Is Knowing One Is Dreaming Within a Dream the Self-Validating Cognition (sva-saṃvitti-saṃvitti-bhāga) of the Mind Consciousness or the Self-Cognition (svasaṃvitti)?

The self-validating cognition (sva-saṃvitti-saṃvitti-bhāga) is the introspection of the consciousness-mind itself and its own mental factors. "Its own" means the mind consciousness discerning the mind consciousness, the manas discerning the manas, and the five sense consciousnesses discerning the five sense consciousnesses; it does not mean mutual discernment. The self-cognition (svasaṃvitti) is the consciousness-mind's discernment of the object-aspect realm, and this object-aspect includes all dharmas, certainly including the eighth consciousness and its mental factors as well—it simply depends on how capable the discerning wisdom is. A dream refers to the dream scenery, which is the object-aspect; knowing is the perceiving-aspect of the consciousness-mind. When the consciousness-mind discerns sense objects, that is the perceiving-aspect discerning the object-aspect, which is self-cognition, not self-validating cognition; the perceiving-aspect seeing itself is self-validating cognition. Only when the perceiving-aspect and the object-aspect are combined do self-cognition and self-validating cognition arise. Self-validating cognition is actually one kind of self-cognition, except that the object-aspect has become the consciousness-mind itself—oneself and one's mental factors have become the object-aspect. 

The perceiving-aspect that discerns the dream-scenery object-aspect is the perceiving-aspect of the sixth and seventh consciousnesses, and the sixth consciousness here is the solitary mental consciousness. Seeing all realms is mainly the seeing of the sixth and seventh consciousnesses; what sentient beings can feel and observe is only the seeing of the mind consciousness—they cannot perceive the seeing of the seventh consciousness. For now, let us speak of the seeing of the mind consciousness. When asleep and dreaming, why does the solitary mental consciousness not know that it is dreaming? Because in the dream the mind consciousness is dull and unclear; sleep itself is a kind of hindrance and obstruction that veils the wise cognition of the mind consciousness. 

If the sleep hindrance is removed and there is no more obstruction, the mind consciousness becomes clear and lucid, and the first dhyāna will be attained; or, as meditative concentration grows ever deeper, sleep becomes less and shallower, so that in dreams the mind consciousness becomes increasingly lucid—to the point of clearly knowing one is dreaming, of not committing unwholesome karma even in dreams, and even of performing wholesome karma. Therefore, knowing one is dreaming within a dream shows that the sixth and seventh consciousnesses possess samādhi and wisdom, and that the hindrance of sleep is slight. Not knowing one is dreaming within a dream means the consciousness-nature of the sixth and seventh consciousnesses is veiled by sleep, and the mind is not clear and lucid.

The knowing and seeing within a dream is the perceiving-aspect of the solitary mental consciousness. The manas has a great influence upon the seeing of the mind consciousness, but we will not discuss the specific influence here. The solitary mental consciousness in a dream has limited discernment of realms, not as comprehensive and clear as the mental consciousness accompanying the five sense consciousnesses (pañcavijñāna-sahagata-manovijñāna), which is aided by the five sense consciousnesses in its discernment. Not knowing one is dreaming within a dream is due to the insufficient functioning of the solitary mental consciousness's self-cognition and its weak power of wisdom; this is related to the physical body and the manas. The strength of all the discerning functions of the mind consciousness is related not only to its own samādhi and wisdom, but also to the samādhi and wisdom of the manas, and to the physical body. One cannot discuss the functions of the mind consciousness apart from the physical body and the manas.

Why is it related to the physical body? Everyone knows the principle that the mind consciousness's knowing while awake is influenced by the physical body. During sleep, the manas does not wish to discern realms, so none of the six consciousnesses arise; while dreaming, the solitary mental consciousness is forced to arise and discern the dream scenery, but because the nervous system's activities are rather sluggish, the mind consciousness's thinking is suppressed, its cognitive wisdom is relatively low, and it cannot distinguish that the realm it faces is a dream, so it takes the dream as reality. This is the same as the situation when drunk—both are caused by an inactive nervous system.

If, within a dream, the mind consciousness has self-validating cognition, that means the mind consciousness can know itself and its own mental factors—this is the power of introspection, which requires even stronger samādhi and wisdom than the mind consciousness's knowing of sense objects, and is more difficult. If the mind consciousness's self-cognition function is insufficient in a dream, then its self-validating cognition function is almost nonexistent, and it will not validate itself; therefore it cannot introspect—unless one is a person of excellent meditative concentration and strong awakened nature. For those who possess the four dhyānas and eight samādhis, the power of introspection in dreams is even better.

The strength of the various functions of the mind consciousness is not only a matter of its own samādhi and wisdom, but is even more related to the manas. Although from ancient times to the present almost no one has been able to recognize and observe this problem, the functions of the mind consciousness are indeed inseparable from the manas; the two complement each other. To discuss the mind consciousness apart from the manas is to abandon the root and chase the branches.