Medieval Christianity and the Rise of Modern Science

James Hannam
On October 31, 2012

Readers of the Biologos Forum do not need to be told that the alleged conflict between science and religion is a myth. The conflict thesis was born in the salons of ancien régime France where philosophes like Voltaire and Jean le Rond d’Alembert used it as a weapon against the Catholic Church. It was further developed in Victorian England by T.H. Huxley in his battle to diminish the influence of the clergy in London’s Royal Society. And it was perfected in American universities by the likes of Andrew Dickson White, first president of Cornell University, who provided the theory with intellectual ballast in his heavily annotated A History of the Warfare of Science with Theology (1896). Today, historians of science have long disposed of the conflict thesis, but it lives on in the popular imagination.

The inevitable companion to the idea that the Church has held back scientific progress is that we must look outside Christendom to discover the origin of modern science. But this is also false. Modern science stands as one of the great achievements of Western civilization. And, despite what we have often heard, it is certainly an achievement of the West, not of Islam, China or even ancient Greece. Many historians of science are still reluctant to admit this. This may be because the fad of post-modernism bit them hard and has refused to let go. They have developed a habit of praising Arabic and ancient Greek science as successful on their own terms but they have lost sight of the fact that, viewed objectively, the theories advanced by early science were quite false.

Of course, we should have respect the Greek and Islamic natural philosophers who struggled to comprehend the world. But most of what they taught, through no fault of their own, was woefully inaccurate. This was because their aims for science were nothing like ours. They wanted to understand nature in terms that made sense of their ethical or religious beliefs, and formed their theories accordingly.

galen_lithographTo take just one example, pre-modern medicine was an unmitigated disaster, far more likely to kill patients than cure them. Treatments such as bleeding and purging could only weaken the constitution of the sick, reducing their bodies’ capacity to fight off infection. It is no surprise to find that the most celebrated doctor of antiquity, Galen of Pergamum (left), considered himself as much a philosopher as a healer. Given the ineffectiveness of learned physicians, it’s little wonder that people put so much stock in miracles and magic. Perhaps the most surprising thing is that doctors were able to maintain their professional status through all the centuries that they could do little more that hasten their clients to the grave. Luckily for us, we can be much more confident that modern medicine really can cure us of many diseases. So the history of science should be the story of how we went from being fundamentally wrong about the natural world to being, in large part, right.

Science as we imagine it today, with laboratories, experiments and a professional culture, is a recent phenomenon that did not appear until the nineteenth century. But its origins can be found much earlier and we usually look for them in the period known as the ‘scientific revolution’. It is commonly believed that the recovery of Greek philosophy during the Renaissance gave Western civilization the inspiration it needed to launch this revolutionary way of looking at the world. In this view, hardly anything of consequence for science occurred between the fall of Rome and the era of Copernicus and Galileo. Carl Sagan produced a timeline of scientific progress in his book Cosmos (1980) showing nothing at all happening between AD415 and AD1543. But this is an illusion foisted on us by the same mentalité that declared science and religion must be in conflict. The truth is that to understand why modern science arose uniquely in the West, we have to travel all the way back to the Middle Ages.

Dispelling Myths

Before we do that, we should finally dispose of the two myths about scientific progress that we noted above. Firstly, as we have seen, the popular view remains that religion has held back science at every opportunity. Many people still believe that science has advanced by fighting superstition and making the world safe for rational enquiry. It is true that certain religious doctrines contradict some scientific discoveries. The creation/evolution controversy is a case in point, but such quarrels have been surprisingly rare. Even the infamous trial of Galileo, the other example of conflict most often cited, was an aberration in the Catholic Church’s usual supportive attitude towards science.

On the other hand, the problems with the thesis that science and faith are locked in a historical conflict are formidable. For a start, the so-called ‘scientific revolution’ in the seventeenth century coincided with the period when Christian belief in Europe was at its strongest. Only after science had triumphed did religion start to suffer any sort of decline. And, if Christianity really had tried to hold back scientific progress, the chances are that it would have succeeded. Modern science would not have arisen in Christian Europe at all.

As it happens, much of the evidence marshaled in favor of the conflict thesis turns out to be bogus. The Church never tried to outlaw zero or human dissection; no one was burnt at the stake for scientific ideas (not even Giordano Bruno); and no educated person in the Middle Ages thought that the world was flat, whatever the Bible might imply. Popes have had better things to do than banning vaccination or lightning conductors on churches. The thought of a pope excommunicating Halley’s Comet is absurd, but this has not prevented the tale of Calixtus III (right) doing just that from entering scientific folklore. It is remarkable that authors today, who consider themselves skeptics, can swallow some of these stories whole. Carl Sagan introduced his readers to a ‘baloney detector’ in his book, The Demon-Haunted World (1997). It is a great shame he never used it on his own writings. He presented a completely fictitious account of the murder of the pagan philosopher Hypatia in Cosmos and falsely blamed Christians for the destruction of the Alexandrian library.

