• Physician and Polymath Abu Ali al-Husayn ibn Abd Allah ibn Sina, 980
  

Abū ʿAlī al-Ḥusayn ibn ʿAbd Allāh ibn Sīnā (Persian پورسينا Pur-e Sina "son of Sina"; c. 980, Afshana near Bukhara – 1037, Hamadan, Iran), commonly known as Ibn Sīnā or by his Latinized name Avicenna, was a Persian polymath, who 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 encyclopaedia, and The Canon of Medicine, which was a standard medical text at many medieval universities. The Canon of Medicine was used as a textbook in the universities of Montpellier and Leuven as late as 1650. Ibn Sīnā's Canon of Medicine provides a complete system of medicine according to the principles of Galen (and Hippocrates).

His corpus also includes writing on philosophy, astronomy, alchemy, geology, psychology, Islamic theology, logic, mathematics, physics, as well as poetry. He is regarded as the most famous and influential polymath of the Islamic Golden Age.

Avicenna created an extensive corpus of works during what is commonly known as Islam's Golden Age, in which the translations of Greco - Roman, Persian, and Indian texts were studied extensively. Greco - Roman (Mid- and Neo - Platonic, and Aristotelian) texts by the Kindi school were commented, redacted and developed substantially by Islamic intellectuals, who also built upon Persian and Indian mathematical systems, astronomy, algebra, trigonometry and medicine. The Samanid dynasty in eastern part of Persia, Greater Khorasan and Central Asia as well as Buyid dynasty in the western part of Persia and Iraq provided a thriving atmosphere for scholarly and cultural development. Under the Samanids, Bukhara rivaled Baghdad as a cultural capital of the Islamic world.

The study of Quran and Hadith thrived in such a scholarly atmosphere. Philosophy, Fiqh and theology (kalam) were further developed, most noticeably by Avicenna and his opponents. Al-Razi and Al-Farabi had provided methodology and knowledge in medicine and philosophy. Avicenna had access to the great libraries of Balkh, Khwarezm, Gorgan, Rey, Isfahan and Hamadan. Various texts (such as the 'Ahd with Bahmanyar) show that he debated philosophical points with the greatest scholars of the time. Aruzi Samarqandi describes how before Avicenna left Khwarezm he had met Abu Rayhan Biruni (a famous scientist and astronomer), Abu Nasr Iraqi (a renowned mathematician), Abu Sahl Masihi (a respected philosopher) and Abu al-Khayr Khammar (a great physician).

The only source of information for the first part of Avicenna's life is his autobiography, as written down by his student Jūzjānī. In the absence of any other sources it is impossible to be certain how much of the autobiography is accurate. It has been noted that he uses his autobiography to advance his theory of knowledge (that it was possible for an individual to acquire knowledge and understand the Aristotelian philosophical sciences without a teacher), and it has been questioned whether the order of events described was adjusted to fit more closely with the Aristotelian model; in other words, whether Avicenna described himself as studying things in the 'correct' order. However given the absence of any other evidence, Avicenna's account essentially has to be taken at face value.

Avicenna was born c. 980 near Bukhara (in present day Uzbekistan), the capital of Samanids, a Persian dynasty in Central Asia and Greater Khorasan. His mother, named Setareh, was from Bukhara; his father, Abdullah, was a respected Ismaili scholar from Balkh, an important town of the Samanid Empire, in what is today Balkh Province, Afghanistan. His father was at the time of his son's birth the governor in one of the Samanid Nuh ibn Mansur's estates. He had his son very carefully educated at Bukhara. Ibn Sina's independent thought was served by an extraordinary intelligence and memory, which allowed him to overtake his teachers at the age of fourteen. As he said in his autobiography, there was nothing that he had not learned when he reached eighteen.

A number of different theories have been proposed regarding Avicenna's madhab. Medieval historian Ẓahīr al-dīn al-Bayhaqī (d. 1169) considered Avicenna to be a follower of the Brethren of Purity. On the other hands, Shia faqih Nurullah Shushtari and Seyyed Hossein Nasr, in addition to Henry Corbin, have maintained that he was most likely a Twelver Shia. More recently, however, Dimitri Gutas demonstrated that Avicenna was a Sunni Hanafi. Similar disagreements exist on the background of Avicenna's family, whereas some writers considered them Sunni, more recent writers thought they were Shia.

