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- OCKHAM, WILLIAM OF
- [Ill] HENRY THE NAVIGATOR
61 [1051 POLO
POLO [105] floating would align itself roughly north and south. Some time before 1200, Eu ropean navigators began to use such a needle (a “compass”) to guide them in their voyages. Legend has it that the Chinese made the discovery centuries earlier and the Europeans picked up the knowledge via the Arabs, but this is un certain.
In any case, in 1269, while taking part in the slow and dull siege of an Italian city. Peregrinus wrote a letter to a friend in which he described his researches on magnets. He showed how to determine the north and south poles of a magnet, pointed out that like poles repelled each other whereas unlike poles attracted. He also explained that one could not isolate one of the poles by breaking a magnet in two. because each half was then a com plete magnet with both a north and south pole. Most important of all, perhaps, he de scribed an improved compass to be formed by placing the magnetic needle on a pivot, rather than allowing it to float on a piece of cork, and surrounding it by a graduated circular scale to allow directions to be read more accurately. Undoubtedly it was this device that made the compass really practical; and it was, in turn, the use of a practical com pass that gave European navigators the self-confidence needed to sail into the Atlantic far out of sight of land. Pere grinus thus was another herald of the great Age of Exploration that was to begin in another century and a half. Where Peregrinus chiefly failed was in his explanation of the reason for the north-south alignment of the needle. He believed the needle pointed to the pole of the celestial sphere, the outermost of the spheres in the Ptolemaic heavens. A better explanation had to await Gilbert [155], [105] POLO, Marco Italian explorer Born: Venice, about 1254 Died: Venice, January 9, 1324 Marco Polo came of a family of well- to-do Venetian merchants. While he was 6 2
still a young boy, his father, Nicolo, and his uncle, Maffeo, set out eastward on a trading mission. They began in 1260 at an unusual time in history. A half century earlier the Mongol, Genghis Khan, had begun a remarkable career of conquest and now his grandson, Kublai Khan, acknowl edged as head of the various Mongol princes, ruled over an immense empire that, for the first time, placed much of Asia and Europe under a single rule and made travel over that whole area practi cal.
Kublai Khan had the Venetians brought to his summer palace at Shangtu in China (Coleridge, in his famous poem “Kublai Khan” called it Xanadu). The Mongol ruler was fascinated by them and eventually sent them back to Europe to bring missionaries to teach him and his people Christianity. The Polos unfor tunately found the papacy in the turmoil of an interregnum. The missionaries were never sent and the great chance to Christianize the Far East never returned. The Polos returned to China in 1275 and this time Marco was with them. Marco in particular rose to high place and was a trusted diplomat in Kublai Khan’s service. In the khan’s old age, however, the Polos felt they could not trust in the favor of his successor and, when they were given the mission of es corting a Mongol princess to Persia, they seized the opportunity to continue on ward toward home. They finally reached Venice again in 1295. Central Asia was not to be observed by Europeans in such detail for five more centuries. Marco Polo’s stories of the wonders he had seen and of the high civilization of the Far East in the midsummer of Mon gol domination was greeted with derision and he was named Marco Milioni (Marco Millions) because he dealt with such large numbers in his descriptions. In 1298 Venice and Genoa renewed their naval wars and Marco Polo held a command in the Venetian fleet. He was captured. While in a Genoese prison he dictated the story of his travels. He did not deal so much with personal matters as with a description of the portions of Asia and Africa with which he was rea-
[106] d ’ abano BURIDAN
[108] sonably familiar. A year later he was released and allowed to return to Venice. The book was popular, but it was largely disbelieved and considered an en tertaining but implausible tissue of tall tales. It was not until five and a half cen turies later that European explorers finally penetrated the interior of Asia and found that, on the whole, and bar ring a few wonder stories, Marco Polo was accurate in his description of such matters as coal, asbestos, and paper cur rency.
