Abū Bakr ibn Muḥammad ibn al Ḥusayn al-Karajī (or al-Karkhī) (c. 953 in Karaj or Karkh – c. 1029) was a 10th-century Persian[1] or Arabic Muslim mathematician and engineer. His three major works are Al-Badi’ fi’l-hisab (Wonderful on calculation), Al-Fakhri fi’l-jabr wa’l-muqabala (Glorious on algebra), and Al-Kafi fi’l-hisab (Sufficient on calculation). Because al-Karaji’s original works in Arabic are lost, it is not certain what his exact name was. It could either have been al-Karkhī, indicating that he was born in Karkh, a suburb of Baghdad, or al-Karajī indicating his family came from the city of Karaj. He certainly lived and worked for most of his life in Baghdad, however, which was the scientific and trade capital of the Islamic world.


Al-Karaji wrote on mathematics and engineering. Some consider him to be merely reworking the ideas of others (he was influenced by Diophantus)[2] but most regard him as more original, in particular for the beginnings of freeing algebra from geometry.
He systematically studied the algebra of exponents, and was the first to realise that the sequence x, x^2, x^3,… could be extended indefinitely; and the reciprocals 1/x, 1/x^2, 1/x^3,… . However, since for example the product of a square and a cube would be expressed, in words rather than in numbers, as a square-cube, the numerical property of adding exponents was not clear.[3]
His work on algebra and polynomials gave the rules for arithmetic operations for adding, subtracting and multiplying polynomials; though he was restricted to dividing polynomials by monomials.
In a now lost work known only from subsequent quotation by al-Samaw’al Al-Karaji introduced the idea of argument by mathematical induction. As Katz says
Another important idea introduced by al-Karaji and continued by al-Samaw’al and others was that of an inductive argument for dealing with certain arithmetic sequences. Thus al-Karaji used such an argument to prove the result on the sums of integral cubes already known to Aryabhata […] Al-Karaji did not, however, state a general result for arbitrary n. He stated his theorem for the particular integer 10 […] His proof, nevertheless, was clearly designed to be extendable to any other integer. […] Al-Karaji’s argument includes in essence the two basic components of a modern argument by induction, namely the truth of the statement for n = 1 (1 = 13) and the deriving of the truth for n = k from that of n = k – 1. Of course, this second component is not explicit since, in some sense, al-Karaji’s argument is in reverse; this is, he starts from n = 10 and goes down to 1 rather than proceeding upward. Nevertheless, his argument in al-Fakhri is the earliest extant proof of the sum formula for integral cubes.[4]
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Hunayn ibn Ishaq

Hunayn ibn Ishaq   known in Latin as Johannitius) (809–873) was a famous and influential Assyrian[1] Nestorian Christian scholar, physician, and scientist, known for his work in translating Greek scientific and medical works into Arabic and Syriac during the heyday of the Islamic Abbasid Caliphate. Ḥunayn ibn Isḥaq was the most productive translator of Greek medical and scientific treatises in his day. He studied Greek and became known among the Arabs as the “Sheikh of the translators.” He mastered four languages: Arabic, Syriac, Greek and Persian. His translations did not require corrections. Hunayn’s method was widely followed by later translators. He was originally from southern Iraq but he spent his working life in Baghdad, the center of the great ninth-century Greek-into-Arabic/Syriac translation movement. His fame went far beyond his own community


In the Abbasid era, a new interest in extending the study of Greek science had arisen. At that time, there was a vast amount of untranslated ancient Greek literature pertaining to philosophy, mathematics, natural science, and medicine.[3][4] This valuable information was only accessible to a very small minority of Middle Eastern scholars who knew the Greek language; the need for an organized translation movement was urgent. In time, Hunayn ibn Ishaq became arguably the chief translator of the era, and laid the foundations of Islamic medicine.[3] In his lifetime, ibn Ishaq translated 116 works, including Plato’s Timaeus, Aristotle’s Metaphysics, and the Old Testament, into Syriac and Arabic.[4][5] Ibn Ishaq also produced 36 of his own books, 21 of which covered the field of medicine.[5] His son Ishaq, and his nephew Hubaysh, worked together with him at times to help translate. Hunayn ibn Ishaq is known for his translations, his method of translation, and his contributions to medicine.[4]

Early life

Hunayn ibn Ishaq was an Assyrian Christian born in 809, during the Abbasid period, in al-Hira, Iraq.[6][7] As a child, he learned the Syriac and Arabic languages. Although al-Hira was known for commerce and banking, and his father was a pharmacist, Hunayn went to Baghdad in order to study medicine. In Baghdad, Hunayn had the privilege to study under renowned physician Yuhanna ibn Masawayh; however, Hunayn’s countless questions irritated Yuhanna, causing him to scold Hunayn and forcing him to leave. Hunayn promised himself to return to Baghdad when he became a physician. He went abroad to master the Latin language. On his return to Baghdad, Hunayn displayed his newly acquired skills by reciting the works of Homer and Galen. In awe, ibn Masawayh reconciled with Hunayn, and the two started to work cooperatively.[7]
Hunayn was extremely motivated in his work to master Greek studies, which enabled him to translate Greek texts into Syriac and Arabic. The Abbasid Caliph al-Mamun noticed Hunayn’s talents and placed him in charge of the House of Wisdom, “Bayt al Hikmah.” The House of Wisdom was an institution where Greek works were translated and made available to scholars.[6] (Silvain Gougenheim argued, though, that there is no evidence of Hunayn being in charge of “Bayt al Hikham”[8]) The caliph also gave Hunayn the opportunity to travel to Byzantium in search of additional manuscripts, such as those of Aristotle and other prominent authors.[7]


In Hunayn ibn Ishaq’s lifetime, he devoted himself to working on a multitude of writings; both translations and original works.[7]

As a writer of original work

Hunayn wrote on a variety of subjects that included philosophy, religion and medicine. In “How to Grasp Religion,” Hunayn explains the truths of religion that include miracles not possibly made by humans and humans’ incapacity to explain facts about some phenomena, and false notions of religion that include depression and an inclination for glory. He worked on Arabic grammar and lexicography.[7]


