Demonstrating the central role of third/ninth century hadith scholars in the articulation of Sunni Islam, this book bases its findings largely upon the analysis of multiple biographical dictionaries, such as al-Dhahabi's Tadhkirat al-huffaz, Ibn Sa?d's Kitab al-tabaqat al-kabir, and collections of the critical comments of Ibn Ma?in and Ibn Hanbal.Part I establishes conceptual and historical frameworks for the study of Sunni hadith scholarship. Part II examines in detail the three foundational principles of Sunni Islam: 1) the collective probity of the sahaba, 2) the discipline of hadith-transmitter criticism, and 3) a historical vision of the authoritative channels by which hadith traversed the two centuries between the life of the Prophet Muhammad and the first major hadith books.