The importance of the book lay in its portrayal of the wealth of the “Indies.” Columbus [121] owned a copy of Polo’s book and scribbled enthusiastic marginal notes in it. It was Marco Polo’s great trek east that drove Columbus west in the hope of arriving at the same destina tion. Marco Polo therefore contributed his bit toward the intellectual ferment that was to break over Europe within two centuries, broadening horizons both geographically and intellectually. [106] D’ABANO, Pietro (dalTbah-noh) Italian physician Born: Abano, near Padua, 1257 Died: Padua, about 1315 D’Abano, after studying at Padua, traveled through Greece and the Near East, visiting Constantinople, absorbing knowledge of Arabic medicine, then completed his formal Western training at Paris. He had apparently met Marco Polo [105] and caught a breath of the world that was still beyond the medieval horizon. As Marco Polo foreshadowed the great Age of Exploration soon to come, so D’Abano foreshadowed the great Age of Science. He wrote a book entitled Conciliator in which he tried to weave together the Greek and Arabic schools of medicine and in which he ex pressed some ideas that were well ahead of his time. For instance, he maintained that the brain was the source of the nerves, and the heart of the blood ves sels. He also stated that air had weight, and he made an unusually accurate esti mate of the year. He was, however, convinced of the usefulness of astrology and, like so many of the scholars of the period was sus pected of magical practices (particularly by competing physicians less successful in their practice). He was brought up twice for heresy before the Inquisition because he re jected the miraculous aspects of the gos pel tales. He was acquitted the first time and died during the course of the second trial. [107] FALSE GEBER Born: Perhaps about 1270 Died: Date unknown Nothing is known of him, not even his name (for he wrote under the pseud onym of Geber [76]), except that he was probably a Spaniard, like Arnold of Vil lanova [103], and that he wrote about 1300. He was the first to describe sul furic acid, the most important single in dustrial chemical used today. The al chemical discovery of sulfuric acid and the other strong acids is, by all odds, the greatest chemical achievement of the Middle Ages. It made possible all sorts of changes that could not be brought about by vinegar, the strongest acid known to the ancients. The discovery was infinitely more important than the preparation of gold would have been, for even if gold could be prepared, the mere fact that it could, would erase its value. Gold, after all, is a comparatively useless metal (although admittedly the most beautiful) and has few values that do not stem from its rarity. [108] BURIDAN, Jean (byoo-ree-dahn") French philosopher Born: Béthune, Artois, about 1295 Died: Paris, about 1358 Buridan studied under Ockham [109] and became himself a professor at the University of Paris. He rejected impor tant sections of Aristotle’s [29] theories of physics, then in full sway over the minds of Europe’s scholars. Aristotle had felt that an object in mo 63 [ 1 0 9 ] OCKHAM, WILLIAM OF MONDINO DE’ LUZZI
tion required a continuous force and reasoned that the air supplied that con tinuing force after the initial impetus (that of a catapult, for instance) had been spent. Buridan maintained that the initial impetus was sufficient; and that once it was supplied, motion continued indefinitely. The spheres of heaven, for instance, having been put in motion by God, continued so and required no con stantly working angels to keep them moving. This was an anticipation of Newton’s [231] first law of motion (pro pounded three centuries later). More generally, he believed the same laws of motion prevailed in the heavens as on earth.