Hunayn ibn Ishaq enriched the field of ophthalmology. His developments in the study of the human eye can be traced through his innovative book, “Ten Treatises on Ophthalmology.” This textbook is the first known systematic treatment of this field and was most likely used in medical schools at the time. Throughout the book, Hunayn explains the eye and its anatomy in minute detail; its diseases, their symptoms, their treatments. He discusses the nature of cysts and tumors, and the swelling they cause. He discusses how to treat various corneal ulcers through surgery, and the therapy involved in repairing cataracts. “Ten Treatises on Ophthalmology” demonstrates the skills Hunayn ibn Ishaq had not just as a translator and a physician, but also as a surgeon.[5]

As a physician

Hunayn ibn Ishaq’s reputation as a scholar and translator, and his close relationship with Caliph al-Mutawakkil, led the caliph to name Hunayn as his personal physician, ending the exclusive use of physicians from the Bukhtishu family.[7] Despite their relationship, the caliph became distrustful; at the time, there were fears of death from poisoning, and physicians were well aware of its synthesis procedure. The caliph tested Hunayn’s ethics as a physician by asking him to formulate a poison, to be used against a foe, in exchange for a large sum. Hunayn ibn Ishaq repeatedly rejected the Caliph’s generous offers, saying he would need time to develop a poison. Disappointed, the caliph imprisoned his physician for a year. When asked why he would rather be killed than make the drug, Hunayn explained the physician’s oath required him to help, and not harm, his patients.[6]

As a translator

Some of Hunayn’s most notable translations were his translation of “De materia Medica,” which was technically a pharmaceutical handbook, and his most popular selection, “Questions on Medicine.”[4] “Questions on Medicine” was extremely beneficial to medical students because it was a good guide for beginners to become familiar with the fundamental aspects of medicine in order to understand the more difficult materials. Information was presented in the form of question and answer. The questions were taken from Galen’s “Art of Physic,” and the answers were based on “Summaria Alexandrinorum.” For instance, Hunayn answers what the four elements and four humors are and also explains that medicine is divided into therapy and practice. He goes on later to define health, disease, neutrality, and also natural and contranatural, which associates with the six necessary causes to live healthy.[7]
Hunayn translated writings on agriculture, stones, and religion. He translated some of Plato’s and Aristotle’s works, and the commentaries of ancient Greeks. Additionally, Hunayn translated many medicinal texts and summaries, mainly those of Galen. He translated a countless number of Galen’s works including “On Sects” and “On Anatomy of the Veins and Arteries.”[7]Many published works of R. Duval in Chemistry represent translations of Hunayn’s work.[9] Also in Chemistry a book titled [‘An Al-Asma’] meaning “About the Names”, did not reach researchers but was used in “Dictionary of Ibn Bahlool” of the 10th century.

Translation techniques

In his efforts to translate as much Greek material as possible, Hunayn ibn Ishaq was accompanied by his son Ishaq ibn Hunayn and his nephew Hubaysh. It was quite normal at times for Hunayn to translate Greek material into Syriac, and have his nephew finish by translating the text from Syriac to Arabic. Ishaq corrected his partners’ errors while translating writings in Greek and Syriac into Arabic.[4]
Unlike other translators in the Abbasid period, Hunayn opposed translating texts word for word. Instead, he would attempt to attain the meaning of the subject and the sentences, and then in a new manuscript, rewrite the piece of knowledge in Syriac or Arabic.[4] He also corrected texts by collecting different set of books revolving around a subject and by finalizing the meaning of the subject.[7] The method helped gather, in just 100 years, nearly all the knowledge from Greek medicine.[4].[2]
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Banū Mūsā

The Banū Mūsā brothers (“Sons of Moses”), namely Abū Jaʿfar, Muḥammad ibn Mūsā ibn Shākir (before 803 – February 873), Abū al‐Qāsim, Aḥmad ibn Mūsā ibn Shākir (d. 9th century) and Al-Ḥasan ibn Mūsā ibn Shākir (d. 9th century), were three 9th-century Islamic scholars of Baghdad who are known for their Book of Ingenious Devices on automata (automatic machines) and mechanical devices. Another important work of theirs is the Book on the Measurement of Plane and Spherical Figures, a foundational work on geometry that was frequently quoted by both Islamic and European mathematicians.[2]The Banu Musa worked in astronomical observatories established in Baghdad by the Abbasid Caliph al-Ma’mun as well as doing research in the House of Wisdom. They also participated in a 9th-century expedition to make geodesic measurements to determine the length of a degree


The Banu Musa were the three sons of Mūsā ibn Shākir, who earlier in life had been a highwayman and astronomer in Khorasan of unknown pedigree.[3] After befriending al-Ma’mun, who was then a governor of Khorasan and staying in Marw, Musa was employed as an astrologer and astronomer.[4] After his death, his young sons were looked after by the court of al-Maʾmūn.[5] Al-Maʾmūn recognized the abilities of the three brothers and enrolled them in the famous House of Wisdom, a library and a translation center in Baghdad.[6]Studying in the House of Wisdom under Yahya ibn Abi Mansur,[4] they participated in the efforts to translate ancient Greek works into Arabic by sending for Greek texts from the Byzantines, paying large sums for their translation, and learning Greek themselves.[5] On such trips, Muhammad met and recruited the famous mathematician and translator Thābit ibn Qurra. At some point Hunayn ibn Ishaq was also part of their team.[2]After the death of al-Ma’mun, the Banu Musa continued to work under the Caliphs al-Mu’tasim, al-Wathiq, and al-Mutawakkil. However, during the reign of al-Wathiq and al-Mutawakkil internal rivalries arose between the scholars in the House of Wisdom. At some point the Banu Musa became enemies to al-Kindi and contributed to his persecution by al-Mutawakkil. They were later employed by al-Mutawakkil to construct a canal for the new city of al-Jafariyya.[1]


The Banu Musa wrote almost 20 books the majority of which are now lost.[2]


