The Zen Teaching of Huang Po
Tr. by John Blofeld
Huang Po was a Zen master in the ninth century in China who got his name from the mountain where he lived. His teachings, consisting of sermons, dialogs, and anecdotes, were recorded by P'ei Hsiu, a scholar and official in a nearby town. Since Huang Po did not preach a rigid doctrine, his teachings were tailored to his audience. And because his audience was often comprised of Buddhist monks, much of Huang Po's teachings were aimed at breaking down specific doctrines that the monks clung to.

If Huang Po's philosophy can be put into words (which he repeatedly says it cannot) it is that man must break through all of his false concepts based on sense perception in order to see his true Self. He explains to his students that, "if you students of the Way wish to become Buddhas, you need study no doctrines whatever, but learn only how to avoid seeking for and attaching yourselves to anything." Not only are doctrines not sufficient but neither are practices:

So if you students of the Way are mistaken about your own real Mind, not recognizing that it is the Buddha, you will consequently look for him elsewhere, indulging in various achievements and practices and expecting to attain realization by such graduated practices. But even after eons of diligent searching, you will not be able to attain the Way. 

Even the sacred Buddhist concept of Enlightenment is not safe from Huang Po's destruction of concepts:

In their anxiety to seek Enlightenment on the one hand and to escape from the passions and ignorance of corporeal existence on the other, they conceive of an Enlightened Buddha and unenlightened sentient beings as separate entities. Continued indulgence in such dualistic concepts as these will lead to your rebirth among the six orders of beings, life after life, eon upon eon, forever and forever!
 
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