Ibn sina scientist biography project

Avicenna

Persian polymath, physician and philosopher (c. 980–1037)

For the crater, see Avicenna (crater).

"Ibn Sīnā" redirects here. Not to be confused with Ali Sina or Ibn Sina Peak.

Ibn Sina (Persian: ابن سینا, romanized: Ibn Sīnā; c. 980 – 22 June 1037), commonly known in the West as Avicenna (), was a preeminent philosopher and physician of the Muslim world,^[4]^[5] flourishing during the Islamic Golden Age, serving in the courts of various Iranian rulers.^[6] He is often described as the father of early modern medicine.^[7]^[8]^[9] His philosophy was of the Peripatetic school derived from Aristotelianism.^[10]

His most famous works are The Book of Healing, a philosophical and scientific encyclopedia, and The Canon of Medicine, a medical encyclopedia^[11]^[12]^[13] which became a standard medical text at many medieval European universities^[14] and remained in use as late as 1650.^[15] Besides philosophy and medicine, Avicenna's corpus includes writings on astronomy, alchemy, geography and geology, psychology, Islamic theology, logic, mathematics, physics, and works of poetry.^[16]

Avicenna wrote most of his philosophical and scientific works in Arabic, but also wrote several key works in Persian, while his poetic works were written in both languages. Of the 450 works he is believed to have written, around 240 have survived, including 150 on philosophy and 40 on medicine.^[10]

Name

Avicenna is a Latin corruption of the Arabic patronymIbn Sīnā (ابن سينا),^[17] meaning "Son of Sina". However, Avicenna was not the son but the great-great-grandson of a man named Sina.^[18] His formal Arabic name was Abū ʿAlī al-Ḥusayn bin ʿAbdullāh ibn al-Ḥasan bin ʿAlī bin Sīnā al-Balkhi al-Bukhari (أبو علي الحسين بن عبد الله بن الحسن بن علي بن سينا البلخي البخاري).^[19]^[20]

Circumstances

Avicenna created an extensive corpus of works during what is commonly known as the Islamic Golden Age, in which the translations of Byzantine, Greco-Roman, Persian, and Indian texts were studied extensively. Greco-Roman (Middle Platonic, Neoplatonic, and Aristotelian) texts translated 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.^[21]

The Samanid Empire in the eastern part of Persia, Greater Khorasan, and Central Asia, as well as the 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 for cultural capital of the Muslim world.^[22] There, Avicenna had access to the great libraries of Balkh, Khwarazm, Gorgan, Rey, Isfahan and Hamadan.

Various texts (such as the 'Ahd with Bahmanyar) show that Avicenna debated philosophical points with the greatest scholars of the time. Nizami Aruzi described how before ibn Sina left Khwarazm, he had met al-Biruni (a scientist and astronomer), Abu Nasr Mansur (a renowned mathematician), Abu Sahl 'Isa ibn Yahya al-Masihi (a respected philosopher) and ibn al-Khammar (a great physician). The study of the Quran and the Hadith also thrived, and Islamic philosophy, fiqh "jurisprudence", and kalam "speculative theology" were all further developed by ibn Sina and his opponents at this time.

Biography

Early life and education

Avicenna was born in c. 980 in the village of Afshana in Transoxiana to a Persian family.^[23] The village was near the Samanid capital of Bukhara, which was his mother's hometown. His father Abd Allah was a native of the city of Balkh in Bactria. An official of the Samanid bureaucracy, he had served as the governor of a village of the royal estate of Harmaytan near Bukhara during the reign of Nuh II (r. 976–997). Avicenna also had a younger brother. A few years later, the family settled in Bukhara, a center of learning, which attracted many scholars. It was there that Avicenna was educated, which early on was seemingly administered by his father.

Although both Avicenna's father and brother had converted to Isma'ilism, he himself did not follow the faith. He was instead a Hanafi Sunni, the same school followed by the Samanids.