Most notable among their achievements is their work in the field of automation, which they utilized in toys and other entertaining creations. They have shown important advances over those of their Greek predecessors.[2]
  • The Book of Ingenious Devices describes 100 inventions; the ones which have been reconstructed work as designed. While designed primarily for amusement purposes, they employ innovative engineering technologies such as one-way and two-way valves able to open and close by themselves, mechanical memories, devices to respond to feedback, and delays. Most of these devices were operated by water pressure.[5]
  • Qarasṭūn, a treatise on weight balance.[6]
  • On Mechanical Devices, a work on pneumatic devices, written by Ahmad.[6]
  • A Book on the Description of the Instrument Which Sounds by Itself, about musical theory.[6]


  • Book on the First Motion of the Celestial Sphere (Kitāb Ḥarakāt al‐falak al‐ūlā), containing a critique of the Ptolemaic system. Muhammad in this book denied the existence of the Ptolemaic 9th sphere which Ptolemy thought was responsible for the motion.[2]
  • Book on the Mathematical Proof by Geometry That There Is Not a Ninth Sphere Outside the Sphere of the Fixed Stars, by Ahmad.
  • Book on The Construction of the Astrolabe, quoted by al-Biruni.[2]
  • Book on the Solar Year, was traditionally attributed to Thābit ibn Qurra, but recent research has shown that it was actually by the Bani Musa.[2]
  • On the Visibility of the Crescent, by Muhammad.
  • Book on the Beginning of the World, by Muhammad.
  • Book on the Motion of Celestial Spheres (Kitāb Ḥarakāt al‐aflāk), by Muhammad.
  • Book of Astronomy (Kitāb al‐Hayʾa), by Muhammad.
  • A book of zij, by Ahmad
  • Another book of zij, listed under the Banu Musa, mentioned by Ibn Yunus.[2].[2]
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Abu’l-Barakāt al-Baghdādī

Abu’l-Barakāt Hibat Allah ibn Malkā al-Baghdādī  c. 1080 – 1164 or 1165 CE) was an Islamic philosopher and physician of Jewish-Arab descent from Baghdad, Iraq. Abu’l-Barakāt, an older contemporary of Maimonides, was originally known by his Hebrew birth name Nathanel before his conversion from Judaism to Islam towards the end of his life.[1]His writings include the anti-Aristotelian philosophical work Kitāb al-Muʿtabar (“The Book of What Has Been Established by Personal Reflection”); a philosophical commentary on the Kohelet; and the treatise “On the Reason Why the Stars Are Visible at Night and Hidden in Daytime”. Abu’l-Barakāt was an Aristotelian philosopher who in many respects followed Ibn Sina, but also developed his own ideas.[2] He proposed an explanation of the acceleration of falling bodies by the accumulation of successive increments of power with successive increments of velocity. His thought influenced the Illuminationist school of classical Islamic philosophy, the medieval Jewish philosopher Ibn Kammuna,[3] and the medieval Christian philosophers Jean Buridan and Albert of Saxony


Abu’l-Barakāt, famed as Awḥad al-Zamān (Unique One of his Time), was born in Balad, a town on the Tigris above Mosul in modern-day Iraq. As a renowned physician, he served at the courts of the caliphs of Baghdad and the Seljuk sultans.[5]He converted to Islam in old age. Abu’l Barakat does not refer to his conversion in his writings, and the historical sources give contradictory episodes of his conversion. According to the various reports, he converted either out of “wounded pride”, fear of the personal consequences of the death of Sultan Mahmud‘s wife while under his care as a physician or fear of execution when he was taken prisoner in a battle between the armies of the caliph and that of the sultan. Ayala Eliyahu argues that the conversion was “probably motivated by convenience reasons”.[6][7][8][9]Isaac, the son of the Abraham Ibn Ezra and the son-in-law of Judah Halevi,[9] was one of his pupils,[6] to whom Abu’l-Barakāt, Jewish at the time, dictated a long philosophical commentary on Ecclesiastes, written in Arabic using Hebrew aleph bet. Isaac wrote a poem in his honour as introduction to this work.[5]


Experimental method

Al-Baghdaadi described an early scientific method emphasizing repeated experimentation, influenced by Ibn Sina, as follows:[10]
“Because of the frequency of the experience, these judgements may be regarded as certain, even without our knowing the reason [for the phenomenon]. For there is certain knowledge that the effect in question is not due to chance. It must accordingly be supposed that it is due to nature or to some modality thereof. Thus the cause qua cause, though not its species or mode of operation, is known. For experimental science is also constituted by a knowledge of the cause and by an induction based on all the data of sensation; whereby a general science is reached. … But in the cases in which an experiment has not been completed, because of its not having been repeated in such a way that the persons, the time and the circumstances varied in everything that did not cause the determining cause, whereas this cause [remained invariable], the experiment does not prove certain knowledge, but only probably opinion.”


According to Alistair Cameron Crombie, al-Baghdaadi was a follower of the scientific and philosophical teachings of Ibn Sina.
proposed an explanation of the acceleration of falling bodies by the accumulation of successive increments of power with successive increments of velocity.[11]
According to Shlomo Pines, al-Baghdaadi’s theory of motion was thus
the oldest negation of Aristotle‘s fundamental dynamic law [namely, that a constant force produces a uniform motion], [and is thus an] anticipation in a vague fashion of the fundamental law of classical mechanics [namely, that a force applied continuously produces acceleration].[12]
Al-Baghdaadi’s theory of motion distinguished between velocity and acceleration and showed that force is proportional to acceleration rather than velocity.[4][13] The 14th-century philosophers Jean Buridan and Albert of Saxony later refer to Abu’l-Barakat in explaining that the acceleration of a falling body is a result of its increasing impetus. Abu’l-Barakat also modified Ibn Sina‘s theory of projectile motion, and stated that the mover imparts a violent inclination (mayl qasri) on the moved and that this diminishes as the moving object distances itself from the mover.[4]Al-Baghdaadi also suggested that motion is relative, writing that “there is motion only if the relative positions of the bodies in question change.” He also stated that “each type of body has a characteristic velocity that reaches its maximum when its motion encounters no resistance.”[3]

