Any evidence? It seems foolish to ask what evidence would convince you when there is no evidence or reason at all to believe in a fairy Godfather.
Not at all. Scientists do this all the time. "If this theory were true, what evidence would we find to support it?" Only once you've identified what type of evidence would be relevant and compelling is it practical to look for it.
I may not believe in Bigfoot, but I can certainly imagine the sort of evidence that would change my mind, and I can figure out what kind of expedition is and is not likely to produce it. A mountain trek through the Pacific NorthWest? Seems sensible. A scuba-diving expedition in the Turks and Caicos? Maybe not....
Heck, that's what I have to do on a fairly routine basis, when I evaluate research proposals. People tell me what they believe to be true, what they expect to find in support of that belief, and how that expectation supports their belief, and a research method that is likely to find that support if it exists.
If protons decayed (as some physicists believe, entirely without physical evidence, that they do), how would we know that? What evidence would they leave? What sort of equipment would we need to capture that evidence?