Zealous Victorian historians did find occasional examples of ecclesiastical stupidity, such as the Boston pastor who warned that lightning strikes caused earthquakes. They rewrote history to make these marginal figures into leaders of opinion. Religious dissidents who paid the ultimate price for their faith were recast as champions of reason. Pope Boniface VIII issued a bull intended to stop crusaders sending their bones home for burial; he would have been most surprised to hear that, according to Andrew Dickson White, he had legislated against human dissection. Whenever a priest questioned a scientific theory, which they often did in their capacity as amateur scientists, this was held up as an example of religious obstruction. Historians have been debunking these legends for over a century now, but they continue to be recycled by each new generation.

The role of ancient Greek and Islamic thought

The other myth about the rise of science is that westerners only had to pick up the baton from the ancient Greeks, or, as has been more recently alleged, the Islamic caliphate. In reality, modern science is qualitatively different from the natural philosophy practiced by the likes of Aristotle or Avicenna. Aristotle started from the passive observation of nature and then built up a system based on rational argument. This had two enormous disadvantages: compared to controlled experiments, passive observation is usually misleading; and not even Aristotle’s powers of reason could prevent blunders in his arguments.

His discussion of motion is a case in point. He observed that everyday objects tend to stop when nothing was pushing them. From this observation, he deduced the principle that all moving objects must be moved by something else. He elevated this principle to the status of a logical certainty and then used it to explain other kinds of motion. He even thought that it successfully proved the existence of God. If the universe as a whole is full of movement, he argued, it requires an exterior unmoved mover,—that is, God—to keep it going. But of course, Aristotle’s initial observation was just a specific instance without any general applicability. We now know that objects do not stop when there is no force on them. They tend to keep going in a straight line: a principle enshrined as Newton’s First Law. Other observations led Aristotle to decree it certain that a vacuum can never exist; that heavy objects fall faster than light ones and that the earth must occupy the centre of the universe. All wrong. Aristotle, alas, was mistaken about almost everything. This was not because he was a fool but because he was practicing a natural philosophy that could never lead to true theories.



Islamic science suffered from similar drawbacks. Advances made by Muslim natural philosophers were significant, but rather more modest than we are usually led to believe. The importance of Alhazen’s investigations into the properties of light is indubitable. They were used by Roger Bacon in his own writings on perspectiva and thence were integrated into the modern theory of vision developed by Johannes Kepler. Even so, Alhazen’s experimental method was limited and not carried forward by his immediate successors. Similarly, the intuition of Ibn al-Nafis, in the thirteenth century, concerning the circulation of blood between the heart and the lungs is deeply impressive. But there is no evidence that he had any impact on the rediscovery of this phenomenon by Michael Servetus and Realdo Columbo three centuries later.

Consequently, we should be skeptical about some of the claims made for Islamic science in some recent television shows and books, not to mention in Wikipedia. That said, the misattribution of scientific advances to Islamic sources has sometimes been the fault of the pioneers who actually discovered them. Alchemy is a case in point. During the Middle Ages, it was customary for Christian alchemists to write their treatises under the name of the fabled Arab savant Geber. It is not surprising that later historians mistakenly assigned developments such as the first production of powerful acids as well as the isolation of alcohol to Geber himself. Alcohol was even assigned an Arabic name by Christian authors. We now know that he probably did not write any of the works attributed to him.

On the other hand, there was one towering exception to the rule that early science tended to be bunk: both the Greeks and Arabs excelled in mathematics. This was because pure rationalism works a treat when it is restricted to geometry and arithmetic. The imams had plenty of practical uses for math, as well: the Muslim calendar follows the moon and not the solar year, while mosques had to be orientated towards Mecca. Both these religious problems required mathematical solutions. It’s also said that the complicated rules of Islamic inheritance made algebra indispensable. Even our word algebra is a corruption of al-jabr, the name of an Arabic textbook widely used by Christians.

Despite these genuine contributions, it is nevertheless fair to say that neither Aristotelian rationality nor Islamic mathematics was the key to the developments that made the modern world possible. As we shall see in the second part of this essay tomorrow, the very different cultural situation in medieval Europe allowed for Aristotle’s faulty method to be criticised by the Catholic Church, meaning that previously forbidden ideas could flourish. The Church also made natural philosophy a compulsory part of the course that it required trainee theologians to follow. So, unlike in Islamic madrassas, science had a central place in Christian centers of learning. Indeed, it was a Christian worldview that proved especially compatible with—even necessary for—the rise of modern science.

