Post-classical history

How Pagan Science was Christianised

The Dominicans had realised that while Aristotle’s philosophy could be dangerous, it was also very useful in the battle with heresy. They needed to combat the extremists on both sides so that they could use pagan ideas for the benefit of Christianity. It is no surprise to find that the two biggest guns in the battle for Aristotle were Dominicans. More than anything else, it was the work of this pair of scholar-saints, Albert the Great (c.1200–80) and his most celebrated pupil, Thomas Aquinas, that made Aristotle not only respectable but essential to Christian theology. As a contemporary wrote of them, ‘Doubtless many others were famous during this same time both in life and thought. But these two transcended and deserve to be placed before all others.’1

The Universal and Angelic Doctors

Albert the Great was born in a region of south-western Germany called Swabia and joined the Dominicans as a young man. The order was attracting many brilliant men and Albert wanted to be part of the exciting new thinking that it had spawned. He spent his career at the university of Paris and at Cologne, where he was partly responsible for the foundation of a new university. His tomb can still be found in the crypt of Cologne’s fine St Andreas church. Commemorated as one of the greatest of all German thinkers, Albert had to wait until 1931 before the Catholic Church finally declared him a saint. He acquired the honorific ‘the Great’ during his own lifetime by virtue of his enormous appetite for learning and the sheer size of his output. The standard edition of his collected works fills 38 capacious Latin volumes.2 His marvellous mind scrutinised everything under the sun, and he questioned and analysed all that he read. His books covered the Bible, the early Church fathers and, above all, Aristotle’s natural science and natural history. It is little wonder that Albert earned the title of ‘Universal Doctor’.

All this knowledge came at a price. Almost inevitably, Albert gained a reputation as a magician among the common people. Rumours even claimed that he had inherited Gerbert’s talking brass head and used it to gain illicit knowledge. In fact, Albert did write some suspect works and his infamy in this respect was not completely undeserved. The contemporary book Mirror of Astronomy takes a very liberal line on the permissibility of magic and may well have been written by Albert himself.3

Although he based his philosophical work primarily on the books of Aristotle, he was not an uncritical admirer. He warned, ‘If Aristotle had been a god then we must think that he never made a mistake. As he is a man, he has certainly made mistakes just like the rest of us.’4 Albert also restated some important principles about natural philosophy. ‘Experience’, he explained, ‘is the only safe guide in such investigations.’5 We need to be careful, however, not to overemphasise the originality of Albert’s remark. It did not mean that he performed experiments. ‘Experience’ meant passive observation rather than active interrogation. For him, investigating nature was a rational and literary activity more than an empirical and practical one. Often, it involved reading the works of many authorities and judging between them. That said, he did from time to time insist that his own experience contradicted Aristotle who must, therefore, have been mistaken. Even the Philosopher’s authority was sometimes suspect. ‘It is the task of natural science’, Albert said, ‘not simply to accept what we are told but to enquire into the causes of things.’6 In other words, as William of Conches had realised, natural philosophy is about discovering natural secondary causes. Albert was clear that the existence of miracles did not prevent the natural philosopher from doing his work.

After noting all his achievements, we must accept that Albert’s fame rested squarely on how much he knew and not what he did with all his knowledge. His learning was wider than it was deep and he could sometimes appear more as a collator of facts than as someone who was pushing back the boundaries of scholarship. There is no system of philosophy named after him and he is largely unknown outside his native Germany. On the other hand, Albert’s treatises were systematic and he did lay foundations for the assimilation of the mass of newly translated Greek philosophy. Perhaps his greatest achievement was to recognise and nurture true genius when he saw it. His most gifted pupil ranks as one of the most famous philosophers who has ever lived, and today we still recognise him as a truly revolutionary thinker. That man was Thomas Aquinas.

Whereas Albert had to wait until the twentieth century to be canonised, Thomas Aquinas was made a saint less than 50 years after his death. He was a humble and devout man, as no one doubts, but he owes his canonisation to his phenomenal works of philosophy and theology. They have been one of the intellectual bulwarks of Catholicism ever since, to the extent that the Church has awarded him the title of ‘Angelic Doctor’.

