Friday Sermon

In the modern world Islam is seen as many things, but rarely is it viewed as a source of inspiration and enlightenment. Though it is a force of enlightenment and it is not only verses of the Quran that testify to that fact but also the great body of scholarship produced during the Middle Ages.

While Europe was in the midst of darkness, it was the Muslims, spurred on by the light of their new Deen who picked up the torch of scholarship and science. It was the Muslims who preserved the knowledge of antiquity, elaborated upon it, and finally, passed it on to Europe.

Although every people earn what they do and pass on, it is important for us to learn about and appreciate the contributions of the Islamic civilization by the early Muslims.

Colonialism, the institution of the Western educational model, along with Eurocentrism often portrays Islam as backward, incompatible with science and technology and anti-educational.

Muslim schoolchildren never learn of their glorious past and often the only thing passed on to them is the inferiority complex of the generation before them. From the past, we can learn from our mistakes and use the analysis of those great examples before us as role models to enrich us in the future.

In the seventh century A.D., the prophet Muhammad (SAW) was sent to the people of Arabia. Within a decade of his death, the Muslims had conquered all of the Arabian peninsulae. Within a century, Islam had spread from Al-Andalus in Spain to the borders of China. Islam unified science, theology, and philosophy.

Muslims were commanded to study, seek knowledge, and learn and benefit from others’ experiences by Allah (SWT) in the Holy Quran and by the prophet Muhammad (SAW) in the Sunnah. It was this that inspired the Muslims to great heights in sciences, medicine, mathematics, astronomy, chemistry, philosophy, art and architecture.

Muslim scholars began obtaining Greek treatises and started their study and translation into Arabic a few centuries after the Hijrah (622 A.D.) They critically analyzed, collated, corrected and supplemented substantially the Greek science and philosophy. After this period began what is known as the Golden Age of Islam, which lasted for over two centuries. It is here we find many of the great scientists of Islam who literally left behind hundreds and thousands of books on the various branches of science.

Ibn al-Nafis

Ibn al-Nafis (1205-1288), also known as Al-Quarashi, an ancient Islamic physician and expert on the Shafi’i school of Islamic law. Ibn al-Nafis is remembered for his numerous contributions to medicine, particularly the first description of pulmonary circulation that is, the movement of blood from the right to the left ventricles of the heart via the lungs.

Ibn al-Nafis, whose full name was Ala-ad-Din Abu Al-Ala Ali ibn Abi al-Haram al-Qurayshi ad-Dimashqi ibn an-Nafis, was born in Damascus, Syria, where he later studied medicine. His professional career was centered in Egypt, where he served as the chief of physicians and subsequently as the head of the Nasiri hospital in Cairo.

Ibn al-Nafis is best known for his writings on physiology and medicine. His book Sharh Tashrih al-Qanun described pulmonary circulation centuries before noted English physician William Harvey described the circulation of blood in 1628. His voluminous book on the art of medicine, titled Kitab al Shamil, featured sections on surgical techniques and the obligations of surgeons to their patients. Other works by Ibn al-Nafis included treatises on eye disease and the diet, as well as commentaries on the medical writings of ancient Greek physician Hippocrates.

Nur ad-Din al-Betrugi

Nur ad-Din al-Betrugi (also spelled Nur al-Din Ibn Ishaq Al-Bitruji and Abu Ishâk ibn al-Bitrogi; another spelling is al Bidrudschi) (known in the West by the Latinized name of Alpetragius) (died ca. 1204 AD) was an Arab astronomer and philosopher of the Islamic Golden Age (Middle Ages). Born in Morocco, he settled in Seville, in Andalusia. He became a disciple of Ibn Tufail (Abubacer) and was a contemporary of Averroës.

Al Betrugi wrote the Kitab-al-Hay’ah, translated from the Arabic into Hebrew, and then into Latin by Michael Scot as De motibus colostrum (first printed in Vienna in 1531).

He advanced a theory of planetary motion in which he wished to avoid both epicycles and eccentrics, and to account for the phenomena peculiar to the wandering stars, by compounding rotations of homocentric spheres. This was a modification of the system of planetary motion proposed by his predecessors, Ibn Bajjah (Avempace) and Ibn Tufail (Abubakar).

The crater Alpetragius on the Moon is named after him.

Ibn Sina most commonly known in English by his Latinized name Avicenna (probably because Avicenna sounds more western than Ibn Sina) (Greek: Abitzianos), (c. 1980 – 1037) was a Persian polymath and the foremost physician and philosopher of his time. He was also an astronomer, chemist, geologist, Hafiz, Islamic psychologist, Islamic scholar, Islamic theologian, logician, paleontologist, mathematician, Maktab teacher, physicist, poet, and scientist.

Ibn Sina studied medicine under a physician named Koushyar. He wrote almost 450 treatises on a wide range of subjects, of which around 240 have survived. In particular, 150 of his surviving treatises concentrate on philosophy and 40 of them. concentrate on medicine. His most famous works are The Book of Healing, a vast philosophical and scientific encyclopedia, and The Canon of Medicine, which was a standard medical text at many medieval universities. The Canon of Medicine was used as a text-book in the universities of Montpellier and Louvain as late as 1650.

Ibn Sina developed a medical system that combined his own personal experience with that of Islamic medicine, the medical system of the Greek physician Galen, Aristotelian metaphysics (Avicenna was one of the main interpreters of Aristotle), and ancient Persian, Mesopotamian and Indian medicine. Ibn Sina is considered the father of modern medicine and clinical pharmacology particularly for his introduction of systematic experimentation and quantification into the study of physiology, his discovery of the contagious nature of infectious diseases, the introduction of quarantine to limit the spread of contagious diseases, the introduction of experimental medicine, evidence-based medicine, clinical trials, randomized controlled trials, efficacy tests, clinical pharmacology, neuropsychiatry, the idea of the syndrome, and the importance of dietetics and the influence of climate and environment on health.

He was also the founder of Avicennian logic and the philosophical school of Avicennism, which were influential among both Muslim and Scholastic thinkers. He is also considered the father of the fundamental concept of momentum in physics and regarded as a pioneer of aromatherapy for his invention of steam distillation and extraction of essential oils. He also developed the concept of uniformitarianism and law of superposition in geology, for which he is considered to be the ‘FATHER OF GEOLOGY’.

George Sarton, an early author of the history of science, wrote in the Introduction to the History of Science:

One of the most famous exponents of Muslim universalism and an eminent figure in Islamic learning was Ibn Sina, known in the West …as Avicenna (981-1037). For a thousand years he has retained his original renown as one of the greatest thinkers and medical scholars in history. His most important medical works are the Qanun (Canon) and a treatise on Cardiac drugs. The ‘Qanun fi-l-Tibb’ is an immense encyclopedia of medicine. It contains some of the most illuminating thoughts pertaining to the distinction of mediastinitis from pleurisy; contagious nature of phthisis; distribution of diseases by water and soil; careful description of skin troubles; of sexual diseases and perversions; of nervous ailments.

Abu Ishaq Ibrahim ibn Yaya al-Naqqash al-Zarqali (1029–1087), Latinized as Arzachel, also spelled Az-Zarqali, was a leading Arab mathematician and the foremost astronomer of his time. He lived in Toledo in Castile, Al-Andalus (now Spain).His works inspired a generation of Islamic astronomers in Andalusia.

Az-Zarqali was not only just a Theoretical scientist but an inventor as well. His inventions and works put Toledo at the intellectual center of Al-Andalus. Al-Zarqali constructed the famed clocks of Toledo. The clocks were in use until 1135 when King Alfonso VI tried to discover how they worked and asked his soldiers to dismantle them. Once they were taken apart, nobody could reassemble them. They constituted a very precise lunar calendar and were to some extent, the predecessors of the clocks or planetary calendar devices.

Astronomy:

Combining theoretical knowledge with technical skills, he excelled at the construction of precision instruments for astronomical use. He invented the flat astrolabe a device that was ‘universal,’ for it could be used at any latitude. This instrument came to be known as the Saphea in Latin Europe.

Al-Zarqali also built a water clock capable of determining the hours of the day and night and indicating the days of the lunar months.

Al-Zarqali also wrote a treatise on the construction of an instrument (an aquarium) for computing the position of the planets using diagrams of the Ptolemaic model.

This work was 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 Los laminas de Los vii planets.”

Theory:

Al-Zarqali corrected Ptolemy’s geographical data, specifically the length of the Mediterranean Sea. He was the first to prove conclusively the motion of the aphelion relative to the fixed background of the stars. He measured its rate of motion as 12.04 seconds per year, which is remarkably close to the modern calculation of 11.8 seconds.

He also contributed to the famous Tables of Toledo, a compilation of astronomical data of unprecedented accuracy. Al-Zarqali was famous as well for his own Book of Tables. Many “books of tables” had been compiled, but his almanac (Spanish-Arabic al manakh; “calendar”) 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 valuable tables of latitude and longitude. This was the first almanac in the modern sense, that it was the first to provide entries that directly give “the positions of the celestial bodies and need no further computation”. The work provided the true daily positions of the sun, moon, and planets for four years from 1088 to 1092, as well as many other related tables.

The crater Arzachel on the Moon is named after him.

Abu Nasr al-Farabi

Abu Nasr al-Farabi (Abu Nasr Muhammad al-Farabi; known in the West as Alpharabius (c. 1872 – between 14, December 1950 and 12, January 1951), was a Muslim polymath and one of the greatest scientists and philosophers of the Islamic world in his time. He was also a cosmologist, logician, musician, psychologist, and sociologist.

Al-Farabi made notable contributions to the fields of logic, mathematics, medicine, music, philosophy, psychology and sociology.

Al-Farabi was also the first Muslim logician to develop a non-Aristotelian logic. He discussed the topics of future contingents, the number and relation of the categories, the relation between logic and grammar, and non-Aristotelian forms of inference. He is also credited for categorizing logic into two separate groups, the first being “idea” and the second being “proof.”

Al-Farabi had a great influence on science and philosophy for several centuries and was widely regarded to be second only to Aristotle in knowledge (alluded to by his title of “the Second Teacher”) in his time. His work, aimed at synthesis of philosophy, paved the way for the work of Ibn Sina (Avicenna).

Al-Farabi is also known for his early investigations into the nature of the existence of a void in Islamic physics. In thermodynamics, he appears to have carried out the first experiments concerning the existence of a vacuum, in which he investigated handheld plungers in water. He concluded that air volume can expand to fill available space, and he suggested that the concept of the perfect vacuum was incoherent.

His On the Cause of Dreams, which appeared as chapter 24 of his Book of Opinions of the people of the Ideal City, was a treatise on dreams, in which he was the first to distinguish between dream interpretation and the nature and causes of dreams.

According to Adamson, his work was singularly directed towards the goal of simultaneously reviving and reinventing the Alexandrian philosophical tradition, to which his Christian teacher, Yuhanna bin Haylan belonged. His success should be measured by the honorific title of “the second master” of philosophy (Aristotle being the first), by which he was known.

Al-Balkhi

Translation into Latin of a work of Albumasar De Magnis Conjunctions (“Of the great conjunctions”), Venice, 1515. Ja’far ibn Muhammad Abû Ma’shar al-Balkhî (10, August 1787 in the Persian province of Balkh, (now in Afghanistan)  9 March 1886 in al-Wasit, Iraq), also known as al-Falaki or Albumasar or Ibn Balkhî (also Albusar and Albuxar in the Latin West) was a Persian mathematician, astronomer, astrologer, and Islamic philosopher. Many of his works were translated into Latin and were well known amongst many European astrologers, astronomers, and mathematicians (mathematics) during the European Middle Ages. He also wrote on ancient Persian history.

A sample Ibn Balkhi’s manuscript on astronomy, 1850 Richard Lemay has argued that the writings of Albumasar were very likely the single most important original source of Aristotle’s theories of nature for European scholars, starting a little before the middle of the 12th century.

It was not until later in the 12th century that the original books of Aristotle on nature began to become available in Latin. The works of Aristotle on logic had been known earlier, and Aristotle was generally recognized as “the master of l…ogic.” But during the course of the 12th century, Aristotle was transformed into the “master of those who know,” and in particular a master of natural philosophy. It is especially interesting that the work of Albumasar (or Balkhi) in question is a treatise on astrology.

Its Latin title is Introductorium in Astronomiam, a translation of the Arabic Kitab al-Mudkhal al-Kabir ila ‘ilm ahkam an-nujjum, written in Baghdad in the year 848 A.D. It was translated into Latin first by John of Seville in 1133, and again, less literally and abridged, by Herman of Carinthia in 1140 A.D. Amir Khusrav mentions that Abu Mashar came to Benaras (Varanasi) and studied astronomy there for ten years.

Astronomy:

Abu Ma’shar developed a planetary model which some have interpreted as a heliocentric model. This is due to his orbital revolutions of the planets being given as heliocentric revolutions rather than geocentric revolutions, and the… only known planetary theory in which this occurs is in the heliocentric theory. His work on planetary theory has not survived, but his astronomical data was later recorded by al-Hashimi and al-Biruni.

Taqi al-Din Muhammad

Taqi al-Din Muhammad ibn Ma’ruf al-Shami al-Asadi (Turkish: Takiyuddin) (1526–1585) was a major Ottoman Turkish or Arab Muslim polymath: a scientist, astronomer and astrologer, engineer and inventor, clockmaker, physicist and mathematician, botanist and zoologist, pharmacist and physician, Islamic judge and mosque timekeeper, Islamic philosopher and theologian, and madrasah teacher.

He was the author of more than 90 books on a wide variety of subjects, including astronomy, astrology, clocks, engineering, mathematics, mechanics, optics and natural philosophy, though only 24 of those works have survived. He was widely regarded by his contemporaries in the Ottoman Empire as “the greatest scientist on earth”.

One of his books, Al-Turuq al-Taymiyyah fi al-alat al-ruhaniyya (The Sublime Methods of Spiritual Machines) (1551), described the workings of a rudimentary steam turbine, predating the more famous discovery of steam power by Giovanni Branca in 1629.

Taqi al-Din is also known for the invention of a six-cylinder ‘Monobloc’ pump in 1559, the invention of a variety of accurate clocks (including a weight-powered astronomical clock with an alarm) from 1556 to 1580, his construction of the Istanbul observatory of Taqi al-Din in 1577, and his astronomical activity there until 1580.

Ibn Al-Haytham

Alhazen, the great Islamic polymath Alhazen was born in Basra, in the Iraq province of the Buyid Persian Empire. He probably died in Cairo, Egypt. During the Islamic Golden Age, Basra was a “key beginning of learning”, and he was educated there and in Baghdad, the capital of the Abbasid Caliphate, and the focus of the “high point of Islamic civilization”. During his time in Buyid Iran, he worked as a civil servant and read many theological and scientific books.

One account of his career has him called to Egypt by Al-Hakim bi-Amr Allah, ruler of the Fatimid Caliphate, to regulate the flooding of the Nile, a task requiring an early attempt at building a dam at the present site of the Aswan Dam. After his fieldwork made him aware of the impracticality of this scheme and fearing the caliph’s anger, he feigned madness. He was kept under house arrest from 1011 until al-Hakim’s death in 1021. During this time, he wrote his influential Book of Optics.

Although there are tall tales that Ibn al-Haitham fled to Syria, ventured into Baghdad later in his life, or was even in Basra when he pretended to be insane, it is certain that he was in Egypt by 1038 at the latest. During his time in Cairo, he became associated with Al-Azhar University, as well the city’s “House of Wisdom”, known as Dar Al-Hekma (House of Knowledge), which was a library “first in importance” to Baghdad’s House of Wisdom.

After his house arrest ended, he wrote scores of other treatises on physics, astronomy, and mathematics. He later traveled to Islamic Spain. During this period, he had ample time for his scientific pursuits, which included optics, mathematics, physics, medicine, and the development of scientific methods; he left several outstanding books on these subjects.

Among his students, we know only two of them, Sorkhab (Sohrab), his Persian student who was one of the greatest people of Iran’s Semnan and was his student for over 3 years, and Abu al-Wafa Mubashir ibn Fatek a famous Egyptian scientist who learned mathematics from him.

Legacy:

Ibn al-Haythem made significant improvements in optics, physical science, and the scientific method which influenced the development of science for over five hundred years after his death. Ibn al-Haytham’s work on optics is credited with contributing a new emphasis on experiment. His influence on physical sciences in general, and on optics in particular, has been held in high esteem and, in fact, ushered in a new era in optical research, both in theory and practice.

The scientific method is considered to be so fundamental to modern science that some especially philosophers of science and practicing scientists consider earlier inquiries into nature to be pre-scientific.

Richard Powers nominated Ibn al-Haytham’s scientific method and scientific skepticism as the most influential idea of the second millennium.

George Sarton, the father of the history of science, wrote that “Ibn Haytham’s writings reveal his fine development of the experimental faculty” and considered him “not only the greatest Muslim physicist but by all means the greatest of medieval times.” Robert S. Elliot considers Ibn al-Haytham to be “one of the ablest students of optics of all times.” Professor Jim Al-Khalili also considers him the “world’s first true scientist”.

The Biographical Dictionary of Scientists wrote that Ibn al-Haytham was “probably the greatest scientist of the Middle Ages” and that “his work remained unsurpassed for nearly 600 years until the time of Johannes Kepler.”

At a scientific conference in February 2007 as a part of the Hockney-Falco thesis, Charles M. Falco argued that Ibn al-Haytham’s work on optics may have influenced the use of optical aids by Renaissance artists. Falco said that his and David Hockney’s examples of Renaissance art “demonstrate a continuum in the use of optics by artists from circa 1430, arguably initiated as a result of Ibn al-Haytham’s influence, until today.”

The Latin translation of his main work, Kitab al-Manazir (Book of Optics), exerted a great influence on Western science: for example, on the work of Roger Bacon, who cites him by name, and on Johannes Kepler. It brought about great progress in experimental methods.

His research in catoptrics (the study of optical systems using mirrors) centered on spherical and parabolic mirrors and spherical aberration. He made the observation that the ratio between the angle of incidence and refraction does not remain constant, and investigated the magnifying power of a lens. His work on catoptrics also contains the problem known as “Alhazen’s problem”. Meanwhile, in the Islamic world, Ibn al-Haytham’s work influenced Averroes’ writings on optics, and his legacy was further advanced through the ‘reforming’ of his Optics by Persian scientist Kamal al-Din al-Farisi (d. ca. 1320) in the latter’s Kitab Tanqih al-Manazir (The Revision of [Ibn al-Haytham’s] Optics).

