Читать книгу An Introduction to the History of Science - Walter Libby - Страница 16

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Learning has very often and very aptly been compared to a torch passed from hand to hand. By the written sign or spoken word it is transmitted from one person to another. Very little advance in culture could be made even by the greatest man of genius if he were dependent, for what knowledge he might acquire, merely on his own personal observation. Indeed, it might be said that exceptional mental ability involves a power to absorb the ideas of others, and even that the most original people are those who are able to borrow the most freely.

In recalling the lives of certain great men we may at first be inclined to doubt this truth. How shall we account for the part played in the progress of civilization by the rustic Burns, the village-bred Shakespeare, or by Lincoln the frontiersman? When, however, we scrutinize the case of any one of these, we discover, of course, exceptional natural endowment, susceptibility to mental influence, remarkable powers of acquisition, but no ability to produce anything absolutely original. In the case of Lincoln, for example, we find that in his youth he was as distinguished by diligence in study as by physical stature and prowess. After he withdrew from school, he read, wrote, and ciphered (in the intervals of manual work) almost incessantly. He read everything he could lay hands on. He copied out what most appealed to him. A few books he read and re-read till he had almost memorized them. What constituted his library? The Bible, Æsop's Fables, Robinson Crusoe, The Pilgrim's Progress, a Life of Washington, a History of the United States. These established for him a vital relation with the past, and laid the foundations of a democratic culture; not the culture of a Chesterfield, to be sure, but something immeasurably better, and none the less good for being almost universally accessible. Lincoln developed his logical powers conning the dictionary. Long before he undertook the regular study of the law, he spent long hours poring over the revised statutes of the State in which he was living. From a book he mastered with a purpose the principles of grammar. In the same spirit he learned surveying, also by means of a book. There is no need to ignore any of the influences that told toward the development of this great statesman, the greatest of English-speaking orators, but it is evident that remote as was his habitation from all the famous centers of learning he was, nevertheless, early immersed in the current of the world's best thought.

Similarly, in the history of science, every great thinker has his intellectual pedigree. Aristotle was the pupil of Plato, Plato was the disciple of Socrates, and the latter's intellectual genealogy in turn can readily be traced to Thales, and beyond—to Egyptian priests and Babylonian astronomers.

The city of Alexandria, founded by the pupil of Aristotle in 332 B.C., succeeded Athens as the center of Greek culture. On the death of Alexander the Great, Egypt was ruled by one of his generals, Ptolemy, who assumed the title of king. This monarch, though often engaged in war, found time to encourage learning, and drew to his capital scholars and philosophers from Greece and other countries. He wrote himself a history of Alexander's campaigns, and instituted the famous library of Alexandria. This was greatly developed (and supplemented with schools of science and an observatory) by his son Ptolemy Philadelphus, a prince distinguished by his zeal in promoting the good of the human species. He collected vast numbers of manuscripts, had strange animals brought from distant lands to Alexandria, and otherwise promoted scientific research. This movement was continued under Ptolemy III (246-221 B.C.).

Something has already been said of the early astronomers and mathematicians of Alexandria. The scientific movement of the later Alexandrian period found its consummation in the geographer, astronomer, and mathematician Claudius Ptolemy (not to be confused with the rulers of that name). He was most active 127-151 A.D., and is best known by his work the Syntaxis, which summarized what was known in astronomy at that time. Ptolemy drew up a catalogue of 1080 stars based on the earlier work of Hipparchus. He followed that astronomer in teaching that the earth is the center of the movement of the heavenly bodies, and this geocentric system of the heavens became known as the Ptolemaic system of astronomy. To Hipparchus and Ptolemy we owe also the beginnings of the science of trigonometry. The Syntaxis sets forth his method of drawing up a table of chords. For example, the side of a hexagon inscribed in a circle is equal to the radius, and is the chord of 60°, or of the sixth part of the circle. The radius is divided into sixty equal parts, and these again divided and subdivided sexagesimally. The smaller divisions and the subdivisions are known as prime minute parts and second minute parts (partes minutæ primæ and partes minutæ secundæ), whence our terms "minute" and "second." The sexagesimal method of dividing the circle and its parts was, as we have seen in the first chapter, of Babylonian origin.

