The word “science” is derived from the Latin scientia, meaning “knowledge.” In this sense, science in the 15th century was identical to its modern form: knowledge of the world gathered by observation. However, during the medieval period, that is all it was regarded as: knowledge. In the modern sense, science is a defined field, with specific disciplines and methods. Any given subject must meet a number of rigorous standards to be considered “scientific.” In the medieval period, any knowledge gathered by observation and logical thought fell within the term “science”, assuming the term was used at all.
Science as it is thought of in the 15th century began with the Greek philosopher Aristotle. Aristotle is known for his study and teachings of logic and mathematics, but also defined a field he called “natural philosophy.” Natural philosophy was based on the idea that one could understand the universe by learning the particulars of the natural world. The subjects covered by this philosophy include most of the modern natural sciences, such as biology and physics. While this philosophy was defined by empirical data, observed from nature, it was generally more qualitative than quantitative. That is, Aristotle could use his method to describe a quality of a falling object or a natural phenomenon, but he could not put numbers to it. This is due in part to an absence of the ideas of mass, force, and temperature. While he could certainly feel that one object could be hotter than another, the lack of measuring instruments meant he had no way of putting numbers to his observations.
After the collapse of the Western Roman Empire, science as a field of study returned to Europe sometime after the beginning of what we now call the Crusades. Aristotle’s methods and teachings had survived in records held by the Eastern Roman Empire, which would eventually become the Byzantine Empire. The Aristotelian method spread to Arabic philosophers, where it flourished. One of the most influential products of scientific boom in the Arabic world was the Canon of Medicine by Ibn Sina. The Persian philosopher compiled and summarized all medical knowledge of the time. The book covered many subjects, from the Four Humours to general anatomy to drugs and their effects. The Canon remained a medical authority not just in Islamic lands but throughout Europe well into the 17th century and even remained a standard of study through the 19th century.
Aristotle’s teachings of natural philosophy were re-introduced to Europeans during the period known as the Crusades. Contact with the Arabic world brought many things to Europe, from trade goods to schools of thought and knowledge. Men like Tomas Aquinas and Roger Bacon were among the early names in a school of critical thought known as Scholasticism, which grew from this exchange of ideas. Scholasticism developed in the 12th century out of an effort to unionize Christian theology with the philosophy of antiquity which had seen a recent revitalization, and evolved into a process of rigorous conceptual analysis similar to the modern scientific method, and was applied to many fields of study.
Roger Bacon (born 1214) was an early advocate of study through empirical observation. Taking advantage of the newly developing opportunities for learning, Bacon spent most of his life at study before turning to teaching later in life. In addition to helping lay the foundation of what would become the scientific method, Bacon wrote extensively in the fields of mathematics, alchemy, astronomy, and the physiology of eyes and how sight works. Bacon also wrote a treatment on the place of philosophy in theology. His works there were mirrored by Tomas Aquinas (born 1225), who viewed theology as a science in itself, drawing from the raw natural data of written scriptures. He wrote of how the body composes the human, but the immaterial soul is what made us more. The human body is a variety of animal, and thus could be studied as such. But it was the presence of the soul, immeasurable and unquantifiable, was what made us holy. Aquinas also sought to prove the existence of God through logical thought, and is in modern times known for the idea of Original Cause, which states that as everything must be caused by something, an infinite change of causation is impossible. Therefore, he believed, there must exist some original cause which was self-causing, which Aquinas identified as God.
Men such as these set the foundation for science in the 15th century. Study was most often done through the church. In contrast to modern times, medieval science and medieval theology most often went hand-in-hand. It was the belief of the Catholic Church and the Papacy that any knowledge of consistent rules existing in the natural world only served as evidence for a divine creator, and it was not until much later in history that the fields of science and theology began to view each other with opposition.
But even in the certainty of the church, there was still present the desire for evidence. The proliferation of taking the words of elders as fact had eroded away in centuries previous, and curious minds were searching everywhere for evidence of previously known truths, and for entirely new concepts and knowledge.
The fields of medicine, astronomy, and geography were near the forefront of development, as they saw the most practical application. The many plagues that had hit Europe and were still hitting Europe ensured that a skilled physician was especially valuable, even above and beyond his ability to cure a fever. Astrology, the idea that the position and movement of heavenly bodies affected the natural world, was at something of a peak, and the stars were still the primary source of navigation, and so every visible body in the sky was mapped and charted. The new navigational capabilities led to more and more detailed maps being drawn as trade ships traveled the globe, which lent to a greater understanding of the layout of the world.
These were not the only fields of learning which were advancing, however. Many set themselves to many fields of study. Perhaps one of the best examples of this is Leonardo da Vinci. In addition to being a sculptor and painter of great renown, da Vinci also studied many fields of natural science extensively, writing treatments on subjects ranging from geography to botany to engineering. Da Vinci came to embody the ideal that was rising in the 14th century; a man whose studies and knowledge were both extensive and deep.
Knowledge was becoming power in the 15th century. More and more established concepts were being questioned, and more regard was being given to that which could be observed with the eye.