According to his autobiography, Avicenna had memorized the entire Qur'an by the age of 10. He learned Indian arithmetic from an Indian greengrocer, and he began to learn more from a wandering scholar who gained a livelihood by curing the sick and teaching the young. He also studied Fiqh (Islamic jurisprudence) under the Hanafi scholar Ismail al-Zahid.

As a teenager, he was greatly troubled by the Metaphysics of Aristotle, which he could not understand until he read al-Farabi's commentary on the work. For the next year and a half, he studied philosophy, in which he encountered greater obstacles. In such moments of baffled inquiry, he would leave his books, perform the requisite ablutions (wudu), then go to the mosque, and continue in prayer (salah) till light broke on his difficulties. Deep into the night, he would continue his studies, and even in his dreams problems would pursue him and work out their solution. Forty times, it is said, he read through the Metaphysics of Aristotle, till the words were imprinted on his memory; but their meaning was hopelessly obscure, until one day they found illumination, from the little commentary by Farabi, which he bought at a bookstall for the small sum of three dirhams. So great was his joy at the discovery, made with the help of a work from which he had expected only mystery, that he hastened to return thanks to God, and bestowed alms upon the poor.

He turned to medicine at 16, and not only learned medical theory, but also by gratuitous attendance of the sick had, according to his own account, discovered new methods of treatment. The teenager achieved full status as a qualified physician at age 18, and found that "Medicine is no hard and thorny science, like mathematics and metaphysics, so I soon made great progress; I became an excellent doctor and began to treat patients, using approved remedies." The youthful physician's fame spread quickly, and he treated many patients without asking for payment.

Ibn Sina's first appointment was that of physician to the emir, who owed him his recovery from a dangerous illness (997). Ibn Sina's chief reward for this service was access to the royal library of the Samanids, well known patrons of scholarship and scholars. When the library was destroyed by fire not long after, the enemies of Ibn Sina accused him of burning it, in order for ever to conceal the sources of his knowledge. Meanwhile, he assisted his father in his financial labors, but still found time to write some of his earliest works.

When Ibn Sina was 22 years old, he lost his father. The Samanid dynasty came to its end in December 1004. Ibn Sina seems to have declined the offers of Mahmud of Ghazni, and proceeded westwards to Urgench in the modern Turkmenistan, where the vizier, regarded as a friend of scholars, gave him a small monthly stipend. The pay was small, however, so Ibn Sina wandered from place to place through the districts of Nishapur and Merv to the borders of Khorasan, seeking an opening for his talents. Qabus, the generous ruler of Dailam and central Persia, himself a poet and a scholar, with whom Ibn Sina had expected to find an asylum, was about that date (1012) starved to death by his troops who had revolted. Ibn Sina himself was at this season stricken down by a severe illness. Finally, at Gorgan, near the Caspian Sea, Ibn Sina met with a friend, who bought a dwelling near his own house in which Ibn Sina lectured on logic and astronomy. Several of Ibn Sina's treatises were written for this patron; and the commencement of his Canon of Medicine also dates from his stay in Hyrcania.

Ibn Sina subsequently settled at Rai, in the vicinity of modern Tehran (present day capital of Iran), the home town of Rhazes; where Majd Addaula, a son of the last Buwayhid emir, was nominal ruler under the regency of his mother (Seyyedeh Khatun). About thirty of Ibn Sina's shorter works are said to have been composed in Rai. Constant feuds which raged between the regent and her second son, Shams al-Daula, however, compelled the scholar to quit the place. After a brief sojourn at Qazvin he passed southwards to Hamadãn where Shams al-Daula, another Buwayhid emir, had established himself. At first, Ibn Sina entered into the service of a high born lady; but the emir, hearing of his arrival, called him in as medical attendant, and sent him back with presents to his dwelling. Ibn Sina was even raised to the office of vizier. The emir consented that he should be banished from the country. Ibn Sina, however, remained hidden for forty days in a sheikh Ahmed Fadhel's house, until a fresh attack of illness induced the emir to restore him to his post. Even during this perturbed time, Ibn Sina persevered with his studies and teaching. Every evening, extracts from his great works, the Canon and the Sanatio, were dictated and explained to his pupils. On the death of the emir, Ibn Sina ceased to be vizier and hid himself in the house of an apothecary, where, with intense assiduity, he continued the composition of his works.

