The event which most historians of science call the scientific revolution can be dated roughly as having begun in 1543, the year in which Nicolaus Copernicus published his De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres) and Andreas Vesalius published his De humani corporis fabrica (On the Fabric of the Human body). As with many historical demarcations, historians of science disagree about its boundaries, some seeing elements contributing to the revolution as early as the 11th century, and finding its last stages in chemistry and biology in the 18th and 19th centuries. There is general agreement, however, that the intervening period saw a fundamental transformation in scientific ideas in physics, astronomy and biology, in institutions supporting scientific investigation, and in the more widely held picture of the universe.
Significance of the "revolution"
Many contemporary writers and modern historians claim that there was a revolutionary change in world view. In 1611 the English poet, John Donne, wrote:
[The] new Philosophy calls all in doubt,
The Element of fire is quite put out;
The Sun is lost, and th'earth, and no man's wit
Can well direct him where to look for it....
'Tis all in pieces, all coherence gone;
The mid-twentieth century historian, Herbert Butterfield, was less disconcerted but saw the change as equally fundamental.
"Since that revolution overturned the authority in science not only of the middle ages but of the ancient world — since it ended not only in the eclipse of scholastic philosophy but in the destruction of Aristotelian physics — it outshines everything since the rise of Christianity and reduces the Renaissance and Reformation to the rank of mere episodes, mere internal displacements within the system of medieval Christendom.... [I]t looms so large as the real origin both of the modern world and of the modern mentality that our customary periodization of European history has become an anachronism and an encumbrance."
More recently, sociologist and historian of science Steven Shapin opened his book, The Scientific Revolution, with the paradoxical statement: "There was no such thing as the Scientific Revolution, and this is a book about it." Although historians of science continue to debate the exact meaning of the term, and even its validity, the Scientific Revolution still remains a useful concept to interpret the many changes in science.
A single change does not make a revolution. Among the new ideas which are seen to be revolutionary are:
- the replacement of the Earth by the Sun as the center of the universe,
- the replacement of the Aristotelian theory that matter was continuous and made up of the elements Earth, Water, Air, Fire, and Aether by rival ideas that matter was atomistic or corpuscular or that its chemical composition was even more complex,
- the replacement of the Aristotelian idea that by their nature, heavy bodies moved straight down toward their natural places; that by their nature, light bodies moved naturally straight up toward their natural place; and that by their nature, aethereal bodies moved in unchanging circular motions by the idea that all bodies are heavy and move according to the same physical laws,
- the replacement of the Aristotelian concept that all motions require the continued action of a cause by the inertial concept that motion is a state that, once started, continues indefinitely without the need for any further action of a cause, and
- the replacement of the Galenic treatment of the venous and arterial systems as two separate systems with Harvey's concept that Blood circulated from the arteries to the veins "impelled in a circle, and is in a state of ceaseless motion".
However, many of the important figures of the scientific revolution shared in the Renaissance respect for ancient learning and cited ancient pedigrees for their innovations. Copernicus, Kepler, and Newton all traced different ancient and medieval ancestries for the heliocentric system. While preparing a revised edition of his Principia, Newton attributed his law of gravity and his first law of motion to a range of historical figures. A few modern historians have agreed with Newton's view that the concept of inertia in his first law of motion was anticipated by Aristotle.
Many historians of science have seen other ancient and medieval antecedents of these ideas. It is widely accepted that Copernicus's De revolutionibus followed the outline and method set by Ptolemy in his Almagest and that Galileo's mathematical treatment of acceleration and his concept of impetus grew out of earlier medieval analyses of motion.
The standard theory of the history of the scientific revolution claims the seventeenth century was a period of revolutionary scientific changes. It is claimed that not only were there revolutionary theoretical and experimental developments, but that even more importantly, the way in which scientists worked was radically changed. Some claim that at the beginning of the century, science was highly Aristotelian, while at its end, science was mechanical, and empirical. But an alternative anti-revolutionist view is that science as exemplified by Newton's Principia was anti-mechanist and highly Aristotelian, being specifically directed at the refutation of anti-Aristotelian Cartesian mechanism, as evidenced in the Principia quotations below, and not more empirical than it already was at the beginning of the century or earlier in the works of such as Benedetti, Galileo, Kepler.
