Dharmas unknown to the mind consciousness do not thereby fail to exist

Dharmas that the mind consciousness cannot observe do not mean those dharmas do not exist, because the mind consciousness is foolish and ignorant. Just as the mind consciousness cannot observe the eighth consciousness, this does not prove that the eighth consciousness does not exist. What mental activities the manas actually engages in during sleep, ordinary people indeed cannot observe. That does not prove the manas has no mental activities; the Buddha can know any mental activity of the manas at any time.

The vast majority of the manas's mental activities cannot be observed by the mind consciousness of ordinary people, but that does not mean the manas does not have so many mental activities. In cultivation, one should make good use of logical thinking. Only by earnestly improving one's capacity for logical thinking, together with deliberation (manana) upon the Dharma within meditative concentration (samādhi), can one effectively enhance wisdom, continually eliminate ignorance, observe more and deeper dharmas, and realize more and deeper principles.

The eight consciousnesses (the eight kings of consciousness) at the Buddha-stage can be observed by no one, and therefore cannot serve as a basis for one's own arguments. The eight consciousnesses prior to the Buddha-stage can be observed to a small extent by bodhisattvas who have attained the bhūmis, and therefore others also may not take them as a basis for debate. Whatever has not been personally observed by oneself may not be used as a basis for argument.