# Popular Science Monthly/Volume 87/September 1915/Natural Science in the Middle Ages

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* NATURAL SCIENCE IN THE MIDDLE AGES
By Professor LYNN THORNDIKE
WESTERN RESERVE UNIVERSITY
PROBABLY ninety-nine out of every hundred educated persons would be surprised to learn that there was any such thing as natural science in the middle ages. Lest I seem to impute too much ignorance to my present audience, perhaps I should lower the ratio to nine persons out of ten. That is really a flattering estimate, since one of the most recent works on the middle ages, Taylor's "The Medieval Mind," while it devotes two volumes to monasticism, scholasticism and other features of medieval thought, treats of natural science in the middle ages only incidentally in two chapters upon Albertus Magnus and Roger Bacon, and dismisses all other medieval students of nature with the words,
Assuredly, through all the middle ages there were men who noticed such physical phenomena as bore upon their lives, even men who cared for the dumb beginnings of what eventually might lead to natural science. But they were not representative of their epoch's master energies.
Such an attitude is due partly to the fact that the history of science has as yet been little investigated; it is also partly due to misconceptions concerning the middle ages. If we appreciate what the middle ages really were, we shall not be amazed to find an interest in natural science then.
Every one knows that by the term "middle ages" is roughly indicated the period between ancient civilization and modern civilization, or, more specifically, between the. decline of the Roman Empire and the Italian Renaissance or the discovery of America. For a time historians, under the influence either of classical or of Protestant prejudices, seemed to think that between ancient civilization and modern civilization there was no civilization. Therefore, the term "dark ages" was applied to the middle ages. Everything worth while in modern life was supposed either to have been rescued from the ruins of antiquity by the men of the Renaissance, or to have originated at some time since. Every disused and decadent idea or custom which modern men threw away on to the historical ash-heap was designated as medieval.
But after a while the middle ages were studied more thoroughly and sympathetically. Monasticism, feudalism, scholasticism, the social and ​industrial groups of manor and guild, the crusades, the pilgrimages, the friars, the cathedrals, and the great ideals of the church and of chivalry, were recognized as important in human history, though different from the thoughts and doings of men before or since. The expression "medieval civilization" was now introduced alongside of "ancient civilization" and "modern civilization," while the phrase "dark ages" was restricted to the early middle ages while the barbarian invasions were going on. Indeed, a recent writer on the history of education wittily states that successive investigations keep pushing the "dark ages" so much further and further back that they will probably ultimately cover no time whatever.
There was, then, civilization, if not natural science, in the middle ages. But it would be leaving a wrong impression to imply that medieval civilization was something quite distinct from ancient or modern civilization. The fact is, and after all it is just what one would naturally expect, that medieval civilization was in large measure a combination of ancient and modern elements. Much it inherited; much it originated; and much it passed on. Moreover, the middle ages really belong partly to ancient and partly to modern times. This principle is now being largely accepted even in high-school teaching and text-books. The year course in ancient history is carried down to Charlemagne, while medieval and modern history are united as a single year's work. In the museums of Europe, too, no great gap is observed between the middle ages and the renaissance, but objects are usually classified together under one caption as of both those periods.
It is very difficult to separate history into distinct periods, yet there is considerable reason for regarding Charlemagne, towering as he did seven feet tall and fighting a campaign every season for over forty years, as the last great landmark of ancient times. With all his vigor he caused little or no permanent progress. He failed to drive the Mohammedans from Spain; under his successors the Northmen and other invaders broke up his empire. But when the Northmen, after their wonderful expansion in all directions from Greenland to the Mediterranean and from Russia to North America, had settled down in Normandy, England, Sicily and elsewhere; when they had with amazing rapidity adapted and improved upon such civilization as they found still existing in their new homes; when the Arabs had brought from the East to Spain the material civilization of the Orient and the intellectual treasures of the Greek genius; and when the men of the north, either as peaceful traders and pilgrims or warlike crusaders, had visited Spain, Constantinople and the Holy Land; the wheels of progress started moving with a new alacrity and things began to hum. Once again, as had happened before in the Mediterranean Basin, the races of the north descended upon and fused with those of the south, and the east passed on to the west the torch of civilization.
​The results of this contact were felt first in Spain and Italy, but the new civilization became generally manifest throughout western Europe in the twelfth and thirteenth centuries. This is the period of which I shall speak this afternoon, and I shall now remind you of some things in the twelfth and thirteenth centuries that were modern in character, so that you may not be surprised when I suggest that modern science, too, began in the middle ages. A book has been written recently on what we owe to the Greeks; let us see what we owe to the middle ages.
In the first place, the Celtic and Teutonic races and the Roman Catholic church. Those races were absorbed, and were trained and inspired to erect a new civilization. In this work the church, as the greatest social force of the times, played the chief part. It has well been said that the Teutonic vigor and originality, and the spirit of western Christianity were quite as responsible for the Italian Renaissance as was the classical revival. There was no renaissance at Constantinople, though there was plenty of study of Greek there. At Constantinople classical culture remained as it were in cold storage. In Italy there was a fresh living movement. New blood and new ideals were responsible.
Secondly and more specifically, our modern languages and literatures began in the middle ages before the classical revival. Already in the twelfth and thirteenth centuries the languages of modern Europe were taking on literary form, and poets were expressing in their own tongues the spirit of a new age. A specialist in comparative literature assures us that the popular literature of the twelfth and thirteenth centuries resembles eighteenth and nineteenth century literature more than it does that of the ninth and tenth centuries which were so much nearer in mere point of time.
In art we owe to the middle ages the marvelous Gothic style of architecture with its new structural conceptions and infinite resource of adornment.
