• 
• 
• 
• 

[Philosophy with the Seven Liberal Arts, Nicolas Xavier Willemin (1763–1833) / Public domain—Wikimedia Commons]

The caricature of the Middle Ages and scientific progress is of a world of bitter rivals; Christian theology and natural philosophy (as scientific study was called) fighting until the former emerged as the victor. But for most medieval theologians and scientists alike, the relationship looked far different. Instead of a battle, it was a royal court. Theology, the “queen of the sciences,” reigned, and natural philosophy was her handmaiden. And in that court, natural philosophers did not just walk hand-in-hand with the church—they were, more often than not, senior members of the clergy. 

The mathematician pope

On Palm Sunday of AD 999, Christendom’s foremost mathematician became Pope Sylvester II. Gerbert of Aurillac (c. 946–1003), as the new pontiff had been known before his elevation, reached these heights in spite of humble family origins. Gerbert’s first calling was as an educator. He taught his students arithmetic, astronomy, and harmonics; in turn they spread an interest in mathematics across France and Germany. He even introduced Arabic numerals 0 through 9—the very ones we use today—into Europe. 

Holy Roman Emperor Otto II took notice of Gerbert’s talent and holiness and appointed him as tutor to his son. Gerbert must have had quite an influence on the lad, for when the boy received the imperial mantle himself as Otto III, he made his old teacher pope. 

To be fair Gerbert’s scientific knowledge was modest by the standards of classical Greece and Islamic Spain. Following the collapse of the western Roman Empire, knowledge of the Greek language had been lost in western Europe and, with it, access to the works of ancient geniuses like Euclid, Ptolemy, and Aristotle. However, Gerbert’s career showed that in the so-called dark ages, a passion for natural philosophy was no impediment to a highly successful career in the church.

For medieval Christians science always consisted of the study of creation; that there was a creator behind the material world was a foregone conclusion. This had some important consequences for how they approached the subject. First, they expected to see God’s character reflected in the material world. Nature should be law-abiding rather than capricious, benevolent rather than amoral. As the twelfth-century philosopher William of Conches put it, “in the creation of all things, one can behold divine power, wisdom and goodness.” That meant Christians found it worthwhile to study nature and to figure out the rules that God had ordained for nature to follow. 

Second, if God invented natural laws, they had to be consistent with the Bible, God’s other great work. Hugh of St. Victor, another twelfth-century scholar, saw a clear analogy between Scripture and nature when he wrote, “The whole of the sensible world is like a book written by the finger of God.” The study of creation was just as appropriate for Christians as the study of the Bible.

Not everyone accepted this congruence between the book of nature and the book of Scripture. One notorious sect, the Cathars, rejected both. As dualists who believed that the material world was the product of a malicious deity, they also rejected traditional orthodox interpretations of the Bible. The church has deservedly been criticized for the severity with which it dealt with this heresy by starting a war in southern France to stamp it out. But in addition to wielding the sword, it also launched campaigns to convert heretics. To succeed, the church had to convince the Cathars that dualism was objectively wrong. The one God, not his evil twin, had created the world.

New science, new beauty

Luckily the tools for this struggle had recently become available. In 1085, Toledo, the capital of Islamic Spain, fell to the Christian King Alfonso VI; the city’s magnificent libraries were now in Christian hands. At around the same time, the Crusades opened up the Byzantine Empire and the Near East to western scholars. Catholics finally had access to the science and mathematics of the ancient Greeks, as well as to the achievements of Arabic science and mathematics. 

These works—in particular the philosophy of Aristotle—further revealed the beauty and intricacy of the natural world, proving to many readers that a good and rational God created it, not a malignant spirit as the Cathars insisted. The newly established Order of Preachers, better known as the Dominicans after their founder Dominic of Caleruega (1170–1221), led the charge in these efforts to harness natural philosophy for the faith. 

The Dominicans learned to use Aristotle to refute the arguments of heretics without having to rely on the Bible. Their most famous member, Thomas Aquinas (1225–1274), made his name by synthesizing Christianity and Aristotelianism. His teaching came close to becoming Catholicism’s official philosophy for generations. 