Meanwhile, he had written to Abu Ya'far, the prefect of the dynamic city of Isfahan, offering his services. The new emir of Hamadan, hearing of this correspondence and discovering where Ibn Sina was hidden, incarcerated him in a fortress. War meanwhile continued between the rulers of Isfahan and Hamadãn; in 1024 the former captured Hamadan and its towns, expelling the Tajik mercenaries. When the storm had passed, Ibn Sina returned with the emir to Hamadan, and carried on his literary labors. Later, however, accompanied by his brother, a favorite pupil, and two slaves, Ibn Sina escaped out of the city in the dress of a Sufi ascetic. After a perilous journey, they reached Isfahan, receiving an honorable welcome from the prince.

The remaining ten or twelve years of Ibn Sīnā's life were spent in the service of Abu Ja'far 'Ala Addaula, whom he accompanied as physician and general literary and scientific adviser, even in his numerous campaigns.

During these years he began to study literary matters and philology, instigated, it is asserted, by criticisms on his style. A severe colic, which seized him on the march of the army against Hamadan, was checked by remedies so violent that Ibn Sina could scarcely stand. On a similar occasion the disease returned; with difficulty he reached Hamadan, where, finding the disease gaining ground, he refused to keep up the regimen imposed, and resigned himself to his fate.

His friends advised him to slow down and take life moderately. He refused, however, stating that: "I prefer a short life with width to a narrow one with length". On his deathbed remorse seized him; he bestowed his goods on the poor, restored unjust gains, freed his slaves, and read through the Qur'an every three days until his death. He died in June 1037, in his fifty - eighth year, in the month of Ramadan and was buried in Hamadan, Iran.

Ibn Sīnā wrote extensively on early Islamic philosophy, especially the subjects logic, ethics, and metaphysics, including treatises named Logic and Metaphysics. Most of his works were written in Arabic - which was the de facto scientific language of the time in the Middle East, and some were written in the Persian language. Of linguistic significance even to this day are a few books that he wrote in nearly pure Persian language (particularly the Danishnamah-yi 'Ala', Philosophy for Ala' ad-Dawla'). Ibn Sīnā's commentaries on Aristotle often corrected the philosopher, encouraging a lively debate in the spirit of ijtihad.

In the medieval Islamic world, due to Avicenna's successful reconciliation between Aristotelianism and Neoplatonism along with Kalam, Avicennism eventually became the leading school of Islamic philosophy by the 12th century, with Avicenna becoming a central authority on philosophy.

Avicennism was also influential in medieval Europe, particular his doctrines on the nature of the soul and his existence - essence distinction, along with the debates and censure that they raised in scholastic Europe. This was particularly the case in Paris, where Avicennism was later proscribed in 1210. Nevertheless, his psychology and theory of knowledge influenced William of Auvergne, Bishop of Paris and Albertus Magnus, while his metaphysics had an impact on the thought of Thomas Aquinas.

Early Islamic philosophy and Islamic metaphysics, imbued as it is with Islamic theology, distinguishes more clearly than Aristotelianism the difference between essence and existence. Whereas existence is the domain of the contingent and the accidental, essence endures within a being beyond the accidental. The philosophy of Ibn Sīnā, particularly that part relating to metaphysics, owes much to al-Farabi. The search for a definitive Islamic philosophy separate from Occasionalism can be seen in what is left of his work.

Following al-Farabi's lead, Avicenna initiated a full fledged inquiry into the question of being, in which he distinguished between essence (Mahiat) and existence (Wujud). He argued that the fact of existence can not be inferred from or accounted for by the essence of existing things, and that form and matter by themselves cannot interact and originate the movement of the universe or the progressive actualization of existing things. Existence must, therefore, be due to an agent - cause that necessitates, imparts, gives, or adds existence to an essence. To do so, the cause must be an existing thing and coexist with its effect.

