But you can go and get info, and then judge, and say, "That prior that I held was wrong."
It is only wrong not to update.
And, of course the priors must be updated the correct way.
Nonetheless, it is greatly preferable to have a prior that led to decisions that gave high utility, rather than one that led to decisions that gave low utility. Of course this can't be measured "before hand". But the whole point of updating is to get better priors, in this exact sense, for the next round of decisions and updates.
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.