Encyclopedia of Medieval Philosophy

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al-Bīrūnī, Abū Rayḥān

  • Gotthard StrohmaierEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-94-024-1151-5_86-2


Al-Bīrūnī, Abū Rayḥān Muḥammad ibn Aḥmad was one of the most original minds of the Muslim world, and by the encyclopedic scope of his interests, perhaps of the whole Middle Ages. In contrast to many less important scientists of the Muslim world, he left no impact on Western scholasticism. The titles of his works amount to 148, but only a part of them is still extant. They deal with astronomy and astrology, geography and geodesy, mathematics and calendar reckoning, mechanics, mineralogy and pharmacognosy, and history of religions and culture. Being a committed Muslim, he was at the same time an enthusiastic admirer of the Greek thinkers. His Arabic style is sometimes sarcastic, especially when dealing with Muslim theologians who rejected obvious facts. Remarkable is also a cautious use of experiments, which are not to prove some preconceived ideas but to falsify them. From his native region at the Amu Darya river, he did not travel further westward than to the Caspian Sea, but he had the opportunity, when accompanying military excursions, to become acquainted with the religion and customs of the Hindus, whose beliefs and sciences he censures from the standpoint of both his Muslim conviction and Greek science.

Al-Bīrūnī was born in 973 CE in Kath, a city on the Amu Darya river, the ancient Oxus, then the capital of Khwarezm. Although, as it seems, of humble origin, he was fortunate enough of being educated at the court of the ruling Khwarezm-Shahs, where one of the princes, Abū Naṣr Manṣūr ibn ῾Irāq, a leading mathematician of the time, taught him the elements of geometry and astronomy. Very early in his youth, he began with astronomical observations and the construction of the necessary instruments. Due to political conflicts, he had to settle temporarily in Persia, first Rayy, near modern Teheran, where he had the opportunity to participate in the observations with a large mural sextant. Here in Rayy lived 100 years earlier the great physician and alchemist Abū Bakr al-Rāzī. Al-Bīrūnī compiled a bibliography of his works while not failing to distance himself sharply from his heresies.

Later, he had to settle in Gurgān at the southern coast of the Caspian Sea, where he dedicated to the sultan Qābūs his Chronology. In this book, he discusses the astronomical foundations of calendar reckoning of all the people and religions known to him. It contains a lot of interesting details of cultural history. Remarkable in this context is also his intimate knowledge of the Bible. Back in Khwarezm, he became, as a counselor of the ruling Khwarezm-Shah, involved in the inner politics of the country that was threatened and in the end occupied by the sultan Maḥmūd of Ghazna, who extended his empire from Afghanistan to Persia, Georgia, and the whole Central Asia. Al-Bīrūnī was deported together with other intellectuals to Maḥmūd’s residence in Ghazna, present-day Ghazni. Here he could continue his astronomical observations. For a woman named Rayḥāna who hailed also from Khwarezm, he wrote an Introduction into the Art of Astrology in the form of questions and answers. From a mountain that offered a far-reaching sight over the Indus plain, he measured the circumference of the earth with a method that was already used by the Caliph al-Maʾmūn (r. 813–833). Either willingly or unwillingly, he accompanied the repeated military incursions into Punjab, where Maḥmūd pillaged the temples and took rich booty of gold and slaves. The fruit of al-Bīrūnī’s observations is a great monograph on the Hindus, their language, literature, religion, and customs. He finds most of this bizarre and the state of their astronomy below the standard of Greek science. He even learnt Sanskrit and tried, with the help of indigenous assistants, to translate some basic mathematical and astronomical texts into this language for the benefit of Hindu colleagues who were, though, unwilling to learn something new. With Maḥmūd’s son and successor Masʿūd, he was, as it seems, on friendly terms as he dedicated to him a huge astronomical handbook which bears therefore the title The Masʿūdic Canon. A description of precious stones and metals, written in a more entertaining style and nowadays called The Mineralogy, was dedicated to Masʿūd’s successor al-Mawdūd. In an earlier tract, he had determined with a specially designed vessel the specific weight of 18 such substances. The last big work is a pharmacognosy, a list of 1,116 articles, where he equates about 4,500 names in 27 languages of plants and mineral substances used in therapy and diet. The arid philological subject appears sometimes enriched with interesting anecdotes. He left it partly unfinished when he died in 1048 CE in Ghazna.

