Philosophy of science and medicine series – VI: Islamic science

Philip R. Liebson
Rush University, Chicago, Illinois, United States


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Al Hazen
Ibn Sina (Avicenna)


The new science of the twelfth century was Arab in form but founded by the ancient Greeks. The Arabs preserved and transmitted a large body of Greek learning, and what content they added was perhaps less important than their change to the concept of why science ought to be studied. The term “Arab science or medicine” is used primarily for convenience, but Near Eastern might be more accurate since the advances were made not only by Arabs or Persians, but also by people living in North Africa, in Spain and Sicily, and even in Southern and Southwestern Europe.

The Arabs acquired their knowledge of Greek from two sources. One was the Greek settlement in the Byzantine Empire, the other the Nestorian Christians of Eastern Persia. During the sixth and seventh centuries the Nestorians translated most of the works of Greek science into Syriac, which since the third century had replaced Greek as the literary language of western Asia. Gradually, as trading relations between the West and Islam revived, the learning amassed by the Arabs began to penetrate into the West.

Beginning in Baghdad with Al Mansur (714-775), the second Abbasid Caliph, successive rulers patronized learning and collected Greek manuscripts that after the closing of the Greek schools by Justinian in 529 had become scattered abroad. At first Arab science was imported, but in the next three centuries it took on characteristics of its own.

During the reign of al-Mansur, Islamic literature and scholarship emerged in full force, supported by the Abbasid promotion of scholarly research and best exemplified by the Abbasid-sponsored Translation Movement. During that reign a committee made up mostly of Syriac-speaking Christians was set up in Baghdad with the purpose of translating extant Greek works into Arabic. Later Al-Ma’mun, born in Baghdad and reigning as the seventh Abbasid Caliph from 813-833, conducted two astronomical operations intended to determine the value of a terrestrial degree. The crater Almanon on the moon is named in recognition of his contributions to astronomy. Alchemy developed greatly under his patronage; and although he was unsuccessful in transmuting base metals to gold, his methods greatly led to the development of pharmaceutical compounds.

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University Library of Istanbul. The Earth the Center of the Universe.

It was under al-Mam’un that Aristotle was first translated into Arabic from the Greek, as were works on mathematics, astronomy, medicine, and philosophy. In Baghdad he founded a kind of academy called “the House of Wisdom”. Endowed with a library and an observatory, it was a major intellectual center during the Islamic Golden Age. Though first founded under the father of al-Mam’un, it culminated under his own reign and he is credited with its formal institution. He brought many well-known scholars to share information, ideas, and culture into the House of Wisdom, which flourished in Baghdad between  the ninth and the thirteenth century, and where besides Muslims even Jews and Christians were allowed to study. In addition to translating books into Arabic and preserving them, scholars associated with the House of Wisdom also made many remarkable original contributions to diverse fields. Astronomical observatories were set up during the reign of al Ma’mun, and the House was an unrivaled center for the study of humanities and for sciences such as mathematics, astronomy, medicine, alchemy and chemistry, zoology, geography, and cartography. Drawing on Greek, Indian, and Persian texts, the scholars accumulated a great collection of world knowledge, and added to it their own discoveries. By the middle of the ninth century, the House of Wisdom had the largest selection of books in the world.

Al Ma’mum was a pioneer of cartography and commissioned a world map from a large group of astronomers and geographers. The map shows large parts of the Eurasian and African continents with recognizable coastlines and major seas based on the experience of Arab captains sailing and trading over vast distances. The map is presently in an encyclopedia in the Topkapi Sarai museum in Istanbul.

The chief centers from which the knowledge of Arabic and ultimately Greek science spread were Sicily and Spain. Toledo became the Spanish center of transmission from Arabic to Latin in the middle of the twelfth century. Ptolemaic astronomy and its associated trigonometry were also transmitted. The authors, however, added nothing of note to the principles on which the astronomical system of Ptolemy had been founded. But observational instruments were improved and increasingly accurate tables were constructed for astronomic and nautical purposes.  The most noted of these was prepared in Spain, which had been a center of astronomical observation. The meridian of Toledo was for a long time the standard of computation for the West.

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Islamic Astronomical Notations

The original Arabic contribution was important in the study of optics and perspective. Al Kindi and al Hazen made large advances in what had been known by the Greeks.

