The Scientific Revolution

   Of all the changes that swept over Europe in the seventeenth and eighteenth centuries, the most widely influential was an epistemological transformation that we call the "scientific revolution." In the popular mind, we associate this revolution with natural science and technological change, but the scientific revolution was, in reality, a series of changes in the structure of European thought itself: systematic doubt, empirical and sensory verification, the abstraction of human knowledge into separate sciences, and the view that the world functions like a machine. These changes greatly changed the human experience of every other aspect of life, from individual life to the life of the group. This modification in world view can also be charted in painting, sculpture and architecture; you can see that people of the seventeenth and eighteenth centuries are looking at the world very differently.

Making the Universe Visible

   The scientific revolution did not happen all at once, nor did it begin at any set date. Realistically speaking, the scientific revolution that we associate with Galileo, Francis Bacon, and Isaac Newton, began much earlier. You can push the date back to the work of Nicolaus Copernicus at the beginning of the sixteenth century, or Leonardo da Vinci in the middle of the fifteenth. Even then, you haven't gone back far enough and you haven't included all the factors that contributed to the set of epistemological transformations that we call the scientific revolution.

Ancient Greece
Aristotle
Plato

   You're safer to find the origins of the scientific revolution in the European re-discovery of Aristotle in the twelfth and thirteenth centuries. Aristotle entered the European Middle Ages by means of the Islamic world, which had preserved both Aristotelean and Platonic philosophy after Europe had completely forgotten it. Originally, Aristotle based knowledge on a kind of empiricism: he would investigate a question by a) examining what everyone else had said about the matter, b) making several observations, and finally, c) deriving either general or probable principles on the matter from both a and b. This method of thinking, which is the theoretical origin of empirical thought, formed the rudiments of a new revolution in human thinking in the twelfth and thirteenth centuries. The earliest Aristoteleans were burned as heretics (in a medieval university, when they fired you, they really fired you&emdash;have you ever wondered where the expression might come from?). Eventually, Aristoteleanism was combined with church doctrine to form a hybrid type of inquiry: Scholasticism. Unlike Aristoteleanism, Scholasticism did not have a strong empirical bent, but some Aristotelean thinkers took to Aristotle's empiricism like a duck to water. In the thirteenth and fourteenth century, empirical science began to take off. People such as Roger Bacon conducted empirical investigations on natural phenomena, such as optics.

   The rage of all the medieval scientists, however, was alchemy . Now alchemy is a greatly misunderstood phenomenon&emdash;we associate it with mad monks trying to turn lead into gold. In the Middle Ages, however, it referred to a variety of questions; some of them were mystical and religious, but most were questions we would consider to be standard chemistry problems. The medievals had inherited the science from Islam, for chemistry was never a separate discipline in Greek or Roman thought. In fact, the words "chemistry" and "alchemy" are both Arabic words, as are many of the terms that you use in a chemistry course, such as "alkali," "alembic," and "alkane." Alchemy, or chemistry, is one of the most important scientific revolutions in the Middle Ages, for the people who worked on alchemical questions by and large invented most of the empirical methods that would form the cornerstone of empirical science in the seventeenth century. The most important of these scientists was Roger Bacon. Besides inventing gunpowder, Bacon devised the trial and error method of finding knowledge while cataloging very carefully all the circumstances of these trials. This is the germ of experimental science. The word "experiment" comes from the word "experience." An experiment, then, is an experience , but it is a controlled experience. What an experiment concludes is the following: if the experience of a natural phenomenon is controlled in a certain way, that experience will be identical to any repeated experience that is controlled in precisely the same way. Experimental science, then, requires that all factors that have gone into the experience of the natural phenomenon be cataloged in some way. This, by and large, is what Bacon invented in a rudimentary form.

