His luck turned a few years later when, in 999, he received an invitation from the newly restored Prince Qābūs in Gorgan and gladly left Rayy behind. To Qābūs he would dedicate his great historical text The Chronology of Ancient Nations, a book still regarded today as one of the greatest sources of medieval history ever written.
By the early years of the new millennium, with his reputation secure as one of the leading thinkers of his generation, he was lured back to a more peaceful Khwārizm and its capital Gurgānj (known today as Old Urganch, or Kunya Urgench, in Turkmenistan) where the ruling Mamūnid sultans, whose power struggle with the Banū Irāq princes had caused him to flee Kath a few years earlier, were now more welcoming. Crucially, they had renewed their patronage of scholarship and were keen to attract the top scholars to work in their courts. Al-Bīrūni would spend many productive years within a circle of brilliant young minds, including the precocious Ibn Sīna, in an intellectual environment not seen since the glory days of the House of Wisdom in Baghdad nearly two centuries earlier.
Better known by his Latinized name of Avicenna, Abū Ali al-Hussein ibn Abdullah ibn Sīna (980–1037) is the best-known scholar of Islam. Just as the work of Aristotle can be regarded as the climax of ancient Greek philosophical thought, so Ibn Sīna’s work stands as the pinnacle of medieval philosophy. Born near Bukhara, and in contrast with al-Bīrūni, Ibn Sīna enjoyed a privileged upbringing as the son of politically influential parents who were part of the ruling Samanid elite. By an early age, he had memorized the entire Qur’an and much of Persian poetry. One man who played an important role in his early life was his tutor, Abū Abdullah al-Nātili, about whom Ibn Sīna later wrote in typically arrogant style: ‘Al-Nātili was extremely amazed at me; whatever problem he posed for me I conceptualized better than he, so he advised my father against my taking up any profession other than learning.’5 Ibn Sīna also describes how as a teenager he mastered medicine and found it not to be intellectually challenging enough, and so turned to philosophy. He continued to practise medicine, however, and was already treating patients at the tender age of 16. After successfully treating Prince Nūh ibn Mansūr himself he was given as a reward free access to the royal library in Bukhara. It was there that he would complete his education, covering every area of human knowledge. He wrote his first work, dedicated to Prince Nūh, called A Treatise on the Soul in the Manner of a Summary, which is extant in both Arabic and Latin. While more of a student essay than a mature scholarly work, it would nevertheless lay the foundations for much of his philosophical writing later in life.
Thus, around the time al-Bīrūni was struggling miserably to establish himself in Rayy, Ibn Sīna was happily devouring the great texts on medicine and philosophy in Bukhara. But it was not long before their fortunes would be reversed, for, coinciding with al-Bīrūni’s luck suddenly taking a turn for the better when he left for Gorgan, Ibn Sīna was compelled to leave his home city for good. The heightening tensions between the Samanid dynasty and the Ghaznavids to the south forced him to flee north to the relative safety of Gurgānj,6 where he would be joined a few years later by the returning al-Bīrūni. But despite this setback Ibn Sīna’s career soon flourished, and he became a huge celebrity during his lifetime. He never married, and is said to have been a man of striking good looks who enjoyed the company of women and more than the odd glass of wine. He was also arrogant to the point of being scornful of the ‘lesser mortals’ around him.
In contrast, al-Bīrūni, while every bit as self-assured, even arrogant, as Ibn Sīna, had a very different personality. Like Ibn Sīna, he never married or had a family, but he did not seek power or wealth and was single-mindedly devoted to his research. It is said that when, later in life, he dedicated his great work on astronomy and geometry, The Mas’ūdi Canon, to the sultan of the Ghaznavid state, al-Mas’ūd, the sultan rewarded him with an elephant loaded with silver coins. But al-Bīrūni would not accept the gift and sent it back, saying that he had no need for such wealth. This example is not an indication of al-Bīrūni’s humility, but rather of his lack of interest in worldly possessions.