Avicenna was first schooled in the Quran and literature, and by the age of 10, he had memorized the entire Quran. He was later sent by his father to an Indian greengrocer, who taught him arithmetic. Afterwards, he was schooled in fiqh by the Hanafi jurist Ismail al-Zahid. Sometime later, his father invited the physician and philosopher al-Natili to their house to educate ibn Sina. Together, they studied the Isagoge of Porphyry (died 305) and possibly the Categories of Aristotle (died 322 BCE) as well. After Avicenna had read the Almagest of Ptolemy (died 170) and Euclid's Elements, al-Natili told him to continue his research independently. By the time Avicenna was eighteen, he was well-educated in Greek sciences. Although ibn Sina only mentions al-Natili as his teacher in his autobiography, he most likely had other teachers as well, such as the physicians Qumri and Abu Sahl 'Isa ibn Yahya al-Masihi.

Career

In Bukhara and Gurganj

At the age of seventeen, Avicenna was made a physician of Nuh II. By the time Avicenna was at least 21 years old, his father died. He was subsequently given an administrative post, possibly succeeding his father as the governor of Harmaytan. Avicenna later moved to Gurganj, the capital of Khwarazm, which he reports that he did due to "necessity". The date he went to the place is uncertain, as he reports that he served the Khwarazmshah, the ruler of Khwarazm, the Ma'munid ruler Abu al-Hasan Ali. The latter ruled from 997 to 1009, which indicates that Avicenna moved sometime during that period.

He may have moved in 999, the year in which the Samanid Empire fell after the Kara-Khanid Khanate captured Bukhara and imprisoned the Samanid emir Abd al-Malik II. Due to his high position and strong connection with the Samanids, ibn Sina may have found himself in an unfavorable position after the fall of his suzerain.

It was through the minister of Gurganj, Abu'l-Husayn as-Sahi, a patron of Greek sciences, that Avicenna entered into the service of Abu al-Hasan Ali. Under the Ma'munids, Gurganj became a centre of learning, attracting many prominent figures, such as ibn Sina and his former teacher Abu Sahl al-Masihi, the mathematician Abu Nasr Mansur, the physician ibn al-Khammar, and the philologistal-Tha'alibi.

In Gorgan

Avicenna later moved due to "necessity" once more (in 1012), this time to the west. There he travelled through the Khurasani cities of Nasa, Abivard, Tus, Samangan and Jajarm. He was planning to visit the ruler of the city of Gorgan, the ZiyaridQabus (r. 977–981, 997–1012), a cultivated patron of writing, whose court attracted many distinguished poets and scholars. However, when Avicenna eventually arrived, he discovered that the ruler had been dead since the winter of 1013. Avicenna then left Gorgan for Dihistan, but returned after becoming ill. There he met Abu 'Ubayd al-Juzjani (died 1070) who became his pupil and companion. Avicenna stayed briefly in Gorgan, reportedly serving Qabus's son and successor Manuchihr (r. 1012–1031) and resided in the house of a patron.

In Ray and Hamadan

In c. 1014, Avicenna went to the city of Ray, where he entered into the service of the Buyid amirMajd al-Dawla (r. 997–1029) and his mother Sayyida Shirin, the de facto ruler of the realm. There he served as the physician at the court, treating Majd al-Dawla, who was suffering from melancholia. Avicenna reportedly later served as the "business manager" of Sayyida Shirin in Qazvin and Hamadan, though details regarding this tenure are unclear. During this period, Avicenna finished writing The Canon of Medicine and started writing his The Book of Healing.

In 1015, during Avicenna's stay in Hamadan, he participated in a public debate, as was customary for newly arrived scholars in western Iran at that time. The purpose of the debate was to examine one's reputation against a prominent resident. The person whom Avicenna debated against was Abu'l-Qasim al-Kirmani, a member of the school of philosophers of Baghdad. The debate became heated, resulting in ibn Sina accusing Abu'l-Qasim of lack of basic knowledge in logic, while Abu'l-Qasim accused ibn Sina of impoliteness.

