The master may say that fish swim on mountains and birds fly in the sea. Mo matter what words are used, the master is interested in one thing ─ determining the disciple's level of understanding. Through this dialogue, the master may find opportunities for guiding the disciple, but not by explanation. The master will do this by using what is called the "opportune sharp action" ─ something that cannot be explained by words, or described by appearances. Still, the master uses language, sometimes gestures, to guide. If the disciple does not grasp the master's meaning, he is told to leave the room immediately.

Or the master may say, "All dharmas are reduced to one. To what is this one reduced?" The disciple may say, "I want to take a leak." What is the connection between the question and response? There doesn't seem to be any. But a master may recognize the disciple's level of experience from it. Perhaps the master may feel that the response is not genuine. The dialogue might continue with, "Who is it that wants to take a leak?" The monk may say nothing and just empty his bladder without further ado. But surely this seems insane from a conventional perspective.

If the monk appears to be feigning, the master may strike him with the incense board. The disciple may seize the board from the master, who might say, "Before you do it, tell me why you want to beat me." Or the master might say, "OK, I won't hit you now, but you owe me thirty blows." To which the disciple might say, "It's you who deserves a beating."

All those interactions would be unintelligible to a third party. But an alert master can immediately understand what's going on. A weak master may dish out punishment or make pointless remarks, and thus risk exposure to a clear-minded disciple. But this is not common. If it did happen, the master should, by all means, take instruction from the disciple.