Thomas Aquinas had the best possible start in life. He was born in central Italy and was closely related to more than one royal family. A quiet and rotund boy, he was clearly unsuited to life as a soldier, so his family mapped out a career in the church for him. Bishops were as powerful and respected as secular rulers, so the clergy was an acceptable profession for such a well-born individual to enter. He could even be a monk without any impropriety. As a member of the Benedictine order, he would live in the luxury of a rich monastery and be a mover and shaker in society. In preparation for such a role, his parents sent him to the university of Naples for the requisite education.

Once there, however, Thomas did not act as his family wished. His piety was entirely genuine and he demonstrated it by joining the Dominican order. This was an entirely different matter to becoming a Benedictine monk. Instead of being a prince of the Church, he had entered into a life where he could own nothing and even had to beg for his food. His family were not amused, and his mother ordered his older brothers to abduct their wayward sibling. They imprisoned him in the family castle. Even shut up in a darkened room to think things over, Thomas refused to change his mind. According to a story told by his earliest biographer (and also a noted inquisitor) Bernardo Gui (c.1261–1331),7 the family went as far as to hire a prostitute to persuade him of the virtues of sin. Thomas threw her out of his chamber.8 Eventually, the family relented and Thomas continued in his vocation. Wisely, the Dominicans moved him well away from Italy to be educated by Albert the Great in Cologne.

Thomas, the chubby and taciturn newcomer, did not impress his fellow pupils and they dubbed him a dumb ox. Albert was a better judge of academic potential. ‘We call this lad a dumb ox’, he said, ‘but I tell you that the whole world is going to hear his bellowing.’9 So he invited his quiet student to come with him to the intellectual capital of Europe – the university of Paris. Once there, Thomas rapidly made a name for himself as a thinker of serious note. He received his doctorate in theology from the Paris faculty in 1257 before embarking on a life of teaching, preaching and writing. Avoiding the honours with which the church attempted to shower him, most notably the archbishopric of Naples, he remained a simple friar until the end of his days.

As we might expect for a man so esteemed by the church, there are plenty of stories about Thomas that fill out the rather meagre official record of his life. A couple of these bear repeating even if not entirely true, because they reflect contemporary perceptions of the man. While still a student of Albert the Great, it is said that one of Thomas’s peers took pity on him and assumed by his silence that he was having trouble following a lesson in logic. The kind student sat down with Thomas after class to run through the work so that the dullard might not fall too far behind. Thomas suffered the indignity with patience as his conscientious tutor laboriously explained matters that the future saint had mastered years earlier. Eventually, after the student had made an obvious error, Thomas politely intervened and stopped his would-be master in full flow. He proceeded to offer a far more lucid exposition on the point than even Albert the Great himself had achieved. Word quickly got around that Thomas Aquinas was not in need of remedial classes.10

Much later, while Thomas was a professor at the university of Paris with his reputation secure, King Louis IX (1215–70) invited him to a great banquet. Louis was later canonised himself, at least in part for his unsuccessful efforts as a crusader. Without much enthusiasm, Thomas politely attended the feast but took no part in the conversation. Soon he was lost in thought. Indeed, he quite forgot where he was and, upon receiving a sudden insight into an obscure problem that had vexed him, slammed his fist into the table and cried out aloud, ‘That’s it!’ An uncomfortable silence greeted this outburst, and all eyes turned to the king to see what his reaction would be. Luckily, His Majesty was aware that scholars needed to be indulged and so merely ordered that quill and parchment be brought to the table so that Thomas’s untimely thoughts should not be lost to prosterity.11

As soon as he became a professor of theology, Thomas was thrown into the latest wrangle about Aristotle that was raging in Paris. This time, the argument hinged on the work of ‘the Commentator’ on Aristotle – the Arab scholar Averröes. Christians had come across many of his works at the same time as they had been translating Greek philosophy into Latin. He was a Muslim who had lived in Islamic Spain during the twelfth century, at least when not in exile as a result of his radical ideas. He based his philosophy firmly on Aristotle and in some ways went even further. For instance, he suggested that the universe was completely deterministic. In other words, we have no free will and hence no moral responsibility. He also agreed with Aristotle that the universe had to be eternal and that there was no life after death.12 These were exactly the sorts of ideas that had got Amaury into so much trouble. Merely discussing them was fine, but what you could not do was say that they were true. Averröes said they had to be true. This emphasised Aristotle’s idea that the laws of nature are necessary and even constrain God’s freedom of action. Averröes was certainly not content for philosophy to be a handmaiden of theology. Reason, he implied, trumped faith every time.

