Can the self-validating cognition of the eight consciousnesses always operate in the present moment?

Self-validating cognition (svasaṃvedana) is precisely the power of introspection (pratyavekṣā-bala), the power of awareness and the power of knowing. The self-validating cognition of the seventh consciousness (manas) cannot appear at all times, because when the power of meditative concentration (samādhi) and the power of wisdom are insufficient, the consciousness will not have the ability to introspect and reflect upon its own mind. The eighth consciousness can at all times possess the power of introspection and self-validating cognition, because the meditative concentration and wisdom of the eighth consciousness exist forever, never change, and are forever neither increasing nor decreasing—they exist without any need for cultivation.

For example, the self-validating cognition of the mind consciousness, which constantly illuminates and observes its own mind, requires very strong power of meditative concentration, and the power of wisdom must also be good. The contemplative practice (vipaśyanā-caryā) method taught by the Buddha in the Mahāsatipaṭṭhāna Sūtra is precisely the method of illuminating and observing one's own mind: one must know whatever one is doing. With this knowing, the mind has concentration; without knowing, the mind scatters. Why did the Buddha teach in this way? Because the minds of sentient beings are all scattered and cannot be aware of their own minds. Being aware of one's own mind is self-validating cognition; if one cannot be aware of one's own mind, there is no self-validating cognition.

Those who have the power of introspection and can be aware of their own minds possess, on the one hand, a certain power of wisdom, and on the other hand, a certain power of meditative concentration—this is so whether or not one studies Buddhism. Thus everyone's wisdom differs: some people understand themselves, and some do not understand themselves. By the same token, the other consciousnesses are also like this: their self-validating cognition cannot always be present and operating.

Self-validating cognition is the power of introspection, the ability to observe what one is doing, what one has already done, and what one intends to do. Within it, of course, the perceiving-aspect (darśana-bhāga) and the object-aspect (nimitta) cannot be absent, nor can self-cognition (svasaṃvitti) be absent. The "what" of "doing what" is the object-aspect; "doing" is the perceiving-aspect; "doing what" is self-cognition; and knowing what one is doing is self-validating cognition.