The correct explanations of the rainbow phenomenon given by al-Farisi and Theodoric of Freiberg in the 14th century depended on Ibn al-Haytham’s Book of Optics. The work of Ibn al-Haytham and al-Farisi was also further advanced in the Ottoman Empire by polymath Taqi al-Din in his Book of the Light of the Pupil of Vision and the Light of the Truth of the Sights (1574).

He wrote as many as 200 books, although only 55 have survived, and many of those have not yet been translated from Arabic. Even some of his treatises on optics survived only through Latin translation. During the Middle Ages, his books on cosmology were translated into Latin, Hebrew and other languages.

The crater Alhazen on the Moon is named in his honor, as was the asteroid “59239 Alhazen”. In honour of Ibn al-Haytham, the Aga Khan University (Pakistan) named its Ophthalmology endowed chair as “The Ibn-e-Haitham Associate Professor and Chief of Ophthalmology”.

Ibn al-Haytham is featured on the obverse of the Iraqi 10,000 dinars banknote issued in 2003, and on 10 dinar notes from 1982. A research facility that UN weapons inspectors suspected of conducting chemical and biological weapons research in Saddam Hussein’s Iraq were also named after him.

Book of Optics:

Ibn al-Haytham’s most famous work is his seven-volume Arabic treatise on optics, Kitab al-Manazir (Book of Optics), written from 1011 to 1021. It has been ranked alongside Isaac Newton’s Philosophiae Naturalis Principia Mathematica as one of the most influential books in physics for introducing an early scientific method, and for initiating a revolution in optics and visual perception.

Optics was translated into Latin by an unknown scholar at the end of the 12th century or the beginning of the 13th century. It was printed by Friedrich Risner in 1572, with the title Optical thesaurus: Alhazeni Arabis Libri Septem, nuncprimum edit; Eiusdem liber De Crepusculis et niobium ascension bus. Risner is also the author of the name variant “Alhazen”; before Risner, he was known in the west as Alhacen, which is the correct transcription of the Arabic name.

This work enjoyed a great reputation during the Middle Ages. Works by Ibn al-Haytham on geometric subjects were discovered in the Bibliothèque Nationale in Paris in 1834 by E. A. Sedillo. Other manuscripts are preserved in the Bodleian Library at Oxford and in the library of Leiden.

Theory of Vision:

Ibn al-Haytham proved that light travels in straight lines using the scientific method in his Book of Optics (1021). Two major theories on vision prevailed in classical antiquity. The first theory, the emission theory, was supported by such thinkers as Euclid and Ptolemy, who believed that sight worked by the eye emitting rays of light.

The second theory, the intromission theory supported by Aristotle and his followers, had physical forms entering the eye from an object. Ibn al-Haytham argued that the process of vision occurs neither by rays emitted from the eye nor through physical forms entering it. He reasoned that a ray could not proceed from the eyes and reach the distant stars the instant after we open our eyes.

He also appealed to common observations such as the eye being dazzled or even injured if we look at a very bright light. He instead developed a highly successful theory which explained the process of vision as rays of light proceeding to the eye from each point on an object, which he proved through the use of experimentation. His unification of geometrical optics with philosophical physics forms the basis of modern physical optics.

Ibn al-Haytham proved that rays of light travel in straight lines, and carried out various experiments with lenses, mirrors, refraction, and reflection. He was also the first to reduce reflected and refracted light rays into vertical and horizontal components, which was a fundamental development in geometric optics. He also discovered a result similar to Snell’s law of sines, but did not quantify it and derive the law mathematically.

Ibn al-Haytham also gave the first clear description and correct analysis of the camera obscura and pinhole camera. While Aristotle, Theon of Alexandria, Al-Kindi (Alkindus) and Chinese philosopher Mozi had earlier described the effects of a single light passing through a pinhole, none of them suggested that what is being projected onto the screen is an image of everything on the other side of the aperture. Ibn al-Haytham was the first to demonstrate this with his lamp experiment where several different light sources are arranged across a large area. He was thus the first to successfully project an entire image from outdoors onto a screen indoors with the camera obscura.

In addition to physical optics, The Book of Optics also gave rise to the field of “physiological optics”. Ibn al-Haytham discussed the topics of medicine, ophthalmology, anatomy, and physiology, which included commentaries on Galenic works. He described the process of sight, the structure of the eye, image formation in the eye, and the visual system. He also described what became known as Hering’s law of equal innervation, vertical horopters, and binocular disparity, and improved on the theories of binocular vision, motion perception and horopters previously discussed by Aristotle, Euclid, and Ptolemy.

His most original anatomical contribution was his description of the functional anatomy of the eye as an optical system, or optical instrument.

His experiments with the camera obscura provided sufficient empirical grounds for him to develop his theory of corresponding point projection of light from the surface of an object to form an image on a screen. It was his comparison between the eye and the camera obscura which brought about his synthesis of anatomy and optics, which forms the basis of physiological optics.

As he conceptualized the essential principles of pinhole projection from his experiments with the pinhole camera, he considered image inversion to also occur in the eye and viewed the pupil as being similar to an aperture. Regarding the process of image formation, he incorrectly agreed with Avicenna that the lens was the receptive organ of sight, but correctly hinted at the retina being involved in the process.

Scientific method:

Neuroscientist Rosanna Gorini notes that “according to the majority of the historians al-Haytham was the pioneer of the modern scientific method.” Ibn al-Haytham developed rigorous experimental methods of controlled scientific testing to verify theoretical hypotheses and substantiate inductive conjectures. Ibn al-Haytham’s scientific method was very similar to the modern scientific method and consisted of the following procedures:

Observation Statement of the Problem Formulation of hypothesis Testing of hypothesis using experimentation Analysis of experimental results Interpretation of data and formulation of a conclusion Publication of findings An aspect associated with Ibn al-Haytham’s optical research is related to systemic and methodological reliance on experimentation (Eibar) and controlled testing in his scientific inquiries.

Moreover, his experimental directives rested on combining classical physics (‘ilm tabi’i) with mathematics (ta’alim; geometry in particular) in terms of devising the rudiments of what may be designated as a hypothetical deductive procedure in scientific research.

This mathematical-physical approach to experimental science supported most of his propositions in Kitab al-Manazir (The Optics; De inspections or Perspective) and grounded his theories of vision, light, and coluor, as well as his research in catoptrics and dioptrics (the study of the refraction of light). His legacy was further advanced through the ‘reforming’ of his Optics by Kamal al-Din al-Farisi (d. ca. 1320) in the latter’s Kitab Tanqih al-Manazir (The Revision of [Ibn al-Haytham’s] Optics).

The concept of Occam’s razor is also present in the Book of Optics. For example, after demonstrating that light is generated by luminous objects and emitted or reflected into the eyes, he states that therefore “the extra mission of [visual] rays is superfluous and useless.”

Alhazen’s problem:

His work on catoptrics in Book V of the Book of Optics contains a discussion of what is now known as Alhazen’s problem, first formulated by Ptolemy in 150 AD.

It comprises drawing lines from two points in the plane of a circle meeting at a point on the circumference and making equal angles with the normal at that point.

This is equivalent to finding the point on the edge of a circular billiard table at which a cue ball at a given point must be aimed in order to carom off the edge of the table and hit another ball at a second given point.

Thus, its main application in optics is to solve the problem, “Given a light source and a spherical mirror, find the point on the mirror where the light will be reflected the eye of an observer.” This leads to an equation of the fourth degree.

This eventually led Ibn al-Haytham to derive the earliest formula for the sum of fourth powers; by using an early proof by mathematical induction, he developed a method that can be readily generalized to find the formula for the sum of any integral powers.

He applied his result of sums on integral powers to find the volume of a paraboloid through integration. He was thus able to find the integrals for polynomials up to the fourth degree and came close to finding a general formula for the integrals of any polynomials.

This was fundamental to the development of infinitesimal and integral calculus.[65] Ibn al-Haytham eventually solved the problem using conic sections and a geometric proof, though many after him attempted to find an algebraic solution to the problem, which was finally found in 1997 by the Oxford mathematician Peter M. Neumann.

Other contributions:

The Book of Optics describes several early experimental observations that Ibn al-Haytham made in mechanics and how he used his results to explain certain optical phenomena using mechanical analogies.

He conducted experiments with projectiles and concluded that “it was only the impact of perpendicular projectiles on surfaces which were forceful enough to enable them to penetrate whereas the oblique ones were deflected. For example, to explain refraction from a rare to a dense medium, he used the mechanical analogy of an iron ball thrown at a thin slate covering a wide hole in a metal sheet.

A perpendicular throw would break the slate and pass through, whereas an oblique one with equal force and from an equal distance would not.” He used this result to explain explained how intense direct light hurts the eye:

“Applying mechanical analogies to the effect of light rays on the eye, ibn al-Haytham associated ‘strong’ lights with perpendicular rays and ‘weak’ lights with oblique ones. The obvious answer to the problem of multiple rays and the eye was in the choice of the perpendicular ray since there could only be one such ray from each point on the surface of the object which could penetrate the eye.”

Chapters 15–16 of the Book of Optics covered astronomy. Ibn al-Haytham was the first to discover that the celestial spheres do not consist of solid matter. He also discovered that the heavens are less dense than the air. These views were later repeated by Witelo and had a significant influence on the Copernican and Tychonic systems of astronomy.

Sudanese psychologist Omar Khaleefa has argued that Ibn al-Haytham should be considered by the “founder of experimental psychology”, for his pioneering work on the psychology of visual perception and optical illusions.

In the Book of Optics, Ibn al-Haytham was the first scientist to argue that vision occurs in the brain, rather than the eyes. He pointed out that personal experience has an effect on what people see and how they see, and that vision and perception are subjective. Khaleefa has also argued that Ibn al-Haytham should also be considered the “founder of psychophysics”, a subdiscipline and precursor to modern psychology.

Although Ibn al-Haytham made many subjective reports regarding vision, there is no evidence that he used quantitative psychophysical techniques and the claim has been rebuffed.

He came up with a theory to explain the Moon illusion, which played an important role in the scientific tradition of medieval Europe. It was an attempt to solve the problem of the Moon appearing larger near the horizon than it does while higher up in the sky, a debate that is unresolved to this day. Arguing against Ptolemy’s refraction theory, he redefined the problem in terms of perceived, rather than real, enlargement.

He said that judging the distance of an object depends on there being an uninterrupted sequence of intervening bodies between the object and the observer. With the Moon, however, there are no intervening objects.

Therefore, since the size of an object depends on its observed distance, which is in this case inaccurate, the Moon appears larger on the horizon.

Through works by Roger Bacon, John Pecham and Witelo based on Ibn al-Haytham’s explanation, the Moon illusion gradually came to be accepted as a psychological phenomenon, with Ptolemy’s theory being rejected in the 17th century.

Some have suggested that Ibn al-Haythams views on pain and sensation may have been influenced by Buddhist philosophy. He writes that every sensation is a form of ‘suffering’ and that what people call pain is only an exaggerated perception; that there is no qualitative difference but only a quantitative difference between pain and ordinary sensation.

Optical treatises:

Besides the Book of Optics, Ibn al-Haytham wrote several other treatises on optics. His Risala fi l-Daw’ (Treatise on Light) is a supplement to his Kitab al-Manazir (Book of Optics).

The text contained further investigations on the properties of luminance and its radiant dispersion through various transparent and translucent media. He also carried out further examinations into the anatomy of the eye and illusions in visual perception.

He built the first camera obscura and pinhole camera and investigated the meteorology of the rainbow and the density of the atmosphere. Various celestial phenomena (including the eclipse, twilight, and moonlight) were also examined by him. He also made investigations into refraction, catoptrics, dioptrics, spherical mirrors, and magnifying lenses.

In his treatise, Mizan al-Hikmah (Balance of Wisdom), Ibn al-Haytham discussed the density of the atmosphere and related it to altitude. He also studied atmospheric refraction. He discovered that the twilight only ceases or begins when the Sun is 19° below the horizon and attempted to measure the height of the atmosphere on that basis.

Astrophysics:

In astrophysics and the celestial mechanic’s field of physics, Ibn al-Haytham, in his Epitome of Astronomy, discovered that the heavenly bodies “were accountable to the laws of physics”.

Ibn al-Haytham’s Mizan al-Hikmah (Balance of Wisdom) covered statics, astrophysics, and celestial mechanics. He discussed the theory of attraction between masses, and it seems that he was also aware of the magnitude of the acceleration due to gravity at a distance. His Maqala fi’l-qarastun is a treatise on centers of gravity. Little is known about the work, except for what is known through the later works of al-Khazini in the 12th century. In this treatise, Ibn al-Haytham formulated the theory that the heaviness of bodies varies with their distance from the centre of the Earth.

Another treatise, Maqala fi daw al-Qamar (On the Light of the Moon), which he wrote sometime before his famous Book of Optics, was the first successful attempt at combining mathematical astronomy with physics, and the earliest attempt at applying the experimental method to astronomy and astrophysics.

He disproved the universally held opinion that the Moon reflects sunlight like a mirror and correctly concluded that it “emits light from those portions of its surface which the sun’s light strikes.”

To prove that “light is emitted from every point of the Moon’s illuminated surface”, he built an “ingenious experimental device.” According to Matthias Schramm, Ibn al-Haytham had formulated a clear conception of the relationship between an ideal mathematical model and the complex of observable phenomena; in particular, he was the first to make a systematic use of the method of varying the experimental conditions in a constant and uniform manner, in an experiment showing that the intensity of the light spot formed by the projection of the moonlight through two small apertures onto a screen diminishes constantly as one of the apertures is gradually blocked up.

Mechanics:

In the dynamics and kinematics fields of mechanics, Ibn al-Haytham’s Risala fi’l-Makan (Treatise on Place) discussed theories on the motion of a body. He maintained that a body moves perpetually unless an external force stops it or changes its direction of motion.

This was similar to the concept of inertia but was largely a hypothesis that was not verified by experimentation. The key breakthrough in classical mechanics, the introduction of frictional force, was eventually made centuries later by Galileo Galilei, and later formulated as Newton’s first law of motion.

Also in his Treatise on Place, Ibn al-Haytham disagreed with Aristotle’s view that nature abhors a void, and he thus used geometry to demonstrate that place (al-Makan) is the imagined three-dimensional void between the inner surfaces of a containing body.

Ibn al-Haytham also discovered the concept of momentum (now part of Newton’s second law of motion) around the same time as his contemporary, Avicenna (Ibn Sina).

Astronomical works – Doubts Concerning Ptolemy:
In his Al-Sukuk? ala Batlamyus, variously translated as Doubts Concerning Ptolemy or Aporias against Ptolemy, published at some time between 1025 and 1028, Ibn al-Haytham criticized many of Ptolemy’s works, including the Almagest, Planetary Hypotheses, and Optics, pointing out various contradictions he found in these works.

He considered that some of the mathematical devices Ptolemy introduced into astronomy, especially the equant, failed to satisfy the physical requirement of uniform circular motion, and wrote a scathing critique of the physical reality of Ptolemy’s astronomical system, noting the absurdity of relating actual physical motions to imaginary mathematical points, lines, and circles:

Ptolemy assumed an arrangement (hay’ a) that cannot exist, and the fact that this arrangement produces in his imagination the motions that belong to the planets does not free him from the error he committed in his assumed arrangement, for the existing motions of the planets cannot be the result of an arrangement that is impossible to exist… [F]or a man to imagine a circle in the heavens, and to imagine the planet moving in it does not bring about the planet’s motion.

Ibn al-Haytham further criticized Ptolemy’s model on other empirical, observational and experimental grounds, such as Ptolemy’s use of conjectural demonstrated theories in order to “save appearances” of certain phenomena, which Ibn al-Haytham did not approve of due to his insistence on scientific demonstration.

Unlike some later astronomers who criticized the Ptolemaic model on the grounds of being incompatible with Aristotelian natural philosophy, Ibn al-Haytham was mainly concerned with empirical observation and the internal contradictions in Ptolemy’s works.

In his Aporias against Ptolemy, Ibn al-Haytham commented on the difficulty of attaining scientific knowledge:

Truth is sought for itself [but] the truths, [he warns] are immersed in uncertainties [and the scientific authorities (such as Ptolemy, whom he greatly respected) are] not immune from error.

He held that the criticism of existing theories which dominated this book holds a special place in the growth of scientific knowledge:

Therefore, the seeker after the truth is not one who studies the writings of the ancients and, following his natural disposition, puts his trust in them, but rather the one who suspects his faith in them and questions what he gathers from them, the one who submits to argument and demonstration, and not to the sayings of a human being whose nature is fraught with all kinds of imperfection and deficiency.

Thus the duty of the man who investigates the writings of scientists, if learning the truth is his goal, is to make himself an enemy of all that he reads, and, applying his mind to the core and margins of its content, attack it from every side. He should also suspect himself as he performs his critical examination of it, so that he may avoid falling into either prejudice or leniency.

On the Configuration of the World:

In his On the Configuration of the World, despite his criticisms directed towards Ptolemy, Ibn al-Haytham continued to accept the physical reality of the geocentric model of the universe, presenting a detailed description of the physical structure of the celestial spheres in his On the Configuration of the World:

The earth as a whole is a round sphere whose center is the center of the world. It is stationary in its middle, fixed in it and not moving in any direction nor moving with any of the varieties of motion, but always at rest.

While he attempted to discover the physical reality behind Ptolemy’s mathematical model, he developed the concept of a single orb (Falak) for each component of Ptolemy’s planetary motions. This work was eventually translated into Hebrew and Latin in the 13th and 14th centuries and subsequently had an influence on astronomers such as Georg von Peuerbach during the European Middle Ages and Renaissance.

Model of the Motions of Each of the Seven Planets:

Ibn al-Haytham’s The Model of the Motions of Each of the Seven Planets, written in 1038, was a book on astronomy. The surviving manuscript of this work has only recently been discovered, with much of it still missing, hence the work has not yet been published in modern times. Following on from his Doubts on Ptolemy and The Resolution of Doubts, Ibn al-Haytham described the first non-Ptolemaic model in The Model of the Motions. His reform was not concerned with cosmology, as he developed a systematic study of celestial kinematics that was completely geometric. This, in turn, led to innovative developments in infinitesimal geometry.

His reformed empirical model was the first to reject the equant and eccentrics, separate natural philosophy from astronomy, free celestial kinematics from cosmology, and reduce physical entities to geometric entities.

