The House of Wisdom (13 page)

Perhaps no work brings out the genius of al-Khwarizmi, particularly his ability to identify and master an emerging discipline or technology and then explain it fully and effectively, as much as his treatise on algebra.
The Book of Restoring and Balancing
—the second element of the Arabic title,
Kitab al-jabr wa’l-muqabala
, bequeathed the West the term
algebra
—was dedicated to his patron Caliph al-Mamun and wrapped in a shroud of religious and practical utility. “That fondness for science, by which God had distinguished Imam al-Mamun … has encouraged me to compose a short work, … confining it to what is easiest and most useful in arithmetic, such as men constantly require in cases of inheritance, legacies, partition, law-suits, and trade, and in 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.”
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In one example, al-Khwarizmi guides the reader through the settlement of a woman’s estate after she dies and leaves a husband, a son, and three daughters. Under the prevailing inheritance rules, a husband was entitled to one quarter of the estate, and a son’s share was twice that of a daughter—an improvement over pre-Islamic Arab practice, in which women generally received nothing.
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As al-Khwarizmi shows, a relatively simple algebraic operation solves the equation for any size estate. More complex problems, including the computation of the annual religious tax, or
zakat
, follow.

Here, then, was the beginning of the Arabs’ study of algebra, a field in which they excelled, as demonstrated by both the large number of scholarly commentaries on al-Khwarizmi’s work and their production of many original algebra texts. Over the centuries, the pervasive influence of
The Book of Restoring and Balancing
can be seen in the repeated, verbatim use of several of al-Khwarizmi’s most famous examples of quadratic equations. In his typical fashion, al-Khwarizmi managed to combine Hindu and early Babylonian influence in solving such equations by the means of algebra with the Greek tradition of geometric proofs to validate the results.
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By stressing the relationship between analytic and geometric solutions to such problems and introducing the decimal place system, al-Khwarizmi, for the first time in mathematical history, established the art of analysis as a worthy discipline in its own right and put it on an equal footing with the more glamorous geometry. He also makes clear in later chapters that, his fine introductory remarks to al-Mamun notwithstanding, he is interested in algebraic theory and calculation for their own sake.
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Much of al-Khwarizmi’s intellectual inspiration derived initially from Indian science. The bulk of his astronomy relies on Hindu tradition and, to a lesser extent, Persian teachings. The Indian city of Arin, for example, is used in the
zij al~Sindhind
as the reference point for astronomical measurements, much as the meridian at Greenwich, England, is used today. One version of the
zij
calls Arin the “center of the sphere of the earth.”
⁶⁶
Methods for the determination of the moon’s motion and for measuring the true longitude of a planet betray the work’s strong Hindu roots.
⁶⁷
Al-Khwarizmi devotes the beginning section of his text to conversions between the different calendar systems of the ancient and contemporary world—Arab, Christian, Egyptian, and Persian—and he takes June 16, 632, the beginning of the reign of the last Persian king before the Muslim conquest, as his starting point, or epoch.

Nonetheless, there are already scattered hints at the growing influence of Greek learning on the Arab sciences contained in the
zij al~Sindhind
and in his other works, particularly the algebra text. This is hardly surprising. Al-Khwarizmi’s patron, al-Mamun, presided over the beginning of a turn among the majority of Arab scholars away from early Hindu and Iranian traditions in the hard sciences and toward those of Greece and Hellenistic Egypt. The centerpiece of this flurry of scientific activity under al-Mamun was the translation of Ptolemy’s masterwork of classical Greek astronomy, the single most important book among medieval Arab scholars, after the Koran. Ptolemy was born around 100
A.D.
and spent his working life in Alexandria, then the center of Greek learning and home to the world’s greatest library, forerunner of Baghdad’s own House of Wisdom.