   There was a scientific revolution of sorts in the high Middle Ages that in many ways rivalled the later scientific revolution in its sweeping changes, but all the cultural components were not in place. So the scientific revolution of the thirteenth and fourteenth centuries did not produce a way of thinking about the world that closely resembles our own (this is why some people think that there was little scientific "progress" in the Middle Ages). You see, even in the high Middle Ages, Europeans believed that the center of all truth and experience was in God and that an overweaning concern with material phenomenon was a serious neglect of one's soul and one's dependence on God. The medievals also deeply distrusted human perception. Not only was human perception variable and untrustworthy, the material world itself was deceptive. Rather than a vehicle for truth, the material world was put in place to actively distract humans from the real task--living the sort of life that would get you into heaven.

   It's hard to pinpoint the shift in these attitudes. The introduction of humanism in the fourteenth century was in large part based on the idea that human intellect and creativity were trustworthy, and human experience was, to some extent, a reliable base on which to hang knowledge. But the humanist revolution didn't happen all at once; the dichotomy between "experience" and "authority" was a vexed question throughout the fourteenth and fifteenth centuries. What should you believe? What your experience shows you? Or what authorities, including the church and the bible, tell you to believe?

   While it's hard to pinpoint the shift in European attitudes, the first, unambiguous statement of this shift in values comes in Leonardo da Vinci's treatise on painting:

Renaissance Readings

The Painter

Here, right here, in the eye, here forms, here colors, right here the character of every part and every thing of the universe, are concentrated to a single point. How marvelous that point is! . . . In this small space, the universe can be completely reproduced and rearranged in its entire vastness!

The argument Leonardo is making is that the entire universe can be made visible to human sight, and human vision can encompass the universe in the same way that God can encompass the universe. When Leonardo says that all the forms and colors of the universe are concentrated in the human eye as to a single point, he is reversing the medieval definition of God, which postulated that God was the single point in which all parts of the universe are gathered, as in Dante Alighieri's vision of God at the end of his poem, Paradise :

Within his depths I saw internalized, ingathered with love into his volume, all the scattered leaves of the universe: substances, accidents, and their characteristics, as if they were all combined, so that what I saw was a single point.

   This new perspective expressed by Leonardo was a profound shift in the European world view. In a fundamental way, it postulated that human experience was and should be the central concern of human beings. It also postulated that human sensory experience, especially vision, was not only a valid way of understanding the universe, it also made it possible for humans to understand anything whatsoever about the universe. Making the universe visible, then, became a shared project among a number of Europeans; extending human vision with microscopes and telescopes seemed like a good idea. Europeans had the scientific knowledge to produce microscopes and telescopes since the time of Bacon; no one really thought to make them until making all parts of the universe visible became a viable and valuable project.

Making the Universe Move

   It's hard for us to really understand, but the universe for most of human experience has been a small and very intimate place. We live in such a vast universe, both temporally and spatially, that the controversies surrounding the motions of the universe in the sixteenth and seventeenth century seem ludicrous. However, the universe for Europeans in the sixteenth century was very small. In its largest version, it could fit within the orbit of Pluto. When a Mesopotamian astrologer climbed his ziggurat, or a Renaissance astronomer climbed his tower, they weren't just getting a better view of the stars, they were literally getting closer.

   A small universe made a great deal of sense. Everyone could see that the universe moved; this perhaps is one of the oldest pieces of human knowledge. Not only did it move, it moved in a circular fashion. So human beings got very good at describing this circular motion; in particular, if the universe moves in a circular fashion, it must be moving around a center point. When they thought about the size of the universe, it was obvious to them that if the universe were too big, then the parts of the universe at the outer edge would be travelling at speeds of billions of miles per hour. Nothing could survive speeds like this. So the universe was a small place; the outer edge was fairly close; in fact, both the Egyptians and the Mesopotamians lived in a universe that would fit within the orbit of the moon.

