The House of Wisdom Read online

  Long supply lines and a unified Islam were not the only problems facing the Christian forces. Born in the West of iron and blood at the close of the eleventh century, the crusader movement immediately found itself deeply enmeshed in the life of the Muslim East in ways that would have horrified men like Peter the Hermit and Pope Urban II, who died just days before the news of Jerusalem’s capture could reach his sickbed in Rome. As countless attackers had before it, the Army of the Cross discovered that the very act of invasion and conquest left its mark on the besiegers as well as the besieged. There would be numerous campaigns to come—even the enduring mystery of the so-called Children’s Crusade of 1212, which, legend has it, ended in death by shipwreck or enslavement in Muslim lands—but the idea of crusade and crusading would never really be the same.

  At first, such changes appeared relatively insignificant: Usama ibn Munqidh’s bemused accounts of how the Muslims had quickly begun to civilize the Europeans; or the way the Christians slipped so easily into the local factional disputes, even siding at times with Muslim warlords and against their coreligionists. Other, more powerful factors soon came to the fore, including the spectacular growth of East-West trade. The church clearly recognized the danger that such trade posed to its anti-Muslim agenda, and papal orders and outraged church councils periodically sought to crack down on commerce with the infidel, particularly in such strategic goods as wood for shipbuilding, iron, arms, and even foodstuffs.50

  Still, money from this new trade with the East began to pour into the merchant leagues of southern Europe. Genoa came to dominate commerce with North Africa and the Black Sea region, while Venice maintained a money-spinning stranglehold on trade with Egypt and Syria.51 Along with shipments of oil, perfumes, textiles, and precious metals came new ideas, technologies, and systems of thought. Our modern Arabic numerals were popularized in the West thanks in large measure to trade documents and contracts drawn up between Muslim merchants and their Italian counterparts. Trade terms in numerous European languages still bear the mark of Arabic and Persian commerical usage: for example, check, tariff, traffic, arsenal, and the French douane, or “customs.”52 Long-haul seaborne commerce required navigational aids, such as sophisticated maps, charts, and instruments, all areas where the medieval Muslims excelled. One measure of the growing economic ties between East and West was the appearance in European royal treasuries, as far away as England, of considerable quantities of Muslim gold. The minting of gold coins, halted in ninth-century Europe for lack of bullion, resumed in the Italian city-states four centuries later, once supplies from the East were secured.53

  The new rulers of the Latin East soon began to realize that their own fates were bound up with those of the Muslims, Christian Arabs, Jews, and others who populated the region; there would be no significant reinfusion of European Christians to help colonize the crusader states. The ever-adaptable Normans took on the best aspects of Arab life even as they expelled Muslim rulers from the eastern Mediterranean, creating sumptuous courts whose learning and culture began to rival those of the great caliphs. At the same time the symbolic value of Jerusalem as a place worthy of fighting, slaughtering, and dying for began to fade—if only gradually—in the face of these new economic, political, and cultural realities.

  Changes in the behavior and tactics of the crusaders were also striking. Later campaigns, which continued off and on for centuries, were either largely defensive affairs designed to claim territory already retaken by the Muslims or else perverted by raw political ambition and outright greed, such as the sack of Christian Constantinople in 1204 at the instigation of the powerful merchants of Venice. One “Crusade” involved a negotiated and temporary transfer of authority over Jerusalem, a favor by Muslim sultan to Christian king—a circumstance few could have predicted at the time of Clermont. At other times, crusading armies were offered control of Jerusalem, once the object of their most fervent desires, in exchange for Muslim territory seized elsewhere; they declined only to leave the Near East empty-handed.

  The steady success of Christian forces in Spain and the reemergence of Christian military power in the Mediterranean, especially the capture by the Normans of once-Muslim Sicily, had already brought the worlds of Islam and Christendom into close contact and direct competition. But the First Crusade opened a third pathway between East and West, one in which brute military struggle would slowly give way to a web of commercial, cultural, and intellectual bonds between two rival but ultimately inseparable worlds. By the time Adelard of Bath arrived in Antioch around 1114, Arab culture—if not Muslim military might—held sway over much of life in the so-called Latin East.