There he produced invaluable works on geography and astrology, among other topics, but none was as vital as the book known among the Greeks as the
Megale Syntaxis
, or “the great composition,” but later recognized universally by the Arabic corruption of its name, the
Almagest
. Ptolemy’s text presents an elaborate and all-encompassing theory of the movement of the fixed stars, the sun, the moon, and the five visible planets—Mercury, Venus, Mars, Jupiter, and Saturn—one that would hold up until the mid-sixteenth century. In terms of Greek science, Ptolemy so dominated the field of astronomy that the works of his most important predecessors virtually disappeared.
⁶⁸
In the West, which would learn of Ptolemy much later through its encounter with Muslim science, he became a mythic, almost mystical, figure often confused with those heirs to Alexander the Great, the Ptolemaic kings of Egypt; medieval images commonly featured the famous astronomer with a crown on his head.

But for the Arabs, the
Almagest
provided a priceless road map for research and study, so much so that it was subject to periodic retranslation, revision, and commentary by the leading scholars of the House of Wisdom throughout the ninth century and beyond. Al-Mamun’s innovative program of astronomical observations at Baghdad and Damascus, for example, was designed to test the results of the
Almagest
and compare them with its own. The star tables that resulted from these experiments eventually superseded those grounded in Hindu science, notably al-Khwarizmi’s
zij al~Sindhind
. The caliph’s geodetic survey on the hot, dusty plain of Sinjar likewise was motivated by questions culled from a careful reading of the
Almagest
. These and other experiments yielded results that often improved significantly on the data provided by Ptolemy—who was notorious for making relatively few observations of his own and instead relying on the earlier observational work of others. Yet there was no immediate sign that such shortcomings in the master’s work dismayed or shocked the Arabs or prompted doubts about the reliability of the general theories presented in the
Almagest
.
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That would come later, after Arab science and philosophy had matured over the course of several centuries.

The royal endorsement of Greek learning may have had almost as much to do with contemporary politics and diplomacy as with intellectual taste or scholarly analysis. The death in 809 of al-Mamun’s father, al-Rashid, sparked a civil war among the Abbasids, and al-Mamun was able to secure power only after a long period of bloody struggle with the forces of his half brother al-Amin. Badly weakened by this war of succession and his own prolonged absence from the capital, al-Mamun took up residence in the Round City determined to centralize political and religious authority in his own hands.

This ruthless consolidation of power was accompanied by a new aggressive tone in the caliph’s foreign policy, one that recast the traditional geopolitical rivalry with the adjacent Byzantine Empire in the stark terms of religious struggle. Even here, state intellectual policy came to the fore: In the new Abbasid view, not only were the Eastern Orthodox Byzantines infidels, but they were also guilty of rejecting classical Greek learning after the coming of Christianity. The religious superiority of Islam was augmented by the fact that the Muslims had had the good sense to recognize the genius of ancient Greece. To oppose the Byzantines was to be in favor of Greek learning, and vice versa.
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Earlier Byzantine harassment of the Nestorian, Syrian, and other eastern Christian scholars, many now taking refuge among the Muslims, appeared to bear out this new propaganda. Al-Mamun was also a supporter of a radical rationalist reading of Islam, a position that appeared to mesh easily with renewed interest in Greek philosophical studies.

