This talk recasts the classic debate on the closure of the gates of ijtihād as the closure or end of a culture of critical Islam. By critical Islam, I mean a legal culture in Iraq and Persia in which continual re-examination of legal proofs across space and time was necessary to the juristic craft. My talk shows this critical culture was undercut within the Shāfi‘ī school by the emergence of a new conception of decaying time among 13^thcentury Mamluk jurists. This new conception of time forced a semantic change in the foundational concepts underlying the culture of critical Islam—ijtihād, madhhab, taqlīd, qiyās,and sharī‘a, spelling the end of critical debate among Shāfi‘īs.