A Really Good Question

The only evidence for Christian claims of the divine authority of their beliefs is their willingness to believe that their claims are divinely authored. That's it - literally and figuratively. 

Other than people's willingness to believe it to the point of either feeding themselves to lions or burning others alive as "witches" and "heretics," there simply is no other evidence to support such a claim. Nor do Christians ever feel the need to offer any. Instead, they simply insist that everyone else prove them wrong. When people then offer arguments like the problem of evil, of why and "all powerful" and "all good" God allows evil to occur, Christians reflexively blame "free will" - which shifts the blame from the manufacturer to the machine while ignoring the pre-programmed settings of "the stain of original sin" that lead us to prefer offending God more than obeying God - and  decide such a point is completely irrelevant. For them, God even uses evil to advance his plans, which is obviously why he punished Jesus and left the Devil without a scratch - even if no one knows why He does. 

And that is the true magic that makes their "beliefs" so real to them  - the adamancy with which they, and others like them, hold their "beliefs" to be infallibly true, regardless of the fact it is a recipe for justifying every immorality imaginable in the name of such a God.  

How do you prove to a person that their choice to simply "believe" that their claims come from a God (or make any sense), however heartfelt such a desire, choice, and a "belief" may be, is in no way proof that the 'divine author' they imagine must therefore exist, or that, even if such a 'divine author' does exist in some way, shape, or form, that "He" ever authored such beliefs, let alone commanded anyone and everyone to "believe" them in order to save themselves from being roasted alive - in a hell such a "God" alone created -  for all eternity for failing to do so?

And this is the true miracle of religious claims - that the hypocrisy of religious claims are so simple it defies credulity. And that's the trick, that only puny secrets need protection, as Marshal McLuhan observed, for big secrets and big discoveries "are protected by public incredulity." As a result, it's far easier to believe every other claim made by "believers" than to accept that the entire 2000 year old edifice of Christianity itself is built on a cornerstone of double standards masquerading as "infallible truth."

What makes it nearly impossible to pull back the curtain on such a simple yet bold faced double standard is the fact that it comes packaged in the Trojan horse of a person’s emotional need to believe it. Like yawning, the conviction a person develops for such a belief comes largely from the dedication (i.e., the need) others have to those same convictions. This is why Christians so often offer martyrs - "no one would simply die for a story that wasn't true, would they?" - as evidence for the truth of Christian claims, even as those very same Christians simply dismiss the martyrs for all other claims, including those like Hyapatia of Alexandria and Giordano Bruno, who died at the hands of Christians as martyrs for science while defending the claim that scientific investigation was a more reliable source of objective truth than faith in religious dogmas which were used to support slavery and burn witches.

 Hence, the true face of Christian claims to divine truth are really a trinity of hypocrisy. The father is the double standard itself, in which Christians boast of how their faith is so strong it needs no evidence to support it, even as they then use "miracles" as evidence to support a "faith" which they insist needs no evidence. The son of such a double standard is to always and everywhere deny that such a double standard is being exclusively relied on because, while Christians require that everyone else has the obligation to offer evidence that disproves their beliefs, Christians likewise require that anyone else who makes the very same claims that Christians make must offer evidence to substantiate their own brand of "faith" claims. (No wonder there are over 42,000 different brands of Christianity!)  

And lastly, the holy spirit  of such a double standard is the fanaticism that such a double standard not only necessitates but is then used as the only evidence there is that such "beliefs" are not only true, but infallibly so. That's why my brother, a Roman Catholic priest, loves to minimize everyone else's beliefs as "just a belief," even as he insists that his own brand of belief is not "just a belief," because it is infallibly true. 

His evidence, of course, is his conviction, which led him to become a Catholic priest in the first place. And he knows this because, at least for him, there's simply no other way of explaining why he believes it so much (at least, not that he would ever be willing to accept anyway). Tell him that a person who is convinced they are Napoleon Bonaparte suffers from the same problem, however, and he cannot help but feel like his "faith" is being attacked - because, let's face it: it is! In short, what proves to him his Catholicism is infallible truth is his own fanaticism for his Catholicism! Yet far from being evidence of anything as true, fanaticism is always a sign of repressed doubt, as Carl Jung pointed out, even when that fanaticism is for skepticism about the Christian claims as being divinely authored by a God. 

The difference is that the skeptic can see how the Christian claims are possibly true, even if the chance of being so are less than one's chance of winning the lottery, while each one of the more than 42,000 different brands of Christianity all equally insist they have won such a lottery,  even as they insist that all of the other 42,000 plus brands of Christianity are as deluded and mistaken as anyone who is convinced they are Napoleon Bonaparte. And what proof does each Christian offer to substantiate their claims to have been granted special access to divine truths about the universe, even more so than the other 42,000 claims? Well, the conviction with which they insist their "beliefs" are true, for why else would they be so willing to feed themselves to lions and burns their neighbors as "witches" and heretics, if their beliefs weren't infallibly true? 

Which is a really good question.