   When it came time to define the central point of this circular motion, the answer was completely obvious. The stars moved in a circular motion around the earth. Look up in the sky and this becomes immediately evident. However, there were some astronomers in Greece who argued that the earth was not the center of the universe, but rather the sun. This was an elegant solution, for it explained all the quirky movements of the planets. While the stars moved in beautiful circles around the earth, the planets also moved in circles but sometimes they would move backwards; this is called precession. Even though placing the sun at the center of the universe solved the precession problem, it created a new one. This meant that the earth was moving in a circular orbit. It also meant that the earth was moving pretty darn fast. If the earth were moving at thousands of miles per hour then if you jumped straight up in the air, when you landed, you'd hit the ground ten or twelve miles away from the spot you started at. Everyone could see, however, that when you jumped straight up in the air, you landed on the spot you started from. (Until Isaac Newton, Europeans, Muslims, and Asians understood only one-half of the concept of inertia: things at rest stay at rest. They did not figure out that things in motion stay in motion).

   The Ptolemaic Universe: The scientific revolution really begins in Europe when Nicolaus Copernicus challenges the dominant model of the motion of the universe: Ptolemy's Almagest . Ptolemy wrestled with the problem of the motion of the universe and all the problems associated with regression. Since common sense dictated that the earth can't be moving (see the "jump" experiment in the previous paragraph), then the motions of the planets had to be described in such a way as to explain why they regularly go backwards. The universe, however, had to still remain logical, for precession was logical. One could fairly accurately predict when a planet would start moving backwards in the sky.

   Ptolemy solved the problem in two ways. First, he made the elliptical orbits eccentric, that is, while the planets still orbited around the sun, the center of the circle of their orbit was not the earth, but a point somewhere else. Each planetary orbit, then, had a different center of rotation. But this still didn't explain every instance of precession. So Ptolemy took the planets out of their orbital path and set them spinning around a moving point on the orbital path., like a tether-ball spinning around a moving pole. These extraorbital orbits Ptolemy called epicycles. The universe became a grand, nonsensical Rube Goldberg machine, with planets orbiting around points that orbited around the earth in uneven and unbalanced elliptical orbits. Even Ptolemy hated it. The great virtue of his scheme was that it fully accounted for all planetary precession; the downside is that it turned the universe into a messy room. So Ptolemey actually argued that the universe did not, in fact, move this way; he only argued that his system was a "mathematical fiction" that should be used only to predict the motions of the universe.

   Somewhere along the line, though, the astrologers and astronomers of the Islamic world decided that the Ptolemaic universe was, in fact, an accurate physical description of the motion of the universe. When Arabic science entered the European world in the twelfth and thirteenth centuries, so did the Ptolemaic world view. This view would go largely unchallenged for hundreds of years while the universe squeaked and wobbled in its eccentrics and epicycles.

   Nicolaus Copernicus: Copernicus (1473-1543) was the first major astronomer to challenge the Ptolemaic universe. Let's keep in mind, though, that Ptolemy had his critics&emdash;starting with Ptolemy himself. The Ptolemaic universe was, after all, a nonsensical affair; when King Alfonso of Spain was introduced to the system in the thirteenth century, he said, "If God had made the universe thus, he should have asked me for advice first." The result of this criticism was not one, but hundreds of versions of the Ptolemaic universe. Copernicus, in the year of his death, published On the Revolutions of the Heavenly Spheres . This book did not revise Ptolemy's system, as all previous criticisms had, but rather challenged the fundamental assumption of the Ptolemaic universe: that the earth was the center point of the revolution of the heavens. In many ways, Copernicus attempted to solve the problem of precession by coming up with the simplest possible explanation. By simply moving the sun to the center of the universe, almost all the problems with planetary precession disappeared (almost all). Copernicus was also a mystical philosopher; he believed that the sun not only symbolized but also contained God; putting the sun at the center of the universe was more than a mathematical solution, it also better explained the spiritual structure of the universe.

   The Copernican universe, however, was still nothing like our own. It was still a small and intimate place; moving the orbits of the stars out too far meant that they'd travel at impossible speeds. Copernicus also kept the Ptolemaic epicycles and argued that the planets moved in circular orbits. His system, though, was a far more accurate predictor of planetary motion than any that had been previously put forth. That, argued Copernicus, was more than enough to justify its adoption.

