We know more about the religion of the early Egyptians than about any other ancient religion. Its development can be traced back three or four thousand years; we can read its sacred texts, mythical narratives, hymns, rituals, and the Book of the Dead in the original, and we can ascertain its various ideas as to the nature of the divine powers and of future life. A great number of monuments have preserved for our inspection the pictures of divinities and representations of liturgic scenes, while numerous inscriptions and papyri enlighten us in regard to the sacerdotal organization of the principal temples. It would seem that the enormous quantity of documents of all kinds that have been deciphered in the course of nearly an entire century should have dispelled every uncertainty about the creed of ancient Egypt, and should have furnished exact information with regard to the sources and original character of the worship which the Greeks and the Romans borrowed from the subjects of the Ptolemies. And yet, this is not the case. While of the four great Oriental religions which were transplanted into the Occident, the religion of Isis and Serapis is the one whose relation to the ancient belief of the mother country we can establish with greatest accuracy, we know very little of its first form and of its nature before the imperial period, when it was held in high esteem. One fact, however, appears to be certain. The Egyptian worship that spread over the Greco-Roman world came from the Serapeum founded at Alexandria by Ptolemy Soter, somewhat in the manner of Judaism that emanated from the temple of Jerusalem. But the earliest history of that famous sanctuary is surrounded by such a thick growth of pious legends, that the most sagacious investigators have lost their way in it. Was Serapis of native origin, or was he imported from Sinope or Seleucia, or even from Babylon? Each of these opinions has found supporters very recently. Is his name derived from that of the Egyptian god Osiris-Apis, or from that of the Chaldean deity Sar-Apsi? Grammatici certant. Whichever solution we may adopt, one fact remains, namely, that Serapis and Osiris were either immediately identified or else were identical from the beginning. The divinity whose worship was started at Alexandria by Ptolemy was the god that ruled the dead and shared his immortality with them. He was fundamentally an Egyptian god, and the most popular of the deities of the Nile. Herodotus says that Isis and Osiris were revered by every inhabitant of the country, and their traditional holidays involved secret ceremonies whose sacred meaning the Greek writer dared not reveal. Recognizing their Osiris in Serapis, the Egyptians readily accepted the new cult. There was a tradition that a new dynasty should introduce a new god or give a sort of preeminence to the god of its own district. From time immemorial politics had changed the government of heaven when changing that of earth. Under the Ptolemies the Serapis of Alexandria naturally became one of the principal divinities of the country, just as the Ammon of Thebes had been the chief of the celestial hierarchy under the Pharaohs of that city, or as, under the sovereigns from Sais, the local Neith had the primacy. At the time of the Antonines there were forty-two Serapeums in Egypt.