Breaking with Aristotle

AlfonsoVI_of_CastileIn 1085, the great Islamic city of Toledo in Spain fell to Alfonso VI, King of Castile (left). Christian forces captured its magnificent libraries intact and word soon spread about the fabulous riches contained therein. Europeans were well aware that they had lost much of the learning of the ancient world after the fall of Rome and they were keen to reacquire it. The resulting movement to translate Arabic and Greek scholarship into Latin meant that by 1200, Christians were back up to speed in science and math.

Initially, some churchmen were suspicious about all this new knowledge and feared that it would be misused to challenge the faith. When a nest of heretics was found in Paris and its environs, the resulting panic led to a temporary ban on Aristotle’s natural philosophy at the university there. Scholars were furious and demanded that the forbidden books were reinstated. So, after a decent interval, the Pope rescinded the ban and Aristotle took his place at the heart of Christian education.

As we saw before, the danger of Aristotle was in his method. It was bad enough that several of his conclusions contradicted revealed theology. But the problem went deeper than that. Because he had tried to arrive at results deductively, Aristotle made his conclusions seem logically necessary. His admirers did not just claim that he was right, they said he had to be right. In effect, Aristotle’s most dedicated followers were agreed that God Himself was bound by what Aristotle thought because, despite His omnipotence, even the Deity could not defy logic. But, in reality, most of Aristotle’s natural philosophy was wrong. Science could go nowhere until the dead hand of the Greek sage was lifted from it.

The Church had to deal with this, even though it was primarily interested in theology and not science. In 1277, the bishop of Paris, with papal approval, issued a list of opinions, drawn from the work of Aristotle and his medieval followers, which he declared heretical. The effect was paradoxically liberating. All of a sudden, European philosophers were freed to think outside the Aristotelian box. No longer could they assume that the Greeks were always right. Thus, if God willed it, vacuums were no longer deemed impossible. There could even be more than one universe. Now natural philosophers could speculate on all sorts of things previously ruled out of court. The result was that the fourteenth century became a scientific golden age when much of the groundwork was laid for ideas that later ended up in the books of Copernicus and Galileo. Let me give a couple of examples.

Medieval sources of Renaissance discoveries

Copernicus, of course, is famous for proposing that the earth rotates and orbits the sun, rather than being stationary in the center of the universe, as Aristotle had taught. It is perfectly sensible to believe that the Earth is at rest, especially given that we cannot feel it moving. However, in fourteenth-century Paris, the philosopher John Buridan and his student Nicole Oresme developed the arguments (pictured right), later used by Copernicus, to explain why we cannot tell if the Earth is in motion. Aristotle proposed that the universe turns around the Earth each day. Buridan asked why it cannot be the other way around, realizing that what we observe would be exactly the same. He used the analogy of someone one a boat:

If anyone is in a moving ship and imagines that he is at rest, then should he see another ship, which is truly at rest, it will appear to him that the other ship is moved … And so, we also posit that the sphere of the sun is everywhere at rest and the earth in carrying us would be rotated.

Compare that to the argument used by Copernicus in his book, On the Revolutions of the Heavenly Spheres:

When a ship sails on a tranquil sea, all the things outside seem to the voyagers to be moving in a pattern that is an image of their own. They think, on the contrary, that they are themselves and all the things with them are at rest. So, it can easily happen in the case of the earth that the whole universe should be believed to be moving in a circle [while the earth is at rest].

Of course, like other Renaissance writers, Copernicus never acknowledges his debt to his medieval predecessors. Rather, he quotes a line from Virgil’s Aeneid, giving his argument a wholly bogus classical gloss. For what it’s worth, Copernicus also used the fruits of Islamic mathematical astronomy without attribution. As the fashion of his time demanded, he would only admit to using Greek and Roman sources.

Despite his correct argument about relative motion, John Buridan eventually decided that the Earth was not moving. He imagined that if it was rotating, an arrow fired straight into the air would land some distance away because the Earth would have moved before it reached the ground. His pupil, Nicole Oresme, realized this argument was false because the arrow inherits the motion of the Earth when it is fired. So, the Earth, bowman and arrow are all rotating together. Galileo covers these thought experiments in great deal in his Dialogue Concerning the Two Chief World Systems (for which he was put on trial by Pope Urban VIII). But you would never guess from Galileo’s text that his arguments are actually rather old hat.

Even Galileo’s most important work, Dialogues on Two New Sciences, contains strong echoes of ideas developed in the fourteenth century. The formula he derives for the motion of a uniformly accelerating body was really discovered in fourteenth-century Oxford at Merton College. And the diagrammatic proof that Galileo provides for this theorem was first illustrated by Nicole Oresme himself.

