limits of orthodoxy. Amongst others the Emir received a letter inviting such men of learning as were to be found in Khwarazan to his court. The Emir read out the letter to the five most distinguished scholars who were his guests, leaving them to act as they thought fit. Three of the guests were attracted by the Sultan's reputation for generosity and accepted the invitation, but two, Ibn Sina and Masihi, were afraid to venture, so they escaped privately and fled; overtaken by a sandstorm in the desert Masihi perished, but Ibn Sina, after long wanderings, finally found a refuge in Isfahan, where the Buwayhid 'Ala'u d-Dawla Muhammad held his court. His experiences show plainly that it was the Shi'ites who were the supporters of philosophy, and that the growing Turkish power of Mahmud of Ghazna and of the Seljuks who succeeded him was reactionary and unfavourably disposed towards philosophical research. It was the Turkish power which finally checked the progress of Arabic philosophy in the East.
Ibn Sina wrote many works in Arabic and Persian, and a number of these are still extant. Amongst his productions were as-Shafa, an encyclopædia of physics, metaphysics, and mathematics in eighteen volumes (ed. Forget, Leiden, 1892), a treatise on logic and philosophy, and the medical works on which his fame so largely rests. The best known of these are the Najat abridged from the as-Shafa, and the medical Canon, in which he reproduced the teaching
