AVICENNA (Abū 'Alī al-Ḥusajīn ibn 'Abd Allāh ibn Sīnā, called by Latin scholasticism Avicenna): - One of the greatest Arab philosophers, a celebrated physician, encyclopedic in his learning and therefore called the "chief sage" and "the third master," after Aristotle and al-Fārābī. Born in 980, in a village in the region of Bukhara, in the eastern part of Persia, where he spent his life; for some time he was wazīr, that is, minister, of the prince Sams ad-Dawlah at Hamadān; for political reasons he suffered several months of imprisonment; but he devoted the greater and better part of his life to the study of philosophy, medicine and the sciences. He died at Hamadān in 1037.
A. created a great philosophical system of a character
Aristotelian, yet imbued with Platonic and Neoplatonic ideas: a system with an empirical basis, with a Neoplatonic and mystical apex. A. shows a strong tendency to reconcile the Islamic religion with Aristotelian philosophy, though at the expense of the former, since, while not combating revealed truths, he wants to see in the teachings of the Koran adaptations made by Mohammed to the crude mentality of the Arabs of his time. It was said that A. formulated the doctrine of double truth, religious and philosophical. In any case, not a few of his philosophical doctrines are wholly irreconcilable with those of the Koran. He was therefore opposed by Algazel, champion of religion against Greek philosophy, atheistic and foreign.
A. wrote about a hundred works, most of them short, though some of great bulk, such as the philosophical encyclopedia al-Šifā', that is, The Healing, and the Canon of medicine. Most of these works are in Arabic, and some in Persian, A.'s native tongue. The Healing consists of four main sections: logic, physics, the (mathematical) disciplines, and metaphysics, and it is the most detailed exposition of his system. The section devoted to physics consists of eight parts, of which the sixth treats of the soul: it is the Liber sextus naturalium, well known to Latin scholasticism, which also knew the metaphysics. The Kitāb an-nağāt is a compendious extract of The Healing. This book was published, together with the Canon, in Rome in 1593. Logic and metaphysics are also set forth in the Kitāb al-šifārāt wat-tanbīhāt. Among the shorter books of philosophy are an epistle on the division of the sciences, and various treatises on psychology. Mention should also be made of his various writings on mystical subjects. He also wrote on alchemy, music, and astronomy, and dealt in his letters with various questions of science and philosophy.
In logic, which according to him also embraces rhetoric and poetics, A. follows Aristotle and Porphyry's Introduction. The syllogistic is, however, treated only briefly.
Wisdom (al-ḥikmah), which comprises all the sciences, is divided into theoretical and practical. The first, which tends toward truth, comprises physics, mathematics, and theology; the second, which is directed toward the good, consists of ethics, economics, and politics. The object of physics is bodies composed of matter and form, endowed with primary and secondary qualities or powers, in a state of rest or in motion. Bodies are in a place and in time, the concept of the latter deriving from that of motion. Every body has its own natural place. A. demonstrates that the void does not exist. He also treats of the problem of the infinite, which he admits for the past; moreover, bodies are divisible to infinity in potency, as is motion.
Although in the doctrine of the soul too A. shows himself a faithful disciple of Aristotle, nevertheless, in certain respects, he departs from the master. He demonstrates, with various arguments, the existence of the soul, its spirituality and therefore its immortality: it is a simple substance, which expands in the body as the trunk expands its branches, and this substance is what man truly is. Soul and body, wholly different from each other, are dependent one upon the other not substantially, but "per accidens," and therefore the soul does not perish with the death of the body. It does not, however, exist before the body, but is created at the very moment of the generation of that body to which it is destined and for which it therefore receives a special preparation. When it leaves the body, each soul remains a being distinct from the other souls. In consequence of this individuality A. rejects metempsychosis. The soul can be of three kinds: vegetative, animal, and rational, of which the first is characteristic of plants, the second of animals, and the third of man. Treating of the latter two, A. observes that it is within the faculty of the animal to grasp particulars and to move voluntarily, while the rational soul grasps universals and acts by free choice. The animal soul performs an incomplete work of abstraction on the data furnished by the senses, without stripping them entirely of their matter. It has four faculties: the formative, the cogitative, opinion (al-tushm), and memory, which constitute internal perception, which must be distinguished from external perception, constituted by the activity of the senses.
