Abū ʿAbd Allāh Muḥammad ibn Muʿādh al-Jayyānī (989, Cordova, Al-Andalus – 1079, Jaén, Al-Andalus) was a mathematician, Islamic scholar, and Qadi from Al-Andalus (in present-day Spain). Al-Jayyānī wrote important commentaries on Euclid‘s Elements and he wrote the first known treatise on spherical trigonometry as a discipline independent from astronomy.
Little is known about his life. Confusion exists over the identity of al-Jayyānī of the same name mentioned by ibn Bashkuwal (died 1183), Qur’anic scholar, Arabic Philologist, and expert in inheritance laws (farāʾiḍī). It is unknown whether they are the same person.
The book of unknown arcs of a sphere
Al-Jayyānī wrote The book of unknown arcs of a sphere, which is considered “the first treatise on spherical trigonometry” in its modern form, although spherical trigonometry in its ancient Hellenistic form was dealt with by earlier mathematicians such as Menelaus of Alexandria, who developed Menelaus’ theorem to deal with spherical problems. However, E. S. Kennedy points out that while it was possible in pre-lslamic mathematics to compute the magnitudes of a spherical figure, in principle, by use of the table of chords and Menelaus’ theorem, the application of the theorem to spherical problems was very difficult in practice. Al-Jayyānī’s work on spherical trigonometry “contains formulae for right-handed triangles, the general law of sines, and the solution of a spherical triangle by means of the polar triangle.” This treatise later had a “strong influence on European mathematics”, and his “definition of ratios as numbers” and “method of solving a spherical triangle when all sides are unknown” are likely to have influenced Regiomontanus.
Abû Bakr Muḥammad Ibn Yaḥyà known as Ibn Bājjah was an Andalusian polymath: an astronomer, logician, musician, philosopher, physician, physicist, psychologist, botanist, poet and scientist. He was known in the West by his Latinized name, Avempace. He was born in Zaragoza in what is today Aragon, Spain around 1085, and died in Fes, Morocco in 1138. Avempace worked as vizir for Abu Bakr ibn Ibrahim Ibn Tîfilwît, the Almoravid governor of Zaragoza. Avempace also wrote poems (panegyrics and ‘muwasshahat’) for him. Avempace joined in poetic competitions with the poet al-Tutili. He later worked, for some twenty years, as the vizir of Yahyà ibn Yûsuf Ibn Tashufin, another brother of the Almoravid Sultan Yusuf Ibn Tashufin (died 1143) in Morocco. He was the famous author of the Kitab al-Nabat (The Book of Plants), a popular work on Botany, which defined the sex of Plants. Among his many teachers was Abu Jafar ibn Harun of Trujillo a physician in Seville, Al-Andalus.
His philosophic ideas had a clear effect on Ibn Rushd and Albertus Magnus. Most of his writings and book were not completed (or well organized) because of his early death. He had a vast knowledge of Medicine, Mathematics and Astronomy. His main contribution to Islamic Philosophy is his idea on Soul Phenomenology, which was never completed. His beloved expressions were Gharib غريب and Mutawahhid متوحد, two approved and popular expressions of Islamic Gnostics. Ibn Bajjah was, in his time, not only a prominent figure of philosophy, but also of music and poetry. His diwan (Arabic: collection of poetry) was rediscovered in 1951. Though many of his works have not survived, his theories on astronomy and physics were preserved by Maimonides and Averroes respectively, which had a subsequent influence on later astronomers and physicists in the Islamic civilization and Renaissance Europe, including Galileo Galilei
“I have heard that Abu Bakr [Ibn Bajja] discovered a system in which no epicycles occur, but eccentric spheres are not excluded by him. I have not heard it from his pupils; and even if it be correct that he discovered such a system, he has not gained much by it, for eccentricity is likewise contrary to the principles laid down by Aristotle…. I have explained to you that these difficulties do not concern the astronomer, for he does not profess to tell us the existing properties of the spheres, but to suggest, whether correctly or not, a theory in which the motion of the stars and planets is uniform and circular, and in agreement with observation.”
