Why Does Buddhism Strictly Prohibit Explicitly Revealing the Secret Meaning?

All dharmas in Buddhism that need to be realized and awakened to belong to the secret dharma. What is meant by "secret dharma" is that these dharmas require one to personally investigate and personally verify them oneself; one should not obtain ready-made answers from others, nor should one use the conscious mind to guess and imagine. Because ready-made answers obtained from others, as well as answers produced by guessing and imagining, only correspond to the conscious mind—the conscious mind can easily understand and grasp them, but the manas cannot understand and grasp them. For the manas to understand and grasp, it must go through the process of investigation; the manas must personally participate in the conscious mind's deliberation and verification, understand every detail transmitted by the consciousness, grasp every piece of evidence, and carry out verification and deliberation (manasikāra). Only when the evidence is sufficient and the manas has deliberated clearly can the manas know with finality. If the manas does not know, there is no realization; if the manas does not realize, there is doubt; with doubt, one has not realized truth, and there is no liberating benefit of experience.

Therefore, in Buddhism, not only is it strictly forbidden in the Mahāyāna dharma to openly reveal the hidden meaning, even in the Hīnayāna dharma it is forbidden to openly explain contemplative practice (vipaśyanā-caryā) in overly specific terms, so as to avoid the situation where the consciousness knows but the manas does not. If it is openly stated, the conscious mind will immediately understand, but there will be no investigation; without investigation, the manas cannot understand and cannot realize it. If the manas has doubt and cannot resolve it, then there is no liberating benefit of experience.

Therefore, for any dharma in Buddhism, whether of the Mahāyāna or Hīnayāna, it is not enough for it to be realized by the conscious mind alone; the most important thing is to let the manas realize it. Because the manas governs body and mind, once it realizes the truth, it can accord with the truth and relax body and mind, thereby bringing about the liberating benefit of experience in body and mind. The intellectual understanding of the conscious mind has no liberating benefit of experience. When the manas realizes awakening, the body-mind world will undergo a turning and obvious changes; others can see from the outside that this person's mental state has changed—relaxed and at ease, spirited and vigorous. The Chan masters of the past had the dharma eye; when they saw a disciple who had been engaged in Chan investigation walking over to report the results of their investigation, without the disciple opening their mouth, the master would already know that this person had attained the Way, because they could see that the disciple's entire spiritual demeanor and temperament had changed.

From this it can be seen how crucial and important the manas is for realizing the dharma—it must not be overlooked. Practitioners must never be satisfied with the coarse and shallow understanding of the conscious mind while abandoning the deep personal realization of the manas, thereby forfeiting the great benefit and true benefit of the Buddha's dharma.