In several years of debating atheism and theism, I have made an observation. Ask any believer what would convince him he was mistaken and persuade him to leave his religion and become an atheist, and if you get a response, it will almost invariably be, "Nothing - I have faith in my god." Although such people may well exist, I personally have yet to meet a theist who would acknowledge even the possibility that his belief was in error. Many theists, by their own admission, structure their beliefs so that no evidence could possibly disprove them. In short, they are closed-minded, and have been taught to be closed-minded.
In light of this, it is ironic that atheists are often accused of being the closed-minded ones. Fundamentalist very frequently claim that we have hardened hearts, we are dogmatic and irrational, and that we reject God based on preconceived bias. Such claims result from psychological projection. Incapable of coping with the fact that there are some people who genuinely do not believe in their god, these theists simply deny that such people exist, and instead insist that everyone thinks the same way they do. Therefore, people who reach different conclusions than them must have some secret ulterior motive for not believing. This is truly ridiculous, but unfortunately, some people really believe it.
Thus, in the spirit of proving that the atheist's mind is not closed, I've assembled a list of what I would accept as proof that a given religion is true. Also included are things that I would accept as circumstantial evidence of a particular religion's truth and things that would not be acceptable to me as proof of anything. While I do not claim to speak for all atheists, I would confidently say that any religion that could produce one of the things from the first list would probably gain a great number of converts.
To be fair, I invite all theists to respond by preparing a list of things that they would accept as proof that atheism is true. If any theist prepares such a list please post it.
The first category deals with things that would absolutely convince me of the truth of a particular religion. If shown any of these, I would convert on the spot.
Verified, specific prophecies that could not have been contrived.
If the prophecy is vague, unclear or garbled (like Nostradamus' ramblings, for example). It must be detailed, specific and unambiguous in its prediction and wording.
If the prophecy is trivial, anyone could predict that it will be cold next winter, or that this drought/plague/flood will eventually subside. The prophecy must predict something surprising, unlikely or unique.
If the prophecy is obviously contrived for other reasons, No official seer or court astrologer ever predicted that the king he worked for would be a brutal, evil tyrant who would ruin the country.
If the prophecy is self-fulfilling; i.e., if the mere fact of the prophecy's existence could cause people to make it come true, The Jewish people returned to their homeland in Israel just as the Bible said they would, but this isn't a genuine prediction - they did it because the Bible said they would. The predicted event can't be one that people could stage.
If the prophecy predicts an event that already happened and the writing of the prophecy itself can't be shown to have preceded the event.
If the prophecy predicts an event that already happened and the happening of that event can't be verified by independent evidence. For example, Christian apologists claim that Jesus fulfilled many Old Testament prophecies, but the authors of the New Testament obviously had access to those prophecies also; what would have prevented them from writing their story to conform to them? The extra-biblical evidence for the existence of Jesus is so scanty that it is impossible to disprove such a proposal.
And finally, if the prophecy is the lone success among a thousand failures, anyone can throw prophecies against a wall until one sticks. The book or other source from which it comes must have at least a decently good record on other predictions.
These conditions, are reasonable, and are only what would be expected of a true prophet with a genuine gift.
Scientific knowledge in holy books that was not available at the time.