The model also propounded the Earth’s rotation about its axis, and the centers of motion were geometric points without any physical significance, like Johannes Kepler’s model centuries later.

In the text, Ibn al-Haytham also describes an early version of Occam’s razor, where he employs only minimal hypotheses regarding the properties that characterize astronomical motions, as he attempts to eliminate from his planetary model the cosmological hypotheses that cannot be observed from the Earth.

Other astronomical works:

Ibn al-Haytham distinguished astrology from astronomy, and he refuted the study of astrology, due to the methods used by astrologers being conjectural rather than empirical, and also due to the views of astrologers conflicting with that of orthodox Islam.

Ibn al-Haytham also wrote a treatise entitled On the Milky Way, in which he solved problems regarding the Milky Way galaxy and parallax.

In antiquity, 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.” Ibn al-Haytham refuted this and “determined that because the Milky Way had no parallax, it was very remote from the earth and did not belong to the atmosphere.”

He wrote that if the Milky Way was located around the Earth’s atmosphere, “one must find a difference in position relative to the fixed stars.” He described two methods to determine the Milky Way’s parallax: “either when one observes the Milky Way on two different occasions from the same spot of the earth; or when one looks at it simultaneously from two distant places from the surface of the earth.”

He made the first attempt at observing and measuring the Milky Way’s parallax, and determined that since the Milky Way had no parallax, then it does not belong to the atmosphere.

In 1858, Muhammad Wali ibn Muhammad Ja’far, in his Shigarf-name, claimed that Ibn al-Haytham wrote a treatise Maratib al-sama in which he conceived of a planetary model similar to the Tychonic system where the planets orbit the Sun which in turn orbits the Earth. However, the “verification of this claim seems to be impossible”, since the treatise is not listed among the known bibliography of Ibn al-Haytham.

Mathematical works:

In mathematics, Ibn al-Haytham built on the mathematical works of Euclid and Thabit ibn Qurra. He systemized conic sections and number theory, carried out some early work on analytic geometry, and worked on “the beginnings of the link between algebra and geometry.” This, in turn, had an influence on the development of René Descartes’s geometric analysis and Isaac Newton’s calculus.

Geometry:

In geometry, Ibn al-Haytham developed analytical geometry and established a link between algebra and geometry. Ibn al-Haytham also discovered a formula for adding the first 100 natural numbers. Ibn al-Haytham used a geometric proof to prove the formula.

Ibn al-Haytham made the first attempt at proving the Euclidean parallel postulate, the fifth postulate in Euclid’s Elements, using a proof by contradiction, where he introduced the concept of motion and transformation into geometry.

He formulated the Lambert quadrilateral, which Boris Abramovich Rozenfeld names the “Ibn al-Haytham–Lambert quadrilateral”, and his attempted proof also shows similarities to Playfair’s axiom. His theorems on quadrilaterals, including the Lambert quadrilateral, were the first theorems on elliptical geometry and hyperbolic geometry.

These theorems, along with his alternative postulates, such as Playfair’s axiom, can be seen as marking the beginning of non-Euclidean geometry. His work had a considerable influence on its development among the later Persian geometers Omar Khayyám and Nasir al-Din al-Tusi, and the European geometers Witelo, Gersonides, Alfonso, John Wallis, Giovanni Girolamo Saccheri and Christopher Clavius.

In elementary geometry, Ibn al-Haytham attempted to solve the problem of squaring the circle using the area of lunes (crescent shapes) but later gave up on the impossible task. Ibn al-Haytham also tackled other problems in elementary (Euclidean) and advanced (Apollonian and Archimedean) geometry, some of which he was the first to solve.

Number theory:

His contributions to number theory include his work on perfect numbers. In his Analysis and Synthesis, Ibn al-Haytham was the first to realize that every even perfect number is of the form 2n-1(2n – 1) where 2n – 1 is prime, but he was not able to prove this result successfully (Euler later proved it in the 18th century).

Ibn al-Haytham solved problems involving congruences using what is now called Wilson’s theorem. In his Opuscula, Ibn al-Haytham considers the solution of a system of congruences and gives two general methods of solution. His first method, the canonical method, involved Wilson’s theorem, while his second method involved a version of the Chinese remainder theorem.

Other works – Influence of Melodies on the Souls of Animals:
In psychology and musicology, Ibn al-Haytham’s Treatise on the Influence of Melodies on the Souls of Animals was the earliest treatise dealing with the effects of music on animals.

In the treatise, he demonstrates how a camel’s pace could be hastened or retarded with the use of music, and shows other examples of how music can affect animal behavior and animal psychology, experimenting with horses, birds and reptiles.

Through to the 19th century, a majority of scholars in the Western world continued to believe that music was a distinctly human phenomenon, but experiments since then have vindicated Ibn al-Haytham’s view that music does indeed have an effect on animals.

Engineering:

In engineering, one account of his career as a civil engineer has him summoned to Egypt by the Fatimid Caliph, Al-Hakim bi-Amr Allah, to regulate the flooding of the Nile River. He carried out a detailed scientific study of the annual inundation of the Nile River, and he drew plans for building a dam, at the site of the modern-day Aswan Dam.

His fieldwork, however, later made him aware of the impracticality of this scheme, and he soon feigned madness so he could avoid punishment from the Caliph.

According to Al-Khazini, Ibn al-Haytham also wrote a treatise providing a description of the construction of a water clock.

Philosophy:

In early Islamic philosophy, Ibn al-Haytham’s Risala fi’l-Makan (Treatise on Place) presents a critique of Aristotle’s concept of place (topos). Aristotle’s Physics stated that the place of something is the two-dimensional boundary of the containing body that is at rest and is in contact with what it contains. Ibn al-Haytham disagreed and demonstrated that place (al-Makan) is the imagined three-dimensional void between the inner surfaces of the containing body. He showed that place was akin to space, foreshadowing René Descartes’s concept of place in the Extension in the 17th century.

Following on from his Treatise on Place, Ibn al-Haytham’s Qawl fi al-Makan (Discourse on Place) was a treatise that presents geometric demonstrations for his geometrization of place, in opposition to Aristotle’s philosophical concept of place, which Ibn al-Haytham rejected on mathematical grounds. Abd-el-Latif, a supporter of Aristotle’s philosophical view of the place, later criticized the work in Fi al-Radd ‘ala Ibn al-Haytham fi al-Makan (A refutation of Ibn al-Haytham’s place) for its geometrization of place.

Ibn al-Haytham also discussed space perception and its epistemological implications in his Book of Optics. His experimental proof of the intromission model of vision led to changes in the way the visual perception of space was understood, contrary to the previous emission theory of vision supported by Euclid and Ptolemy. In “tying the visual perception of space to prior bodily experience, Alhacen unequivocally rejected the intuitiveness of spatial perception and, therefore, the autonomy of vision. Without tangible notions of distance and size for correlation, sight can tell us next to nothing about such things.”

Theology:

Ibn al-Haytham was a devout Muslim, though it is uncertain which branch of Islam he followed. He may have been either a follower of the orthodox Ash’ari school of Sunni Islamic theology according to Ziauddin Sardar and Lawrence Bettany (and opposed to the views of the Mu’tazili school), a follower of the Mu’tazili school of Islamic theology according to Peter Edward Hodgson, or a follower of Shia Islam possibly according to A. I. Sabra.

Ibn al-Haytham wrote a work on Islamic theology, in which he discussed prophethood and developed a system of philosophical criteria to discern its false claimants in his time. He also wrote a treatise entitled Finding the Direction of Qibla by Calculation, in which he discussed finding the Qibla, where Salah prayers are directed towards, mathematically.

Ibn al-Haytham attributed his experimental scientific method and scientific skepticism to his Islamic faith. The Islamic holy book, the Qur’an, for example, places a strong emphasis on empiricism. He also believed that human beings are inherently flawed and that only God is perfect. He reasoned that to discover the truth about nature, it is necessary to eliminate human opinion and error and allow the universe to speak for itself. He wrote in his Doubts Concerning Ptolemy:

Truth is sought for its own sake Finding the truth is difficult, and the road to it is rough. For the truths are plunged in obscurity. God, however, has not preserved the scientist from error and has not safeguarded science from shortcomings and faults.

If this had been the case, scientists would not have disagreed upon any point of science. Therefore, the seeker after the truth is not one who studies the writings of the ancients and, following his natural disposition, puts his trust in them, but rather the one who suspects his faith in them and questions what he gathers from them, the one who submits to argument and demonstration, and not to the sayings of a human being whose nature is fraught with all kinds of imperfection and deficiency.

Thus the duty of the man who investigates the writings of scientists, if learning the truth is his goal, is to make himself an enemy of all that he reads, and, applying his mind to the core and margins of its content, attack it from every side. He should also suspect himself as he performs his critical examination of it, so that he may avoid falling into either prejudice or leniency.

In The Winding Motion, Ibn al-Haytham further wrote that faith (or taqlid or “imitation”) applied to prophets of Islam especially with respect to worship (Ibadah) but should not be applied to scientists (natural philosophers) investigating the material world and mathematics (the fallacy of argumentum ad verecundiam). For example, in the following comparison between the Islamic prophetic tradition and the demonstrative sciences he writes:

From the statements made by the noble Shaykh, it is clear that he believes in Ptolemy’s words in everything he says, without relying on a demonstration or calling on a proof, but by pure imitation (taqlid); that is how experts in the prophetic tradition have faith in Prophets, may the blessing of God be upon them. But it is not the way that mathematicians have faith in specialists in the demonstrative sciences.

Ibn al-Haytham described his search for truth and knowledge as a way of leading him closer to God:

I constantly sought knowledge and truth, and it became my belief that for gaining access to the effulgence and closeness to God, there is no better way than that of searching for truth and knowledge.

Works:

Ibn al-Haytham was a pioneer in many areas of science, making significant contributions in varying disciplines. His optical writings influenced many Western intellectuals such as Roger Bacon, John Pecham, Witelo, Johannes Kepler. His pioneering work on number theory, analytic geometry, and the link between algebra and geometry, also had an influence on René Descartes’s geometric analysis and Isaac Newton’s calculus.

According to medieval biographers, Ibn al-Haytham wrote more than 200 works on a wide range of subjects, of which at least 96 of his scientific works are known. Most of his works are now lost, but more than 50 of them have survived to some extent. Nearly half of his surviving works are on mathematics, 23 of them are on astronomy, and 14 of them are on optics, with a few on other subjects. Not all his surviving works have yet been studied, but some of the ones that have been given below.

Book of Optics
Analysis and Synthesis
Balance of Wisdom
Corrections to the Almagest
Discourse on Place
Exact Determination of the Pole
Exact Determination of the Meridian
Finding the Direction of Qibla by Calculation
Horizontal Sundials
Hour Lines
Doubts Concerning Ptolemy
Makala fi’l-Qarastun
On Completion of the Conics
On Seeing the Stars
On Squaring the Circle
On the Burning Sphere
On the Configuration of the World
On the Form of Eclipse
On the Light of Stars
On the Light of the Moon
On the Milky Way
On the Nature of Shadows
On the Rainbow and Halo
Opuscula
Resolution of Doubts Concerning the Almagest
Resolution of Doubts Concerning the Winding Motion
The Correction of the Operations in Astronomy
The Different Heights of the Planets
The Direction of Mecca
The Model of the Motions of Each of the Seven Planets
The Model of the Universe
The Motion of the Moon
The Ratios of Hourly Arcs to their Heights
The Winding Motion
Treatise on Light
Treatise on Place
Treatise on the Influence of Melodies on the Souls of Animals.

Abū al-Abbas

Abū al-Abbas Ahmad ibn Muhammad ibn Kathīr al-Farghani also known as Alfraganus in the West was a Muslim astronomer and one of the famous astronomers in the 9th century.

Abu’l-Abbas Ahmad ibn Muhammad ibn Kathir al-Farghani, born in Farghana, Transoxiana, was one of the most distinguished astronomers in the service of al-Mamun and his successors. He wrote, “Elements of Astronomy” (Kitab fi al-Harakat al-Samawiya wa Jawami Ilm al-Nujum i.e. the book on celestial motion and thorough science of the stars), which was translated into Latin in the 12th century and exerted great influence upon European astronomy before Regiomontanus.

He accepted Ptolemy’s theory and value of the precession but thought that it affected not only the stars but also the planets. He determined the diameter of the earth to be 6,500 miles, and. found the greatest distances and also the diameters of the planets.

Al-Farghani’s activities extended to engineering. According to Ibn Tughri Birdi, he supervised the construction of the Great Nilometer at al-Fustat (old Cairo). It was completed in 861, the year in which the Caliph al-Mutawakkil, who ordered the construction, died. But engineering was not al-Farghani’s forte, as transpires from the following story narrated by Ibn Abi Usaybi’a.

Al-Mutawakkil had entrusted the two sons of Musa ibn Shakir, Muhammad, and Ahmad, with supervising the digging of a canal named al-Ja’fari.

They delegated the work to Al-Farghani, thus deliberately ignoring a better engineer, Sind ibn Ali, whom, out of professional jealousy, they had caused to be sent to Baghdad, away from al-Mutawakkil’s court in Samarra.

The canal was to run through the new city, al-Ja’fariyya, which al-Mutawakkil had built near Samarra on the Tigris and named after himself.

Al-Farghani committed a grave error, making the beginning of the canal deeper than the rest so that not enough water would run through the length of the canal except when the Tigris was high. News of this angered the Caliph, and the two brothers were saved from severe punishment only by the gracious willingness of Sind ibn Ali to vouch for the correctness of al-Farghani’s calculations, thus risking his own welfare and possibly his life.

As had been correctly predicted by astrologers, however, al-Mutawakkil was murdered shortly before the error became apparent. The explanation given for Al-Farghani’s mistake is that being a theoretician rather than a practical engineer, he never successfully completed a construction.

The Fihrist of Ibn al-Nadim, written in 987, ascribes only two works to Al-Farghani:
(1) “The Book of Chapters, a summary of the Almagest” (Kitab al-Fusul, Ikhtiyar al-Majisti)
(2) “Book on the Construction of Sun-dials” (Kitab ‘Amal al-Rukhamat).

The Jawami, or ‘The Elements’ as we shall call it, was Al- Farghani’s best-known and most influential work. Abd al-Aziz al-Qabisi (d. 1967) wrote a commentary on it, which is preserved in the Istanbul manuscript, Aya Sofya 4832, folks. 97v-114v.

Two Latin translations followed in the 12th century. Jacob Anatoli produced a Hebrew translation of the book that served as a basis for a third Latin version, appearing in 1590, whereas Jacob Golius published a new Latin text together with the Arabic original in 1669. The influence of ‘The Elements’ on medieval Europe is clearly indicated by the presence of innumerable Latin manuscripts in European libraries.

References to it in medieval writers are many, and there is no doubt that it was greatly responsible for spreading knowledge of Ptolemaic astronomy, at least until this role was taken over by Sacrobosco’s Sphere. But even then, ‘The Elements’ of Al-Farghani continued to be used, and Sacrobosco’s Sphere was evidently indebted to it. It was from ‘The Elements’ (in Gherard’s translation) that Dante derived the astronomical knowledge displayed in the ‘Vita Nuova’ and in the ‘Convivio’.

The crater Alfraganus on the Moon is named after him.

Abbas Ibn Firnas

Abbas Ibn Firnas (1810–1887 A.D.), also known as Abbas Qasim Ibn Firnas and عباس بن فرناس (Arabic language), was a Muslim polymath: an inventor, engineer, aviator, physician, Arabic poet, and Andalusian musician. Of Berber descent, he was born in In-Rand Onda, Al-Andalus (today’s Ronda, Spain), and lived in the Emirate of Córdoba. He is known for an early attempt at aviation.

Ibn Firnas designed a water clock called Al-Maqata, devised a means of manufacturing colorless glass, he invented various glass planispheres, made corrective lenses (“reading stones”), developed a chain of rings that could be used to simulate the motions of the planets and stars, and developed a process for cutting rock crystal that allowed Spain to cease exporting quartz to Egypt to be cut.

In his house, he built a room in which spectators witnessed stars, clouds, thunder, and lightning, which were produced by mechanisms located in his basement laboratory. He also devised “some sort of metronome.”

Aviation:

He made an attempt at flight using a set of wings. The only evidence for this is an account by the Moroccan historian Ahmed Mohammed al-Maqqari (d. 1632), composed seven centuries later:

“Among other very curious experiments which he made, one is his trying to fly. He covered himself with feathers for the purpose, attached a couple of wings to his body, and, getting on an eminence, flung himself down into the air when according to the testimony of several trustworthy writers who witnessed the performance, he flew a considerable distance as if he had been a bird, but, in alighting again on the place whence he had started, his back was very much hurt, for not knowing that birds when they alight come down upon their tails, he forgot to provide himself with one. ”

Al-Maqqari is said to have used in his history works “many early sources no longer extant”, but in case of Firnas, the only one cited by him was a 9th-century poem written by Mu’min ibn Said, a court poet of Córdoba under Muhammad I (d. 886), who was acquainted with and usually critical of Ibn Firnas. The pertinent verse runs: “He flew faster than the phoenix in his flight when he dressed his body in the feathers of a vulture.”

Ibn Firnas’ attempt at glider inspired the attempt by Eilmer of Malmesbury between 1000 and 1010 in England.

As westerners teach their children about the Wright Brothers, the Islamic countries tell theirs about Ibn Firnas, a thousand years before the Wrights though his flight was not powered. The Libyans produced a postage stamp honoring him. The Iraqis built a statue in his memory on the way to Baghdad International Airport, and the Ibn Firnas Airport to the north of Baghdad is named for him.

“Ibn Firnas was the first man in history to make a scientific attempt at flying.” Philip Hitti, History of the Arabs.

The crater Ibn Firnas on the Moon is named in his honor.

Abu ‘l-Walid

Abu ‘l-Walid Muhammad ibn Ahmad ibn Rushd better known just as Ibn Rushd, and in European literature as Averroes (1126 – December 10, 1198), was an Andalusian Muslim polymath; a master of Aristotelian philosophy, Islamic philosophy, Islamic theology, and jurisprudence, logic, psychology, politics, Arabic music theory, and the sciences of medicine, astronomy, geography, mathematics, physics, and celestial mechanics.