Space and Time

Al-Baghdaadi criticized Aristotle’s concept of time as “the measure of motion” and instead redefines the concept with his own definition of time as “the measure of being”, thus distinguishing between space and time, and reclassifying time as a metaphysical concept rather than a physical one. The scholar Y. Tzvi Langermann writes:[3]
Dissatisfied with the regnant approach, which treated time as an accident of the cosmos, al-Baghdadi drew the conclusion that time is an entity whose conception (ma’qul al-zaman) is a priori and almost as general as that of being, encompassing the sensible and the non-sensible, that which moves and that which is at rest. Our idea of time results not from abstraction, stripping accidents from perceived objects, but from a mental representation based on an innate idea. Al-Baghdadi stops short of offering a precise definition of time, stating only that ‘were it to be said that time is the measure of being (miqdar al-wujud), that would be better than saying [as Aristotle does] that it is the measure of motion’. His reclassification of time as a subject for metaphysics rather than for physics represents a major conceptual shift, not a mere formalistic correction. It also breaks the traditional linkage between time and space. Concerning space, al-Baghdadi held unconventional views as well, but he did not remove its investigation from the domain of physics.
In his view, there is just one time which is similar for all beings, including God. Abu’l-Barakāt also regarded space as three-dimensional and infinite.[14]


He upheld the unity of the soul, denying that there is a distinction between it and the intellect.[14] For him, the soul’s awareness of itself is the definitive proof that the soul is independent of the body and will not perish with it.[2] On his contributions to Islamic psychology, Langermann writes:[3]
Al-Baghdadi’s most significant departure in psychology concerns human self-awareness. Ibn Sina had raised the issue of our consciousness of our own psychic activities, but he had not fully pursued the implications for Aristotelian psychology of his approach. Al-Baghdadi took the matter much further, dispensing with the traditional psychological faculties and pressing his investigations in the direction of what we would call the unconscious.


He wrote a critique of Aristotelian philosophy and Aristotelian physics entitled Kitab al-Mu’tabar (the title may be translated as “The Book of What Has Been Established by Personal Reflection”). According to Abu’l-Barakāt, Kitāb al-Muʿtabar consists in the main of critical remarks jotted down by him over the years while reading philosophical text, and published at the insistence of his friends, in the form of a philosophical work. The work “presented a serious philosophical alternative to, and criticism of, Ibn Sina“.[15] He also developed concepts which resemble several modern theories in physics.[3]Abu’l-Barakāt also wrote a short treatise on the intellect, Kitāb Ṣaḥiḥ adillat al-naql fī māhiyyat al-ʻaql (صحيح أدلة النقل في ماهية العقل), which has been edited by Ahmad El-Tayeb.[16]All that we possess in the way of medical writing by Abu’l-Barakāt are a few prescriptions for remedies. These remain in manuscript and are as yet unstudied.[17]


Abu’l-Barakāt’s thought had a deep influence on Islamic philosophy but none on Jewish thought. His works were not translated into Hebrew,[14] and he is seldom cited in Jewish philosophy, probably because of his conversion to Islam.[7]
The famous theologian and philosopher Fakhr al-Din al-Razi was one of Abu’l-Barakāt’s eminent disciples. The influence of Al-Baghdadi’s views appears especially in Al-Razi’s chief work Al-Mabāḥith al-Mashriqiyyah (Oriental Discourses). Abu’l-Barakāt influenced certain conceptions of Suhrawardi.[18].[4]
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‘Ali ibn al-‘Abbas al-Majusi

Ali ibn al-‘Abbas al-Majusi (died 982-994), also known as Masoudi, or Latinized as Haly Abbas, was a Persian physician and psychologist most famous for the Kitab al-Maliki or Complete Book of the Medical Art, his textbook on medicine and psychology.


He was born in Ahvaz, southwestern Persia, and studied under Shaikh Abu Maher Musa ibn Sayyār. He was considered one of the three greatest physicians of the Eastern Caliphate of his time, and became physician to Emir ‘Adud al-Daula Fana Khusraw of the Buwayhid dynasty, who ruled from 949 CE to 983 CE. The Emir was a great patron of medicine, and founded a hospital at Shiraz in Persia, and in 981 the Al-Adudi Hospital in Baghdad, where al-Majusi worked. His ancestors were Zoroastrian, but he himself was a Muslim. His reverence for Allah is evident in the worship and styles of expression throughout his work.[1]

The Complete Art of Medicine

Al-Majusi is best known for his Kitāb Kāmil aṣ-Ṣināʿa aṭ-Ṭibbiyya (كتاب كامل الصناعة الطبيةComplete Book of the Medical Art“), later called The Complete Art of Medicine,[1] which he completed circa 980. He dedicated the work to the Emir, and it became known as the Kitāb al-Malakiyy (كتاب الملكي, “Royal Book“, or in Latin Liber Regalis or Regalis Dispositio). The book is a more systematic and concise encyclopedia than Razi‘s Hawi, and more practical than Avicenna‘s The Canon of Medicine, by which it was superseded.[citation needed]
The Maliki is divided into 20 discourses, of which the first ten deal with theory and the second ten with the practice of medicine. Some examples of topics covered are dietetics and materia medica, a rudimentary conception of the capillary system, interesting clinical observations, and proof of the motions of the womb during parturition (for example, the child does not come out, but is pushed out).
In Europe a partial Latin translation was adapted as the Liber pantegni by Constantinus Africanus (c. 1087), which became a founding text of the Schola Medica Salernitana in Salerno. A complete and much better translation was made in 1127 by Stephen of Antioch, and this was printed in Venice in 1492 and 1523. Haly’s book of medicine is cited in Chaucer‘s Canterbury Tales.

