The hiddenness or manifestness of the manas depends entirely on the wisdom of observation of the mind consciousness

The deliberation (manana) of the mind consciousness is overt and easy to observe, whereas the deliberation of the manas is covert and not easy to observe. Because the mind consciousness has a relatively strong power of introspection, the solitary mental consciousness can observe some of the modes of activity of the mental consciousness accompanying the five sense consciousnesses (pañcavijñāna-sahagata-manovijñāna) and of the solitary mental consciousness itself, but it cannot observe them all, because the mind consciousness has not achieved the transformation of consciousness into wisdom. The Buddha can observe them all, and the wisdom of the varieties of paths of bodhisattvas who have attained the bhūmis can observe most of them.

However, when the solitary mental consciousness is obstructed by afflictions, lacks sufficient meditative concentration (samādhi), and has not transformed consciousness into wisdom, it cannot observe the modes of activity of the manas. That is why it must be said that the deliberation of the manas is hidden. In fact, for the Buddha and for bodhisattvas who have transformed consciousness into wisdom, the modes of activity of the manas are still easy to observe. Whether it is hidden or overt depends entirely on the observational wisdom of the mind consciousness, not on the manas itself.

The manas also has self-validating cognition (sva-saṃvitti-saṃvitti-bhāga) and possesses a weak power of introspection, capable of observing its own modes of activity, but the manas cannot express this, so the mind consciousness—which is what we call "we"—does not know. Since the mind consciousness does not know the modes of activity of the manas, it also does not know whether the introspective power of the manas is strong or weak.

Regarding things the mind consciousness does not know, many people's mind consciousness habitually denies them, saying they do not exist. Then, since the mind consciousness cannot observe the Earth's revolution around the sun and its rotation, one could also say the Earth is motionless. Saying so would cause no harm, but it would not accord with the facts. How many facts and truths can an ordinary person's mind consciousness actually observe? Not many—ignorance (avidyā) is too abundant and too thick, and the obstructions are too heavy. Yet precisely those with the most ignorance are the least willing to admit their own ignorance and trust their own judgments all the more. This is truly helpless.