He was born in Córdoba, Al Andalus, modern-day Spain, and died in Marrakesh, modern-day Morocco. His school of philosophy is known as Averroism. He has been described by some as the “one of the spiritual fathers of Europe,”

According to Ernest Renan, he was also called as Ibin-Ros-din, Filius Rosadis, Ibn-Rusid, Ben-Raxid, Ibn-Ruschod, Den-Reached, Aben-Rassad, Aben-Rois, Aben-Raid, Aben- Rust, Avenrosdy Avenryz, Adveroys, Benoist, Avenroyth, Averroysta, etc. “Averroès et l’Averroïsme: Essai Historique”

Biography:

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’s 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, the 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 amir Abu Yaqub Yusuf. 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 was also a student 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 mystics to an extent, the thought of Averroes was purely rationalist. Together, the three men are considered the greatest Andalusian philosophers.

In 1160, Averroes was made Qadi (judge) of Seville and he served in many court appointments in Seville, Cordoba, and Morocco during his career. At the end of the 12th century, following the Almohads conquest of Al-Andalus, his political career was ended.

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.

He devoted the rest of his life (more than 30 years) to his philosophical writings, he died in the year 1198 AD.

Works:

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.

He wrote commentaries on most of the surviving works of Aristotle. These were not based on primary sources (it is not known whether he knew Greek), but rather on Arabic translations.

There were three levels of commentary: the Jami, the Talkhis and the Tafsir which are, respectively, a simplified overview, an intermediate commentary with more critical material, and an advanced study of Aristotelian thought in a Muslim context. The terms are taken from the names of different types of commentary on the Qur’an.

It is not known whether he wrote commentaries of all three types on all the works: in most cases, only one or two commentaries survive.

He did not have access to any text of Aristotle’s Politics. As a substitute for this, he commented on Plato’s The Republic, arguing that the ideal state there described was the same as the original constitution of the Arab Caliphate, as well as the Almohad state of Ibn Tumart.

The imaginary debate between Averroes and Porphyry. Monfredo de Monte Imperiali Liber de herbis, 14th century. 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).

Al-Ghazali argued that Aristotelianism, especially as presented in the writings of Avicenna, was self-contradictory and an affront to the teachings of Islam. Averroes’ rebuttal was two-pronged: he contended both that al-Ghazali’s arguments were mistaken and that, in any case, the system of Avicenna was a distortion of genuine Aristotelianism so that al-Ghazali was aiming at the wrong target.

Other works were the Fasl al-Maqal, which argued for the legality of philosophical investigation under Islamic law, and the Kitab al-Kashf, which argued against the proofs of Islam advanced by the Ash’arite school and discussed what proofs, on the popular level, should be used instead.

Averroes is also a highly regarded legal scholar of the Maliki school. Perhaps his best-known work in this field is Bidayat al-Mujtahid wa Nihayat al-Muqtaid, a textbook of Maliki doctrine in a comparative framework.

In medicine, Averroes wrote a medical encyclopedia called Kulliyat (“Generalities”, i.e. general medicine), known in its Latin translation as College. He also made a compilation of the works of Galen (129-200) and wrote a commentary on The Law of Medicine (Qanun fi ‘t-Tibb) of Avicenna (Ibn Sina) (980-1037).

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 Martino 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. Contributions Philosophy

Giovanni di Paolo’s St. Thomas Aquinas Confounding Averroës.See also: Averroism and The Incoherence of the Incoherence

According to Averroes, there is no conflict between religion and philosophy, rather that they are different ways of reaching the same truth. He believed in the eternity of the universe. He also held that the soul is divided into two parts, one individual and one divine; while the individual soul is not eternal, all humans at the basic level share one and the same divine soul.

Averroes has two kinds of Knowledge of Truth. The first being his knowledge of the truth of religion being based in faith and thus could not be tested, nor did it require training to understand. The second knowledge of truth is philosophy, which was reserved for an elite few who had the intellectual capacity to undertake this study.

The concept of “existence precedes essence”, a key foundational concept of existentialism can also be found in the works of Averroes, as a reaction to Ibn Sina’s concept of “essence precedes existence”. Averroes’s most famous original philosophical work was The Incoherence of the Incoherence, a rebuttal to Al-Ghazali’s The Incoherence of the Philosophers.

In medieval Europe, his school of philosophy known as Averroism exerted a strong influence on Jewish philosophers such as Gersonides and Maimonides and was opposed by Christian philosophers such as Thomas Aquinas.

Astronomy:

At the age of 25, Averroes conducted astronomical observations near Marrakech, Morocco, during which he discovered a previously unobserved star.

In astronomical theory, Averroes rejected the eccentric deferents introduced by Ptolemy. He rejected the Ptolemaic model and instead argued for a strictly concentric model of the universe. He wrote the following criticism on the Ptolemaic model of planetary motion:

“To assert the existence of an eccentric sphere or an epicyclic sphere is contrary to nature. The astronomy of our time offers no truth, but only agrees with the calculations and not with what exists.”

Averroes also argued that the Moon is opaque and obscure, and has some parts which are thicker than others, with the thicker parts receiving more light from the Sun than the thinner parts of the Moon. He also gave one of the first descriptions of sunspots.

Celestial mechanics:

In celestial mechanics, while discussing the celestial spheres, Averroes rejected John Philoponus’ ‘anti-Aristotelian’ solution to his refutation of Aristotelian celestial dynamics, and instead restored Aristotle’s law of motion by adopting the ‘hidden variable’ approach to resolving apparent refutations of parametric laws that posits a previously unaccounted variable and its value(s) for some parameter, thereby modifying the predicted value of the subject variable. For, he posited a non-gravitational, previously unaccounted, inherent resistance to motion, as hidden within the celestial spheres.

This was a non-gravitational inherent resistance to motion of superlunary quintessential matter, whereby R > 0 even when there is neither any gravitational nor any media resistance, to motion.

Hence, in refuting the prediction of Aristotelian celestial dynamics:

[ (i) v a F/R & (ii) F > 0 & (iii) R = 0 ] entail v is infinite
the alternative logic of Averroes’ solution was to reject its third premise “R = 0” instead of rejecting its first premise as Philoponus had.

Thus Averroes most significantly revised Aristotle’s law of motion “v a F/R” into “v a F/M” for the case of celestial motion with his auxiliary theory of what may be called celestial inertia M, whereby R = M > 0. But Averroes restricted inertia to celestial bodies and denied sublunar bodies have any inherent resistance to motion other than their gravitational (or levitational) inherent resistance to violent motion, just as in Aristotle’s original sublunar physics.

However, Thomas Aquinas, also a student of Aristotelianism, rejected this denial of sublunar inertia and extended Averroes’ innovation in the celestial physics of the spheres to all sublunar bodies. He posited all bodies universally have a non-gravitational inherent resistance to motion constituted by their magnitude or mass. In his Systeme du Monde, the pioneering historian of medieval science Pierre Duhem stated:

“For the first time, we have seen human reason distinguish two elements in a heavy body: the motive force, that is, in modern terms, the weight; and the moving thing, the corpus quantum, or as we say today, the mass.

For the first time we have seen the notion of mass being introduced in mechanics, and being introduced as equivalent to what remains in a body when one has suppressed all forms in order to leave only the prime matter quantified by its determined dimensions.

Saint Thomas Aquinas’s analysis, completing Ibn Bajja’s, came to distinguish three notions in a falling body: the weight, the mass, and the resistance of the medium, about which physics will reason during the modern era. This mass, this quantified body, resists the motor attempting to transport it from one place to another, stated Thomas Aquinas.”

Some five centuries after Averroes’ and Aquinas’ innovations, it was Johannes Kepler who first dubbed this non-gravitational inherent resistance to motion in all bodies universally ‘inertia’. Hence the crucial notion of 17th century early classical mechanics of a resistant force of inertia inherent in all bodies was born in the heavens of medieval astrophysics, in the Aristotelian physics of the celestial spheres, rather than in terrestrial physics or in experiments.

However, having discounted the possibility of any resistance due to a contrary inclination to move in an opposite direction or due to any external resistance, in concluding their impetus was therefore not corrupted by any resistance, Jean Buridan also discounted any inherent resistance to motion in the form of an inclination to rest within the spheres themselves, such as the inertia posited by Averroes and Aquinas.

For otherwise, that resistance would destroy their impetus, as the anti-Duhemian historian of science, Annaliese Maier maintained the Parisian impetus dynamicists were forced to conclude, because of their belief in an inherent inclinations quietem (tendency to rest) or inertia in all bodies. But in fact, contrary to that inertial variant of Aristotelian dynamics, according to Buridan, prime matter does not resist motion.

Law and jurisprudence:

As a Qadi (judge), Averroes wrote the Bidayat al-Mujtahid wa Nihayat al-Muqtasid, a Maliki legal treatise dealing with Sharia (law) and Fiqh (jurisprudence) which, according to Al-Dhahabi in the 13th century, was considered the best treatise was ever written on the subject. Averroes’s summary of the opinions (fatwa) of previous Islamic jurists on a variety of issues has continued to influence Islamic scholars to the present day, notably Javed Ahmad Ghamidi. While Averroes himself claimed that women in Islam were equal to men in all respects and possessed equal capacities to shine in peace and in war, he summarized the opinions of previous jurists and Imams on the status of women’s testimony in Islam as follows:

“There is a general consensus among the jurists that in financial transactions a case stands proven by the testimony of a just man and two women on the basis of the verse: ‘If two men cannot be found then one man and two women from among those whom you deem appropriate as witnesses’. However; in cases of Hudud, there is a difference of opinion among our jurists. The majority say that in these affairs the testimony of women is in no way acceptable whether they testify alongside a male witness or do so alone. The Zahiris, on the contrary, maintain that if they are more than one and are accompanied by a male witness, then owing to the apparent meaning of the verse their testimony will be acceptable in all affairs. Imam Abu Hanifah is of the opinion that except in cases of Hudud and in financial transactions their testimony is acceptable in bodily affairs like divorce, marriage, slave-emancipation and Raju‘ [restitution of conjugal rights]. Imam Malik is of the view that their testimony is not acceptable in bodily affairs. There is however a difference of opinion among the companions of Imam Malik regarding bodily affairs which relate to wealth like advocacy and will-testaments which do not specifically relate to wealth. Consequently, Ash-hab and Ibn Majishun accept two male witnesses only in these affairs, while Malik Ibn Qasim and Ibn Wahab two female and a male witness are acceptable. As far as the matter of women as sole witnesses are concerned, the majority accept it only in bodily affairs, about which men can have no information in ordinary circumstances like the physical handicaps of women and the crying of a baby at birth.”

He also discussed Islamic economic jurisprudence, particularly the concept of Riba (usury). He reported that Ibn ‘Abbas, a sahaba (companion) of Muhammad, did not accept Riba al-Fadl (interest in excess) because, according to him, the Prophet Muhammad had clarified that there was no Riba except in credit. He also discussed the role of Islamic criminal jurisprudence in the Islamic dietary laws in regard to the consumption of alcohol. He stated that physical punishment for alcoholic consumption was not originally established as part of the Sharia in Muhammad’s time but was later decided by the Shura (consultive council) of the Rashidun Caliphate. He wrote:

“The general opinion in this regard is based on the consultation of ‘Umar (RTA) with the members of his Shura. The session of this Shura took place during his period when people started indulging in this habit more frequently. ‘Ali (RTA) opined that, by analogy with the punishment of Qadhf, its punishment should also be fixed at eighty stripes. It is said that while presenting his arguments, he had remarked: ‘When he [ the criminal ] drinks, he will get intoxicated and once he gets intoxicated, he will utter nonsense; and once he starts uttering nonsense, he will falsely accuse other people’.”

Logic:

Averroes was the last major Muslim logician from Al-Andalus. He is known for writing the most elaborate commentaries on Aristotelian logic.

Medicine:

As a physician, Averroes wrote twenty treatises on Arabic medicine, including a seven-volume medical encyclopedia entitled Kitabu’l Kulliyat fi al-Tibb (General Rules of Medicine), better known as College in Latin.

This encyclopedic work was completed at some time before 1162 and elaborated on physiology, general pathology, diagnosis, materia medica, hygiene, and general therapeutics. He argued that no one can suffer from smallpox twice, and fully understood the function of the retina.

He improved on Alhazen’s Book of Optics (1021) which, though providing a largely correct optical theory on vision, incorrectly assumed the lens of the eye to be the organ of sight. Averroes corrected this by showing that sight is the function of the retina.

His College was largely overshadowed by the earlier medical encyclopedias, Continents by Muhammad ibn Zakariya ar-Razi (Rhazes) and The Canon of Medicine by Ibn Sina (Avicenna). As a result, Averroes’ fame as a physician was eclipsed by his own fame as a philosopher.

His Kulliyat was translated into Latin by the Jewish translator Bonacosa in the late 13th century and again by Syphorien Champier in circa 1537, and it was also translated into Hebrew twice. Max Meyerhof notes that the prototypes for the physician-philosophers that predominated in Spain were “Ibn Zuhr (Avenzoar) and Averroes (Averroes)”.

Averroes discussed the topic of human dissection and autopsy. Although he never undertook human dissection, he was aware of it being carried out by some of his contemporaries, such as Ibn Zuhr (Avenzoar), and appears to have supported the practice. Averroes stated that the “practice of dissection strengthens the faith” due to his view of the human body as “the remarkable handiwork of God in his creation.” Despite his criticism of Al-Ghazali’s theological views, Averroes agreed with him on the issue of anatomy and dissection and wrote.

“Whoever has been occupied with the science of anatomy/dissection (Tashrfh) has increased his belief in God.”

In urology, Averroes identified the issues of sexual dysfunction and erectile dysfunction and was among the first to prescribe medication for the treatment of these problems. He used several methods of therapy for this issue, including the single-drug method where a tested drug is prescribed, and a “combination method of either a drug or food.” Most of these drugs were oral medication, though a few patients were also treated through topical or transurethral means.

In neurology and neuroscience, Averroes suggested the existence of Parkinson’s disease, and in ophthalmology and optics, he was the first to attribute photoreceptor properties to the retina. In his College, he was also the first to suggest that the principal organ of sight might be the arachnoid membrane (Aranea). His work led to much discussion in 16th century Europe over whether the principal organ of sight is the traditional Galenic crystalline humour or the Averroist Aranea, which in turn led to the discovery that the retina is the principal organ of sight.

Physics:

In Averroes’ commentary on Aristotle’s Physics, he commented on the theory of motion proposed by Ibn Bajjah (Avempace) in Text 71 and also made his own contributions to physics, particularly mechanics. Averroes was the first to define and measure force as “the rate at which work is done in changing the kinetic condition of a material body” and the first to correctly argue “that the effect and measure of force change in the kinetic condition of a materially resistant mass.”

It seems he was also the first to introduce the notion that bodies have a (non-gravitational) inherent resistance to motion into physics, subsequently first dubbed ‘inertia’ by Johannes Kepler. But he only attributed it to the superlunary celestial spheres, and in order to explain why they do not move with infinite speed as was predicted by the application of Aristotle’s general law of motion v a F/R to celestial motion, given the assumption that the spheres have movers and thus F > 0, but no resistance to their motion, whereby R = 0.

John Philoponus had earlier rejected Aristotle’s theory of motion because of this celestial empirical refutation in favour of his alternative theory v a F – R that avoided it because v is finite even when R = 0 and when F > 0 and is finite. But contra Philoponus, Averroes restored it by positing inertia instead, whereby R > 0 even in the absence of any external resistance to motion and of any inherent gravitational resistance, as in the quintessential heavens in Aristotelian cosmology.

But Averroes denied sublunar bodies have inertia, and it was Thomas Aquinas, also a student of Aristotelianism, who extended this inherent force to terrestrial bodies as well, thus also rejecting Aristotle’s prediction that the speed of gravitational fall of all bodies in a vacuum would be infinite because there would be no resistance to motion in the absence of an external resistant medium (i.e. R = 0). For Aristotle had assumed the only inherent resistance to motion in bodies is that of gravity, without which bodies would not inherently resist any motion, and which does not resist gravitational (i.e. ‘natural’) motion where it acts as the motor rather than as a brake as it does in violent motion.

The Averroes-Aquinas notion of inertia was eventually adopted by Kepler, but not by scholastic Aristotelian impetus dynamics nor Galileo Galilei who maintained like Jean Buridan, for example, that prime matter does not inherently resist any motion and so is indifferent to motion or rest. It eventually became the central concept of Newton’s dynamics in its notion of the inherent force of inertia in all bodies, with the minor revision that the force of inertia resists all motion except for uniform straight motion, a purely fictitious ideal motion whose perseverance it would cause.

But Newton’s inherent force of inertia resists all actual motion, given it is all accelerated motion in the Newtonian cosmos populated by many gravitationally attractive massive bodies. Thus on this analysis, Averroes is creditable with one of the two most crucial innovations in the history of the development of Aristotelian dynamics into Newtonian dynamics, namely its two auxiliary notions of the force of impetus and of the force of inertia.

Politics:

Averroes did not have access to any text of Aristotle’s Politics. As a substitute for this, he commented on Plato’s The Republic, arguing that the ideal state there described was the same as the original constitution of the Islamic Caliphate, as well as the Almohad state of Ibn Tumart. He also believed that a wise philosopher should be commander and chief of a nation.

Averroes also claimed that women were equal to men in all respects and possessed equal capacities to shine in peace and in war, citing examples of female warriors among the Arabs, Greeks, and Africans to support his case. In Muslim history, examples of notable female Muslims who fought as soldiers or generals included Nusaybah Bint kab Al Maziniyyah, Aisha, Kahula and Wafeira, and Um Umarah.

Psychology:

Chad Hillier writes the following on Averroes’s contributions to psychology, there is evidence of some evolution in Averroes’s thought on the intellect, notably in his Middle Commentary on De Anima where he combines the positions of Alexander and Themistius for his doctrine on the material intellect and in his Long Commentary and the Tahafut where Averroes rejected Alexander and endorsed Themistius’ position that “material intellect is a single incorporeal eternal substance that becomes attached to the imaginative faculties of individual humans.” Thus, the human soul is a separate substance ontologically identical with the active intellect; and when this active intellect is embodied in an individual human it is the material intellect.

The material intellect is analogous to prime matter, in that it is pure potentiality able to receive universal forms. As such, the human mind is a composite of the material intellect and the passive intellect, which is the third element of the intellect. The passive intellect is identified with the imagination, which, as noted above, is the sense-connected finite and passive faculty that receives particular sensual forms.

When the material intellect is actualized by information received, it is described as the speculative (habitual) intellect. As the speculative intellect moves towards perfection, having the active intellect as an object of thought, it becomes the acquired intellect. In that, it is aided by the active intellect, perceived in the way Aristotle had taught, to acquire intelligible thoughts.

