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:
“He was called The Proof of Islam and undoubtedly was worthy of the name, absolutely trustworthy (in respect of the Faith) How many an epitome (has he given) us setting forth the basic principles of religion : how much that was repetitive has he summarised, and epitomised what was lengthy. How many a simple explanation has he given us of what was hard to fathom, with brief elucidation and clear solution of knotty problems. He used moderation, being quiet but decisive in silencing an adversary, though his words were like a sharp sword-thrust in refuting a slanderer and protecting the high-road of guidance.”The Shafi'i jurist al-Subki stated that "If there had been a prophet after Muhammad, al-Ghazali would have been the man". Praise for al-Ghazali not withstanding, he also received criticism from within Islam: Ibn Taymiyyah states: “If we assume that someone narrated the view of the salaf but what he narrated is far removed from what the view of the salaf actually is, then he has little knowledge of the view of the salaf, such as Abu’l-Ma’aali, Abu Hamid al-Ghazali, Ibn al-Khateeb and the like, who did not have enough knowledge of hadith to qualify them as ordinary scholars of hadith, let alone as prominent scholars in that field. For none of these people had any knowledge of al-Bukhari and Muslim and their hadiths, apart from what they heard, which is similar to the situation of the ordinary Muslim, who cannot distinguish between a hadith which is regarded as sahih and mutawatir according to the scholars of hadith, and a hadith which is fabricated and false. Their books bear witness to that, for they contain strange things and most of these scholars of ‘ilm al-kalam (science of kalam) and Sufis who have drifted away from the path of the salaf admit that, either at the time of death or before death. There are many such well-known stories. This Abu Hamid al-Ghazali, despite his brilliance, his devotion to Allah, his knowledge of kalam and philosophy, his asceticism and spiritual practices and his Sufism, ended up in a state of confusion and resorted to the path of those who claim to find out things through dreams and spiritual methods.
Ibn Rushd (Averroes), a rationalist, famously responded that "to say that philosophers are incoherent is itself to make an incoherent statement."[citation needed] Rushd's book, The Incoherence of the Incoherence, attempted to refute al-Ghazali's views, though the work was not well received in the Muslim community.