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Science

Renaissance scientists made major discoveries in a variety of fields, from the study of animals and plants to the analysis of motion, light, and sound. They also developed many ideas and techniques that are central to modern science, such as the reliance on observation and experience and the use of experiments to test theories. However, the term science had a much broader meaning in the Renaissance than it does today. The word could refer to several fields of study, such as alchemy*, astrology*, and magic, that the modern world does not regard as scientific.

THE MEANING OF SCIENCE

Renaissance thinkers based their concept of science on the writings of the ancient Greek philosopher ARISTOTLE, who defined science as knowledge that is certain and unchanging. Aristotle claimed that a person gained perfect knowledge of an object by knowing its cause. The cause of an object, he claimed, made it what it was, and made it impossible for it to be anything else. Thus, Aristotle saw scientific knowledge as fixed and not subject to change. For him, a scientific explanation had to involve a logical proof that one thing was the cause of another.

Since Aristotle's time, however, the concept of science had broadened to include less perfect types of knowledge. Over the course of the Middle Ages, and even more during the Renaissance, thinkers came to recognize that the kind of arguments Aristotle saw as "proof" always involved some amount of speculation. Thus, they began accepting theories that only identified the probable cause of a thing or event, rather than "proving" its cause. They also gave more credit to theories that could predict actual events, such as eclipses, without explaining why they occur.

Renaissance scholars divided science into two main types. The speculative sciences were concerned with knowledge for its own sake. The practical sciences, by contrast, focused on applying knowledge to everyday problems. Each of these broad categories included several more specific fields.

The speculative sciences covered three major areas: mathematics, metaphysics*, and natural philosophy. Of these three, only natural philosophy resembled the modern concept of science. This field, also known as natural science, dealt with the physical world. It included such disciplines as botany (the study of plants), geology (the study of the earth), and zoology (the study of animals). The speculative sciences also included some "mixed sciences" such as mathematical physics, which covered the same subjects as natural science, but examined them in terms of mathematical ideas.

While the speculative sciences dealt with what human beings could know, practical sciences dealt with what human beings could do or make. Renaissance thinkers saw the practical sciences as very close to the arts, and they viewed some fields, such as logic and medicine, as both arts and sciences. Practical sciences during the Renaissance included medicine, engineering, and the "moral sciences" of ethics* and politics.

NATURAL SCIENCES

The natural philosophy of the Renaissance was the basis of the disciplines now known as natural sciences. Several factors helped advance the study of natural philosophy. First, better translations of the classical* works on science became available. Scholars also rediscovered ancient sources that provided alternate views of nature. Perhaps the most important change, however, was the development of new ideas and new approaches in science.

Mathematicians had long relied on the use of suppositions, or hypotheses—ideas that they assumed to be true in order to test an argument. As mathematics and physics began to overlap more in the 1500s, scientists began using the same technique. The famous Italian scientist Galileo GALILEI (1564–1642) was one of the first to use experiments to test his proposed ideas. The use of hypotheses and experiments was a major breakthrough in the development of modern science.

Botany. Since prehistoric times, humans had used plants for food, medicine, and other purposes. However, until the Renaissance, there were few attempts to study or describe plants in a systematic manner. The science of botany emerged in the 1400s as a result of several factors, including the revival of classical texts, the discovery of new plants, and the growth of printing, which made it much easier to reproduce pictures and descriptions of plants. Renaissance botany dealt mainly with the medical uses of plants and with identifying plants mentioned in ancient texts. In the later Renaissance, botanists focused more on classifying plants and describing their physical and chemical properties.

Two types of botany texts were widely available in the Renaissance. The first type, known as an herbal, was a list of plants—usually in alphabetical order—along with a brief description of each one, including its habitat and its medical uses. The only illustrations in the earliest printed herbals were woodcuts* based on drawings from medieval* texts, which barely resembled the actual plants. Some later herbals featured more realistic images drawn from life. The other common botany texts were new editions of ancient botanical works, such as Natural History by the Roman author Pliny the Elder and On the Materials of Medicine by the Greek physician Pedanius Dioscorides. The study of these classical texts raised suspicions among scholars that the ancients might not have known all the plants in the world.

In 1530 the scholar Otto Brunfels gave the illustrated herbal a distinctly Renaissance form with his Living Images of Plants. The woodcut illustrations, prepared from drawings made by a student of the famous German artist Albrecht DÜRER, were incredibly lifelike. Some pictures even showed the insect holes and withered leaves on individual plants. The text quoted new editions of classical authors and attacked medieval physicians' ignorance of plants.