After the debate, Avicenna sent a letter to the Baghdad Peripatetics, asking if Abu'l-Qasim's claim that he shared the same opinion as them was true. Abu'l-Qasim later retaliated by writing a letter to an unknown person in which he made accusations so serious that ibn Sina wrote to Abu Sa'd, the deputy of Majd al-Dawla, to investigate the matter. The accusation made towards Avicenna may have been the same as he had received earlier, in which he was accused by the people of Hamadan of copying the stylistic structures of the Quran in his Sermons on Divine Unity. The seriousness of this charge, in the words of the historian Peter Adamson, "cannot be underestimated in the larger Muslim culture".

Not long afterwards, Avicenna shifted his allegiance to the rising Buyid amir Shams al-Dawla, the younger brother of Majd al-Dawla, which Adamson suggests was due to Abu'l-Qasim also working under Sayyida Shirin. Avicenna had been called upon by Shams al-Dawla to treat him, but after the latter's campaign in the same year against his former ally, the Annazid ruler Abu Shawk (r. 1010–1046), he forced Avicenna to become his vizier.

Although Avicenna would sometimes clash with Shams al-Dawla's troops, he remained vizier until the latter died of colic in 1021. Avicenna was asked to stay as vizier by Shams al-Dawla's son and successor Sama' al-Dawla (r. 1021–1023), but he instead went into hiding with his patron, Abu Ghalib al-Attar, to wait for better opportunities to emerge. It was during this period that Avicenna was secretly in contact with Ala al-Dawla Muhammad (r. 1008–1041), the Kakuyid ruler of Isfahan and uncle of Sayyida Shirin.

It was during his stay at Attar's home that Avicenna completed The Book of Healing, writing 50 pages a day. The Buyid court in Hamadan, particularly the Kurdish vizier Taj al-Mulk, suspected Avicenna of correspondence with Ala al-Dawla, and as a result, had the house of Attar ransacked and ibn Sina imprisoned in the fortress of Fardajan, outside Hamadan. Juzjani blames one of ibn Sina's informers for his capture. He was imprisoned for four months until Ala al-Dawla captured Hamadan, ending Sama al-Dawla's reign.

In Isfahan

Avicenna was subsequently released, and went to Isfahan, where he was well received by Ala al-Dawla. In the words of Juzjani, the Kakuyid ruler gave Avicenna "the respect and esteem which someone like him deserved". Adamson also says that Avicenna's service under Ala al-Dawla "proved to be the most stable period of his life". Avicenna served as the advisor, if not vizier of Ala al-Dawla, accompanying him in many of his military expeditions and travels. Avicenna dedicated two Persian works to him, a philosophical treatise named Danish-nama-yi Ala'i ("Book of Science for Ala"), and a medical treatise about the pulse.

During the brief occupation of Isfahan by the Ghaznavids in January 1030, Avicenna and Ala al-Dawla relocated to the southwestern Iranian region of Khuzistan, where they stayed until the death of the Ghaznavid ruler Mahmud (r. 998–1030), which occurred two months later. It was seemingly when Avicenna returned to Isfahan that he started writing his Pointers and Reminders. In 1037, while Avicenna was accompanying Ala al-Dawla to a battle near Isfahan, he contracted a severe colic, having suffered from colic throughout his life. He died shortly afterwards in Hamadan, where he was buried.

Philosophy

Avicenna 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, then the language of science in the Muslim world, and some in Early New Persian. Of linguistic significance even to this day are a few books that he wrote in Persian, particularly the Danishnama. Avicenna's commentaries on Aristotle often criticized the philosopher,^[54] encouraging a lively debate in the spirit of ijtihad.

