The House of Wisdom (34 page)

It was not long before the critique of Greek astronomy spread from the realm of science to that of natural philosophy. Avicenna took note of Ptolemy’s theoretical shortcomings, as did Averroes and Maimonides. These latter philosophers, along with Averroes’s mentor Ibn Tufayl and others, were part of a sustained critical tradition centered in al-Andalus that sought to replace the model of the
Almagest
with a nest of hollow spheres all centered on the earth.
³³
The effort failed—although Avicenna hinted that he had found a separate way to save the model by eliminating the offending equant point, a claim that even his most loyal student dismissed
³⁴
—but it nonetheless reveals the extent to which the Arabs were demanding that science not only account for observed phenomena but also accord with its own understanding of reality. In other words, science had to be both predictive and consistent, central tenets of the modern scientific method. “The science of astronomy of our time contains nothing existent, rather the astronomy of our time conforms only to computation and not to existence,” complains Averroes.
³⁵

Astronomers connected with an observatory at Maragha, in what is today northwest Iran, produced a number of significant breakthroughs to address the deficiencies found in classical astronomy. This research center was built in 1259 on the orders of Genghis Khan’s grandson, Hulegu, who one year earlier had led the Mongol forces in the sack of Baghdad and the execution of the last of the Abbasid caliphs. Baghdad’s authority had long since been whittled down from its once-great expanse, and the caliphs, whose religious significance remained important, had been reduced to little more than political figureheads by the Mamluk warlords who had once served them. But the end of empire did not extinguish the scientific traditions once animated by the early Abbasids. As with the diffusion of scholarly learning into scattered Muslim courts after the collapse of central rule in al-Andalus, so, too, did other centers in the East exhibit remarkable intellectual activity after the loss of Baghdad. These included Diyarbakir, in southeast Turkey, as well as Isfahan, Damascus, and Cairo.
³⁶
Such was the case at Maragha, which brought together an extraordinary collection of astronomers, engineers, and other experts and included a state-of-the-art science library.

Nasir al-Din Tusi, now the observatory’s director and scientific adviser to Hulegu, had already devised an ingenious approach to the problem of the equant, one that generated linear motion from the uniform rotations, in opposite directions, of two spheres. Modern scholars have dubbed this the Tusi Couple. Not only did this address a major shortcoming within Ptolemaic astronomy, but it also helped later Arab scientists, as well as later Western ones, mount serious challenges to the authority of Aristotelian physics.
³⁷
Meanwhile, Tusi’s assistant and the designer of the observatory’s specialized instruments solved the same problem in a different manner. Over time, the theorems developed by Tusi and his colleague were introduced into a range of planetary models by the Arab astronomers, most elegantly by the official timekeeper at the Umayyad mosque in Damascus, Ibn al-Shatir, who used them to account for the movements of the moon, the so-called upper planets, and the lower planet, Mercury.

Ibn al-Shatir died in 1375, but 168 years later his use of the theorems of the Maragha astronomers turns up in the groundbreaking work of Copernicus, suggesting that the Polish astronomer must have been familiar with the work of his Arab predecessors.
³⁸
No means of direct transmission has yet been established, and there is no evidence that Copernicus knew Arabic or that these theorems were ever published in Latin. There are only hints: From 1496 to 1503, he studied in Italy, where Arab science and philosophy avoided the backlash experienced in Paris; there were in his day a number of Western Arabists capable of explaining such advanced works to Latin scientists; and Copernicus, who had studied Greek, may also have had access to late Byzantine borrowings from Arab astronomy. Adding to the mystery, Tusi’s proof of his couple, made around 1260, and the proof included by Copernicus in his
De Revolutionibus
three centuries later use identical designations for the same geometric points, an indication to modern scholars that Copernicus had firsthand access to Tusi’s work.
³⁹

Neither Ibn al-Shatir nor Tusi ever suggested anything as radical as transposing the Ptolemaic model to place its center at or near the sun, the defining feature of what became known as the Copernican revolution, although some Greek and Arab scholars had already pondered the idea. The enormous obstacles facing any theory of a sun-centered universe—established religious teaching and philosophical tradition, common sense and daily human experience, and the lack of a gravitational theory to make the whole thing work—testify to the genius of Copernicus’s insight and to the brilliance of the Western men of science who later perfected his work. Yet it is worth nothing that Ibn al-Shatir had already imposed uniform circular motion on Ptolemy in such a way that all planetary movements now revolved around a single point, the earth. This made Copernicus’s conceptual breakthrough that much easier by allowing him to shift that center toward the sun without having to reinvent an entire model of the heavens from scratch.
⁴⁰

The scientific, philosophical, and theological struggles over Copernicus’s proposal of a heliocentric universe, which was buried in his famously difficult treatise under a mountain of complex mathematics, continued for many years.
⁴¹
The birth pangs of the new world of independent science included Galileo’s heresy conviction in 1633 for his support of Copernicus, the earlier burning at the stake of the freethinking philosopher Giordano Bruno, and the persecution of countless others by the Catholic Church, at disastrous and lasting cost to its reputation and authority.