Al-Bīrūnī was one of those enlightened intellectuals in the Muslim world, who were firm adherents of the Greek scientific heritage that came down to them via the Alexandrian school of late antiquity and the indefatigable activities of the Syrian and Arab translators working in ninth-century Baghdad. In a sarcastic style, he censures often those people who did not share his belief in the primacy of the Greeks. Typical for a medieval intellectual, in general, are derogatory remarks on his mother tongue, the now extinct Khwarezmian. He praises instead the Arabic language that he had to learn later in life as the only suitable medium for the cultivation of the sciences. Sometimes, he stands out by a new and daring approach to geodetic and astronomical problems. While celestial globes with the pictures of the Greek constellations were widely in use, he was the first to construct a terrestrial globe, that is, a model of the Northern Hemisphere with a diameter of 5 m where he could combine the geographical latitudes and longitudes of the cities with their distances in miles as reported by travelers. While being in Kath, he determined in collaboration with a colleague in Baghdad the longitudinal difference between the two cities. This was possible by a lunar eclipse, which was to be observed at different times of the day in both places, in Kath 1 h earlier, what corresponded to 15°. In a special treatise on the various types of the astrolabe, he mentions one which was constructed on the conception that the sphere of the fixed stars rests immobile while the earth is rotating on its place in the center. He adds that this would not be impossible on mathematical grounds, but he sees difficulties in bringing this in accord with the physical realities. Occasionally, he made a cautious use of experiments, but not to prove some preconceived ideas, as was often the case in Greek science and later on, but to falsify them when showing that the observed facts did not tally with them.

In a correspondence with his younger colleague Avicenna, he shows certain dissatisfaction with Aristotle’s natural philosophy, while the latter feels obliged to defend the great master. Al-Bīrūnī touches on a variety of questions: When the heavy elements earth and water gather around the center of the universe and the water is less heavy, why does it not cover the earth equally from all sides? Air and fire are, according to Aristotle, absolutely light, while air is less light. Here al-Bīrūnī puts forward the alternative that both may possess also heaviness and that the air, while being heavier, presses the sphere of fire against that of the moon. We all know that the cold lets bodies contract, while warmth causes them to expand. But why do glass vessels shatter when water contained therein freezes? And why does ice swim on the water despite its solid “earthy” nature? When water evaporates, does it really become air or are its particles only scattered in the air? This leads to the question of the existence of a vacuum, what both try to solve with the help of experiments. Al-Bīrūnī thinks that a vacuum in the air is necessary when one assumes a corpuscular nature of light. Al-Bīrūnī defends not only a physical but also a mathematical atomism, arguing that otherwise one side of a square and the diagonal would be of equal length, as both consist of the same, that is, an infinite number of parts.

In the correspondence, he articulates also his Muslim faith. He doubts the eternity of the world and defends the creationism of the Alexandrian Christian thinker John Philoponus, whom Avicenna on the other hand treats as a hypocrite. Al-Bīrūnī contradicts even the opinion that our cosmos should be the only exemplar of its kind and accuses Avicenna, who follows Aristotle in this respect, of trying to limit God’s omnipotence. It may be that his skepticism toward these basic tenets of the Aristotelian and Neoplatonic mainstream as prevalent in Arabic philosophy has earned him the nickname al-Bīrūnī, which sounds like the so-called nisba, which was usually given to a person after his birthplace. But a place called Bīrūn or Bērūn cannot easily be determined. The Bīrūniyyūn were in Arabic transcription the philosophical sect of the Pyrrhonists, whose radical skepticism was known through doxographies or occasional remarks of Galen of Pergamum.

He shows his truly scientific outlook when dealing with the reports about wondrous and unexplained phenomena, as, for example, Saint Elmo’s fire on high sea or strange therapeutic methods of the Indians or the fire that appears at Easter in the Church of the Holy Sepulchre in Jerusalem. He refrains from rash statements and leaves the question open until more evidence may be found. On the other hand, he is nevertheless, seen in the context of his time, an outstanding representative of historical criticism when he analyses, for example, the tendentiousness of the legends told by the Persians about Alexander the Great.

Due to the wideness of his interests, it proves to be difficult to appreciate equally all his various achievements. The last monograph by Pavel G. Bulgakov about his life and works appeared in 1972 in Russian and was not translated into any other language.



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© Springer Nature B.V. 2018

Authors and Affiliations

  1. 1.Freie Universität BerlinBerlinGermany