Why is the manas not easily discovered?

Because the manas has no language or words, and its mental activity is hidden and profound, it lacks the obvious functions of the mind consciousness such as inference, conjecture, deliberation, analysis, imagination, and fantasy—yet the manas's capacity to take charge and its power of decision are still quite evident. When meditative concentration (samādhi) is insufficient, wisdom is insufficient and the mind is coarse; no matter how evident the manas's activity may be, it cannot be observed.

For example, a person who likes to lie often has two intentions: one operates on the surface and is relatively obvious, while the other operates covertly behind the scenes. A person's true intention is the one behind the scenes, not the one on the surface; the surface one merely serves as cover—feinting east while attacking west. The one behind the scenes is hidden, not easily exposed, and not meant for others to know. Once you find the one behind the scenes, you have found the manas. The manas is a person's essential character, representing a person's moral quality and personality, and it plays the key role.

Many people, when in front of others, have two inner voices: one that can be seen by others, displayed for others to see and evaluate, and another that they are unwilling to let others know—the deliberately hidden, substantive one. When alone behind others' backs, in moments of indecision, a person also has two opinions, two thoughts, two plans, two mental activities; because they are not unified, an internal war ensues. If the decision cannot be made, the internal war drags on long-term, and then it is hard to avoid inner collapse, mental fragmentation, and hidden dangers to the body—for body and mind mutually influence and constrain each other.

Yogācāra is in fact psychology. If you study Yogācāra well, you can perceive the subtle to know the evident, and observing people's psychology is not difficult. But when you understand a person, do not easily say it out loud, lest it cause trouble and make things hard to get along. A person of straightforward mind, whatever thoughts they have, will speak them directly, without nine bends and eighteen turns, without intestines winding eight loops. A person of crooked mind conceals their thoughts and does not speak directly, leading people around in circles; after getting people dizzy and confused, they steer them into the trap they have designed, achieving their own aims.