Avicenna's Neoplatonic scheme of emanations became fundamental in kalam in the 12th century.^[55]

The Book of Healing became available in Europe in a partial Latin translation some fifty years after its composition under the title Sufficientia, and some authors have identified a "Latin Avicennism" as flourishing for some time paralleling the more influential Latin Averroism, but it was suppressed by the Parisian decrees of 1210 and 1215.^[56]

Avicenna's psychology and theory of knowledge influenced the theologian William of Auvergne^[57] and Albertus Magnus,^[57] while his metaphysics influenced the thought of Thomas Aquinas.^[57]

Metaphysical doctrine

Early Islamic philosophy and Islamic metaphysics, imbued as it is with kalam, distinguishes between essence and existence more clearly than Aristotelianism. Whereas existence is the domain of the contingent and the accidental, essence endures within a being beyond the accidental. The philosophy of Avicenna, 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 (Arabic: ماهية, romanized: māhiya) and existence (Arabic: وجود, romanized: wujūd). He argued that the fact of existence cannot 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.^[58]

Impossibility, contingency, necessity

See also: Necessity and sufficiency, Contingency (philosophy), Metaphysical necessity, and Potentiality and actuality

Further information: Modal logic

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.^[59]^[60]

Differentia

Reception

Avicenna's theology on metaphysical issues (ilāhiyyāt) has been criticized by some Islamic scholars, among them al-Ghazali, ibn Taymiyya, and ibn Qayyim al-Jawziyya.^[66]^{[page needed]} While discussing the views of the theists among the Greek philosophers, namely Socrates, Plato and Aristotle in Al-Munqidh min ad-Dalal "Deliverance from Error", al-Ghazali noted:

[the Greek philosophers] must be taxed with unbelief, as must their partisans among the Muslim philosophers, such as Avicenna and al-Farabi and their likes. None, however, of the Muslim philosophers engaged so much in transmitting Aristotle's lore as did the two men just mentioned. [...] The sum of what we regard as the authentic philosophy of Aristotle, as transmitted by al-Farabi and Avicenna, can be reduced to three parts: a part which must be branded as unbelief; a part which must be stigmatized as innovation; and a part which need not be repudiated at all.^[67]

Argument for God's existence

Main article: Proof of the Truthful

Avicenna made an argument for the existence of God which would be known as the "Proof of the Truthful" (wajib al-wujud). Avicenna argued that there must be a Proof of the Truthful, an entity that cannot not exist and through a series of arguments, he identified it with God in Islam. Present-day historian of philosophyPeter Adamson called this argument one of the most influential medieval arguments for God's existence, and Avicenna's biggest contribution to the history of philosophy.

Al-Biruni correspondence

Correspondence between ibn Sina with his student Ahmad ibn ʿAli al-Maʿsumi and al-Biruni has survived in which they debated Aristotelian natural philosophy and the Peripatetic school. al-Biruni began by asking eighteen questions, ten of which were criticisms of Aristotle's On the Heavens.^[70]

Theology

Ibn Sina was a devout Muslim and sought to reconcile rational philosophy with Islamic theology. He aimed to prove the existence of God and His creation of the world scientifically and through reason and logic.^[71] His views on Islamic theology and philosophy were enormously influential, forming part of the core of the curriculum at Islamic religious schools until the 19th century.^[72]

Avicenna wrote several short treatises dealing with Islamic theology. These included treatises on the prophets and messengers in Islam, whom he viewed as "inspired philosophers", and also on various scientific and philosophical interpretations of the Quran, such as how Quranic cosmology corresponds to his philosophical system. In general, these treatises linked his philosophical writings to Islamic religious ideas; for example, the body's afterlife.