Avicenna’s consideration of the essence - attributes question may be elucidated in terms of his ontological analysis of the modalities of being; namely impossibility, contingency, and necessity. Avicenna argued that the impossible being is that which cannot exist, while the contingent in itself (mumkin bi-dhatihi) has the potentiality to be or not to be without entailing a contradiction. When actualized, the contingent becomes a ‘necessary existent due to what is other than itself’ (wajib al-wujud bi-ghayrihi). Thus, contingency - in - itself is potential beingness that could eventually be actualized by an external cause other than itself. The metaphysical structures of necessity and contingency are different. Necessary being due to itself (wajib al-wujud bi-dhatihi) is true in itself, while the contingent being is ‘false in itself’ and ‘true due to something else other than itself’. The necessary is the source of its own being without borrowed existence. It is what always exists. The Necessary exists ‘due - to - Its - Self’, and has no quiddity / essence (mahiyya) other than existence (wujud). Furthermore, It is ‘One’ (wahid ahad) since there cannot be more than one ‘Necessary-Existent - due - to - Itself’ without differentia (fasl) to distinguish them from each other. Yet, to require differentia entails that they exist ‘due - to - themselves’ as well as ‘due to what is other than themselves’; and this is contradictory. However, if no differentia distinguishes them from each other, then there is no sense in which these ‘Existents’ are not one and the same. Avicenna adds that the ‘Necessary - Existent - due - to - Itself’ has no genus (jins), nor a definition (hadd), nor a counterpart (nadd), nor an opposite (did), and is detached (bari’) from matter (madda), quality (kayf), quantity (kam), place (ayn), situation (wad’), and time (waqt).

Ibn Sina and Abū Rayhān al-Bīrūnī engaged in a written debate, with Abu Rayhan Biruni mostly criticizing Aristotelian natural philosophy and the Peripatetic school, while Avicenna and his student Ahmad ibn 'Ali al-Ma'sumi respond to Biruni's criticisms in writing. Abu Rayhan began by asking Avicenna eighteen questions, ten of which were criticisms of Aristotle's On the Heavens.

Ibn Sīnā was a devout Muslim and sought to reconcile rational philosophy with Islamic theology. His aim was to prove the existence of God and His creation of the world scientifically and through reason and logic. Avicenna wrote a number of treatises dealing with Islamic theology. These included treatises on the Islamic prophets, whom he viewed as "inspired philosophers", and on various scientific and philosophical interpretations of the Qur'an, such as how Quranic cosmology corresponds to his own philosophical system.

Ibn Sīnā memorized the Qur'an by the age of seven, and as an adult, he wrote five treatises commenting on suras from the Qur'an. One of these texts included the Proof of Prophecies, in which he comments on several Quranic verses and holds the Qur'an in high esteem. Avicenna argued that the Islamic prophets should be considered higher than philosophers.

While he was imprisoned in the castle of Fardajan near Hamadhan, Avicenna wrote his famous "Floating Man" thought experiment to demonstrate human self - awareness and the substantiality and immateriality of the soul. Avicenna believed his "Floating Man" thought experiment demonstrated that the soul is a substance, and claimed humans cannot doubt their own consciousness, even in a situation that prevents all sensory data input. The thought experiment told its readers to imagine themselves created all at once while suspended in the air, isolated from all sensations, which includes no sensory contact with even their own bodies. He argued that, in this scenario, one would still have self - consciousness. Because it is conceivable that a person, suspended in air while cut off from sense experience, would still be capable of determining his own existence, the thought experiment points to the conclusions that the soul is a perfection, independent of the body, and an immaterial substance. The conceivability of this “Floating Man” indicates that the soul is perceived intellectually, which entails the soul’s separateness from the body. Avicenna referred to the living human intelligence, particularly the active intellect, which he believed to be the hypostasis by which God communicates truth to the human mind and imparts order and intelligibility to nature. However, Avicenna posited the brain as the place where reason interacts with sensation. Sensation prepares the soul to receive rational concepts from the universal Agent Intellect. The first knowledge of the flying person would be “I am,” affirming his or her essence. That essence could not be the body, obviously, as the flying person has no sensation. Thus, the knowledge that “I am” is the core of a human being: the soul exists and is self - aware. Avicenna thus concluded that the idea of the self is not logically dependent on any physical thing, and that the soul should not be seen in relative terms, but as a primary given, a substance. The body is unnecessary; in relation to it, the soul is its perfection. In itself, the soul is an immaterial substance.

