Ibn Sina (Avicenna) is one of the foremost philosophers in the Medieval Hellenistic Islamic tradition that also includes al-Farabi and Ibn Rushd. His philosophical theory is a comprehensive, detailed and rationalistic account of the nature of God and Being, in which he finds a systematic place for the corporeal world, spirit, insight, and the varieties of logical thought including dialectic, rhetoric and poetry.
Central to Ibn Sina’s philosophy is his concept of reality and reasoning. Reason, in his scheme, can allow progress through various levels of understanding and can finally lead to God, the ultimate truth. He stresses the importance of gaining knowledge, and develops a theory of knowledge based on four faculties: sense perception, retention, imagination and estimation. Imagination has the principal role in intellection, as it can compare and construct images which give it access to universals. Again the ultimate object of knowledge is God, the pure intellect.
In metaphysics, Ibn Sina makes a distinction between essence and existence; essence considers only the nature of things, and should be considered apart from their mental and physical realization. This distinction applies to all things except God, whom Ibn Sina identifies as the first cause and therefore both essence and existence. He also argued that the soul is incorporeal and cannot be destroyed. The soul, in his view, is an agent with choice in this world between good and evil, which in turn leads to reward or punishment.
Reference has sometimes been made to Ibn Sina’s supposed mysticism, but this would appear to be based on a misreading by Western philosophers of parts of his work. As one of the most important practitioners of philosophy, Ibn Sina exercised a strong influence over both other Islamic philosophers and medieval Europe. His work was one of the main targets of al-Ghazali’s attack on Hellenistic influences in Islam. In Latin translations, his works influenced many Christian philosophers, most notably Thomas Aquinas.
Ibn Sina was born in AH 370/AD 980 near Bukhara in Central Asia, where his father governed a village in one of the royal estates. At thirteen, Ibn Sina began a study of medicine that resulted in ‘distinguished physicians… reading the science of medicine under [him]’ (Sirat al-shaykh al-ra’is (The Life of Ibn Sina): 27). His medical expertise brought him to the attention of the Sultan of Bukhara, Nuh ibn Mansur, whom he treated successfully; as a result he was given permission to use the sultan’s library and its rare manuscripts, allowing him to continue his research into modes of knowledge.
When the sultan died, the heir to the throne, ‘Ali ibn Shams al-Dawla, asked Ibn Sina to continue as vizier, but the philosopher was negotiating to join the forces of another son of the late king, Ala al-Dawla, and so went into hiding. During this time he composed his major philosophical treatise, Kitab al-shifa’ (Book of Healing), a comprehensive account of learning that ranges from logic and mathematics to metaphysics and the afterlife. While he was writing the section on logic Ibn Sina was arrested and imprisoned, but he escaped to Isfahan, disguised as a Sufi, and joined Ala al-Dawla. While in the service of the latter he completed al-Shifa’ and produced the Kitab al-najat (Book of Salvation), an abridgment of al-Shifa’. He also produced at least two major works on logic: one, al-Mantiq, translated as The Propositional Logic of Ibn Sina, was a commentary on Aristotle’s Prior Analytics and forms part of al-Shifa’; the other, al-Isharat wa-‘l-tanbihat (Remarks and Admonitions), seems to be written in the ‘indicative mode’, where the reader must participate by working out the steps leading from the stated premises to proposed conclusions. He also produced a treatise on definitions and a summary of the theoretical sciences, together with a number of psychological, religious and other works; the latter include works on astronomy, medicine, philology and zoology, as well as poems and an allegorical work, Hayy ibn Yaqzan (The Living Son of the Vigilant). His biographer also mentions numerous short works on logic and metaphysics, and a book on ‘Fair Judgment’ that was lost when his prince’s fortunes suffered a turn. Ibn Sina’s philosophical and medical work and his political involvement continued until his death.
Ibn Sina’s autobiography parallels his allegorical work, Hayy ibn Yaqzan. Both clarify how it is possible for individuals by themselves to arrive at the ultimate truths about reality, being and God. The autobiography shows how Ibn Sina more or less taught himself, although with particular kinds of help at significant moments, and proceeded through various levels of sophistication until he arrived at ultimate truths.
Such progress was possible because of Ibn Sina’s conception of reality and reasoning. He maintains that God, the principle of all existence, is pure intellect, from whom other existing things such as minds, bodies and other objects all emanate, and therefore to whom they are all necessarily related. That necessity, once it is fully understood, is rational and allows existents to be inferred from each other and, ultimately, from God. In effect, the totality of intelligibles is structured syllogistically and human knowledge consists of the mind’s reception and grasp of intelligible being. Since knowledge consists of grasping syllogistically structured intelligibles, it requires the use of reasoning to follow the relations between intelligibles. Among these intelligibles are first principles that include both concepts such as ‘the existent’, ‘the thing’ and ‘the necessary’, that make up the categories, and the truths of logic, including the first-figure syllogistics, all of which are basic, primitive and obvious. They cannot be explained further since all explanation and thought proceeds only on their basis. The rules of logic are also crucial to human development.