In politics there began then national states in contrast to the city states and empires of antiquity. Representative government, too, was developed as it had not been in ancient times. Representative institutions were widespread in western Europe at the close of the thirteenth century, and survived in England through succeeding centuries to furnish a model for other nations which reintroduced parliamentary government in the nineteenth century. Bishop Stubbs limited his famous "Constitutional History of England" to the medieval period. During that time the English were busy making their constitution; ever since they have been busy breaking it.
The middle ages recovered from the economic dry-rot which had ruined the Roman empire from within before ever the barbarians broke through its military shell from without. The middle ages revived the ​city life of antiquity, but with these modern differences, that religion was separate from the state, and that the institution of human slavery found no place in the medieval town. There the freeman was not ashamed to toil, and the runaway serf could acquire liberty. Slavery has been reckoned by one historian of science as one of the five great obstacles to the advance of science in antiquity; if so, the middle ages were better off in this respect.
Early in the twelfth century there was a great outburst of enthusiasm for learning and of intellectual curiosity. Students swarmed from all parts of western Europe seeking teachers; the result was that foundation of the European universities whose intellectual life has been continuous from then until now. Roman law was revived and studied scientifically. The fruits of Greek philosophy, preserved by the Arabs in Spain or the Orient in translations and commentaries, were translated again,—this time into Latin, which in the Christian West was now the universal language of scholarship. Humanism, classical scholarship in the strict and narrow sense, and the great paintings and sculptures of the Italians in the fifteenth and early sixteenth centuries, were but later phases of the same movement. Petrarch, the first great humanist, who adored Cicero, wrote letters like Pliny the Younger, collected and copied ancient manuscripts, and came to scorn all contemporary interests except his own fame, has often been called the first modern man, but in many ways seems a reactionary looking backward. Abelard, the first great schoolman, who over two centuries before Petrarch's time wandered forth from his native Brittany, first seeking teachers, then triumphing over them, then attracting students to himself; Abelard, who dared to show that even the church fathers held conflicting opinions, and who advocated sceptical and systematic criticism as the best road to knowledge; Abelard, more than Petrarch, deserves the title of the first modern man.
Turning now from medieval civilization as a whole to this medieval learning in particular, let us correct some erroneous notions concerning it. For one thing, we have been taught to call medieval learning scholasticism, and to think of it as concerned almost exclusively with logic, metaphysics and theology; while we have been taught to associate the beginnings of modern science with the Italian Renaissance. But the fact is that the narrow humanist of the Renaissance took no more interest in natural science than did the narrow schoolman of the middle ages. The sciences which they cultivated were philology and theology. The fact is that natural science has had a more or less continuous development of its own, largely independent of the middle ages and Renaissance. Books on nature written in the twelfth and thirteenth centuries were still satisfactory to readers in the fifteenth and sixteenth centuries, as is shown by numerous editions of them which were printed then.
The reliance of the middle ages upon the authority of the Greek ​philosopher Aristotle has often been exaggerated. In medicine they recognized Galen as a greater authority than Aristotle. In astronomy Ptolemy was their guide. In natural history they cited Pliny the Elder. Indeed they used scores of other authorities than Aristotle. But had he been their sole source of information, they would not have been without interest in natural science, for Aristotle devotes much attention to that field. He wrote not only on logic, ethics and metaphysics; but on physics, animals, plants, minerals, the heavens, sleep and waking, generation and corruption, and so forth. Indeed, he was without much doubt the greatest scientist of antiquity.
Now the twelfth century had known only Aristotle's "Logic." When his other works were brought from Spain and translated from Arabic into Latin in the early thirteenth century, those devoted to nature created even more of a furore than the others. The great University of Paris at first prohibited these newly discovered books in natural philosophy. But it was impossible to check the rising tide of secular and scientific learning. Another French university at Toulouse advertised its readiness to teach these works of Aristotle on nature, and before long the forbidden books were being freely taught at Paris itself.
Paris's two leading theologians and commentators on Aristotle were also recognized in their own day as great students of nature. Albertus Magnus wrote on all the subjects that Aristotle had treated and added much new information in his works on plants and animals. Thomas Aquinas is usually thought of as a theologian; but when he died, the University of Paris wrote to the Dominicans asking that his bones might be sent to Paris for burial, and also requesting the transmission of some books begun by him while at the university but not as yet completed upon his departure from Paris. What were these writings; theological treatises, commentaries on the minor prophets, or manuals of devotion? None of these. They were a commentary on the philosopher Simplicius; another on Aristotle's treatise "The Sky and Universe"; a third on Plato's "Timæus," a dialogue dealing with nature; and finally, a treatise on irrigation and mechanical engineering.
Another erroneous notion concerning the middle ages is that nature was studied chiefly in order to illustrate spiritual truth or to teach moral lessons. The "Bestiary," a little manual about animals used by the clergy for illustrations in their sermons, is often referred to as typical of medieval science; but one might as well judge modern science by the lurid articles in the supplements of our Sunday newspapers. Far more typical are the long encyclopedias in Latin prose which collected all available information concerning the phenomena of nature, and whose motive was rather a keen curiosity about the things of this world than a desire merely to illustrate divine verities. It is true that one of the earliest and briefest of these encyclopedists, Alexander Neckam, an ​English monk, still tends to moralize and allegorize. For instance, he says that some persons call the spots on the moon caverns or mountains, but that he believes that they were put there to signify the stain of sin which Adam's transgression brought into the world. But Neckam also displays a scientific attitude. When he finds a statement in the book of Genesis in apparent contradiction to the astronomy of his time, he explains that the Bible here follows "the judgment of the eye and the popular notion," but that astronomy is really right. The later and longer encyclopedias of Arnold of Saxony, Thomas of Cantimprè, Bartholomew of England, and Vincent of Beauvais greatly increased the amount of space devoted to nature and contained comparatively little moralizing.
