"The Rise of Lay Religious Authority in 1970's Egypt: The Case of Dr. Mustafa Mahmud" examines Mahmud's rise to prominence in Egypt during this period of tumultuous religious and political debate. It argues that Mahmud's ascent as a prominent lay religious intellectual and critic of both Leftists and violent Islamists in Egypt during this period reveals larger changes in the influence of lay-trained intellectuals. Mahmud serves as a model of the way in which such intellectual draw both on previously "traditional" models of authority as well as the authority of the "modern" Sciences to make their case within a deregulated religious marketplace. This paper draws draws on anthropological scholarship on the construction of religious authority in analyzing the 27 books which Mustafa Mahmud published during this period. It first places him in a larger religious and historical context, tracing how the underlying premises of religious and secular authority developed in Egypt during the 20th century. In this vein, it examines how religious debate spread outside of al-Azhar, as well as the rise of the modern sciences as another important source of intellectual and social authority. It then examines how Mahmud fits into the larger trends of decentralization of religious authority by examining his claim to not only scientific authority but also traditional ideas of knowledge such as Sufi Ma'rifa as well as to traditional literary genres of the Ulama such as the Tafsir and the Sirra Nabawiyya. It finally examines how Mahmud's claims to religious authority based on Modern Science and Sufism manifested themselves in his engagement with the claims of Egyptian Leftists (both Marxist and Nasserist) and violent Islamists during the 1970's. In conclusion, I seek to illustrate both the importance and tenuous nature of lay religious authority during the 1970's by examining both Mustafa Mahmud's claim to such authority and the intellectual premises on which his indictment of Leftists and violent Islamists during this period pivoted. In doing so, I hope to contribute to the scholarly debate on lay and traditional religious authority in Egypt by explaining how lay religious authority, while challenging traditional forms of authority, ultimately recognizes their continued relevance.