Why Does One Feel Fatigued After Excessive Contemplation?

Question: The physical body is composed of the four great elements, and the four great elements in the body are also constantly flowing and changing. A person absorbs the four great elements from outside the body through eating, breathing, and so on, transforming them into the nutrients composed of the four great elements that the body needs. At the same time, the four great elements in the body are also constantly being worn down and expelled through various excretions. And for all of this operation, only the tathāgatagarbha has this function. When a person is thinking, the tathāgatagarbha continuously takes in the four great elements at the supreme faculty and manifests them as mental sense-objects, for the mind consciousness and the manas to discern. Therefore, when one thinks too much, the nutrients of the four great elements at the supreme faculty are consumed excessively, and the brain will feel fatigued. When the supply of the four great elements' nutrients to the supreme faculty is insufficient, the capacity for thinking declines. When a person is overly fatigued, one must, through sleep, have the tathāgatagarbha operate the four great elements to replenish the nutrients of the four great elements in the supreme faculty. Is it so?

Answer: The mental sense-objects of solitary image-objects do not require consuming the four great elements of the supreme faculty, whereas form subsumed under the Dharmāyatana does require consuming the nutrients of the four great elements within the supreme faculty. However, when the manas and the mind consciousness are operating, they must activate the supreme faculty and the neurons, must release bioelectric signals, and must consume the nutrients of the four great elements. Therefore, when one thinks too much, the brain will feel fatigued and needs to rest for a while, awaiting the re-accumulation of energy in the brain.

When the conscious mind stirs, the brain's neurons fire, releasing bioelectric signals and releasing energy. Even when in meditative concentration and the six consciousnesses are not moving, the manas is still subtly discerning, secretly active, and this also consumes a little of the nutrients of the four great elements. The more subtle the manas's activity, the less is consumed; the deeper the meditative concentration, the more subtle the manas's activity, and the less is consumed. When one enters the concentration of no-thought, one can remain in concentration for several kalpas or even longer, without needing food or drink, but the body will still become thin and weak.