By the end of the 1500s Europeans had cut themselves loose from all the old certainties of the Medieval past. Inspired by newly rediscovered knowledge of the ancient and classical world, as well as exposure to entirely new information about the world beyond their borders brought back by explorers, many began to question even the church's vision of nature and the creation. No longer content to separate the life at hand from the life hereafter, many tried to integrate knowledge of the spirit with knowledge of the body. Using the rediscovered tools of ancient philosophy, especially mathematics, European scholars and philosophers began to interpret the world through observation rather than through the teachings of the church. In their search for knowledge, they invented new tools of observation and measurement. As they found new explanations for how the world around them worked, Europeans began to redefine the nature not only of their civilization but of their entire conception of the nature of the world.

The Beginnings of Modern Science

Before the Renaissance, European scholars and philosophers looked for answers to their problems primarily in the past. Just as Islamic scholars saw Muhammad as the fountain of all wisdom, and the Chinese referred for answers to Confucius or Lao Tsu, Latin Christians returned to the authorities of the ancient past, not only the Bible, but also the Greek and Roman philosophers who had helped create the civilization of Rome. Scholastics believed that the teachings of these ancient authorities should not be questioned but simply accepted as truth. They believed that such general truths could be used to reach solutions to specific problems. This process of reasoning from the general to the specific, known as deductive logic, was the basis of European learning until the Renaissance.

The Christian worldview. The major authority to whom Scholastics looked for their view of the universe was Aristotle. Aristotle believed that knowledge could be acquired through observation using the five senses. He believed that every thing had its own natural qualities, such as heaviness or lightness. Things that were heavy naturally fell down, while things that were light rose. Since his senses told him that the earth moved neither up nor down, he concluded that it was both the heaviest part of the universe and its center. The planets and stars revolved around it because they were lighter. They were kept from floating off, he decided, because they were embedded in some invisible substance, which he called “crystalline spheres.” In addition, since the stars, planets and other objects beyond the moon's orbit were obviously made of a different, lighter substance than earthly things, the heavens must work according to a different set of rules than the earth.

            Around A.D. 100, a Greek astronomer living in Egypt, Ptolemy, provided support for Aristotle’s common-sense model of the universe. Rejecting earlier ideas that the earth rotated on its axis as it moved around the sun, Ptolemy worked out a complex mathematical explanation for the movements of the stars and planets based on Aristotle’s earth-centered, or geocentric, model. According to Ptolemy, the planets and stars all moved in perfect circles within their own spheres as the spheres moved in perfect circles around the earth.

            The geocentric model of the universe fit nicely with the basic doctrines of the Christian Church. The church taught that the whole purpose of creation, the central point of history, was the crucifixion and resurrection of Christ. As the stage on which this cosmic drama had been played out, they thought, the earth must be the center of the universe. Even the Bible suggested as much when it referred to the sun standing still, as it did for Joshua.

            Accepting the “authority” of Aristotle and Ptolemy, church leaders added their own Christian dimension to the model. The spheres beyond the moon, they believed, were the heavens, including Paradise. Angels worked to keep them in motion. Within the orbit of the moon, all things were earthly and tainted with the sin that humanity had brought into the world at the time of Adam and Eve. Since the heavens and the earth were not the same, one being divine and the other human, each had its own different set of laws. Perfection above and sin below became the official Christian view of the universe.

Plato’s view. The rediscovery of Plato during the Renaissance, however, challenged the church’s Aristotelian conceptions. Unlike Aristotle, Plato had not accepted the authority of the five senses in determining the nature of the universe. Plato looked beyond the appearances and insisted that behind all physical things lay an invisible reality—a perfect idea that was unchanging, rational, and simple. Even when this reality could not be detected with the senses, it could be described mathematically.

            Renaissance Europeans also rediscovered the work of the Neoplatonists and Pythagoras. The Neoplatonists had argued that the perfect idea behind a thing constituted its “soul.” Moreover, these souls were all part of the great World Soul, the ideal of the creation itself. The entire universe was thus alive and interconnected. There was no difference between the heavenly sphere and the earthly sphere; therefore, a single, universal set of rules must govern both. The Pythagoreans added the idea that everything in the universe was made up of numbers and the relationships, or ratios, between them. By understanding and manipulating these ratios, people could learn the rules of the universe and use them to control and change the world around them.

Magical background. The first Europeans to begin looking for these universal rules were not Scholastics but magicians, astrologers, and alchemists, most of whom were heavily influenced by Pythagorean and Neoplatonic philosophy. Unlike Scholastics, who usually wanted to understand the nature of the universe without trying to change it, practitioners of the magical "sciences" hoped to use their knowledge in very practical ways.

