Scholars of Islamic history have long recognized the fascinating transition of Sufism from a loose set of distinct tendencies in the third/ninth centuries, to a self-conscious movement which, by the beginning of the sixth/twelfth century, had entered into the mainstream and began to pervade all levels of society. Many have sought to explain the developments in the interim between the third/ninth and sixth/twelfth centuries which resulted in the eventual popularization of Sufism by the end of that period. It is known that instrumental to this process was the rising prominence of the so-called awliyā’ Allāh (“Friends of God”) who before long, were primarily identified with masters of the Ṣūfī path. Given the integration of Sufism into mainstream Sunnī Islam, Sunnī theology came to adopt the miracles of the Friends as markers of sainthood (wilāyah). My project seeks a more comprehensive understanding of how this took place, and the challenges that presented against this development. To this end, this project explores the debates on the Friends and their miracles between two opposing camps, the emerging Sunnī-Ṣūfī majority in contradistinction to the Muʿtazilah. I adopt a combination of textual, source-critical, and contextual approaches to Sunnī and Muʿtazilī writings on sainthood from the third/ninth to the fifth/eleventh century and place these sources in conversation with one another to better understand the stakes involved. This project also highlights the discursive nature of the Islamic tradition, with Muslim writers dynamically acting and reacting to one another, and to their social environments, in their attempts to define the boundaries of Islamic thought. / Religion