Brunfels's success led others to follow in his footsteps. In 1542 Leonhard Fuchs, a German professor of medicine, published Notable Commentaries on the History of Plants. The simple line drawings in this volume could be printed at very small sizes while still showing each plant clearly, making them suitable for use in pocket-sized field manuals. Fuchs's text also included many New World plants not known to the ancients, such as maize (corn). In addition, it featured a glossary of old and new terms for the parts of plants.

By the late 1500s the number of known plants had grown to 6,000—ten times the number listed in Dioscorides' text. These newly discovered plants included many from beyond Europe, and specialized books began to appear about the plants of different lands. Scholars found it difficult to name and classify all these new plants. Over 200 different authorities existed, each with its own set of plant names. The confusion over names made it harder to classify plants. Some texts claimed to arrange plants according to similarities, but the guidelines for similarity—such as habitat, growth pattern, or visible features—differed from one book to the next.

Beginning in the 1530s, humanist* scholars reformed the teaching of medicine to reflect the advances in botany. Formal lectures on the medicinal uses of plants drew on new editions of texts by Dioscorides and the ancient Greek physician GALEN. Instructors also began to place more emphasis on direct, hands-on experience. Professors took students on botanical field trips and conducted demonstrations of plants in botanical gardens. An Italian teacher of botany developed a new type of study aid called an herbarium, which contained pressed and dried plants preserved on sheets of paper.

Zoology. During the Renaissance, the study of animals was based on texts and descriptions rather than on real-world experience. Universities emphasized the teachings of Aristotle, which inspired them to group living things into a value-based hierarchy*. Other classical authors, such as Pliny, focused on tales of animals rather than descriptions of them. These writers tended to include mythical creatures, such as unicorns, in their texts. They often assigned human traits to animals.

Like botany, zoology had strong ties to medicine. Most zoologists were physicians who studied stories of animals to seek ingredients for medical cures. Most of what scholars knew at the time about the structure and function of the human body was based on parallels drawn from dissecting* animals such as pigs and apes. Scientists also studied animals to learn more about their roles in transportation, nutrition, and sports.

Humanist activity encouraged the study of zoology as scholars restored the original versions of ancient texts. Works by Aristotle, Pliny, and other classical writers appeared in print in the late 1400s. Other factors promoted the growth of zoology as well. For example, Renaissance artists such as Albrecht DÜRER and LEONARDO DA VINCI created lifelike portraits of animals. The practice of letter writing also advanced the science by giving scholars a way to exchange information. World travelers brought back reports of new animals in other lands—though these reports were often false or exaggerated. Wealthy and powerful individuals, such as popes, set up their own menageries (the forerunners of modern zoos) to display exotic creatures, such as monkeys and elephants.

During the 1500s scientists who wrote about nature relied mostly on evidence from books. In their eagerness to cover as many ancient sources as possible, they often discussed mythical creatures such as the phoenix that had been included in classical texts. Some of them also accepted as fact the claims of ancient authors that rotting wood could breed a certain type of geese. However, other scientists disproved the theories of ancient authors by dissecting actual animals. The Italian medical scholar Gabriele Falloppio, for instance, countered Aristotle's claim that lions have solid bones with no marrow in them. Similarly, Swiss physician Conrad Gesner disproved the belief that the liver of a mouse grows and shrinks with the phases of the moon.

While knowledge of animals increased, classifying them remained difficult. Scholars used a variety of methods for sorting animals into categories. Aristotle had grouped animals according to their structure, development, and habitat. Another common division involved several categories, including quadrupeds (four-footed creatures), birds, and fish. However, even these large groupings left room for confusion. For example, one text included a picture of a bat nursing, yet described the animal as a bird. Gesner suggested adding further branches to the four basic groups of animals, such as wild versus tame and hornless versus horned.

PHYSICS

During the Renaissance, the modern science of physics did not exist. The Renaissance concept of physics reflected the ideas outlined in Aristotle's Physics, which laid out a basic philosophy of nature. However, scientists of the time were studying many of the areas that make up modern physics, such as mechanics (the study of forces at work), optics (the study of light), and acoustics (the study of sound).

Mechanics. In its earliest form, the science of mechanics dealt with weights and the movement of heavy bodies. Renaissance scholars used a variety of sources to study mechanics. Two of the most important were Aristotle's Physics and another work called Mechanics, thought to be Aristotle's but actually written by one of his students. Scholars also relied on texts by ancient Greek mathematicians, such as Archimedes, Hero, and Pappus, and on treatises* about the medieval science of weights. The work of engineers who designed and built machines also contributed to the science of mechanics.