  Chapter Two

  THE EARTH IS LIKE A WHEEL

  SEVEN YEARS BEFORE the earthquake that shook the moral foundations of crusader Antioch, Adelard surveyed the world around him and pronounced it rotten. His recent studies at the famed French cathedral school at Tours had provided him with the best education of his day. He enjoyed the support and patronage of the powerful bishop of Bath, the French court physician and scholar John de Villula. He practiced the art of hunting with falcons, a sign of his noble rank and the life of leisure it generally afforded. And he was an accomplished musician, who years later still fondly recalled the time he had been invited to play the cithara, a forerunner of the guitar, for the queen.

  In short, Adelard of Bath was the model country gentleman. His father, Fastrad, was one of Bishop John’s richest tenants and most senior aides, ensuring a life of privilege for his son. The family appears sporadically in official documents of church and state. The Pipe Rolls, or royal accounts, later list Adelard as the beneficiary of a pension from the revenues of Wiltshire, in southwest England. Still, young Adelard saw little of value in the contemporary world, and he despaired at the state of Western learning in particular. “When I examine the famous writings of the ancients—not all of them, but most—and compare their talents with the knowledge of the moderns, I judge the ancients eloquent, and call the moderns dumb,” he proclaimed in the opening line of his coming-of-age essay and first known work, On the Same and the Different.1

  Adelard’s disdain for “the moderns” was understandable, for the West at the end of the eleventh century was a mess. Daily life staggered under the burden of rampant violence and social instability. Bands of mercenaries, answerable to neither king nor God, prowled the countryside, their commanders’ word the only law of the land. Across Europe, primitive farming techniques could no longer keep pace with a growing population, while antiquated inheritance laws left many impoverished and desperate.2 Violence—inflamed by the weakness of central political authority and uninhibited by the tenuous moral grip of the Catholic Church—was the currency of the day. As Pope Urban II had acknowledged at Clermont when he called for the First Crusade, religious leaders were helpless to halt the chaos across the continent. The best the church could do was to redirect its flock’s baser nature against the infidels to the East.

  Not even Adelard’s remote corner of England was immune to the troubles. It was not long since the Norman Conquest of 1066, and political and social strife still plagued the land. The uneasy relationship—for centuries punctuated by bouts of armed conflict—between what today comprise the distinct nations of England and France was a regular feature of late medieval life. At the same time, political, cultural, and personal ties ran deep, and so it was not surprising that Adelard could pursue higher education in Tours and that many leading officials and courtiers, like Bishop John, hailed from the European mainland. In 1086, as a young child, Adelard had seen his native West Country town, including its once-proud abbey of black-robed monks, burned almost to the ground during an uprising against the heir to the throne, William the Red. The rebels had hoped to secure the rule of William’s brother, Robert of Normandy, but their bid for power had ended in bloody failure and considerable destruction. Robert, eldest son of William the Conqueror, later died a royal prisoner.

  Things were little better inside the elite cathedral schoo
ls. The chaos and disorder that had swept in with the Germanic invasions of the western Roman Empire, beginning in the fourth century A.D., had just about destroyed formal education and the perpetuation of classical knowledge. The Muslim conquests around the eastern Mediterranean three hundred years later sealed the West’s isolation by choking off easy access to the Byzantine Christians based in far-off Constantinople, where some traces of the Greek intellectual tradition could still be found.3 The wonders of classical learning were all but forgotten, or at best pushed to the extreme margins of European consciousness. Invaluable texts were lost through inattention, destroyed in war, or rendered unintelligible by the general ignorance of would-be scholars or simply by the lost ability to read Greek. The aristocracy of the Roman Empire read the Greek masters in the original, so there was no need at the time for Latin translations of the philosophy of Plato and Aristotle, the engineering wonders of Archimedes, or the geometry of Euclid. The wholesale disappearance of Greek as the language of learning meant centuries of knowledge virtually vanished from the collective mind of Latin-speaking Europe.

