The Persians, after being conquered by the Arabs, were compelled to adopt the Muhammedan religion, but they preserved a secret adherence to Magism, their ancient national creed, they were therefore easily disposed to join any sect, which was more or less contrary to the standard creed of their conquerors, and bore some slight conformity, or had the least connection with, their former religion. They became Shiâhs. Among these sectaries originated the particular office of _Imám_, whose power partook of something of a mysterious nature: the visible presence of an Imám was not required; he could, although concealed, be acknowledged, direct and command his believers; his name was _Mahdi_, “the director.” This opinion originated and was spread after the sudden disappearance of the seventh Imám, called _Ismâil_. His followers, the Ismâilahs, maintained that he was not dead; that he lived concealed, and directed the faithful by messages, sent by him, and brought by his deputies; that he would one day reappear, give the victory to his adherents over all other sects, and unite the world in one religion. More than one Mahdi was subsequently proclaimed in different parts of Asia, Africa, and Europe――always expected, never appearing――so that it became a proverbial expression among the Arabs to denote tardiness: “_as slow as a Mahdi_.” We recognize in this an ancient idea of Zoroaster: he too was to reappear in his sons at the end of 12,000 years; rather late,――but mankind never tire of hope and expectation. A creed, like that of the _Ismâilahs_, because founded upon something mysterious, vague, and spiritual, was likely to branch out in most extraordinary conceptions and practices. The Dabistán abounds with curious details about them. Their doctrine bore the character of duplicity: one part was manifest, the other concealed. Their manner of making proselytes was not open; they acted in the dark. They first induced the neophyte to doubt, then to despise his own creed, and at last to exchange it for apparently more sublime truths, until, after having sufficiently emboldened his reasoning faculty, they enabled him to throw off every restraint of authority in religious matters. We see in the Dabistán,[165] the degrees through which an Ismâilah was to pass until he believed in no religion at all.