The earliest studies of mechanics occurred in the field now known as statics, which deals with the forces exerted by bodies at rest. The central idea of statics is the law of the balance, which tells how applying weights or forces at certain distances from a fulcrum, or balancing point, will bring the entire system to rest. The ancient Greeks had developed two ways to prove this law. The first, which involved calculating the ratios between the forces and distances involved, assumed that all the bodies were at rest. The other proof treated the bodies involved as if they were moving in a circle around the fulcrum. Renaissance mathematicians eventually came to favor the first proof, which led them emphasize the mathematical aspects of mechanics over its physical aspects.

In the 1300s scholars at Oxford University made advances in the study of bodies in motion. They developed laws more sophisticated than Aristotle's for analyzing the forces that move bodies and created rules for calculating the distances bodies travel in various periods of time. Scientists in Paris applied these new discoveries to the fields of physics and astronomy. In the mid-1500s the Spanish scholar Domingo de Soto sought, with limited success, to find common ground between Aristotle's laws of motion and those discovered at Oxford. De Soto also made a major contribution in 1551 when he suggested that the speed of a falling body changes steadily over time.

Galileo made the last great discoveries in Renaissance mechanics. His work in the field began in 1590, when he challenged one of Aristotle's laws of motion. Aristotle had claimed that the speed of a falling object depends on its weight and on the resistance it encounters. Galileo claimed that what mattered was not the absolute weight of the object, but its weight minus the weight of the volume of air, water, or some other medium that it displaced as it fell. Thus, two objects of unequal size made of the same material would fall at the same speed through a given medium.

Beginning around 1593 Galileo taught a course in mechanics at the University of Padua. In this course he used the law of balance to calculate the mechanical advantage of various simple machines, such as the screw and the lever. In the early 1600s Galileo performed a series of experiments with pendulums and inclined planes to study the properties of falling bodies. Eventually he determined that the speed of a falling object varies according to how long it has been falling, rather than on how far it has fallen. In a series of clever "tabletop" experiments, he succeeded in proving that the speed of a falling body increases steadily with time. After 1610 Galileo turned his attention to astronomy for many years. It was not until 1638 that he published Two New Sciences, which became the basis of modern mechanics.

Optics. The science of optics deals with the study of reflected and refracted (bent) light, as well as with the nature of light and theories of human vision. The most influential medieval work on this subject was Optics, by the Arab thinker known to the West as Alhazen. Drawing on anatomical, physical, and mathematical texts by ancient Greek scholars, Alhazen developed the idea that each point on the surface of an object gives off rays that strike the eye. About 1270 the Polish monk Witelo reworked Alhazen's ideas, along with those of various other authors, in a book titled Perspective. Early Renaissance scholars, however, largely ignored these medieval sources in favor of classical texts. For example, in 1486 the monk Gregorius Reisch published an encyclopedic work that drew on the ideas of ancient Stoic philosophers, who described vision in terms of a series of images that moves from the object to the eye of the viewer.

In 1572 scholar Friedrich Risner published his Thesaurus of Optics. This text combined Optics and Perspective in a single volume and was the first printed version of Alhazen's work. Risner prepared this book by comparing the texts of several different manuscripts. He also divided the book into sections, redrew the figures, and added references to link parts of Alhazen's work to that of Witelo. The book had a major influence on future studies of optics.

The work of German astronomer Johannes KEPLER laid the foundation for the modern science of optics. His Supplement to Witelo, published in 1604, explored such topics as reflection, refraction, the nature of light, and the relationship between light and color. Kepler also developed a theory of vision that stated that light rays enter the eye and create an upside-down image on the retina. He was the first to understand the role of the retina in vision.

One of the most important developments in optics during the Renaissance was the use of lenses to magnify the size of objects. This idea was not completely new. Eyeglasses had existed as early as 1313, and by 1500 the use of lenses to improve vision was common throughout Europe. However, making eyeglasses was the work of craftspeople, rather than scientists, and was not related to writings on optics. In 1593 the Italian humanist Giambattista della Porta published On Refraction, which described a series of experiments that combined convex lenses, which curve outward, with concave ones, which curve inward. By 1608 instrument makers in the Netherlands had put this idea to use, creating spyglasses that used two lenses to magnify images to three times their normal size.