In his commentary on Aristotle’s Meteorology, Ibn Bajjah presented his own theory on the Milky Way galaxy. Aristotle believed the Milky Way to be caused by “the ignition of the fiery exhalation of some stars which were large, numerous and close together” and that the “ignition takes place in the upper part of the atmosphere, in the region of the world which is continuous with the heavenly motions.” On the other hand, Aristotle’s Arabic commentator Ibn al-Bitriq considered “the Milky Way to be a phenomenon exclusively of the heavenly spheres, not of the upper part of the atmosphere” and that the “light of those stars makes a visible patch because they are so close.” Ibn Bajjah’s view differed from both, as he considered “the Milky Way to be a phenomenon both of the spheres above the moon and of the sublunar region.” The Stanford Encyclopedia of Philosophy describes his theory and observation on the Milky Way as follows:
“The Milky Way is the light of many stars which almost touch one another. Their light forms a “continuous image” (khayâl muttasil) on the surface of the body which is like a “tent” (takhawwum) under the fierily element and over the air which it covers. Avempace defines the continuous image as the result of refraction (in‛ikâs) and supports its explanation with an observation of a conjunction of two planets, Jupiter and Mars which took place in 500/1106-7. He watched the conjunction and “saw them having an elongate figure” although their figure is circular.”
Ibn Bajjah also reported observing “two planets as black spots on the face of the Sun.” In the 13th century, the Maragha astronomer Qotb al-Din Shirazi identified this observation as the transit of Venus and Mercury. However, Ibn Bajjah cannot have observed a Venus transit, as there were no Venus transits in his lifetime.
Text 71 of Averroes‘ commentary on Aristotle‘s Physics contains a discussion on Avempace’s theory of motion, as well as the following quotation from the seventh book of Ibn Bajjah’s lost work on physics:
“And this resistance which is between the plenum and the body which is moved in it, is that between which, and the potency of the void, Aristotle made the proportion in his fourth book; and what is believed to be his opinion, is not so. For the proportion of water to air in density is not as the proportion of the motion of the stone in water to its motion in air; but the proportion of the cohesive power of water to that of air is as the proportion of the retardation occurring to the moved body by reason of the medium in which it is moved, namely water, to the retardation occurring to it when it is moved in air.”
“For, if what some people have believed were true, then natural motion would be violent; therefore, if there were no resistance present, how could there be any motion? For it would necessarily be instantaneous. What then shall be said concerning the circular motion? There is no resistance there, because there is no cleavage of a medium involved; the place of the circle is always the same, so that it does not leave one place and enter another; it is therefore necessary that the circular motion should be instantaneous. Yet we observe in it the greatest slowness, as in the case of the fixed stars, and also the greatest speed, as in the case of the diurnal rotation. And this is caused only by the difference in perfection between the mover and the moved. When therefore the mover is of greater perfection, that which is moved by it will be more rapid; and when the mover is of lesser perfection, it will be nearer (in perfection) to that which is moved, and the motion will be slower.”
Averroes writes the following comments on Avempace’s theory of motion:
“Avempace, however, here raises a good question. For he says that it does not follow that the proportion of the motion of one and the same stone in water to its motion in air is as the proportion of the density of water to the density of air, except on the assumption that the motion of the stone takes time only because it is moved in a medium. And if this assumption were true, it would then be the case that no motion would require time except because of something resisting it for the medium seems to impede the thing moved. And if this were so, then the heavenly bodies, which encounter no resistant medium, would be moved instantaneously. And he says that the proportion of the rarity of water to the rarity of air is as the proportion of the retardation occurring to the moved body in water, to the retardation occurring to it in air.”
“And if this which he has said be conceded, then Aristotle’s demonstration will be false; because, if the proportion of the rarity of one medium to the rarity of the other is as the proportion of accidental retardation of the movement in one of them to the retardation occurring to it in the other, and is not as the proportion of the motion itself, it will not follow that what is moved in a void would be moved in an instant; because in that case there would be subtracted from the motion only the retardation affecting it by reason of the medium, and its natural motion would remain. And every motion involves time; therefore what is moved in a void is necessarily moved in time and with a divisible motion; and nothing impossible will follow. This, then, is Avempace’s question.”
In Islamic psychology, Ibn Bajjah “based his psychological studies on physics.” In his essay, Recognition of the Active Intelligence, he wrote that active intelligence is the most important ability of human beings, and he wrote many other essays on sensations and imaginations. He concluded that “knowledge cannot be acquired by senses alone but by Active Intelligence, which is the governing intelligence of nature.” He begins his discussion of the soul with the definition that “bodies are composed of matter and form and intelligence is the most important part of man—sound knowledge is obtained through intelligence, which alone enables one to attain prosperity and build character.” He viewed the unity of the rational soul as the principle of the individual identity, and that by its contact with the Active Intelligence, it “becomes one of those lights that gives glory to God.” His definition of freedom is “that when one can think and act rationally”. He also writes that “the aim of life should be to seek spiritual knowledge and make contact with Active Intelligence and thus with the Divine.”