Medical ethics and research methodology

The work emphisized the need for a healthy relationship between doctors and patients, and the importance of medical ethics. It also provided details on a scientific methodology that is similar to modern biomedical research.[2]

Neuroscience and psychology

Neuroscience and psychology were discussed in The Complete Art of Medicine. He described the neuroanatomy, neurobiology and neurophysiology of the brain and first discussed various mental disorders, including sleeping sickness, memory loss, hypochondriasis, coma, hot and cold meningitis, vertigo epilepsy, love sickness, and hemiplegia. He placed more emphasis on preserving health through diet and natural healing than he did on medication or drugs, which he considered a last resort.[1]

Psychophysiology and psychosomatic medicine

Ali ibn Abbas al-Majusi was a pioneer in psychophysiology and psychosomatic medicine. He described how the physiological and psychological aspects of a patient can have an effect on one another in his Complete Book of the Medical Art. He found a correlation between patients who were physically and mentally healthy and those who were physically and mentally unhealthy, and concluded that “joy and contentment can bring a better living status to many who would otherwise be sick and miserable due to unnecessary sadness, fear, worry and anxiety.”[3]
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Al-Farabi  Abū Naṣr Muḥammad ibn Muḥammad Fārābī;[1] for other recorded variants of his name see below) known in the West as Alpharabius[5] (c. 872[2] in Fārāb[3] – between 14 December, 950 and 12 January, 951 in Damascus),[3] was a renowned scientist and philosopher of the Islamic Golden Age. He was also a cosmologist, logician, and musician. Through his commentaries and treatises, Al-Farabi became well known among medieval Muslim intellectuals as “The Second Teacher”, that is, the successor to Aristotle, “The First Teacher”.


The existing variations in the basic accounts of al-Farabi’s origins and pedigree indicate that they were not recorded during his lifetime or soon thereafter by anyone with concrete information, but were based on hearsay or guesses (as is the case with other contemporaries of al-Farabi).[1] The sources for his life are scant which makes the reconstruction of his biography beyond a mere outline nearly impossible.[1] The earliest and more reliable sources, i.e., those composed before the 6th/12th century, that are extant today are so few as to indicate that no one among Fārābī’s successors and their followers, or even unrelated scholars, undertook to write his full biography, a neglect that has to be taken into consideration in assessing his immediate impact.[1] The sources prior to the 6th/12th century consist of: (1) an autobiographical passage by Farabi, preserved by Ibn Abī Uṣaibiʿa. In this passage, Farabi traces the transmission of the instruction of logic and philosophy from antiquity to his days. (2) Reports by Al-Masudi, Ibn al-Nadim and Ibn Hawqal as well as by Said Al-Andalusi (d. 1070), who devoted a biography to him.
When major Arabic biographers decided to write comprehensive entries on Farabi in the 6th-7th/12th-13th centuries, there was very little specific information on hand; this allowed for their acceptance of invented stories about his life which range from benign extrapolation on the basis of some known details to tendentious reconstructions and legends.[1] Most modern biographies of the philosopher present various combinations of elements drawn at will from this concocted material.[1] The sources from the 6th/12th century and later consist essentially of three biographical entries, all other extant reports on Farabi being either dependent on them or even later fabrications:[1] 1) the Syrian tradition represented by Ibn Abī Uṣaibiʿa.[1] 2) The Wafayāt al-aʿyān wa-anbāʾ abnāʾ az-zamān (“Deaths of Eminent Men and History of the Sons of the Epoch”; trans. by Baron de Slane, Ibn Khallikan’s Biographical Dictionary, 1842–74) compiled by Ibn Khallikān.[1] 3) the scanty and legendary Eastern tradition, represented by Ẓahīr-al-Dīn Bayhaqī.[1]From incidental accounts it is known that he spent significant time in Baghdad with Christian scholars including the cleric Yuhanna ibn Haylan, Yahya ibn Adi, and Abu Ishaq Ibrahim al-Baghdadi. He later spent time in Damascus, Syria and Egypt before returning to Damascus where he died in 950-1.[6][page needed]


His name was Abū Naṣr Muḥammad b. Muḥammad Farabi, as all sources, and especially the earliest and most reliable, Al-Masudi, agree.[1] In some manuscripts of Fārābī’s works, which must reflect the reading of their ultimate archetypes from his time, his full name appears as Abū Naṣr Muḥammad b. Muḥammad al-Ṭarḵānī, i.e., the element Ṭarḵān appears in a nisba (family surname or attributive title).[1] Moreover, if the name of Farabi’s grandfather was not known among his contemporaries and immediately succeeding generations, it is all the more surprising to see in the later sources the appearance of yet another name from his pedigree, Awzalaḡ.[1] This appears as the name of the grandfather in Ibn Abī Uṣaibiʿa and of the great-grandfather in Ibn Khallikān. Ibn Abī Uṣaibiʿa is the first source to list this name which, as Ibn Khallikān explicitly specifies later, is so to be pronounced as Awzalaḡ.[1] In modern Turkish scholarship and some other sources, the pronunciation is given as Uzluḡ rather than Awzalaḡ, without any explanation.[1]


His birthplace is given in the classical sources as either Fāryāb in Greater Khorasan (modern day Afghanistan)[1] or Fārāb on the Jaxartes (Syr Darya) in modern Kazakhstan.[1] The older Persian[1] Pārāb (in Ḥudūd al-ʿĀlam) or Fāryāb (also Pāryāb), is a common Persian toponym meaning “lands irrigated by diversion of river water”.[7][8] By the 13th century, Fārāb on the Jaxartes was known as Otrār.[9]


There is a difference of opinion on the ethnic background of Farabi.[1][10][11] According to Dimitri Gutas, “[…] ultimately pointless as the quest for Farabi’s ethnic origins might be, the fact remains that we do not have sufficient evidence to decide the matter […]”[1] The Cambridge companion to Arabic philosophy also states that “[…] these biographical facts are paltry in the extreme but we must resist the urge to embellish them with fanciful stories, as the medieval biographers did, or engage in idle speculation about al-Farabi’s ethnicity or religious affiliation on the basis of contrived interpretations of his works, as many modern scholars have done.”[12] According to the Oxford Encyclopaedia of African Thought “[…] because the origins of al-Farabi were not recorded during his lifetime or soon after his death in 950 C.E. by anyone with concrete information, accounts of his pedigree and place of birth have been based on hearsay […]”.[13]
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Abu Zayd al-Balkhi

Abu Zayd Ahmed ibn Sahl Balkhi   was a Persian Muslim polymath: a geographer, mathematician, physician, psychologist and scientist. Born in 850 CE in Shamistiyan, in the Persian province of Balkh, Khorasan (in modern day Afghanistan), he was a disciple of al-Kindi. He was also the founder the “Balkhī school” of terrestrial mapping in Baghdad


Of the many books ascribed to him in the al-Fihrist by Ibn al-Nadim, one can note the excellency of mathematics; on certitude in astrology. His Figures of the Climates (Suwar al-aqalim) consisted chiefly of geographical maps. He also wrote the medical and psychological work, Masalih al-Abdan wa al-Anfus (Sustenance for Body and Soul).