Thomas Aquinas’s Scholastic Method

Thomas Aquinas was the prime exponent of the extremely methodical and carefully organised system that medieval philosophers used to construct rational arguments. Today, we call this mode of argument the ‘scholastic method’ and hence the entire body of medieval thought is often described by the single word ‘scholasticism’. We can see what this means in practice by way of an important example taken from the thought of Thomas himself: his attempt to prove that God exists.

A scholastic argument almost always begins with a question and so near the start of his greatest work Summa Theologiae, Thomas Aquinas asks ‘Does God exist?’13 Rather than launching himself immediately into explaining why he thinks God does exist, Thomas, in typical medieval fashion, first sets out a couple of arguments for the nonexistence of God. Although he is very brief, the two arguments he chooses to use are strong ones. The first is the problem of evil, which states that if God existed there should be no such thing as evil. An all-powerful and good God should be able to ensure that no evil would exist, whereas clearly it does. The second of Aquinas’s arguments for atheism is that the concept of God does not explain anything. We can use science to understand everything about the world and so we do not need to postulate a God.

The next stage is to state the contrary to the arguments for atheism. This is not a counter-argument, just a statement that Thomas intends to defend summarised by a quotation from the Bible or some other authority. In this case, it is that God says in Exodus 3:14 that he does exist.

Only now do we get to the meat of the argument. Thomas presents us with no less than five proofs for the existence of God, known to philosophers as the ‘five ways’. Thinkers have been arguing about them ever since. While his five proofs, like the ontological argument of St Anselm, are not finally convincing (or there would be no such thing as an intelligent atheist), they did help demonstrate to Christians that reason was their friend and not something they needed to be afraid of. If they could use rational arguments to show what they believed by faith, then rational arguments were a course well worth pursuing. Here we will restrict ourselves to a combination of the first and second of Thomas’s arguments because they give a good idea of how his mind worked.

Taking his cue from Aristotle, Thomas insisted that every effect in the world must have a cause. Things cannot happen for no reason at all. However, Thomas realised that this approach led to a problem because as soon as you have determined the cause of an effect, you have to ask what the cause of that cause is. Even if you can find that out, you are still faced with an infinite series of causes going back forever.

A modern example can illustrate the problem.14 Imagine a car is stuck at the traffic lights at Trafalgar Square in London. These take an inordinately long time to change from red to green and London traffic being what it is, if you are at the front, a large queue often builds up there. Suddenly a van shunts into the back of the car and causes a dent. The driver of the car gets out in order to remonstrate with the van driver and obtain his insurance details, but finds that he is already remonstrating with the driver behind him. It turns out that the van shunted into the car because the vehicle behind the van had run into it. Likewise, the same thing had happened to the next car back in the queue and so on. Imagine that London traffic has now become so bad that the queue is infinitely long. As far back as it is possible to go, everyone has been shunted into the car in front of him or her by the car behind. What makes this doubly unfortunate is that although the repair bills and aggravation are also infinite, there is no one responsible for the initial shunt because the queue has no end. Clearly, Thomas would have said, this is impossible. Without an initial cause, there could never have been any effect. There has to be a first car colliding to begin the whole chain of events.

Thomas reasoned that this must always be the case: everything is caused by something else, and so there must be some first cause that set the ball rolling. Otherwise, nothing should happen at all. However, we have already stated that everything in the world has a cause. So we must conclude that the first cause, the first movement, came from outside the world. That supernatural cause is what Aristotle called the prime mover and Thomas Aquinas called God.

Thomas rounds off the question of God’s existence by briefly responding to the objections that he started with. He replies to the problem of evil by claiming that God’s greatness is such that he can draw good even from evil. Finally, he reiterates that the laws of nature require a ‘first cause’, that is God, to explain them. Thus, according to Thomas, science can never explain everything.

