This book examines the role of Muhammad Ibn 'Abd al-Wahhab (1703-1792) and his successors in reconsolidating the religious principles of Wahhabism. It explains the role of the Sa'udi princes in crystallizing the core of the Sa'udi-Wahhabi political entity within their tribal society. Key to this explanation is the interrelation between sedentary and nomadic populations and the consequent impact on the development of Saudi political entities prior to the emergence of the Sa'udi Kingdom. Texts of Wahhabi scholars are compared with those of the early Hanbali scholars, pinpointing the new religious elements introduced to foster the Wahhabi creed. Discussion focuses on the first and second generations of Wahhabi scholars who maintained the Wahhabi creed with great success, keeping its hegemony as the main doctrine in Sa'udi Arabia, and developing a takfiri discourse (accusing people of being infidels) which by the nineteenth century had become the main religious and political weapon by which the Wahhabis mobilized supporters against their political and religious adversaries. To better understand this development, the meaning of kufr (heresy) in Islam and its implications in various Islamic doctrines is examined closely. The focus on the role of Wahhabi scholars in the nineteenth century sheds new lights on the principles of continuity and discontinuity in the historical development of Sa'udi political entities and explains the origin of the modern Sa'udi State. Although major socio-economic and cultural change is now taking place under the leadership of Prince Muhammad ibn Salman, the main religious structures of the state remain firmly in place. It remains to be seen how two diametric societal viewpoints will integrate or clash. This work is essential reading for all scholars and students of religious, cultural, social and political history of Sa'udi Arabia and Islam in the Middle East.