Why Distinguish the Functional Roles of the Manas and the Mind Consciousness?

When both hands need to move together, they must be coordinated and their movements must be identical in order to accomplish the task; otherwise it is difficult. The same is true for the two eyes, two ears, two nostrils, two feet, and two legs: their movements must be coordinated and their goals identical or similar for things to be accomplished easily; otherwise, non-coordinated movements are not easy to carry out. Why is this? The movements of the two hands are commands issued by the brain, and the brain is directed and controlled by the manas. When the manas wants to use the hands to do something, it issues a command, and the two hands must act simultaneously. If the manas wants the left and right hands to do two different things at the same time, the commands transmitted by the brain must be split into two parts, and the mind consciousness and body consciousness must be divided into separate streams; the nervous system then has to strain to cooperate, unless one has undergone a period of special training.

As for the two eyes, no matter how they are trained, they cannot each touch, each attend, and each discern independently; it is very difficult to separate them. The two nostrils are also very hard to separate—one exhaling while the other inhales—though perhaps it is possible for those specially trained. The two ears are relatively easier to separate in their activities. It is also rather difficult for the two feet and two legs to move separately and independently in an uncoordinated way. The reason it is difficult is that they belong to one faculty, one nervous transmission system, one set of brain commands. The ease or difficulty depends on whether the manas's attention and energy are sufficient and abundant, and also on whether the energy of the six consciousnesses is sufficient.

By separating the functions and roles of the manas and the mind consciousness, one can understand the respective characteristics of the manas and the mind consciousness better and more clearly; when they are mixed together, the characteristics of neither consciousness can be understood clearly. Once the functions and roles of the manas and the mind consciousness are separated, and one observes the manas on its own, one can know what characteristics the manas has, what afflictions it has, what habitual tendencies it has, and what mental factors (caittas) it has; without having to chew over other people's words, one will have the ability to observe the true situation for oneself.