Averröes versus Aquinas

The most prominent Averröist at Paris while Thomas was teaching there was Siger of Brabant (who died around 1282), a radical philosophy professor who had gathered a group of like-minded students around him. Siger was a combative character who was fully involved in the rough-and-tumble of university politics. His name first appears in the records when he took part in an attempt to kidnap a rival. He also played a leading role in the conflicts between students of different nationalities that took place in the 1260s.

His philosophy was just as controversial. He could not resist the more radical interpretations of the work of Aristotle and Averröes, believing that philosophy proved that the earth must be eternal and that humans lack individual souls. We are, Siger said, all part of a single hive-intellect that animates the rational faculties of the entire human race. Of course, he could not safely say that these conclusions were actually correct, so had to content himself with claiming that reason demonstrated their truth. Contrarily, he continued to assert that we can know by faith that, in reality, God did create the world and that each man does possess an immortal soul. In other words, Siger claimed that reason said one thing and faith said another. This flew in the face of Christian orthodoxy, which stated that the two could never conflict because both came from God. Echoing St Augustine and St Anselm, the Church believed that reason illuminated faith and you could not have one without the other.

Worse was to follow. Some of Siger’s disciples allegedly claimed that when reason and faith conflicted, they were both true! Thus, in the philosophical sphere, the world was eternal and in the theological sphere, God created it. This was called the doctrine of the two truths. The bishop of Paris roundly condemned the idea as complete nonsense.15 If faith and reason seemed to conflict, he thought, it was down to human error. In 1270, he issued a decree outlawing some Averröist ideas. Siger then apparently recanted and returned to lecturing.

Thomas Aquinas’s interventions in the great debate at Paris over Averröism were hugely significant. He was determined to show that he could make Aristotle into a servant of Christianity, and also to demonstrate that Siger was wrong to claim that reason led to conclusions in conflict with the faith. Thomas wrote direct rebuttals to some of Siger’s work but concentrated on producing his own synthesis of Christian and pagan philosophy. This found its definitive expression in his Summa Theologiae. It is a massive work and, despite the fact he never quite finished it, remains the highest achievement of medieval scholarship. What he achieved was such a successful amalgamation of Aristotle’s philosophy with Christian doctrine that some Catholics have since failed to distinguish between the two.

Thomas combined an enormous respect for non-Christian authorities with his reverence for the Church fathers. As well as Aristotle and Averröes, Thomas found inspiration in the writings of Moses Maimonides (1135–1204). Maimonides was the most renowned Jewish philosopher of the Middle Ages and spent all his life living under Islamic rule. He wrote his most important book, The Guide for the Perplexed, for a student who was having trouble reconciling what he had learnt about natural philosophy with the words of the Bible. As Maimonides explained in his introduction:

The object of this treatise is to enlighten a religious man who has been trained to believe in the truth of our Holy Scriptures, who conscientiously fulfils his moral and religious duties and, at the same time, has been successful in his study of philosophy.16

Thomas Aquinas thought that his problem was the same. He had to reconcile the Averröists, who believed philosophy was supreme, with their opponents, who thought it was dangerous. Like Maimonides, he united the two sides and showed the value of both. Thomas gave human reason a great deal of credit. While he did not hold that the existence of God was self-evident to the human mind, he did believe that unaided reason could rationally prove God existed.17 He also thought that we could discover a great deal about the world around us. However, there are limits to reason. When it comes to properly understanding the mysteries of the faith, such as the Trinity, we also need supernatural illumination. Actually to know for certain that Christianity is true is, for Thomas, a gift from the Holy Spirit and not something we can ever achieve by ourselves.18

For natural philosophers, reason was the correct tool and Thomas showed how they could make best use of it. According to him, the world was real and it was subject to cause and effect. Things did not happen without any reason but behaved in predictable ways. Thus, it was worthwhile to study causes. Of course, Albert the Great’s opinion had been that causes were the whole point of natural philosophy. In particular, Thomas stood up for the doctrine of secondary causes as a valid way for a Christian to investigate the world. He did not accept that it was impious to say that a plague was caused by a disease rather than attributing it directly to the will of God. Nor did he think the world was evil. After all, it had been created by God and he could not do anything wrong. Aristotle had said that the world must be eternal, but Thomas showed how the Greek’s arguments were flawed. However, he admitted that he could not prove conclusively that God created the universe because of the limits of human reason. So, according to him, we must look to the book of Genesis to find the truth. Thomas also stood against determinism and in favour of human free will. Against the Averröists, he believed that humans each have their own souls.

