The dharmas known by the manas are not necessarily known by the mind consciousness.

Question: Sometimes when walking, I cannot see whether someone is following behind me, yet I can know that someone is behind me. How do I know this? Are the people and objects behind me the inner object-aspect (nimitta) within the back of my head? Can material form (rūpa) enter the supreme faculty (indriya) at the back of the brain without being transmitted through the eye faculty?

Answer: The people and objects behind you cannot be transmitted through the eye faculty into the supreme faculty at the back of the brain, because the eye faculty does not face the back of the head. In the Śūraṅgama Sūtra, the Buddha said that among the twelve hundred merits, the eye faculty possesses only eight hundred merits, meaning that the eye faculty can contact material form directly in front, and about two-thirds on each side, but cannot contact the rest. Therefore, knowing that someone is following behind you—this knowing is the subjectively imagined realm, a mental sense-object (dharma-viṣaya), known by the solitary consciousness (mano-vijñāna-eka-citta); it cannot know material form. This subjectively imagined realm, this mental sense-object, is contacted and known by the manas. When the manas considers it important, it alerts the mind consciousness to know it. The manas knows a great many dharmas but cannot express them, and the mind consciousness has no way to know what the manas knows, so the mind consciousness does not know. Some people then say "I don't know," but in fact the manas does know.

Sneezing is a sudden event; the mind consciousness has no mental preparation for it, so it is initiated by the manas. When a ghost comes, the mind consciousness does not know, but the body will shiver—this is triggered by the manas. When a major event is about to occur, the mind consciousness does not know what it is, but one will feel inexplicably happy or distressed—this is initiated and hinted at by the manas.