Abu Hamid al-Ghazali (1058–1111) was a philosopher, theologian, jurist, and Sufi mystic. Born in the Middle Eastern region of Khurisan (or Khorasan), and educated in the intellectual center of Nishaur, he became head of Nizamiyah, a seminary in Baghdad, where his teachings in law and theology were renowned. He sought certainty in knowledge, and when he could not find it in his academic studies he resigned his academic post, left his family, and became a Sufi mystic. He wandered for a decade and, as the result of those experiences, returned to Nishapur to resume teaching.

Al-Ghazali came to believe that truth can be found only as the result of God’s grace. In Deliverance from Error, his spiritual autobiography, he related his futile quest for truth and certainty through both Islamic and Western intellectual traditions and concluded that sensory information and reason were just as lacking. His alternative to rational and sensory knowledge was “a light which God Most High cast into my breast … the key to most knowledge.”

His attack on philosophical authorities as a guide to truth and certainty, particularly in the writings of Avicenna (980–1037), culminated in The Intensions of the Philosophers. And in The Incoherence of the Philosophers he offered a detailed intellectual attack on the views of Plato and Aristotle, which was again directed against Avicenna.