About 100 treatises were ascribed to Ibn Sina. Some of them are tracts of a few pages. Others are works extending through several volumes. His 14 volume The Canon of Medicine (Al-Qanoon fi al-Tibb, The Laws of Medicine) was a standard medical text in Europe and the Islamic world until the 18th century.

The book is known for its description of contagious diseases and sexually transmitted diseases, quarantine to limit the spread of infectious diseases, and testing of medicines. Ibn Sīnā adopted, from the Greeks, the theory that epidemics are caused by pollution in the air (miasma). It classifies and describes diseases, and outlines their assumed causes. Hygiene, simple and complex medicines, and functions of parts of the body are also covered. The Canon agrees with Aristotle (and disagrees with Hippocrates) that tuberculosis was contagious, a fact which was not universally accepted in Europe until centuries later. It also describes the symptoms and complications of diabetes. Both forms of facial paralysis were described in-depth.

The Canon of Medicine discussed how to effectively test new medicines:

• The drug must be free from any extraneous accidental quality.
• It must be used on a simple, not a composite, disease.
• The drug must be tested with two contrary types of diseases, because sometimes a drug cures one disease by Its essential qualities and another by its accidental ones.
• The quality of the drug must correspond to the strength of the disease. For example, there are some drugs whose heat is less than the coldness of certain diseases, so that they would have no effect on them.
• The time of action must be observed, so that essence and accident are not confused.
• The effect of the drug must be seen to occur constantly or in many cases, for if this did not happen, it was an accidental effect.
• The experimentation must be done with the human body, for testing a drug on a lion or a horse might not prove anything about its effect on man.

An Arabic edition of the Canon appeared at Rome in 1593, and a Hebrew version at Naples in 1491. Of the Latin version there were about thirty editions, founded on the original translation by Gerard de Sabloneta. In the 15th century a commentary on the text of the Canon was composed. Other medical works translated into Latin are the Medicamenta Cordialia, Canticum de Medicina, and the Tractatus de Syrupo Acetoso.

It was mainly accident which determined that from the 12th to the 18th century, Ibn Sīnā should be the guide of medical study in European universities, and eclipse the names of Rhazes, Ali ibn al-Abbas and Averroes. His work is not essentially different from that of his predecessor Rhazes, because he presented the doctrine of Galen, and through Galen the doctrine of Hippocrates, modified by the system of Aristotle. But the Canon of Ibn Sīnā is distinguished from the Al-Hawi (Continence) or Summary of Rhazes by its greater method, due perhaps to the logical studies of the former.

The work has been variously appreciated in subsequent ages, some regarding it as a treasury of wisdom, and others, like Averroes, holding it useful only as waste paper. In modern times it has been mainly of historic interest as most of its tenets have been disproved or expanded upon by scientific medicine. The vice of the book is excessive classification of bodily faculties, and over - subtlety in the discrimination of diseases. It includes five books; of which the first and second discuss physiology, pathology and hygiene, the third and fourth deal with the methods of treating disease, and the fifth describes the composition and preparation of remedies. This last part contains some personal observations.

He is ample in the enumeration of symptoms, and is said to be inferior in practical medicine and surgery. He introduced into medical theory the four causes of the Peripatetic system. Of natural history and botany he pretended to no special knowledge. Up to the year 1650, or thereabouts, the Canon was still used as a textbook in the universities of Leuven and Montpellier.

In the museum at Bukhara, there are displays showing many of his writings, surgical instruments from the period and paintings of patients undergoing treatment. Ibn Sīnā was interested in the effect of the mind on the body, and wrote a great deal on psychology, likely influencing Ibn Tufayl and Ibn Bajjah. He also introduced medical herbs.

Avicenna extended the theory of temperaments in The Canon of Medicine to encompass "emotional aspects, mental capacity, moral attitudes, self - awareness, movements and dreams." 

In The Canon of Medicine, Avicenna described a number of conditions, including melancholia. He described melancholia as a depressive type of mood disorder in which the person may become suspicious and develop certain types of phobias.