Abū-Marwān ʻAbd al-Malik ibn Zuhr ( ; 1094–1162 CE), better known in the West by his Latinized name Avenzoar, was an Arab–Muslim physician, surgeon and a contemporary of Averroes and Maimonides. He was born at Seville (now southwestern Spain) and was regarded as the most renowned physician of Al-Andalus.Ibn Zuhr was known for his emphasis on a more rational, empiricbasis of medicine. His major work, Al-Taysīr fil-Mudāwāt wal-Tadbīr (“Book of Simplification Concerning Therapeutics and Diet”), was translated into Latin and Hebrew and was influential to the progress of surgery. He also improved surgical and medical knowledge by keying out several diseases and their treatments. Ibn Zuhr performed the first experimental tracheotomy on a goat. He is thought to have made the earliest description of bezoar stones as medicinal items
His full name is ‘Abū-Marwān ʻAbd al-Malik ibn Abī al-ʻAlāʼ Ibn Zuhr (Arabic: أبو مروان عبد الملك بن أبي العلاء بن زهر). His name was Latinized as Avenzoar, Abumeron, Abhomeron, Alomehón or Abhomjeron.
He was born in Seville and belonged to the Banu Zuhr family (of Arab origin), which produced six consecutive generations of physicians, and included jurists, poets, viziers or courtiers, and midwives who served under rulers of Al-Andalus. He studied medicine with his father, Abu’l-Ala Zuhr (d.1131) at an early age.
Fleeing from Seville
He fell out of favour of with the Almoravid ruler, ‘Ali bin Yusuf bin Tashufin, and fled from Seville. He was however, apprehended and jailed in Marrakesh in 1140. Later in 1147 when the Almohad dynasty conquered Seville, he returned and devoted himself to medical practice. He died in Seville in 1162.
Ibn Zuhr wrote three major books:
Kitab al-iqtisad fi Islah Al-Anfus WA al-Ajsad, written in his youth.
Kitab al-aghdhiya, on foods and regimen of health, written in exile in Morocco.
Kitab al-taysir, his opus magnum and written at the request of his colleague Averroes.
Ibn Zuhr presented an accurate description of the esophageal and stomach cancers, as well as other lesions.
Ibn Zuhr introduced animal testing as an experimental method of testing surgical procedures before applying them to human patients.
The Jewish physician-philosopher Maimonides admired Ibn Zuhr, describing him as “unique in his age and one of the great sages”. He frequently quoted him in his medical texts. He performed medical procedures on animals before doing them on humans to know if they would work
Abu al-Qasim Khalaf ibn al-Abbas Al-Zahrawi (936–1013), also known in the West as Albucasis, was an Arab Muslim physician who lived in Al-Andalus. He is considered the greatest medieval surgeon to have appeared from the Islamic World, and has been described by many as the father of modern surgery. His greatest contribution to medicine is the Kitab al-Tasrif, a thirty-volume encyclopedia of medical practices. His pioneering contributions to the field of surgical procedures and instruments had an enormous impact in the East and West well into the modern period, where some of his discoveries are still applied in medicine to this day.
Abū Al-Qāsim was born in the city El-Zahra, six miles northwest of Córdoba, Andalusia. The nisba (attributive title), Al-Ansari, suggests origin from the Medinian tribe of Al-Ansar.He lived most of his life in Córdoba. It is also where he studied, taught and practiced medicine and surgery until shortly before his death in about 1013, two years after the sacking of El-Zahra. Few details remain regarding his life, aside from his published work, due to the destruction of El-Zahra during later Castillian-Andalusian conflicts. His name first appears in the writings of Abu Muhammad bin Hazm (993 – 1064), who listed him among the greatest physicians of Moorish Spain. But we have the first detailed biography of al-Zahrawī from al-Ḥumaydī‘s Jadhwat al-Muqtabis (On Andalusian Savants), completed six decades after al-Zahrawī’s death. He was a contemporary of Andalusian chemists such as Ibn al-Wafid, Maslamah Ibn Ahmad al-Majriti and Artephius. Albucasis was 77 years old when he died
Abū al-Qāsim was a court physician to the Andalusian caliph Al-Hakam II. He devoted his entire life and genius to the advancement of medicine as a whole and surgery in particular. His best work was the Kitab al-Tasrif, discussed below. Abū al-Qāsim specialized in curing disease by cauterization. He invented several devices used during surgery, for purposes such as inspection of the interior of the urethra, applying and removing foreign bodies from the throat, inspection of the ear, etc. He is also credited to be the first to describe ectopic pregnancy in 963, in those days a fatal affliction.Al-Zahrawi was the first to illustrate the various cannulae and the first to treat a wart with an iron tube and caustic metal as a boring instrument. He was also the first to draw hooks with a double tip for use in surgery.
