Voices resistant to theological change have created a make-believe dualism meant to protect " (evangelical) orthodoxy" from outside contamination. This is the false dichotomy of "contextualization" vs. "syncretism." The success of this fantasy isn't really all that surprising. Evangelicals have noticed how important it is to relate to the culture in which they find themselves. Yet, they want to find a way to protect their eternal message from enduring the pressure of the cultural realities from invading their pristine chapels. They want to communicate the(ir version of) the gospel in a relevant way to convert and fill the pews. But they also want to feel justified in sticking their fingers in their ears and saying "lalalalala" in order to keep information from the culture out. In short, they want one-way communication. It's safe and clean. (While this may not be the stance of all evangelicals, it does seem to be the most dominant stance.)
The propagan... er, argument asserts that contextualization is good and syncretism is bad. Contextualization is taking cultural forms and filling them with evangelical meaning. So, The Passion of the Christ is good because it takes the form of a movie and uses it to communicate the message. Syncretism, on the other hand, allows not only form but meanings to mingle. Since this would contaminate the message, we can see how scary this is to evangelicals.
Theologian Kosuke Koyama pointed out the blatantly obvious more than 10 years ago when he said, "Condemning syncretism is like condemning the air one breathes. Nothing in history is pure and isolated. For the human mind, there is no choice but to meet, converse and syncretize. What a vast reality of syncretism is Christianity in the United States!" Though I realize how appealing the false dichotomy is to those who feel a need to stay pure, the resistance to basic reason sometimes baffles me. Even more interesting is the willingness to bury one's head in the sand and pretend reality isn't happening.
The reality I'm talking about here is the make-up of the central symbols of Christianity itself. And yet, strangely enough, as we explore them we see how the earliest Christians engaged in a healthy (well, that may be debatable) form of syncretism.
Baptism has its roots in primarily in Judaism, though its significance is best understood in light of baptism in the mystery religions. Generally speaking, from what we can tell, mystery religions viewed the worlds populace as belonging to one of two categories: the pure and impure. When joining a cult, one would first purify one's self, then undergo baptism as a rite of entry into the pure community. So it was purification, baptism, then participation in the pure community. Jewish baptism was an act of purification that happened inside the community. The community by definition was not pure but being purified. Christian baptism seems to have taken on the role of baptism in a mystery religion (a gateway into the community, the role also played by Jewish circumcision), and it filled it with the communal theology of Judaism. The separation of humanity into the pure and impure was liturgically rejected. Through the act of liturgical syncretism, early Christians took a stand on the nature of humanity. (For more on baptism, see the works of Wayne A. Meeks. Unfortunately, my books are in storage, so no citations today.)
The Lord's Supper (or Eucharist, or Communion) actually seems to draw more from a mystery sacrifice than it does the Jewish Passover. In basic mystery religion lore, a god (or son of a god) comes down to earth to teach humanity how it's done. Humanity, however, doesn't like this. So they unjustly persecute and kill the (son of a) god. In a grand reversal of the injustice, the god resurrects his son (or the god resurrects himself), thus the truth is vindicated. Those who would follow the god's teachings join the cult. One such cult was the cult of Mithras in which (if I recall correctly) the eating of the flesh of the sacrificial bull and drinking its blood empowered a participant to partake of the eternal life of the risen god. From the Jewish influence, it appears that the use of Passover imagery primarily served to identify which deity is setting the table. By injecting this hint of Passover theology into the rite, early Christians were able to claim the ritual and its mystery theology as their own.
We see syncretism written into the texts of faith early in the gospel of Matthew. According to the Zoroastrian religion, our world is the battleground between two gods, one of light and one of darkness. The human calling is to choose a side (and not choosing defaults you to the god of darkness). Their religion taught that one day, the god of light would send a divine emissary to lead the followers of light to victory over the darkness. The arrival of that emissary would be heralded by the appearance of a star. A task of the Zoroastrian priests was to watch for this star. Zoroastrian priests were also called magi. Thus, we see in the beginning of the gospel of Matthew a rubber stamp placed on the beliefs of the Zoroastrians. And in the gospel's dualism between light and dark, we see the incorporation of their religious dualism into the narrative itself. The textual evidence right up front, then, seems to indicate that the dualism prevalent in Matthew is drawn more from the Zoroastrian narratives than it is from Jewish fringe groups.
Then, we have the story of Jesus himself. I have to wonder, to what extend did the story of Socrates influence the recordings of the story of Jesus? Is the Holy Spirit of Jesus a rip off of Socrates' divine voice? Both were portrayed as men of strong character and amazing teachers. Both enjoyed a final meal with their friends. Is Jesus a literary parallel to Socrates? Or was the story a Jesus an attempt to overturn the story of Socrates (as the story of Jesus is clearly meant to overturn the story of the Emperor)? Socrates was educated from birth, but Jesus was not; perhaps the writers were trying to show their poor communities that wisdom comes from God and not classical education, so they need not feel inferior to their social superiors. I have not looked into this much, but I suspect we would find that the story of Socrates was partly written into Jesus' story in order to make a point. That, too, is a form of syncretism. (An old but interesting source to read might be Joseph Priestly, Socrates and Jesus Compared, 1803.)
So, if anyone really wants to proclaim that Christianity must protect itself from syncretism, then those people have some serious house-cleaning to do. They need to rid their theology (at least) of baptism, the Lord's Supper, the gospels, and (since the gospels are our foundation for what we know about him) Jesus himself. If their not willing to do that, they shouldn't expect me (or any other reasonable person) to take them seriously.