Though the threads which comprise Unani healing can be traced all the way back to Galen of Pergamon, who lived in the 2nd century AD, the basic knowledge of Unani medicine as a healing system was developed by Hakim Ibn Sina in his medical encyclopedia The Canon of Medicine. The time of origin is thus dated at circa 1025 AD, when Avicenna wrote The Canon of Medicine in Persia, which remains a text book in the syllabus of Unani medicine in the colleges of India and Pakistan.

Ibn Sīnā wrote on Earth sciences such as geology in The Book of Healing. While discussing the formation of mountains, he explained:

Either they are the effects of upheavals of the crust of the earth, such as might occur during a violent earthquake, or they are the effect of water, which, cutting itself a new route, has denuded the valleys, the strata being of different kinds, some soft, some hard... It would require a long period of time for all such changes to be accomplished, during which the mountains themselves might be somewhat diminished in size.

In mechanics, Ibn Sīnā, in The Book of Healing, developed an elaborate theory of motion, in which he made a distinction between the inclination (tendency to motion) and force of a projectile, and concluded that motion was a result of an inclination (mayl) transferred to the projectile by the thrower, and that projectile motion in a vacuum would not cease. He viewed inclination as a permanent force whose effect is dissipated by external forces such as air resistance.

The theory of motion developed by Avicenna may have influenced Jean Buridan's theory of impetus (the ancestor of the inertia and momentum concepts).

In optics, Ibn Sina was among those who argued that light had a speed, observing that "if the perception of light is due to the emission of some sort of particles by a luminous source, the speed of light must be finite.". He also provided a wrong explanation of the rainbow phenomenon. Carl Benjamin Boyer described Avicenna's ("Ibn Sīnā") theory on the rainbow as follows:

Independent observation had demonstrated to him that the bow is not formed in the dark cloud but rather in the very thin mist lying between the cloud and the sun or observer. The cloud, he thought, serves simply as the background of this thin substance, much as a quicksilver lining is placed upon the rear surface of the glass in a mirror. Ibn Sīnā would change the place not only of the bow, but also of the color formation, holding the iridescence to be merely a subjective sensation in the eye.

In 1253, a Latin text entitled Speculum Tripartitum stated the following regarding Avicenna's theory on heat:

Avicenna says in his book of heaven and earth, that heat is generated from motion in external things.

Avicenna's legacy in classical psychology is primarily embodied in the Kitab al-nafs parts of his Kitab al-shifa' (The Book of Healing) and Kitab al-najat (The Book of Deliverance). These were known in Latin under the title De Anima (treatises "on the soul"). The main thesis of these tracts is represented in his so-called "flying man" argument, which resonates with what was centuries later entailed by Descartes's cogito argument (or what phenomenology designates as a form of an "epoche").

Avicenna’s psychology requires that connection between the body and soul be strong enough to ensure the soul’s individuation, but weak enough to allow for its immortality. Avicenna grounds his psychology on physiology, which means his account of the soul is one that deals almost entirely with the natural science of the body and its abilities of perception. Thus, the philosopher's connection between the soul and body is explained almost entirely by his understanding of perception; in this way, bodily perception interrelates with the immaterial human intellect. In sense perception, the perceiver senses the form of the object; first, by perceiving features of the object by our external senses. This sensory information is supplied to the internal senses, which merge all the pieces into a whole, unified conscious experience. This process of perception and abstraction is the nexus of the soul and body, for the material body may only perceive material objects, while the immaterial soul may only receive the immaterial, universal forms. The way the soul and body interact in the final abstraction of the universal from the concrete particular is the key to their relationship and interaction, which takes place in the physical body.

The soul completes the action of intellection by accepting forms that have been abstracted from matter. This process requires a concrete particular (material) to be abstracted into the universal intelligible (immaterial). The material and immaterial interact through the Active Intellect, which is a “divine light” containing the intelligible forms. The Active Intellect reveals the universals concealed in material objects much like the sun makes color available to our eyes.

