The theories of the astronomers as to movements of the heavenly bodies are to be accepted--al-Ghazali adhered, of course, to the Ptolemaic system--but these deal only with the lowest plane, the world of sense. Behind all nature is God, who is on the plane of reality. This higher plane cannot be reached by reason or intellect, whose operations must rely on the evidence of sense perception. To reach the plane of reality man must be raised by a spiritual faculty, “by which he perceives invisible things, the secrets of the future and other concepts as inaccessible to reason as the concepts of reason are inaccessible to mere discrimination and what is perceived by discrimination of the senses” (op. cit.). Inspiration means the disclosing of realities to the prophets or saints, and these realities can only be known by such revelation or by the personal experience of ecstasy by which the soul is raised to the plane of reality. Not only are the religious truths in the Qur´an revealed, but all ideas of good and evil are similarly revealed, and could not be attained by the unaided use of reason, a view which is obviously intended to refute the Mu`tazilite claim that moral differences can be perceived by reason. The philosophers also have attained truths by revelation, and the main substance of medicine and astronomy is based on such revelation (op. cit.). 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.