Abū Ḥāmed Muḥammad ibn Muḥammad Ghazālī (1058–19 December 1111) (Persian/Arabic:ابو حامد محمد ابن محمد غزالی), often Algazel in English, was an Islamic theologian, jurist, philosopher, cosmologist, psychologist and Sufi mystic of Persian origin, and remains one of the most celebrated scholars in the history of Sunni Islamic thought. He is considered a pioneer of methodic doubt and skepticism, and in one of his major works, The Incoherence of the Philosophers, he changed the course of early Islamic philosophy, shifting it away from an Islamic metaphysics towards an Islamic philosophy based on cause-and-effect that was determined by God or intermediate angels, a theory now known as occasionalism. He was born in Tus, a part of the Khorasan province of Persia. He died there as well.
Ghazali has sometimes been referred to by historians as the single most influential Muslim after the Prophet Muhammad. Besides his work that successfully changed the course of Islamic philosophy—the early Islamic Neoplatonism developed on the grounds of Hellenistic philosophy, for example, was so successfully refuted by Ghazali that it never recovered—he also brought the orthodox Islam of his time in close contact with Sufism. The orthodox theologians still went their own way, and so did the mystics, but both developed a sense of mutual appreciation which ensured that no sweeping condemnation could be made by one for the practices of the other.
Ghazali contributed significantly to the development of a systematic view of Sufism and its integration and acceptance in mainstream Islam. He was a scholar of Sunni Islam, belonging to the Shafi'i school of Islamic jurisprudence and to the Asharite school of theology. Ghazali received many titles such as Sharaful A'emma (Arabic: شرف الأئمّة), Zainuddin (Arabic: زين الدين), Hujjatul Islam, meaning "Proof of Islam" (Arabic: حجّة الاسلام). He is viewed as the key member of the influential Asharite school of early Muslim philosophy and the most important refuter of Mutazilites. However, he chose a slightly different position in comparison with the Asharites; his beliefs and thoughts differ, in some aspects, from the Asharite school.
Ghazali was born in 1058 in Tus, a city in Khorasan province of Persia. His father, a traditional Sufi, died when he and his younger brother, Ahmad Ghazali, were still young. One of their father's friends took care of them for the next few years. In 1070, Ghazali and his brother went to Gurgan to enroll in a madrassah (Islamic seminary). There, he studied fiqh (Islamic jurisprudence) next to Ahmad ibn Muhammad Rādkānī and Abu'l Qāsim Jurjānī. After studying for approximately 7 years in the seminary, he returned to Tus.
His first important trip to Nishapur occurred around 1080 when he was almost 23 years old. He became the student of the famous Muslim scholar Abu'l Ma'ālī Juwaynī, known as Imam al-Haramayn. After the death of Al-Juwayni in 1085, Ghazālī was invited to go to the court of Nizamul Mulk Tusi, the powerful vizier of the Seljuq sultans. The vizier was so impressed by Ghazali's scholarship that in 1091 he appointed him as chief professor at the Al-Nizamiyya of Baghdad. He used to lecture to more than 300 students, and his participation in Islamic debates and discussions made him popular in all over the Islamic territories.
He passed through a spiritual crisis in 1095, abandoned his career, and left Baghdad on the pretext of going on pilgrimage to Mecca. Making arrangements for his family, he disposed of his wealth and adopted the life of a poor Sufi. After some time in Damascus and Jerusalem, with a visit to Medina and Mecca in 1096, he settled in Tus to spend the next several years in seclusion. He ended his seclusion for a short lecturing period at the Nizamiyyah of Nishapur in 1106. Later he returned to Tus where he remained until his death on December 19, 1111. He had one son named Abdu'l Rahman Allam.
Ghazali wrote more than 70 books on the sciences, early Islamic philosophy, Islamic psychology, Kalam and Sufism. His 11th century book titled The Incoherence of the Philosophers marks a major turn in Islamic epistemology, as Ghazali effectively discovered philosophical skepticism that would not be commonly seen in the West until René Descartes, George Berkeley and David Hume. The encounter with skepticism led Ghazali to embrace a form of theological occasionalism, or the belief that all causal events and interactions are not the product of material conjunctions but rather the immediate and present will of God.