The practice of judicial astrology was refuted by Avicenna. His reasons were due to the methods used by astrologers in judicial astrology being conjectural rather than empirical and also due to the principles of this type of astrology conflicting with orthodox Islam. He also cited passages from the Qur'an in order to justify his refutation of astrology on both scientific and religious grounds. However, Avicenna’s refutation of astrology (in the treatise titled Resāla fī ebṭāl aḥkām al-nojūm) concerned only the judicial application of astrology rather than the philosophical principles of the subject and its natural influence. He stated that it was true that each planet had some influence on the earth, but his argument was the difficulty of astrologers being able to determine the exact effect of it. In essence, Avicenna did not refute astrology, but denied man’s limited capacity to be able to know the precise effects of the stars on the sublunar matter. With that, he did not refute the essential dogma of astrology, but only refuted our ability to fully understand it.

In astronomy, he criticized Aristotle's view of the stars receiving their light from the Sun. Ibn Sīnā stated that the stars are self luminous, and believed that the planets are also self luminous. He claimed to have observed the transit of Venus across the Sunon May 24, 1032. However, modern scholars have questioned whether he could have observed the transit from his location at that time. He used his transit observation to demonstrate that Venus was, at least sometimes, below the Sun in the Ptolemaic cosmology.

Soon after, he wrote the Compendium of the Almagest, a commentary on Ptolemy's Almagest. Avicenna concluded that Venus is closer to the Earth than the Sun. In 1070, Abu Ubayd al-Juzjani, a pupil of Ibn Sīnā, claimed that his teacher Ibn Sīnā had solved the equant problem in the Ptolemaic model.

Ibn Sīnā used distillation to produce essential oils such as rose essence, forming the foundation of what later became aroma therapy. Four of his works on alchemy were translated into Latin as:

• Liber Aboali Abincine de Anima in arte Alchemiae
• Declaratio Lapis physici Avicennae filio sui Aboali
• Avicennae de congelatione et conglutinatione lapidum
• Avicennae ad Hasan Regem epistola de Re recta

In one of these works, Ibn Sīnā discredited the theory of the transmutation of substances commonly believed by alchemists:

Those of the chemical craft know well that no change can be effected in the different species of substances, though they can produce the appearance of such change.

Among his works on alchemy, Liber Aboali Abincine de Anima in arte Alchemiae was the most influential, having influenced later medieval chemists and alchemists such as Vincent of Beauvais.

In another work, translated into Latin as De congelatione et conglutinatione lapidum, Ibn Sina proposed a four - part classification of inorganic bodies, which was a significant improvement over the two - part classification of Aristotle (into orycta and metals) and three - part classification of Galen (into terrae, lapides and metals). The four parts of Ibn Sina's classification were: lapides, sulfur, salts and metals.

Almost half of Ibn Sīnā's works are versified. His poems appear in both Arabic and Persian. As an example, Edward Granville Browne claims that the following Persian verses are incorrectly attributed to Omar Khayyám, and were originally written by Ibn Sīnā:

As early as the 14th century when Dante Alighieri depicted him in Limbo alongside the virtuous non - Christian thinkers in his Divine Comedy such as Virgil, Averroes, Homer, Horace, Ovid, Lucan, Socrates, Plato, and Saladin, Avicenna has been recognized by both East and West, as one of the great figures in intellectual history.

George Sarton, the author of The History of Science, described Ibn Sīnā as "one of the greatest thinkers and medical scholars in history" and called him "the most famous scientist of Islam and one of the most famous of all races, places, and times." He was one of the Islamic world's leading writers in the field of medicine, and similarly to earlier Islamic writers he followed the approach of Galen (and Hippocrates as transmitted through Galen). Along with Rhazes, Abulcasis, Ibn al-Nafis, and al-Ibadi, Ibn Sīnā is considered an important compiler of early Muslim medicine. He is remembered in Western history of medicine as a major historical figure who made important contributions to medicine and the European Renaissance. His medical texts were unusual in that where controversy existed between Galen and Aristotle's views on medical matters (such as anatomy), he preferred to side with Aristotle, where necessary updating Aristotle's position to take into account post - Aristotle advances in anatomical knowledge. Aristotle's dominant intellectual influence among medieval European scholars meant that Avicenna's linking of Galen's medical writings with Aristotle's philosophical writings in the Canon of Medicine (along with its comprehensive and logical organisation of knowledge) significantly increased Avicenna's importance in medieval Europe in comparison to other Islamic writers on medicine. His influence following translation of the Canon was such that from the early fourteenth to the mid - sixteenth centuries he was ranked with Hippocrates and Galen as one of the acknowledged authorities, princeps medicorum (prince of physicians).

