According to William Montgomery Watt, Al-Ghazali considered himself to be the Mujaddid (Revivier) of his age. Many, perhaps most, later Muslims concurred and according to Watt, some have even considered him to be the greatest Muslim after the Prophet Muhammad.
As an example, the Islamic scholar al-Safadi states: “Muhammad ibn Muhammad ibn Muhammad ibn Ahmad, the Proof of Islam, Ornamont of the Faith, Abu Hamid al-Tusi (al-Ghazali) the Shafi'ite jurist, was in his later years without rival.” and the jurist, al-Yafi'i stated that:
Al-Ghazali wrote most of his works in Arabic and few in Persian. His most important Persian work is Kīmyāyé Sa'ādat' (The Alchemy of Happiness). It is al-Ghazali's own Persian version of Ihya'ul ulumuddin (The Revival of Religious Sciences) in Arabic, but a shorter work. It is one of the outstanding works of 11th-century-Persian literature. The book was published several times in Tehran by the edition of Hussain Khadev-jam, a renown Iranian scholar. It is translated to English, Arabic, Turkish, Urdu and other languages.
Al-Ghazali had mentioned the number of his works "more than 70", in one of his letters to Sultan Sanjar in the late years of his life. However, there are more than 400 books attributed to him today. Making a judgment on the number of his works and their attribution to al-Ghazali is a difficult step. Many western scholars such as William Montgomery Watt (The works attributed to Al-Ghazali), Maurice Bouyges (Essai de chronologie des oeuvres d'Al-Ghazali) and others prepared a list of his works along with their comments on each book.
Despite his declared reluctance to enter into theological discussions, al-Ghazâlî addresses in his Revival important philosophical problems related to human actions. In the 35th book on “Belief in Divine Unity and Trust in God” (Kitâb al-Tawhîd wa-l-tawakkul) he discusses the relationship between human actions and God's omnipotence as creator of the world. In this and other books of the Revival al-Ghazâlî teaches a strictly determinist position with regard to events in the universe. God creates and determines everything, including the actions of humans.
Soon after al-Ghazâlî had published his two refutations of falsafa and Ismâ’îlism he left his position at the Nizâmiyya madrasa in Baghdad. During this period he began writing what most Muslim scholars regard as his major work, The Revival of the Religious Sciences (Ihyâ’ ‘ulûm al-dîn). The voluminous Revival is a comprehensive guide to ethical behavior in the everyday life of Muslims. It is divided into four sections, each containing ten books.
In his attempt to define the boundaries of Islam al-Ghazâlî singles out a limited number of teachings that in his opinion overstep the borders. In a separate book, The Decisive Criterion for Distinguishing Islam from Clandestine Unbelief (Faysal al-tafriqa bayna l-Islâm wa-l-zandaqa) he clarifies that only teachings that violate certain “fundamental doctrines” (usûl al-‘aqâ’id) should be deemed unbelief and apostasy. These doctrines are limited to three: monotheism, Muhammad's prophecy, and the Qur’anic descriptions of life after death (al-Ghazâlî 1961, 195 = 2002, 112).
Al-Ghazâlî describes the Incoherence of the Philosophers as a “refutation” (radd) of the philosophical movement (Ghazâlî 1959a, 18 = 2000b, 61), and this has contributed to the erroneous assumption that he opposed Aristotelianism and rejected its teachings. His response to falsafa was far more complex and allowed him to adopt many of its teachings. The falâsifa are convinced, al-Ghazâlî complains at the beginning of the Incoherence, that their way of knowing by “demonstrative proof” (burhân) is superior to theological knowledge drawn from revelation and its rational interpretation.
After having already made a name for himself as a competent author of legal works, al-Ghazâlî published around 1095 a number of books where he addresses the challenges posed by falsafa and by the theology of the Ismâ’îlite Shiites. The movement of falsafa (from Greek: philosophía) resulted from the translation of Greek philosophical and scientific literature into Arabic from the 8th to the early 10th centuries. The Arabic philosophers (falâsifa) were heirs to the late-antique tradition of understanding the works of Aristotle in Neoplatonic terms.
Al-Ghazâlî (c.1056–1111) was one of the most prominent and influential philosophers, theologians, jurists, and mystics of Sunni Islam. He was active at a time when Sunni theology had just passed through its consolidation and entered a period of intense challenges from Shiite Ismâ’îlite theology and the Arabic tradition of Aristotelian philosophy (falsafa). Al-Ghazâlî understood the importance of falsafa and developed a complex response that rejected and condemned some of its teachings, while it also allowed him to accept and apply others.
Mawlana Fazil Karim's English Translation from the Urdu Translation
Ihya' 'Ulum al-Din
REVIVAL OF RELIGIOUS LEARNINGS