Yet from a Christian perspective, Aristotle’s doctrines were not without their problems; after all he was a pagan born four centuries before Jesus. For example Aristotle had taught that the universe is eternal and uncreated, that “god” has no interest in humanity, and that people do not possess individual immortal souls. 

Unsurprisingly in 1210 authorities discovered a group of heretics inspired by Aristotelian thought active around Paris. Known as Amalricians, they were pantheists who believed that the universe itself is a divine being. The local bishop, overreacting in bureaucratic mode, promptly banned books by Aristotle. 

The pope took a more measured view and lifted the ban, but made clear that Aristotle’s books had to be read with care to ensure they didn’t encourage heresy. He expected Christians to distinguish useful elements of Aristotle’s philosophy while rejecting damaging teachings. Before long the University of Paris drew up a syllabus stipulating that students who wanted to study theology must first master Aristotle: not just his science, but also his works of reason, logic, and ethics. 

The University of Paris was in fact the preeminent example of a new kind of educational establishment springing up all over Europe. Traditionally schools had centered around an individual teacher or a monarch’s sponsorship. When the teacher retired or the monarch died, the school went with them. Universities were different. Structured as corporate bodies, they could set their own internal rules and face off against the world as a collective. Masters and students might come and go, but the university endured. Indeed most of these medieval foundations are still operating today. 

Universities provided a home for scholarship, including natural philosophy and mathematics. To obtain a bachelor’s degree, every student had to learn arithmetic, geometry, and astronomy. These students needed lecturers, so scholars who wanted to devote their careers to science found employment—and also intellectual freedom of at least a limited sort. 

Stick to philosophy

The universities disciplined their members; only rarely did church hierarchy get involved in more serious cases. History proves the common caricature of scientists being burned at the stake for meddling in forbidden knowledge almost wholly unwarranted. As far as we know, no executions for beliefs we today understand as “scientific” ever took place. The closest example was Cecco D’Ascoli, an astrologer executed in Florence in 1327 for teaching that Jesus’s poverty and death resulted from his birth under the wrong stars. Even Cecco had to commit a second offense before he paid this ultimate penalty.

That’s not to say that Aristotelian science became uncontroversial after the Amalrician debacle. Debates continued to rage at the University of Paris through the thirteenth century. Eventually the university insisted that philosophers stick to philosophy and leave theological speculation to doctors of divinity, who had studied Aristotle themselves before spending at least seven more years on the Scriptures and the opinions of the church fathers. 

Ultimately the church supported the study of natural science because it buttressed faith. Despite this subservient status, science enjoyed sufficient resources and prestige and made significant theoretical advances. Some of the most important developments took place at the University of Oxford in the first half of the fourteenth century. A group of Merton College scholars known as “the Calculators” started to use math to place Aristotle’s kinematics, the science of moving objects, on a more rigorous footing. 

Thomas Bradwardine (c. 1300–1349) was one of the Calculators’ earliest representatives. “Whoever has the effrontery to pursue physics while neglecting mathematics,” he declared, “should know from the start that he will never make his entry through the portals of wisdom.” Following his own advice, Bradwardine derived a numerical formula that describes how Aristotle said objects moved when a force is applied to them. His formula is wrong because Aristotle’s kinematics was wrong, but it showed how effectively the world could be described in mathematical terms. 

Bradwardine eventually left Oxford, pursued a successful clerical career, and became archbishop of Canterbury. However, his Calculator colleagues extended his work, discovering another formula that describes how far a uniformly accelerating object moves in a given time. Known as the mean speed theorem, it formed a key part of Galileo’s work on mechanics in the seventeenth century and is still taught in schools. However, Galileo didn’t give any credit to his predecessors, so the contribution of the Oxford Calculators was forgotten until rediscovered by modern historians.

I shot an arrow in the air

Equally important scientific developments took place in fourteenth-century Paris. The rector of the university, John Buridan (1301–1359), wanted to understand why objects keep moving after the withdrawal of the force that set them off. Aristotle said things could only move if something else is acting on them. Buridan realized this couldn’t be right: after all, when an arrow is shot from a bow, it continues to fly through the air even though nothing is pushing it. He formulated the concept of impetus, a force that keeps the arrow racing toward its target until air resistance slows it down. 