Yaqub ibn Ishaq al-Kindi, celebrated as the Philosopher of the Arabs, soon took up the anti-Byzantine refrain. He posited a mythical past in which the ancient forerunners of the Greeks and the Arabs were represented as siblings. It was only natural, al-Kindi suggested, that the Arabs inherit and build upon the earlier work of their brothers, the pre-Christian Greeks, a view that became increasingly entrenched in the Muslim world.
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One century later, the geographer al-Masudi made the link between the arrival of Christianity and the decline of learning explicit: “During the time of the ancient Greeks, and for a little while during the … [Roman] empire, the philosophical sciences kept growing and developing, and scholars and philosophers were respected and honored. They developed their theories on natural science—on the body, the intellect, the soul—and on the quadrivium … The sciences continued to be in great demand and intensely cultivated until the religion of Christianity appeared among the Byzantines; then they effaced the signs of philosophy, eliminated its traces, destroyed its paths, and they changed and corrupted what the ancient Greeks had set forth in clear expositions.”
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The policy of fostering scientific and philosophical activity, research, and innovation addressed the vital political, religious, and diplomatic interests of the early Abbasid state. But one industrious chronicler of medieval Arab intellectual history preferred another explanation, ascribing al-Mamun’s passion for the work of the House of Wisdom to a mystical dream. According to Ibn al-Nadim, the sleeping caliph spotted a bald, light-skinned Aristotle sitting on his bed. Overcoming his initial shock at finding himself face-to-face with the great philosopher, al-Mamun asked him to define “that which is good.” Aristotle replied that reason and revelation—that is, science and religion—were both good and in the public interest, a response the caliph took as confirmation that scientific scholarship was a religious duty. “The dream,” Ibn al-Nadim concludes, “was one of the most definite reasons for the output of books.”
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Chapter Four

MAPPING THE WORLD

A
L-MAMUN’S GREAT
Abbasid Empire owed much of its enormous vitality to the spiritual and intellectual energies unleashed two hundred years earlier in a remote corner of the Arabian Peninsula. There, in 610, a former caravan driver and small-time merchant began to receive revelations from God during periodic retreats in the nearby mountains. After receiving his initial revelations, Muhammad was troubled and at first told no one, except his beloved wife Khadija. But he was soon commanded by God to make his message public: “O you enveloped in your cloak, arise and warn (Koran, 74:1–2).”
¹

Muhammad’s message of social justice, the need for good works, and the oneness of God attracted some members of Mecca’s elite, such as Khadija, herself a wealthy business owner. And it resonated with members of the lesser Arab tribes and the urban poor in his native city of Mecca. But it also drew the anger of many among Mecca’s powerful merchant class, grown fat on their command of valuable trade routes and their monopoly over lucrative religious tourism to the city’s cube-shaped Kaaba shrine, then a center of traditional idol worship.

In recent decades, the rise of these same wealthy tribes had largely displaced the old order in and around Mecca, reducing the standing and power of Muhammad’s own clan, the Banu Hashim, and others like it. In keeping with the Arab tradition of collective clan responsibility, Mecca’s oligarchs pressured the Banu Hashim elders to rein in Muhammad before he could destabilize the entire economic and social order. His opponents imposed a boycott against anyone who supported the firebrand preacher. Muhammad found himself the subject of taunts, insults, even an assassination attempt. Loudmouthed cynics demanded that he produce a miracle in support of his revelations. In the face of such pressure, recruitment of new followers tailed off sharply. With the death of his uncle Abu Talib, Muhammad lost the protection of the leading voice among the Banu Hashim. Life in Mecca was no longer tenable.

The result was the emigration, called the
bijra
, in 622 of Muhammad and a small band of followers north to the oasis town of Medina, an event that would prove so momentous that it was later taken as the starting point for the Islamic calendar and thus for all of Muslim history. Muhammad had cut a deal with Medina’s fractious Arab tribes, mostly pagans but also several important Jewish clans: He would arbitrate their interminable disputes in exchange for protection for himself and his supporters against the merchants of Mecca. Once Muhammad was secure in this new base, his relationship to the young community of believers around him and the content of his preaching began to change dramatically.

Revelations from the Meccan era, recorded among the 114 chapters of the Koran, are largely in the age-old Near Eastern tradition of spiritual warning. They were revealed to Muhammad over the course of more than two decades and consist of brief messages, generally in rhymed prose, calling on humanity to mend its ways and please the one true God before Judgment Day. For their part, the Holy Book’s Medina sections, longer and more detailed, generally reflect more quotidian concerns. They also provide specific guidelines for ordering the political, social, and economic affairs of Muhammad’s growing number of followers.
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Only now is he portrayed as the messenger of God, the last of the line of divine prophets that includes Abraham, Moses, and Jesus.
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