            Astrologers used complex mathematical calculations to determine the location of the heavenly bodies, whose positions and movements, they believed, affected the course of events on earth. Alchemists used mixtures of chemicals and earthly elements to find the “Philosopher’s stone,” which they believed could change worthless materials such as lead into precious material such as gold. Some saw this as a search for spiritual purification and enlightenment, but many simply hoped to get rich. As they mixed and reduced and distilled chemicals and compounds, alchemists laid the foundations for modern chemistry. The most famous alchemist, Paracelsus, discovered many basic chemical processes.

            Magicians and astrologers also contributed to mathematics, physics, astronomy, and medicine. Dr. John Dee, for example, an English magician and astrologer to Queen Elizabeth I, lectured on mathematics and used his skills to help English sailors develop new methods of navigation, even as he tried to make himself rich by commanding angels to lead him to buried treasure.[xv][xv] For like all his colleagues in the magical arts, Dee believed that the universe itself was in a sense alive, and that a spiritual hierarchy under God enforced its rules.

The Scientific Revolution: Looking Outward

As Europeans began to question the accepted authorities of the past, they also began to demolish the basic explanations those authorities had provided about how the world worked. In the early 1500s, for example, a Polish astronomer named Nicolaus Copernicus challenged the prevailing Ptolemaic view by claiming that the earth and other planets revolved around the sun. It was the opening blow in what we call today the Scientific Revolution.

            Copernicus had studied under Neoplatonists in Italy, where he had come across ancient Greek references that suggested the earth rotated on its axis and revolved around the sun. Although Aristotle and Ptolemy had rejected this notion, Copernicus was intrigued. The Polish astronomer found Ptolemy’s system too complex. Influenced by the mystical Pythagorean idea of numbers, he thought there must be a simpler explanation for all the movements in the heavens. He was also intrigued by the Neoplatonist revival of an ancient idea, that the sun, the source of warmth and light and therefore of life itself, was the manifestation of God in the physical universe. Consequently, Copernicus began to consider the idea of a heliocentric, or sun-centered, universe. After considerable study, he concluded that such a model of the universe would be both more accurate and less complicated than the geocentric model. Copernicus published his ideas in 1543 in a book called On the Revolutions of the Heavenly Spheres.

Kepler. In 1609, a brilliant mathematician in Germany named Johannes Kepler, who was also an astrologer and a mystic, used new mathematical formulas to prove Copernicus' heliocentric theory. Kepler had been the assistant of Tycho Brahe, a great Danish scholar who had used his wealth to build the finest observatory in Europe. Over many years Brahe made thousands of observations of the position and motion of the heavenly bodies. When he died, he left this information to Kepler. Ironically, Brahe, a devout Christian, worried about the spiritual implications of a sun-centered universe. He hoped Kepler would be able to use the information to prove the Ptolemaic not the Copernican theory!

            Drawing on Brahe’s observations as well as his own, however, at first Kepler could not make them fit either theory. Eventually he discovered the problem. Copernicus had been on the right track, but he too had accepted the idea that the planets moved in perfect circles around the earth. Kepler found that they moved in ovals, or ellipses. From this basic insight, Kepler developed his famous laws of planetary motion. Because Kepler's proof could not be seen, however, the only people who could understand his work were other mathematicians. It took an Italian professor of mathematics, Galileo Galilei, to prove both Kepler and Copernicus correct.

Galileo. Galileo was been born in Pisa in 1564, nearly 20 years after Copernicus' death. Although his family expected him to pursue a medical career, Galileo was more interested in studying the world outside the body. After teaching in Pisa, he became a professor of mathematics at the university in Padua. In 1610 he moved to Florence.

            In Florence, Galileo became fascinated with astronomy. Already a firm believer in Copernicus' theory, he wanted to observe the planetary bodies for himself. When he heard of a Dutch lens maker who had made a device for observing far away objects, called a telescope, Galileo quickly constructed his own. He used it first to investigate the surface of the moon, which he found very different from the way most people described it. According to Aristotle and the teachings of the church, heavenly objects must by nature be round and smooth, without bumps to break their perfection. Galileo saw something different: 

"The surface of the moon is not smooth, uniform, and precisely spherical as a great number of philosophers believe it (and the other heavenly bodies) to be, but is uneven, rough, and full of cavities and prominences . . . not unlike the face of the earth, relieved by chains of mountains and deep valleys."[xvi] 

Galileo also observed the rings of Saturn, the moons of Jupiter, sunspots, and a comet whose path would have shattered Aristotle's crystalline spheres if they had really existed. He published his findings in two great works, The Starry Messenger and Dialogues on the Two Great Systems of the World. Although the church condemned Galileo for his beliefs, his observations made it impossible for any true astronomer to accept a geocentric theory of the universe. Kepler, supported by Galileo’s observations, had shattered Aristotle's conception of the heavens. Galileo himself now began to demolish the rest of Aristotle’s explanation of the universe.

