Muhammad ibn 'Abd al-Wahhab (1703-1792) aroused great controversy in his lifetime. More than two centuries after his death, he still elicits strong views. For some he is the model of a pious religious activist who fought to establish a regime of Islamic godliness in the least promising of environments. For others, especially Muslims associated with mystic orders or who belong to the Shi'i branch of Islam, he is a hate figure. Few would contest that he shaped the Muslim world. For over 250 years the Wahhabi movement has rested on the twin pillars of a clear, compelling credo and an indissoluble alliance with temporal power. Absolutist, uncompromising theology and political and religious ambition combined to make it the dominant force in Arabia, turning its champions, the Al Sa'ud clan, from petty rulers of a mid-sized settlement into the guardians of Islam's Holy Places, disposing of the earth's greatest identified oil reserves. This thought-provoking and comprehensive biography, which charts the relationship between religious doctrine, political power, and events on the ground, uncovers the life and thoughts of the man who helped establish the first Saudi state and who began a dynastic alliance that continues to the present day.