In Iran, he is considered a national icon, and is often regarded as one of the greatest Persians to have ever lived. Many portraits and statues remain in Iran today. An impressive monument to the life and works of the man who is known as the 'doctor of doctors' still stands outside the Bukhara museum and his portrait hangs in the Hall of the Avicenna Faculty of Medicine in the University of Paris. There is also a crater on the Moon named Avicenna and a plant genus Avicennia. Bu-Ali Sina University in Hamadan (Iran), the ibn Sīnā Tajik State Medical University in Dushanbe (The capital of the Republic of Tajikistan), Ibn Sina Academy of Medieval Medicine and Sciences at Aligarh, India, Avicenna School in Karachi and Avicenna Medical College in Lahore, Pakistan, Ibne Sina Balkh Medical School in his native province of Balkh in Afghanistan, Ibni Sina Faculty Of Medicine of Ankara University, Ankara, Turkey, and Ibn Sina Integrated School in Marawi City (Philippines) are all named in his honor. In 1980, the former Soviet Union, which then ruled his birthplace Bukhara, celebrated the thousandth anniversary of Avicenna's birth by circulating various commemorative stamps with artistic illustrations, and by erecting a bust of Avicenna based on anthropological research by Soviet scholars. Near his birthplace in Qishlak Afshona, some 25 km (16 mi). north of Bukhara, a training college for medical staff has been named for him. On the grounds is a museum dedicated to his life, times and work.

In March 2008, it was announced that Avicenna’s name would be used for new Directories of education institutions for health care professionals, worldwide. The Avicenna Directories will list universities and schools where doctors, public health practitioners, pharmacists and others, are educated. The project team stated “Why Avicenna? Avicenna ... was ... noted for his synthesis of knowledge from both east and west. He has had a lasting influence on the development of medicine and health sciences. The use of Avicenna’s name symbolises the worldwide partnership that is needed for the promotion of health services of high quality.”

The treatises of Ibn Sīnā influenced later Muslim thinkers in many areas including theology, philology, mathematics, astronomy, physics, and music. Ibn Sīnā's works numbered almost 450 volumes on a wide range of subjects, of which around 240 have survived. In particular, 150 volumes of his surviving works concentrate on philosophy and 40 of them concentrate on medicine. His most famous works are The Book of Healing, a vast philosophical and scientific encyclopaedia, and The Canon of Medicine.

Ibn Sīnā wrote at least one treatise on alchemy, but several others have been falsely attributed to him. His book on animals was translated by Michael Scot. His Logic, Metaphysics, Physics, and De Caelo, are treatises giving a synoptic view of Aristotelian doctrine, though the Metaphysics demonstrates a significant departure from the brand of Neoplatonism known as Aristotelianism in Ibn Sīnā's world; Arabic philosophers have hinted at the idea that Ibn Sīnā was attempting to "re-Aristotelianise" Muslim philosophy in its entirety, unlike his predecessors, who accepted the conflation of Platonic, Aristotelian, Neo- and Middle - Platonic works transmitted into the Muslim world.

The Logic and Metaphysics have been extensively reprinted, the latter, e.g., at Venice in 1493, 1495, and 1546. Some of his shorter essays on medicine, logic, etc., take a poetical form (the poem on logic was published by Schmoelders in 1836). Two encyclopaedic treatises, dealing with philosophy, are often mentioned. The larger, Al-Shifa' (Sanatio), exists nearly complete in manuscript in the Bodleian Library and elsewhere; part of it on the De Anima appeared at Pavia (1490) as the Liber Sextus Naturalium, and the long account of Ibn Sina's philosophy given by Muhammad al-Shahrastani seems to be mainly an analysis, and in many places a reproduction, of the Al-Shifa'. A shorter form of the work is known as the An-najat (Liberatio). The Latin editions of part of these works have been modified by the corrections which the monastic editors confess that they applied. There is also a حكمت مشرقيه (hikmat-al-mashriqqiyya, in Latin Philosophia Orientalis), mentioned by Roger Bacon, the majority of which is lost in antiquity, which according to Averroes was pantheistic in tone.