Why Can Closing the Eyes Nourish the Spirit?

"Shen" (spirit) refers to the mind consciousness. First, it refers to the eye consciousness; second, to the mind consciousness; third, to the manas. The eighth consciousness does not need nourishment; it consumes no energy and is never tired.

Can the manas get tired? Since beginningless kalpas, the manas, like the eighth consciousness, has never rested. Although it is not always willingly bearing its burdens without complaint, it grasps at all dharmas and worries over everything. When will it finally become unwilling to worry?

The manas also has times of weariness, boredom, and fatigue. It cannot persist in one way from beginning to end. Therefore, the manas also needs rest, shifting its attention to relatively relaxed and pleasant matters, and ceasing to engage with (攀缘) troubling affairs. When there is too much engagement and it can no longer carry the load, it knows to set things down temporarily.

What most needs nourishment is the mind consciousness, because whenever the mind consciousness becomes active, it consumes certain nutrients, especially brain cells. When material energy is insufficient, the mind consciousness feels fatigued. When there is a great deal of thinking to do, the mind consciousness's train of thought can no longer keep up; at such times, rest is needed—no more discerning, discriminating, distinguishing, or deliberating.

Does the eye consciousness need nourishment? When the eyes look at things for a long time, they will ache, vision declines, things become unclear, and the head feels dizzy and swollen. However, this is not a problem of the eye consciousness, but rather that the eye faculty, fixed on one object for a long time without moving, causes nerve fatigue. The material form (rūpa) of the eye faculty belongs to part of the body faculty; when a problem arises with the eye faculty, it is a problem of the body faculty. The sensation of fatigue and soreness is tactile sensation, which is what the body consciousness discerns.

Because the eye faculty spends a long time looking at objects, it consumes more energy. The attention of both the manas and the mind consciousness is directed onto a single object, which consumes brain cells and also causes fatigue and weariness. If the optic nerves being constantly taut posed no problem, then it would not matter how long the eye consciousness looked at objects.

The optic nerves connect to the liver meridian. Prolonged looking causes fatigue and damage to the liver meridian, and problems will arise in the liver. Problems in the liver will affect the mind consciousness's thinking and discernment. The physical body influences the conscious mind, and the conscious mind also influences the physical body; body and mind are mutually dependent.

In fact, the conscious mind never has problems in itself; the issue lies in whether the body's material energy can be supplied sufficiently. The normal functioning of the conscious mind requires that the six sense objects appear normally and that brain cells can function normally. If material form is consumed excessively, or the supply is insufficient, the operation of the conscious mind will be affected, and it can no longer perform its function of discernment normally.

Closing the eyes to rest the spirit (闭目养神) can also be described as regulating the activity of the nervous system, not letting the nerves become overactive or excessively strained—especially rigid, unidirectional, forced activity—so that the body remains undamaged.