Figures of the Regions

His Figures of the Regions (Suwar al-aqalim) consisted chiefly of geographical maps. It led to him founding the “Balkhī school” of terrestrial mapping in Baghdad. The geographers of this school also wrote extensively of the peoples, products, and customs of areas in the Muslim world, with little interest in the non-Muslim realms.[1]

Sustenance for Body and Soul

Mental health and mental illness

In Islamic psychology and neuroscience, the concepts of mental health and “mental hygiene” were introduced by Abu Zayd al-Balkhi, who often related it to spiritual health. In his Masalih al-Abdan wa al-Anfus (Sustenance for Body and Soul), he was the first to successfully discuss diseases related to both the body and the soul. He used the term al-Tibb al-Ruhani to describe spiritual and psychological health, and the term Tibb al-Qalb to describe mental medicine. He criticized many medical doctors in his time for placing too much emphasis on physical illnesses and neglecting the psychological or mental illnesses of patients, and argued that “since man’s construction is from both his soul and his body, therefore, human existence cannot be healthy without the ishtibak [interweaving or entangling] of soul and body.” He further argued that “if the body gets sick, the nafs [psyche] loses much of its cognitive and comprehensive ability and fails to enjoy the desirous aspects of life” and that “if the nafs gets sick, the body may also find no joy in life and may eventually develop a physical illness.” Al-Balkhi traced back his ideas on mental health to verses of the Qur’an and hadiths attributed to Muhammad, such as:[2]
“In their hearts is a disease.”
Qur’an 2:10
“Truly, in the body there is a morsel of flesh, and when it is corrupt the body is corrupt, and when it is sound the body is sound. Truly, it is the qalb [heart].”
Sahih al-Bukhari, Kitab al-Iman
“Verily Allah does not consider your appearances or your wealth in (appraising you) but He considers your hearts and your deeds.”

Cognitive and medical psychology and cognitive therapy

Abu Zayd al-Balkhi was the first known cognitive psychologist and medical psychologist, the first to differentiate between neurosis and psychosis, and the first to classify neurotic disorders and pioneer cognitive therapy in order to treat each of these classified disorders. He classified neurosis into four emotional disorders: fear and anxiety, anger and aggression, sadness and depression, and obsession. He further classified three types of depression: normal depression or sadness (huzn), endogenous depression originating from within the body, and reactive clinical depression originating from outside the body. He also wrote that a healthy individual should always keep healthy thoughts and feelings in his mind in the case of unexpected emotional outbursts in the same way drugs and First Aid medicine are kept nearby for unexpected physical emergencies. He stated that a balance between the mind and body is required for good health and that an imbalance between the two can cause sickness. Al-Balkhi also introduced the concept of reciprocal inhibition (al-ilaj bi al-did), which was re-introduced over a thousand years later by Joseph Wolpe in 1969.[3]

Psychophysiology and psychosomatic medicine

The Muslim physician Abu Zayd al-Balkhi was a pioneer of psychotherapy, psychophysiology and psychosomatic medicine. He recognized that the body and the soul can be healthy or sick, or “balanced or imbalanced”, and that mental illness can have both psychological and/or physiological causes. He wrote that imbalance of the body can result in fever, headaches and other physical illnesses, while imbalance of the soul can result in anger, anxiety, sadness and other mental symptoms. He recognized two types of depression: one caused by known reasons such as loss or failure, which can be treated psychologically through both external methods (such as persuasive talking, preaching and advising) and internal methods (such as the “development of inner thoughts and cognitions which help the person get rid of his depressive condition”); and the other caused by unknown reasons such as a “sudden affliction of sorrow and distress, which persists all the time, preventing the afflicted person from any physical activity or from showing any happiness or enjoying any of the pleasures” which may be caused by physiological reasons (such as impurity of the blood) and can be treated through physical medicine.[2] He also wrote comparisons between physical disorders with mental disorders, and showed how psychosomatic disorders can be caused by certain interactions between them.[3.[1]
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Abu Yūsuf Yaʻqūb ibn ʼIsḥāq aṣ-Ṣabbāḥ al-Kindī   (c. 801–873 CE), known as “the Philosopher of the Arabs”, was an Iraqi Muslim Arab 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[2][3][4] for his synthesis, adaptation and promotion of Greek and Hellenistic philosophy in the Muslim world.[5]Al-Kindi was a descendant of the Kinda tribe. He was born and educated in Basra,[6] before going to pursue further studies in Baghdad. Al-Kindi became a prominent figure in the House of Wisdom, and a number of Abbasid Caliphs appointed him to oversee the translation of Greek scientific and philosophical texts into the Arabic language.
This contact with “the philosophy of the ancients” (as Greek philosophy was often referred to by Muslim scholars) had a profound effect on his intellectual development, and led him to write hundreds of original treatises of his own on a range of subjects ranging from metaphysics, ethics, logic and psychology, to medicine, pharmacology,[7] mathematics, astronomy, astrology and optics, and further afield to more practical topics like perfumes, swords, jewels, glass, dyes, zoology, tides, mirrors, meteorology and earthquakes.[8][9]In the field of mathematics, al-Kindi played an important role in introducing Indian numerals to the Islamic and Christian world.[10] He was a pioneer in cryptanalysis and devised several new methods of breaking ciphers.[11
 Using his mathematical and medical expertise, he was able to develop a scale that would allow doctors to quantify the potency of their medication.[12]The central theme underpinning al-Kindi’s philosophical writings is the compatibility between philosophy and other “orthodox” Islamic sciences, particularly theology. And many of his works deal with subjects that theology had an immediate interest in. These include the nature of God, the soul and prophetic knowledge.[13] But despite the important role he played in making philosophy accessible to Muslim intellectuals, his own philosophical output was largely overshadowed by that of al-Farabi and very few of his texts are available for modern scholars to examine.