Abū al-Qāsim’s thirty-chapter medical treatise, Kitab al-Tasrif, completed in the year 1000, covered a broad range of medical topics, including dentistry and childbirth, which contained data that had accumulated during a career that spanned almost 50 years of training, teaching and practice. In it he also wrote of the importance of a positive doctor-patient relationship and wrote affectionately of his students, whom he referred to as “my children”. He also emphasized the importance of treating patients irrespective of their social status. He encouraged the close observation of individual cases in order to make the most accurate diagnosis and the best possible treatment. Al-Tasrif was later translated into Latin by Gerard of Cremona in the 12th century, and illustrated. For perhaps five centuries during the European Middle Ages, it was the primary source for European medical knowledge, and served as a reference for doctors and surgeons.
Not always properly credited, Abū Al-Qāsim’s al-Tasrif described both what would later became known as “Kocher’s method” for treating a dislocated shoulder and “Walcher position” in obstetrics. Al-Tasrif described how to ligature blood vessels almost 600 years before Ambroise Paré, and was the first recorded book to document several dental devices and explain the hereditary nature of haemophilia. He was also the first to describe a surgical procedure for ligating the temporal artery for migraine, also almost 600 years before Pare recorded that he had ligated his own temporal artery for headache that conforms to current descriptions of migraine. Abū al-Qāsim was therefore the first to describe the migraine surgery procedure that is enjoying a revival in the 21st century, spearheaded by Elliot Shevel a South African surgeon. Abū al-Qāsim also described the use of forceps in vaginal deliveries. He introduced over 200 surgical instruments. Many of these instruments were never used before by any previous surgeons.His use of catgut for internal stitching is still practised in modern surgery. The catgut appears to be the only natural substance capable of dissolving and is acceptable by the body. Abū al-Qāsim also invented the forceps for extracting a dead fetus, as illustrated in the Al-Tasrif.
In pharmacy and pharmacology, Abū al-Qāsim al-Zahrawī pioneered the preparation of medicines by sublimation and distillation. His Liber Servitoris is of particular interest, as it provides the reader with recipes and explains how to prepare the “simples” from which were compounded the complex drugs then generally used.
Al-Zahrawi was the “most frequently cited surgical authority of the Middle Ages”.
Donald Campbell, a historian of Arabic medicine, described Al-Zahrawi’s influence on Europe as follows:
The chief influence of Albucasis on the medical system of Europe was that his lucidity and method of presentation awakened a prepossession in favour of Arabic literature among the scholars of the West: the methods of Albucasis eclipsed those of Galen and maintained a dominant position in medical Europe for five hundred years, i.e long after it had passed its usefulness. He, however, helped to raise the status of surgery in Christian Europe; in his book on fractures and luxations, he states that ‘this part of surgery has passed into the hands of vulgar and uncultivated minds, for which reason it has fallen into contempt.’ The surgery of Albucasis became firmly grafted on Europe after the time of Guy de Chauliac (d.1368).
In the 14th century, the French surgeon Guy de Chauliac quoted al-Tasrif over 200 times. Pietro Argallata (d. 1453) described Abū al-Qāsim as “without doubt the chief of all surgeons”. Abū al-Qāsim’s influence continued for at least five centuries, extending into the Renaissance, evidenced by al-Tasrif‘s frequent reference by French surgeon Jacques Delechamps (1513–1588).The street in Córdoba where he lived is named in his honor as “Calle Albucasis”. On this street he lived in house no. 6, which is preserved today by the Spanish Tourist Board with a bronze plaque (awarded in January 1977) which reads: “This was the house where Abul-Qasim lived.”
On Surgery and Instruments
On Surgery and Instruments is an illustrated surgical guide written by Albucasis, known in Arabic as ‘al-Zahrāwī’. Albucasis contributed many technological innovations, notably which tools to use in specific surgeries. In On Surgery and Instruments, he draws diagrams of each tool used in different procedures to clarify how to carry out the steps of each treatment. The full text consists of three books, intended for medical students looking to gain more knowledge within the field of surgery regarding procedures and the necessary tools.