I may explain that in a medieval encyclopedia, instead of the alphabetical arrangement followed in modern encyclopedias, there is first a topical arrangement under such heads as Reptiles or Birds or Trees, and then an alphabetical arrangement under each topic. As in modern encyclopedias, most of the information was taken from other books, but sometimes the medieval encyclopedist adds new data which he has heard from hunters, travelers and others, or which he has learned from personal observation.
The twelfth and thirteenth centuries were a period of intellectual curiosity. Albertus Magnus says that he lists the properties of individual plants in order to satisfy the curiosity of his students. A favorite book of the period, translated into almost every European language, was entitled, "De omni re scibili et quibusdam aliis" which may be freely translated as "Concerning everything that can be known and then some." Indeed, it is not merely in professedly learned works written in Latin that one sees the interest of those times in natural science. If we turn to popular literature in the tongue of the layman and open one of the long French romances of the thirteenth century, we find Dame Nature making a speech concerning various branches of natural science which occupies a considerable section of the entire poem, whereas little space is devoted to logic or theology.
This interest in nature is often accompanied by an independent scientific spirit, of which we have just seen some evidence even in the moralizing Neckam. But it can be traced back earlier than him to the beginning of the twelfth century. As the life story and writings of Abelard illustrate the great interest in logic, philosophy and theology at the beginning of the twelfth century, and help to explain the origin of the University of Paris; so the career and books of a contemporary of his with a very similar name, Adelard of Bath, depict a pioneer of natural science. As Abelard went forth from Brittany through the towns of France in quest of Christian teachers, so from England Adelard made a wider circuit in lands both Christian and Mohammedan, where he might acquaint himself with all that was best in contemporary learning, but especially in mathematics and natural science.
​In one of his works he tells us that upon his recent return to England after long study abroad, his nephew and other friends urged him to disclose some of the new ideas that he had learned among the Arabs. The result is his treatise called "Natural Questions" in the form of a dialogue with his nephew, who proposes, by means of a set of questions, to force his uncle Adelard to justify his preference for "the opinions of the Saracens" concerning nature over those of "the schools of Gaul" where the nephew has been studying. Adelard agrees to this, but wishes to state at the start that, because of the prejudice of the present generation against any modern discoveries, he will attribute even his own ideas to the Arabs and will not be personally responsible for what he says. "For I know," he declares, "what misfortunes pursue the professors of truth among the common crowd. Therefore it is the cause of the Arabs that I plead, not my own."
Adelard's use of the word "modern" should be noted. The word modernus is not found in classical Latin, but is often employed in the twelfth and thirteenth centuries. In another passage Adelard distinguishes "the writings of men of old" from "the science of moderns." Bartholomew of England rejects an astronomical theory of the Venerable Bede, and says that he prefers the view of "modern writers who, as I think, have scrutinized the subtler signs of philosophy more profoundly." Peter of Spain, who finally became Pope John XXI., in one of his medical treatises states his sources of information as "ancient philosophers" and "modern experimenters." Several other writers use like expressions. So perhaps Adelard rather than either Petrarch or Abelard should be called the first modern man.
The opening question asked of Adelard by his nephew is, "How can plants grow from earth which they so little resemble?" The nephew fails to see how this can be explained except as "a marvelous effect of the marvelous divine will." Adelard retorts that no doubt it is the Creator's will, but that the operation is also not without a natural reason. This gives a fair example of the tone of the dialogue throughout; Adelard upholds scientific argument and investigation against a narrow religious attitude. He insists that he is in no way detracting from God, whom he grants to be the source of all things, but that nature "is not confused and without system," and that "human science should be given a hearing on those points which it has covered." He also sets reason above authority; and sharply reprimands his nephew for following authority as if he were a brute led by a halter, for his bestial credulity, for his trusting simply in the mention of an old title. In fine, he tells his nephew that if their discussion is to go any further, he must drop authorities and "give and take reason." He assures his young relation that he is not the sort of a man "who can be fed on the picture of a beefsteak."
​It is true that both questions and answers in this pioneer book of natural science are usually more amusing than instructive to the modern reader, although Adelard in his prologue says that he is sure his treatise will be useful to his hearers, but not that it will prove entertaining (tractatum. . . quem quidem auditoribus suis utilem fore scio, iocundum nescio). Asked why men do not have horns, Adelard first objects that the question is trivial; but when the nephew urges the utility of horns as weapons of defense, Adelard replies that man has reason instead of horns, and that, as a social as well as bellicose animal, he requires arms which he can lay aside in time of peace. Asked why the nose is placed above the mouth, he replies that it serves the head while the mouth serves the stomach. Many of his explanations are grounded upon the hypothesis current since the Greek philosopher Empedocles, that all nature is composed of four elements, earth, air, fire and water, and characterized by four qualities, hot, cold, dry and moist. Thus when Adelard is asked why bright students often have poor memories, he answers that a moist brain is conducive to intelligence, and a dry cerebrum to memory. He explains his nephew's weeping for joy to see his uncle safely returned from the Orient by the theory that his excessive delight heated his brain and distilled moisture thence.
But reasoning from a general theory of nature to explain particular phenomena is not Adelard's sole method; he also relies on experience. Nor are all his notions crude and incorrect. While he accepts the long established theory of four elements, he is careful to explain that the earth which we see and call by that name is not the element earth, and that no one has ever touched the element water, or seen the elements fire and air. Every particular object contains all four elements, and in daily life we deal only with compounds.
Adelard states the eternity of matter as follows:
And certainly in my judgment nothing in this sensible world ever perishes or is less to-day than when it was created. If a part is dissolved from one union, it does not perish but is joined to some other group.
