No concepts, no words
Huangbo struggled with a fundamental dilemma of Chan: how the wordless wisdom of intuition can be passed from generation to generation. Enlightenment necessarily has to be intuitive, and that means traditional teaching methods are useless. There are no conceptual formulations or "concepts." It is by definition wordless. It has to be realized intuitively by the novice, by himself. The masters had isolated a type of knowledge that words could not transmit. It was this transmission of wordless insight of Mind, that obsessed Huangbo.
As did other masters, Huangbo also employed silence as a teaching device, using it to teach wordless insight by example. In one pointed story Huangbo was invited to teach the local governor, who made the mistake of presenting the master with a written exposition of the teachings of Chan. Huangbo greeted this with silence, his "exposition" of Chan.
The Prime Minister invited the Master to the city and presented his own written interpretation of Chan to him. The Master took it and put it on the table. He did not read it. After a short silence, he asked the Prime Minister, "Do you understand?"
The minister: "I do not understand."
The Master: "It would be better if you could understand immediately through inner experience. If it is expressed in words, it won't be our teaching."
This exchange brings out the essence of Huangbo's concerns. His most insistent conviction was that Chan cannot be taught, that it must be somehow gained intuitively. He was contemptuous of conceptual thought, believing it to be the greatest hindrance to achieving intuitive insight. The problem is the mistaken belief that Zen can somehow be taught and understood if only one grasps the concepts. But concepts only serve to obstruct intuition; Zen intuition can work only outside concepts. As Huangbo put it:
Since Zen was first transmitted, it has never taught that men should seek for learning or form concepts. "Studying the Way" is just a figure of speech. It is a method of arousing people's interest in the early stages of their development. In fact, the Way is not something which can be studied: Study leads to the retention of concepts and so the Way is entirely misunderstood.
The use of the rational mind in the study of Chan is only useful at the beginning. But once the flash of intuitive insight has been snared in the net of the rational mind’s ken, the net must be discararded. Elsewhere he likens the extended use of analytical thought to the shoveling of dung.