   Arabic numerals: We need, however, to step back and briefly discuss one other innovation of the middle ages: the adoption of Arabic numerals. For Arabic numerals made the Copernican revolution possible in a way that can't be overstressed. Before the adoption of Arabic science in the twelfth and thirteenth centuries, Europeans used the Roman numeral system. This is a subtractive number system: numbers are indicated by letters and the transition to higher letters is first preceded by subtraction:

I II III IV V

While people were fairly proficient at working with these numerals, calculation was not exactly a blazing fast process. Try multiplying MDMCXLVII by CCCLXXIII without converting them to Arabic numerals and see how fast you can do it.

   The Arabs, on the other hand, used a place number system, which is the number system that you've been trained on. It consisted of ten numerals; when all ten numerals were used up, then another place was added and numbers would then consist of two sets, or places, of numerals. The immense advantage of a place system (only the Mayans and the Hindus also developed place systems) is that you can do calculations extremely rapidly. When this system was introduced into Europe, learned people began to calculate like mad. Books upon books piled up filled with calculations from the hands of busy monks and busy students and busy university teachers adding and subtracting and multiplying and dividing.

   Books of astronomical calculations especially began to pile up: this was the beginning of mathematical astronomy. As astronomical observations and calculations piled up, the problems with the Ptolemaic universe also piled up. More than anything else, it was this pile of mathematical calculations that pushed Copernicus to radically revise the Ptolemaic universe.

   Tycho Brahe: The man who most greatly influenced the adoption of the Ptolemaic system was Tycho Brahe (1546-1601), who was one of those fanatics doing all those mathematical calculations of the motion of the universe. Tables and tables and tables of calculations. For a man with a boring profession, however, he led a singularly interesting life: temperamental, he had lost his nose to syphilis, or, rather, to the cure for syphilis; he was a raucous heavy drinker and he died a particularly just death for a heavy drinker. At a dinner with a prince, he drank a bit too much, and, since you were not allowed to leave the table until the person outranking you left the table, he waited out his full bladder until it burst and sent him to the heavens he had so lovingly observed and calculated.

   Brahe opposed the Copernican universe and vehemently argued that the earth was the center of the universe. In order to prove this, however, he cataloged a superhuman number of astronomical observations and calculations. These tables of calculations made up the best astronomical observations in any culture at any time up to that point and would become the basis for proving the Copernican system to be a more accurate model of the universe.

   Johannes Kepler: Like Copernicus, Kepler (1571-1630) believed that the sun represented the spiritual essence and presence of God and should be placed at the center of the universe. He discovered Brahe's observations and calculations and set about using them to develop a new, sun-centered universe. He rejected two major aspects of the Copernican universe: epicycles and circular orbits. In the Keplerian universe, the planets orbited around the sun and remained in their orbital paths; these paths, however, were elliptical rather than circular. This was the big prize: by revising Copernicus's model through the use of Brahe's calculations, he produced a mathematical model of the universe that perfectly predicted planetary motions and accounted for every instance of planetary precession. This model he published in the book New Astronomy in 1609, and it instantly created a sensation. It would also inspire an Italian astronomer, Galileo Galilei, to fit his new observations into this Keplerian universe.

   Even though the model was perfect in terms of its predictive power, it still had a number of problems. It still didn't explain why the earth didn't move out from under us when we jumped in the air. Also: why would the planets move elliptically? Circular orbits made sense, but elliptical orbits? Both of these questions would be answered by Newtonian physics a few decades later.

   Galileo Galilei: Galileo (1564-1642) combined the two roles of observer and theorist and, more than anyone else, provided the empirical discoveries that cinched the Copernican-Keplerian universe. First, in 1609, he eagerly read Kepler's New Astronomy and bought into it completely. That same year he bought a curious new Dutch invention, the telescope. While the telescope had been around for a few years, he was the first to use it to systematically look at the heavens. What he saw amazed even him.

