This article examines several fatwās by the important Muslim reformer Muḥammad Rashīd Riḍā. It treats these fatwās as part of a broader Arabic debate on “materialism” at the end of the nineteenth and the beginning of the twentieth century. In this context, Riḍā's fatwās on materialism illustrate the changing nature of Islamic religious authority in this period, as new kinds of knowledge became available to new kinds of readers.