Nonetheless, the fearsome inquisitors never managed to put the jinn of Arab science back in the bottle. The findings of Johannes Kepler on elliptical planetary orbits and Isaac Newton’s later theory of gravitation, published in 1687, effectively completed the work of Copernicus and helped guarantee the success of the scientific revolution. The church was forced to abide by the verdict of natural philosophy, its former handmaiden, and accept that the earth in fact revolved around the sun. Galileo was eventually rehabilitated, and in 1979 Pope John Paul II expressed regret for the mistreatment of the great Italian scientist and inventor at the hands of the church.

The verdict of history on this entire episode has been harsh, and rightly so. This is all the more the case because the church willfully ignored the prescriptions of its own St. Thomas—and through him those of Averroes—for the peaceful and productive coexistence of faith and reason. Under the direct influence of the Arab Aristotelians, Thomas had carved out a truce between traditional church teachings and the discoveries of the emerging generations of modern Western scientists. That compromise defines the rules of engagement to this day between the realms of faith and reason. And it stakes the Arabs’ claim as inventors of the West, a debt that Adelard of Bath identified many centuries ago on his return from Antioch: “Of course God rules the universe,” he assures his readers. “But we may and should enquire into the natural world. The Arabs teach us that.”
⁴²

NOTE TO READERS

D
EFINITIONS OF TERMS
and concepts are rarely associated with works for the general reader, no matter how serious or weighty the subject, and I have deliberately kept these to a minimum. Nonetheless, a few words are in order at the outset about my choice of “Arab science”—or words to that effect—to convey the complex cultural milieu of the medieval Islamic world, rather than “Islamic science.” As many readers will already be aware, much of the cultural flowering in this time and place was not exclusively the work of ethnic Arabs. Nor was it strictly the work of Muslims. Persians—including Zoroastrians and Christians—Jews, Greeks, Syriac Christians, Turks, Kurds, and others played crucial roles in all aspects of science, theology, and philosophy.

However, this work was almost always conducted in Arabic and frequently under the aegis of Arab rulers, most notably the Umayyad and Abbasid caliphs, first in Damascus and then in Baghdad. In one notable case, as we shall see, an ethnic Persian scholar produced a major work in his native language but then rewrote it in Arabic, which he found far more precise and more effective for his purposes. Throughout much of the period in question, Arabic served as the global language of scholarship, and learned men of all stripes could travel widely and hold serious and nuanced discussions in this lingua franca. Medieval Western scholars who wanted access to the latest findings also needed to master the Arabic tongue, or work from translations by those who had done so. It is also worth noting that such labels, today largely associated with nation-states and the demands for distinct cultural identity, were far more fluid in the era under discussion.

This is not to say that Islam and the unique culture of the Muslims are not important elements of our story. I refer to the great importance of Islam to the development of Arab science throughout the text and have devoted an entire chapter to this vital relationship between faith and reason. Yet much of the research during this period went well beyond specific questions relating to the Islamic faith and was not generally carried out with an eye to establishing theological or doctrinal truths. At the same time, it is worth avoiding any confusion with the established notion of the “Islamic sciences,” which generally refers to strictly religious disciplines: jurisprudence, Koranic exegesis, the study of the hadith, or the collected sayings of the Prophet Muhammad, and so on.

A few words on my use of names and dates and my system of transliteration will also be useful. This work presents the enormous impact of Arab learning on the West—that is, on the lands of medieval Christendom and the states and societies they later produced. It seemed only sensible to use the Latinized forms instead of the Arabic names in the case of figures widely known to the Western world. Thus, I have used the Latin Averroes, not the Arabic Ibn Rushd, and Avicenna, not Ibn Sina. Less familiar figures have retained their Arabic names. For similar reasons, dates are presented in the traditional “Western” fashion—that is, anno Domini (
A.D
.) and before Christ (
B.C
.) In transliterating, I have chosen readability, familiarity, and convention over linguistic purity or consistency.

Finally, a reference to the structure of
The House of Wisdom
, which pays tribute to the success of Arab scholars in measuring out the ever-changing pattern of night and day that determines the times of the five daily Muslim prayers. The book begins at sunset (
al~maghrib
prayer), the traditional start of the day in the Middle East; then moves through the nightfall (
al~isha
) of the Christian Middle Ages; recounts the dawn (
al~fajr
) of the great age of Arab learning; soars toward the glory of midday (
al~zuhr
) with our central hero, Adelard of Bath, in the Near East; and concludes with the rich colors of afternoon (
al~asr
) that mark the end of the Age of Faith in the West and the seemingly unstoppable triumph of Reason.

SIGNIFICANT EVENTS

These are some of the most important events surrounding the story of
The House of Wisdom
. By necessity, several of the dates are only approximate. More details can be found in the narrative that follows.