   The first thing he saw was mountains on the moon. Until this time, the moon was regarded as more or less gaseous; the presence of mountains meant that the moon was terrestrial, just like earth. If it had mountains, it could also have plants and people. The second thing he saw were planets orbiting around the planet of Jupiter. Five, to be exact. This was the big banana. For if the planet of Jupiter was an independent orbital system orbiting around a larger system, that meant that the sun could also be an independent orbital system orbiting around a larger system. The universe, which until Galileo's time was a small and homey place, suddenly expanded infinitely outwards and became a vast and incomprehensible place.

   Galileo announced his findings in The Starry Messenger , which he published in 1610, one year after the publication of Kepler's New Astronomy . The Starry Messenger was really only a pamphlet, and Galileo would not write a full exposition of his observations and his model for a much larger universe until his Dialogues on the Two Chief Systems of the World . It was this book that inspired the Roman Catholic church to closely examine his observations and models and compare them to church doctrine and the texts of the Old and New Testament. The Church concluded that his ideas were at variance with both doctrine and Scriptures and demanded, on pain of death, that he recant his views.

   The one part of Galileo's system that most greatly influenced all subsequent European inquiry into the nature of the universe was his insistence that the universe operated according to mathematical principles. The circle, you might say, had been completed. The Ptolemaic universe was a mathematical model designed to assist predictions but was not designed to be a physical description of the universe. Both the Copernican and Keplerian systems were primarily proposed as mathematical rather than physical models. Galileo insisted that the two were coterminous, that all physical description of the universe would of necessity be a mathematical description. His revolutionary argument was this: if a physical model did not fit the mathematical properties of that phenomenon, the physical model was wrong. This would become the basis of a profound shift in European knowledge: classical mechanics.

Making the Universe Move Mechanically

   Francis Bacon: The grounds for a mechanical universe, that is, a universe that operated like a machine, was laid down by Galileo's insistence that the universe operated by predictable mathematical laws and models. In addition, Francis Bacon (1561-1626), added a key element to the genesis of the mechanical universe in his attacks on traditional knowledge. Bacon wasn't a scientist in our sense of the word, but he did take great joy in telling everybody why they were wrong. In particular, he argued that all the old systems of understanding should be abandoned: he called them idols. He believed that knowledge shouldn't be derived from books, but from experience itself. Europeans should move beyond their classics and observe all natural and human phenomena afresh. He proposed the Aristotelean model of induction and empiricism as the best model of human knowledge; in inductive thinking, one begins by observing the variety of phenomena and derives general principles to explain those observations. (In deductive thinking, one starts with general principles and uses these principles to account for the variety of phenomena). This model of systematic empirical induction was the piece that completed the puzzle in the European world view and made the scientific revolution possible.

**Isaac Newton**

   Isaac Newton: The mechanical universe in all its glory would emerge from the work of Isaac Newton (1642-1727) in his compendious The Mathematical Principles of Natural Philosophy (1687), which is primarily known by the first two words of its Latin title: Principia Mathematica . The fundamental arguments of the book were the following:

The universe could be explained completely through the use of mathematics; mathematical models of the universe were accurate physical descriptions of the universe.

The universe operated in a completely rational and predictable way following the mathematics used to describe the universe; the universe, then, was mechanistic.

One need not appeal to revealed religion or theology to explain any aspect of the physical phenomena of the universe.

All the planets and other objects in the universe moved according to a physical attraction between them, which is called gravity; this mutual attraction explained the orderly and mechanistic motions of the universe.

Ancient Greece
Aristotle
The Atomists

   Newton's mechanistic view of the universe is an idea that derives from Greek atomism, but Newton's mechanistic universe would become the dominant model in European thought for the next several centuries ( and still is). According to Newton, the universe was like a massive clock built by a creating god and set into motion. Actually, even though Newton was a devout Christian, this argument has a philosophical basis. For Newton based his entire view of the universe on the concept of inertia: every object remains at rest until moved by another object; every object in motion stays in motion until redirected or stopped by another object. (This latter principle explains why we can jump in the air without the earth moving out from under us). According to the concept of inertia, no object has the ability to move or stop itself. The universe, then, becomes a vast billiard ball table, in which everything moves because something else has just knocked into it or caused it to move.

