A couple days ago, I was flipping through Thomas Merton's little pamphlet on how to approach Scripture. He pointed out an example of the typical master-disciple exchange in Zen Buddhism: the disciple asks, "Who is the Buddha?", and the master replies, "Who are you?" The surface interpretation of this dialog is that you are the Buddha and I am the Buddha and everybody is the Buddha so let's all be happy hippies all together now. Merton explains it in a different way: the disciple goes to the master looking for facts, for doctrine to fill in the blanks in her spiritual worksheet. In reply, the master offers a question instead of an answer. Knowledge of the Buddha is not doctrine but experience, and therefore it requires a process of internal reflection and self-discovery ("Who are you?").
Interpreted a different way, this is what good advisors do with their students. If the answer to a question is known, it can be found in some journal paper or textbook. Instead, good advisors offer questions, because the process of scientific insight and discovery cannot begin without a good question. Long experience in a field develops the ability to ask the right questions, rather than the ability to accumulate knowledge. (Perhaps this is why among professors, good lecturers are much harder to find than good researchers!)