Around the year 1012, with the threat of invasion from the Ghaznavid Empire in the south growing ever greater, Ibn Sīna decided it was time to leave Gurgānj. He set off to seek greater fame and fortune in the royal courts of Persia, evading Ghaznavid capture while searching for a safe haven and the all-important patronage that would enable him to continue his studies. He spent time in Gorgan, where he began writing his great Canon of Medicine and first met his lifelong disciple and biographer, al-Juzjānī; and then in Rayy, where he practised medicine in the royal court and refined many of his philosophical thoughts. Still nervous of the advancing shadow of the Ghaznavids, he moved on, first to Qazwīn, and finally settled in Hamadan in 1015. There he befriended the Buyid Amir Shams al-Dowla, whom he cured of colic, and was soon appointed as his new vizier. Apart from a shaky start in the job when he was briefly imprisoned to appease insurgent soldiers unhappy with his appointment, Ibn Sīna lived life to the full in Hamadan, fulfilling his administrative duties during the day, teaching and writing in the evening and partying through the night.
Ibn Sīna became increasingly outspoken on philosophical matters and his writing betrayed his uncompromising rationalist views and commitment to the supremacy of logic. Although he was a very spiritual man – and much of his philosophy was theological in flavour – he was nevertheless labelled a heretic by the conservative orthodoxy. It did not help that he lived a lifestyle some regarded as hedonistic. However, he refused to moderate his rationalist views and also argued that he preferred a rich and broad yet short life to a narrow, long one.
Al-Bīrūni meanwhile had chosen to sit it out in Gurgānj. But in 1017 the Ghaznavids finally invaded Khwārizm. Their ruler, Sultan Mahmūd, took al-Bīrūni and several other scholars back with him to his capital, Ghazna in modern Afghanistan. Whether al-Bīrūni was taken as a prisoner or went willingly is not clear, but this move did not stop his scholarly output and he soon began one of his most famous works, The Determination of the Coordinates of Cities (Kitab Tahdīd Nihāyāt al-Amākin li-Tashīh Masāfāt al-Masākin), which he completed in the summer of 1025 and which is essentially a textbook on spherical geometry.
By 1031 he had completed his magnum opus, The Mas’ūdi Canon, which he dedicated to the Ghaznavid Sultan Mas’ūd. Then, after years of travel around India, he completed his last great work, The History of India (Ta’rīkh al-Hind), which is to this day an important source of information for modern Indologists.7 For instance, his analysis of the relationship between Islam and Hinduism is a wonderful early study of comparative religions.
Ibn Sīna had to uproot yet again in 1023, this time for political reasons, leaving Hamadan in a hurry for Isfahan, where he would spend the last fifteen years of his life working under the patronage of Sultan Ala’ al-Dowla. At the time, Isfahan was one of the powerhouses of Persian scholarship. A famous saying about this still beautiful city that exemplifies its status and importance a thousand years ago was ‘Isfahān nesf-e jahān’ (‘Isfahan is half the world’).
What of the scientific legacy of these two great men? In the case of the other scientists we have encountered it has been quite clear-cut what their main contributions have been, despite all of them being polymaths: Jābir the chemist, al-Khwārizmi the algebraist, al-Kindi the philosopher, al-Rāzi the clinician, Ibn al-Haytham the physicist; but when describing the achievements of Ibn Sīna and al-Bīrūni, the best I can do is pluck out a few highlights.
As a physician, Ibn Sīna’s fame today is due to his Canon of Medicine, which became the standard medical textbook in both the Islamic world and Europe (where it was even more widely known and used than al-Rāzi’s Liber continens) for the next six hundred years – an extraordinary shelf life for an academic text, particularly as it also supplanted the writings of Galen and Hippocrates, the two giants of Greek medicine. It is remarkable because it synthesized all Greek, Persian and Indian medical knowledge
as well as Ibn Sīna’s own work, such as his discovery and explanation of contagious diseases and a detailed description of the anatomy of the human eye.
One of the volumes of the Canon contains a section on bone fractures, and has aspects of a modern medical textbook in the way it describes causes, types and forms of all kinds of fractures, along with methods of treatment. Ibn Sīna was the first physician, for instance, to advocate what we now know as the theory of delayed splintage, by suggesting that fractures should not be splinted immediately but only after several days. This is still a respected idea in medicine today. He also discussed how to deal with a fracture to the first metacarpal bone in the thumb, which modern textbooks describe as the ‘Bennett’s fracture’ after the man who supposedly ‘discovered’ it in 1882, nearly nine centuries after Ibn Sīna’s description.