            Aristotle had argued that the natural state of all things in the universe was rest. Things only moved if some outside force were applied to them. A new set of experiments convinced Galileo this was not true. In Pisa, by dropping different sized spheres from the famous leaning tower, he found that objects would fall at the same rate no matter how much they weighed. He also showed how the speed of falling objects naturally accelerated. In Florence he continued these studies. In addition to working out the mathematical explanation for acceleration, Galileo found that things remained in whatever state they were, either rest or motion, unless acted upon by some outside force. With Galileo's discovery of this law of inertia, Aristotle’s universe was now a shambles.

Looking Inward

While scholars like Copernicus and Galileo looked outward to discover the mysteries of the stars and planets, others were looking inward, trying to understand the workings of the human body. There too, challenging ancient authorities proved crucial to achieving a better understanding of how things worked. In medicine, Europeans had traditionally looked to the ancient Greek physician Galen, whose studies of anatomy were the accepted basis of medical knowledge. In the 1500s, the Flemish doctor Andreas Vasalius challenged Galen’s work.

            Vasalius, a professor of medicine in Italy, conducted his own dissections of bodies for his classes. His own experience convinced him that Galen had not always been correct. Vasalius concluded that all descriptions of anatomy must be based on observation and experimentation, not philosophy. In 1543 he published On the Fabric of the Human Body, which revolutionized the European understanding of human anatomy. Following Vasalius's example, in 1628 an English doctor named William Harvey discovered the circulation of the blood through veins and arteries and described a beating heart as being like a mechanical pump.

            Meanwhile, just as the telescope was transforming conceptions about the larger world of the universe, a tool based on the same principles of optics also began to change ideas about the nature of the smaller world within. A Dutch scientist named Anton Van Leeuwenhoek used a new invention called the microscope, developed in the late 1500s, to study bacteria. Just as the telescope allowed Galileo to see objects far away, the microscope permitted people to see tiny forms of life never seen before. Using the new instrument, an English scientist named Robert Hooke discovered cells.

Toward a New World View

Galileo had destroyed the Aristotelian conception of the universe primarily through simple observations and measurements. Although Kepler had developed mathematical explanations for what happened, it was Galileo’s experiments, demonstrations by physical means that could be repeated by anyone, that finally won the day. The work of Vasalius, Harvey, and others interested in the human body had also been possible only by direct experimentation and observation. In England, this new process of experimentation and demonstration particularly intrigued another great thinker, Sir Francis Bacon.

Bacon. Like many others, Bacon became irritated by the constant reference to the authority of the ancients. For Bacon, Aristotle’s great fault lay not so much in his conclusions, as in the means by which he had arrived at them, in other words, his methodology. In his book, Novum Organum, Bacon rejected deductive reasoning and argued that with repeated experiments and observation one should develop a mass of experimental data, or information, from which to develop a general explanation. This process of reasoning from the specific to the general, known as inductive logic, would produce an explanation that could be tested in turn through other experiments. Relying on proof that could be physically demonstrated, Bacon’s approach became known as empiricism. Bacon himself defined the object of the “new science” eloquently: “Now the true and lawful goal of the sciences is none other than this: that human life be endowed with new discoveries and power.”

Descartes. Not all new thinkers in Europe shared Bacon’s contempt for deductive logic. In 1637, a Frenchman, René Descartes, published his own Discourse on Method. Descartes, like Bacon, disapproved of the blind acceptance of ancient authorities as a sound foundation for knowledge. For Descartes, however, there was nothing wrong with deducing knowledge from a basic idea—so long as the idea was true beyond any reasonable doubt. The trick was to find the right axioms, or true ideas, on which to base one’s logical deductions. For this certainty, Descartes turned to arithmetic and geometry, which provided axioms that were clear, simple, and unquestionably true. Even then, he believed, one should question all assumptions before accepting them, an attitude known as skepticism.  

