Why the Buddha Cannot Find the Eighth Consciousness in Nirvāṇa Without Remainder (anupadhiśeṣa-nirvāṇa)

In nirvāṇa without remainder (anupadhiśeṣa-nirvāṇa), the five aggregates (pañcaskandha) body no longer exists, and the eighth consciousness has nothing to rely upon, so it cannot manifest its own mode of activity. Without a mode of activity in operation, none of the Buddha's consciousnesses can discover the eighth consciousness.

Finding the eighth consciousness and observing the eighth consciousness can only be done on the five aggregates body; observing the eighth consciousness must be done through its operations on the five aggregates body. Without the five aggregates body, the eighth consciousness cannot be observed—just like observing wind: one must observe the wind on trees or on objects. Without trees or objects, even if there is wind in empty space, it cannot manifest itself. The situation of the eighth consciousness should be the same as that of the wind.

Something formless and without marks must manifest itself through dharmas that have form and marks; otherwise, being formless and without marks, how could it be discovered? For example, when you discover wind, you must discover the coolness and refreshing quality of the wind blowing on your body, or see clothes fluttering, trees swaying, or objects moving—only then can you discover the wind. If you did not have your own five aggregates body, how could you discover the wind? Without the swaying of external trees and grass, how could you discover the wind? To discover wind, one must find it through these material forms (rūpa), through the wind's mode of activity and its dynamic nature—finding the wind from the fluttering of objects, and discovering the wind through the coolness, refreshing quality, coldness, or heat felt when the wind blows upon the body.

Finding the eighth consciousness follows the same principle: it must be perceived through the operations of the five aggregates body, through the activities of the five aggregates. The presence of five aggregates activity indicates that the eighth consciousness is upholding, sustaining, and operating within the physical body. Without the five aggregates body, the eighth consciousness cannot manifest.

The Buddha said in the Twelve Links of Dependent Origination Sūtra: name-and-form (nāma-rūpa), the two, are mutually dependent—name-and-form conditions consciousness, and consciousness conditions name-and-form. Name-and-form refers to the five aggregates, and consciousness refers to the ālayavijñāna, the eighth consciousness. The five aggregates can only operate by being conditioned upon the eighth consciousness; without the eighth consciousness, there would be no five aggregates. That consciousness conditions name-and-form means that the ālayavijñāna must be conditioned upon the five aggregates body in order to manifest its own existence and operation; without the five aggregates body, the eighth consciousness cannot operate.