There can no longer be any doubt that the pioneers of early modern science were far more indebted to their medieval predecessors than they were inclined to admit. But by the sixteenth century, humanism, the political correctness of its day, meant that it was respectable to acknowledge the influence of the classical world while denigrating the Middle Ages. To a great extent, this is still true today.

Science as practical theology

The importance of medieval science extends beyond simply providing the theories that early modern scientists exploited. Medieval Christian theologians also developed the metaphysical framework within which it made sense to practice science at all.

Given today’s perceptions of a conflict between science and religion, it is surprising to find that Christianity has proved to be uniquely accommodating to the study of nature. While there is little in the Bible that could be called science, the book of Genesis is very clear about where the universe came from. Contrary to Aristotle’s view that it is eternal, the Bible says that God made the world at the beginning of time. Christians believe that the world was created ex nihilo, out of nothing. God did not have to work from pre-existing material that resisted His purposes. This meant, as Genesis affirms, that the creation turned out ‘good’ and as God wished it to be. Christian theologians held that He had also allowed the world to develop freely through natural laws which He had ordained. The order of nature followed these laws rather than God personally having to manipulate each atom.

The twelfth-century, William of Conches had already realized this when he wrote:

I take nothing away from God. All things that are in the world were made by God, except evil. But He made other things through the operation of nature which is the instrument of divine operation.

Another feature of the Christian God was is reliability. He is not capricious like the Olympians of ancient Greece or entirely beyond human comprehension, like Allah. This meant that natural philosophers knew that they could depend on the laws that He had laid down. Nature itself should reflect her creator by obeying His commandments. This gave Christians good reason to believe that science was a practical venture; that nature did follow fixed laws that could be discovered. This view was expressed by Thierry of Chartres, another theologian of the twelfth century:

Because the things in the world are mutable and corruptible, it is necessary that they should have an author. Because they are arranged in a rational way and in a very beautiful order, it is necessary that they should have been created in accordance with wisdom. But, because the Creator, rationally speaking, is in need of nothing, having perfection and sufficiency in himself, it is necessary that he should create what he does create only through benevolence and love.

Science was also a theologically righteous path to pursue. Since the world was created by God, exploring how it works does honor to its Creator. And because science studies the ordinary course of nature, it was not necessary to worry about the rare occasions that God does intervene directly through miracles. John Buridan explained in the fourteenth century, “it is evident to us that every fire is hot, 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 science.”

Nonetheless, because God was free to do as He pleased, Christians realized it was impossible to work out the laws of nature from rational analysis alone. The only way to discover His plan was to go out and look. This principle of God’s freedom and absolute power was asserted by the bishop of Paris in 1277. It meant that science could not rely on pure reason to generate theories, still less Aristotle’s “logically necessary” conclusions. God created the world in the way He wished to, not the way Aristotle said He had to.

Of course, medieval natural philosophers no more had in mind the development of modern science than the ancient Greeks had. Christians practiced science to serve theology, just like pagan natural philosophy had served ethics. Specifically, scholars of the Middle Ages wanted to understand the universe in a way that made sense of their religious beliefs. They saw the world as a place that was God’s creation but one which also had its own freedom and integrity. It was a place where human beings could make real moral decisions that had real consequences. It just so happens that their metaphysical were especially conducive to science.

Given the advantages that the religion provided, it is hardly surprising that modern science has only developed within a Christian milieu. Although it is possible that other religious traditions could have provided a similarly fertile metaphysical ground for the study of nature, none that we know of have actually done so. Nor is it startling to find that Copernicus, Kepler and Galileo worked within the framework of medieval natural philosophy, rather than in a transplanted ancient Greek tradition. It seems fair to conclude that Christianity was an important cause of the unique development of western science, the only science which has consistently produced true theories of nature.

Before You Read ...

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James Hannam
About the Author

James Hannam

James Hannam took a Physics degree at Oxford before training as an accountant. He enjoyed a successful career in the City, mainly financing film production, but harboured ambitions to write about the history of science. In 2001, he started a part time MA at Birkbeck College, London in Historical Research. In 2003, he began his PhD program at Cambridge in the History and Philosophy of Science, and wrote his thesis on the decline of medieval learning during the 16th century. His book for general readers, God's Philosophers: How the Medieval World Laid the Foundation of Modern Science, was published by Icon in 2009. It is titled in the U.S. as The Genesis of Science: How the Christian Middle Ages Launched the Scientific Revolution. The book was shortlisted for the Royal Society Prize for Science Books in 2010. James lives in Kent, England with his wife and two children.