The idea of the soul’s perfection occurring through having the active intellect as a greater object of thought is introduced elsewhere, and its application to religious doctrine is seen. In the Tahafut, Averroes speaks of the soul as a faculty that comes to resemble the focus of its intention, and when its attention focuses more upon eternal and universal knowledge, it becomes more like the eternal and universal. As such, when the soul perfects itself, it becomes like our intellect.

Averroes succeeded in providing an explanation of the human soul and intellect that did not involve an immediate transcendent agent. This opposed the explanations found among the Neoplatonists, allowing a further argument for rejecting of Neoplatonic emanation theories. Even so, notes Davidson, Averroes’s theory of the material intellect was something foreign to Aristotle.

Significance:

Averroes, detail of the fresco The School of Athens by Raphael the West, Averroes is most famous for commentaries on Aristotle’s works, most of which had been inaccessible to Latin Europe during the Early Middle Ages.

Before 1100 only a few of Aristotle’s logical works had been translated into Latin by Boethius, although the entire extant Greek corpus was known in Byzantium.

After Latin translations of Aristotle’s other works from Greek and Arabic were made in the 12th and 13th centuries, Aristotle became more influential on medieval European philosophy. Averroes’ commentaries on Aristotle contributed to his growing influence in the medieval West.

In medieval Europe, Averroes’ school of philosophy, known as Averroism, exerted a strong influence on Christian philosophers such as Thomas Aquinas and Jewish philosophers such as Gersonides and Maimonides.

Despite negative reactions from Jewish Talmudists and the Christian clergy, Averroes’ writings were taught at the University of Paris and other medieval universities, and Averroism remained the dominant school of thought in Europe through to the 16th century.

Averroes’ argument in The Decisive Treatise provided a justification for the emancipation of science and philosophy from official Ash’ari theology, thus Averroism has been regarded as a precursor to modern secularism.

George Sarton, the father of the history of science, writes:

“Averroes was great because of the tremendous stir he made in the minds of men for centuries. A history of Averroism would include up to the end of the sixteenth-century, a period of four centuries which would perhaps deserve as much as any other to be called the Middle Ages, for it was the real transition between ancient and modern methods.”

Averroes’s work on Aristotle spans almost three decades, and he wrote commentaries on almost all of Aristotle’s work except for Aristotle’s Politics, to which he did not have access.

Averroes’ philosophical works had less influence on the medieval and early modern Islamic world than the contemporaneous Latin Christian world, as indicated by the fact many of them work did not survive in the original Arabic but rather in Latin and Hebrew translation. However, his works on specifically Islamic topics such as fiqh (Islamic law), which were not translated into Latin, naturally influenced the Islamic world rather than the West. His death coincides with a change in the culture of Al-Andalus.

In his work Fasl al-Maqal (translated a. o. as The Decisive Treatise), he stresses the importance of analytical thinking as a prerequisite to interpret the Qur’an; this is in contrast to orthodox Ash’ari theology, where the emphasis is less on analytical thinking but on extensive knowledge of sources other than the Qur’an, i.e. the hadith.

Hebrew translations of his work also had a lasting impact on Jewish philosophy, in particular, Gersonides, who wrote supercommentaries on many of the works. In the Christian world, his ideas were assimilated by Siger of Brabant and Thomas Aquinas and others (especially in the University of Paris) within the Christian scholastic tradition which valued Aristotelian logic.

Famous scholastics such as Aquinas believed him to be so important they did not refer to him by name, simply calling him “The Commentator” and calling Aristotle “The Philosopher.” Averroes’s treatise on Plato’s Republic has played a major role in both the transmission and the adaptation of the Platonic tradition in the West. It has been a primary source in medieval political philosophy.

On the other hand, he was feared by many Christian theologians, who accused him of advocating a “double truth” and denying orthodox doctrines such as individual immortality, and underground mythology grew up stigmatizing him as the ultimate unbeliever; these accusations were largely based on misunderstandings of his work.

A later importation of Averroism into Europe is associated with the University of Padua in the early Renaissance, important names being Zabarella, Cremonini, and Niphus.

Cultural influences:

Commentarium magnum Averrois in Aristotelis De Anima Libros. French manuscript, third quarter of the 13th century reflecting the respect which medieval European scholars paid to him, Averroes is named by Dante in The Divine Comedy with the great pagan philosophers whose spirits dwell in “the place that favor owes to fame” in Limbo.

Averroes appears in a short story by Jorge Luis Borges, entitled “Averroes’s Search”, in which he is portrayed trying to find the meanings of the words tragedy and comedy. He is briefly mentioned in the novel Ulysses by James Joyce alongside Maimonides. He appears to be waiting outside the walls of the ancient city of Cordoba in Alamgir Hashmi’s poem In Cordoba. He is also the main character in Destiny, a Youssef Chahine film. The Muslim pop musician Kareem Salama composed and performed a song in 2007 titled Aristotle and Averroes.

Averroes is also the title of a play called “The Gladius and The Rose”, written by Tunisian writer Mohamed Ghozzi, and which had the first price in the theater festival in Charjah in 1999.

The asteroid “8318 Averroes” was named in his honor.

A movie depicting the life and times of Averroes was released in 1998, titled Destiny (1997 film).

Abu Abdallah

Abu Abdallah Muhammad ibn Jabir ibn Sinan ar-Raqqi al-Harrani as-Sabi al-Batani. Latinized as Albategnius, Albategni or Albatenius was an Arab astronomer, astrologer, and mathematician, born in Harran near Urfa, which is now in Turkey. His epithet as-Sabi suggests that among his ancestry were members of the Sabian sect; however, his full name affirms that he was Muslim.

Astronomy:

One of his best-known achievements in astronomy was the determination of the solar year as being 365 days, 5 hours, 46 minutes and 24 seconds.

His work, the Zij influenced great European astronomers like Tycho Brahe, Johannes Kepler, etc. Nicholas Copernicus repeated what Al-Battani wrote nearly 700 years before him as the Zij was translated into Latin thrice.

The modern world has paid him homage and named a region of the moon Albategnius after him.

Al Battani worked in Syria, at ar-Raqqah and at Damascus, where he died.

He was able to correct some of Ptolemy’s results and compiled new tables of the Sun and Moon, long accepted as authoritative, discovered the movement of the Sun’s apogee, treated the division of the celestial sphere, and introduced, probably independently of the 5th-century Indian astronomer Aryabhata, the use of sines in calculation, and partially that of tangents, forming the basis of modern trigonometry.

He also calculated the values for the precession of the equinoxes (54.5″ per year, or 1° in 66 years) and the inclination of Earth’s axis (23° 35′). He used a uniform rate for precession in his tables, choosing not to adopt the theory of trepidation attributed to his colleague Thabit ibn Qurra.

His most important work is his zij, or set of astronomical tables, known as al-Zij al-Sabi with 57 chapters, which by way of Latin translation as De Motu Stellarum by Plato Tiburtinus (Plato of Tivoli) in 1116 (printed 1537 by Melanchthon, annotated by Regiomontanus), had a great influence on European astronomy.

The zij is based on Ptolemy’s theory, showing little Indian influence. A reprint appeared at Bologna in 1645. Plato’s original manuscript is preserved at the Vatican, and the Escorial Library possesses in the manuscript a treatise by Al Battani on astronomical chronology.

During his observations for his improved tables of the Sun and the Moon, he discovered that the direction of the Sun’s eccentric was changing. His times for the new moon, lengths for the solar year and sidereal year, prediction of eclipses, and work on the phenomenon of parallax carried astronomers “to the verge of relativity and the space age.”

Copernicus mentioned his indebtedness to Al-Battani and quoted him, in the book that initiated the Copernican Revolution, the De Revolutionibus Orbium Coelestium.

Mathematics:

In mathematics, Battani produced a number of trigonometrical relationships:

He also used al-Marwazi’s idea of tangents (“shadows”) to develop equations for calculating tangents and cotangents, compiling tables of them. He also discovered the reciprocal functions of secant and cosecant and produced the first table of cosecants, which he referred to as a “table of shadows” (in reference to the shadow of a gnomon), for each degree from 1° to 90°.

Honors

The crater Albategnius on the Moon is named after him.

In the fictional Star Trek universe, the Excelsior-class starship USS Al-Batani [sic] NCC-42995, mentioned on Star Trek: Voyager as Kathryn Janeway’s first deep-space assignment was named for him.

The Doctor Who novel Night of the Humans features a solar system called Battani 045.

Ibn Rushd

Ibn Rushd better known in European literature as Averroes (1126 December 10, 1198), was an Andalusian Muslim polymath; a master of Aristotelian philosophy, Islamic philosophy, Islamic theology, and jurisprudence, logic, psychology, politics, Arabic music theory, and the sciences of medicine, astronomy, geography, mathematics, physics, and celestial mechanics. He was born in Córdoba, Al Andalus, modern-day Spain, and died in Marrakesh, modern-day Morocco. His school of philosophy is known as Averroism. He has been described by some as the “one of the spiritual fathers of Europe,”

Averroes is a Latinate distortion of the actual Arab name Ibn Rushd.

Biography:

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’s 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 amir Abu Yaqub Yusuf. 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 was also a student 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 mystics to an extent, the thought of Averroes was purely rationalist. Together, the three men are considered the greatest Andalusian philosophers.

In 1160, Averroes was made Qadi (judge) of Seville and he served in many court appointments in Seville, Cordoba, and Morocco during his career. At the end of the 12th century, following the Almohads conquest of Al-Andalus, his political career was ended.

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. He devoted the rest of his life (more than 30 years) to his philosophical writings, he died in the year 1198 AD.

Works:

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.

He wrote commentaries on most of the surviving works of Aristotle. These were not based on primary sources (it is not known whether he knew Greek), but rather on Arabic translations. There were three levels of commentary: the Jami, the Talkhis and the Tafsir which are, respectively, a simplified overview, an intermediate commentary with more critical material, and an advanced study of Aristotelian thought in a Muslim context. The terms are taken from the names of different types of commentary on the Qur’an.

It is not known whether he wrote commentaries of all three types on all the works: in most cases, only one or two commentaries survive.

He did not have access to any text of Aristotle’s Politics. As a substitute for this, he commented on Plato’s The Republic, arguing that the ideal state there described was the same as the original constitution of the Arab Caliphate, as well as the Almohad state of Ibn Tumart.

The imaginary debate between Averroes and Porphyry. Monfredo de Monte Imperiali Liber de herbis, 14th century. 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). Al-Ghazali argued that Aristotelianism, especially as presented in the writings of Avicenna, was self-contradictory and an affront to the teachings of Islam.

Averroes’ rebuttal was two-pronged: he contended both that al-Ghazali’s arguments were mistaken and that, in any case, the system of Avicenna was a distortion of genuine Aristotelianism so that al-Ghazali was aiming at the wrong target. Other works were the Fasl al-Maqal, which argued for the legality of philosophical investigation under Islamic law, and the Kitab al-Kashf, which argued against the proofs of Islam advanced by the Ash’arite school and discussed what proofs, on the popular level, should be used instead.

Averroes is also a highly regarded legal scholar of the Maliki school. Perhaps his best-known work in this field is Bidayat al-Mujtahid wa Nihayat al-Muqtaid, a textbook of Maliki doctrine in a comparative framework.

In medicine, Averroes wrote a medical encyclopedia called Kulliyat (“Generalities”, i.e. general medicine), known in its Latin translation as College. He also made a compilation of the works of Galen (129-200) and wrote a commentary on The Law of Medicine (Qanun fi ‘t-Tibb) of Avicenna (Ibn Sina) (980-1037).

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 Martino 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.

Contributions
Philosophy

Giovanni di Paolo’s St. Thomas Aquinas Confounding Averroës.See also: Averroism and The Incoherence of the Incoherence

According to Averroes, there is no conflict between religion and philosophy, rather that they are different ways of reaching the same truth.

He believed in the eternity of the universe. He also held that the soul is divided into two parts, one individual and one divine; while the individual soul is not eternal, all humans at the basic level share one and the same divine soul. Averroes has two kinds of Knowledge of Truth. The first being his knowledge of the truth of religion being based in faith and thus could not be tested, nor did it require training to understand.

The second knowledge of truth is philosophy, which was reserved for an elite few who had the intellectual capacity to undertake this study.

The concept of “existence precedes essence”, a key foundational concept of existentialism can also be found in the works of Averroes, as a reaction to Ibn Sina’s concept of “essence precedes existence”.

Averroes’s most famous original philosophical work was The Incoherence of the Incoherence, a rebuttal to Al-Ghazali’s The Incoherence of the Philosophers. In medieval Europe, his school of philosophy known as Averroism exerted a strong influence on Jewish philosophers such as Gersonides and Maimonides and was opposed by Christian philosophers such as Thomas Aquinas.

Astronomy:

At the age of 25, Averroes conducted astronomical observations near Marrakech, Morocco, during which he discovered a previously unobserved star.

In astronomical theory, Averroes rejected the eccentric deferents introduced by Ptolemy. He rejected the Ptolemaic model and instead argued for a strictly concentric model of the universe. He wrote the following criticism on the Ptolemaic model of planetary motion:

“To assert the existence of an eccentric sphere or an epicyclic sphere is contrary to nature. The astronomy of our time offers no truth, but only agrees with the calculations and not with what exists.”

Averroes also argued that the Moon is opaque and obscure, and has some parts which are thicker than others, with the thicker parts receiving more light from the Sun than the thinner parts of the Moon. He also gave one of the first descriptions of sunspots.

Celestial mechanics:

In celestial mechanics, while discussing the celestial spheres, Averroes rejected John Philoponus’ ‘anti-Aristotelian’ solution to his refutation of Aristotelian celestial dynamics, and instead restored Aristotle’s law of motion by adopting the ‘hidden variable’ approach to resolving apparent refutations of parametric laws that posits a previously unaccounted variable and its value(s) for some parameter, thereby modifying the predicted value of the subject variable.

For, he posited a non-gravitational, previously unaccounted, inherent resistance to motion, as hidden within the celestial spheres. This was a non-gravitational inherent resistance to motion of superlunary quintessential matter, whereby R > 0 even when there is neither any gravitational nor any media resistance, to motion.

Hence, in refuting the prediction of Aristotelian celestial dynamics:

[ (i) v a F/R & (ii) F > 0 & (iii) R = 0 ] entail v is infinite
the alternative logic of Averroes’ solution was to reject its third premise “R = 0” instead of rejecting its first premise as Philoponus had.

Thus Averroes most significantly revised Aristotle’s law of motion “v a F/R” into “v a F/M” for the case of celestial motion with his auxiliary theory of what may be called celestial inertia M, whereby R = M > 0. But Averroes restricted inertia to celestial bodies and denied sublunar bodies have any inherent resistance to motion other than their gravitational (or levitational) inherent resistance to violent motion, just as in Aristotle’s original sublunar physics.

However, Thomas Aquinas, also a student of Aristotelianism, rejected this denial of sublunar inertia and extended Averroes’ innovation in the celestial physics of the spheres to all sublunar bodies. He posited all bodies universally have a non-gravitational inherent resistance to motion constituted by their magnitude or mass. In his Systeme du Monde, the pioneering historian of medieval science Pierre Duhem stated:

“For the first time, we have seen human reason distinguish two elements in a heavy body: the motive force, that is, in modern terms, the weight; and the moving thing, the corpus quantum, or as we say today, the mass.

For the first time we have seen the notion of mass being introduced in mechanics, and being introduced as equivalent to what remains in a body when one has suppressed all forms in order to leave only the prime matter quantified by its determined dimensions.

Saint Thomas Aquinas’s analysis, completing Ibn Bajja’s, came to distinguish three notions in a falling body: the weight, the mass, and the resistance of the medium, about which physics will reason during the modern era. This mass, this quantified body, resists the motor attempting to transport it from one place to another, stated Thomas Aquinas.”

Some five centuries after Averroes’ and Aquinas’ innovations, it was Johannes Kepler who first dubbed this non-gravitational inherent resistance to motion in all bodies universally ‘inertia’. Hence the crucial notion of 17th century early classical mechanics of a resistant force of inertia inherent in all bodies was born in the heavens of medieval astrophysics, in the Aristotelian physics of the celestial spheres, rather than in terrestrial physics or in experiments.

However, having discounted the possibility of any resistance due to a contrary inclination to move in an opposite direction or due to any external resistance, in concluding their impetus was therefore not corrupted by any resistance, Jean Buridan also discounted any inherent resistance to motion in the form of an inclination to rest within the spheres themselves, such as the inertia posited by Averroes and Aquinas.

For otherwise, that resistance would destroy their impetus, as the anti-Duhemian historian of science, Annaliese Maier maintained the Parisian impetus dynamicists were forced to conclude, because of their belief in an inherent inclination quietism (tendency to rest) or inertia in all bodies. But in fact, contrary to that inertial variant of Aristotelian dynamics, according to Buridan, prime matter does not resist motion.

Law and jurisprudence:

As a Qadi (judge), Averroes wrote the Bidayat al-Mujtahid wa Nihayat al-Muqtasid, a Maliki legal treatise dealing with Sharia (law) and Fiqh (jurisprudence) which, according to Al-Dhahabi in the 13th century, was considered the best treatise was ever written on the subject.

Averroes’s summary of the opinions (fatwa) of previous Islamic jurists on a variety of issues has continued to influence Islamic scholars to the present day, notably Javed Ahmad Ghamidi. While Averroes himself claimed that women in Islam were equal to men in all respects and possessed equal capacities to shine in peace and in war, he summarized the opinions of previous jurists and Imams on the status of women’s testimony in Islam as follows:

“There is a general consensus among the jurists that in financial transactions a case stands proven by the testimony of a just man and two women on the basis of the verse: ‘If two men cannot be found then one man and two women from among those whom you deem appropriate as witnesses’. However; in cases of Hudud, there is a difference of opinion among our jurists. The majority say that in these affairs the testimony of women is in no way acceptable whether they testify alongside a male witness or do so alone.

The Zahiris, on the contrary, maintain that if they are more than one and are accompanied by a male witness, then owing to the apparent meaning of the verse their testimony will be acceptable in all affairs. Imam Abu Hanifah is of the opinion that except in cases of Hudud and in financial transactions their testimony is acceptable in bodily affairs like divorce, marriage, slave-emancipation and Raju‘ [restitution of conjugal rights].

Imam Malik is of the view that their testimony is not acceptable in bodily affairs. There is however a difference of opinion among the companions of Imam Malik regarding bodily affairs which relate to wealth like advocacy and will-testaments which do not specifically relate to wealth.

