Why is the manas not easily discovered?

Because the manas has no language or words, and its mental activities are hidden and profound, lacking the obvious functions of the mind consciousness such as inference, speculation, thinking, analysis, imagination, and fantasy, the manas's role as the master and its power of decision-making are still quite evident. When the power of meditative concentration is insufficient, wisdom is insufficient and the mind is coarse; no matter how obvious the manas's activities are, they 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 let known to others. Once you find the one behind the scenes, you have found the manas. The manas is a person's essential character, representing one's moral character and personality, and it plays a key role.

Many people, 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, deliberately hidden—the substantive one. When alone behind others' backs, hesitating and undecided, 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 will last a long time, and then it is inevitable that one will suffer inner collapse, mental fragmentation, and hidden dangers in the body, for body and mind mutually influence and constrain each other.

Yogācāra is also psychology. If you study Yogācāra well, you can perceive the subtle and know the manifest; observing people's psychology is not difficult. But when you understand a person, do not easily say it out loud, to avoid trouble and difficulty getting along with others. A person of straightforward mind, whatever thoughts they have, will speak directly, without nine bends and eighteen turns, without intestines winding eight circles. A person of crooked mind has thoughts that are hidden and not spoken directly, leading people around in circles; after getting people dizzy and confused, they lead them into traps of their own design to achieve their own goals.