Interestingly, Albucasis considers his educated opinion to be superior than that of the Ancients: “…whatever skill I have, I have derived for myself by my long reading of the books of the Ancients and my thirst to understand them until I extracted the knowledge of it from them. Then through the whole of my life I have adhered to experience and practice…I have made it accessible for you and rescued it from the abyss of prolixity”. Because he has extensively studied and practiced these topics, he believes that has earned the authority to challenge the revered statements of the Ancients. He has reached the limit of book learning, and is now adding-on to this knowledge with his own experiences.
Throughout the text, Albucasis uses an authoritative tone to declare his expertise on the topic. For example, when introducing topics or describing procedures, Albucasis often warns the reader of the skills necessary to complete the task. In chapter forty-eight, On cauterization for numbness, he defines the required knowledge for the procedure in a commanding tone: “This should not be attempted except by one who has a good knowledge of the anatomy of the limbs and of the exits of the nerves that move the body”. He invents a criterion to generate a standard of skill level, indicating that he himself has surpassed it due to training and experience. As such, he reiterates his preeminence by implying that he is part of an exclusive group of learned surgeons capable of correctly completing this cautery. In another instance, he states that the procedure should be avoided completely by incompetent surgeons: “However, no one should attempt this operation unless he has had long training and practice in the use of cautery”. In this example, Albucasis prohibits lesser-trained surgeons from practicing cautery. He firmly makes a decision for the field rather than suggesting a plan of action, asserting his authority. By outlining the exact qualifications necessary to properly execute this procedure, Albucasis places himself in the role of the current expert of this field of medicine.
This objective is also demonstrated in willingness to openly disagree with the ‘Ancients’. By declaring himself a dedicated student of the Ancients, he appoints himself a worthy critic of their practices. For example, Albucasis openly disparages the Ancients’ opinion that cauterization should only be used in the spring season: “…the Ancients…[affirmed] that spring was the best. Myself, I say that cautery is suitable at all times”. Four pages later, he again opposes the Ancients’ opinion that gold is the best material for cauterization, stating that iron is actually his preferred metal: “therefore in our own opinion cauterization is swifter and more successful with iron”.
In these two quotes, Albucasis uses his personal experience as a reliable source worthy of challenging the Ancients’ teachings. In chapter twenty-nine, On cauterization for pleurisy, he even ventures to state that one practice of the Ancients’ is dangerously incorrect: “Now one of the Ancients mentioned that there were some people who used an iron cautery shaped like a probe, and introduced it red hot into the intercostal space until it reached the abscess itself and evacuated the pus…but in this perforation with the cautery there is a danger either that the patient may die on the spot or that an incurable fistula may raise at the place”. By opposing the revered opinions of the Ancients throughout his guide, Albucasis pronounces himself as a new reliable source of medical knowledge worthy of followers . He believes that he has surpassed the limits of learning through studies, and is now in the realm of practice and experience, meriting his ability to critique the Ancients. Interestingly, while he does not hesitate to assert his expertise, he does not state his background training or any foundation that would prove his proficiency. He does state that he has extensively studied the Ancients, but not in what context.n ectopic pregnancy, and the first physician to identify the hereditary nature of haemophilia
Abū l-Walīd Muḥammad bin ʾAḥmad bin Rušd (Arabic: أبو الوليد محمد بن احمد بن رشد), commonly known as Ibn Rushd (Arabic: ابن رشد) or by his Latinized name Averroës (//; April 14, 1126 – December 10, 1198), was a Moroccan Andalusian Muslim polymath, a master of Aristotelian philosophy, Islamic philosophy, Islamic theology, Maliki law and jurisprudence, logic, psychology, politics and Arabic music theory, and the sciences of medicine, astronomy, geography, mathematics, physics and celestial mechanics. Averroes was born in Córdoba, Al Andalus, present-day Spain, and died in Marrakesh, present-day Morocco. He was interred in his family tomb at Córdoba. The 13th-century philosophical movement based on Averroes’ work is called Averroism.
Averroes was a defender of Aristotelian philosophy against Ash’ari theologians led by Al-Ghazali. Averroes’ philosophy was considered controversial in Muslim circles. Averroes had a greater impact on Western European circles and he has been described as the “founding father of secular thought in Western Europe”. The detailed commentaries on Aristotle earned Averroes the title “The Commentator” in Europe. Latin translations of Averroes’ work led the way to the popularization of Aristotle and were responsible for the development of scholasticism in medieval Europe
Averroes’ name is also seen as “Averroës”, “Averroès” or “Averrhoës”, indicating that the “o” and the “e” form separate syllables. “Averroës” is a Latinisation of the Arabic name Ibn Rushd.
