About Al Ghazzali:
Abū Ḥāmid Muḥammad ibn Muḥammad al-Ghazālī (/ɡæˈzɑːli/; Arabic: ابو حامد محمد ابن محمد الغزالي; c. 1058 – 18 December 1111), shortened as Al-Ghazali and known as Algazelus or Algazel to the Western medieval world, was a Muslim theologian, jurist, philosopher, and mystic of Persian descent.
Al-Ghazali has been referred to by some historians as the single most influential Muslim after the Islamic prophet Muhammad. Within Islamic civilization he is considered to be a Mujaddid or renewer of the faith, who, according to tradition, appears once every century to restore the faith of the community. His works were so highly acclaimed by his contemporaries that al-Ghazali was awarded the honorific title “Proof of Islam” (Hujjat al-Islam). Others have cited his opposition to certain strands of Islamic philosophy as a detriment to Islamic scientific progress. Besides his work that successfully changed the course of Islamic philosophy—the early Islamic Neoplatonism that developed on the grounds of Hellenistic philosophy, for example, was so successfully criticised by al-Ghazali that it never recovered—he also brought the orthodox Islam of his time in close contact with Sufism. It became increasingly possible for individuals to combine orthodox theology (kalam) and Sufism, while adherents of both camps developed a sense of mutual appreciation that made sweeping condemnation of one by the other increasingly problematic.
More at wikipedia.