Expose yourself to the best of the other side, and see if it changes your mind. See religion at its best, at its most intelligent, and ask yourself what you think then.
I'm going to admit laziness early, and acknowledge that possibly you or someone else has something specific in mind. What would you [or any outside observer] consider reading to see that?
Edit: This also tempts me to build a time machine and ask my past self with whom I feel very disjointed from why he still holds onto his faith, or to grab myself during the transition and watch it happen again. Not to say I was religion at it's best, but I could see what convinced me better... alas, such is not the case :P
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