What is the true state of applying effort in genuine Chan investigation?

When truly engaged in the effort of investigating Chan, because meditative concentration is very deep, the mind consciousness has almost nothing to occupy itself with; only the manas remains in the state of sustained examination (vicāra), deeply probing. Finally, when the causes and conditions are complete, the manas will suddenly find the tathāgatagarbha that is presently operating within the five aggregates, and thus awakening is realized. At the same time, the manas transmits this message to the mind consciousness, and the mind consciousness thereupon suddenly understands—it is awakened almost simultaneously with the manas, and the manas directs the mind consciousness to slap its thigh. As long as the manas has realized awakening, the body and mind at that moment will inevitably react differently from ordinary times: the body and mind are tranquil and at ease, the mood is joyful and delighted, relaxed and free. If there is only the mind consciousness's understanding, there will be none of these signs and reactions, because the mind consciousness does not make the decisions and cannot direct the body faculty. Without meditative concentration, or with shallow concentration, the manas cannot be put to use, because it cognizes many dharmas and cannot investigate alone, nor can it investigate together with the mind consciousness.

Generally speaking, whenever any dharma is truly realized, there is meditative concentration, and the manas participates in the process of investigation; in the end it is always the manas that realizes, and then tells the mind consciousness. If the mind consciousness realizes first and then tells the manas, the manas cannot fully investigate and deliberate (manana); it merely reluctantly agrees with the mind consciousness's views and opinions. The degree of awakening is shallow, the manas does not understand completely and fully, and regression is very easy. When the manas realizes it by itself first, one is often firmly convinced and will not regress.

As for the mind consciousness engaging on its own in sentimental thinking and intellectual interpretation, with the manas not participating in the entire process of thinking—even if the mind consciousness understands some principles, the manas remains muddled and full of doubts; the mind consciousness, being coarse, generally cannot detect the manas's mental state. Any conclusion or answer that the mind consciousness arrives at on its own is neither ultimate nor thorough, and has no evidence, or insufficient evidence. There is no question of speaking of regression or non-regression, because there was never any forward progress at all—how could there be any talk of falling back?