Galileo began improving on the spyglass and developed an instrument that could magnify images 30 times. He used his new tool to study and describe the features of the moon's surface, the moons of Jupiter, and many new stars. In 1610 he published his discoveries in the book Sidereal* Messenger. The book stirred controversy about the value of the telescope. A critic in Florence attacked Galileo, denying that images seen through a telescope were real. Kepler responded by declaring his belief in the value of the telescope and the reality of Galileo's observations.

Acoustics. The science of acoustics deals with the physics of sound and the ways that humans hear sounds. For much of the 1400s, scholars and musicians based their understanding of sound on the book Fundamentals of Music, by the Roman scholar Anicius Boethius (480–524). This work combined the theories of various ancient Greek authorities in a single text. Boethius defined sound as a vibration of air that reaches a listening ear. Although a sound wave is actually a series of pulses, the ear senses it as a continuous tone, which is higher or lower depending on how fast the air is moving. Measuring the rate of the pulses, he argued, made it possible to assign a number to a pitch and compare it to the pitch of other notes.

Boethius agreed with the Greek author Pythagoras that only certain ratios between pitches would produce consonances—mixtures of high and low tones that were pleasing to the ear. He believed that simple ratios, like 2:1 or 3:2, produced pleasing sounds. Because there was no way to measure the speed of the vibrations in the air directly, Boethius focused on the size of the objects that produced the sounds. He referred to a legend about Pythagoras hearing consonances coming from a black-smith's shop and speculating that the combinations of pitches resulted from hammers of differing weights striking the anvil. Later scholars, however, proved that the weight of a hammer does not affect the pitch of the sound it produces.

While some parts of Boethius's work used Pythagorean ideas, in other sections he quoted authors who defined consonance and dissonance (a displeasing blend of tones) purely in terms of the listener's judgment. During the 1500s musical theorists argued over whether to define consonance in terms of mathematical ratios or listener reactions. Physicist Giovanni Benedetti analyzed the motion of strings and suggested that a consonance depended on having two vibrating strings pass through the central point of their vibration at exactly the same instant. The more often this happened, the more perfect the interval between the two notes would sound. For instance, if the two strings were tuned exactly one octave apart, then the lower string would be in its central position exactly half the time that the higher one was. Thus, the ear perceived the octave as a consonance.

Another major discovery of the 1500s had to do with sympathetic vibration. This occurs when the sound waves produced by one vibrating object, such as a string, set off vibrations in another object. Italian scholar Girolamo Fracastoro suggested that a vibrating string produces a sound by causing the air to compress and decompress in a series of pulses. When these waves of compressed air hit another string, they will cause it to vibrate if it is tuned to the same pitch as the first object. If the second string is tuned to a different note, it will interfere with the motion of the air and no sound will be produced.

CHEMISTRY

The modern science of chemistry arose out of the "chemical philosophy" of the Renaissance. This philosophy, in turn, grew out of the work of alchemists, especially the Swiss physician PARACELSUS (1493–1541). Chemical philosophers sought to identify the basic elements of which things were made. Some of them focused their attention on the study of metals and minerals. Others, such as Paracelsus, aimed to discover new medical uses for various substances. Some of their methods hinted at the techniques that would later be useful in the labs of modern chemists. However, most chemical philosophers did not make a distinction between their field and alchemy, which also contained magical and mystical* elements.

Metallurgy. Many early advances in chemistry occurred in the field of metallurgy (the study of metals). Italian scholar Vannoccio Biringuccio made several major discoveries in this field. Although he based his theories on the works of Aristotle, his methods were much more modern. In On Pyrotechnics, published in 1540, he wrote at length about metallic ores and how to analyze them and prepare them for smelting. He also discussed alloys (blends of two or more metals) and "semiminerals" such as mercury and sulfur.

German scholars Georgius Agricola and Lazarus Ercker also published influential works on mining and metallurgy. Agricola's On Metals was a thorough survey of what Renaissance scholars knew about metals, including how to work with them. Ercker's Description, published in 1574, built on Agricola's work. It explained how to obtain and refine various metals and use them to produce acids, salts, and other compounds. Some consider this text the first manual of analytical and metallurgical chemistry.

Medical Chemistry. Paracelsus pioneered the field of medical chemistry. Unlike most doctors of his time, he favored the use of powerful drugs designed to treat specific diseases. He developed several new laboratory procedures to refine chemical substances for medical purposes, such as a method of concentrating alcohol by purifying and freezing it. He was also the first scientist to group chemicals according to how easy it was to perform certain chemical processes on them.