However, while the Canon (a name that derives from the Arabic word Qānūn, meaning ‘law’ – which itself comes from the Greek kanōn) is Ibn Sīna’s most famous work, it is not his greatest contribution to science. That accolade without doubt goes to his Kitab al-Shifā’, which is commonly translated as the Book of Healing. But unlike the Canon this was no medical text; the word shifā’ actually means ‘cure’, in the sense that the book was written as a general compendium of knowledge in the hope of curing the world of the disease of ignorance.
In all, al-Shifā’ contained nine volumes on logic and eight on the natural sciences. Other volumes covered arithmetic, geometry, astronomy, music and, of course, metaphysics. It is in a section on psychology, for instance, that we encounter one of Ibn Sīna’s most famous arguments: the ‘floating man’ thought-experiment. With it, Ibn Sīna refutes the moralist belief of earlier Muslim theologians that our physical bodies are all that exists. He does this by describing a scenario that he believed proves the immateriality of the human soul:
Suppose that a man is created all at once, fully developed and perfectly formed but with his vision shrouded from perceiving all external objects – created floating in the air or in space, not buffeted by any perceptible currents of the air that supports him, his limbs separated and kept out of contact from one another, so that they do not feel each other. Then let the subject consider whether he would affirm the existence of his self. There is no doubt that he would affirm his own existence, although not affirming the reality of any of his limbs or inner organs.
Hence the one who affirms has a means to be alerted to the existence of his soul as something other than the body and to his being directly acquainted with this existence and aware of it.8
The extent to which this idea was to influence later thinkers, such as the seventeenth-century early modern philosopher René Descartes, remains a matter of speculation. However, Descartes’s immortal words, Cogito, ergo sum (‘I think, therefore I am’), on the issue of mind/body dualism, run remarkably close to Ibn Sīna’s arguments; and it is well known that others, such as David Hume, built their arguments on the floating man.
More generally, Ibn Sīna attempted to construct an all-encompassing metaphysical model of reality that would allow him to prove the existence of God using logic. Although he studied the work of Aristotle and Plato, he was without doubt the most original philosopher of the medieval world. Modern historians in fact like to divide medieval philosophy into two eras: pre-Ibn Sīna, in which the greatest Islamic philosophers such as al-Kindi, al-Rāzi and al-Farābi essentially modified, extended and criticized Aristotelianism, and post-Ibn Sīna, in which philosophers such as al-Ghazāli and Ibn Rushd modified, extended and criticized what is referred to as Avicennism (the philosophy of Ibn Sīna). I would argue that just as Ibn al-Haytham should be regarded as the world’s greatest physicist in the time span between Archimedes and Newton, so Ibn Sīna was the colossus of philosophy between Aristotle and Descartes. His synthesis of philosophy and Islamic theology would influence later Jewish and Christian scholars such as Maimonides in the twelfth century and Roger Bacon and Thomas Aquinas in the thirteenth.
Ibn Sīna’s harshest critic was the theologian al-Ghazāli (1058–1111), who famously wrote The Incoherence of the Philosophers (Tahāfut al-Falāsifa) as a direct attack on the Aristotelian approach of Ibn Sīna as being anti-Islamic. But this work would not be the last word on the subject, for the Andalusian philosopher Ibn Rushd would write a brilliant defence of Ibn Sīna and Aristotelianism in his stinging rebuttal to al-Ghazāli, which he called The Incoherence of ‘The Incoherence’ (Tahāfut al-Tahāfut).
It is not surprising that Ibn Sīna is a national icon in Iran today, and one can find countless schools and hospitals named after him in many countries around the world. Indeed, his legacy stretches even further, for there is an ‘Avicenna’ crater on the moon, and in 1980 every member country of Unesco celebrated the thousand-year anniversary of Ibn Sīna’s birth. As a philosopher he is referred to as the Aristotle of Islam; as a physician he is known as the Galen of Islam.
Yet al-Bīrūni was the better natural scientist. He adopted a critical stance on Aristotle, arguing that the Greek’s reliance on pure thought and reasoning had often led him to the wrong conclusions. Instead, al-Bīrūni insisted on careful observation and scientific experimentation to test Aristotle’s ideas, and it was this careful empirical approach that led to his many impressive discoveries in physics and astronomy. He was also an exceptional mathematician and developed techniques for solving cubic equations and extracting cube, and higher, roots. He also advanced the field of trigonometry beyond the earlier work of the brilliant Persian mathematician Abū al-Wafā’ (940–98).