Consequently, Ash-hab and Ibn Majishun accept two male witnesses only in these affairs, while Malik Ibn Qasim and Ibn Wahab two female and a male witness are acceptable. As far as the matter of women as sole witnesses is concerned, the majority accept it only in bodily affairs, about which men can have no information in ordinary circumstances like the physical handicaps of women and the crying of a baby at birth.”

He also discussed Islamic economic jurisprudence, particularly the concept of Riba (usury). He reported that Ibn ‘Abbas, a sahaba (companion) of Muhammad, did not accept Riba al-Fadl (interest in excess) because, according to him, the Prophet Muhammad had clarified that there was no Riba except in credit.

He also discussed the role of Islamic criminal jurisprudence in Islamic dietary laws in regard to the consumption of alcohol. He stated that physical punishment for alcoholic consumption was not originally established as part of the Sharia in Muhammad’s time but was later decided by the Shura (consultive council) of the Rashidun Caliphate. He wrote:

“The general opinion in this regard is based on the consultation of ‘Umar (RTA) with the members of his Shura. The session of this Shura took place during his period when people started indulging in this habit more frequently. ‘Ali (RTA) opined that, by analogy with the punishment of Qadhf, its punishment should also be fixed at eighty stripes. It is said that while presenting his arguments, he had remarked: ‘When he [–the criminal –] drinks, he will get intoxicated and once he gets intoxicated, he will utter nonsense; and once he starts uttering nonsense, he will falsely accuse other people’.”

Logic:
Averroes was the last major Muslim logician from Al-Andalus. He is known for writing the most elaborate commentaries on Aristotelian logic.

Medicine:

As a physician, Averroes wrote twenty treatises on Arabic medicine, including a seven-volume medical encyclopedia entitled Kitabu’l Kulliyat fi al-Tibb (General Rules of Medicine), better known as College in Latin. This encyclopedic work was completed at some time before 1162 and elaborated on physiology, general pathology, diagnosis, materia medica, hygiene and general therapeutics. He argued that no one can suffer from smallpox twice, and fully understood the function of the retina.

He improved on Alhazen’s Book of Optics (1021) which, though providing a largely correct optical theory on vision, incorrectly assumed the lens of the eye to be the organ of sight. Averroes corrected this by showing that sight is the function of the retina.

His College was largely overshadowed by the earlier medical encyclopedias, Continents by Muhammad ibn Zakariya ar-Razi (Rhazes) and The Canon of Medicine by Ibn Sina (Avicenna). As a result, Averroes’ fame as a physician was eclipsed by his own fame as a philosopher.

His Kulliyat was translated into Latin by the Jewish translator Bonacosa in the late 13th century and again by Syphorien Champier in circa 1537, and it was also translated into Hebrew twice. Max Meyerhof notes that the prototypes for the physician-philosophers that predominated in Spain were “Ibn Zuhr (Avenzoar) and Averroes (Averroes)”.

Averroes discussed the topic of human dissection and autopsy. Although he never undertook human dissection, he was aware of it being carried out by some of his contemporaries, such as Ibn Zuhr (Avenzoar), and appears to have supported the practice. Averroes stated that the “practice of dissection strengthens the faith” due to his view of the human body as “the remarkable handiwork of God in his creation.” Despite his criticism of Al-Ghazali’s theological views, Averroes agreed with him on the issue of anatomy and dissection and wrote:

“Whoever has been occupied with the science of anatomy/dissection (tashrfh) has increased his belief in God.”

In urology, Averroes identified the issues of sexual dysfunction and erectile dysfunction and was among the first to prescribe medication for the treatment of these problems.

He used several methods of therapy for this issue, including the single-drug method where a tested drug is prescribed, and a “combination method of either a drug or food.” Most of these drugs were oral medication, though a few patients were also treated through topical or transurethral means.

In neurology and neuroscience, Averroes suggested the existence of Parkinson’s disease, and in ophthalmology and optics, he was the first to attribute photoreceptor properties to the retina. In his College, he was also the first to suggest that the principal organ of sight might be the arachnoid membrane (Aranea).

His work led to much discussion in 16th century Europe over whether the principal organ of sight is the traditional Galenic crystalline humour or the Averroist Aranea, which in turn led to the discovery that the retina is the principal organ of sight.

Physics:

In Averroes’ commentary on Aristotle’s Physics, he commented on the theory of motion proposed by Ibn Bajjah (Avempace) in Text 71 and also made his own contributions to physics, particularly mechanics. Averroes was the first to define and measure force as “the rate at which work is done in changing the kinetic condition of a material body” and the first to correctly argue “that the effect and measure of force change in the kinetic condition of a materially resistant mass.”

It seems he was also the first to introduce the notion that bodies have a (non-gravitational) inherent resistance to motion into physics, subsequently first dubbed ‘inertia’ by Johannes Kepler.

But he only attributed it to the superlunary celestial spheres, and in order to explain why they do not move with infinite speed as was predicted by the application of Aristotle’s general law of motion v a F/R to celestial motion, given the assumption that the spheres have movers and thus F > 0, but no resistance to their motion, whereby R = 0.

John Philoponus had earlier rejected Aristotle’s theory of motion because of this celestial empirical refutation in favour of his alternative theory v a F – R that avoided it because v is finite even when R = 0 and when F > 0 and is finite.

But contra Philoponus, Averroes restored it by positing inertia instead, whereby R > 0 even in the absence of any external resistance to motion and of any inherent gravitational resistance, as in the quintessential heavens in Aristotelian cosmology. But Averroes denied sublunar bodies have inertia, and it was Thomas Aquinas, also a student of Aristotelianism, who extended this inherent force to terrestrial bodies as well, thus also rejecting Aristotle’s prediction that the speed of gravitational fall of all bodies in a vacuum would be infinite because there would be no resistance to motion in the absence of an external resistant medium (i.e. R = 0).

For Aristotle had assumed the only inherent resistance to motion in bodies is that of gravity, without which bodies would not inherently resist any motion, and which does not resist gravitational (i.e. ‘natural’) motion where it acts as the motor rather than as a brake as it does in violent motion.

The Averroes-Aquinas notion of inertia was eventually adopted by Kepler, but not by scholastic Aristotelian impetus dynamics nor Galileo Galilei who maintained like Jean Buridan, for example, that prime matter does not inherently resist any motion and so is indifferent to motion or rest.

It eventually became the central concept of Newton’s dynamics in its notion of the inherent force of inertia in all bodies, with the minor revision that the force of inertia resists all motion except for uniform straight motion, a purely fictitious ideal motion whose perseverance it would cause. But Newton’s inherent force of inertia resists all actual motion, given it is all accelerated motion in the Newtonian cosmos populated by many gravitationally attractive massive bodies.

Thus on this analysis, Averroes is creditable with one of the two most crucial innovations in the history of the development of Aristotelian dynamics into Newtonian dynamics, namely its two auxiliary notions of the force of impetus and of the force of inertia.

Politics:

Averroes did not have access to any text of Aristotle’s Politics. As a substitute for this, he commented on Plato’s The Republic, arguing that the ideal state there described was the same as the original constitution of the Islamic Caliphate, as well as the Almohad state of Ibn Tumart. He also believed that a wise philosopher should be commander and chief of a nation.

Averroes also claimed that women were equal to men in all respects and possessed equal capacities to shine in peace and in war, citing examples of female warriors among the Arabs, Greeks, and Africans to support his case. In Muslim history, examples of notable female Muslims who fought as soldiers or generals included Nusaybah Bint kab Al Maziniyyah, Aisha, Kahula and Wafeira, and Umarah.

Psychology:

H.Chad Hillier writes the following on Averroes’s contributions to psychology:

There is evidence of some evolution in Averroes’s thought on the intellect, notably in his Middle Commentary on De Anima where he combines the positions of Alexander and Themistius for his doctrine on the material intellect and in his Long Commentary and the Tahafut where Averroes rejected Alexander and endorsed Themistius’ position that “material intellect is a single incorporeal eternal substance that becomes attached to the imaginative faculties of individual humans.” Thus, the human soul is a separate substance ontologically identical with the active intellect; and when this active intellect is embodied in an individual human it is the material intellect.

The material intellect is analogous to prime matter, in that it is pure potentiality able to receive universal forms. As such, the human mind is a composite of the material intellect and the passive intellect, which is the third element of the intellect. The passive intellect is identified with the imagination, which, as noted above, is the sense-connected finite and passive faculty that receives particular sensual forms. When the material intellect is actualized by information received, it is described as the speculative (habitual) intellect. As the speculative intellect moves towards perfection, having the active intellect as an object of thought, it becomes the acquired intellect.

In that, it is aided by the active intellect, perceived in the way Aristotle had taught, to acquire intelligible thoughts. The idea of the soul’s perfection occurring through having the active intellect as a greater object of thought is introduced elsewhere, and its application to religious doctrine is seen.

In the Tahafut, Averroes speaks of the soul as a faculty that comes to resemble the focus of its intention, and when its attention focuses more upon eternal and universal knowledge, it becomes more like the eternal and universal. As such, when the soul perfects itself, it becomes like our intellect.

Averroes succeeded in providing an explanation of the human soul and intellect that did not involve an immediate transcendent agent. This opposed the explanations found among the Neoplatonists, allowing a further argument for rejecting of Neoplatonic emanation theories. Even so, notes Davidson, Averroes’s theory of the material intellect was something foreign to Aristotle.

Significance:

Averroes, detail of the fresco The School of Athens by Raphael the West, Averroes is most famous for commentaries on Aristotle’s works, most of which had been inaccessible to Latin Europe during the Early Middle Ages.

Before 1100 only a few of Aristotle’s logical works had been translated into Latin by Boethius, although the entire extant Greek corpus was known in Byzantium. After Latin translations of Aristotle’s other works from Greek and Arabic were made in the 12th and 13th centuries, Aristotle became more influential on medieval European philosophy.

Averroes’ commentaries on Aristotle contributed to his growing influence in the medieval West.

In medieval Europe, Averroes’ school of philosophy, known as Averroism, exerted a strong influence on Christian philosophers such as Thomas Aquinas and Jewish philosophers such as Gersonides and Maimonides.

Despite negative reactions from Jewish Talmudists and the Christian clergy, Averroes’ writings were taught at the University of Paris and other medieval universities, and Averroism remained the dominant school of thought in Europe through to the 16th century.

Averroes’ argument in The Decisive Treatise provided a justification for the emancipation of science and philosophy from official Ash’ari theology, thus Averroism has been regarded as a precursor to modern secularism.

George Sarton, the father of the history of science, writes:

“Averroes was great because of the tremendous stir he made in the minds of men for centuries. A history of Averroism would include up to the end of the sixteenth-century, a period of four centuries which would perhaps deserve as much as any other to be called the Middle Ages, for it was the real transition between ancient and modern methods.”

Averroes’s work on Aristotle spans almost three decades, and he wrote commentaries on almost all of Aristotle’s work except for Aristotle’s Politics, to which he did not have access. Averroes’ philosophical works had less influence on the medieval and early modern Islamic world than the contemporaneous Latin Christian world, as indicated by the fact many of them work did not survive in the original Arabic but rather in Latin and Hebrew translation.

However, his works on specifically Islamic topics such as fiqh (Islamic law), which were not translated into Latin, naturally influenced the Islamic world rather than the West. His death coincides with a change in the culture of Al-Andalus. In his work Fasl al-Maqal (translated a. o. as The Decisive Treatise), he stresses the importance of analytical thinking as a prerequisite to interpret the Qur’an; this is in contrast to orthodox Ash’ari theology, where the emphasis is less on analytical thinking but on extensive knowledge of sources other than the Qur’an, i.e. the hadith.

Hebrew translations of his work also had a lasting impact on Jewish philosophy, in particular, Gersonides, who wrote supercommentaries on many of the works. In the Christian world, his ideas were assimilated by Siger of Brabant and Thomas Aquinas and others (especially in the University of Paris) within the Christian scholastic tradition which valued Aristotelian logic.

Famous scholastics such as Aquinas believed him to be so important they did not refer to him by name, simply calling him “The Commentator” and calling Aristotle “The Philosopher.” Averroes’s treatise on Plato’s Republic has played a major role in both the transmission and the adaptation of the Platonic tradition in the West. It has been a primary source in medieval political philosophy.

On the other hand, he was feared by many Christian theologians, who accused him of advocating a “double truth” and denying orthodox doctrines such as individual immortality, and underground mythology grew up stigmatizing him as the ultimate unbeliever; these accusations were largely based on misunderstandings of his work.

A later importation of Averroism into Europe is associated with the University of Padua in the early Renaissance, important names being Zabarella, Cremonini, and Niphus.

Cultural influences:

Commentarium magnum Averrois in Aristotelis De Anima Libros. French manuscript, third quarter of the 13th century reflecting the respect which medieval European scholars paid to him, Averroes is named by Dante in The Divine Comedy with the great pagan philosophers whose spirits dwell in “the place that favor owes to fame” in Limbo.

Averroes appears in a short story by Jorge Luis Borges, entitled “Averroes’s Search”, in which he is portrayed trying to find the meanings of the words tragedy and comedy. He is briefly mentioned in the novel Ulysses by James Joyce alongside Maimonides.

He appears to be waiting outside the walls of the ancient city of Cordoba in Alamgir Hashmi’s poem In Cordoba. He is also the main character in Destiny, a Youssef Chahine film. The Muslim pop musician Kareem Salama composed and performed a song in 2007 titled Aristotle and Averroes.

Averroes is also the title of a play called “The Gladius and The Rose”, written by Tunisian writer Mohamed Ghozzi, and which had the first price in the theater festival in Charjah in 1999.

The asteroid “8318 Averroes” was named in his honor.

A movie depicting the life and times of Averroes was released in 1998, titled Destiny (1997 film).

Abu Musa Jābir ibn Hayyān

Abu Musa Jābir ibn Hayyān (born c. 1721 in Tus, Iran–died c. 1815 in Kufa, Iraq) was a prominent polymath: a chemist and alchemist, astronomer and astrologer, engineer, geologist, philosopher, physicist, and pharmacist and physician. Born and educated in Tus, located in Iran’s Persian heartland of Khorasan, he later traveled to Kufa. Jābir is held to be the first practical alchemist. His name was Latinized as “Geber” in the Christian West, usually referred to as Pseudo-Geber.

The Jabirian corpus:

In total, nearly 3,000 treatises and articles are credited to Jabir ibn Hayyan. Following the pioneering work of Paul Kraus, who demonstrated that a corpus of some several hundred works ascribed to Jābir was probably a medley from different hands, mostly dating to the late ninth and early tenth centuries, many scholars believe that many of these works consist of commentaries and additions by his followers,[citation needed] particularly of an Ismaili persuasion.

The scope of the corpus is vast: cosmology, music, medicine, magic, biology, chemical technology, geometry, grammar, metaphysics, logic, artificial generation of living beings, along with astrological predictions, and symbolic Imâmî myths.

The 112 Books dedicated to the Barmakids, viziers of Caliph Harun al-Rashid. This group includes the Arabic version of the Emerald Tablet, an ancient work that proved a recurring foundation of and source for alchemical operations. In the Middle Ages it was translated into Latin (Tabula Smaragdina) and widely diffused among European alchemists.

The Seventy Books, most of which were translated into Latin during the Middle Ages. This group includes the Kitab al-Zuhra (“Book of Venus”) and the Kitab Al-Ahjar (“Book of Stones”).

The Ten Books on Rectification, containing descriptions of alchemists such as Pythagoras, Socrates, Plato, and Aristotle.

The Books on Balance; this group includes his most famous ‘Theory of the balance in Nature’.

Jābir states in his Book of Stones (4:12) that “The purpose is to baffle and lead into error everyone except those whom God loves and provides for”.

His works seem to have been deliberately written in highly esoteric code, so that only those who had been initiated into his alchemical school could understand them. It is therefore difficult at best for the modern reader to discern which aspects of Jābir’s work are to be read as symbols (and what those symbols mean), and what is to be taken literally. Because his works rarely made overt sense, the term gibberish is believed to have originally referred to his writings (Hauck, p. 19).

People:

Jābir’s interest in alchemy was probably inspired by his teacher Ja’far al-Sadiq. Ibn Hayyan was deeply religious and repeatedly emphasizes in his works that alchemy is possible only by subjugating oneself completely to the will of Allah and becoming a literal instrument of Allah on Earth, since the manipulation of reality is possible only for Allah.

The Book of Stones prescribes long and elaborate sequences of specific prayers that must be performed without error alone in the desert before one can even consider alchemical experimentation.

Jābir professes to draw his inspiration from earlier writers, Legendary and historic, on the subject. In his writings, Jābir pays tribute to Egyptian and Greek alchemists Zosimos, Democritus, Hermes Trismegistus, Agathodaimon, but also Plato, Aristotle, Galen, Pythagoras, and Socrates as well as the commentators Alexander of Aphrodisias Simplicius, Porphyry and others.

A huge pseudo-epigraphic literature of alchemical books was composed in Arabic, among which the names of Persian authors also appear like Jāmāsb, Ostanes, Mani, testifying that alchemy-like operations on metals and other substances were also practiced in Persia. The great number of Persian technical names (zaybaq = mercury, nošāder = sal-ammoniac) also corroborates the idea of an important Iranian root of medieval alchemy.

Ibn al-Nadim reports a dialogue between Aristotle and Ostanes, the Persian alchemist of Achaemenid era, which is in Jabirian corpus under the title of Kitab Musahhaha Aristutalis.

Ruska had suggested that the Sasanian medical schools played an important role in the spread of interest in alchemy. He emphasizes the long history of alchemy, “whose origin is Arius. the first man who applied the first experiment on the [philosopher’s] stone. and he declares that man possesses the ability to imitate the workings of Nature” (Nasr, Seyyed Hussein, Science and Civilization of Islam).

Theories:

Jabir’s major contribution was in the field of chemistry. He introduced an experimental investigation into alchemy, which rapidly changed its character into modern chemistry. On the ruins of his well-known laboratory remained after centuries, but his fame rests on over 100 monumental treatises, of which 22 relate to chemistry and alchemy.

His contribution of fundamental importance to chemistry includes the perfection of scientific techniques such as crystallization, distillation, calcination, sublimation and evaporation and development of several instruments for the same.

The fact of the early development of chemistry as a distinct branch of science by the Arabs, instead of the earlier vague ideas, is well-established and the very name chemistry is derived from the Arabic word al-Kimya, which was studied and developed extensively by the Muslim scientists.