The rational soul, or intelligence, is divided first of all into theoretical and practical. The theoretical is the perceptive faculty and stands in relation to the principles superior to it, which it obeys. In the perceptive faculty one must distinguish the material intellect, which is the absolute possibility of knowing, the possible intellect, which is in act with respect to the former and has acquired the first and necessary truths, the intellect in act, which is in a state of perfect preparation for the acquired intellect, when the comprehension of forms takes place. Moreover, some men have the holy spirit, which would constitute a fifth stage, in which things are known immediately. Now the intellect in potency does not pass into act except through the operation of the intellect that is always in act, which is, however, a substance outside man; in it reside the intelligible forms of the objects of knowledge. To know a thing, the rational soul must therefore be conjoined with the agent intellect, but without becoming that intellect outright. The soul grasps universals or intelligibles, first extracted from the particulars brought to it by the senses, comprehending them in act through its conjunction with the agent intellect, in which those intelligibles reside. Particulars, besides being perceived by the senses, are also comprehended by the intellect, not however as particulars, but as effects of their cause: this comprehension constitutes the science of particulars, which must be distinguished from their perception by the senses. The soul thus rises from sense and reaches the agent intellect: it therefore has one side turned downward and another turned upward, it detaches itself from the senses to draw ever closer to universal realities and thus to return to its origin and its essence.
Metaphysics, or first philosophy or al-illāhijāt, is the science of abstract concepts, concerning all beings and the first principles of the sciences and of the world of supraterrestrial beings, as well as of God. In the scale of beings the supreme place is occupied by the necessary being, God, whose existence A. seeks to demonstrate: a being that has neither body nor matter nor form, that is not divisible, and in which therefore has no part before or after, but everything that is possible in him is necessary at the same time. God is truth, goodness, power, life, pure knowledge, but with all this he is a single cause, he is the One and the Only. He knows particulars in a universal manner. His essence has neither genus nor difference and cannot be defined. It is impossible to imagine him as non-existent. From this being emanates the world of ideas, of pure intelligences, then the world of essences, clothed in a certain way with matter, which govern the bodies of the spheres and through them the elements; then the physical world with the forces infused in bodies and finally the world of bodies. A. sought to deduce in an ingenious manner, though hardly persuasive, the multiple of the sublunary world from the One of the necessary being, by means of the knowledge that the first caused being has of itself as first, as possible in itself and as necessary from the first, and similarly of the lower emanations, to arrive at the agent intellect, which governs the world of man. A. also confers soul and body upon the spheres and compares their soul with the animal soul of man. The sphere-soul seeks to resemble the supreme good and thus to enter into a state of perfection. The first cause of the movement of the spheres is the first mover, God, who stands, however, above all movement. Avicennian emanatism is found among Arab philosophers already in al-Fārābī. A. also dealt with the problem of evil. He affirms that in God's judgment evil is only accidental, it is merely negative, it is a lack or defect and does not touch intelligibles, but strikes only particulars or individuals. Good in the world is superior to evil numerically and quantitatively. A. is therefore an optimist.
One enters the field of mysticism with the doctrine of the fate of rational souls after separation from bodies. They then tend toward perfection, which is their essence, seeking to become intelligent and wise and to assimilate themselves ever more to God. To prepare for this life man must already in this world lead an intellectual existence, superior to the senses. Thus the soul will be able to reach a state of happiness. When instead it is impure, it suffers, and its sufferings diminish the more it purifies itself. Spiritual souls, after the death of the body, enter into God's mercy, while the souls that are entirely wicked suffer terrible pains.
Besides his philosophy, A. owes the great fame he has enjoyed to the medical art, of which he was one of the great masters, followed for certain doctrines still in the last century. His Canon of Medicine represents a grandiose attempt to order into a system all the medical doctrines of Hippocrates and Galen, together with the biological conceptions of Aristotle. The Avicennian doctrine is based on the humoral theory of Hippocrates. All physicians have admired in A., besides the clear and suggestive style, the precision in therapeutic indications and the clarity in clinical histories.