Abu ‘Ali Ibn Sina (ca. 980-1037 CE), known in Latin as Avicenna, was a physician, natural philosopher, mathematician, poetic mystic, and princely minister. Of Persian descent, he was born in Afshana in the province of Bukhara. His chief philosophical work, Kitab al-shifa’ (Book of Healing), which was known in Latin as Liber Sufficientia, together with its condensed revision, Kitab al-najat (Book of Deliverance), led many to regard him as being the authoritative Neoplatonist integrator of the Aristotelian corpus. However, his intellectual acumen elevates his station beyond that of a commentator and lets him stand as an insightful thinker in his own right. His philosophical investigations covered mathematics, music, logic, physical and psychical sciences, as well as metaphysics and theology.
In geometry, he critically examined Euclid’s Elements and attempted to prove its fifth postulate. In his Aristotelian intromission conception of vision, he showed that the velocity of light had a finite magnitude. Partly influenced by Porphyry's Isagoge, Aristotle's Organon, and Galen's logical investigations, he eventually developed intricate forms of propositional logic. Furthermore, he founded a proto-theory of meaning that was partially embodied in his work Kitab al-hudud (Book of Definitions), wherein he arrived at definitions by way of a rigorous distinction among concepts. Unlike most Platonists, he celebrated the merits of the art of persuasion and rhetoric. In astronomy, he endeavoured to systematise his observations that were grounded in Ptolemy's Almagest, and in mechanics he built on the theories of Heron of Alexandria while also seeking to improve the precision of instrumental readings. In his physical inquiries he studied different forms of energy, heat and force, while presenting a more coherent account of the interconnection between time and motion than what is habitually associated with Aristotle's Physics. One of his important achievements in natural philosophy was his account of the soul in Kitab al-nafs (Treatise on the Soul), which was preserved in his al-Shifa and al-Najat, and was translated into Latin under the title De Anima. Therein, he presented an affirmation of the existence of the soul that rested on a radical mind-body dualism in an argument that is customarily referred to as “the flying person argument,” which anticipates Descartes's “cogito ergo sum.” He also elucidated the notion of “intentionality” in the workings of the internal sense of the facility of estimation (wahm) and its pragmatic entailments.
Ranking among the most influential of metaphysicians in the history of philosophy, Ibn Sina offered an original elucidation of the question of “being” (al-wujud) that was mediated by a methodical distinction between essence and existence and oriented by an ontological consideration of the modalities of necessity, contingency, and impossibility. Taking the contingent to be a mere potentiality of being, whose existence or nonexistence did not entail a contradiction, Ibn Sina construed all creatures in actuality as being necessary existents due to something other than themselves. Consequently, any contingent had its essence distinct from its existence while being existentially dependent on causes that are external to it, which lead back to the One Necessary Existent due to Itself Whose Essence is none other than Its Existence. In this, Ibn Sina eschewed Aristotle’s reduction of “being” into the Greek conception of ousia (substance or essence), and he conceived the Deity as being the metaphysical First Cause of existence rather than being the physical Unmoved Cause of motion. Although his consideration of Divine creation was primarily mediated by an attempt to found a synthesis between Aristotle’s naturalism and monotheistic creationism, his ontology remained more akin to Neoplatonist emanationism, which took the One Necessary Existent to be the Source of all existential effusion. In this processional hierarchical participation in “being”, the Active Intellect played a necessary role in the genesis of human knowledge.
Following Plato, Ibn Sina held that knowledge, consisting of grasping the intelligible, ultimately determined the fate of the rational soul in the hereafter. Believing that the universality of our ideas was attributed to the mind itself, he additionally held that our passive individual intellects are in a state of potency with regard to knowledge, unlike the Active impersonal and separate Intellect that is in a state of actual perennial thinking. Consequently, our passive intellect qua mind acquires ideas by being in contact with the Active Intellect without compromising its own independent substantiality or immortality. In a mystical tone that becomes most pronounced in Kitab al-isharat wa-l-tanbihat (Book of Hints and Pointers), Ibn Sina also maintained that certain elect souls are capable of realising a union with the Universal Active Intellect, thereby attaining the station of prophecy.
His philosophical views were debated by Averroes and Maimonides, criticised by al-Ghazali, and integrated by intellectual authorities in medieval Europe, such as Thomas Aquinas, Duns Scotus, and Roger Bacon. His thinking also impacted the course of development of the ontotheological systems of prominent Muslim scholars such as Suhrawardi, Tusi, and Mulla Sadra. In all of this, his philosophical wisdom did not outshine his celebrated reputation as a physician, and his classic Kitab al-qanun fi’l-tibb (The Canon in Medicine), which was translated into Latin in the twelfth century CE (Liber Canonis), commanded an authority that almost surpassed that of Hippocrates and Galen and acted as the decisive compendium of the Greco-Roman- Arabic scientific medicine, and as the reference Materia Medica, throughout the medieval period and up to the Renaissance.
Ibn Sina. Kitab al-shifa’, al-ilahiyyat. Edited by Ibrahim Madkour, George Anawati, and Said Zayed. Cairo: al-Hay’a al-misriyya al-‘amma lil-kitab, 1975.
---. Kitab al-shifa’, Kitab al-nafs. Edited by Fazlur Rahman. Oxford: Oxford University Press, 1960.
---. Kitab al-najat. Edited by Majid Fakhry. Beirut: Dar al-afaq al-jadida, 1985.
---. Kitab al-hudud (Livre des definitions). Edited and translated by A. M. Goichon. Cairo: Institut francais d’archeologie orientale du Caire, 1963.
---. Kitab al-‘isharat wa’l-tanbihat (Le livre des directives et remarques). Edited and translated by A. M. Goichon. Paris: J. Vrin, 1999.
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