During the living centuries of the Arab empire, a series of stellar observatories glittered like jewels throughout the archipelago of its conquests. The observatory played an important role in the religious life of devout Muslims. More so than either Jews or Christians, men of the faith were called upon carefully to mark the schedule of their devotions. Caliphs in Baghdad counted time by means of either a water clock or an hourglass, and yet the Quran commanded five-fold prayers each day, and it commanded the faithful to face the shrine of Kaaba in Mecca as they prayed—tasks requiring some very considerable mental dexterity. “At the last Judgment,” the Turkish devout Said Nursî remarked, “the ink spent by scholars is equal to the blood of martyrs.”

Those scholars celebrated at the last judgment were apt to be scholars of religion and so bound by the inerrancy of the Quran. “Allah turns over the night and the day,” reads a well-known Quranic verse, “most surely there is a lesson in this for those who have sight.” It is hardly surprising that Muslim mathematicians and astronomers, from the late seventh to the early fifteenth century, regarded their curiosity, on those occasions when they were called upon to justify it, as if its indulgence were an exercise calculated to increase their devotion.

But of all the human emotions, curiosity is the one least subject to the general proscription against gluttony, and once engaged, even if engaged initially in the service of religion, it has a tendency to grow relentlessly until in the end the scholar becomes curious about the nature of revelation itself.

Ulugh Beg

Muhammad Taragai Ulugh Beg was born in 1394 and died 55 years later, the victim of an assassination orchestrated by his son. The grandson of the murderous Tamerlane, Ulugh Beg became the ruler of Transoxiana on the death of his father. It was in Samarkand that he created an outstanding astronomical observatory.

A king and an astronomer, Ulugh Beg’s moral nature impressed his contemporaries. He was admired. Writing to his father, a young man by the name of Giyâth al-Din Jamshid al-Kâshi was concerned to establish Ulugh Beg’s reputation as a scientist as well as a ruler. “The King of Islam,” he writes, “the issuer of orders to the seven climes, may God preserve his realm and sovereignty, is a learned person.” There follows an earnest disclaimer. “I do not write this and make these assertions out of politeness.” Various encomia now follow. Ulugh Beg’s knowledge of the Quran is impeccable and wide-ranging. He knows most of the Quran by heart; he recites at least two sections before experts each morning. He makes no mistakes. His knowledge of grammar and syntax is very good, and he writes Arabic very well. Ulugh Beg, Al-Kâshi assures his father, is well-versed in jurisprudence, logic, and the theory of literary styles.

If Ulugh Beg emerges from Al-Kâshi’s letter as a man of parts, as he surely does, it is his scientific stewardship that most elicits Al-Kâshi’s admiration. Beyond his competence, there is his temper: rare in a scientist, unheard of in a king. According to Al-Kâshi, Ulugh Beg was determined to act in his observatory as one scientist among others:

If, in certain cases, there happens to be anything concerning which we, his servants, have some doubt, the point is discussed, and no matter from what side the clarification of the mistake comes, His Majesty will at once accept it without the least hesitation, [for] it is his aim to see that everything is thoroughly investigated, and to have the work at the observatory accomplished in the best possible manner.

Giyâth al-Din Jamshid al-Kâshi died as a young man, his death leaving his colleagues stunned and mournful. When, a few years later, Ulugh Beg composed the introduction to his monumental Zij—the observatory’s astronomical tables—he reflected on his own role in the work of the observatory, and supplied as an aphorism the noble living voice that is missing from Al-Kâshi’s letter. “Our accomplishments indicate what we are; look therefore at the things we have left behind.” He then credited his teachers and masters, “the most learned of the men of learning,” and finally with his own voice now in its proper register, he wrote in tribute to his friend, “the pride of the sagacious people of the world … the unraveler of the intricacies of problems … Giyâth al-Din Jamshid al-Kâshi, may God refresh his resting place.”

The observatory that Ulugh Beg created was conceived on a monumental scale. Muslim astronomers quite understood that celestial phenomena are periodic, with the stars returning roughly to their position after days, months, or years; but they understood experimental error as well, and they knew that careful observations could be defeated by a cloudy night. The observatory at Samarkand was dedicated to a thirty-year program, one longer than anything envisioned, by way of comparison, for the Hubble space telescope. The observatory was grand in its physical aspects. The sextant used to measure the ecliptic had a radius of almost 40m, roughly comparable to the radius of the reflecting telescope at Mt. Palomar. The building was constructed of marble, and it housed exquisite brass and copper instruments. After Ulugh Beg’s death, the observatory was sacked by local rulers, unable to resist its wealth, and by local clerics, unwilling to abide its learning.

