The Zen master addressed the gathered group and said, "You don't know anything." and one of the students replied, "What do you mean, we don't know anything?" and the master was silent and appeared puzzled, so I now know what the master means by not knowing anything, because at any given moment I don't know a thing and knowing for sure is so difficult that nobody probably does know anything, but I can also understand the student's response, because of course, I know all about this here and now, or so I think, so like me right now, the master was silent and puzzled, because probably he knew nothing.