The Islamic regime that came to power after the 1978-79 Iranian revolution justified the rule of the Ayatollah Khomeini, and the Shi'ite imams in general, on the basis of the doctrine that the Islamic jurist is best suited to rule with justice in an Islamic country. Arguing that this concept has no apparent parallel in Sunni Islam, this study explores its origins in the Sunni/Shi'ite schism, which took place after the death of the Prophet, and traces its evolution to the present day. Drawing on exhaustive research in the Islamic libraries of Iran and Jordan, as well as discussions with leading jurors and scholars in Iran, Sachedina presents the first in-depth analysis of an Islamic phenomenon of vital contemporary social and political significance.