From the II Errancy Discussion List, 1-1-07:
This is like the ivory-billed woodpecker example that I gave in an earlier reply to McDonald. If I were claiming that the ivory-billed woodpecker is extinct and McDonald knew that specimens of this species had been discovered in Arkansas, he wouldn't hesitate to counter my claim by producing an ivory-billed woodpecker or at least pictures of the discovery. The easiest way to prove the existence of gods or angels or miracles, then, would be to produce one.
You just can't beat empiricism for reliability. It beats all to heck holy books, visions, and such like.