Recently, I heard a liberal theologian (Dr. Robert Price) say that the Christian religion is built on fables, mystery religions, and ultimately born out of syncretism. According to him, a Christ that is born of a virgin, dies and rises, ascends to the right hand of the Father, and saves the cosmos is the most natural thing in the world. He also adds to his argument that novels had been written in the 600BC, and the NT was the pinnacle of these writings.
Specifics aside, (when people say things like this they stretch the evidence way too far), in my experience, syncretism is born out of a compromise for a peace and unity where there is no peace and unity. But Jesus is totally the opposite! In the Gospel, Jesus doesn't come to bring peace, but a sword, to divide people. That doesn't sound like syncretism at all. Furthermore, if it was a syncretistic movement, why a new religion that refuses to worship in the pantheon, undermines Cesar's ultimate authority, suffers intense persecution, and yet gives to Cesar what is Cesar's. It doesn't make any sense. As a Lutheran, this doctrine of the two Kingdoms blows me away. You have this almost-pacifism that doesn't give a crap who Cesar is, and yet suffers at his hands gladly. Christianity never tries to overthrow the state, whether by force or patience. That is the Lord's job at his reappearing. Although, I do find it ironic that Christianity did win the day centuries later. I highly doubt that the early Christians would have foreseen this in any way.
Sure, there are other religions out there who passively suffer for their faith, but I highly suspect any truth to a story about a gaggle of Jews willing to die for a fable to make some greater point in government. Both of these groups, Jews and Gentiles, wanted to make power grabs. Jesus says his kingdom is not of this world. I think people actually believed that and this is the reason for all the martyrdom that has gone on.
But what is also really funny, is that Dr. Price claims much of the New Testament is forgery, and filled with all sorts of interpolations. But this first-last and last-first mindset is permeated in all of the Gospels and Epistles through and through. If you take out all of the so called "interpolations" you have nothing in the Bible left, nothing significant at all, and no reason why anyone would want to be a Christian. It's amazing how much the New Testament itself works as evidence to outsiders. It stands alone as a great independent source, and you don't even have to presuppose divine inspiration/ inerrancy. How great is the strength we have in our weakness!
BTW, I would be curious to investigate what other mystery religions confessed of government. That said, Liberal theology makes absolutely no sense to me.