Ptolemy was the last of the great Greek astronomers. In the fourth century and at the beginning of the fifth, Theon and his illustrious daughter Hypatia commented on and taught the astronomy of Ptolemy. In the Greek schools of philosophy Plato's doctrine of the supreme reality of the invisible world was harmonized for a time with Christian mysticism, but these schools were suppressed at the beginning of the sixth century. The extinction of scientific and of all other learning seemed imminent.

What were the causes of this threatened break in the historical continuity of science? They were too many and too varied to admit of adequate statement here. From the latter part of the fourth century the Roman Empire had been overrun by the Visigoths, the Vandals, the Huns, the Ostrogoths, the Lombards, and other barbarians. Even before these incursions learning had suffered under the calamity of war. In the time of Julius Cæsar the larger of the famous libraries of Alexandria, containing, it is computed, some 490,000 rolls, caught fire from ships burning in the harbor, and perished. This alone involved an incalculable setback to the march of scientific thought.

Another influence tending to check the advance of the sciences was the clash between Christian and Pagan ideals. To many of the bishops of the Church the aims and pursuits of science seemed vain and trivial when compared with the preservation of purity of character or the assurance of eternal felicity. Many were convinced that the end of the world was at hand, and strove to fix their thoughts solely on the world to come. Their austere disregard of this life found some support in a noble teaching of the Stoic philosophy that death itself is no evil to the just man. The early Christian teachers held that the body should be mortified if it interfered with spiritual welfare. Disease is a punishment, or a discipline to be patiently borne. One should choose physical uncleanliness rather than run any risk of moral contamination. It is not impossible for enlightened people at the present time to assume a tolerant attitude toward the worldly Greeks or the other-worldly Christians. At that time, however, mutual antipathy was intense. The long and cruel war between science and Christian theology had begun.

Not all the Christian bishops, to be sure, took a hostile view of Greek learning. Some regarded the great philosophers as the allies of the Church. Some held that churchmen should study the wisdom of the Greeks in order the better to refute them. Others held that the investigation of truth was no longer necessary after mankind had received the revelation of the gospel. One of the ablest of the Church Fathers regretted his early education and said that it would have been better for him if he had never heard of Democritus. The Christian writer Lactantius asked shrewdly whence atoms came, and what proof there was of their existence. He also allowed himself to ridicule the idea of the antipodes, a topsy-turvy world of unimaginable disorder. In 389 A.D. one of the libraries at Alexandria was destroyed and its books were pillaged by the Christians. In 415 Hypatia, Greek philosopher and mathematician, was murdered by a Christian mob. In 642 the Arabs having pushed their conquest into northern Africa gained possession of Alexandria. The cause of learning seemed finally and irrecoverably lost.

The Arab conquerors, however, showed themselves singularly hospitable to the culture of the nations over which they had gained control. Since the time of Alexander there had been many Greek settlers in the larger cities of Syria and Persia, and here learning had been maintained in the schools of the Jews and of a sect of Christians (Nestorians), who were particularly active as educators from the fifth century to the eleventh. The principal Greek works on science had been translated into Syrian. Hindu arithmetic and astronomy had found their way into Persia. By the ninth century all these sources of scientific knowledge had been appropriated by the Arabs. Some fanatics among them, to be sure, held that one book, the Koran, was of itself sufficient to insure the well-being of the whole human race, but happily a more enlightened view prevailed.

In the time of Harun Al-Rashid (800 A.D.), and his son, the Caliphate of Bagdad was the center of Arab science. Mathematics and astronomy were especially cultivated; an observatory was established; and the work of translation was systematically carried on by a sort of institute of translators, who rendered the writings of Aristotle, Hippocrates, Galen, Euclid, Ptolemy, and other Greek scientists, into Arabic. The names of the great Arab astronomers and mathematicians are not popularly known to us; their influence is greater than their fame. One of them describes the method pursued by him in the ninth century in taking measure of the circumference of the earth. A second developed a trigonometry of sines to replace the Ptolemaic trigonometry of chords. A third made use of the so-called Arabic (really Hindu) system of numerals, and wrote the first work on Algebra under that name. In this the writer did not aim at the mental discipline of students, but sought to confine himself to what is easiest and most useful in calculation, "such as men constantly require in cases of inheritance, legacies, partition, law-suits, and trade, and in all their dealings with one another, or where the measuring of lands, the digging of canals, geometrical computation, and other objects of various sorts and kinds are concerned."

