Much is obscure in their history, even though hypothesis be given the widest range and a friendly hearing. The central problem, which still requires much further attention than it has as yet received, is how and when these religions became mystery cults. As we know them in the Roman Empire all have the same central feature of offering personal salvation to their adherents through sacraments. But did they have this characteristic in their original homes, where they were national religions? The evidence that they did so is not convincing, and perhaps cannot be, because of the absence of literary sources. For instance, one of the best known of these religions is the cult of Isis, for the nature of which in the second and third centuries there is admirable evidence in the writings of Plutarch and Apuleius. It was then clearly a sacramental religion offering private salvation. It was also connected with a myth which was obviously a hindrance rather than a help to these educated Romans, and this myth can be traced back to the monuments of ancient {5} Egypt. Are we justified in concluding that the interpretation in ancient Egypt was the same as in imperial Rome? It may be so; but it is possible that the sacramental nature, though not the element of private salvation came in, in Hellenistic or in Imperial times, to meet the necessity of Egyptians who had lost all sense of belonging to a living nation or having a national religion, and of Greeks who with decadent enthusiasm desired imported rites. In any case, a synthesis was rapidly established between these cults and the official Graeco-Roman religion. The names of the Oriental deities were Hellenised, and the barbaric crudities of the East were removed by allegory and symbolism; the philosophers felt that the myths only needed restatement to confirm their opinions, while the priests were confident that the elements of truth in philosophy were those revealed by the language and ritual of the cults.[1] With considerable rapidity, therefore, Greek mythology, Greek philosophy, and Oriental cults were being accommodated to one another, and brought together in a new and highly complex religious system. For political purposes the introduction into this system of the worship of the emperors, living or dead, was of great importance. It tended to unify the whole mass, and the imperial authorities adopted the {6} position, with some reservations, that, provided a man accepted the cult of Caesar and Rome, he could in addition be a member of any other religion which pleased his fancy or soothed his soul.