One hundred and eighty years of egyptological scholarship has failed to establish why and how the ancient Egyptian religion could be surmounted by Christianity. In recent decades scholars have attributed Christianity's triumph to Christian revelation, the moral superiority of Christianity, its more thoroughly social sensibility, monotheism, its domination over the heimarmene, etc. The riddle is intensified if we consider that by the time of the decay of the autochthonous Egyptian religion in the home country, the so-called Isis religion was victorious in other provinces of the Imperium Romanum. The present paper argues that the two religions represent two different types, the Egyptian one being an ethnic religion, Christianity being a universal one. Consequently, the Egyptian religion had no need of soteria, while Christianity was born in a situation of "Unheil". During the last millennium of the pharaonic history the crisis of the traditional religion became more and more serious, because the cleft between cult and the native culture supporting this cult became too deep. This conclusion is supported by the decline of the hieroglyphic and demotic scripture, the disappearing of the characteristic Egyptian art and the profound change in the anthropological understanding of human being, which might have required the soteriology of a new religion.