With the time came the man. He was al-Ghazzali, the greatest, certainly the most sympathetic figure in the history of Islam, and the only teacher of the after generations ever put by a Muslim on a level with the four great Imams. The equal of Augustine in philosophical and theological importance, by his side the Aristotelian philosophers of Islam, Ibn Rushd and all the rest, seem beggarly compilers and scholiasts. Only al-Farabi, and that in virtue of his mysticism, approaches him. In his own person he took up the life of his time on all its sides and with it all its problems. He lived through them all and drew his theology from his experience. Systems and classifications, words and arguments about words, he swept away; the facts of life as he had known them in his own soul he grasped. When his work was done the revelation of the mystic (_kashf_) was not only a full part but the basal part in the structure of Muslim theology. That basis, in spite, or rather on account of the work of the mutakallims had previously been lacking. Such a scepticism as their atomic system had practically amounted to, could disprove much but could prove little. If all the categories but substance and quality are mere subjectivities, existing in the mind only, what can we know of things? An ultra-rational basis had to be found and it was found in the ecstasy of the Sufis. But al-Ghazzali brought another element into fuller and more effective working. With him passes away the old-fashioned kalam, a thing of shreds and patches, scraps of metaphysics and logic snatched up for a moment of need, without grasp of the full sweep of philosophy, and incapable, in the long run, of meeting it. Even its atomic system is a philosophy of amateurs, with all their fantastic one-sidedness, their vigor and rigor. But al-Ghazzali was no amateur. His knowledge and grasp of the problems and objects of philosophy were truer and more vital than in any other Muslim up to his time—perhaps after it, too. Islam has not fully understood him any more than Christendom fully understood Augustine, but until long after him the horizon of Muslims was wider and their air clearer for his work. Then came a new scholasticism, reigning to this day. So much by way of preface. We must now give some account of the life and experiences, the ideas and sensations, of this great leader and reformer. For his life and his work were one. Everything that he thought and wrote came with the weight and reality of personal experience. He recognized this connection himself, and has left us a book—the _Munqidh min ad-dalal_, “Rescuer from Error”—almost unique in Islam, which, in the form of an apology for the faith, is really an _Apologia pro vita sua_. This book is our main source for what follows. [Sidenote: EARLY CAREER; RENUNCIATION]