Buridan is most famous for a point he is supposed to have made concerning the impossibility of action by free will under two opposite and exactly balanced im pulses. His example was the case of an ass poised exactly between two exactly equivalent bales of hay. Since there would be no reason to choose one bale over the other, the ass would remain in perpetual indecision and would starve to death. However, “Buridan’s ass” is no where to be found in Buridan’s writings, so it is doubtful that he is really the au thor of it. [109] OCKHAM, WILLIAM OF (ok'- um)
English scholar Born: Ockham, Surrey, about 1285
Died: Munich, Germany, 1349 William of Ockham (called the Invin cible Doctor) joined the Franciscan order, studied at Oxford, and lectured there from 1315 to 1319. He was among the last of the medieval scholars and led the battle against the views of Thomas Aquinas [102]. Ockham held that much of theology was a matter of faith, not amenable to reason. For this and, even more so, because he was an opponent of papal supremacy, he was tried for heresy in 1324 by Pope John XXII. He fled and was protected by Holy Roman Emperor Louis IV, who as a strong political oppo nent of the pope automatically favored any antipapal scholar. After Louis’ death, Ockham cautiously made his peace with the church. Ockham battled against the universals that had been introduced by Plato [24], the notion that the only true realities were the ideal objects of which the earthly objects sensible to perception were only imperfect copies. These ideals Ockham considered abstractions, mere names (hence the expression “nomi nalism” for this philosophy), and held that only the objects perceived were real. Since the universalists kept adding more and more items to their ideals in order to make their theories work, Ock ham laid down the rule that: “Entities must not needlessly be multiplied.” This has been interpreted in modern times to mean that of two theories equally fitting all observed facts, that theory requiring the fewer or simpler assumptions is to be accepted as more nearly valid. The rule, now called “Ockham’s razor,” is of vital importance in the philosophy of science. [110] MONDINO DE’ LUZZI (mon- dee'noh day loot'tsee) Italian anatomist Born: Bologna, about 1275 Died: Bologna, 1326 The thirteenth century marked the height of the Middle Ages and thereafter there was a stirring of new viewpoints, particularly in Italy, as was exemplified by Pietro d’Abano [106], The transla tions from the Arabic had aroused an in terest in the nonscientific works of the Greeks and Romans, which were read anew with great appreciation. They in spired imitation and a resurgence of in terest in man and the world (humanism) after the long preoccupation with theol ogy and the afterworld. This was the Re naissance. Scientifically, an interest in man meant the faint stirrings of biology and medi cine. Famous Italian schools of medicine sprang up at Salerno in the ninth century and Bologna in the thirteenth. At Bo logna the art of dissection was revived, not specifically for research but for utili tarian work in connection with legal
[ I l l ] HENRY THE NAVIGATOR ULUGH BEG
cases or medical postmortems and for demonstrations to confirm the views of Galen [65] and Avicenna [86]. The greatest of the Renaissance anato mists was Mondino de’ Luzzi, the son of an apothecary, who studied at the medi cal school at Bologna, under Alderotti [101] graduating about 1290 and joining its teaching staff in 1306. He taught anatomy in a very unusual way for the times. Ordinarily the lec turer, mounted on a high platform, lec tured loftily from the ancient writers while a menial conducted the actual il lustrative dissection. This perpetuated er rors, since the lecturer did not himself see what he was talking about, and the anatomist could not understand the talk concerning what he saw. Mondino, however, did his own dissec tions, and on the basis thereof wrote, in 1316, the first book in history to be devoted entirely to anatomy. (He is therefore called the Restorer of Anat omy.)
Much of Mondino’s terminology is taken from the Arabic and is rather disorderly. The book contains many er rors where Mondino remains too much under the influence of the ancients. He describes the stomach as spherical, gives the liver five lobes instead of three, and sticks to Avicenna’s description of the heart. However, he made some advances, notably in his description of the organs of the reproductive system. In any case, Mondino’s book was to be the best available until the time of Vesa- lius [146], over two centuries later, for Mondino’s successors reverted to the practice of having somebody else do the dissecting.