Siger and Thomas aimed several of their tracts at each other before Thomas left Paris and returned to Italy in his last years. Shortly before he died, he had a mystical experience while at prayer that caused him to give up writing. He declared that all he had achieved was mere chaff, at least compared to the vision of God’s glory which he had experienced. Few have agreed with Thomas’s own assessment of his work.

The Condemnations of 1277

After Thomas Aquinas left Paris, Siger and his students continued to make trouble with their radical theories. In a new effort to end the dispute, the university instituted a reform that aimed to separate the warring factions. As we have noted, much of the trouble for the Church in accepting the work of Aristotle was down to the lack of a clear border between philosophy and theology.

Thomas Aquinas had gone some way towards providing that border, because he was always clear about what could be known through reason alone and what requires faith. Just to be on the safe side, the university of Paris required philosophers to agree that they would not meddle in matters of theology. From 1272, new graduates had to swear that they would never argue about sacred doctrines and, if they had to mention them, they would always come down on the side of orthodoxy.19 From a medieval point of view, this was a sensible and understandable arrangement. Already in the thirteenth century, lawyers and doctors were taking action against amateurs who professed knowledge in their fields of expertise. Everyone agreed that theology was by far the most important and highly skilled profession of all. Only the most rigorously trained individuals could practise it. It took seven years to qualify as a theologian and that was after having spent at least four years working on a first degree. No wonder theologians were jealous of their prerogatives. If a philosopher did want to tackle matters of faith, then he was perfectly entitled to join the theology faculty and train as a theologian.

By 1277, it was clear that not even this reform had ended the trouble. The ideas of Averröes had continued to spread, perhaps because existing graduates did not have to take the new oath. Taverns and inns echoed with arguments between rival factions. The row threatened the reputation of the university as well as its unity.

Siger had decided that the situation was simply too dangerous for him to remain. The local inquisitor was pursuing him for questioning, although Siger was never convicted of heresy, even in absentia.20 He travelled to Italy, possibly seeking to take the matter up with the Pope. It is unlikely that the Pope in question, John XXI (c.1215–77), would have been very sympathetic. He had already written to the bishop of Paris demanding that he do something about Averröism. It is worth noting that before he became Pope, John XXI (then called Peter of Spain) had been a student at Paris himself. In the course of his academic career, he wrote the textbook on logic that dominated the field until the close of the Middle Ages. He also trained as a physician and occupied the chair of medicine at the university of Sienna. A medical handbook attributed to him was enormously popular. Certainly, this Pope had no problem with the proper application of reason. On his election, he had a private study added to the papal palace in Viterbo near Rome so that he could get on with philosophical research in his spare time undisturbed. Sadly, after less than a year as Pope, John XXI was killed in a freak accident. He had been working in his new study when the roof collapsed on him.21

The bishop of Paris, even before he had received the Pope’s letter, set about compiling a list of all the things that he found objectionable about Siger’s and Averröes’ ideas. It turned out to be quite a long list – 219 propositions were condemned in all. The document forbade anyone at the university from teaching or holding any of the condemned opinions on pain of excommunication. As for Siger, for reasons unknown he was murdered by his secretary. After his death, he enjoyed a reputation as an important thinker, cemented by Dante Alighieri, who placed him in paradise in the Divine Comedy.22

The 219 condemnations of 1277 hold a very important and controversial place in the history of science. The main point at issue was whether God was constrained by natural laws himself or whether he was above them. The condemnations themselves are fairly confusing to read because they consist of a list of things that people were not allowed to say, rather than setting out what people should believe. Several of the condemned statements deal with specific cases where God is not to be restricted. For instance, among the now-heretical statements were that God ‘could not make several universes’, that he could not ‘move the universe in a straight line lest a vacuum result’, nor ‘make more than three dimensions exist simultaneously’. The bishop of Paris summed up the condemnations by prohibiting anyone from saying that ‘God cannot do anything that is naturally impossible.’23