In the following centuries Arab institutions of higher learning were widely distributed and the flood-tide of Arab science was borne farther west. At Cairo about the close of the tenth century the first accurate records of eclipses were made, and tables were constructed of the motions of the sun, moon, and planets. Here as elsewhere the Arabs displayed ingenuity in the making of scientific apparatus, celestial globes, sextants of large size, quadrants of various sorts, and contrivances from which in the course of time were developed modern surveying instruments for measuring horizontal and vertical angles. Before the end of the eleventh century an Arab born at Cordova, the capital of Moorish Spain, constructed the Toletan Tables. These were followed in 1252 by the publication of the Alphonsine Tables, an event which astronomers regard as marking the dawn of European science.

Physics and chemistry, as well as mathematics and astronomy, owe much in their development to the Arabs. An Arabian scientist of the eleventh century studied the phenomena of the reflection and refraction of light, explained the causes of morning and evening twilight, understood the magnifying power of lenses and the anatomy of the human eye. Our use of the terms retina, cornea, and vitreous humor may be traced to the translation of his work on optics. The Arabs also made fair approximations to the correct specific weights of gold, copper, mercury, and lead. Their alchemy was closely associated with metallurgy, the making of alloys and amalgams, and the handicrafts of the goldsmiths and silversmiths. The alchemists sought to discover processes whereby one metal might be transmuted into another. Sulphur affected the color and substance. Mercury was supposed to play an important part in metal transmutations. They thought, for example, that tin contained more mercury than lead, and that the baser, more unhealthy metal might be converted into the nobler and more healthy by the addition of mercury. They even sought for a substance that might effect all transmutations, and be for mankind a cure for all ailments, even that of growing old. The writings that have been attributed to Geber show the advances that chemistry made through the experiments of the Arabs. They produced sulphuric and nitric acids, and aqua regia, able to dissolve gold, the king of metals. They could make use of wet methods, and form metallic salts such as silver nitrate. Laboratory processes like distilling, filtering, crystallization, sublimation, became known to the Europeans through them. They obtained potash from wine lees, soda from sea-plants, and from quicksilver the mercuric oxide which played so interesting a part in the later history of chemistry.

Much of the science lore of the Arabs arose from their extensive trade, and in the practice of medicine. They introduced sugar-cane into Europe, improved the methods of manufacturing paper, discovered a method of obtaining alcohol, knew the uses of gypsum and of white arsenic, were expert in pharmacy and learned in materia medica. They are sometimes credited with introducing to the West the knowledge of the mariner's compass and of gunpowder.

Avicenna (980-1037), the Arab physician, not only wrote a large work on medicine (the Canon) based on the lore of Galen, which was used as a text-book for centuries in the universities of Europe, but wrote commentaries on all the works of Aristotle. For Averroës (1126-1198), the Arab physician and philosopher, was reserved the title "The Commentator," due to his devotion to the works of the Greek biologist and philosopher. It was through the commentaries of Averroës that Aristotelian science became known in Europe during the Middle Ages. In his view Aristotle was the founder and perfecter of science; yet he showed an independent knowledge of physics and chemistry, and wrote on astronomy and medicine as well as philosophy. He set forth the facts in reference to natural phenomena purely in the interests of the truth. He could not conceive of anything being created from nothing. At the same time he taught that God is the essence, the eternal cause, of progress. It is in humanity that intellect most clearly reveals itself, but there is a transcendent intellect beyond, union with which is the highest bliss of the individual soul. With the death of the Commentator the culture of liberal science among the Arabs came to an end, but his influence (and through him that of Aristotle) was perpetuated in all the western centers of education.