Portuguese prince Born: Oporto (now Porto), March 4, 1394 Died: Sagres, November 13, 1460 Henry, a younger son of King John 1 of Portugal, was part English, for his mother’s father was John of Gaunt. Henry was thus the great-grandson of Edward III of England. In Henry’s day the tide had turned and the Christians of Portugal were finally recrossing the Strait of Gibraltar to fight the Muslims on African soil. In 1415 Henry took part in a battle at Ceuta, on the northwestern tip of Africa and was knighted for heroism. Although he himself never penetrated deeper into Africa, he fell in love with the continent, or rather with the project of exploring its coasts. He dedicated himself to that sole pur pose, establishing an observatory and school for navigation at Sagres on Cape St. Vincent in 1418. This was in south ernmost Portugal, the southwestern tip of Europe. Year after year he outfitted and sent out ships that inched their way farther and farther down the African coast. He even supervised the collection of astronomic data to ensure the greater safety and success of the ships. It was Henry’s ultimate aim to circum navigate Africa as Hanno [12] had sup posedly done two thousand years before, but in his lifetime his ships only reached the area now marked by Dakar, the west ernmost point on the western bulge of Africa. He died a full generation before the continent was successfully rounded. The light he lit did not go out. Portu guese successes inspired other west Euro pean nations to send expeditions of their own and the great Age of Exploration was under way, reaching its climax with Columbus [121] and Magellan [130]. [112] ULUGH BEG (oo'loog begO Mongol astronomer Born: Soltaniyeh, Persia, March 22, 1394 Died: Samarkand (now part of the Uzbek S.S.R.), October 27, 1449 Ulugh Beg (“great prince”) is the name by which Muhammad Taragay is known. He was a grandson of the Mon gol warrior Tamerlane, last of the great barbarian conquerors. He himself gov erned a portion of the central Asian realm in the lifetime of his father and succeeded to the throne in 1447. His real fame, however, is as the only 65 [113] TOSCANELLI GUTENBERG
important scientist to be found among the Mongols. In 1420 he founded a uni versity in Samarkand, and in 1424 he built an astronomic observatory there, the best in the world at that time. Furthermore, he did more than merely fiddle with Ptolemy’s [64] tables, as Eu ropean astronomers were doing through out the Middle Ages. Ulugh Beg pub lished new tables in the Tadzhik lan guage based on his own observations. They were superior to those of Ptolemy. His star map, containing 994 stars, was the first new one since Hipparchus [50], Ulugh Beg, however, was doomed to obscurity by the accident of space and time. He had no followers and when he was assassinated by his son in 1449, Mongolian astronomy died with him. His observatory was reduced to ruins by 1500 and it was only in 1908 that its remains were found. His writings appeared in Arabic and Persian, but the nations of Europe where astronomy was soon to burst into new and gigantic growth did not hear of him. It was not until 1665 that his tables were translated into Latin and by that time Ulugh Beg had been surpassed by Tycho Brahe [156] and had been made obsolete by the coming of the telescope. Few even today realize that a Mongol prince had once been the greatest astron omer of his time. [113] TOSCANELLI, Paolo (tos-kuh- nel'lee) Italian physician and mapmaker Born: Florence, 1397 Died: Florence, May 15, 1482 Toscanelli, the son of a physician, studied medicine and was a friend of Nicholas of Cusa [115]. He was inter ested in astronomy and made creditable observations of comets. His lone claim to fame, however, and his chief service to science, consisted of a mistake firmly held. He believed that Asia lay three thousand miles west of Europe and drew up a map of the Atlan tic Ocean with Europe on the east and Asia on the west. He showed this to Columbus [121], and that was all Co lumbus needed. [114] GUTENBERG, Johann (goo'ten- berg) German inventor Born: Mainz, Hesse, about 1398 Died: Mainz, about 1468 Little is known of Gutenberg’s early life, except that he used his mother’s maiden name. (His father’s name was Ganzfleisch—“goose meat”—and the change seems an improvement.) About 1430 he had to leave Mainz as a result of being on the losing side of a civic squabble. He went to Strasbourg, a hun dred miles to the south. By 1435 he was involved in a lawsuit, and in that suit the word drucken (printing) was used. Gu tenberg’s attempt to make printing prac tical may have begun as early as that. Until Gutenberg’s time, books were laboriously copied by hand. This meant that they were few and expensive, that only rich men, monasteries, and universi ties could have libraries of dozens of books, that entire cultures had to be satisfied with only one or two really large libraries. (The one at Alexandria was the most famous in all the centuries before Gutenberg.) Furthermore, errors were bound to infiltrate hand-copied books unless the most heroic precautions were taken. (The Jewish copyists of the Bible counted every letter in an effort to guard against error.) The mechanical reproduction of letter ing—incising it in reverse on wood or metal and then pressing the surface against a soft medium or (after inking) on a blank sheet—was known in ancient times. The Sumerians and Babylonians used small intaglios to serve as signatures when impressed in clay, much as we use inked stamps. What Gutenberg conceived, however, was not a one-shot stamp, good only for one purpose, but a series of small stamps, each representing a single letter, which could be assembled to form a page of lettering, then broken down and reassembled to form another page. A limited number of such movable type 6 6
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