Nobody, as far as we can now tell, thought that God had actually created extra universes or that there really were more than three dimensions. That wasn’t the point. The bishop of Paris was just telling everyone that they should never say never. Science could not make final pronouncements, especially those that limited the freedom of God. This meant that the bishop was not stopping people from investigating how the world worked, he was merely preventing them from saying that God was constrained in how he could organise the world. Rather than restricting the work of natural philosophers, the condemnations actually freed them up. They no longer had to doggedly follow Aristotle, but could invoke God’s freedom to do things differently and develop theories outside the Aristotelian paradigm. We will see in the following chapters that they leapt at the chance to explore these possibilities.

Of the remaining banned propositions, several asserted that the world had not been created by God and that it was eternal. Others questioned human free will and moral responsibility. A few give us an idea of just how bitter the war of words between the Averröists and the theologians had become. Among the condemned statements were ‘Theology is based on fables’ and ‘You can’t learn anything from theology’.24

Reading through the 1277 condemnations, it is clear that they were written in a hurry. They are chaotically ordered and appear to be the product of some sort of ecclesiastical brainstorming session. No one sat down and thought carefully about what they were supposed to achieve. This makes their success all the more remarkable. They did put a stop to the Averröists and finally settled the row over how Christians should interpret Aristotle. But they did not prevent natural philosophers from pushing back the boundaries of their subject. Things could have gone so differently. If the Averröists had pushed the Church into a corner, then Aristotle might again have been banned outright. Wiser counsel prevailed and both the condemnations and their enforcement allowed space for natural philosophy to flourish.

Much of the credit for preventing the 1277 condemnations from being interpreted too widely must go to Thomas Aquinas, even though he had died two years previously. His frequent references to the books of Averröes ensured that they were not themselves prohibited. Furthermore, among the forbidden propositions, there were some that he had probably supported. By apparently seeking to correct the great scholar, the bishop of Paris had bitten off more than he could chew. The Dominicans lobbied hard for Thomas’s canonisation and within half a century had attained their goal. When he was made a saint in 1323, a later bishop of Paris had to declare the condemnations amended so that they did not conflict with his thought.25 After Thomas Aquinas was admitted to the ranks of the blessed, no one could claim that a combination of Aristotle and Christianity automatically led to heresy.

The condemnations and Thomas’s Summa Theologiae had created a framework within which natural philosophers could safely pursue their studies. The framework first defined clear boundaries between natural philosophy and theology. This allowed the philosophers to get on with the study of nature without being tempted to indulge in illicit metaphysical speculation. Then the framework laid down the principle that God had decreed the laws of nature but was not bound by them. Finally, it stated that Aristotle was sometimes wrong. The world was not ‘eternal according to reason’ and ‘finite according to faith’. It was not eternal, full stop. And if Aristotle could be wrong about something that he regarded as completely certain, that threw his whole philosophy into question. The way was clear for the natural philosophers of the Middle Ages to move decisively beyond the achievements of the Greeks.

It would be a mistake to see the restrictions that the 1277 condemnations placed on natural philosophers as evidence that the Church was anti-science. True, there was no such thing as completely free inquiry, but placing limits around a subject is not the same thing as being against it. The limits imposed on natural philosophy served a dual purpose. While they did prevent it from impinging on theology, they also protected natural philosophers from those who wanted to see their activities further curtailed. Like a country with secure borders, philosophy was safe to develop in peace and without fear.

The Gothic Cathedrals

With the dispute over natural philosophy resolved, the bishops of Paris could devote themselves to fitting out their new cathedral. The towers had been completed in 1250, but interior and exterior decoration continued until 1300.26 Notre Dame de Paris is only the most famous of the Gothic cathedrals that sprouted throughout northern France during the twelfth century. If you ever have the chance to visit the region, it is worth heading for the equally beautiful churches in Orléans, Reims, Rouen or Chartres instead. There, you will be able to enjoy the architecture without the horde of fellow tourists that so blight a trip to Paris. Even the most one-eyed critic of medieval civilisation cannot deny that the Gothic cathedrals are among the wonders of the world. After more than seven centuries, they continue to hold visitors and pilgrims in awe. In recent years, restoration programs have left many of them looking better than ever. Soot and pollution have been laboriously cleaned off to reveal their shining veneer beneath. Now they glow golden in the sun.