Ancient and medieval background
Ptolemaic model of the spheres for Venus, Mars, Jupiter, and Saturn. Georg von Peuerbach, Theoricae novae planetarum, 1474.
|The Scientific revolution built upon the foundation of ancient Greek learning, as it had been elaborated in medieval Islam and the schools and universities of medieval Europe. Though it had evolved considerably over the centuries, this "Aristotelian tradition" was still the dominant intellectual framework in 16th and 17th century Europe.
Key ideas from this period, which would be transformed fundamentally during the scientific revolution, include:
- Aristotle's cosmology which placed the Earth at the center of a spherical cosmos, with a hierarchical order to the Universe. The terrestrial and celestial regions were made up of different elements which had different kinds of natural movement.
- The terrestrial region, according to Aristotle, consisted of concentric spheres of the four elements—earth, water, air, and fire. All bodies naturally moved in straight lines until they reached the sphere appropriate to their elemental composition—their natural place. All other terrestrial motions were non-natural, or violent.
- The celestial region was made up of the fifth element, Ether, which was unchanging and moved naturally with circular motion. In the Aristotelian tradition, astronomical theories sought to explain the observed irregular motion of celestial objects through the combined effects of multiple uniform circular motions.
- The Ptolemaic model of planetary motion. Ptolemy's Almagest demonstrated that geometrical calculations could compute the exact positions of the Sun, Moon, stars, and planets in the future and in the past, and showed how these computational models were derived from astronomical observations. As such they formed the model for later astronomical developments. The physical basis for Ptolemaic models invoked layers of spherical shells, though the most complex models were inconsistent with this physical explanation.
- Galen's physiological system which located three vital functions in three different organs: the brain was the center of the nervous system which disseminates a subtle psychical spirit responsible for sensation; the heart was the center of the arterial system which disseminates arterial blood, bearing a vital spirit responsible for life; and the liver was the center of the venous system which disseminates the thick venous blood, bearing a natural spirit responsible for growth and nourishment. He also adopted the traditional Greek view that illness was the result of imbalance among four bodily humours: blood, phlegm, yellow bile, and black bile. Health could be restored by diet, by bleeding or purging, or by medication to restore the proper balance.
New approaches to nature
Historians of the Scientific Revolution traditionally maintain that its most important changes were in the way in which scientific investigation was conducted, as well as the philosophy underlying scientific developments. Among the main changes are the mechanical philosophy, the chemical philosophy, empiricism, and the increasing role of mathematics.
The mechanical philosophy
Aristotle recognized four kinds of causes, of which the most important was the "final cause". The final cause was the aim, goal, or purpose of something. Thus, the final cause of rain was to let plants grow. Until the scientific revolution, it was very natural to see such goals in nature. The world was inhabited by angels and demons, spirits and souls, occult powers and mystical principles. Scientists spoke about the 'soul of a magnet' as easily as they spoke about its velocity.
The rise of the so-called "mechanical philosophy" put a stop to this. The mechanists, of whom the most important one was René Descartes, rejected all goals, emotion and intelligence in nature. In this view the world consisted of particles of matter -- which lacked all active powers and were fundamentally inert -- with motion being caused by direct physical contact. Where nature had previously been imagined to be like an active entity, the mechanical philosophers viewed nature as following natural, physical laws.
The chemical philosophy
Chemistry, and its cousin alchemy, became an increasingly important aspect of scientific thought in the course of the sixteenth and seventeenth centuries. The importance of chemistry is indicated by the range of important scholars who actively engaged in chemical research. Among them were the astronomer Tycho Brahe the chemical physician Paracelsus, and the English philosophers Robert Boyle and Isaac Newton.
Unlike the mechanical philosophy, the chemical philosophy stressed the active powers of matter, which alchemists frequently expressed in terms of vital or active principles – of spirits operating in nature.
The Aristotelian scientific tradition's primary mode of interacting with the world was through observation and searching for "natural" circumstances. It saw what we would today consider "experiments" to be contrivances which at best revealed only contingent and un-universal facts about nature in an artificial state. Coupled with this approach was the belief that rare events which seemed to contradict theoretical models were "monsters", telling nothing about nature as it "naturally" was. During the scientific revolution, changing perceptions about the role of the scientist in respect to nature, the value of evidence, experimental or observed, led towards a scientific methodology in which empiricism played a large, but not absolute, role.