Ibn Sina’s stand on the fundamental nature of categorical concepts and logical forms follows central features of Aristotle’s thought in the Prior Analytics (see Aristotle §§4-7). Borrowing from Aristotle, he also singles out a capacity for a mental act in which the knower spontaneously hits upon the middle term of a syllogism. Since rational arguments proceed syllogistically, the ability to hit upon the middle term is the ability to move an argument forward by seeing how given premises yield appropriate conclusions. It allows the person possessing this ability to develop arguments, to recognize the inferential relations between syllogisms. Moreover, since reality is structured syllogistically, the ability to hit upon the middle term and to develop arguments is crucial to moving knowledge of reality forward.
Ibn Sina holds that it is important to gain knowledge. Grasp of the intelligibles determines the fate of the rational soul in the hereafter, and therefore is crucial to human activity. When the human intellect grasps these intelligibles it comes into contact with the Active Intellect, a level of being that emanates ultimately from God, and receives a ‘divine effluence’. People may be ordered according to their capacity for gaining knowledge, and thus by their possession and development of the capacity for hitting on the middle term. At the highest point is the prophet, who knows the intelligibles all at once, or nearly so. He has a pure rational soul and can know the intelligibles in their proper syllogistic order, including their middle terms. At the other end lies the impure person lacking in the capacity for developing arguments. Most people are in between these extremes, but they may improve their capacity for grasping the middle term by developing a balanced temperament and purity of soul (see Logic in Islamic philosophy §1).
In relation to the older debate about the respective scopes of grammar and logic, Ibn Sina argues that since logic deals with concepts that can be abstracted from sensible material, it also escapes the contingencies of the latter. Language and grammar govern sensible material and therefore have a different domain; indeed, languages are various and their rules of operation, their grasp of sensible material, are likewise articulated variously (see Language, philosophy of). Nevertheless, languages make available the abstracted concepts whose operation is governed by logic; yet if language deals with contingencies, it is not clear how it can grasp or make available the objects of logic. At times, as for example in al-Isharat, Ibn Sina suggests that languages generally share a structure.
In his theory of knowledge, Ibn Sina identifies the mental faculties of the soul in terms of their epistemological function. As the discussion of logic in §2 has already suggested, knowledge begins with abstraction. Sense perception, being already mental, is the form of the object perceived (see Sense and reference §1). Sense perception responds to the particular with its given form and material accidents. As a mental event, being a perception of an object rather than the object itself, perception occurs in the particular. To analyse this response, classifying its formal features in abstraction from material accidents, we must both retain the images given by sensation and also manipulate them by disconnecting parts and aligning them according to their formal and other properties. However, retention and manipulation are distinct epistemological functions, and cannot depend on the same psychological faculty; therefore Ibn Sina distinguishes faculties of relation and manipulation as appropriate to those diverse epistemological functions (see Epistemology in Islamic philosophy §4).
Ibn Sina identifies the retentive faculty as ‘representation’ and charges the imagination with the task of reproducing and manipulating images. To conceptualize our experience and to order it according to its qualities, we must have and be able to reinvoke images of what we experienced but is now absent. For this we need sensation and representation at least; in addition, to order and classify the content of representation, we must be able to discriminate, separate out and recombine parts of images, and therefore must possess imagination and reason. To think about a black flag we must be able to analyse its colour, separating this quality from others, or its part in the image from other images, and classify it with other black things, thereby showing that the concept of black applies to all such objects and their images. Imagination carries out this manipulation, allowing us to produce images of objects we have not seen in fact out of the images of things we have experienced, and thereby also generating images for intelligibles and prophecies.
Beyond sense perception, retention and imagination, Ibn Sina locates estimation (wahm). This is a faculty for perceiving non-sensible ‘intentions that exist in the individual sensible objects’. A sheep flees a wolf because it estimates that the animal may do it harm; this estimation is more than representation and imagination, since it includes an intention that is additional to the perceived and abstracted form and concept of the animal. Finally, there may be a faculty that retains the content of wahm, the meanings of images. Ibn Sina also relies on a faculty of common sense, involving awareness of the work and products of all the other faculties, which interrelates these features.
Of these faculties, imagination has a principal role in intellection. Its comparison and construction of images with given meanings gives it access to universals in that it is able to think of the universal by manipulating images (see Universals). However, Ibn Sina explains this process of grasping the universal, this emergence of the universal in the human mind, as the result of an action on the mind by the Active Intellect. This intellect is the last of ten cosmic intellects that stand below God. In other words, the manipulation of images does not by itself procure a grasp of universals so much as train the mind to think the universals when they are given to the mind by the Active Intellect. Once achieved, the processes undergone in training inform the mind so that the latter can attend directly to the Active Intellect when required. Such direct access is crucial since the soul lacks any faculty for retaining universals and therefore repeatedly needs fresh access to the Active Intellect.