Al Kindi (c.801-c.873), known as “the Philosopher of the Arabs”, lived in Baghdad and was a philosopher, mathematician, and physician who promoted Hellenistic philosophy by overseeing the translation of Greek scientific and philosophical texts into Arabic . Associated prominently with the Baghdad Wisdom, he wrote many  treatises on metaphysics, ethics, logic, psychology and medicine, pharmacology, mathematics, astronomy, astrology and optics, as well as perfumes, swords, jewels, glass, dyes, zoology, tides, mirrors, meteorology, and earthquakes. He played an important role in mathematics by introducing the Indian numerals to the Islamic and Christian world. He was a pioneer in cryptanalysis; devised several new methods of breaking ciphers; and using his mathematical and medical expertise developed a scale to allow doctors  quantify the potency of their medication.

Al Kindi

Al Hazen (c.965-c.1040) was born in Basra, Mesopotamia, but lived in Cairo under the Fatimid Caliphate. A scientist, mathematician, astronomer, and philosopher, he  made significant contributions to optics, astronomy, mathematics, meteorology, visual perception, and the scientific method. He discussed spherical and parabolic mirrors, lenses and vision. He gave a detailed account of the human eye, and was the first to explain that vision occurs when light bounces on an object and then is directed to the eyes. He attempted to explain the apparent change of the sun and moon when approaching the horizon. Al Hazen is considered to be one of the first theoretical physicists, and an early proponent of the concept that a hypothesis must be proven by experiments based on confirmable procedures or mathematical evidence—hence understanding the scientific method 200 years before Renaissance scientists. In medieval Europe, he was honored as the “Second Ptolemy” or “The Physicist”.

In mathematics the Arabs transmitted valuable knowledge not ever available to the Greeks by making more widely known Indian mathematical concepys. Indian mathematicians had developed a system of numerals in which the value of a digit was shown by its position. They provided the use of “0”, could extract square and cube roots; understood fractions; and worked with geometric series. They also developed solutions of determinate and indeterminate equations of the first and second degree, permutations and combinations, and other operations of arithmetic and algebra. They had also developed trigonomic techniques for expressing the motion of stars and introduced sine tables similar to the ones introduced by Hipparchus (cf Essay IV). The most important mathematical concept transmitted by the Arabs from the Indians was their system of numerals. The adoption of this system in the West was one of the most important advances in European science, for a functional number system was now available for theoretical work. This system had a great advantage over the bulky Roman system of numerals.

The most influential mathematician was al Karismi [al Khwarizmi] (c.780-c.850), a Persian mathematician, geographer, and astronomer who worked in the House of Wisdom. He gave a complete account of the Indian number system, exemplifying the general trend toward what was most useful and practical. He himself said that he limited his work to what was easiest and most useful in arithmetic. In his work he discussed arithmetic progressions, quadratic equations, areas of triangles, quadrilaterals, and circles. He is said to have asserted the impossibility of finding two cubes whose sum would be one cube. In his discussion of five types of quadratic equations, he only accepted real positive roots, but unlike the Greeks recognized the existence of multiple roots. His  Compendious Book on Calculation by Completion and Balancing presented the first systematic solution of linear and quadratic equations in Arabic. He is often considered one of the fathers of algebra. “Algebra” is derived from al jabr, one of the two operations he used to solve quadratic equations. The term algorithm stems from the Latin form of his name. He revised Ptolemy’s Geography and wrote on astronomy and astrology.

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Statue of al-Khwarizma

The Arabs made their most important and original contribution to alchemy, astrology, and magic, partly due their approach to nature. They did not inquire into most vividly illustrated the moral purposes of the Deity, as European symbolists did, nor were they concerned with rational explanations of facts observed in everyday experience. They were more interested in knowledge that would give them more power over nature. They wanted to find the Elixir of Life, the Philosopher’s Stone, and the magical properties of plants and minerals, and the answer to many of their questions was alchemy. It was partly a desire to share the rumored magical power of alchemy that sent the first translators on their journeys from the West to Toledo and Sicily. No sharp distinction was drawn between the natural and the occult, for physical and occult causes were recognized as equally responsible for physical phenomena. This point of view is found in the works of al Kindi (see above). In his works on stellar rays and on the theory of magic art, he argued that the stars and terrestrial objects, and also the human mind through the potency of words suitably uttered, exerted influence by means of rays whose ultimate source was celestial harmony. The effect of the rays was supposed to vary with the configurations of the stars.

