and in 484 he was appointed president of the Nazmiite Academy at Baghdad. Gradually, however, he became a prey to spiritual unrest, and in 488 resigned his post and retired to Syria, where he spent some years in study and the practices of devotion. In 499 he returned to active work as a teacher in the Nazimite Academy at Naisabur, where he became the leader of a modified Ash'arite system strongly leavened by mysticism, which we may regard as the final evolution of orthodox Muslim theology.
Al-Ghazali, following al-Ash'ari, taught that philosophical theory cannot form the basis of religious thought, thus opposing the position of the philosophers. By revelation only can the primary essentials of truth be attained. Philosophy itself is no equal or rival of revelation: it is no more than common sense and regulated thinking, which may be employed by men about religion or any other subject; at best it acts as a preservative against error in deduction and argument, the primary material for which, so far as religion is concerned, can be furnished only by revelation. But against this he appears also as the transmitter of the teaching already given, by al-Qushayri, which introduced the mysticism of the Sufis into orthodox Islam. Revelation indeed is given by means of the Qur'an and tradition, and it is sufficient to accept what is thus revealed, but the ultimate truth of revelation can be tested and proved only by the experience of the individual. So far as men are concerned this is possible by means
