The “House of Wisdom” continued until 513 when the reactionary wave of orthodoxy had reached even Fatimid Egypt, and in that year it was closed as a home of heresy by the Wazir Afdal. Four years later a new academy near the great palace was founded by the Wazir Maʾmun, but this adhered more strictly to the traditional lines of Muslim study. In the line of philosophers strictly so-called, that is to say, of those who worked from the basis of Greek science, one is associated with al-Hakim and the Cairo of the Fatimids, namely, Ibn al-Haytsam, known to the mediaeval Latin writers as Alhazen. He was born at Basra in 354, and became distinguished as a student of the Greek philosophers. At that time the path of philosophy was beset with many difficulties owing to the orthodox reaction. Ibn Sina was a wanderer in many lands, and Ibn al-Haytsam found it more prudent to seek a refuge in Cairo where he made his home amongst the learned of the al-ʾAzhar mosque. He died in 430. We have a long list of the works he produced, all of the type usually associated with the Arabic philosophers, manuals, commentaries, and discussions of questions arising from the teaching of the ancients. In his case these deal chiefly with mathematics, physics, the Aristotelian logic, and the medical works of Galen. The Bodleian contains a MS. of his commentary on Euclid. To the mediaeval west he was best known as the author of a treatise on optics which was translated into Latin and used by Roger Bacon. Occasionally this optical work of “Alhazen” appears in the curricula of the mediaeval universities. Various evidences of a fanatical spirit in maintaining the doctrines and usages of Shiʿism begin to appear in al-Hakim about 393. In Syria a person was arrested on the charge that he denied that any special devotion was due to ʿAli. The offender was imprisoned by the authority of the Chief Qadi of Egypt who acted as pope over all the territories subject to Fatimid rule, and was examined by four jurists who did their best to persuade him to recognise the Imamate of ʿAli, but, as he remained stubborn, he was beheaded. In Cairo thirteen persons were arrested for having observed the _Salat ad-Duha_ or “mid-morning prayer,” one of the voluntary observances sometimes added to the five canonical daily prayers, but disapproved by the Shiʿites. The offenders were paraded through the streets, beaten, and detained three days in prison. In the month of Rabiʿ II. of this same year (393) a man named Aswad Hakami was punished for some offence of which the details are unknown, but which probably was a public championship of the three first Khalifs whom the Shiʿites regarded as usurpers. He was paraded through the city and a herald cried before him: “This is the reward of those who are the partisans of Abu Bakr, and Umar,” after which he was beheaded (As-Suyuti, _History_, chap. I., Qadir bi-llah).