When his nephew asks him to explain the working of a magic water jar which they once saw at an enchantress's house, and which had holes in both top and bottom so that the attendant could check the flow of water from the bottom by placing his fingers over the apertures in the top, Adelard accounts for the trick by saying that nature abhors a vacuum. Asked how far a stone would fall, if it were dropped into a hole which extended through the center of the earth, he states that it would fall as far as the center and stop there.
We have heard Adelard upholding scientific argument and investigation against a narrow religious attitude. This position is further illustrated by a contemporary of his, William of Conches in Normandy. William, too, complains that the age is instinctively hostile to new ​ideas; and dilates upon the unreasonableness of those persons who are unwilling to listen to explanations of the natural phenomena mentioned in the Scriptures, but prefer to accept them blindly. He declares that since they themselves know nothing of the forces of nature, they are unwilling that any one else should investigate these. "We, on the contrary," he says, "think that a reason should be sought in every case, if one can be found." In another passage William's indignation is aroused by those who say, "We don't know how this is, but we know that God can do it." "You poor fools," he retorts, "God can make a cow out of a tree but has he ever done so?"
This theological opposition, of which Adelard and William are conscious, brings before us the important problem of the attitude of the medieval church to science. There is not time to-day to argue it at length; I can only give you my conclusions. We see science establishing its own standpoint and marking out the boundaries of its realm. The first surveyors, like Adelard and William, naturally meet with opposition and encounter a jealous attitude which fears lest study of science and nature will be at the expense of religion and God. But in the end it turns out that so long as they do not trespass upon the particular preserves of theology their stakes are not pulled up. In the course of two centuries the church gradually gets used to science, just as the University of Paris finally accepts the new Aristotle. By the middle of the thirteenth century Thomas Aquinas, from whom we expect an authoritative presentation of the position of the church, holds that to a large extent the fields of theology and natural science are distinct; that theologians should not try to settle purely philosophical or scientific problems, and, conversely, that every theory of ancient philosophy or scientific hypothesis is not to be regarded as a religious dogma.
Men of science, who were often clergymen themselves, seldom attacked Christianity in the middle ages, and as a rule maintain the usual medieval tone of respectful and devout feeling toward theology and religion. Conversely, there seems no adequate proof for a single specific instance of persecution of men of science by the church for purely scientific views in the twelfth and thirteenth centuries. The occasions when such men got into trouble and when we know the reason why, are just those occasions when they left science to dabble in theological or ecclesiastical concerns. Roger Bacon has often been pictured as a long-suffering martyr to the cause of science, but this is a legend constructed from historians' imaginations and added to by successive writers; the sources indicate that he was imprisoned only once, and then we do not know for how long nor whether his scientific work had anything to do with it. On the other hand, many cases might be mentioned where popes and prelates patronized and protected medieval men of science, while Peter of Spain became pope himself.
​It can not be shown then that there was bitter warfare between science and theology in the middle ages; nor, on the other hand, was science a handmaid at theology's beck and call. The two interests were beginning to separate, sometimes with a little friction, often with much caution on the part of science, yet on the whole with maintenance of friendly relations between them. Science was still somewhat under the wing of the church, but science was learning to use its own wings.
Having traced back the scientific spirit in western Christian Europe to the twelfth and thirteenth centuries rather than to the time of the Italian Renaissance, let us now examine some of the particular fields which it investigated.
Physics was studied now, and not merely along the theoretical lines of Aristotle's treatise. Further progress had been made among the Arabs in optics; and the subjects of vision, perspective, reflection and refraction were now better understood than in the time of Ptolemy. The men of the thirteenth century speedily absorbed these new ideas of the Arabs. Roger Bacon, it is true, while according due credit to the Arabs, gives us the impression that his Latin contemporaries were neglecting the subject of optics, and describes the formation of rainbows, and the characteristics of convex and concave mirrors, burning glasses and lenses by which the size of objects can be greatly magnified, or mirrors by which their numbers can be greatly multiplied, as if all these things were marvelous novelties. Bacon's own discussion of these matters is excellent, and in some details he corrects or adds to his Arabian authorities, but he does not do justice to his Christian contemporaries. At just about this time Witelo, a Pole who traveled in Italy, wrote an important treatise on optics in which he embodied the views of Alhazen, the leading Arabian authority, together with many additions from other writers and of his own. Moreover, the French "Romance of the Rose," probably written soon after Bacon's work, shows remarkable familiarity with all the things that he describes. Of rainbows it remarks that
Only he who's learned the rule
Of optics in some famous school
Can to his fellow men explain
How 'tis that from the sun they gain
Their glorious hues.
The author also mentions burning-glasses and various other sorts of mirrors, but he refers to all these as well-known scientific facts, and says that there are plenty of books about them. He also unmistakably describes magnifyng glasses when he tells us that from optics one
... may learn the cause
Why mirrors, through some subtle laws
Have power to objects seen therein
(Atoms minute or letters thin)
To give appearance of fair size,
Though naked unassisted eyes Can scarce perceive them. Grains of sand Seem stones when through these glasses scanned.
The poet goes on to say that through these glasses one can read letters from such a distance that one would not believe it unless he had seen it. Then he concludes,
But to these matters blind affiance No man need give; they're proved by science.
From the testimony of several other contemporaries we know that eye-glasses had been invented before the close of the thirteenth century.
Another important physical treatise besides Witelo's was a "Book on Weights" by Jordanus Nemorarius earlier in the century. In this work he is said to have made progress in dynamics beyond the ancients. Another invention of great use to science, clocks, was worked out during the middle ages. An innovation of great convenience in scientific reckoning and records was made when Leonardo, a merchant of Pisa, in a work written first in 1202 and then revised in 1228, brought the so-called Arabic numerals to the attention of Western Europe. Some progress in algebra was also made in the middle ages, and Roger Bacon emphasized the importance of mathematical method in scientific investigation.