There are occasional brief hints and allusions in his longer works, however, that Avicenna considered philosophy as the only sensible way to distinguish real prophecy from illusion. He did not state this more clearly because of the political implications of such a theory if prophecy could be questioned, and also because most of the time he was writing shorter works which concentrated on explaining his theories on philosophy and theology clearly, without digressing to consider epistemological matters which could only be properly considered by other philosophers.^[73]

Later interpretations of Avicenna's philosophy split into three different schools; those (such as al-Tusi) who continued to apply his philosophy as a system to interpret later political events and scientific advances; those (such as al-Razi) who considered Avicenna's theological works in isolation from his wider philosophical concerns; and those (such as al-Ghazali) who selectively used parts of his philosophy to support their own attempts to gain greater spiritual insights through a variety of mystical means. It was the theological interpretation championed by those such as al-Razi which eventually came to predominate in the madrasahs.^[74]

Avicenna memorized the Quran by the age of ten, and as an adult, wrote five treatises commenting on surahs of the Quran. One of these texts included the Proof of Prophecies, in which he comments on several Quranic verses and holds the Quran in high esteem. Avicenna argued that the Islamic prophets should be considered higher than philosophers.^[75]

Avicenna is generally understood to have been aligned with the Hanafi school of Sunni thought.^[76]^[77] Avicenna studied Hanafi law, many of his notable teachers were Hanafi jurists, and he served under the Hanafi court of Ali ibn Mamun.^[78]^[76] Avicenna said at an early age that he remained "unconvinced" by Ismaili missionary attempts to convert him.^[76]

Medieval historian Ẓahīr al-dīn al-Bayhaqī (d. 1169) believed Avicenna to be a follower of the Brethren of Purity.^[77]

Thought experiments

Main article: Floating man

While he was imprisoned in the castle of Fardajan near Hamadhan, Avicenna wrote his famous "floating man"—literally falling man—a 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.^[79] 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. Following is an English translation of the argument:

One of us (i.e. a human being) should be imagined as having been created in a single stroke; created perfect and complete but with his vision obscured so that he cannot perceive external entities; created falling through air or a void, in such a manner that he is not struck by the firmness of the air in any way that compels him to feel it, and with his limbs separated so that they do not come in contact with or touch each other. Then contemplate the following: can he be assured of the existence of himself? He does not have any doubt in that his self exists, without thereby asserting that he has any exterior limbs, nor any internal organs, neither heart nor brain, nor any one of the exterior things at all; but rather he can affirm the existence of himself, without thereby asserting there that this self has any extension in space. Even if it were possible for him in that state to imagine a hand or any other limb, he would not imagine it as being a part of his self, nor as a condition for the existence of that self; for as you know that which is asserted is different from that which is not asserted and that which is inferred is different from that which is not inferred. Therefore the self, the existence of which has been asserted, is a unique characteristic, in as much that it is not as such the same as the body or the limbs, which have not been ascertained. Thus that which is ascertained (i.e. the self), does have a way of being sure of the existence of the soul as something other than the body, even something non-bodily; this he knows, this he should understand intuitively, if it is that he is ignorant of it and needs to be beaten with a stick [to realize it].
— Ibn Sina, Kitab Al-Shifa, On the Soul^[62]^[80]

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.^[81] 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.^[82]^[83]^[84] In itself, the soul is an immaterial substance.^[85]

Principal works

The Canon of Medicine

Main article: The Canon of Medicine

Avicenna authored a five-volume medical encyclopedia, The Canon of Medicine (Arabic: القانون في الطب, romanized: al-Qānūn fī l-ṭibb). It was used as the standard medical textbook in the Islamic world and Europe up to the 18th century.^[86]^[87] The Canon still plays an important role in Unani medicine.^[88]

Liber Primus Naturalium

Avicenna considered whether events like rare diseases or disorders have natural causes.^[89] He used the example of polydactyly to explain his perception that causal reasons exist for all medical events. This view of medical phenomena anticipated developments in the Enlightenment by seven centuries.^[90]

The Book of Healing

Main article: The Book of Healing

Earth sciences

Avicenna wrote on Earth sciences such as geology in The Book of Healing.^[91] 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.^[91]