An important application of his mathematics was in solving the qibla problem (determining the direction of Mecca), which had to be addressed each time a new mosque was built anywhere in the Islamic Empire. It required knowledge of the accurate coordinates of longitude and latitude of all cities, as well as a mastery of spherical geometry. In these matters, al-Bīrūni was peerless.
In his famous Mas’ūdi Canon, completed around 1031, al-Bīrūni employed mathematical techniques that had never been used before, and developed rudimentary methods in calculus for the first time, which he used to describe the motion and acceleration of heavenly bodies, thereby laying the foundations for Newton’s laws of motion in the Principia Mathematica more than six hundred years later.
Despite having supreme confidence in his own abilities, and his comfortable relationships with the various rulers from whose patronage he benefited, al-Bīrūni was a man who did not like rocking the establishment boat, and he willingly toed the orthodox religious line of his masters. For example, he denounced al-Rāzi for his criticism of religion and even went so far as to claim that the physician’s blindness later in life was divine punishment for his heresy. Whether this was the pronouncement of a rational genius hiding behind the cloak of religious conservatism, or whether al-Bīrūni was simply a more devout Muslim than al-Rāzi (which would not have been difficult), we shall probably never know. Nor was al-Bīrūni a willing politician, but the needs of a life of unrest forced him to become involved in the affairs of state. He famously once wrote of how he was required to mediate in disputes between different rulers: ‘I was compelled to participate in worldly affairs, which excited the envy of fools, but made the wise pity me.’
Another example is his fascinating position on the issue of heliocentrism versus geocentrism. There is no doubt that, in common with the vast majority of Islamic scholars, al-Bīrūni subscribed wholeheartedly to the geocentric model of the universe. He even went so far as to argue about the ordering of the orbits of the sun and planets around the earth. However, a contemporary of his, the Baghdadi astronomer al-Sijzi (c. 950–c. 1020), had proposed a heliocentric universe. Al-Bīrūni was well aware of this work and even collaborated with al-Sijzi, and so, rather than dismiss it out of hand in favour of geocentrism, he was initially neutral on the matter. He famously stated that all astronomical data could be explained just as well by supposing that the earth turns daily on its axis and revolves annually around the sun as by
assuming that it was stationary. So, while al-Bīrūni had philosophical issues with heliocentrism, he was still brilliant enough to appreciate, like Ibn al-Haytham, that one can only accept a scientific theory based on empirical evidence. And since the data could not discriminate between heliocentrism and geocentrism, he was in no position to decide. Indeed, even Copernicus’ much later, and correct, heliocentric model was really no more than a guess. For while it would later be seen to have heralded the birth of modern European science, it came before Galileo pointed his telescope at the sky and before Newton derived his inverse-square law of gravitation (the two ingredients needed to prove Copernicus was correct).9
The position of al-Bīrūni on cosmology can be compared with another much more recent scientific debate, over the correct interpretation of quantum mechanics, the theory of the subatomic world developed in the early decades of the twentieth century. In that case – and this is an issue that has yet to be satisfactorily resolved – the argument was over the physical reality of certain aspects of the microcosm, such as the apparent ability of subatomic particles to be in two places at once. But here, too, no experiment we care to devise has been able to point us to any one of several possible interpretations of what is going on. The Danish physicist and father of quantum mechanics, Niels Bohr (who for some reason reminds me a lot of al-Bīrūni transported in space and time to 1920s Copenhagen), argued that, since experiment cannot resolve the issue, it is a purely metaphysical question and just a matter of philosophical taste. Al-Bīrūni’s attitude towards cosmology would seem to me similar to this modern ‘positivist’ position: if experimental evidence cannot discriminate between two competing theories, they are necessarily equally valid and it is a waste of time worrying about it. In the case of the model of the solar system, the issue would be resolved many centuries after al-Bīrūni. Quantum mechanics is still waiting for its Copernicus, Galileo or Newton. I should add that this idea of positivism has also been attributed to Ibn al-Haytham, who states quite clearly in his Book of Optics that metaphysical speculation is not true knowledge unless it can be supported by empirical proof.
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