It can not be shown that Roger Bacon actually anticipated any of our modern inventions, but the following passage from one of his works does indicate that an interest existed then in machinery and mechanical devices, and that men were already beginning to struggle with the problems which have recently been solved.
Machines for navigation can be made without rowers so that the largest ships on rivers or seas will be moved by a single man in charge with greater velocity than if they were full of men. Also cars can be made so that without animals they will move with unbelievable rapidity; such we opine were the scythe-bearing chariots with which the men of old fought. Also flying machines can be constructed so that a man sits in the midst of the machine revolving some engine by which artificial wings are made to beat the air like a flying bird. Also a machine small in size for raising or lowering enormous weights, than which nothing is more useful in emergencies. For by a machine three fingers high and wide and of less size a man could free himself and his friends from all danger of prison and rise and descend. Also a machine can easily be made by which one man can draw a thousand to himself by violence against their wills, and attract other things in like manner. Also machines can be made for walking in the sea and rivers, even to the bottom without danger. For Alexander the Great employed such, that he might see the secrets of the deep, as Ethicus the astronomer tells. These machines were made in antiquity and they have certainly been made in our times, except possibly a flying machine which I have not seen nor do I know any one who has, but I know an expert who has thought out the way to make one. And such things can be made almost without limit, for instance, bridges across rivers without piers or other supports, and mechanisms, and unheard of engines.
​Since Bacon's authority concerning Alexander is unreliable and his conjecture concerning ancient scythe-bearing chariots unwarranted, we may also doubt if steamboats and automobiles had "certainly been made" in his day; but there seems little doubt that men were trying to accomplish such things.
The modern science of geology was a sealed book both to the middle ages and to antiquity. But in geography the middle ages seem to have preserved the knowledge of the ancients and to have added considerably thereto. The north of Europe and its adjacent seas now became better known. In the thirteenth century medieval missionaries and travelers penetrated to the far East, and the accounts of the Venetian trader, Marco Polo, and of the Franciscan friar, William of Kubruk, gave information concerning China and Japan,—lands practically unknown to the men of classical times. The mariner's compass must have been known in western Europe by the twelfth century; it is first mentioned by Alexander Neckam, the same man who thought that Adam's fall caused the spots on the moon. It very possibly was a western invention, since it can hardly be proved that it was known before this in the Orient, where some think that it was first introduced by the Portuguese. After Neckam the compass is frequently referred to by western writers and was evidently in common use. The old story that sailors were long afraid to use the new instrument lest they be accused of magic seems to be an arrant fabrication with no foundation in the writings of the time, which speak of the invention in a tone of perfect freedom and unconcern. In the fourteenth century came the development of deep sea sailing and Atlantic navigation; and the Portuguese by 1350 had discovered the Canary, Madeira and Azores Islands. The Italian sailors became so expert in charting coasts that Professor Beazley affirms that a certain fourteenth-century map of the Mediterranean is superior to any other until as late as the eighteenth century. Thus in the middle ages the foundations were laid for the circumnavigation of Africa and discovery of America in the last decade of the fifteenth century. Already in Dante's time every well-educated person knew that the world was round and that the people on the other side could not possibly fall off; and any one who read Pliny and Seneca, as every medieval student of nature did, could read, as Roger Bacon did, that the space dividing the west of Spain from the east of India was not great. Other authorities, however, made the distance much greater.
Alchemy, the art which strove to convert metals of less value into gold, is usually associated especially with the middle ages, and regarded as a proof of their superstition compared to the scientific perfection of modern chemistry. We must make several amendments to this view. First, alchemy is in no sense peculiarly medieval but existed in the ancient Greek-speaking world and perhaps came down from ancient Egypt. ​Berthelot found 160 tracts by Greek alchemists. Also, various distinguished scientists continued to believe in the transmutation of metals as late as the seventeenth century. Second, thirteenth century alchemy was less superstitious and more scientific than in previous periods, whether among the Greeks or more recently among the Arabs. This fact has been rather obscured because the editors and publishers of books on alchemy in the sixteenth century preferred to print such treatises as made great pretensions and were full of mystic language. Thus the productions of charlatans got into print and the more sober works of rational investigators remained for the most part neglected in manuscripts. These, however, have now been studied by Berthelot with the following results.
Whereas Greek tracts on alchemy are all in an archaic enigmatic style, "combining in one undecipherable medley terms of obscure meaning, magical formulas, astrological notions, citations from mystic authors, and cryptic allusions to a philosophy long since buried too deep for present resurrection"; on the contrary, the thirteenth century treatises are full of positive details and rational argument. Moreover, the medieval alchemists are careful to refute those who deny the possibility of transmuting metals, while it does not seem to have entered the heads of the Greek alchemists that any one should doubt the truth of their art. Third, this progress is not due to the Arabs. Berthelot discovered only one treatise in Arabic which contained precise and minute details about chemical substances and operations. As a rule the Arabian alchemists wrote "theoretical works full of allegories and declamations." For a long time several works important in the history of chemistry as well as of alchemy were regarded as Latin translations from the Arab Geber, who was consequently regarded as a pioneer in the history of science. Berthelot discovered the Arabic manuscripts which turned out to be of little value and largely copied from Greek sources. On the other hand, the Latin works which had gone under Geber's name were produced in the thirteenth and fourteenth centuries by men who seem, like Adelard of Bath, to have preferred to attribute their own ideas to the Arabs.
Let us examine for a moment with Berthelot the chief of these treatises. It is "a systematic work, very well arranged." "Its modest method of exposition" differs greatly from "the excessive and vague promises of the real Geber." It refutes scepticism as to alchemy in a long scholastic discussion typical of the thirteenth century. But this is no mere scholastic treatise. Parts of it possess "a truly scientific character" and show "the state of chemical knowledge and theory with a precision of thought and expression unknown to previous authors." The writer "defines carefully silver, lead and the other metals, and traces the characteristic features of their chemical history as far as it was then known. If you leave out a few incorrect details connected with ​transmutation, all these chapters show the stamp of solid science." Elsewhere the writer describes chemical operations, and "each description is full of special details and illustrated in the manuscript by exact figures."