According to Ernest Renan, Averroes was also known as Ibin-Ros-din, Filius Rosadis, Ibn-Rusid, Ben-Raxid, Ibn-Ruschod, Den-Resched, Aben-Rassad, Aben-Rois, Aben-Rasd, Aben-Rust, Avenrosdy Avenryz, Adveroys, Benroist, Avenroyth and Averroysta.
Averroes was born in Córdoba to a family with a long and well-respected tradition of legal and public service. His grandfather Abu Al-Walid Muhammad (d. 1126) was chief judge of Córdoba under the Almoravids. His father, Abu Al-Qasim Ahmad, held the same position until the Almoravids were replaced by the Almohads in 1146.
Averroes’ education followed a traditional path, beginning with studies in Hadith, linguistics, jurisprudence and scholastic theology. Throughout his life he wrote extensively on Philosophy and Religion, attributes of God, origin of the universe, Metaphysics and Psychology. It is generally believed that he was perhaps once tutored by Ibn Bajjah (Avempace). His medical education was directed under Abu Jafar ibn Harun of Trujillo in Seville. Averroes began his career with the help of Ibn Tufail (“Aben Tofail” to the West), the author of Hayy ibn Yaqdhan and philosophic vizier of Almohad king Abu Yaqub Yusuf who was an amateur of philosophy and science. It was Ibn Tufail who introduced him to the court and to Ibn Zuhr (“Avenzoar” to the West), the great Muslim physician, who became Averroes’s teacher and friend. Averroes’s aptitude for medicine was noted by his contemporaries and can be seen in his major enduring work Kitab al-Kulyat fi al-Tibb (Generalities) the work was influenced by the Kitab al-Taisir fi al-Mudawat wa al-Tadbir (Particularities) of Ibn Zuhr. Averroes later reported how it was also Ibn Tufail that inspired him to write his famous commentaries on Aristotle:
Abu Bakr ibn Tufayl summoned me one day and told me that he had heard the Commander of the Faithful complaining about the disjointedness of Aristotle‘s mode of expression — or that of the translators — and the resultant obscurity of his intentions. He said that if someone took on these books who could summarize them and clarify their aims after first thoroughly understanding them himself, people would have an easier time comprehending them. “If you have the energy, ” Ibn Tufayl told me, “you do it. I’m confident you can, because I know what a good mind and devoted character you have, and how dedicated you are to the art. You understand that only my great age, the cares of my office — and my commitment to another task that I think even more vital — keep me from doing it myself. “—
Averroes also studied the works and philosophy of Ibn Bajjah (“Avempace” to the West), another famous Islamic philosopher who greatly influenced his own Averroist thought.
However, while the thought of his mentors Ibn Tufail and Ibn Bajjah were mystic to an extent, the thought of Averroes was purely rationalist. Together, the three men are considered the greatest Andalusian philosophers. Averroes devoted the next 30 years to his philosophical writings.
In 1160, Averroes was made Qadi (judge) of Seville and he served in many court appointments in Seville, Cordoba, and Morocco during his career. Sometimes during the reign of Yaqub al-Mansur, Averroes’ political career was abruptly ended and he faced severe criticism from the Fuqaha (Islamic jurists) of the time.
A contemporary of Averroes, Abdelwahid al-Marrakushi writing in 1224, reported that there were secret and public reasons for his falling out of favor with Yaqub al-Mansour:
And in his days [Yaqub al-Mansur], Abu al-Walid Ibn Rushd faced his severe ordeal and there were two causes for this; one is known and the other is secret. The secret cause, which was the major reason, is that Abu al-Walid [Averroes] —may God have mercy on his soul— when summarizing, commenting and expending upon Aristotle’s book “History of Animals” wrote: “And I saw the Giraffe at the garden of the king of the Berbers”.
And that is the same way he would mention another king of some other people or land, as it is frequently done by writers, but he omitted that those working for the service of the king should glorify him and observe the usual protocol. This was why they held a grudge against him [Averroes] but initially, they did not show it and in reality, Abu al-Walid wrote that inadvertently…Then a number of his enemies in Cordoba, who were jealous of him and were competing with him both in knowledge and nobility, went to Yaqub al-Mansur with excerpts of Abu Walid’s work on some old philosophers which were in his own handwriting. They took one phrase out of context that said: “and it was shown that Venus is one of the Gods” and presented it to the king who then summoned the chiefs and noblemen of Córdoba and said to Abu al-Walid in front of them “Is this your handwriting?”. Abu al-Walid then denied and the king said “May God curse the one who wrote this” and ordered that Abu al-Walid be exiled and all the philosophy books to be gathered and burned…And I saw, when I was in Fes, these books being carried on horses in great quantities and burned—Abdelwahid al-Marrakushi, “The Pleasant Book in Summarizing the History of the Maghreb”, (1224)
Averroes’s strictly rationalist views collided with the more orthodox views of Abu Yusuf Ya’qub al-Mansur, who therefore eventually banished Averroes, though he had previously appointed him as his personal physician. Averroes was not reinstated until shortly before his death in the year 1198 AD.
