Abu al-Hasan al-Ash'ari

Abu al-Hasan Ali ibn Ismail al-Ash'ari (260-324 AH / 874-936 CE) was born in Basra and spent his formative years as a leading figure within the Mutazili school of theology. At around age forty, he publicly abandoned Mutazilism in the Great Mosque of Basra, famously declaring his return to the creed of the pious predecessors. This dramatic reversal marked a turning point in the history of Islamic theology.

Al-Ash'ari used the rational tools of kalam (dialectical theology) to defend the positions of Ahl us-Sunnah against their opponents. His methodology provided a middle way between the pure textualism of the traditionists (ahl al-hadith) and the rationalism of the Mutazilah. His Maqalat al-Islamiyyin is an invaluable encyclopedia of theological positions held by various Muslim groups. His al-Ibanah an Usul ad-Diyanah explicitly affirms the creed of Imam Ahmad ibn Hanbal as his own.

The school that bears his name became the most widespread theological school in the Sunni world, adopted by the majority of Shafii and Maliki scholars. It was further developed by al-Baqillani, al-Juwayni, and al-Ghazali into a comprehensive theological system. Al-Ash'ari died in Baghdad in 324 AH (936 CE). His legacy in providing a systematic, rational defense of orthodox Sunni beliefs remains one of the most significant intellectual achievements in Islamic history.