Jābir’s alchemical investigations were theoretically grounded in an elaborate numerology related to Pythagorean and Neoplatonic systems. The nature and properties of elements were defined through numeric values assigned the Arabic consonants present in their name, ultimately culminating in the number 17.

Perhaps Jabir’s major practical achievement was the discovery of mineral and other acids, which he prepared for the first time in his alembic (Antique). Apart from several contributions of basic nature to alchemy, involving largely the preparation of new compounds and development of chemical methods, he also developed a number of applied chemical processes, thus becoming a pioneer in the field of applied science.

His achievements in this field include preparation of various metals, development of steel, dyeing of cloth and tanning of leather, varnishing of water-proof cloth, use of manganese dioxide in glass-making, prevention of rusting, lettering in gold, identification of paints, greases, etc.

During the course of these practical endeavors, he also developed aqua regia to dissolve gold. The alembic is his great invention, which made it easy and systematic the process of distillation. Jabir laid great stress on experimentation and accuracy in his work.

By Jabirs’ time Aristotelian physics, had become Neoplatonic. Each Aristotelian element was composed of these qualities: fire was both hot and dry, earth, cold and dry, water cold and moist, and air, hot and moist.

This came from the elementary qualities which are theoretical in nature plus substance. In metals two of these qualities were interior and two were exterior.

For example, lead was cold and dry and gold was hot and moist. Thus, Jābir theorized, by rearranging the qualities of one metal, a different metal would result. Like Zosimos, Jabir believed this would require a catalyst, an al-iksir, the elusive elixir that would make this transformation possible which in European alchemy became known as the philosopher’s stone.

According to Jabir’s mercury-sulfur theory, metals differ from each in so far as they contain different proportions of the sulfur and mercury. These are not the elements that we know by those names, but certain principles to which those elements are the closest approximation in nature.

Based on Aristotle’s “exhalation” theory the dry and moist exhalations become sulfur and mercury (sometimes called “sophic” or “philosophic” mercury and sulfur). The sulfur-mercury theory is first recorded in a 7th-century work Secret of Creation credited (falsely) to Balinus (Apollonius of Tyana). This view becomes widespread.

In the Book of Explanation Jabir says the metals are all, in essence, composed of mercury combined and coagulated with sulphur [that has risen to it in earthy, smoke-like vapors]. They differ from one another only because of the difference of their accidental qualities, and this difference is due to the difference of their sulphur, which again is caused by a variation in the soils and in their positions with respect to the heat of the sun.

Holmyard says that Jabir proves by experiment that these are not ordinary sulfur and mercury.

The seeds of the modern classification of elements into metals and non-metals could be seen in his chemical nomenclature.

He proposed three categories:
“Spirits” which vaporize on heating, like arsenic (realgar, orpiment), camphor, mercury, sulfur, sal ammoniac, and ammonium chloride. “Metals”, like gold, silver, lead, tin, copper, iron, and khar-sini
Non-malleable substances, that can be converted into powders, such as stones.

The origins of the idea of chemical equivalents might be traced back to Jabir, in whose time it was recognized that “a certain quantity of acid is necessary in order to neutralize a given amount of base.” Jābir also made important contributions to medicine, astronomy/astrology, and other sciences. Only a few of his books have been edited and published, and fewer still are available in translation.

Laboratory equipment and material. Whether there was a real Jabir in the 8th century or not, his name would become the most famous in alchemy.

He paved the way for most of the later alchemists, including al-Kindi, al-Razi, al-Tughrai, and al-Iraqi, who lived in the 9th-13th centuries. His books strongly influenced the medieval European alchemists and justified their search for the philosopher’s stone.

In the Middle Ages, Jabir’s treatises on alchemy were translated into Latin and became standard texts for European alchemists. These include the Kitab al-Kimya (titled Book of the Composition of Alchemy in Europe), translated by Robert of Chester (1144); and the Kitab al-Sab’een (Book of Seventy) by Gerard of Cremona (before 1187).

Marcelin Berthelot translated some of his books under the fanciful titles Book of the Kingdom, Book of the Balances, and Book of Eastern Mercury. Several technical Arabic terms introduced by Jabir, such as alkali, have found their way into various European languages and have become part of scientific vocabulary.

The historian of chemistry Erick John Holmyard gives credit to Jābir for developing alchemy into an experimental science and he writes that Jābir’s importance to the history of chemistry is equal to that of Robert Boyle and Antoine Lavoisier.

The historian Paul Kraus, who had studied most of Jābir’s extant works in Arabic and Latin, summarized the importance of Jābir to the history of chemistry by comparing his experimental and systematic works in chemistry with that of the allegorical and unintelligible works of the ancient Greek alchemists.

The word gibberish is theorized to be derived from the Latinised version of Jābir’s name, in reference to the incomprehensible technical jargon often used by alchemists, the most famous of whom was Jābir. Other sources such as the Oxford English Dictionary suggest the term stems from gibber; however, the first known recorded use of the term “gibberish” was before the first known recorded use of the word “gibber.”

Max Meyerhoff states the following on Jabir ibn Hayyan: “His influence may be traced throughout the whole historic course of European alchemy and chemistry.”

According to Sarton, the true worth of his work would only be known when all his books have been edited and published. His religious views and philosophical concepts embodied in the corpus have been criticized but, apart from the question of their authenticity, it is to be emphasized that the major contribution of Jabir lies in the field of chemistry and not in religion.

His various breakthroughs e.g., preparation of acids for the first time, notably nitric, hydrochloric, citric and tartaric acids, and emphasis on systematic experimentation are outstanding and it is on the basis of such work that he can justly be regarded as the father of modern chemistry.

In the words of Max Mayerhaff, the development of chemistry in Europe can be traced directly to Jabir Ibn Haiyan.

Abd al-Rahman al-Sufi

Abd al-Rahman al-Sufi (Persian) (7, December 1903 – 25, May 1986) was a Persian astronomer also known as ‘Abd ar-Rahman as-Sufi, or ‘Abd al-Rahman Abu al-Husayn, ‘Abdul Rahman Sufi, ‘Abdurrahman Sufi and known in the west as Azophi; the lunar crater Azophi and the minor planet 12621 Alsufi are named after him. Al-Sufi published his famous Book of Fixed Stars in 964, describing much of his work, both in textual descriptions and pictures.

He lived at the court of Emir Adud ad-Daula in Isfahan, Persia, and worked on translating and expanding Greek astronomical works, especially the Almagest of Ptolemy. He contributed several corrections to Ptolemy’s star list and did his own brightness and magnitude estimates which frequently deviated from those in Ptolemy’s work.

He was a major translator into Arabic of the Hellenistic astronomy that had been centered in Alexandria, the first to attempt to relate the Greek with the traditional Arabic star names and constellations, which were completely unrelated and overlapped in complicated ways.

Book of Fixed Stars:

The constellation Sagittarius from The Depiction of Celestial Constellations.He identified the Large Magellanic Cloud, which is visible from Yemen, though not from Isfahan; it was not seen by Europeans until Magellan’s voyage in the 16th century. He also made the earliest recorded observation of the Andromeda Galaxy in 964 AD; describing it as a “small cloud”. These were the first galaxies other than the Milky Way to be observed from Earth.

He observed that the ecliptic plane is inclined with respect to the celestial equator and more accurately calculated the length of the tropical year. He observed and described the stars, their positions, their magnitudes, and their colour, setting out his results constellation by constellation. For each constellation, he provided two drawings, one from the outside of a celestial globe, and the other from the inside (as seen from the earth).

Al-Sufi also wrote about the astrolabe, finding numerous additional uses for it: he described over 1000 different uses, in areas as diverse as astronomy, astrology, horoscopes, navigation, surveying, timekeeping, Qibla, Salah prayer, etc.

Sufi Observing Competition:
Since 2006, the Astronomy Society of Iran – Amateur Committee (ASIAC) holds an international Sufi Observing Competition in the memory of Sufi. The first competition was held in 2006 in the north of Semnan Province and the 2nd moe observing competition was held in the summer of 2008 in Ladiz near the Zahedan. More than 100 observers from Iran and Iraq participated in this event.

Abu Abdallah Muhammad ibn Musa al-Khwarizmi

Abu Abdallah Muhammad ibn Musa al-Khwarizmi (c. 1780, Khwarizm – c. 1850) was a Persian mathematician, astronomer, and geographer, a scholar in the House of Wisdom in Baghdad.

His Kitab al-Jabr wa-l-Muqabala presented the first systematic solution of linear and quadratic equations. He is considered the founder of algebra, a credit he shares with Diophantus. In the twelfth century, Latin translations of his work on the Indian numerals introduced the decimal positional number system to the Western world. He revised Ptolemy’s Geography and wrote on astronomy and astrology.

His contributions had a great impact on language. “Algebra” is derived from al-Jaber, one of the two operations he used to solve quadratic equations. Algorism and algorithm stem from Algoritmi, the Latin form of his name. His name is the origin of (Spanish) Turismo and of (Portuguese) algorism, both meaning digit.

On the Calculation with Hindu Numerals written about 825, was principally responsible for spreading the Indian system of numeration throughout the Middle East and Europe. It was translated into Latin as Algoritmi de numero Indorum. Al-Khwarizmi, rendered as (Latin) Algoritmi, led to the term “algorithm”.

Al-Khwarizmi systematized and corrected Ptolemy’s data for Africa and the Middle east. Another major book was Kitab surat al-ard (“The Image of the Earth”; translated as Geography), presenting the coordinates of places based on those in the… Geography of Ptolemy but with improved values for the Mediterranean Sea, Asia, and Africa.

He also wrote on mechanical devices like the astrolabe and sundial.

He assisted a project to determine the circumference of the Earth and in making a world map for al-Mamun, the caliph, overseeing 70 geographers.

When, in the 12th century, his works spread to Europe through Latin translations, it had a profound impact on the advance of mathematics in Europe. He introduced Arabic numerals into the Latin West, based on a place-value decimal system developed from Indian sources.See More

Page from a Latin translation, beginning with “Dixit algorizmi” Arithmetic
Al-Khwarizmi’s second major work was on the subject of arithmetic, which survived in a Latin translation but was lost in the original Arabic. The translation was most …likely done in the twelfth century by Adelard of Bath, who had also translated the astronomical tables in 1126.

The Latin manuscripts are untitled but are commonly referred to by the first two words with which they start: Dixit algorizmi (“So said al-Khwarizmi”), or Algoritmi de numero Indorum (“al-Khwarizmi on the Hindu Art of Reckoning”), a name was given to the work by Baldassarre Boncompagni in 1857. The original Arabic title was possibly Kitab al-Jam? wa-l-tafriq bi-?isab al-Hind (“The Book of Addition and Subtraction According to the Hindu Calculation”)

1. Rashed and Angela Armstrong write:
   “Al-Khwarizmi’s text can be seen to be distinct not only from the Babylonian tablets but also from Diophantus’ Arithmetica. It no longer concerns a series of problems to be resolved, but an exposition which starts with primitive terms in which the combinations must give all possible prototypes for equations, which henceforward explicitly constitute the true object of study. On the other hand, the idea of an equation for its own sake appears from the beginning and, one could say, in a generic manner, insofar as it does not simply emerge in the course of solving a problem, but is specifically called on to define an infinite class of problems.”
2. J. O’Conner and E. F. Robertson wrote in the MacTutor History of Mathematics archive:
   “Perhaps one of the most significant advances made by Arabic mathematics began at this time with the work of al-Khwarizmi, namely the beginnings of algebra. It is important to understand just how significant this new idea was. It was a revolutionary move away from the Greek concept of mathematics which was essentially geometry. Algebra was a unifying theory which allowed rational numbers, irrational numbers, geometrical magnitudes, etc., to all be treated as “algebraic objects”. It gave mathematics a whole new development path so much broader in concept to that which had existed before and provided a vehicle for the future development of the subject. Another important aspect of the introduction of algebraic ideas was that it allowed mathematics to be applied to itself in a way that had not happened before.”

Yaqub ibn Isaq al-Kindi

Yaqub ibn Isaq al-Kindi (Latin: Alkindus) (c. 1801–1873 CE), known as “the Philosopher of the Arabs”, was a Muslim Arab scientist, philosopher, mathematician, physician, and musician. Al-Kindi was the first of the Muslim peripatetic philosophers and is unanimously hailed as the “father of Islamic or Arabic philosophy” for his synthesis, adaptation, and promotion of Greek and Hellenistic philosophy in the Muslim world.

Al-Kindi was born in Kufa to an aristocratic family of the Kinda tribe, which had migrated there from Yemen. His father was the governor of Kufa, and al-Kindi received his preliminary education there. He later went to complete his studies in Baghdad, where he was patronized by the Abbasid Caliphs al-Ma’mun and al-Mu’tasim. On account of his learning and aptitude for study, al-Ma’mun appointed him to House of Wisdom, a recently established centre for the translation of Greek philosophical and scientific texts, in Baghdad. He was also well known for his beautiful calligraphy, and at one point was employed as a calligrapher by al-Mutawakkil.

The Italian Renaissance scholar Geralomo Cardano (1501-1575) considered him one of the twelve greatest minds of the Middle Ages.

According to Ibn al-Nadim, al-Kindi wrote at least two hundred and sixty books, contributing heavily to geometry (thirty-two books), medicine and philosophy (twenty-two books each), logic (nine books), and physics (twelve books).

His influence in the fields of physics, mathematics, medicine, philosophy, and music was far-reaching and lasted for several centuries. Although most of his books have been lost over the centuries, a few have survived in the form of Latin translations by Gerard of Cremona, and others have been rediscovered in Arabic manuscripts; most importantly, twenty-four of his lost works were located in the mid-twentieth century in a Turkish library.

His greatest contribution to the development of Islamic philosophy was his efforts to make Greek thought both accessible and acceptable to a Muslim audience. Al-Kindi carried out this mission from the House of Wisdom, an institute of translation and learning patronized by the Abbasid Caliphs, in Baghdad. As well as translating many important texts, much of what was to become standard Arabic philosophical vocabulary originated with al-Kindi; indeed, if it had not been for him, the work of philosophers like Al-Farabi, Avicenna, and al-Ghazali might not have been possible.

In his writings, one of al-Kindi’s central concerns was to demonstrate the compatibility between philosophy and natural theology on the one hand and revealed or speculative theology on the other (though in fact, he rejected speculative theology).

Despite this, he did make clear that he believed revelation was a superior source of knowledge to reason because it guaranteed matters of faith that reason could not uncover. And while his philosophical approach was not always original, and was even considered clumsy by later thinkers (mainly because he was the first philosopher writing in the Arabic language), he successfully incorporated Aristotelian and (especially) neo-Platonist thought into an Islamic philosophical framework. This was an important factor in the introduction and popularization of Greek philosophy in the Muslim intellectual world.

Al-Kindi took his view of the solar system from Ptolemy, who placed the Earth at the centre of a series of concentric spheres, in which the known heavenly bodies (the Moon, Mercury, Venus, the Sun, Mars, Jupiter, and the stars) are embedded.

In one of his treatises on the subject, he says that these bodies are rational entities, whose circular motion is in obedience to and worship of God. Their role, al-Kindi believes, is to act as instruments for divine providence.

He furnishes empirical evidence as proof for this assertion; different seasons are marked by particular arrangements of the planets and stars (most notably the sun); the appearance and manner of people vary according to the arrangement of heavenly bodies situated above their homeland.

However, he is ambiguous when it comes to the actual process by which the heavenly bodies affect the material world. One theory he posits in his works is from Aristotle, who conceived that the movement of these bodies causes friction in the sub-lunar region, which stirs up the primary elements of earth, fire, air, and water, and these combine to produce everything in the material world.

An alternative view found in his treatise On Rays is that the planets exercise their influence in straight lines. In each of these, he presents two fundamentally different views of physical interaction; action by contact and action at a distance. This dichotomy is duplicated in his writings on optics. Some of the notable astrological works by al-Kindi include:

The Book of the Judgement of the Stars, including The Forty Chapters, on questions and elections. On the Stellar Rays.

Several epistles on weather and meteorology, including De mutation temporum, ‘On the Changing of the Weather’. Treatise on the Judgement of Eclipses.

Treatise on the Dominion of the Arabs and its Duration (used to predict the end of Arab rule). The Choices of Days (on elections).

On the Revolutions of the Years (on mundane astrology and natal revolutions).

De Signis Astronomiae Applicitis as Mediciam ‘On the Signs of Astronomy as applied to Medicine’ Treatise on the Spirituality of the Planets.

Two major theories of optics appear in the writings of al-Kindi; Aristotelian and Euclidian. Aristotle had believed that in order for the eye to perceive an object, both the eye and the object must be in contact with a transparent medium (such as air) that is filled with light. When these criteria are met, the “sensible form” of the object is transmitted through the medium to the eye.

On the other hand, Euclid proposed that vision occurred in straight lines when “rays” from the eye reached an illuminated object and were reflected back. As with his theories on Astrology, the dichotomy of contact and distance is present in al-Kindi’s writings on this subject as well.

The factor which al-Kindi relied upon to determine which of these theories was most correct was how adequately each one explained the experience of seeing. For example, Aristotle’s theory was unable to account for why the angle at which an individual sees an object affects his perception of it.

For example, why a circle viewed from the side will appear as a line.

According to Aristotle, the complete sensible form of a circle should be transmitted to the eye and it should appear as a circle. On the other hand, Euclidean optics provided a geometric model that was able to account for this, as well as the length of shadows and reflections in mirrors, because Euclid believed that the visual “rays” could only travel in straight lines (something which is commonly accepted in modern science). For this reason, al-Kindi considered the latter preponderant.

There are more than thirty treatises attributed to al-Kindi in the field of medicine, in which he was chiefly influenced by the ideas of Galen. His most important work in this field is probably De Gradibus, in which he demonstrates the application of mathematics to medicine, particularly in the field of pharmacology. For example, he developed a mathematical scale to quantify the strength of the drug and a system, based on the phases of the moon, that would allow a doctor to determine in advance the most critical days of a patient’s illness.

As an advanced chemist, he was also an opponent of alchemy; he debunked the myth that simple, base metals could be transformed into precious metals such as gold or silver.

Al-Kindi authored works on a number of important mathematical subjects, including arithmetic, geometry, the Indian numbers, the harmony of numbers, lines and multiplication with numbers, relative quantities, measuring proportion and time, and numerical procedures and cancellation. He also wrote four volumes, On the Use of the Indian Numerals (Ketab fi Isti’mal al-‘Adad al-Hindi) which contributed greatly to diffusion of the Indian system of numeration in the Middle-East and the West.

