ALHAZEN, a learned Arabian, who flourished in Spain about the beginning of the twelfth century. No particulars of his life have been transmitted to the pre sent day. He wrote a treatise on Optics, and another on Astrology ; the former of which was published in 1572, in the Thesaurus Opaces of Risne, and was illustrated by Vitcllio, in a work on the same subject, published in 1270. Alhazen was the author of several important dis coveries respecting vision, refraction, and lenses ; but these will be more properly detailed in the History of OPTICS. See Priestley's Hist. of Vision, Sze. vol. i. p. 17. _Hist. des Mathemat. par Montucla, tom. i. p. 577 ; and Smith's Optics, vol. ii. Rem. p. 15. (w) ALI, the son of Abu Taheb, and the cousin-gerrnan and pupil of Mahomet. Ali, by his intrepidity and in fluence, was of infinite service to Mahomet, in promot ing the extraordinary project, which he had conceived, of giving a new religion to the Arabs. When the im postor thought his scheme ripe for execution, he direct ed Ali, whom he had taken under his protection from his infancy, to prepare an entertainment, and invite to it all the descendants of his grandfather Abdal Motalleb. Mahomet, however, had not an opportunity of disclosing his mind at this meeting, as the company broke up be fore he had time to harangue them. Ali therefore in vited the same party next clay ; and, as soon as they were assembled, Mahomet thus addressed them :—" offer you the felicity both of this world, and of that which is to come. God bath commanded me to call you unto him ; who, therefore, will be my visir, (or assistant,) and become my brother and my vicegerent ?" None of the company seemed very forward in aspiring to this honourable distinction ; when Ali, starting up, exclaimed with vehemence, " I, 0 prophet of God, will be thy visir ; and I will beat out the teeth, pull out the eyes, rip open the bellies, and cut off the legs, of all who shall dare to oppose thee." Upon this, Mahomet, embracing him, thus addressed the company :—" This is my brother, my deputy, and my successor ; therefore shcw yourselves submissive and obedient." This ha rangue was received by the company as it deserved, with s‘:orn and derision. Nothing, however, could shake the attachment of All to his friend and protector ; he stood by hint in all his difficulties, and often exposed himself to the most imminent danger, in order to promote his views. Mahomct, being hard pressed by his inveterate enemies the Koreish, found it expedient to retire to Me dina, where he had gained many partisans. His enemies, having learned his intention, and dreading the conse quence of his appearing at the head of a powerful party, came to a determination to assassinate him. For this purpose, one man was singled out from every tribe, that the guilt might be equally divided amongst them. Ma hornet, having got notice of their design, which was in stantly to be carried into execution, prevailed on All to wrap himself up in his green cloak, and lie down in his place, till he should have escaped to a sufficient distance. In this situation, Ali was surrounded by the conspirators, who, looking through the crevice, and seeing Mahomet, as they believed, asleep, waited patiently till they should obtain admittance. When morning came, Ali arose, and the conspirators found, to their infinite mortification, that the object of their resentment had escaped, and that one, with whom they had no quarrel, was left in his place.
Ali often distinguished himself in single combat with the most renowned champions on the side of the enemy, and always came off victorious. From his acknowledged talents and bravery, and also from his connection with Mahomet, being both his cousin-german and his son-in law, he naturally looked forward to the succession to the caliphat on the death of the impostor. Abu Becr, how ever, Alabama's father-in-law, was preferred to him, chiefly through the influence of Omar. Ali was very much displeased with the election, but was soon re duced to submission, as the new caliph sent Omar with orders to burn the house, in which All and his friends were assembled, unless they concurred with the general sentiment. On the death of Abu Beer, All was again excluded, and Omar quietly succeeded, being nominated by the last will of the caliph. On the assassination of Omar, Ali again appeared as a candidate, and was again excluded, through the intrigues of a party, Othman be ing elected as successor to Omar. It is much to the honour of Ali, that he continued faithful to the several princes, by whose election he had so long been deprived of what he reckoned his birth-right, as he was the near est male relation of Mahomet. He had now, indeed, seen so much of the turbulence and factious spirit of the leading men of the state, that he was heartily cured of his love of sovereignty ; insomuch, that, when Othman was murdered by his rebellious subjects, and the eyes of all were turned towards Ali as his successor, he declined, with the utmost earnestness, that honour, to which he had formerly so keenly aspired. He was compelled, however, to accept of it, by the entreaties of his friends, and the threats of the people. No sooner had he taken into his hands the reins of government, than he found himself embroiled with his rebellious subjects. Teiha and Zobier, in conjunction with Ayesha, Mahomet's favourite wife, rose in open rebellion. This insurrection was soon suppressed ; but Ali found a more formidable enemy in Moawiyah the prefect of Syria, and head of the powerful family of Ommiyah. After several bloody en gagements, Ali was induced to submit his dispute with Aloawiyah to arbitration, when, by a foul trick, he was deprived of his authority, and his competitor declared the lawful caliph. This, however, did not end the dis pute ; Ali was taking the most effectual means to reco vet' his authority, when he was assassinated by a fanatic, who, with two others, had made a solemn vow to rid the world of Ali, Moawiyali, and a third competitor, Am ruclen Al As. The attempt against Ali only was suc cessful. Thus fell one of the bravest of the f011owers of Mahomet, after a short reign of four years and nine months. He is reckoned by his followers the first of believers, though it is certain, that both Mahomet's wife and father-in-law were converted before him.
The sect of All is still one of the principal sects amongst the Mahometans. Their distinguishing tenet, is, that Ali and his descendants are the only lawful suc sessors of Mahomet, and, of course, that all the caliphs, who are not of his family, are usurpers. The Persians, who are of the sect of Ali, maintain his prerogative with as much obstinacy as the Roman Catholics do that of St Peter ; whilst the Turks, who are of the sect of Omar, denounce Ali as an innovator in their religion ; and consider the opinions of his followers as damnable heresy. (g)