By 1449, the observatory was in ruins.

The ancient near east is filled with the debris of centuries. The physical glories of the observatory at Samarkand are incidental. It is the moral instrument created by Ulugh Beg that is compelling, for that instrument, in various copies and clones, survives into the twenty-first century. The most perceptive contemporary scholar of the Islamic observatory, Aydin Sayili, assigns to the institution the power of primogeniture:

The observatory as an organized and specialized institution was born in Islam; [and] it passed on a rather highly developed state to Europe, and this was followed shortly afterwards, by the creation of modern observatories in Europe, in an unbroken process of evolution.

Writing in 1420 or 1430, Ulugh Beg described science in a way that suggests nothing of the martyr’s blood. “Intellects are in agreement,” he wrote, “and minds are in accord as to the excellence of science and the worthiness of scientists.” The benefits conferred are very often matters of self-improvement. “Science sharpens the intellect and strengthens it; it increases sagacity, and augments perspicacity.” Benefits are social as well as personal. Those sciences whose principles are “indisputable and self-evident” have the merit of being “common to people of different religions.”

Is there any reason to think any of this true? It would be nice to think so.

At the beginning of the twelfth century, the Arab archipelago stretched from Cordoba in the west to the border of India in the east. The greatest of the medieval caliphs, Harun al-Rashid, had, in the early ninth century, created the Bayt al-Hikmah (the House of Wisdom); his son, Al-Mamun invested the resources of his empire in its efflorescence, and until Mongol primitives overran Baghdad in the thirteenth century, the Bayt al-Hikmah retained the light of its learning, flickering wherever mathematicians, logicians, translators, goldsmiths, physicists, physicians, astronomers, astrologers, or poets gathered, whether in fly-specked provincial villages, the coffee house, a place of culture, camels neighing irritably on the streets, the men gabbling in Uzbek or in Turkish, or if not there, then in Baghdad, where pleasure boats plied the Tigris and colored lanterns decorated all the stately riverfront mansions. By the eleventh century, the Bayt al-Hikmah had become, like the library at Alexandria, an institution beyond space and time. The most notable physical scientist of the eleventh century, Abu al-Biruni, was born in Uzbekistan. A man of overpowering curiosity, his collected works run to thirteen thousand folio pages, covering mathematics, astronomy, physics, linguistics, and a dozen other subjects. He wrote an extraordinary account of Indian history, the Kitab al-Hind, one in which he observed, with some equanimity, that among Hindus, Muslims were thought low, impure, cunning, grasping, and cruel.

That Allah is omniscient, he remarked with some asperity, does not justify ignorance.

Abu Hamid Muhammad al-Ghazali

The most perceptive of the Arabic philosophers, Abu Hamid Muhammad al-Ghazali, was born in Baghdad in 1058. If his portraits are inauthentic or unverifiable, they are remarkable in that not one of them depicts a man with a merry face. He seems to have emerged from the womb with burning eyes. Obsessed in childhood by the divine, he possessed in adolescence a mature grasp of dogma and doctrine. He was trained in the law and in theology, and was widely considered matchless in debate.

A curious and incomplete kind of elective affinity passes from the Muslim to the Christian world in the high Middle Ages. The beetle-browed Al-Ghazali is a coeval of sorts to Peter Abelard, who was born in 1079 in what is now Brittany. Leaving home at the age of fourteen, he was introduced to eleventh century philosophy and disputation by the philosopher Jean Roscelin. Abelard then wandered the Loire valley, “disputing,” as he says, “like a true peripatetic philosopher, whenever I heard there was keen interest in the art of dialectic.”

He was very widely considered insufferable.

The book that prompted the nerve of theological heresy to commence vibrating Abelard entitled Sic et Non (Yes and No). “There are many seeming contradictions,” Abelard writes, “in the writings of the Church fathers.” The theologian must therefore address the church fathers with what Abelard calls “the full freedom to criticize and with no obligation to accept unquestioningly.”

Bernard of Clairvaux, the largest religious personality of the twelfth century denounced Abelard as a “scrutinizer of majesty and fabricator of heresies.”