Al-Kindi was born in Kufa to an aristocratic family of the Kinda tribe. 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.[14]When al-Ma’mun died, his brother, al-Mu’tasim became Caliph. Al-Kindi’s position would be enhanced under al-Mu’tasim, who appointed him as a tutor to his son.
But on the accession of al-Wathiq, and especially of al-Mutawakkil, al-Kindi’s star waned. There are various theories concerning this: some attribute al-Kindi’s downfall to scholarly rivalries at the House of Wisdom; others refer to al-Mutawakkil’s often violent persecution of unorthodox Muslims (as well as of non-Muslims); at one point al-Kindi was beaten and his library temporarily confiscated. Henry Corbin, an authority on Islamic studies, says that in 873, al-Kindi died “a lonely man”, in Baghdad during the reign of Al-Mu’tamid.[14]After his death, al-Kindi’s philosophical works quickly fell into obscurity and many of them were lost even to later Islamic scholars and historians. Felix Klein-Franke suggests a number of reasons for this: aside from the militant orthodoxy of al-Mutawakkil, the Mongols also destroyed countless libraries during their invasion. However, he says the most probable cause of this was that his writings never found popularity amongst subsequent influential philosophers such as al-Farabi and Avicenna, who ultimately overshadowed him.[15]


Al-Kindi was a master of many different areas of thought. And although he would eventually be eclipsed by names such as al-Farabi and Avicenna, he was held to be one of the greatest Islamic philosophers of his time. The Italian Renaissance scholar Geralomo Cardano (1501–1575) considered him one of the twelve greatest minds of the Middle Ages.[16] 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).[17] His influence in the fields of physics, mathematics, medicine, philosophy and music were 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.[18]


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 (Bayt al-Hikma), an institute of translation and learning patronized by the Abbasid Caliphs, in Baghdad.[14] 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.[19]
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.[20]


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 varies according to the arrangement of heavenly bodies situated above their homeland.[21]
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 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.[22]
Some of the notable astrological works by al-Kindi include:[23]
  • 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 mutatione 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, Euclidian 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.[24]Through the Latin version of the De Aspectibus, Al-Kindi partly influenced the optical investigations of Robert Grosseteste.[25]


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.[26] 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 drug and a system, based the phases of the moon, that would allow a doctor to determine in advance the most critical days of a patient’s illness.[12]


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.[27] He is sometimes credited as one of the first distillers of alcohol.


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.[10] 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.[28]
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Muhammad ibn Hasan Tūsī

Khawaja Muhammad ibn Muhammad ibn Hasan Tūsī  (born 18 February 1201 in Ṭūs, Khorasan – died on 26 June 1274 in al-Kāżimiyyah district of metropolitan Baghdad), better known as Nasīr al-Dīn Tūsī (Persian: نصیر الدین طوسی‎; or simply Tusi in the West), was a Persian[1][2][3][4] polymath and prolific writer: an architect, astronomer, biologist, chemist, mathematician, philosopher, physician, physicist, scientist, theologian and Marja Taqleed.[citation needed] He was of the Ismaili-, and subsequently Twelver Shī‘ah Islamic belief.[5] The Muslim scholar Ibn Khaldun (1332–1406) considered Tusi to be the greatest of the later Persian scholars


Nasir al-Din Tusi was born in the city of Tus in medieval Khorasan (in north-eastern Iran) in the year 1201 and began his studies at an early age. In Hamadan and Tus he studied the Qur’an, Hadith, Shi’a jurisprudence, logic, philosophy, mathematics, medicine and astronomy.[7]
He was apparently born into a Shī‘ah family and lost his father at a young age. Fulfilling the wish of his father, the young Muhammad took learning and scholarship very seriously and travelled far and wide to attend the lectures of renowned scholars and acquire the knowledge which guides people to the happiness of the next world. At a young age he moved to Nishapur to study philosophy under Farid al-Din Damad and mathematics under Muhammad Hasib.[8] He met also Farid al-Din ‘Attar, the legendary Sufi master who was later killed by Mongol invaders and attended the lectures of Qutb al-Din al-Misri.
In Mosul he studied mathematics and astronomy with Kamal al-Din Yunus (d. 639/1242). Later on he corresponded with Sadr al-Din al-Qunawi, the son-in-law of Ibn al-‘Arabi, and it seems that mysticism, as propagated by Sufi masters of his time, was not appealing to his mind and once the occasion was suitable, he composed his own manual of philosophical Sufism in the form of a small booklet entitled Awsaf al-Ashraf “The Attributes of the Illustrious”.
As the armies of Genghis Khan swept his homeland, he was captured by the Ismailis and made his most important contributions in science during this time when he was moving from one stronghold to another. He finally joined Hulagu Khan‘s ranks, after the invasion of the Alamut castle by the Mongol forces.


Kitāb al-Shakl al-qattāʴ Book on the complete quadrilateral. A five volume summary of trigonometry.
  • Al-Tadhkirah fi’ilm al-hay’ah – A memoir on the science of astronomy. Many commentaries were written about this work called Sharh al-Tadhkirah (A Commentary on al-Tadhkirah) – Commentaries were written by Abd al-Ali ibn Muhammad ibn al-Husayn al-Birjandi and by Nazzam Nishapuri.
  • Akhlaq-i-Nasri – A work on ethics.
  • al-Risalah al-Asturlabiyah – A Treatise on astrolabe.
  • Zij-i ilkhani (Ilkhanic Tables) – A major astronomical treatise, completed in 1272.
  • sharh al-isharat (Commentary on Avicenna’s Isharat)
  • Awsaf al-Ashraf a short mystical-ethical work in Persian
  • Tajrīd al-iʿtiqād (Summation of Belief) – A commentary on Shia doctrines.