Averroes’s works were spread over 20,000 pages covering a variety of different subjects, including early Islamic philosophy, logic in Islamic philosophy, Arabic medicine, Arabic mathematics, Arabic astronomy, Arabic grammar, Islamic theology, Sharia (Islamic law), and Fiqh (Islamic jurisprudence). In particular, his most important works dealt with Islamic philosophy, medicine and Fiqh. He wrote at least 67 original works, which included 28 works on philosophy, 20 on medicine, 8 on law, 5 on theology, and 4 on grammar, in addition to his commentaries on most of Aristotle’s works and his commentary on Plato‘s The Republic.
Averroes commentaries on Aristotle were the foundation for the Aristotelian revival in the 12th and 13th centuries. Averroes wrote short commentaries on Aristotle’s work in logic, physics, and psychology. Averroes long commentaries provided an in depth line by line analysis of Aristotle’s “Posterior Analytics,” “De Anima,” “Physics,” “De Caelo,” and the “Metaphysics.”His most important original philosophical work was The Incoherence of the Incoherence (Tahafut al-tahafut), in which he defended Aristotelian philosophy against al-Ghazali‘s claims in The Incoherence of the Philosophers (Tahafut al-falasifa). Other works were the Fasl al-Maqal and the Kitab al-Kashf. Averroes is also a highly regarded legal scholar of the Maliki school. Perhaps his best-known work in this field is Bidāyat al-Mujtahid wa Nihāyat al-Muqtaṣid ( بداية المجتهد و نهاية المقتصد), a textbook of Maliki doctrine in a comparative framework.
Jacob Anatoli translated several of the works of Averroes from Arabic into Hebrew in the 13th century. Many of them were later translated from Hebrew into Latin by Jacob Mantino and Abraham de Balmes. Other works were translated directly from Arabic into Latin by Michael Scot. Many of his works in logic and metaphysics have been permanently lost, while others, including some of the longer Aristotelian commentaries, have only survived in Latin or Hebrew translation, not in the original Arabic. The fullest version of his works is in Latin, and forms part of the multi-volume Juntine edition of Aristotle published in Venice 1562-1574..
Abū Isḥāq Ibrāhīm ibn Yaḥyā al-Naqqāsh al-Zarqālī, also known as Al-Zarqali or Ibn Zarqala (1029–1087), was a Muslim instrument maker, astrologer, and one of the leading astronomers of his time. Although his name is conventionally given as al-Zarqālī, it is probable that the correct form was al-Zarqālluh. In Latin he is referred to as Arzachel or Arsechieles, a modified form of Arzachel, meaning ‘the engraver’. He lived in Toledo in Castile, Al-Andalus (now Spain), moving to Córdoba later in his life. His works inspired a generation of Islamic astronomers in Andalusia.
Al-Zarqālī was born to a family of Visigoth which converted to Islam in a village near the outskirts of Toledo, then a famous capital of the Taifa of Toledo, known for its co-existence between Muslims and Christians. He was trained as a metalsmith and due to his skills he was nicknamed Al-Nekkach (in Andalusian Arabic “the engraver of metals”). His Latinized name, ‘Arzachel’ is formed from the Arabic al-Zarqali al-Naqqash, meaning ‘the engraver’.He was particularly talented in Geometry and Astronomy. He is known to have taught and visited Córdoba on various occasions his extensive experience and knowledge eventually made him the foremost astronomer of his time. Al-Zarqālī was also an inventor, and his works helped to put Toledo at the intellectual center of Al-Andalus. He is also referred to in the works of Chaucer, as ‘Arsechieles’.