Roger Bacon, too, shows us that alchemy was not intent merely upon transmutation, when he defines it as the science "concerning the generation of things from the elements, and concerning all inanimate things, such as the elements and humors single and compound, ordinary stones, gems, marbles, gold and other metals, sulphurs, salts, dyes and colors, oils, bitumen and countless other things." The invention of gunpowder has sometimes been attributed to Bacon, probably incorrectly; but he mentions some explosive as already in common use in children's toy caps and torpedoes.
We have already seen that there was a good deal of scepticism about the transmutation of metals in the thirteenth century. The consensus of learned opinion was that most alchemists produced a mere appearance of gold which would not stand severe tests. However, it was believed that by reducing the metals to their constituent elements or to first matter one might then combine them anew into gold. The difficulty, of course, was in not realizing that the metals themselves were elements.
Astrology was another medieval study which, like alchemy, was partly scientific and partly superstitious. No clear distinction in meaning was observed between the words astronomy and astrology. Either one was used to include both knowledge of the movements of the heavenly bodies and prediction of the future from them. Indeed, it was largely due to this sensational and superstitious side of the subject that sober astronomical observations made so much progress in both antiquity and the middle ages. Astronomy in those days was the most advanced of any natural science, although the Copernican theory and the telescope were as yet in the future. Astronomy was classed as the chief of the liberal arts; numerous treatises concerning the heavens were composed; Ptolemy's out-of-date astronomical tables were replaced by those of King Alfonso the Wise of Spain; Roger Bacon pointed out the need of reforming the calendar which Pope Gregory accomplished centuries later; in 1344 an archbishop of Canterbury was the first to expound the correct theory of polygonal stars.
Moreover, astrology, like alchemy, became more scientific in the thirteenth century than before, and it supplied what may almost be called the fundamental scientific hypothesis of that period. The middle ages no longer regarded the planets as gods; and they did not so much emphasize the notion that the fate of this or that man can be predicted from the constellations, as they did insist that the whole world of nature on our globe was controlled by the orderly, unceasing and unchanging revolutions of the heavenly bodies. All generation and corruption in ​organic life was supposed to be so controlled, and even inorganic matter was thought to receive impressions from the stars. Even the members of the human body were parceled out under the control of the different planets and signs of the zodiac. How far one thought human fate under the stars simply depended on how far one attributed human action to appetite and environment, rather than to reason, will and divine interference. In any case, astronomy and astrology must be reckoned with in botany, zoology, mineralogy and medicine; and became the supreme science, the one underlying the rest.
Furthermore, astrology was no easy art, but had a very complicated technique as well as an enormous scope. The pursuit of this intricate superstition must, like the disputations and carefully analyzed arguments of the scholastics, have exercised a beneficial effect upon the muscles of the human mind. It has always been a matter of some wonder to me that, even after astrology was proved to be false, its former devotees did not continue to urge the study of this outworn subject on the ground that it would provide good mental discipline.
Medieval medicine was connected with natural science, and sometimes with astrology; but there is not time to speak of it now except to say that there were several schools or university faculties of medicine, that numerous medical treatises have come down to us, and that, while in the main medicine was still controlled by the theories and authority of Galen, there seems to have been some progress. Surgery received a new impulse in Italy in the thirteenth century, though the epoch-making discoveries of Vesalius and Harvey were still far in the future.
We have seen that Aristotle was not the sole authority of medieval science; I wish now to emphasize that it did not rely solely upon authorities, no matter how numerous. We have already heard Adelard prefer reason to mere authority, but besides reason medieval students of nature recognized observation and experience as criteria of truth. Albertus Magnus, for instance, in the later books of his work on animals, often says, "I have tested this," or "My associates and I have experienced this," or "I have proved this is not so," or "But I have not experienced that." When discussing whales, he "passes over the writings of antiquity on this topic because they do not agree with experience," and gives his own personal observations instead. Often, indeed, he questions the reliability of former writers, drawing a sharp line between those who state what they themselves have seen or experienced and those who appear to repeat rumor or folk-lore. He will not accept everything that Pliny the Elder says in his "Natural History," and he is particularly chary of accepting the assertions of Solinus and Jorach, assuring his readers that
those philosophers tell many lies and I think that this is one of their lies.
In his treatise on plants, too, which has been called the chief work ​in botany between Theophrastus and Gesner, Albert limits himself to "those plants better known among us." Of some of these he has personal knowledge, for others he cites those writers
who are not too ready to state anything unless it is proved by experience. For in such matters experience alone gives sure information.
Again in his "Physics" Albert states that
Indeed, medieval men not merely trusted in observation and experience; they experimented. The inventions which we have mentioned involved experimentation. The efforts of the alchemists involved experimentation. We have heard Peter of Spain contrast "ancient philosophers" with "modern experimenters." Roger Bacon has been given undue credit for his discussion of "experimental science," and has been lauded as the first prophet of modern science in the wilderness of scholasticism. But his views seem to have really been the common property of his age, as I have shown more fully in an article upon "Roger Bacon and Experimental Method in the Middle Ages," which appeared in The Philosophical Review (May, 1914).
So far we have considered the serious side of medieval science and the progress which was then being made, slight indeed compared with the rapid strides of science in our own time, but well worth the notice of any one interested in science's first steps. But it would be unfair to stop there; if we disclose medieval science's merits, we must also draw forth its frailties and lay bare the superstition, the absurdities, the credulity which characterized the study of nature then. Fortunately this side of medieval science is as amusing as the other was serious.