  There were a few outposts—scattered monasteries in Ireland, northern England, Catalonia, and southern Italy—where the monks labored to keep the classical traditions alive. Yet the results were meager in comparison with the heights once scaled by the Greeks, or with the new and exciting work being carried out in the Arab world. At the West’s leading center of mathematical studies, the cathedral school of Laon, the best minds of Adelard’s day had no grasp of the use of zero. The masters at Laon taught the latest techniques employed by King Henry I, who ruled both England and Normandy in the early twelfth century, to manage his treasury. These included the use of a special tablecloth, marked out in rows and columns like a chessboard and based on the principles of the abacus, which had reached France from Arab Spain some years before. The cloth was known as the scaccarium, Latin for “chessboard,” and was the origin of the English term for a national treasury, exchequer. Despite the importance of this royal mission, the standard of learning at Laon remained very low; one contemporary textbook reveals consistent errors in even the most basic calculations.4

  More vexing than sloppy royal accounting was the inability to measure the hours of the day or keep the calendar. Even by the sleepy standards of medieval Christendom, time was a serious business, linked as it was with the pursuit of heavenly salvation. The Rule of St. Benedict, which governed thousands of monasteries from the sixth century onward, required eight sets of prayers at specific times every twenty-four hours. The practice was based on a reading of two verses in Psalm 119: “Seven times a day I praise thee” and “At midnight I rise to give thee thanks.”5 This was relatively simple during the day, when the changing position of the sun could provide a rough guide to the hour, but at night the monks of the Latin West were left literally in the darkness of their own ignorance.

  Crude methods of timekeeping evolved to fulfill the demands of the rule. It was found, for example, that a twelve-inch wax candle of a certain diameter would last about four hours.6 A handful of the more prosperous monasteries employed elementary water clocks, in which the regulated flow of water into a container measured the passage of a given unit of time. In an early example of practical astronomy, the sixth-century prelate Gregory of Tours offered a rule of thumb, possibly Babylonian in origin, that accounted for the changing length of the days by beginning at nine hours of daylight in December and adding one hour per month from December to June, to make fifteen hours. The process was then reversed from June back to December. Popular in its day for its simplicity and ease of use, the system is nonetheless undermined by a lack of scientific understanding: The ratio of fifteen to nine is better suited to the latitudes of the Mediterranean and the Near East than it is to the northern climes of Tours.7 Gregory presented a similar method for keeping track of the changing phases of the moon through the course of the month, but he made no provisions for seasonal changes. And he identified some constellations in the northern sky—taking pains not to use their pagan names—that could be used on clear nights to help regulate the prayers.8

  Other attempts at attacking the problem suffered well into the Middle Ages from flaws similar to those that marred Gregory’s early efforts. A Saxon sundial at a church in Yorkshire dating to 1064, for example, divides the day into eight equal units, or “tides,” but it fails to take into account the fact that Yorkshire’s latitude requires that these tides vary in length.9 Lacking any real understanding of the theory behind techniques borrowed from the southern Mediterranean of the Middle East, the Latins did not realize they had to adjust their approach to account for their own more northerly locales, such as Adelard’s own town of Bath.

  As late as the thirteenth century, monks in France relied on informal systems such as local observational markers that could be aligned with the constellations to correspond to certain prayer times. A text written on a piece of slate found at the Cistercian Villers Abbey, near Namur in Belgium, explains how to estimate the time by tracing the sun and stars as they appear at various windows.10 Most common of all, perhaps, was the appointment of a senior and respected monk as the significator horarum, who would chant a set number of psalms to note the progress of the hours and then awaken his brethren for their vigils, to be held at the “eighth hour of darkness.”11 This had the obvious advantage of functioning even when the stars were obscured by the clouds. But the method was so imprecise that theologians were forced to concede that ordinary monks should not be held responsible for any resulting failure by the significator to start the required prayer on time.