Abelard was a logician by profession, and at forty he came to love late in life, the coldness of his craft doing little to calm his boiling blood and nothing whatsoever to improve his better judgment. Long after he had lost his love, along with his manhood, drunkards in all the low Parisian taverns were still banging their tankards on the tabletops and singing the songs that Abelard seems effortlessly to have composed. Not one survives, although some vagrant ditties attributed to Héloïse may still be found in Breton folklore: mon clerc, mon bien cher Abailard.

At some time during the late eleventh century, Al-Ghazali suffered a terrifying spiritual crisis. He became overwhelmed by doubt. Skepticism is today an honorific. Men who believe any number of absurdities are pleased to regard themselves as skeptics and gather unpleasantly in conventions to say that this is so. The late Christopher Hitchens was in this respect masterful. What can be asserted without evidence, he observed sonorously, can be dismissed without evidence. The remark has been promoted to Hitchens’s razor on Wikipedia.1 Hitchens never once considered that Hitchens’s razor might be used to shave itself. “It is just a sentence,” he said amiably when asked.

This is not the kind of skepticism from which Al-Ghazali suffered. His sense of doubt was corrosive; it was annihilating. He could find no reason for belief in the sciences at his command, and he came to distrust his senses. Unable to combat doubt, and unwilling to accept it, Al-Ghazali stood naked in his torments. God put a lock on his tongue. It is a source of regret that the deity is presently not inclined further to distribute locks. His physician, a smooth Baghdad professional, remarked that there could be no way to treat his affliction unless “his heart were eased of its anxiety.”

Al-Ghazali’s most profound skeptical arguments he expressed in a tract entitled the Tahafut al-Falasifa (the Incoherence of the Philosophers). It is a bitter work, and one written before his spiritual crisis. Have the philosophers maintained that the world is the necessary effect of some divine and so necessary cause? Apparently they have. Does God then act as He must or as He would? If He acts as He must, He is not God, and if He acts as He would, He is not necessary. The most famous of Al-Ghazali’s arguments in the Tahafut concerns the relationship between causes and their effects. “The connection between what is habitually believed to be a cause,” Al-Ghazali wrote, “and what is habitually believed to be an effect, is not necessary [emphasis added] according to us.” There is no necessary connection between “the quenching of thirst and drinking, satiety and eating, burning and contact with fire, light and the appearance of the sun, death and decapitation, healing and the drinking of medicine, the purging of the bowels and the using of a purgative, and so on to all that is observable among connected things in medicine, astronomy, arts and crafts.”

Seven centuries later, the suave Scottish philosopher, David Hume, advanced a similar argument. If A causes B, then either something or nothing makes A the cause of B. If something, what is it, and if nothing, why is A the cause of B? That there was something, Hume never doubted; but what it was, he could not say. The “ultimate springs and principles” of nature, he concluded bleakly, “are totally shut up from human curiosity and enquiry.” Hume appealed to custom to explain what he could not directly discern.

[W]e assert that, after the constant conjunction of two objects—heat and flame, for instance, weight and solidity—we are determined by custom alone to expect the one from the appearance of the other.2

This is no very persuasive example of analysis. A is said to cause B when the two always occur together. If A is the cause of B, then A and B cannot occur together; neither A nor B can occur again or could have occurred before. They are what they are; they took place when they did. Far from explaining that A causes B, custom makes reference only to events that are like A and like B. If we are unable to analyze why A caused B, an appeal to similar circumstances is unavailing. Ten drowning men are unlikely to be of support to a man who is drowning.

This Al-Ghazali quite understood. Only some principle of binding necessity makes causation coherent. No such principle seemed evident to him, and no such principle seems evident to us either. Al-Ghazali settled his accounts with the concept of causation by appealing to the whim of God.

Neither Al-Ghazali nor Hume settled their doubts to their own satisfaction. Were those doubts ever real? What would have satisfied either man, if asked to offer an imaginative account of the connection between A and B? There is nonetheless a difference in attitude between Al-Ghazali and Hume. The secret springs that Hume invoked, although they could not be described, he nonetheless thought real. Perhaps there is nothing in nature and so no causal connection between events. Things just happen. Chaos predominates. This is not an idea that Hume entertained; it is very tempting to suppose that Al-Ghazali did.

It is the difference between them.

