Who is al-Ghazali? This is an interesting question in and of itself. Those who knew him would say he had two main stages in his life: before and after his retreat from the Niẓamiyya. But in fact, this event was really only important for him. One can easily read and understand al-Ghazali’s works from the later stage of his life, without ever having to encounter any of his works that he had written earlier. His most famous book, the Iḥyāʾ ʿulūm al-dīn, or The revival of Islamic knowledge, as I like to translate is a extremely important in its own right.
Al-Ghazali, however, wrote many other influential books in other fields. One such field is that of philosophy; he wrote quite a few works on philosophy, the most important being the Tahāfut al-falāsifa (Incoherence of the Philosophers). No one studying Islamic/Arabic/Muslim philosophy or even medieval philosophy can afford to ignore this book. He also wrote on metaphysics, ethics, logic, and even on logic in legal theory.
In other fields, such as fiqh (jurisprudence), he wrote al-Wajīz, an important manual of Shāfiʿī fiqh. This book became the standard work in the field, as did his work on legal theory, al-Musṭaṣfa—one of five major books in the field.
Anyone reading any of his books gets the impression that he is not only the de facto expert, but that it was his only speciality. Al-Maraghi, the late rector of al-Azhar University, said quite succinctly when that one thinks of al-Ghazali one conjures up an image of many different personalities. Al-Ghazali the philosopher/theologian, the jurisprudent, the legal theorist, or the Sufi. He was all of these and more.
If that was all there is to al-Ghazali, one would stop here. However there is more. He has a very interesting life story. He came from a humble background and it was through his hard work and genius that he was able to achieve fame and renown beyond his wildest dreams. Now, 900 years after his death, we are still talking about him, his legacy, and his works.