What is the meaning of "not establishing words and letters" (不立文字) in Chan Buddhism?

The Chan school is also called the "gate of the source" (zongmen). The source of the Buddhadharma is the true mind, the tathāgatagarbha, and Chan is the dharma gate of investigating Chan to awaken to the true mind, the tathāgatagarbha. Although the tathāgatagarbha has no language, words, or sounds, the entire process of investigating Chan likewise does not use language, words, or sounds. Whatever is conveyed through language and words is not the true mind. Therefore, during Chan investigation, the language, words, and sounds of both the one transmitting the Dharma and the one receiving it become useless; all books and theories become useless; the investigator no longer needs to mutter to himself, ramble on, or hum and haw—everything that could serve as an external reference for comparison is stripped away.

In this way, there is no longer any room to roam freely through fanciful thoughts and intellectual interpretations, to give full rein to inference and erroneous cognition. The mind consciousness has no room to perform, and one must honestly rely entirely on the manas' direct perception (pratyakṣa) to ponder and investigate. Though this is arduous and keeps one sleepless through the night, the fruits are abundant: it can unearth the potential and wisdom of the inner manas. Once you dig up your own family treasure, from then on you will live a free and prosperous life, no longer wandering destitute, begging your way through bitter days.

At this point, the written words outside and the words in your mind are both useless and powerless. Only by relying on your own wisdom can you develop the great wisdom inherent in yourself. Reasoning, analysis, organizing, summarizing, dissecting, integrating, conjecturing, imagining, comparing, scriptural authority, theories, knowledge, learning—all of these become unusable. The mind consciousness settles down and no longer needs to busy itself. At this point, a responsible Chan master will tell you to put the Buddhist sutras away and forbid you to read scriptures and books; violators will face the disciplinary ruler. Once you reach a critical juncture in your investigation, getting struck is an absolutely good thing. Although language and words are all unusable, you can still be struck. When you are struck, there is likewise no language, words, or thinking, yet it can stir the inspiration of the manas.

When the master wields the stick, if the mind consciousness is very active, it will immediately think and analyze, saying, "This might be it"—but the result is: Wrong! The mind consciousness then analyzes and reasons, "The coalescence of the real and the deluded—this is not wrong"—but the result is still: Wrong! You go further, using the process of elimination to infer and conjecture: "This is not the eye consciousness, not the ear, nose, or body consciousness, nor the mind consciousness or the manas—it must be the eighth consciousness"—but the final result is still: Wrong! If you dare to engage the mind consciousness, no matter how, the answer is one word: Wrong! After three wrongs, if you still fail to awaken, the Chan master will drive you out of the Chan hall, or even out of the Chan monastery and temple, refusing to keep you any longer, because you are not yet a suitable vessel for the Path and have no qualification to investigate Chan. Of course, a properly qualified Chan master will not wield the stick recklessly; he will surely discern the psychological state of the investigator and deliver the blow at the most opportune moment. This is called "the blow that fits the occasion"—casting off all defiled objects and sentimental attachments, directly recognizing, in valid direct cognition, that which is neither defiled object nor sentiment.

The patriarchs and great masters of the past always said: if the thieving mind does not die, one cannot awaken to the Way; if the bandit mind does not die, one cannot awaken to the Way. What minds do the "thieving mind" and "bandit mind" refer to? Stealing what, one cannot awaken to the Way? Who is the thief? What has been stolen? During Chan investigation, how does one remove the thieving mind? The thieving mind in Chan investigation can also be called the mind of opportunism, the mind that seeks shortcuts—the mind that directly takes knowledge and theories from elsewhere and treats them as realization, as personal verification. Because it is not personally verified by the manas itself, whatever the mind consciousness opportunistically brings in from elsewhere is called "stealing." In the past, a phrase was often used to describe the Dharma teachings of patriarchs with genuine realization: their Dharma was said to be dug out from the depths of their own hearts. This means that the Dharma the patriarchs taught was all realized through their own practice, the crystallization of their own wisdom—not ready-made theoretical knowledge that the mind consciousness carted in from elsewhere, nor theories they had learned, merely organized, summarized, processed, and repackaged with a new face to pass off as their own. Because such things do not count as awakening to the Way, and they also obstruct awakening.

What is called "immediate manifestation from one's own mind (manas)"? Only what is dug out from one's own breast is called immediate manifestation from one's own mind. "Breast" and "the depths of the heart" both refer to the deep dwelling place of the manas, the master. The opposite of this is what the mind consciousness effortlessly interprets—what is worked out without cultivating precepts, samādhi, and wisdom, or the thirty-seven factors of enlightenment—what is deduced by comparing and cross-referencing learned theories and other people's views. This is pretty much taking it for free. When the mind consciousness acts this way, it is pretty much stealing. If the thieving mind does not die, the manas cannot deliberate and investigate, and one cannot realize the Way. When the mind consciousness learns a great deal of Dharma, in substance it is all stealing, because it is not from one's own breast, not one's own family's—it is all Dharma from elsewhere, Dharma that goes in the ear and out the mouth, Dharma learned and immediately resold. None of it is one's own family treasure.