The Manas Constantly Deliberates—Why Is Sleep Still Needed?

Sleep is for restoring the energy of the material body and eliminating the fatigue of the material body, so that the six consciousnesses can operate normally, better, and more effectively. The manas regards the material body as its own possession, regards the six consciousnesses as its own possessions, and regards the five aggregates and eighteen realms all as its own possessions; it also relies on the eighth consciousness to know the condition of the material body in every instant. The activity of the six consciousnesses consumes energy. In order to reduce energy consumption, the manas decides not to let the six consciousnesses continue their activity, and actively shuts off the six consciousnesses' discernment of the six sense objects, no longer wishing to know the six sense objects, relying only on the manas's own knowing. In this way, energy continuously accumulates, and when vitality has recovered to a certain degree, the manas will decide to wake up, make contact with sense objects, and continue the activities of the five aggregates.

If the material body is fatigued, sleep is needed to restore energy, and the manas will decide to sleep, not letting the six consciousnesses continue their activity. The manas itself wishes to shut off the six sense objects and not discern them, and thus the five sense consciousnesses and the mind consciousness will gradually cease. Therefore, it is not that the manas needs to sleep, but that the material body needs rest, to replenish energy and restore vitality. This is precisely the result of the manas's constant, attentive deliberation (manasikāra). However, sleep does not affect the manas's constant, attentive deliberation; the manas can continue deliberating during sleep, and can even manifest dream states, deliberating within those dreams.