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Arab Alchemy Symbols

An important body of transmission was work on medicine, to which some valuable material was added. Most of the information was derived from Hippocrates and Galen and became enshrined in various Arabic encyclopedias, but the Arabs were able to add medical accounts of many mineral substances and substances from plants. The physicians of the emerging Islamic society were familiar with the classical medical traditions already at the times of the Umayyads (7th-8th centuries), especially from Alexandria. An important source from the second half of the 8th century is a “Book of Poisons”. It mentions the Persian names of some drugs and medical plants.

Medical contributions made by medieval Islam included the use of plants as remedy or medicine. Medieval Islamic physicians used natural substances as a source of medicinal drugs—including poppy, Cannabis sativa Linnaeus, and hemp. Hemp was introduced into the Islamic countries in the ninth century from India through Persia and Greek culture and medical literature. The pain-killing uses of opium had been known since ancient times; other drugs such as henbane, hemlock, soporific black nightshade, and lettuce seeds were also used by Islamic physicians to treat pain. Some of these drugs, especially opium, were known to cause drowsiness, and some modern scholars have argued that these drugs were used to cause a person to lose consciousness before an operation, as a modern-day anesthetic would. However, there is no clear reference to such a use before the 16th century.

Original diagnoses and observations were recorded of smallpox and measles.  Ophthalmology was the most successful branch of medicine researched of the time, with the works of ibn al Hazen [al Haytham] (965-1040) remaining an authority until early modern times. Ibn al Hazen took a straight forward approach on vision by explaining that the eye was an optical instrument. The description on the anatomy of the eye led him to form the basis for his theory of image formation, explained by the refraction of light rays passing between two media of different densities. He developed this new theory on vision from experimental investigations.

Ahmad ibn Abi al Ash’ath observed the physiology of the stomach in a live lion in 959. This description preceded William Beaumont by almost 900 years, making Ahmad ibn al-Ash’ath the first person to initiate experimental events in gastric physiology.[

Concepts were integrated from Greek, Roman, Persian, and Indian traditions. In the seventh through the at least the fourteenth centuries, Islamic medicine was the most advanced in the world. Complex literature was developed with textbooks on the principles and practice of medicine. The Academy of Gondishapur, Persia, was an important center of medical education, offering training in philosophy, theology, and science. It was considered by some in the West the most important medical center of the ancient world during the sixth and seventh centuries. Again the Academy of Gondishapur played an important role, guiding the transmission of Persian medical knowledge to the Arab physicians. Founded, in the third century, the academy connected the ancient Greek and Indian medical traditions. Arab physicians trained in Gondishapur may have established contacts with early Islamic medicine. Ophthalmology and pharmacology were some of the important subjects taught.

Many hospitals were developed during the early Islamic era. They were called bimarstan, the Persian words meaning “house of the sick.” The bimaristan had a staff of salaried physicians and a well-equipped dispensary. It treated the blind, lepers and other disabled people, and also separated patients with leprosy from the rest of the ill. The first true Islamic hospital was built in Baghdad. Men and women were admitted to separate but equally equipped wards. The separate wards were further divided into mental disease, contagious disease, non-contagious disease, surgery, medicine, and eye disease. Each hospital contained a lecture hall, kitchen, pharmacy, library, mosque, and occasionally a chapel for Christian patients. The hospital was not merely a place to treat patients: it also served as a medical school to educate and train students. Islamic hospitals were the first to keep written records of patients and their medical treatment. The birth of pharmacy as an independent, well-defined profession was established in the early ninth century by Muslim scholars.

Rhazes  (854-925), Muhammad ibn Zakariyyā al-Rāzī, was a Persian physician, alchemist, philosopher, and important figure in the history of medicine. He was one of the most versatile scientists of the Islamic Golden Age. He is most famous for his medical works, but he also wrote botanical and zoological works, as well as books on physics and mathematics. Many of his books were translated into Latin, and he remained one of the undisputed authorities in European medicine well into the seventeenth century.

A comprehensive thinker, Rhazes made fundamental and enduring contributions, observations and discoveries, which he recorded in more than 200 manuscripts. An early proponent of experimental medicine, he became a successful doctor and served as chief physician of the Baghdad and Rey hospitals. As a teacher of medicine, he attracted students of all backgrounds and interests and was said to be compassionate and devoted to the service of his patients, whether rich or poor.