In the year 1085 Toledo was taken by Alfonso VI of Castile and remained after that under Christian rule. Al-Zarqālī and his colleagues, such as Al‐Waqqashi (1017–1095) of Toledo, had to flee. It is unknown whether the aged Al-Zarqālī fled to Cordoba or died in a Moorish refuge camp. His works influenced Ibn Bajjah (Avempace), Ibn Tufail (Abubacer), Ibn Rushd (Averroës), Ibn al-Kammad, Ibn al‐Haim al‐Ishbili and Nur ad-Din al-Betrugi (Alpetragius). In the 12th century, Gerard of Cremona translated al-Zarqali’s works into Latin. He referred to Al-Zarqali as an astronomer and magician. Ragio Montanous wrote a book in the 15th century on the advantages of the Sahifah al-Zarqalia. In 1530, the German scholar Jacob Ziegler wrote a commentary on one of al-Zarqali’s works. In his “De Revolutionibus Orbium Coelestium”, in the year 1530, Nicolaus Copernicus quotes the works of al-Zarqali and Al-Battani.
Al-Zarqālī wrote two works on the construction of an instrument (an equatorium) for computing the position of the planets using diagrams of the Ptolemaic model. These works were translated into Spanish in the 13th century by order of King Alfonso X in a section of the Libros del Saber de Astronomia entitled the “Libros de las laminas de los vii planetas”. He also invented a perfected kind of astrolabe known as “the tablet of the al-Zarqālī” (al-ṣafīḥā al-zarqāliyya), which was famous in Europe under the name Saphaea.There is a record of an al-Zarqālī who built a water clock, capable of determining the hours of the day and night and indicating the days of the lunar months. According to a report found in al-Zuhrī‘s Kitāb al-Juʿrāfīyya, his name is given as Abū al-Qāsim bin ʿAbd al-Raḥmān, also known as al-Zarqālī, which made some historians think that this is a different person.
Al-Zarqali corrected geographical data from Ptolemy and Al-Khwarizmi. Specifically, he corrected Ptolemy’s estimate of the length of the Mediterranean sea from 62 degrees to the correct value of 42 degrees In his treatise on the solar year, which survives only in a Hebrew translation, he was the first to demonstrate the motion of the solar apogee relative to the fixed background of the stars. He measured its rate of motion as 12.9 seconds per year, which is remarkably close to the modern calculation of 11.6 seconds. Al-Zarqālī’s model for the motion of the Sun, in which the center of the Sun’s deferent moved on a small, slowly-rotating circle to reproduce the observed motion of the solar apogee, was discussed in the thirteenth century by Bernard of Verdun and in the fifteenth century by Regiomontanus and Peurbach. In the sixteenth century Copernicus employed this model, modified to heliocentric form, in his De Revolutionibus Orbium Coelestium.
Tables of Toledo
Al-Zarqālī also contributed to the famous Tables of Toledo, an adaptation of earlier astronomical data to the location of Toledo along with the addition of some new material. Al-Zarqālī was famous as well for his own Book of Tables. Many “books of tables” had been compiled, but his almanac contained tables which allowed one to find the days on which the Coptic, Roman, lunar, and Persian months begin, other tables which give the position of planets at any given time, and still others facilitating the prediction of solar and lunar eclipses. He also compiled an almanac that directly provided “the positions of the celestial bodies and need no further computation”. The work provided the true daily positions of the sun for four Julian years from 1088 to 1092, the true positions of the five planets every 5 or 10 days over a period of 8 years for Venus, 79 years for Mars, and so forth, as well as other related tables.
His Zij and Almanac were translated into Latin by Gerard of Cremona in the 12th century, and contributed to the rebirth of a mathematically-based astronomy in Christian Europe and were later incorporated into the Tables of Toledo in the 12th century and the Alfonsine tables in the 13th century.In designing an instrument to deal with Ptolemy’s complex model for the planet Mercury, in which the center of the deferent moves on a secondary epicycle, al-Zarqālī noted that the path of the center of the primary epicycle is not a circle, as it is for the other planets. Instead it is approximately oval and similar to the shape of a pignon. Some writers have misinterpreted al-Zarqālī’s description of an earth-centered oval path for the center of the planet’s epicycle as an anticipation of Johannes Kepler‘s sun-centered elliptical paths for the planets. Although this may be the first suggestion that a conic section could play a role in astronomy, al-Zarqālī did not apply the ellipse to astronomical theory and neither he nor his Iberian or Maghrebi contemporaries used an elliptical deferent in their astronomical calculations.
Major Works and publications :
1-“Al Amal bi Assahifa Az-Zijia”;
3-“Al Madkhal fi Ilm Annoujoum”;
4-“Rissalat fi Tarikat Istikhdam as-Safiha al-Moushtarakah li Jamiâ al-ouroud”;