Under the influence of philosophers like Francis Bacon, an empirical tradition was developed in the 17th century. The Aristotelian belief of natural and artificial circumstances was abandoned, and a research tradition of systematic experimentation was slowly accepted throughout the scientific community. Bacon's philosophy of using an inductive approach to nature – to abandon assumption and to attempt to simply observe with an open mind – was in strict contrast with the earlier, Aristotelian approach of deduction, by which analysis of "known facts" produced further understanding. In practice, of course, many scientists (and philosophers) believed that a healthy mix of both was needed—the willingness to question assumptions, yet also interpret observations assumed to have some degree of validity.
At the end of the scientific revolution the organic, qualitative world of book-reading philosophers had been changed into a mechanical, mathematical world to be known through experimental research. Though it is certainly not true that Newtonian science was like modern science in all respects, it conceptually resembled ours in many ways—much more so than the Aristotelian science of a century earlier. Many of the hallmarks of modern science, especially in respect to the institution and profession of science, would not become standard until the mid-19th century.
In the Middle Ages mathematics was held to produce an inferior form of knowledge; mathematics could only describe, and sometimes predict, observed phenomena. Scientific knowledge, according to the Aristotelians, was concerned with establishing true and necessary causes of things. To the extent that medieval natural philosophers used mathematical techniques, they limited mathematics to theoretical analyses of local motion and other aspects of change. The actual measurement of a physical quantity, and the comparison of that measurement to a value computed on the basis of theory, was largely limited to the mathematical disciplines of astronomy and optics. In the sixteenth and seventeenth centuries, quantitative measurements were increasingly applied to the measurement of physical phenomena on the earth. Galileo maintained strongly that mathematics provided a kind of necessary certainty that could be compared to God's: "with regard to those few [mathematical propositions] which the human intellect does understand, I believe its knowledge equals the Divine in objective certainty."
Emergence of the revolution
Since the time of Voltaire, some observers have considered that a revolutionary change in thought, called in recent times a scientific revolution, took place around the year 1600; that is, that there were dramatic and historically rapid changes in the ways in which scholars thought about the physical world and studied it. Science, as it is treated in this account, is essentially understood and practiced in the modern world; with various "other narratives" or alternate ways of knowing omitted.
Alexandre Koyré coined the term and definition of 'The Scientific Revolution' in 1939, which later influenced the work of traditional historians A. Rupert Hall and J.D. Bernal and subsequent historiography on the subject (Steven Shapin, The Scientific Revolution, 1996). To some extent, this arises from different conceptions of what the revolution was; some of the rancor and cross-purposes in such debates may arise from lack of recognition of these fundamental differences. But it also and more crucially arises from disagreements over the historical facts about different theories and their logical analysis, e.g. Did Aristotle's dynamics deny the principle of inertia or not? Did science become mechanistic?
New scientific developments
About 1600, key ideas and people emerged:
- Nicolaus Copernicus (1473-1543) published On the Revolutions of the Heavenly Spheres in 1543 argued for the heliocentric theory of the solar system.
- Andreas Vesalius (1514-1564) published De Humani Corporis Fabrica (On the Fabric of the Human Body) (1543), which discredited Galen's views. He found that the circulation of blood resolved from pumping of the heart. He also assembled the first human skeleton from cutting open cadavers.
- William Gilbert (1544-1603) published On the Magnet and Magnetic Bodies, and on That Great Magnet the Earth in 1600.
- Tycho Brahe (1546-1601) made extensive and more accurate naked eye observations of the planets in the late 1500s which became the basic data for Kepler's studies.
- Sir Francis Bacon (1561-1626), whose most famous scientific experiment involved stuffing snow into a dead chicken, nevertheless advanced inductive reasoning, proceeding from observation and experimentation.
- Galileo Galilei (1564-1642) improved the telescope and made several astonishing (for the time) astronomical observations such as the phases of Venus and the moons of Jupiter, which he published in 1610. He developed the laws for falling bodies based on pioneering quantitative experiments which he analyzed mathematically.
- Johannes Kepler (1571-1630) published the first two of his three laws of planetary motion in 1609.
- William Harvey (1578-1657) demonstrated that blood circulates via dissections and various other experimental techniques.
- René Descartes (1596-1650) pioneered deductive reasoning, publishing in 1637 Discourse on Method.
