This article, part of a Common Knowledge symposium on “the consequence of blur,” concerns the place of religion in the historical literature on Asia. It finds a minimalist approach to religion in the case of Buddhism and a maximalist approach in the case of Islam: historians of Asia have little to say about Buddhism, while they exaggerate the role of the Muslim religion. This problem is acute when treating historical circumstances in which Buddhism and Islam are involved in tandem. Although people of the two traditions interacted throughout Asia for more than a millennium, which would suggest that pluralism or something like it was operative, there is virtually no mention of the other in the religious corpus of either tradition. This essay recommends and demonstrates a historical approach more alert to the possibility that religious pluralism may best be found in the past by exploring examples of cross-religious interaction that were not religious but, simply, performed by religious people. The case examined here is of a Buddhist-Muslim interaction that changed the history of the world. The successful spread of Buddhism was tied to the technological prowess and especially the advanced hydrology of its followers, which enabled irrigation for crops, including above all cotton. The sudden “cotton boom” in ninth-century Iran, which enabled the subsequent Muslim takeover of the global cotton industry, was enabled by Buddhists who were fleeing economic collapse and political turmoil in northwest India. This transfer of technology and expertise took place even though Islam is (thought of as) fiercely resistant to alien religious influence. Religious pluralism appears to have been at work when creedal specifics were left blurry, vague, and unstipulated.