And then there's the Jewish position regarding prophecies in the Old Testament about the Messiah. Jews say that Jesus did not in any way meet the requirements for being the Messiah. Their position is that the prophecies which were applied to Jesus were maligned, taken out of context, misapplied, etc., etc. They are still waiting for the Messiah based on their interpretation of messianic passages in what Christians call the Old Testament. Jew in effect are contending for "the faith once delivered", although they would not use that term. Christians, on the other hand, look at the same Old Testament passages and are convinced that they picture Jesus as the Son of God who died and was resurrected for the sins of mankind.
So in the final analysis it's all really a matter of faith and religious tradition, isn't it? How do you prove in a modern, scholarly manner what doctrines are correct and what are in error? The Bible has come down to us over thousands of years in different languages and multiple translations, and it is all too ambiguous to definitively prove doctrines, although there's no shortage of folks who say they do just that. But in the end, we are left only with faith.
We're also left with something else: the golden rule, a teaching about which there is no ambiguity. Simply treat others as you would wish to be treated. If every human being did that, the world would be just fine.