German scientists of the mid-1500s took the lead in expanding medical chemistry into a more complete field. Adam of Bodenstein edited and translated Paracelsus's works, focusing on the relationship between minerals and medicine. He also recommended the use of metallic compounds for treating disease. German scholar Andreas Libavius, by contrast, opposed the ideas of Paracelsus. The last edition of his book Alchymia, published in 1606, included plans for building a chemical laboratory. The text contained more than 200 designs and pictures of chemical glassware, furnaces, and devices. Many modern scholars view Libavius as the founder of chemical analysis. Another leading medical chemist in Germany was Oswald Croll, who performed experiments to determine the chemical properties of the drugs he used. His book Chemical Edifice (1609) described his preparations in detail and explained how to use them. It became the first textbook of medical chemistry, used for a course in the subject at the University of Marburg.

In France, scientist Guy de La Brosse combined his knowledge of botany with an interest in medicine and chemistry. De la Brosse admired Paracelsus because he had stressed the importance of experiments and direct experience and had opposed the ideas of ancient scholars such as Aristotle and Galen. In 1628 de la Brosse published a work on the nature of plants that he described as a "general treatise on chemistry." According to de la Brosse, the basic idea of chemistry is that everything can be broken down into the basic elements of which it is formed. Reducing a substance in this way, he argued, is the only way to understand it fully.

Belgian scientist Jan van Helmont (1579–1644) made several major discoveries in medicine and chemistry. He relied heavily on the use of experiments to test different substances. He analyzed smoke chemically and described it as a gas with specific properties based on the substance that produced it. Helmont identified several gases produced by burning different substances, including carbon dioxide from charcoal and "explosive gas" from gunpowder. He also designed methods for preparing various acids from substances such as clay and salt.

While Helmont made many practical discoveries, Daniel Sennert of Germany was responsible for the most important advances in the theory of chemistry. He aimed to find common ground between the ideas of Paracelsus, Aristotle, Galen, and other ancient scholars. Sennert argued that all natural objects could be reduced to certain basic parts. He thought of these parts as very small particles, or minima. He viewed a chemical reaction as an object splitting into specific minima, which then moved around and reformed to create a new substance with its own properties. The minima themselves, he claimed, could never be created, destroyed, or changed. Sennert saw the science of chemistry not just as an aid to the practice of medicine, but as a separate field with the goal of breaking down natural substances and prepare them for other uses.

(See also Alchemy; Anatomy; Astronomy; Humanism; Magic and Astrology; Mathematics; Medicine; Mining and Metallurgy; Scientific Instruments; Scientific Method; Technology.)

* alchemy

early science that sought to explain the nature of matter and to transform base metals, such as lead, into gold

* astrology

study of the supposed influences of the stars and planets on earthly events

* metaphysics

branch of philosophy concerned with the nature of reality and existence

* ethics

branch of philosophy concerned with questions of right and wrong

* classical

in the tradition of ancient Greece and Rome

See color plate 6, vol. 4

* woodcut

print made from a block of wood with an image carved into it

* medieval

referring to the Middle Ages, a period that began around A.D. 400 and ended around 1400 in Italy and 1500 in the rest of Europe

* humanist

referring to a Renaissance cultural movement promoting the study of the humanities (the languages, literature, and history of ancient Greece and Rome) as a guide to living

* hierarchy

organization of a group into higher and lower levels

* dissect

to cut open a body to examine its inner parts

* treatise

long, detailed essay

Plant Look-Alikes

Most botanists of the 1500s named, pictured, and described plants without attaching any special importance to their outward appearance. However, some held to the longstanding belief that God had made plants look like human organs to reveal their medical properties. The physician Paracelsus supported this view and proposed such remedies as the use of walnuts to treat brain ailments because a walnut resembles the brain.

* sidereal

relating to the stars

* mystical

based on a belief in the idea of a direct, personal union with the divine

Living Rocks

During the Renaissance, scholars first began to suggest that fossils were not merely stones, but objects that had once been living beings. In 1547 the Italian scholar Girolamo Cardano argued that some fossils found on mountainsides had come from sea creatures. However, he rejected the suggestion that the great flood described in the Bible had deposited these fossils on land. In 1566 Conrad Gesner of Switzerland sorted fossils by shape, separating out specimens he felt resembled land and sea animals. His work was a first step toward the modern view of fossils as the remains of living creatures.