"[I] was never to accept anything as true that I did not know to be evidently so; that is to say carefully to avoid precipitancy and prejudice, and to include in my judgments nothing more than what presented itself so clearly and so distinctly to my mind that I might have no occasion to place it in doubt."[xvii] 

            Descartes tried to develop a complete description of the universe on the basis of a single truth that he could personally accept as beyond doubt: “I think, therefore I am.” From his own existence as a thinking being, he further deduced the existence of an infinite being that was pure thought, or spirit—God—as well as a physical universe that existed apart from thought. Thus, Descartes saw the world divided into two distinct substances, thought or spirit, which he called mind, and physical matter that existed apart from mind. Known as Cartesian Dualism, this idea marked a fundamental shift in the European worldview that separated it from all other worldviews.

            Instead of a living universe in which every physical object had a spiritual counterpart, Descartes had proposed a physical universe composed of matter that was essentially dead, without any spiritual essence at all. Only mind, which allowed a being to think about and know itself, could be considered alive. Even animals, Descartes argued, were simply mechanisms without consciousness. The whole universe could be explained as something that operated not with consciousness but as a machine operates according to the basic laws of physics. This mechanistic philosophy became the foundation of the modern European view of the universe.

            Descartes, a devout Christian, never questioned the basic Christian idea that spirit, which he associated with mind, was the essence of God and therefore was more important than matter. At the same time, he believed that through their capacity for thought and reason human beings shared in both God's nature and his creativity. The material with which humans created was physical matter. This idea soon set western European science apart from its Indian and Chinese counterparts, which made little distinction between mind and matter. Accepting Descartes’ view, many Europeans not only came to believe that they could manipulate their physical environment to suit themselves, but that, as creators in their own right, it was proper for them to do so.

            Although Bacon and Descartes seemed to have taken opposite approaches to the pursuit of knowledge, in fact most European scholars soon realized that combining the two methods provided the most versatile and powerful means of acquiring knowledge. The combination of logical deductive reasoning from self-evident axioms or principles, and inductive reasoning from the collection and observation of data through repeatable experiments, provided the basis for a whole new way for human beings to think about themselves and their world. We call this new approach the scientific method.

Newton. Sir Isaac Newton, the man most responsible for the general acceptance of both the scientific method and Descartes’ new view of the universe, was born in England in the same year that Galileo died, 1642. Newton replaced the old Aristotelian and Ptolemaic worldview that Galileo and others had demolished. Even as a student he had been puzzled by a nagging question: If Copernicus and Galileo were right, then what held the heavenly bodies in their places and caused them to move? Fully aware of both Kepler's laws of planetary motion and Galileo's observations on the movement of objects on earth, Newton became convinced that the two seemingly different types of motion were somehow connected. After many years of research, in 1687 he published his conclusion in The Mathematical Principles of Natural Philosophy.

            Newton realized that the force that held the planets in their orbits, and the force that caused objects to fall to the earth, were one and the same. Galileo’s laws of falling bodies and Kepler’s laws of planetary motion were both examples of the law of universal gravitation. In the course of reaching this discovery, Newton also explained the laws of motion, and developed calculus, a mathematical means to describe and measure motion. In one sweeping system, he tied together the movement of all things in the heavens and on earth and thus delivered the deathblow to the old Aristotelian idea that the laws governing the heavenly spheres and those governing the earth were not the same. The universe was a seamless, single whole.

            Equally important, Newton's work reinforced Descartes' idea of a physical universe made up of matter that simply responded to mechanical laws of motion. No longer would most educated Europeans see the universe as a place in which everything moved according to the constant attention of God and his angels, or to some infinite underlying personal spiritual essence or soul. Although most still accepted God as the Creator, they now began to think of the creation as a kind of giant clock: once wound up by the divine clock maker, it moved according to the natural (and impersonal) universal laws of motion. So great was Newton's influence on scientific thought that the English poet Alexander Pope once wrote: 

"Nature and nature's laws lay hid by night;

God said 'Let Newton be' and all was light."[xviii] 

Newton’s system remained the basis of the European conception of the universe until the 20^th century.

Section 2 Review

IDENTIFY and explain the significance of the following:

deductive logic

geocentric universe

Nicolaus Copernicus

Scientific Revolution

heliocentric universe

Johannes Kepler

Tycho Brahe

laws of planetary motion

Galileo Galilei

telescope

inertia

Andreas Vasalius

William Harvey

Anton Van Leeuwenhoek

microscope

Robert Hooke

Sir Francis Bacon

methodology

inductive logic

empiricism

René Descartes

axiom

skepticism

mind and matter

Cartesian Dualism

scientific method