The preservation of the ancient learning had not, however, depended solely on the Arabs. At the beginning of the sixth century, before the taking of Alexandria by the followers of Mohammed, St. Benedict had founded the monastery of Monte Cassino in Italy. Here was begun the copying of manuscripts, and the preparation of compendiums treating of grammar, dialectic, rhetoric, arithmetic, astronomy, music, and geometry. These were based on ancient, Roman writings. Works like Pliny's Natural History, the encyclopedia of the Middle Ages, had survived all the wars by which Rome had been devastated. Learning, which in Rome's darkest days had found refuge in Britain and Ireland, returned book in hand. Charlemagne (800) called Alcuin from York to instruct princes and nobles at the Frankish court. At this same palace school half a century later the Irishman Scotus Erigena exhibited his learning, wit, and logical acumen. In the tenth century Gerbert (Pope Sylvester II) learned mathematics at Arab schools in Spain. The translation of Arab works on science into the Latin language, freer intercourse of European peoples with the East through war and trade, economic prosperity, the liberation of serfs and the development of a well-to-do middle class, the voyages of Marco Polo to the Orient, the founding of universities, the encouragement of learning by the Emperor Frederick II, the study of logic by the schoolmen, were all indicative of a new era in the history of scientific thought.

The learned Dominican Albertus Magnus (1193-1280) was a careful student of Aristotle as well as of his Arabian commentators. In his many books on natural history he of course pays great deference to the Philosopher, but he is not devoid of original observation. As the official visitor of his order he had traveled through the greater part of Germany on foot, and with a keen eye for natural phenomena was able to enrich botany and zoölogy by much accurate information. His intimacy with the details of natural history made him suspected by the ignorant of the practice of magical arts.

His pupil and disciple Thomas Aquinas (1227-1274) was the philosopher and recognized champion of the Christian Church. In 1879 Pope Leo XIII, while proclaiming that every wise saying, every useful discovery, by whomsoever it may be wrought, should be welcomed with a willing and grateful mind, exhorted the leaders of the Roman Catholic Church to restore the golden wisdom of St. Thomas and to propagate it as widely as possible for the good of society and the advancement of all the sciences. Certainly the genius of St. Thomas Aquinas seems comprehensive enough to embrace all science as well as all philosophy from the Christian point of view. According to him there are two sources of knowledge, reason and revelation. These are not irreconcilably opposed. The Greek philosophers speak with the voice of reason. It is the duty of theology to bring all knowledge into harmony with the truths of revelation imparted by God for the salvation of the human race. Averroës is in error when he argues the impossibility of something being created from nothing, and again when he implies that the individual intellect becomes merged in a transcendental intellect; for such teaching would be the contrary of what has been revealed in reference to the creation of the world and the immortality of the individual soul. In the accompanying illustration we see St. Thomas inspired by Christ in glory, guided by Moses, St. Peter, and the Evangelists, and instructed by Aristotle and Plato. He has overcome the heathen philosopher Averroës, who lies below discomfited.

ST. THOMAS AQUINAS OVERCOMING AVERROËS

The English Franciscan Roger Bacon (1214-1294) deserves to be mentioned with the two great Dominicans. He was acquainted with the works of the Greek and Arabian scientists. He transmitted in a treatise that fell under the eye of Columbus the view of Aristotle in reference to the proximity of another continent on the other side of the Atlantic; he anticipated the principle on which the telescope was afterwards constructed; he advocated basing natural science on experience and careful observation rather than on a process of reasoning. Roger Bacon's writings are characterized by a philosophical breadth of view. To his mind the earth is only an insignificant dot in the center of the vast heavens.

In the centuries that followed the death of Bacon the relation of this planet to the heavenly bodies was made an object of study by a succession of scientists who like him were versed in the achievements of preceding ages. Peurbach (1423-1461), author of New Theories of the Planets, developed the trigonometry of the Arabians, but died before fulfilling his plan to give Europe an epitome of the astronomy of Ptolemy. His pupil, Regiomontanus, however, more than made good the intentions of his master. The work of Peurbach had as commentator the first teacher in astronomy of Copernicus (1473-1543). Later Copernicus spent nine years in Italy, studying at the universities and acquainting himself with Ptolemaic and other ancient views concerning the motions of the planets. He came to see that the apparent revolution of the heavenly bodies about the earth from east to west is really owing to the revolution of the earth on its axis from west to east. This view was so contrary to prevailing beliefs that Copernicus refused to publish his theory for thirty-six years. A copy of his book, teaching that our earth is not the center of the universe, was brought to him on his deathbed, but he never opened it.

Momentous as was this discovery, setting aside the geocentric system which had held captive the best minds for fourteen slow centuries and substituting the heliocentric, it was but a link in the chain of successes in astronomy to which Tycho Brahe, Kepler, Galileo, Newton, and their followers contributed.