The question of the decline in Arabic science and the rise of the West has a long and storied history. In this article, I count manuscripts by author over time in different subject areas with newly digitalized data from Kashf al-Zanūn, a 17th century book catalogue written by Kâtip Çelebi, as well as the Islamic manuscript collections of over 2,500 libraries. The results of my linear and generalized differences-in-differences analysis are consistent with the Sunni Revival thesis, which argues that the political empowerment of Abbasid and Seljuk religious élite in the 11th and 12th centuries facilitated the spread of madrasa institutions, professionalized the ‘ulamā class of religious scholars, and channeled talent and state patronage away from empirical sciences. I argue however that the medieval decline did not occur in the context of the ‘ulema’s opposition to science as part of a nakedly reactionary ideology nor was the madrassa college the unique institutional vehicle for the decline of science. The process involved, rather, the acceptance and assimilation of scientific research into the heart of religious, scholastic life. These findings cast doubt on narratives that attribute intellectual stagnation in the Islamic world to the Mongol, Spanish, and Crusader invasions, the Black Death, the Medieval Climate Anomaly, or modern European colonialism.