Avicenna [Abū ‛Alī al-Husain ibn ‛Abdallāh ibn Sīnā] (980-1037), Arabian philosopher, was born at Afshena in the district of Bokhara. His mother was a native of the place; his father, a Persian from Balkh, filled the post of tax-collector in the neighbouring town of Harmaitin, under Nūh II. ibn Mansur, the Samanid amir of Bokhara. On the birth of Avicenna's younger brother the family migrated to Bokhara, then one of the chief cities of the Moslem world, and famous for a culture which was older than its conquest by the Saracens. Avicenna was put in charge of a tutor, and his precocity soon made him the marvel of his neighbours, - as a boy of ten who knew by rote the Koran and much Arabic poetry besides. From a greengrocer he learnt arithmetic; and higher branches were begun under one of those wandering scholars who gained a livelihood by cures for the sick and lessons for the young. Under him Avicenna read the Isagoge of Porphyry and the first propositions of Euclid. But the pupil soon found his teacher to be but a charlatan, and betook himself, aided by commentaries, to master logic, geometry and the Almagest. Before he was sixteen he not merely knew medical theory, but by gratuitous attendance on the sick had, according to his own account, discovered new methods of treatment.

For the next year and a half he worked at the higher philosophy, in which he encountered greater obstacles. In such moments of baffled inquiry he would leave his books, perform the requisite ablutions, then hie to the mosque, and continue in prayer till light broke on his difficulties. Deep into the night he would continue his studies, stimulating his senses by occasional cups of wine, 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 Fārābī (q.v.), which he bought at a bookstall for the small sum of three dirhems. So great was his joy at the discovery, thus made by help of a work from which he had expected only mystery, that he hastened to return thanks to God, and bestowed an alms upon the poor. Thus, by the end of his seventeenth year his apprenticeship of study was concluded, and he went forth to find a market for his accomplishments.

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

At the age of twenty-two Avicenna lost his father. The Samanid dynasty came to its end in December 1004. Avicenna seems to have declined the offers of Mahmūd the Ghaznevid, and proceeded westwards to Urjensh in the modern Khiva, where the vizier, regarded as a friend of scholars, gave him a small monthly stipend. But the pay was small, and Avicenna wandered from place to place through the districts of Nishapur and Merv to the borders of Khorasan, seeking an opening for his talents. Shams al-Ma‛ālī Qābūs, the generous ruler of Dailam, himself a poet and a scholar, with whom he had expected to find an asylum, was about that date (1012) starved to death by his own revolted soldiery. Avicenna himself was at this season stricken down by a severe illness. Finally, at Jorjān, near the Caspian, he met with a friend, who bought near his own house a dwelling in which Avicenna lectured on logic and astronomy. For this patron several of his treatises were written; and the commencement of his Canon of Medicine also dates from his stay in Hyrcania.

He subsequently settled at Rai, in the vicinity of the modern Teheran, where a son of the last amir, Majd Addaula, was nominal ruler, under the regency of his mother. At Rai about thirty of his shorter works are said to have been composed. But the constant feuds which raged between the regent and her second son, Shams Addaula, compelled the scholar to quit the place, and after a brief sojourn at Kazwīn, he passed southwards to Hamadān, where that prince had established himself. At first he entered into the service of a high-born lady; but ere long the amir, hearing of his arrival, called him in as medical attendant, and sent him back with presents to his dwelling. Avicenna was even raised to the office of vizier; but the turbulent soldiery, composed of Kurds and Turks, mutinied against their nominal sovereign, and demanded that the new vizier should be put to death. Shams Addaula consented that he should be banished from the country. Avicenna, however, remained hidden for forty days in a sheik's house, till a fresh attack of illness induced the amir to restore him to his post. Even during this perturbed time he prosecuted his studies and teaching.

Every evening extracts from his great works, the Canon and the Sanatio, were dictated and explained to his pupils; among whom, when the lesson was over, he spent the rest of the night in festive enjoyment with a band of singers and players. On the death of the amir Avicenna 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 Isfahan, offering his services; but the new amir of Hamadān getting to hear of this correspondence, and discovering the place of Avicenna's concealment, incarcerated him in a fortress. War meanwhile continued between the rulers of Isfahan and Hamadān; in 1024 the former captured Hamadān and its towns, and expelled the Turkish mercenaries. When the storm had passed Avicenna returned with the amir to Hamadān, and carried on his literary labours; but at length, accompanied by his brother, a favourite pupil, and two slaves, made his escape out of the city in the dress of a Sufite ascetic. After a perilous journey they reached Isfahan, and received an honourable welcome from the prince.