Al-Ghazālī's Radical Skepticism Preceded Descartes by Five Centuries

In 11th-century Persia, the Islamic philosopher Al-Ghazālī underwent a profound crisis of doubt that anticipated René Descartes' methodical skepticism by 500 years. By 1095 CE, Al-Ghazālī was head of the Niẓāmiyya Madrasa in Baghdad, at the height of his career within the Great Seljuk Empire. He became convinced his studies were futile, suffered a psychosomatic breakdown, and lost the ability to speak. His skeptical arguments, recorded in al-Munqidh min al-Ḍalāl (Deliverance from Error), questioned inherited beliefs, sensory perception, and even reason itself. He proposed a dream argument—that conscious experience might be a dream—and considered the possibility of a deceptive deity, allowing him to doubt even mathematical certainties. Descartes later employed nearly identical reasoning in his Meditations, including the fallibility of the senses, the dream argument, and the hypothesis of an evil deceiver. Both thinkers ultimately relied on God to restore certainty: Descartes through the Cogito and proofs of a non-deceiving God, Al-Ghazālī through divine light imparted into his heart. Al-Ghazālī's Aims of the Philosophers was translated into Latin in the late 12th century; he was known to Dante, who mentioned him in Il Convivio. His works were studied by Jewish and Scholastic philosophers. The striking parallels between Meditationes de Prima Philosophia and al-Munqidh min al-Ḍalāl remain a subject of historical debate.