But this leads to a serious philosophical problem: who moved the first object? How did the universe get going if no object can move itself? The Greek atomists, who believed that the universe consisted of atoms (in Greek the word atoma means "indivisibles") that create all phenomena by colliding into and combining with each other, explained this with the concept of "swerve": somewhere at the beginning of time, one atom swerved all by itself and knocked into another and hence the universe came into being. Aristotle, on the other hand, who also based his thought more or less on a mechanistic view of the universe, solved the problem by positing an "Unmoved Mover": somewhere at the beginning of time, an "Unmoved Mover" (which he calls God), was able to set things in motion without having to be moved itself. This idea was appropriated in the Middle Ages by the Scholastics, who, like Aristotle, believed the universe functioned in a rational and mechanistic way and was set in motion and ruled over by a rational and unmoving mover, God. Newton adopts this idea whole-cloth: although the universe is a vast machine of objects moving and colliding into each other and functioning by its own laws, it still requires some original thing that set it all in motion in the first place. That thing, for Newton, was God.

   But God did not interfere with the day to day workings of the universe (although Newton never denied that God couldn't, just that God didn't become involved). If the universe was a vast machine of interacting objects, that meant that it could be understood as a machine. Human reason and the simple observation of phenomena were sufficient to explain the universe; one need not drag religion or God into the explanation. If physical phenomena were mechanistic, that means that physical phenomena can be manipulated , that is, engineered. This mechanistic view of the universe, called classical mechanics, focuses entirely on the concept of motion, that is, at the base of Newton's thought is an attempt to explain why the universe moves. This is what physics is all about: why things change.

Enlightenment Glossary

Deism

   Newton's mechanistic view of the universe would soon be applied to other phenomena as well. If the universe was a machine and could be understood rationally, then so perhaps could economics, history, politics, and ethics (human character). It also followed that if economics, history, politics, and ethics were mechanical, they could be explained without recourse to religion or God and they could be manipulated as if they were machines, that is, they could be improved, engineered, and made to run better. As the Enlightenment developed, classical mechanics would give rise to a larger phenomenon, Deism, which is founded on the idea that all phenomena are fundamentally rational and mechanistic and can be explained in non-religious terms. All of modern Western knowledge and the majority of your experience is ultimately derived from this principle. Newton's separation of the mechanical universe from religious explanation and the Enlightenment concept of deism went further than this, however. If the universe was created by God and the universe was a rational place, that meant that God was rational. If one understood the workings of the universe, one understood the workings of the mind of God. So the separation of physical explanation from religious explanation was not as tightly enforced as it seems at first glance. The great innovation of this view for Western religion would be the Enlightenment insistence that religion itself be rational.

Western Science Moves

   All the pieces were now in place, fused there by Newton's elaborate concept of a mechanical universe. Eighteenth century science saw an explosion of empirical knowledge about the physical world. A virtual flood of empirical observations and calculations inspired not only an increase in knowledge, but a massive effort to systematize that knowledge as Newton had done. The scientific revolution of the eighteenth century is, above everything else, characterized by fanatical conversion of knowledge into rational systems.

   Biology: The greatest strides in systematizing an unsystematic science occurred in biology. While Galileo trained his new optical device on the stars and discovered new worlds, another optical device was being used to discover equally dramatic worlds in drops of water: the microscope. The earliest scientists to use the microscope, Robert Hooke in England, and Jan Swammerdam and Antony van Leeuwenhoek (1632-1723), found that plant and animal tissues were made out of rooms or cells, but they also discovered frightening and nonsensical monsters in mud puddles: hydras, ameobas, and equally baffling creatures.