The credulity of medieval men is something astounding. Roger Bacon and Albertus Magnus are both sceptical at times. Then again they simply amaze one by their incomprehensible gullibility. For instance, Bacon classifies the prophetic writings of Merlin among "reliable authorities"; he tells of a woman of Norwich who lived without food for twenty years, "as the bishop proved by a trustworthy examination"; he says that "papal letters attest" that a German captured by the Saracens received a medicine which prolonged his life to 500 years. He has "learned without deceit or doubt from men of proved faith" that "good flying dragons" still exist in Christian Europe, and that eating their flesh will prolong life and develop the mind to a high degree. Moreover, some of these assertions occur in the very midst of his discussion of experimental science. Albert is somewhat less credulous on the theme of dragons and suggests that meteors or flaming vapors may have been mistaken for flying dragons breathing fire. But Albert falls a victim to a sea-serpent yarn, having "heard from trustworthy ​persons" that a serpent with the virgin countenance of a beardless man was recently killed in an island of Germany. Another "trustworthy person" told him that he saw in an eagle's nest 500 ducks, over 100 geese, about 40 hares, and many large fish, which were all required to satisfy the hunger of the young eaglets.
Besides miscellaneous instances of credulity, and the errors of alchemy and astrology already mentioned, we find medieval books on nature full of marvelous and fantastic properties attributed to plants, stones, birds and beasts. Especially wonderful powers are attributed to gems. A French Bishop Marbod in his book on stones tells us that the sapphire nourishes the body and preserves the limbs intact. One who carries it can not be injured by fraud or envy, and is impervious to fear. It sets prisoners free; and is even represented as placating God and rendering him favorable to prayers. It makes peace between foes. By means of it the future can be predicted. It cools one off and checks perspiration. Applied in a pulverized state with milk, it heals ulcers, cleans the eyes, cures headache and ills of the tongue.
But plants, too, as well as gems, have remarkable powers. The German abbess Hildegard, in her work on "The Subtleties of Diverse Creatures," mentions certain plants which fish eat, and which, if a man could procure and eat, would enable him to go without food for four or five months. Adam used to eat them now and then, after he had been cast out of Eden, but not when he could get other food, since they make one's flesh tough. As for the strange virtues possessed by birds, Hildegard tells us that mistiness is marvelously removed from the eyes by catching a nightingale before daybreak, adding a single drop of dew found on clean grass to the bird's gall; and anointing the eyebrows and lashes frequently with the mixture.
Hildegard's chapters on quadrupeds are delightfully quaint. The camel is peculiar in that its different humps possess different virtues. The hump next its neck has the virtues of the lion, the second of the leopard, the third of the horse. Unicorns can never be caught except by means of girls, for they flee from men, but stop to gase diligently at girls, because they marvel that they have human forms, yet no beards. "And," adds Hildegard,
if there are two or three girls together, the unicorn marvels so much the more and is the more easily captured while its eyes are fixed upon them.
When a weasel is sick, another weasel digs up a certain herb and breathes on it for the space of an hour and then brings it to the sick weasel who is cured thereby. This herb is unknown to other animals and to men, and it would do them no good if they did know of it, since its own virtue is not efficacious, nor would their breathing upon it make it so. But the heart of a weasel, dried and placed with wax in the ear, benefits deafness or headache. A fine cure for epilepsy is to ​put a mouse in a dish of water and then give this water to the patient to drink, not to mention washing his forehead and feet in it. As with drinking Postum instead of coffee, "There is a reason." It is this,
Inasmuch as the mouse runs away from everything, therefore it drives away the falling disease.
Marbod and Hildegard were twelfth-century writers, and somewhat naïve and undiscriminating in their acceptance of marvels. The thirteenth-century encyclopedias and works on medicine do not contain so much chaff in proportion to their wheat; but they still contain a great deal. Even Roger Bacon, who declared false and disproved by experiment several such notions as that only goat's blood can break adamant and that hot water freezes faster than cold,—even Bacon still speaks of the "almost miraculous" powers of "herbs and stones and metals." However, the writers come to recognize that there is something peculiar and requiring explanation in these strange properties ascribed to the things of nature. In the thirteenth century they are distinguished as occult virtues and are regarded as marvelous. It is admitted that reason can not account for them, but their existence is declared to be attested by experience.
Thus Albertus Magnus admits that it is difficult to explain the strange virtues of gems, and says that many students of nature seem to doubt whether stones possess any such attributes as to cure ulcers, counteract magic potions, conciliate human hearts, and win battles. But he insists that these occult virtues are well-established facts, and gives two examples attested by his own experience, namely, the magnet's power to attract iron and a sapphire which he saw cure ulcers. Some plants, too, Albert declares, have "divine effects which students of magic especially investigate."
On the other hand, Vincent of Beauvais, while he still agrees with Marbod that the virtues of gems are so marvellous that they can be accounted for only as the result of direct divine influence, thinks that plants possess only natural powers, which are chiefly medicinal. Nor does either Albert or Vincent usually recommend fantastic or irrelevant methods of using herbs medicinally. Many, however, of the medicinal virtues which they ascribe to plants are probably false, and they also show a tendency to make each plant a panacea for a long list of very miscellaneous and unrelated diseases. This may be illustrated by a passage taken quite at random and which happens to be about the nasturtium:
and so forth.
