We learn from Francis Legge in Forerunners and Rivals of Christianity (1964) that in the year 391 A.D., the chief seat of origin for the Alexandrian religion was laid to waste, and the religion itself perished after a successful reign of seven centuries. Legge writes, “The ecclesiastical writers say that this was followed by the conversion of several of the ‘Hellenists,’ adherents to the worship of Serapis and Isis, to Christianity… Is this the reason we find so many of the external usages of Isis-worship preserved, in or revived by, the Catholic Church? When one religion finally replaces another, it generally takes over from its predecessor much of its usages that seem harmless or praiseworthy.” Another example of this immersion of belief systems is seen with the worship of the Virgin as the Theotokos or Mother of God, which is introduced into the Catholic Church about the same time as the destruction of the Serapeum in Alexandria. It enabled the devotees of Isis to continue unchecked their worship of the mother goddess by merely changing the object of their adoration” (Legge).

The concept of the Supreme Being as a triune (three-fold) god was a very old one in Egypt. “Thus from one god I became three gods,” says Osiris in his description of his self-creation in a papyrus dated twelve years after the death of Alexander. The Trinitarian formulas set out in the Creeds of Nicaea and of St. Athanasius was familiar to those in the Alexandrian religion, but not to those brought up in the uncompromising monotheism of the Jews. The ideas in Christianity are much older doctrines in the most ancient of religions than most people realize.