For more than a century, liberal critics of the Christian faith have been claiming that early Christianity was heavily influenced by Platonism, Stoicism, pagan mystery religions, or other movements in the world at that time. A series of scholarly books and articles had refuted most of these claims by the 1940s. But new generations of liberal scholars have revived many of these older discredited positions.
The favorite target among the four Gospels has been the Gospel of John. John 1:1-18 was supposedly influenced by a Jewish philosopher named Philo who lived in Alexandria, Egypt. Rudolf Bultmann made a career of claiming that parts of John's Gospel were influenced by Gnosticism and/or various mystery religions. Such influences allegedly extended to the Apostle Paul as well.
All Christians should ask the following questions of all claims about any alleged dependence of early Christianity upon pagan sources:
(1) What is the evidence for such claims?
(2) What are the dates for the evidence? An embarrassingly high percentage of the alleged evidence turns out to be dated long after the writing of the NT.
(3) Are the alleged parallels really similar, or are the likenesses a result of exaggeration, oversimplification, inattention to detail, or the use of Christian language in the description?
(4) Is the alleged parallel between the NT and a supposed pagan source the sort of thing that could have arisen independently in several different movements?
(5) the claim of influence or dependence consistent with the historical information we have about the first-century church?
Extracted from the Apologetics Study Bible.