The descendants of Ali, though almost universally devoid of the qualities of great leaders, possessed the persistence and devotion of martyrs, and their sufferings heightened the fanatical enthusiasm of their supporters. All attempts to recover the temporal power having proved vain, the Alides fell back upon the spiritual authority of the successive candidates of the holy family, whom they proclaimed to be the imams or spiritual leaders of the faithful. This doctrine of the imamate gradually acquired a more mystical meaning, supported by an allegorical interpretation of the _Koran_; and a mysterious influence was ascribed to the imam, who, though hidden from mortal eye, on account of the persecution of his enemies, would soon come forward publicly in the character of the ever-expected _mahdi_, sweep away the corruptions of the heretical caliphate, and revive the majesty of the pure lineage of the prophet. All Mahometans believe in a coming mahdi, a messiah, who shall restore right and prepare for the second advent of Mahomet and the tribunal of the last day; but the Shiahs turned the expectation to special account. They taught that the true Imam, though invisible to mortal sight, is ever living; they predicted the mahdi's speedy appearance, and kept their adherents on the alert to take up arms in his service. With a view to his coming they organized a pervasive conspiracy, instituted a secret society with carefully graduated stages of initiation, used the doctrines of all religions and sects as weapons in the propaganda, and sent missionaries throughout the provinces of Islam to increase the numbers of the initiates and pave the way for the great revolution. We see their partial success in the ravages of the Karmathians, who were the true parents of the Fatimites. The leaders and chief missionaries had really nothing in common with Mahometanism. Among themselves they were frankly atheists. Their objects were political, and they used religion in any form, and adapted it in all modes, to secure proselytes, to whom they imparted only so much of their doctrine as they were able to bear. These men were furnished with "an armory of proselytism" as perfect, perhaps, as any known to history: they had appeals to enthusiasm, and arguments for the reason, and "fuel for the fiercest passions of the people and times in which they moved." Their real aim was not religious or constructive, but pure nihilism. They used the claim of the family of Ali, not because they believed in any divine right or any caliphate, but because some flag had to be flourished in order to rouse the people.