If a list of the half dozen most important figures in the historical elaboration of Islam were to be drawn up, there can be no doubt that Abu Hamid Ghazali would figure on that list. As a versatile and gifted scholar and, more importantly, a believer of great spiritual insight, he confronted all the intellectual and spiritual currents of his day and elaborated what might be called a defining synthesis of Sunni Islam. He achieved this result through both lengthy personal experience and erudition, and this lecture deals, therefore, both with his life and his works, as well as attempting to assess his impact on the religious history of Islam.