   Systematizing this vast new catalogue of knowledge fell to a Swedish botanist, Karl von Linné (1707-1778), also known as Carolus Linnaeus. In his Systema Naturae , published in 1767, he cataloged all the living creatures into a single system that defined their morphological relations to one another: the Linnean classification system. Morphologically distinct living creatures he called "species," which means "individuals." Morphologically related species were called a "genus," which means "kind." And so on up a scale of more abstract morphological relationships: family, class, order, phylum, kingdom. Each individual species was marked by both its species and its genus name; this classification system, with some modifications, still dominates our understanding of the living world.

   There was no such concept as evolution in Linneaus's time. The morphological relationships between living creatures, then, were purely descriptive; they did not explain why living creatures seemed to have these morphological relationships nor why these relationships could be abstracted to such high levels. It was George Buffon (1707-1788) who tried to explain these relationships, but he couldn't really commit himself to an evolutionary theory. What troubled Buffon was the close morphological relationships between humans and primates; this implied that the account of creation in Christianity wasn't valid. Buffon was only willing to admit that it was possible that all the range of living creatures ultimately derived from a single species which had changed over time in the variety of its descent.

   Chemistry: Chemistry, you'll remember, was originally an Islamic import into European culture and served as the foundational science in the development of European empirical and experimental science. While chemical knowledge advanced in leaps and bounds from the thirteenth century onwards, nobody could really explain how chemical systems worked. There were a pile of theories, but none of them fully explained the range of chemical phenomena. A new system of understanding chemicals and elements was precipitated by the discovery of gases by Henry Cavendish and Joseph Priestley in the latter half of the eighteenth century. In 1766, Cavendish discovered hydrogen (but he didn't know what it was at the time) and found that it would not burn all by itself; however, when it was exposed to air, whooosh!, it burned like crazy. In 1774, Priestley discovered oxygen; if a candle were put in a tube filled with oxygen, it, too, burned like crazy. This was a great breakthrough. Up until this point, Europeans believed that fire was a separate element and the properties of combustion were derived from the properties of fire. Cavendish and Priestley had proven, however, that fire was caused by the mixture of things with a gas. Finally, Cavendish discovered that water, which was also considered to be an element, was, in fact, made up of two gases: hydrogen and oxygen. A new chemical model of the universe was forming: the world was made up of "compounds" of basic elements.

   The picture was put together by Antoine Lavoisier, who proved that burning was caused by oxidation, that is, the mixing of a substance with oxygen. He also proved that diamonds were made of carbon and, more importantly, argued that all living processes were at their heart chemical reactions. Finally, and most importantly, he forumulated the "law of conservation of mass," which argued that the amount of physical substance never changes in a chemical reaction. The only thing that changes is the nature of chemical combinations.

   Electricity: The most exciting of the new sciences, however, was electricity. In 1672, Otto von Guericke, was the first human to knowingly generate electricity using a machine, and in 1729, Stephen Gray demonstrated that electricity could be "transmitted" through metal filaments. The first electrical storage device was invented in 1745, the so-called "Leyden jar," and in 1749, Benjamin Franklin demonstrated that lightning was electricity by firing up a Leyden jar in a thunderstorm (this discovery led to the invention of the lightning rod). However, throughout the eighteenth century, electricity was the most abstract of the physical sciences. It was a toy, a bric-a-brac, in the scientific community because nobody could think of any real practical use for it.

   Medicine: Enormous amounts of knowledge were added to medical practice throughout the seventeenth and eighteenth centuries: anatomy, microscopic anatomy, the circulation of blood, inoculation (which Europeans learned from the Ottoman Muslims) and vaccination, and so on. Most important, however, was a new system of understanding human biological processes: pathology. Enlightenment medicine proposed that the body was a natural system that functioned in predictable and rational ways--that is, it operated like a machine. No surprise there. Disease was a malfunction, disease was the breaking down of this machine: this was pathology. All disease processes, then, could be understood as natural phenomena and the recovery of health was also a natural and rational phenomenon.

Richard Hooker