To animals amusing habits and human characteristics as well as occult virtues were sometimes ascribed by the encyclopedists. Thus in describing the lion Albert devotes half his space to the noble and genial personality of the king of beasts, and to discrediting scientific scandal about the wiles of the lioness to conceal her amours with the leopard. Then we come to marvelous virtues. A man anointed with lion's fat puts every animal to flight. A diet of lion's flesh is good for paralytics. Garments wrapped in a lion's skin are secure from moths. If the skin of a wolf is left near the skin of a lion, the hair soon falls out from the wolf-skin. The tooth of a lion, suspended around a boy's neck before he loses his first teeth, protects him from toothache when the second teeth appear. Lion's fat should be used in unguents to remove blotches from the skin. Cancer may be cured by an application of lion's blood. Drinking some of a lion's gall cures jaundice. Eating its brain is a cure for madness.
If the encyclopedists attribute marvelous medicinal virtues to individual things, the medical treatises proper prefer elaborate concoctions. Sometimes the ingredients of these formidable mixtures might excite no surprise if administered separately, but the multiplicity and diversity of their combination seems strange indeed. Sometimes the recipes are utterly fantastic. Bernard Gordon assures us that for cure of eye-troubles "God even to these times has never vouchsafed to reveal a better remedy" than a combination in varying amounts of mountain willow, majoram, eufragia, celidonia, fennel, ginger, spikenard, pepper, gariofil, thucia, Persian gum, ass's milk, aloes wood, the gall of an eagle, a hawk and a mountain goat, balsam and honey. Of these ingredients
those that need pulverizing are to be pulverized; those that ought to be shaken well are to be well shaken; those that should be reduced to liquid form are to be liquefied. Then, if it is summer time, they should for forty days be mixed in the hot sun, and stirred daily. And if it be winter, let the mixture be prepared with cinders, where the heat is about that of a sitting hen; and let it be stirred and kept in a glass vessel, and dropped into the eyes; and it is of so great virtue that it enables decrepitude to read small letters without eye-glasses.
Thus in the midst of a superstitious recipe we get evidence of a scientific invention.
Even the experiments of medieval men were affected by this belief in occult virtues, and sometimes resembled the tricks of magic more than the scientific procedure of a modern laboratory. Roger Bacon advocates experimental science at considerable length, but he calls the following an experiment.
A sage at Paris recently cut a snake into small sections except that the skin of its belly on which it crawled was left intact; and that snake crawled as best it could to a certain herb, by touching which it was instantly made whole. Thus the performer of the experiment discovered an herb of wonderful virtue.
But Albertus Magnus has an experiment to match this. He says:
An emerald was recently seen among us, small indeed in size but marvelously beautiful. When its power was to be tested, some one suggested that if a circle was made about the toad with the emerald and then the stone was displayed to the toad, one of two things would happen. Either the stone would be broken by the gaze of the toad, if the stone was of weak virtue; or the toad would burst, if the gem was in its full natural vigor. Things were immediately arranged as suggested, and, after a moderate interval of time, during which the toad kept its eye unswervingly upon the gem, the latter began to crack like a nut and a portion of it flew from the ring. Then the toad, which hitherto had stood immovable, began to move away, as if it had just been freed from the power of the stone.
While medieval men still accept in large measure these far-fetched virtues, they have a semi-scientific theory to account for them. It is not a case of unreasoning superstition. They agree that no satisfactory physical explanation of such virtues can be given, that the varying composition of objects from the four elements is not enough to account for such powers. Vincent thinks them due to divine influence, Hildegard sometimes connects them with demons; but other writers, as Roger Bacon, Peter of Abano, and Thomas Aquinas, attribute them to the influences impressed on matter by the stars. Here again we see how important a part astrology played in medieval science.
We, however, can find an explanation which will explain both the belief in occult virtues and the belief in astrology. They are survivals from magic. The conception of occult virtues in particular objects is magical. Much sympathetic magic, too, may be found stranded on the shores of medieval science, as is seen in the reasoning why the mouse cures epilepsy, and in the eating of lion's flesh in order to grow strong. Furthermore, incantations, amulets, characters, astrological images, are occasionally found in medieval science and medicine. Sometimes their experiments seem like feats of magic.
The reason for this is that science and magic were for a long time closely connected. As anthropologists have shown, magic plays a great part in the life and thought of primitive peoples, and it is only gradually that the science and religion of civilized peoples free themselves from the old habits and instincts. True, it is one of the glories of modern science that it has freed men from superstition and mental anarchy. But science did not come down from above nor invade from without. It grew up in the very midst of superstition and mental anarchy, just as the states of modern Europe had their beginnings in feudal society. As the kings in the middle ages had to govern under feudal limitations and even by feudal means, so science for a long time ​not merely was opposed by the unscientific attitude, but was itself tinged by fantastic theories and false data. Yet the scientific attitude, like the spirit of nationality, was at work in the seeming chaos; gradually it shook itself free from error, and, by the increasing application of truly scientific methods, won a similar triumph to that which the sovereign political power gained by its gradual development of governmental institutions.
This was the process going on in the twelfth and thirteenth centuries. When men still believed in demons and witches and divination from dreams, it is not surprising that they believed also in natural magic. Only a small part of nature's secrets were revealed to them; of the rest they felt that almost anything might turn out to be true. It was a time when "one vast realm of wonder spreads around." They had to struggle against a huge burden of error and superstition which Greece and Rome and the Arabs handed down to them; yet they must try to assimilate what was of value in Aristotle, Galen, Pliny, Ptolemy, and the rest. Crude naïve beginners they were in many respects. Yet they show an interest in nature and its problems; they are drawing the line between science and religion; they make some progress in mathematics, geography, physics and chemistry; they not only talk about experimental method, they actually make some inventions and discoveries of use in the future advance of science. Moreover, they themselves feel that they are making progress. They do not hesitate to disagree with their ancient authorities, when they know something better. Roger Bacon affirms that many scientific facts and truths are known in his time of which Plato and Aristotle, Hippocrates and Galen, were ignorant. The ancients, says Peter of Spain in effect, were philosophers, but we are experimenters. Magic still lingers but the march of modern science has begun.