Why Don't We Know We Are Dreaming While in a Dream

In a dream, knowing that it is a dream—who knows this? When awake, knowing sense objects—who knows this? Whether within the dream or outside it, both the sixth and seventh consciousnesses have knowing, with the knowing of the sixth and seventh being primary; the five sense consciousnesses can only know the five sense-object realms in reality, and cannot know the realms within a dream.

The knowing nature of the mind consciousness is greatly related to the physical body. When the physical body has obstructions, the knowing of the mind consciousness becomes weak or ceases. A person who has attained the four dhyānas and eight samādhis has no obstruction in the physical body; the knowing of the mind consciousness is clear and vast, and whether asleep or not, one can know with great clarity. Even if one drinks many bottles of wine, one will not become drunk, for alcohol can no longer paralyze the central nervous system of the brain, and thus the mind consciousness is unaffected.

The knowing of the mind consciousness is also greatly related to the knowing of the seventh consciousness (manas). Generally speaking, the seventh consciousness knows all dharmas; the question is only whether it knows them as they truly are. As for the portion that the seventh consciousness can know truthfully, how it can influence the mind consciousness so that the mind consciousness also knows, and promptly processes what is known—that involves the capacity for communication between the two consciousnesses. This so-called capacity for communication is wisdom. How what the mind consciousness knows can effectively influence and perfume the seventh consciousness also involves this capacity for communication—that is, how good the wisdom is.

Wisdom is in turn closely related to meditative concentration (samādhi). Meditative concentration can make the mind quiet, peaceful, and steady, strengthen the capacity for contemplation, and make the power of wisdom great; then the mutual influence between the two consciousnesses is great. Meditative concentration can also render the physical body unobstructed; with the physical body unobstructed, the mind consciousness has no hindrance, its knowing is keen and unimpeded, and it can effectively influence the seventh consciousness. Conversely, the seventh consciousness can also effectively influence the mind consciousness; the two exchange what they have, and knowing all dharmas becomes smooth and unimpeded, with little obstruction.

Being the same whether awake or dreaming is a realm of wisdom cultivated through practice. Knowing that it is a dream and not being trapped by the dream-state is wisdom. This cultivation mainly refers to meditative concentration; concentration is an indispensable link in practice—only with meditative concentration can wisdom be developed, making the knowing of the sixth and seventh consciousnesses more truthful and more in accord with principle, knowing more truly, more subtly, and more vastly. Moreover, only by removing the hindrance of sleep can profound meditative concentration arise. For a person whose concentration is deeper, thinking is clear when awake, and even in dreams there is no delusion—just as when awake—knowing the realms without obstruction.

The knowing of ordinary people has obstructions—that is, in common parlance, they lack superknowledge (abhijñā). For those who have superknowledge, their knowing is unobstructed, possessing knowledge of others' minds, the divine eye, and so forth. This is the karmic retribution of the merit of concentration and wisdom. Knowing a dream within a dream is the retribution attained by a person whose meditative concentration is excellent and whose mind has become pure. Monk Jigong had the four dhyānas and eight samādhis and possessed superknowledge; no matter how much wine he drank, his nervous system was not affected or anesthetized, and his mind consciousness was always clear and awake, able to observe and know all realms as they truly are. When ordinary people fall asleep, the mind consciousness ceases, and the portion of the manas' function that relies on the mind consciousness to know realms no longer operates; therefore, when dreaming, the manas' discernment is weak and it does not know it is a dream, and the solitary mental consciousness in the dream also has very weak discernment and likewise does not know it is a dream. But a person with cultivation, whose power of concentration is strong, whose physical body is unobstructed, and whose sixth and seventh consciousnesses are clear, has strong discernment and, while dreaming, knows it is a dream and is not deluded. 

Master Kuiji had the four dhyānas and eight samādhis and possessed superknowledge. When he slept at night he was extremely clear and lucid, even more lucid than ordinary people when awake; his sixth and seventh consciousnesses were keen. After he had fallen asleep, when a leg of a louse fell off and it cried out in pain, Master Kuiji could hear it—this is the merit of the power of concentration and the power of superknowledge. Being able to hear the cry of a louse while asleep—does this not show that he was not actually asleep? For ordinary people, sleep is a covering that can veil their minds so that they neither see nor hear, like dead people. But for one who has eliminated the covering of sleep, very little sleep suffices to nourish the physical body; concentration will reach the level of the first dhyāna or above, the mind is clear, obstructions are slight or entirely absent. During sleep, the mind consciousness may not be completely severed, yet sleep is still sufficient—this differs from ordinary people.

Especially for those who possess superknowledge, their sleep is like being awake, even more lucid than ordinary people when awake. In ancient times, those with martial arts skills also slept lightly and were highly alert. This alertness can be said to belong to the mind consciousness, but the manas indeed also has alertness; its function of alerting the mind consciousness is still very strong, so without the manas, the functions of the mind consciousness cannot be fully explained. Sleep is of the same category as torpor; both belong to the hindrances and coverings, which can veil the light of the conscious mind. Only after the hindrance and covering of sleep is eliminated will the concentration of the first dhyāna appear. The deeper the torpor when sleeping, the poorer one's meditative skill—or one has no concentration and heavy coverings; the more deluded one is in dreams, the less concentration one has; the more easily one becomes drunk, the greater the obstruction of the physical body and the less concentration one has. Those with deep meditative skill can regulate the physical body well, unaffected by environmental factors, without obstructing the functioning of the six consciousnesses. Therefore, the power of concentration is extremely important. Even for those who do not study Buddhism or cultivate practice, if meditative concentration is well cultivated, the benefits are also very great.