoning must have recourse to experience of the physical world. Many, even most, of Aquinas's contemporaries would have said that even this sort of reasoning depends on an illumination from God. We've seen how Bonaventure, among others, thought such illumination was indispensable for the certainty of a philosophical demonstration. Aquinas disagrees. The light of reason is derived from God, but this is given to us automatically when we are created as humans, and for the most part no further assistance is needed. The human intellect is itself active and can illuminate the images it derives from the senses so as to understand them. It is only when we try to understand such supernatural themes as the Trinity that an additional light must be added. But this does not mean that God is entirely out of bounds for the philosopher. Several times Aquinas cites what may be his very favorite line from the Bible, The invisible things of him are clearly known from the creation of the world, being understood by the things that are made. That's Romans 1.20. Aquinas takes this to indicate that the philosopher can indeed know God, but only indirectly. Natural reason approaches God as the cause of created things, rather than grasping Him in himself as we hope to do in the afterlife. The philosopher cannot offer demonstrations that divulge God's essence, if only because we demonstrate things on the basis of their causes, and God has no cause. The Trinity is a good example of this limitation. In himself, God is indeed three in one. But we can never come to know this naturally, because with our inborn resources, we grasp God only as a cause, and it is the whole Godhead that creates things, not only one or the other divine person. Nonetheless, philosopher can offer several services to religion. It can help the Christian to refute false criticisms of religious doctrine, the task known as apologetics. And it can offer a deeper understanding of something accepted on the basis of faith. It should be underlined that this does not mean proving the articles of faith. These are believed on a voluntary basis, thanks to another supernatural light infused within us by God during this life, which is what Aquinas fundamentally understands faith to be. Rather, Aquinas has in mind the sort of procedure used by Augustine or Boethius, as when Augustine used philosophical tools to show us that the inner workings of our own mind give us some inkling of God's Trinitarian nature. A final task for philosophy is establishing what Aquinas calls the preambles of faith, things that pave the way for religion but are accessible to natural reason. Among these, none is more central than the very existence of God. Aquinas is adamant that even if the philosopher cannot demonstrate what God is, he can demonstrate that God is. For further light on all this, we can do no better than to turn to the beginning of the Summa Theologiae. As the title implies, this is nothing less than a comprehensive study of theology, and Aquinas begins by explaining the nature of his enterprise. Theology is, he insists, a science, and a science in the Aristotelian sense. That is, it offers demonstrative proofs based on unshakable first principles. The difference between theology and other sciences is that those principles are not available to human reason itself. How then can theology be a science at all? To answer this question, Aquinas reminds us of a teaching found in Aristotle's posterior analytics. One science can take over as principles things established in another science. The study of optics might require the principle that parallel lines never meet, and this is something shown in a higher science, namely geometry. Likewise, the human science of theology takes its principle from a higher science, namely the self-understanding of God himself and the understanding that the blessed have of him in the afterlife. Here, it helps to know that the Latin word sciencia is a bit more flexible than our word science. Like Aristotle's Greek term episteme, it can mean a branch of knowledge like optics or theology, but it can also mean knowledge or understanding. Thus, it is natural for Aquinas to say that God's sciencia provides the principles of the sacred sciencia, that is theology, the way that one human sciencia or science grounds another demonstrating its principles. But whether we are speaking English or Latin, we may worry that no article of faith could ever be the basis of a rational science. We typically assume today that faith is antithetical to reason. Faith is belief that one embraces on the basis of authority, or by a sheer act of will, or just because one was brought up in a religious family. It is, in other words, the sort of belief that involves the absence of rational justification. In a sense, Aquinas could agree. He admits that in this life, humans have no direct access to the certain truths that ground theology. Those truths are as certain as truth comes, since we are talking here about nothing less than God's own knowledge of himself. The theologian is like the optician who doesn't understand geometry, who we might say takes it as a matter of faith that parallel lines won't meet in the end. Likewise, the theologian, like the optician, operates with perfectly certain principles. It's just that he doesn't himself understand why they are certain. This is, of course, unlikely to satisfy the atheist, but Aquinas isn't talking to atheists, he's talking to fellow Christians, in fact, to students of theology. We should bear this in mind as we turn to the next topic of the Summa, namely the existence of God. Aquinas told us in his commentary on Boethius that the philosopher can use natural reason to prove that God exists, though not to understand what God is. Thus, we might expect the proofs Aquinas offers here to be intended as knockdown demonstrations. If so, we're apt to be disappointed. In a set of famous arguments often called the Five Ways, Aquinas describes five ways of establishing that God does in fact exist. These are some of the most thoroughly discussed arguments in the history of philosophy, and if all that discussion has shown anything, it is that the arguments need a lot of help if they are to be made watertight and convincing. For