Unlike Ibn Rushd, al-Ghazali thus emphasizes supra-rational intuition attained in a state of ecstasy, whereby the soul is raised above the world of shadow and reflection to the plane of reality. This was pure mysticism, and thus al-Ghazali introduces a Sufi element into orthodox Islam. At the same time he reduced Sufism to a scientific form, and endorsed the Plotinian terminology. Macdonald summarises his work under four heads: (i.) he established an orthodox mysticism; (ii.) he popularised the use of philosophy; (iii.) he rendered philosophy subordinate to theology, and (iv.) he restored the fear of God when the element of fear was tending to be thrust into the background, at least by the educated. From this time on the term _kalam_ was usually applied to philosophy adapted to the use of theologians.
The chief works left by al-Ghazali are the _Ihya `Ulum ad-Din_, of which it is understood that a translation by H. Bauer is in preparation, and the _Mi´yar al-`Ilm_, a treatise on logic. To posterity, however, he is best known by his _Confessions_, an autobiographical account of his spiritual life and development, which may not unfitly be placed beside the Confessions of St. Augustine.
Al-Ghazali completes the development of orthodox Muslim theology. From this time forth it ceased to have any originality, and for the most part showed signs of decadence. Here and there we find Sufi revivals; indeed, Sufism is the only phase of Islam which kept free from the rigid conservatism which has laid its iron hand of repression upon Muslim life and thought generally. In Yemen the system of al-Ghazali was kept alive by generations of Sufis, but for the most part Sufism preferred less orthodox paths. Against these Sufi movements we see from time to time others of a distinctly reactionary character, such as that of the Wahabis, who opposed the theology of al-Ghazali when it was generally recognised as the orthodox teaching at Mecca, and in this they were followed by the Sanusi.
_Sayyid Murtada_ (d. 1205 A.H. = 1788 A.D.), a native of Zabid in Yihama, wrote a commentary on al-Ghazali’s _Ihya `Ulum ad-Din_, and thus revived the study of the great scholastic theologian. From that time the Islamic community has not lacked neo-Ghazalian students, and many consider that that school contains the best promise for modern Islam.