Impetus raised an interesting question: what would happen without air resistance or another kind of friction? Obviously this could never happen on the earth, but what about the heavens? Aristotle had said that the continuous action of God rotates the celestial spheres that carry the planets around the earth. Buridan thought this might not be necessary. Once God set the planets on their courses at the beginning of time, there would be nothing to slow them down and they would keep moving forever. This conclusion was an important precursor to Sir Isaac Newton’s (1642–1727) first law of motion, on inertia, 300 years later. 

Buridan also wrestled with God’s freedom to perform miracles if he saw fit. In general he believed the material world follows regular laws that God had ordained and philosophers could investigate: “It is evident to us that every fire is hot and that the heavens are moved, even though the contrary is possible by God’s power. And it is evidence of this sort that suffices for the principles and conclusions of natural philosophy.” 

Everyone agreed that miracles are possible, but also that they are rare enough not to interfere with studying the ordinary course of nature. God’s freedom also meant he could have organized the world in any way he pleased; he wasn’t bound by how Aristotle thought he should have done it. Buridan decided to examine whether God had arranged the world to follow one of Aristotle’s most important propositions—that the earth is stationary at the center of the universe. 

On an everyday basis, it seems to us that the earth isn’t moving; the sun, moon, and stars appear to rotate around us every 24 hours, while we can’t feel anything to suggest the earth is in motion. The ancients believed that if the earth were actually turning, a rushing wind would accompany it. Not so, said Buridan: if the atmosphere rotates with the earth, things would appear the same whether the earth or the heavens rotates. God could have arranged things either way. Indeed it seemed more elegant for him to make the tiny earth spin around its axis each day rather than move the vast sphere of the heavens. 

Buridan explained this concept with the example of a boat floating down a river passing another vessel moored to the bank. Without reference to the surrounding landscape, someone on the moving boat observing the stationary one would not be able to tell which was in motion: motion is relative to our frame of reference. Copernicus (1473–1543) adopted exactly this argument, again without attribution, when he wanted to show why we can’t tell that the earth is orbiting the sun. 

Technological as well as theoretical progress occurred frequently in the Middle Ages. During the thirteenth century, the mechanical clock was invented, probably in England, to ring the bells so that monks would wake up in time to perform the divine office. Clocks rapidly spread into the towns, where they regulated the lives of workers as well as clergy. Hours became constant units of time rather than varying as the length of days and nights changed with the seasons. 

Eyeglasses were another medieval invention, first appearing in late thirteenth-century Italy. They substantially increased the working life of scribes by providing a remedy for far-sightedness. Medieval Christians eagerly adopted inventions from the Far East as well—including the compass, gunpowder, and printing. Once they had grasped the basic concepts, they improved on them and developed technologies that allowed Europe to dominate the early-modern world. The compass enabled voyages out of sight of land across the Atlantic and Indian Oceans, while gunpowder provided a huge advantage in warfare. 

Printing may have been the most significant new industry of the Middle Ages and required amalgamating several different technologies. Johann Gutenberg (c. 1398–1468), a metallurgist from Mainz in Germany, combined movable metal type, a wine press, and a sticky black ink from turpentine and soot to produce the first printed books in the 1450s. Paper made out of rags was much cheaper than parchment from animal skins and brought the cost of books down further. 

Dismissed as superstition

The rise of printing coincided with another area of renewed interest in the ancient world: the literature of Greece and Rome. Enthusiasts for the works of Plato and Cicero actively denigrated medieval scholarship as superstitious and (much worse) written in a degraded form of Latin. Luckily the new printed books preserved the natural philosophy of the Merton Calculators and John Buridan, ready for it to be picked up by Copernicus and Galileo.

Many people still imagine the Middle Ages as a period of stagnation dominated by an overbearing church. But it was in fact a period of dynamic change, of technological and scientific advances, and of the birth of institutions like universities, now so central to the modern world. Without the foundations laid during the Middle Ages, modern science as we know it might never have occurred. CH

By James Hannam

Show more