Thankfully, by the eleventh century, a degree of stability had returned and Europe entered a philosophical golden age. This was fuelled by the translation of the ancient Greek logic, science and mathematics. Christian scholars built on these foundations to produce a new way of thinking that eventually gave birth to modern science. That said, certain issues did first need to be addressed to define the relationship between science and Christianity. One question that medieval scholars had to answer was “what is the status of the Bible as a source of scientific knowledge?”. William of Conches, a twelfth century theologian and tutor to King Henry II of England, explained:
The authors of Truth are silent on matters of natural philosophy, not because these matters are against the faith, but because they have little to do with the upholding of such faith, which is what those authors were concerned with.
In other words, don’t expect to find much science in the Bible. And, as William also noted, you don’t have to take the scriptures completely literally. For instance, parts of the Bible do seem to imply that the earth is flat but no educated person in the Middle Ages actually believed that. They just assumed, correctly, that the Bible should be read figuratively on this point. As Galileo put it four hundred years later, “The intention of the Holy Spirit is to teach us how one goes to heaven, not how the heavens go.”
Still, why practice science in the first place? Another theologian of the twelfth century, Thierry of Chartres, realised that it was because nature is God’s creation:
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.
Thus, the rationality and order of nature was thought to be proof that the Deity existed. This made studying physical laws another way to know the thoughts of God. Nature was one book written by the creator, just as the Bible was another.
Science in the Middle Ages was dominated by theologian/philosophers who were as comfortable working on secular subjects as they were studying the scriptures. Thomas Bradwardine is a good example. While he was a master at the University of Oxford during the early fourteenth century, he made a breakthrough which challenged ancient Greek assumptions about how science should operate. Using the latest mathematical techniques, Bradwardine developed a formula that provided a universal description of motion. Aristotle had declared that since mathematics and physics were different subjects, you could not use one of them to prove something in the other. Bradwardine realised that this was a mistake. Mathematics is essential in all branches of science because nature obeys mathematical laws. This is one of the most fundamental tenets of modern science, restated by Galileo when he declared, “Science is written in this grand book… it is written in the language of mathematics.” Bradwardine himself left Oxford to pursue a successful career in the Church, which culminated with his appointment as Archbishop of Canterbury. Unfortunately, he had barely been enthroned when he died of the Black Death in 1349.
The equation of motion generated by Thomas Bradwardine was based on Aristotle’s physics and was consequently inaccurate. However, a member of the next generation at Oxford called William Heytesbury derived a correct formula. He showed that when an object accelerates at a uniform rate, the distance it moves is equal to how far it would have moved if it had travelled at its average speed. This is known as the “mean speed theorem” and it describes the velocity of an object falling under gravity. Although Heytesbury did not know of the theorem’s application to gravity, it was later used by Galileo in his own analysis of freefall.
Meanwhile, in Paris, John Buridan, struck several blows against the mistaken ancient Greek science which he had inherited. Aristotle had said that no object can move unless there is something else moving it. When you stop pushing something, he declared, it should stop. Buridan could see this was wrong. When he threw a stone, it kept moving after it had left his hand even though nothing was in contact with it. So he postulated a quality called “impetus”. This was a force impressed onto the stone by the thrower and proportional to its weight and speed. As the stone travels, said Buridan, its impetus is drained by air resistance. When it reaches zero, the stone stops.
Impetus is an important step towards the modern concept of momentum which is also a property of moving objects related to their velocity and their mass. More generally, Buridan could see that in the absence of friction, there would be nothing to expend impetus and so an object should keep moving forever. He couldn’t see any such instances on earth, but he observed how regularly the planets travelled across the sky. Perhaps, he suggested, God had set them moving at the Creation and because there was no resistance in the heavens, they would keep going until Doomsday. Here, Buridan began to formulate the idea of inertia, also known as Newton’s First Law.
John Buridan’s most brilliant pupil was Nicole Oresme. As well as being a gifted mathematician, Oresme wrote a diatribe against astrology and eventually rose to the rank of Bishop of Lisieux. His greatest scientific achievement was to prove the mean speed theorem geometrically. He also showed that when you plot a graph of an object’s speed against time, the area under the graph correlates to the distance travelled. Thus, Oresme started to use geometry to model moving objects three hundred years before Rene Descartes is alleged to have invented the idea.
Historians now recognise that the Middle Ages were a period of important scientific developments. Furthermore, Christianity was, on balance, a positive factor in the rise of western science. This is not to say that science and religion have always got along smoothly. The Galileo affair and today’s battle between evolution and creationism are certainly examples of where specific scientific theories have conflicted with particular religious doctrines. But these are exceptions. In general, Christianity has rubbed along with science just fine. In the Middle Ages, at least, it is hard to see how any scientific progress could have occurred otherwise.