  Monastic timekeeping, however, was not only a matter for the soul. With no reliable way to measure the passing of the hours, Western man’s imagination—and his very existence—remained hostage to the shifting cycles of night and day and the organic phases of planting and harvesting. Accurate timekeeping would one day free society from the dictates of sunrise and sunset and recast the day or the hour as an abstract notion distinct from daily existence. This would eventually foster a new way of looking at the universe as something that could be measured, calculated, and controlled, opening up the realms of science and technology. The regular ringing of the monastery bells, governed by the rhythms of the monks’ devotional and practical duties, provided one of medieval daily life’s very few sureties and marked the tentative beginnings of an organized social order.12

  Like the counting of the hours, accurately setting the date for the movable feast of Easter—the holiest day in the Christian calendar and the reference point for the entire ecclesiastical year—proved beyond the abilities of even the most learned of monks. While politics, tradition, and regional and sectarian rivalries invariably intruded throughout the centuries, the essential problem in fixing Easter lay in its ties to the astronomical cycle of the solar year, which was out of step with the calendar of daily life. Majority Christian opinion puts Easter on the first Sunday following the first full moon after the spring equinox. This could be determined only by observation and advanced calculation. For a world alienated from the very idea of science by its own focus on the afterlife and cut off by choice and circumstance from the great intellectual traditions of the classical world, both accurate calculation and meticulous observation were in short supply. The result was endless wrangling over the very notions of time and date. Estimates of the spring equinox, for example, often varied by as much as two weeks.

  Naturally enough, the early church fathers adopted the Roman system of dates that prevailed in their day. The so-called Julian calendar was created by the Greek astronomer Sosigenes of Alexandria and imposed with a few minor changes by order of Julius Caesar forty-six years before the birth of Christ. But there was a hitch: The calendar rests on a year that is roughly eleven minutes and fourteen seconds too long, a well-known flaw that would not have escaped Sosigenes and his fellow astronomers. The spring equinox fell on March 25 when the Julian calendar was first introduced, but it was slipping “backward” at the considerable rate of a
bout one full day every 130 years, threatening to take Easter and the rest of the church calendar with it.

  As the young Christian community grew and expanded its reach, it naturally sought uniformity in the celebration of its most holy day. “What could be more beautiful … than that this feast day, from which we receive hope of immortality, be observed by all according to one and the same order and certain rule?” Emperor Constantine asked in 325 from his place of honor at the Council of Nicea, which nonetheless failed to resolve the Easter controversy.13 Still, church leaders were eager to head off disputes like the one that later erupted in England between Christians of the so-called Roman conversion and followers of the older Celtic tradition from Ireland.14 This required either the command of a recognized central religious or political authority or an agreed-on set of principles—scriptural or astronomical—clearly spelling out the proper day to celebrate the Resurrection. Lacking all of these, Christendom instead came to rely on the computus, a system of practical astronomy that evolved slowly over the centuries to provide rough approximations of date and time. The calculations themselves were arithmetic, and so there was no need to master the geometric concepts, such as the circle and the sphere, so integral to the proper study of astronomy.

  Even where explicit guidance from the ancients was on hand, the West proved beyond help. A Latin translation of a simplified, step-by-step guide by the great classical Greek astronomer Ptolemy for determining the positions of the sun and the moon survives in the form of a medieval manuscript dating from around 1000. This would have greatly improved the work of the “computists” in fixing Easter and related calculations. But apparently, even the rudimentary understanding of astronomical terms needed just to use Ptolemy’s Handy Tables, much less to understand his full text, was well beyond the reach of contemporary scholars.15 It was not until the late sixteenth century that the Christian West could mobilize enough scientific firepower to begin to gain control of time and grapple successfully with the problem of calendar reform. By then, the equinox had drifted backward about two weeks, to mid-March.