According to what criterion? You'd end up comparing a prior to the prior you hold, with the "best" prior for you just being the same as yours. Like with preference. Clearly not the concept Unknowns was assuming -- you don't need luck to satisfy a tautology.
According to what criterion?
Correspondence to reality.
(Do you realize how inferentially far the idea of prior as part of preference is from the normal worldview here?)
This is our monthly thread for collecting these little gems and pearls of wisdom, rationality-related quotes you've seen recently, or had stored in your quotesfile for ages, and which might be handy to link to in one of our discussions.