You almost always have some information to concentrate your priors. Between mutually-helpful speakers, implicit with an answer to a question is that the answer gives all the information you have on the question that could benefit the questioner. E.g.
What will the closing price of Apple be at the end of the year?
“Almost certainly somewhere between $150 and $250.”
The ability to quickly recall what I studied for its application.
I thought that was obvious. Why do you ask? What am I missing?