Gothic architecture relied on three innovations – the pointed arch, rib vaulting and the flying buttress. The style was not called ‘Gothic’ at the time. The term was coined in the sixteenth century when it was intended as yet another barb aimed at the Middle Ages. The style was originally called ‘French’ because the earliest truly Gothic building was the new church of the Abbey of St Denis on the outskirts of Paris,27 where Peter Abelard had once been a monk.

Pointed arches came from India and arrived in Europe some time in the eleventh century. All arches are intended to support a load, be it a roof or a bridge. Round arches send the entire weight of the load straight down the pillars on which they stand. A pointed arch does not. It has a natural tendency to splay outwards. There are two consequences of this. Firstly, it is not necessary to sit a pointed arch on top of enormous thick pillars, as they are not required to bear the full load. Secondly, some kind of exterior support is needed in order to stop the arches from pushing out the walls of the building. The support that medieval masons hit upon was the flying buttress. This holds in the outside of the wall and means that the interior of the building is spacious and uncluttered. The new idea caught on remarkably quickly. Some cathedral builders even changed their plans halfway through construction. At Bayeux, the bottom half of the nave is supported by round arches over massive stone pillars. Above them, fine pointed arches frame the windows with much more slender columns.

The final element of the Gothic style is the rib vault. The roof is held up by a series of arches but instead of these running perpendicular to the wall, they are sent across diagonally. This means that two ribs can cross over each other, mutually reinforcing and reducing the amount of space that has to be filled between them.

The triumph of Gothic architecture is that medieval masons moulded these three elements into a series of aesthetic masterpieces. They wanted to build upwards and create massive amounts of interior space. And because the flying buttresses were outside the building, they could fill the walls with glass rather than needing enormous trunks of stone. The results have stood the test of time.

Height was the ambition of the masons and every bishop wanted his cathedral to rise over that of his neighbours. The trend towards ever-taller buildings culminated with the magnificent choir at Beauvais. When you step through the doorway of Beauvais Cathedral, your eyes are drawn inexorably upwards. The vaults are an unprecedented and unrepeated 160 feet (48 metres) above the floor.28 A thick screen of slender pillars in two tiers swings around the apse of the church to form the choir. Between them, stained-glass windows curve across the entire field of vision. The effect is like standing in an exquisite kaleidoscope of colour. Unfortunately, like the builders of the tower of Babel, the masons at Beauvais overreached themselves. Merely to set eyes on the cathedral is to see that something has gone very wrong. For although it towers over its environs, only half of it has been built. It has a choir and a transept but where the longest nave in Christendom should have been, just empty space. The far wall of the transept is simply boarded up.

Work on the choir was completed in 1272, but twelve years later its excessive height caused it to collapse. The dense forest of columns that holds it up today, although an aesthetic success, is the result of the masons desperately trying to stop it from falling down again. No more was done for two centuries but in 1500 work finally started on the transept. It took 50 years and, on completion, appeared to be holding up well. At that point, hubris overtook the builders again and they planted an enormous bell tower on top, complete with a spire and capped with a heavy iron cross. Briefly, Beauvais possessed the tallest building in Europe. All too briefly. On Ascension Day 1573, the congregation had just filed out of the church when the tower crashed through the roof. Although the vaults were quickly repaired, the cathedral’s nave was never built.29 Even today the building remains in a precarious state. A huge brace is strung across the transept in an effort to keep it standing while the opposite wall is buttressed by a giant wooden prop dug into the foundations. The cathedral’s height makes it especially vulnerable to the high winds that sweep across the plains of Picardy. Despite standing for centuries, the days must be numbered for this monument to man’s inability to know when to stop.

We must now temporarily leave behind the philosophers and cathedral builders to spend some time in less reputable company. For modern science also owes a debt of gratitude to those who dabbled in magic, alchemy and astrology.

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