“Well, Mr. Atheist Smarty Pants, you think you’re so open minded. Prove it. Show me what would convince you to change your mind.” I recently challenged Christians to consider what it would take to convince them that their religious beliefs are wrong, and now it’s the atheists’ turn.
A good article on this question is The Theist’s Guide to Converting Atheists, written by fellow Patheos blogger Adam Lee of Daylight Atheism. I’ve used it here as a starting point for my own exploration on this question.
Convincing Traits
Here’s a tentative list of what would convince me of a religion’s claims (more on the tentative nature of the list below).

• Many occurrences that are widely accepted by the scientific establishment as miracles. And “Science can’t explain it” isn’t necessarily a miracle—it’s just something science can’t yet explain.
• Alternatively, a single crowdsourced miracle. On one day, everyone in the world sees “Yahweh exists” spelled out in stars or pebbles or lines in the sand. Or, one night, everyone has the same dream in which a god explains his plan. If either happened just to me, the obvious explanation would be that my mind (or someone) was playing tricks on me.
• Prophecies, but not the ones that Christians often point to. I mean real ones. I’ve discussed before the properties of a reasonable prophecy—it must be startling, precise, accurate, and so on.
• Scientific knowledge in holy books that wasn’t available at the time. The scientific knowledge in the Bible is no more advanced than would be expected from any non-divinely inspired book of that time. There’s no e = mc², no f = ma, no Big Bang, and no geocentric solar system. What’s really surprising is nothing to do with health: no “boil your drinking water,” no “dig latrines far from the water source,” and no recipe for soap.
• The believers would be changed in a way unexplainable by natural causes—good things would tend to happen to them more often than for nonbelievers, problems would be resolved quicker, prayers are answered, or in some other way we would see the deity assisting his people.

Necessary Traits of a Divinely Inspired Religion
These traits aren’t evidence for a religion, but they respond to arguments against. They are traits of a religion with a real deity behind.

• The holy book would be perfect—no errors, no ambiguities, no inconsistencies. Not much to ask from a perfect deity, right?
• As a corollary, there would be nothing in the holy book to which believers say, “I must admit that I can’t explain that. I guess I’ll just have to ask God when I get to heaven.” I’m thinking of puzzles like why God commanded genocide or allows famines. But how can a holy book contain this kind of problem? The holy book has no purpose except to explain to people here on earth what reality is and what the rules are.
• The religion would have no internal divisions or doctrinal conflicts. To take a Christian example, Docetism (the idea that Jesus only seemed to be a human) was put to rest only at the First Council of Nicaea in 325. Other heresies took centuries more to resolve. One could pretend that the various twists and turns taken by Christianity were divinely guided, but where is the evidence for that?
• It would not only celebrate reason, it would provide necessary evidence and wouldn’t require faith.

I wouldn’t add to this list that the god must be praiseworthy, judged by modern moral standards. The god might encourage genocide and allow slavery, but he doesn’t necessarily have to be good (the Gnostics imagined such a creator god).
Of course, you can cobble together rationalizations for religion without these properties—a religion where faith is required, where the holy book is ambiguous, where religion is split by doctrinal controversies, and so on, but don’t expect that to be a compelling argument.
Nonstarter Traits
Here’s a short list of general religious arguments that won’t get you out of the starting gate.

• Curious things with natural explanations like speaking in tongues or other ecstatic experiences
• Personal conversion stories or anything else that only you experienced
• Things that can be explained as coincidences
• And it should go without saying that anyone should be written off if they make a prophecy that fails (for starters, I’m thinking of Harold Camping).

Revisiting the List of Convincing Arguments
Let me return to the first list. I said that it was a tentative list because of Shermer’s Last Law: “Any sufficiently advanced extraterrestrial intelligence is indistinguishable from God.” How could I distinguish alien technology a million years more advanced than our own from the supernatural actions of a god? And if the aliens identified themselves, they might portray themselves as gods to get us to react in a certain way. Who knows—they might even be intergalactic practical jokers who just want to mess with us.
Given the choice of God or aliens as explanations, the aliens are more plausible because they’re intelligent life forms with technology. We already have an example: we are intelligent life forms with technology. By contrast, we have no commonly accepted examples of a supernatural anything.
So let me admit that, to the Christian’s challenge “What would it take to get you to believe in God?” it might be that no evidence would. But anything that would provoke Shermer’s Last Law would be a heckuva lot more evidence than we’ve had to date, where Christianity fades into the general background of thousands of manmade religions.
Hypocrisy?
Let’s pull back and consider two situations: (1) the atheist given substantial evidence of God’s existence (the present slate of arguments by Christian apologists doesn’t come close to being “substantial”) and (2) the Christian given substantial evidence that their faith is incorrect (discussed in a post a few days ago). I’m saying that the atheist would be reasonable in not changing to accept the supernatural, but reason compels the Christian to change and reject the supernatural.
Is this a double standard?
I don’t think so. In each case, the natural argument wins. The atheist goes with the natural explanation (it’s aliens, it’s a trick, I’m mistaken, I’m crazy, etc.), and the Christian also goes with the natural explanation by following the evidence. Science has shown us myriad examples where a natural explanation trumps a prior supernatural explanation, so it’s reasonable to bet on the natural explanation where it exists.
Perhaps the reason that Christianity isn’t compelling to many atheists is that they have no particular motivation (besides wanting to believe true things) to see it as correct. Is wanting it to be true a requirement for Christian belief?

Any sufficiently advanced technology
is indistinguishable from magic.
— Arthur C. Clarke

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