this reason, I tend to sympathize with readers who see the Five Ways in the context of theology, as Aquinas understands theology. Remember that philosophy offers the theologian various services. This includes proving certain preliminary points, which could certainly include the existence of God. But it can also help us to understand things we already accept on the basis of faith, and you can be sure that these would most definitely include the existence of God. So it may be better to think of the Five Ways as offering the theologian a set of rational approaches for thinking about God, even if they are also intended to work as proofs. This could help to explain their relative sketchiness and the various holes one can easily poke in the argumentation. As Aquinas scholar Rudi de Velde has put it, What Aquinas is saying is like this. Although there are several objections to the assumption that God exists, which should be taken seriously, we Christians firmly hold that God is existent. Now granted that this is true, as we believe it is, let us then try, with the help of arguments found in the philosophical tradition, to show how the human mind may be led to an understanding of this truth. Having said that, it is also important that Aquinas thinks we can and should try to prove that God exists. It is not simply obvious, or as he puts it, known through itself, that this is the case. This is one of those places where Aquinas is signaling his departure from the mainstream. Most 13th century thinkers followed Augustine, who held that it is simply incoherent to argue that God doesn't exist. A typical Augustinian argument to this effect was that God is truth, and it is self-defeating to deny that there is truth, since, to do so, you'd have to say that it is true that there is no truth. This sort of reasoning had been used by Anselm, who was of course responsible for an even more famous attempt to show that God's existence simply cannot be denied. This was his ontological argument, which Aquinas interprets as trying to establish that God's existence is self-evident. For Aquinas, the argument fails, because it concludes from what must be the case in our minds to what must be the case in external reality. Though Aquinas does put his finger here on a feature of the argument that makes people uncomfortable, I don't think it is a good objection. After all, the whole point of Anselm's ontological argument is to move from our idea of God to God's real existence. Aquinas simply rules this out as an illegal kind of inference. This amounts to stipulating that the ontological argument doesn't work, rather than pinpointing where exactly the flaw in Anselm's reasoning might be. If God's existence is not self-evident, how should it be established? On the basis of sense perception, of course, since it is on the basis of the visible, created world that the invisible must be known. Each of the five ways duly takes its departure from a feature of the world of sense experience. Take the first of the ways. It argues that every motion depends on some cause which moves it. That mover might in turn be moved, as when I move a stick that moves a rock. But the chain of movers cannot go on forever, since without a first unmoved mover, the chain of movers could never begin. Thus, there is a first mover, which Aquinas blithely adds, everyone understands to be God. You see what I mean. The argument has more holes than the plot of a movie about the invention of Swiss cheese. How do we know that something can't move itself, as when I get up from the sofa to fetch a drink from the kitchen? And why isn't it good enough to have a chain of moved causes, each of which is moved by the previous cause into infinity? Or take the third of the five ways, which is probably the most mystifying. Here, Aquinas asks whether it could be the case that all things are merely possible or contingent. No, because a contingent thing can fail to exist. So if all things are contingent, then at some point everything would have failed to exist. But that is absurd, because if everything had been non-existent in the past, then nothing would exist now. It follows that not everything is contingent. Instead, there must be a necessary being, and again, this is what everyone understands to be God. And again, the argument looks almost painfully bad, especially the bit where he infers that if each thing could fail to exist, then at some point all things must fail to exist. Aquinas may be assuming as an unstated premise something called the Principle of Planitude, that every genuine possibility is realized at some point. If it is genuinely possible for all things to be non-existent, as surely it is if each thing individually can be non-existent, then at some point this must happen. As for why he might just assume the Principle of Planitude without saying so, we might think Aquinas is depending on Aristotle's endorsement of the Principle. Or perhaps he'd have us turn to Avicenna, whose own more elaborate proof of the necessary existent is lurking in the background. A similar game can be played with the first way. In that case, we might seek answers in Aristotle, who is the inspiration for Aquinas's argument, or elsewhere in Aquinas, by looking to his theory of action to see why absolute self-motion is impossible. Of course, we might also use our own ingenuity to improve the arguments. Plenty of people have done so. But a more sensible reaction might be to assume that the student is familiar with these types of argument from studying their Aristotle and their Avicenna, and is just being reminded of several philosophical approaches to God that can be invoked in the rest of the Summa. To quote another Aquinas scholar, Brian Davies, "...the purpose of the five ways is to set the ball rolling, not to bring the game to an end." Of course, we are ourselves only just getting the ball rolling with Aquinas. In coming episodes, we'll look more at his conception of God, as well as his ethics and political philosophy. But next time, we'll be turning to one of the issues on which he was most out of step with his contemporaries, the nature of the human soul. Join me for what should be a pretty animated episode of The History of Philosophy, without any gaps.