Taqi al-Din

Lying undisturbed in a locked drawer of the great library at Istanbul is a manuscript entitled the Shahin-Shah-nama (Book of the King of Kings). Its author was a Persian, Ala ad-Din Mansur-Shirazi. Written in verse, Mansur-Shirazi’s poem is in fact a chronicle, describing the reign of Sultan Murad III, the ruler of the Ottoman Turks from 1574 to 1595. The poem itself, Mansur-Shirazi piously notes, was completed on October 28, 1581, the last day of Ramadan. The manuscript, its translator notes, is “richly illustrated and illuminated,” in the ornate Persian tradition—no perspective, the turbaned characters in the illustrations clambering up the folio pages as if they were climbing so many beanstalks. The binding, he adds, is “quite elaborate,” but the penmanship, considered from “the artistic point of view,” is disappointing.

Parts of the poem, comprising 153 folios, are purely formulaic. God is praised, the Prophet thanked. There are various prayers. But the greater part of the poem is historical, and among the events that it records, there is the story of the creation and destruction of the Royal Istanbul Observatory, the successor by 150 years of the observatory at Samarkand.

Mansur-Shirazi begins his poem by discussing the Royal Observatory’s instruments, remarking that “our wise star gazing astronomer” has placed the observatory in Istanbul on such a firm foundation that in the current era—the late sixteenth century—the prestige accorded astronomy is comparable to the prestige once accorded “the science of religion.” It is an odd remark, and one intended to excite apprehension. The preparations undertaken by Taqi al-Din, the director of the observatory, are recounted in some detail: “The required instruments all became ready/They were, with their brass and copper sections, of great perfection.”

A number of verses that follow are given over to hopes that are by turns exuberant and pious. The appearance of a comet during the month of Ramadan in 985 is recounted, its implications discussed. Until this point, the poem reveals nothing of note. Things now change dramatically. Taqi al-Din is summoned to the presence of Sultan Murad III. A strange concourse follows. The Sultan addresses Taqi al-Din as “you witty man of conscientiousness and perfection,” but the flattery, in addition to being obscure, is insincere. “People of learning,” the Sultan remarks—and it is now clear that he means clerics—have made inquiries. They have expressed reservations. And just what has the observatory been doing?

Taqi al-Din answers as almost any physical scientist would, although with a certain purely Ottoman flourish:

In the Zij of Ulugh Beg, there were many doubtful points; now through observation, the tables have been corrected, and out of grief, the heart of the foe has writhed and twisted in its coils.

It is now that history breaks in two. The Sultan issues a shocking order, one that the poem has done nothing to suggest. He summons his Admiral and commands that he should promptly “wreck the observatory, and pull it down from apogee to perigee.”

And it was done: “Nothing remains of the observatory but a name and a memory.”

The reader might well expect the poet to share in his consternation, but far from castigating the acts that he records, he denies his own emotional sentiments, and provides a melancholy justification for the Sultan’s actions:

In the labyrinth of this existence of short duration do not close your eye of circumspection of our greediness and appetite. Do not make decisions concerning the affairs of the firmament.

The justification given is then elaborated in what would appear to be a direct address to men of science:

What hope then can you have of uncovering these matters
That you make diversions from the surface of the earth
And indulge in celestial affairs.
Come, let us get away from this egotism and wrangling
For the old decrepit world is monstrously tricky and deceptive
Beware of her for she may put our affairs in confusion.

This is hardly advice that a partisan of inquiry would wish to hear. It is nonetheless the advice—and the only advice—that Mansur-Shirazi is prepared to offer:

When the affair concerning the Observatory was brought to completion
And it was torn from its foundation and its traces were obliterated
All people of faith prayed for the mighty King
For he had caused the performance of a deed
Which was in accordance with the Law of the True Religion.

The year is 1580. Just five years earlier, Tycho Brahe had laid the foundations of his own observatory at Uraniborg, the enchantment of seeing dying in one culture, even as it was coming to life in another.

For scholarly references see The Secrets of the Vaulted Sky.3

  1. Wikipedia, “Hitchens’s razor.” 
  2. Terence Penelhum, David Hume: An Introduction to His Philosophical System (West Lafayette, IN: Purdue University Press, 1992): 76. 
  3. David Berlinski, The Secrets of the Vaulted Sky (Orlando, FL: Houghton Mifflin Harcourt, 2003).