This is relevant, not just to Elvis appearing, but to New Age stuff. I have quite a few friends who are into astrology, Tarot, the I Ching, and so on. I'm not interested in it myself, but if I wanted to investigate it, how would I do it non-rationally?
I mean, one could make guesses, or sort of enjoy oneself getting drunk, throwing Tarot cards around, or whatever, but none of that would really tell me if Tarot offers genuine insights or not.
Of course, one could also set up experiments which match predictions with outcomes - this seems fairly rational. How else?