Philosophy of science

In the Al-Burhan (On Demonstration) section of The Book of Healing, Avicenna discussed the philosophy of science and described an early scientific method of inquiry. He discussed Aristotle's Posterior Analytics and significantly diverged from it on several points. Avicenna discussed the issue of a proper methodology for scientific inquiry and the question of "How does one acquire the first principles of a science?" He asked how a scientist would arrive at "the initial axioms or hypotheses of a deductive science without inferring them from some more basic premises?" He explained that the ideal situation is when one grasps that a "relation holds between the terms, which would allow for absolute, universal certainty". Avicenna then added two further methods for arriving at the first principles: the ancient Aristotelian method of induction (istiqra), and the method of examination and experimentation (tajriba). Avicenna criticized Aristotelian induction, arguing that "it does not lead to the absolute, universal, and certain premises that it purports to provide." In its place, he developed a "method of experimentation as a means for scientific inquiry."^[92]

Logic

An early formal system of temporal logic was studied by Avicenna.^[93] Although he did not develop a real theory of temporal propositions, he did study the relationship between temporalis and the implication.^[94] Avicenna's work was further developed by Najm al-Dīn al-Qazwīnī al-Kātibī and became the dominant system of Islamic logic until modern times.^[95]^[96] Avicennian logic also influenced several early European logicians such as Albertus Magnus^[97] and William of Ockham.^[98]^[99] Avicenna endorsed the law of non-contradiction proposed by Aristotle, that a fact could not be both true and false at the same time and in the same sense of the terminology used. He stated, "Anyone who denies the law of non-contradiction should be beaten and burned until he admits that to be beaten is not the same as not to be beaten, and to be burned is not the same as not to be burned."^[100]

Physics

In mechanics, Avicenna, in The Book of Healing, developed a 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.^[101] He viewed inclination as a permanent force whose effect is dissipated by external forces such as air resistance.^[102]

The theory of motion presented by Avicenna was probably influenced by the 6th-century Alexandrian scholar John Philoponus. Avicenna's is a less sophisticated variant of the theory of impetus developed by Buridan in the 14th century. It is unclear if Buridan was influenced by Avicenna, or by Philoponus directly.^[103]

In optics, Avicenna 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."^[104] 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 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.^[105]

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.^[106]

Psychology

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").^{[dubious – discuss]} Notably, Avicenna develops what is called the Flying Man argument in the Psychology of The Cure I.1.7 as defence of the argument that the soul is without quantitative extension, which has an affinity with Descartes's cogito argument (or what phenomenology designates as a form of an "epoche").^[82]^[83]

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.^[107]

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.^[108] The Active Intellect reveals the universals concealed in material objects much like the sun makes colour available to our eyes.

Other contributions

Astronomy and astrology

Main article: Astrology in the medieval Islamic world

Avicenna wrote an attack on astrology titled Missive on the Champions of the Rule of the Stars (رسالة في ابطال احكم النجوم) in which he cited passages from the Quran to dispute the power of astrology to foretell the future.^[109] He believed that each classical planet had some influence on the Earth but argued against current astrological practices.^[110]

Avicenna's astronomical writings had some influence on later writers, although in general his work could be considered less developed than that of ibn al-Haytham or al-Biruni. One important feature of his writing is that he considers mathematical astronomy a separate discipline from astrology.^[111] He criticized Aristotle's view of the stars receiving their light from the Sun, stating that the stars are self-luminous, and believed that the planets are also self-luminous.^[112] He claimed to have observed the transit of Venus. This is possible as there was a transit on 24 May 1032, but ibn Sina did not give the date of his observation and modern scholars have questioned whether he could have observed the transit from his location at that time; he may have mistaken a sunspot for Venus. He used his transit observation to help establish that Venus was, at least sometimes, below the Sun in the geocentric model,^[111] i.e. the sphere of Venus comes before the sphere of the Sun when moving out from the Earth.^[113]^[114]

He also wrote the Summary of the Almagest based on Ptolemy's Almagest with an appended treatise "to bring that which is stated in the Almagest and what is understood from Natural Science into conformity". For example, ibn Sina considers the motion of the solar apsis, which Ptolemy had taken to be fixed.^[111]

Chemistry

Avicenna was first to derive the attar of flowers from distillation^[115] and used steam distillation