- Antony van Leeuwenhoek (1632-1723) constructed powerful single lens microscopes and made extensive observations that he published in about 1660 began to open up the micro-world of biology.
- Isaac Newton (1642-1727) built upon the work of Kepler and Galilei. His development of the calculus opened up new applications of the methods of mathematics to science. He showed that an inverse square law for gravity explained the elliptical orbits of the planets, and advanced the theory of Universal Gravitation. Newton believed that scientific theory should be coupled with rigid experimentation.
In 1543 Copernicus' work on the heliocentric model of the solar system was published, in which he tried to proved that the sun was the center of the universe. Ironically, this was the opposite of the ideas of the Roman Catholic Church as part of the Counter Reformation. efforts for a means of creating a more accurate calendar for its activities. For almost two millennia, the geocentric model had been accepted by all but a few astronomers. The idea that the earth moved around the sun, as advocated by Copernicus, was to most of his contemporaries preposterous. It contradicted not only the virtually unquestioned Aristotelian philosophy, but also common sense. For suppose the earth turns about its own axis. Then, surely, if we were to drop a stone from a high tower, the earth would rotate beneath it while it fell, thus causing the stone to land some space away from the tower's bottom. This effect is not observed. Furthermore, the centripetal force exerted by a spinning body--especially one that would have to rotate as quickly as the Earth must, given that in the 16th century, the size of the planet and the length of a day were well and accurately known--would fling objects from its surface. It would take Newton's developments inertia and gravity to set these objections to rest, respectively.
It is no wonder, then, that although some astronomers used the Copernican system to calculate the movement of the planets, only a handful actually accepted it as true theory. It took the efforts of two men, Johannes Kepler and Galileo, to give it credibility. Kepler was a brilliant astronomer who, using the very accurate observations of Tycho Brahe, realized that the planets move around the sun not in circular orbits, but in elliptical ones. Together with his other laws of planetary motion, this allowed him to create a model of the solar system that was a huge improvement over Copernicus' original system. Galileo's main contributions to the acceptance of the heliocentric system were his mechanics and the observations he made with his telescope, as well as his detailed presentation of the case for the system (which led to his condemnation by the Inquisition). Using an early theory of inertia, Galileo could explain why rocks dropped from a tower fall straight down even if the earth rotates. His observations of the moons of Jupiter, the phases of Venus, the spots on the sun, and mountains on the moon all helped to discredit the Aristotelian philosophy and the Ptolemaic theory of the solar system. Through their combined discoveries, the heliocentric system gained more and more support, and at the end of the 17th century it was generally accepted by astronomers.
Kepler's laws of planetary motion and Galileo's mechanics culminated in the work of Isaac Newton. His laws of motion were to be the solid foundation of mechanics; his law of universal gravitation combined terrestrial and celestial mechanics into one great system that seemed to be able to describe the whole world in mathematical formulae.
Not only astronomy and mechanics were greatly changed. Optics, for instance, was revolutionized by people like Robert Hooke, Christiaan Huygens, René Descartes and, once again, Isaac Newton, who developed mathematical theories of light as either waves (Huygens) or particles (Newton). Similar developments could be seen in chemistry, biology and other sciences, although their full development into modern science was delayed for a century or more.
Not all historians of science are agreed that there was any revolution in the sixteenth or seventeenth century. For a contrary view, see the article Continuity thesis.
Another contrary view has been recently proposed by Arun Bala in his dialogical history of the birth of modern science. Bala argues that the changes involved in the Scientific Revolution – the mathematical realist turn, the mechanical philosophy, the corpuscular (atomic) philosophy, the central role assigned to the sun in Copernican heliocentrism - have to be seen as rooted in multicultural influences on Europe. Arabic science gave the first exemplar of a mathematical realist theory with Alhazen optics in which physical light rays traveled along mathematical straight lines. The swift transfer of Chinese mechanical technologies in the medieval era shifted European sensibilities to perceive the world in the image of a machine. The Indian number system, which developed in close association with atomism in India, carried implicitly a new mode of mathematical atomic thinking. And the heliocentric theory which assigned central status to the sun, as well as the Newton’s concept of force acting at a distance, were rooted in ancient Egyptian religious ideas associated with Hermeticism. Bala argues that by ignoring such multicultural impacts we have been led to a Eurocentric conception of the the Scientific Revolution.