He was among the first of the Islamic physicians to use humorism, the theory that an excess or deficiency of any of four distinct bodily fluids (humors) in a person directly influenced their temperament and health. To distinguish one contagious disease from another he wrote a pioneering book about smallpox and measles providing clinical characterization of the diseases. He also discovered many compounds and chemicals, such as alcohol and kerosene. Through translation, his medical works and ideas became known among medieval European practitioners and profoundly influenced medical education in the Latin West. Some volumes of his work al Mansuri, namely “On Surgery” and “A General Book on Therapy”, became part of the medical curriculum in Western universities. Rhazes is the first Arab-writing physician who made thorough use of Hippocrates’s writings to set up his own medical system.

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Folio from the “Liber continens” by Rhazes

In medical theory, Rhazes relied mainly on Galen, but his particular attention to the individual case, stressing that each patient must be treated individually, and his emphasis on hygiene and diet reflect the ideas and concepts of the empirical Hippocratic school. Rhazes considered the influence of climate and of the season on health and well-being, taking care that there was always clean air and an appropriate temperature in the patients’ rooms, and recognizing the value of prevention as well as the need for a careful diagnosis and prognosis. The Comprehensive book of medicine, Continens Liber, The Virtuous Life) was one of Rhazes’ largest works, a collection of medical notes that he made throughout his life in the form of extracts from his reading and observations from his own medical experience. In its published form, it consists of twenty-three volumes. Rhazes cites Greek, Syrian, Indian and earlier Arabic works, and also includes medical cases from his own experience. He refers to everything important for a physician to maintain health and treat illness with medications and diet. He describes the signs of illness and does not omit anything which would be necessary for anyone who wants to learn the art of healing In his description of every illness, their causes, symptoms and treatment he describes everything which is known to all ancient and modern physicians since Hippocrates and Galen up to his time and all those who lived in-between. Another work contains a comprehensive encyclopedia of medicine dedicated to medical theory and deals with anatomy, physiology and pathology, materia medica, health issues, dietetics, surgery, toxicology and fever. Another work covers the treatments and cures of diseases and ailments, through dieting.

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Part of a text by Rhazes Avicenna (980-1037)

Ibn Sina, more commonly known in west as Avicenna, was a Persian polymath and physician of the tenth and eleventh centuries known for his scientific works but especially for his writing on medicine. He has been described as the “Father of Early Modern Medicine”. He recognized the potential of airborne transmission of disease, providing insight into many psychiatric conditions, recommending the use of forceps in deliveries complicated by fetal distress, distinguishing central from peripheral facial paralysis, and describing guinea worm infection and trigeminal neuralgia. Avicenna’s medicine became the representative of Islamic medicine mainly through the influence of his famous work, The Canon of Medicine. The book is a compendium of medical principles, individual drugs, organ-specific diseases, preventive health measures, and descriptions of compound medicines. The Canon was highly influential in medical schools.

Ibn al-Nafis, a thirteenth-century Syrian physician, found the previous statement on blood flow from the right ventricle to the left to be false. Ibn al-Nafis discovered that the ventricular septum was impenetrable, lacking any type of invisible passages, showing Galen’s assumptions to be false. Ibn al-Nafis discovered that the blood in the right ventricle of the heart was instead carried to the left by way of the lungs. This discovery was one of the first descriptions of the pulmonary circulation, although his writings on the subject were only rediscovered in the twentieth century, and it was William Harvey’s later independent discovery which brought it to general attention

Physicians like Rhazes wrote about the importance of morality in medicine. Together with Avicenna and ibn al-Nafis they presented the first concept of ethics in Islamic medicine. The contributions of the two major Muslim philosophers and physicians, Rhazes and Avicenna, provided a lasting impact on Muslim medicine. Their compilation of knowledge into medical books had a major influence on the education and spread of medical knowledge in Islamic culture.



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PHILIP R. LIEBSON, MD, graduated from Columbia University and the State University of New York Downstate Medical Center. He received his cardiology training at Bellevue Hospital, New York and the New York Hospital Cornell Medical Center, where he also served as faculty for several years. A professor of medicine and preventive medicine, he has been on the faculty of Rush Medical College and Rush University Medical Center since 1972 and holds the McMullan-Eybel Chair of Excellence in Clinical Cardiology.