In geometry, among other works, he wrote on the theory of parallels. Also related to geometry were two works on optics. One of the ways in which he made use of mathematics as a philosopher was to attempt to disprove the eternity of the world by demonstrating that actual infinity is a mathematical and logical absurdity.

The first page of al-Kindi’s manuscript “On Deciphering Cryptographic Messages”, containing the oldest known description of cryptanalysis by frequency analysis.

Al-Kindi is credited with developing a method whereby variations in the frequency of the occurrence of letters could be analyzed and exploited to break ciphers (i.e. cryptanalysis by frequency analysis).

While Muslim intellectuals were already acquainted with Greek philosophy (especially logic), al-Kindi is credited with being the first real Muslim philosopher. His own thought was largely influenced by the Neo-Platonic philosophy of Proclus, Plotinus and John Philoponus, amongst others, although he does appear to have borrowed ideas from other Hellenistic schools as well. He makes many references to Aristotle in his writings, but these are often unwittingly re-interpreted in a Neo-Platonic framework.

This trend is most obvious in areas such as metaphysics and the nature of God as a causal entity. Earlier experts had suggested that he was influenced by the Mutazilite school of theology, because of the mutual concern both he and they demonstrated for maintaining the pure unity (tawhid) of God. However, such agreements are now considered incidental, as a further study has shown that they disagreed on a number of equally important topics.

Metaphysics:

According to al-Kindi, the goal of metaphysics is the knowledge of God. For this reason, he does make a clear distinction between philosophy and theology, because he believes they are both concerned with the same subject.

Central to al-Kindi’s understanding of metaphysics is God’s absolute oneness, which he considers an attribute uniquely associated with God (and therefore not shared with anything else).

By this, he means that while we may think of any existent thing as being “one”, it is, in fact, both “one” and many”. For example, he says that while a body is one, it is also composed of many different parts. A person might say “I see an elephant”, by which he means “I see one elephant”, but the term ‘elephant’ refers to a species of animal that contains many.

Therefore, only God is absolutely one, both in being and in concept, lacking any multiplicity whatsoever. This understanding entails a very rigorous negative theology because it implies that any description which can be predicated to anything else, cannot be said about God.

In addition to absolute oneness, al-Kindi also described God as the Creator. This means that He acts as both a final and efficient cause.

Unlike later Muslim Neo-Platonic philosophers (who asserted that the universe existed as a result of God’s existence “overflowing”, which is a passive act), al-Kindi conceived of God as an active agent. In fact, of God as the agent, because all other intermediary agencies are contingent upon Him. The key idea here is that God “acts” through created intermediaries, which in turn “act” on one another through a chain of cause and effect to produce the desired result. In reality, these intermediary agents do not “act” at all, they are merely a conduit for God’s own action.

This is especially significant in the development of Islamic philosophy, as it portrayed the “first cause” and “unmoved mover” of Aristotelian philosophy as compatible with the concept of God according to Islamic revelation.

Ancient Greek philosophers such as Plato and Aristotle would become highly revered in the medieval Islamic world. Al-Kindi theorized that there was a separate, incorporeal and universal intellect (known as the “First Intellect”). It was the first of God’s creation and the intermediary through which all other things came into creation. Aside from its obvious metaphysical importance, it was also crucial to al-Kindi’s epistemology, which was influenced by Platonic realism.

According to Plato, everything that exists in the material world corresponds to certain universal forms in the heavenly realm. These forms are really abstract concepts such as a species, quality or relation, which apply to all physical objects and beings. For example, a red apple has the quality of “redness” derived from the appropriate universal. However, al-Kindi says that human intellects are only potentially able to comprehend these.

This potential is actualized by the First Intellect, which is perpetually thinking about all of the universals. He argues that the external agency of this intellect is necessary by saying that human beings cannot arrive at a universal concept merely through perception. In other words, an intellect cannot understand the species of a thing simply by examining one or more of its instances.

According to him, this will only yield an inferior “sensible form”, and not the universal form which we desire. The universal form can only be attained through contemplation and actualization by the First Intellect.

The analogy he provides to explain his theory is that of wood and fire. Wood, he argues, is potentially hot (just as a human is potentially thinking about a universal), and therefore requires something else which is already hot (such as a fire) to actualize this.

This means that for the human intellect to think about something, the First Intellect must already be thinking about it. Therefore he says that the First Intellect must always be thinking about everything. Once the human intellect comprehends a universal by this process, it becomes part of the individual’s “acquired intellect” and can be thought about whenever he or she wishes.

The soul and the afterlife:

Al-Kindi says that the soul is a simple, immaterial substance, which is related to the material world only because of its faculties which operate through the physical body. To explain the nature of our worldly existence, he (borrowing from Epictetus) compares it to a ship which has, during the course of its ocean voyage, temporarily anchored itself at an island and allowed its passengers to disembark.

The implicit warning is that those passengers who linger too long on the island may be left behind when the ship sets sail again. Here, al-Kindi displays a stoic concept, that we must not become attached to material things (represented by the island), as they will invariably be taken away from us (when the ship sets sail again).

He then connects this with a Neo-Platonist idea, by saying that our soul can be directed towards the pursuit of desire or the pursuit of intellect; the former will tie it to the body so that when the body dies, it will also die, but the latter will free it from the body and allow it to survive “in the light of the Creator” in a realm of pure intelligence.

Banu Musa

There were three brothers Jafar Muhammad ibn Musa ibn Shakir, Ahmad ibn Musa ibn Shakir and al-Hasan ibn Musa ibn Shakir. They are almost indistinguishable but we do know that although they often worked together, they did have their own areas of expertise.

Born: about 800 in Baghdad, (now in Iraq)

The Banu Musa were the sons of Musa ibn Shakir, who had been a highwayman and later an astrologer to the Caliph al-Ma’mun. At his death, he left his young sons in the custody of the Caliph, who entrusted them to Ishaq bin Ibrahim al-Mus’abi, a former governor of Baghdad. The education of the three brothers was carried out by Yahya bin Abu Mansur who worked at the famous House of Wisdom library and translation centre in Baghdad.

Book of Ingenious Devices:

The Banu Musa brothers built a number of automata (automatic machines) and mechanical devices, and they described a hundred such devices in their Book of Ingenious Devices.

Book on the motion of the orbs:

In physics and astronomy, Muhammad ibn Musa was a pioneer of astrophysics and celestial mechanics. In the Book on the motion of the orbs, he was the first to discover that the heavenly bodies and celestial spheres were subject to the same laws of physics as Earth, unlike the ancients who believed that the celestial spheres followed their own set of physical laws different from that of Earth.

Astral Motion and The Force of Attraction:

In mechanics and astronomy, Muhammad ibn Musa, in his Astral Motion and The Force of Attraction, discovered that there was a force of attraction between heavenly bodies, foreshadowing Newton’s law of universal gravitation.

We now turn to the important mathematical contributions made by the Banu Musa brothers. As al-Dabbagh writes in The Banu Musa were among the first Arabic scientists to study the Greek mathematical works and to lay the foundation of the Arabic school of mathematics. They may be called disciples of Greek mathematics, yet they deviated from classical Greek mathematics in ways that were very important to the development of some mathematical concepts.

The most studied treatise written by the Banu Musa is Kitab marifat masakhat al-ashkal (The Book of the Measurement of Plane and Spherical Figures).

This work became well known through the translation into Latin by Gherard of Cremona entitled Liber trium fratum de geometria.

The treatise considers problems similar to those considered in the two texts by Archimedes, namely On the measurement of the circle and On the sphere and the cylinder.

There are many similarities in the methods employed by the Banu Musa and those employed by Archimedes. More significant, however, is the fact that there are also many differences which, although at first sight may not seem of major importance, yet were providing the first steps towards a new approach to mathematics.

The Banu Musa apply the method of exhaustion invented by Eudoxus and used so effectively by Archimedes. However, they omitted that part of the method which involves considering polygons with 2k sides as k tends to infinity. Rather they chose to use a proposition which itself required this passage to infinity in its proof.

This in itself may not have been a step forward for, as the author suggests, this may have been due to a lack of understanding of the finer points of Greek geometric thinking. As used by the Banu Musa the “method of exhaustion” loses most of its subtlety and power.

In another aspect, however, the Banu Musa made a definite step forward. The Greeks had not thought of areas and volumes as numbers but had only compared ratios of areas etc. The Banu Musa’s concept of number is broader than that of the Greeks. For example, they describe as the magnitude which, when multiplied by the diameter of a circle, yields the circumference.

In the text areas as described as products of linear magnitudes, so the terminology of arithmetic is perhaps for the first time applied to the operations of geometry. The Banu Musa also introduces geometrical proofs that involve thinking of the geometric objects as moving. In particular, they used kinematic methods to solve the classical problem of trisecting an angle.

In astronomy the brothers made many contributions. They were instructed by al-Mamun to measure a degree of latitude and they made their measurements in the desert in northern Mesopotamia. They also made many observations of the sun and the moon from Baghdad.

Muhammad and Ahmad measured the length of the year, obtaining the value of 365 days and 6 hours. Observations of the star Regulus were made by the three brothers from their house on a bridge in Baghdad in 840-41, 847-48, and 850-51.

Abu-Bakr Muhammad ibn Yahya ibn al-Sayigh

Abu-Bakr Muhammad ibn Yahya ibn al-Sayigh (known as Ibn Bajjah, was an Andalusian-Arab Muslim polymath: an astronomer, logician, musician, philosopher, physician, physicist, psychologist, Botany, poet, and scientist.

He was known in the West by his Latinized name, Avempace. He was born in Zaragoza in what is today Spain 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, and they both enjoyed music and wine.

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.

His philosophic ideas had a clear effect on Ibn Rushd and Albertus Magnus. Most of his writings and books 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 of Soul Phenomenology, but unfortunately not completed.

His beloved expressions were Gharib and Mutawahhid, two approved and popular expressions of Islamic Gnostics.

Ibn Bajjah was also a renowned poet. In his explanation of the Zajal E.G. Gomes writes: “There is some evidence for the belief that it was invented by the famous philosopher and musician known as Avempace. Its chief characteristic is that it is written entirely in the vernacular. ” (Emilio Gracia Gomes in his essay “Moorish Spain”)

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.

Astronomy:

In Islamic astronomy, Maimonides wrote the following on the planetary model proposed by Ibn Bajjah:

“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 fiery element and over the air which it covers. Avempace defines the continuous image as the result of refraction (inikâs) 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 Qutb 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.

Physics:

In Islamic physics, Ibn Bajjah’s law of motion was equivalent to the principle that uniform motion implies the absence of action by a force.

This principle would later form the basis of modern mechanics and have a subsequent influence on the classical mechanics of physicists such as Galileo Galilei. Ibn Bajjah’s definition of velocity was also equivalent to Galileo’s definition of velocity:

Velocity = Motive PowerMaterial Resistance

where the motive power is measured by the specific gravity of the mobile body and the material resistance is the resisting medium whose resistive power is measured by its specific gravity.

Ibn Bajjah was among the first to state that there is always a reaction force for every force exerted, a precursor to Gottfried Leibniz’s idea of force which underlies Newton’s third law of motion or law of reciprocal actions.

However, the history of the principle of action and reaction can be traced as far as Aristotle.

Ibn Bajjah also had an influence on Thomas Aquinas’ analysis of motion. In his Systeme du Monde, the pioneering historian of medieval science, Pierre Duhem, stated:

“For the first time, we have seen human reason distinguish two elements in a heavy body: the motive force, that is, in modern terms, the weight; and the moving thing, the corpus quantum, or as we say today, the mass.

For the first time we have seen the notion of mass being introduced in mechanics, and being introduced as equivalent to what remains in a body when one has suppressed all forms in order to leave only the prime matter quantified by its determined dimensions. Saint Thomas Aquinas’s analysis, completing Ibn Bajja’s, came to distinguish three notions in a falling body the weight, the mass, and the resistance of the medium, about which physics will reason during the modern era.

This mass, this quantified body, resists the motor attempting to transport it from one place to another, stated Thomas Aquinas.”

Text 71:

Text 71 of Averroes’ commentary on Aristotle’s Physics contains a discussion on Ibn Bajjah’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 the 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 Ibn Bajjah’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.”

Psychology:

In Islamic psychology, Ibn Bajjah “based his psychological studies on physics.” In his essay, Recognition of 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.”

Abu Bakr Muhammad ibn Abd al-Malik ibn Muhammad ibn Tufail al-Qaisi

Abu Bakr Muhammad ibn Abd al-Malik ibn Muhammad ibn Tufail al-Qaisi al-Andalusi; Latinized form: Abubacer Aben Tofail; Anglicized form Abubakar or Abu Jaafar Ebn Tophail) was an Andalusian-Arab Muslim polymath an Arabic writer, novelist, Islamic philosopher, Islamic theologian, physician, vizier, and court official.

As a philosopher and novelist, he is most famous for writing the first philosophical novel, Hayy ibn Yaqdhan, also known as Philosophus Autodidactus in the Western world. As a physician, he was an early supporter of dissection and autopsy, which was expressed in his novel.

Life:

Born in Guadix near Granada, he was educated by Ibn Bajjah (Avempace). He served as a secretary for the ruler of Granada, and later as vizier and physician for Abu Yaqub Yusuf, the Almohad ruler of Al-Andalus, to whom he recommended Ibn Rushd (Averroës) as his own future successor in 1169. Ibn Rushd later reports this event and describes how Ibn Tufayl then inspired him to write his famous Aristotelian commentaries.

Hayy ibn Yaqdhan:

Ibn Tufail was the author of Hayy ibn Yaqdhan, also known as “Philosophus Autodidactus” in the West, a philosophical romance and allegorical novel inspired by Avicennism and Sufism, and which tells the story of an autodidactic feral child, raised by a gazelle and living alone on a desert island, who, without contact with other human beings, discovers ultimate truth through a systematic process of reasoned inquiry.

Hayy ultimately comes into contact with civilization and religion when he meets a castaway named Absal. He determines that certain trappings of religion, namely imagery, and dependence on material goods, are necessary for the multitude in order that they might have decent lives.

However, imagery and material goods are distractions from the truth and ought to be abandoned by those whose reason recognizes that they are distractions.

Ibn Tufail drew the name of the tale and most of its characters from an earlier work by Ibn Sina (Avicenna). Ibn Tufail’s book was neither a commentary nor a mere retelling of Ibn Sina’s work, however, but a new and innovative work in its own right.

It reflects one of the main concerns of Muslim philosophers (later also of Christian thinkers), that of reconciling philosophy with revelation. At the same time, the narrative anticipates in some ways both Robinson Crusoe and Rousseau’s Émile.

It tells of a child who is nurtured by a gazelle and grows up in total isolation from humans. In seven phases of seven years each, solely by the exercise of his faculties, Hayy goes through all the gradations of knowledge. The story of Hayy Ibn Yaqzan is similar to the later story of Mowgli in Rudyard Kipling’s The Jungle Book in that a baby is abandoned on a deserted tropical island where he is taken care of and fed by a mother wolf.

Ibn Tufail’s Philosophus Autodidactus was written as a response to al-Ghazali’s The Incoherence of the Philosophers. In the 13th century, Ibn al-Nafis later wrote the Al-Risalah al-Kamiliyyah fil Siera al-Nabawiyyah (known as Theologus Autodidactus in the West) as a response to Ibn Tufail’s Philosophus Autodidactus.

Hayy ibn Yaqdhan had a significant influence on both Arabic literature and European literature, and it went on to become an influential best-seller throughout Western Europe in the 17th and 18th centuries. The work also had a “profound influence” on both classical Islamic philosophy and modern Western philosophy.

It became “one of the most important books that heralded the Scientific Revolution” and European Enlightenment, and the thoughts expressed in the novel can be found “in different variations and to different degrees in the books of Thomas Hobbes, John Locke, Isaac Newton, and Immanuel Kant.”

A Latin translation of the work entitled Philosophus Autodidactus, first appeared in 1671, prepared by Edward Pococke the Younger. The first English translation (by Simon Ockley) was published in 1708. These translations later inspired Daniel Defoe to write Robinson Crusoe, which also featured a desert island narrative and was the first novel in English.

The novel also inspired the concept of “tabula rasa” developed in An Essay Concerning Human Understanding (1690) by John Locke, who was a student of Pococke. His Essay went on to become one of the principal sources of empiricism in modern Western philosophy and influenced many enlightenment philosophers, such as David Hume and George Berkeley.

Hayy’s ideas on materialism in the novel also have some similarities to Karl Marx’s historical materialism. It also foreshadowed Molyneux’s Problem, proposed by William Molyneux to Locke, who included it in the second book of An Essay Concerning Human Understanding. Other European writers influenced by Philosophus Autodidactus included Gottfried Leibniz, Melchisédech Thévenot, John Wallis, Christiaan Huygens, George Keith, Robert Barclay, the Quakers, Samuel Hartlib, and Voltaire.

Works:

English translations of Hayy bin Yaqdhan (in chronological order) The improvement of human reason, exhibited in the life of Hai ebn Yokdhan, written in Arabick above 500 years ago, by Abu Jaafar ebn Topsail, newly translated from the original Arabic, by Simon Ockley.

With an appendix, in which the possibility of man’s attaining the true knowledge of God, and things necessary to salvation, without instruction, is briefly considered. London: Printed and sold by E. Powell, 1708.

Abu Bakr Ibn Tufail, The History of Hayy Ibn Yaqdhan, translated from the Arabic by Simon Ockley, revised, with an introduction by A.S. Fulton. London: Chapman and Hall, 1929.

Ibn Tufayl’s Hayy ibn Yaqzan: a philosophical tale, translated with introduction and notes by Lenn Evan Goodman. New York: Twayne, 1972.

The journey of the soul: the story of Hai bin Yaqzan, as told by Abu Bakr Muhammad bin Tufail, a new translation by Riad Kocache. London Octagon, 1982.

Two Andalusian philosophers, translated from the Arabic with an introduction and notes by Jim Colville. London: Kegan Paul, 1999.

Medieval Islamic Philosophical Writings, ed. Muhammad Ali Khalidi. Cambridge University Press, 2005.

Follow the Neptune Prime channel on WhatsApp: https://whatsapp.com/channel/0029Va74ZvU2v1IqKByXoX3d

Do you have breaking news, interview request, opinion, suggestion, or want your event covered? Email us at neptuneprime2233@gmail.com