During his stay in Nishapur, Tusi established a reputation as an exceptional scholar. “Tusi’s prose writing, which number over 150 works, represent one of the largest collections by a single Islamic author. Writing in both Arabic and Persian, Nasir al-Din Tusi dealt with both religious (“Islamic”) topics and non-religious or secular subjects (“the ancient sciences”).[9] His works include the definitive Arabic versions of the works of Euclid, Archimedes, Ptolemy, Autolycus, and Theodosius of Bithynia.[9]


Tusi convinced Hulegu Khan to construct an observatory for establishing accurate astronomical tables for better astrological predictions. Beginning in 1259, the Rasad Khaneh observatory was constructed in Azarbaijan, west of Maragheh, the capital of the Ilkhanate Empire.
Based on the observations in this for the time being most advanced observatory, Tusi made very accurate tables of planetary movements as depicted in his book Zij-i ilkhani (Ilkhanic Tables). This book contains astronomical tables for calculating the positions of the planets and the names of the stars. His model for the planetary system is believed to be the most advanced of his time, and was used extensively until the development of the heliocentric model in the time of Nicolaus Copernicus. Between Ptolemy and Copernicus, he is considered by many to be one of the most eminent astronomers of his time.
For his planetary models, he invented a geometrical technique called a Tusi-couple, which generates linear motion from the sum of two circular motions. He used this technique to replace Ptolemy‘s problematic equant[10] for many planets, but was unable to find a solution to Mercury, which was solved later by Ibn al-Shatir as well as Ali Qushji.[11] The Tusi couple was later employed in Ibn al-Shatir‘s geocentric model and Nicolaus Copernicusheliocentric Copernican model.[12] He also calculated the value for the annual precession of the equinoxes and contributed to the construction and usage of some astronomical instruments including the astrolabe.
Ṭūsī criticized Ptolemy’s use of observational evidence to show that the Earth was at rest, noting that such proofs were not decisive. Although it doesn’t mean that he was a supporter of mobility of the earth, as he and his 16th-century commentator al-Bīrjandī, maintained that the earth’s immobility could be demonstrated, but only by physical principles found in natural philosophy.[13] Tusi’s criticisms of Ptolemy were similar to the arguments later used by Copernicus in 1543 to defend the Earth’s rotation.[14]
About the real essence of the Milky Way, Ṭūsī in his Tadhkira writes: “The Milky Way, i.e. the galaxy, is made up of a very large number of small, tightly-clustered stars, which, on account of their concentration and smallness, seem to be cloudy patches. because of this, it was likend to milk in color.” [15] Three centuries later the proof of the Milky Way consisting of many stars came in 1610 when Galileo Galilei used a telescope to study the Milky Way and discovered that it is really composed of a huge number of faint stars.[16]


In his Akhlaq-i-Nasri, Tusi put forward a basic theory for the evolution of species. He begins his theory of evolution with the universe once consisting of equal and similar elements. According to Tusi, internal contradictions began appearing, and as a result, some substances began developing faster and differently from other substances. He then explains how the elements evolved into minerals, then plants, then animals, and then humans. Tusi then goes on to explain how hereditary variability was an important factor for biological evolution of living things:[17]
“The organisms that can gain the new features faster are more variable. As a result, they gain advantages over other creatures. […] The bodies are changing as a result of the internal and external interactions.”
Tusi discusses how organisms are able to adapt to their environments:[17]
“Look at the world of animals and birds. They have all that is necessary for defense, protection and daily life, including strengths, courage and appropriate tools [organs] […] Some of these organs are real weapons, […] For example, horns-spear, teeth and claws-knife and needle, feet and hoofs-cudgel. The thorns and needles of some animals are similar to arrows. […] Animals that have no other means of defense (as the gazelle and fox) protect themselves with the help of flight and cunning. […] Some of them, for example, bees, ants and some bird species, have united in communities in order to protect themselves and help each other.”
Tusi recognized three types of living things: plants, animals, and humans. He wrote:[17]
“Animals are higher than plants, because they are able to move consciously, go after food, find and eat useful things. […] There are many differences between the animal and plant species, […] First of all, the animal kingdom is more complicated. Besides, reason is the most beneficial feature of animals. Owing to reason, they can learn new things and adopt new, non-inherent abilities. For example, the trained horse or hunting falcon is at a higher point of development in the animal world. The first steps of human perfection begin from here.”
Tusi then explains how humans evolved from advanced animals:[17]
“Such humans [probably anthropoid apes] live in the Western Sudan and other distant corners of the world. They are close to animals by their habits, deeds and behavior. […] The human has features that distinguish him from other creatures, but he has other features that unite him with the animal world, vegetable kingdom or even with the inanimate bodies. […] Before [the creation of humans], all differences between organisms were of the natural origin. The next step will be associated with spiritual perfection, will, observation and knowledge. […] All these facts prove that the human being is placed on the middle step of the evolutionary stairway. According to his inherent nature, the human is related to the lower beings, and only with the help of his will can he reach the higher development level.”

Chemistry and Physics

In chemistry and physics, Tusi stated a version of the law of conservation of mass. He wrote that a body of matter is able to change, but is not able to disappear:[17]
“A body of matter cannot disappear completely. It only changes its form, condition, composition, colour and other properties and turns into a different complex or elementary matter.”.[6]
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Ahmad ibn Muhammad ibn Kathīr al-Farghānī

Abū al-ʿAbbās Aḥmad ibn Muḥammad ibn Kathīr al-Farghānī. also known as Alfraganus in the West, was an Arab[1] or Persian[2][3] Sunni Muslim astronomer, and one of the most famous astronomers in 9th century. The crater Alfraganus on the Moon is named after him.


He was involved in the calculation of the diameter of the Earth by the measurement of the meridian arc length, together with a team of scientists under the patronage of al-Ma’mūn in Baghdad. Later he moved to Cairo, where he composed a treatise on the astrolabe around 856. There he also supervised the construction of the large Nilometer on the island of al-Rawda (in Old Cairo) in the year 861.


His textbook Kitāb fī Jawāmiʿ ʿIlm al-Nujūm (كتاب في جوامع علم النجوم A Compendium of the Science of the Stars) or Elements of astronomy on the celestial motions, written about 833, was a competent descriptive summary of Ptolemy’s Almagest, while using the findings and revised values of earlier Islamic astronomers.[4] It was translated into Latin in the 12th century and remained very popular in Europe until the time of Regiomontanus. Dante Alighieri‘s knowledge of Ptolemaic astronomy, which is evident in his Divina Commedia as well as other works such as the Convivio, seems to have been drawn from his reading of Alfraganus.[5][6] In the 17th century the Dutch orientalist Jacob Golius published the Arabic text on the basis of a manuscript he had acquired in the Near East, with a new Latin translation and extensive notes.


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