Spiritual Practice Is Sweeping the Mind-Ground.

The manifestation of the subjectively imagined realm occurs when the manas grasps at and attends to mental sense-objects (dharmadhātu) and then gives rise to a thought; the tathāgatagarbha then produces the solitary consciousness (mano-vijñāna-eka-citta) to carry out the manas's instruction. Whatever dharma the manas attends to, that is the dharma upon which the solitary consciousness arises, and thereafter it operates according to the manas's directives. Only after the mind consciousness gives rise to a thought does knowing occur—knowing what the dharma is. This dharma is a mental sense-object resembling information, having nothing to do with the five sense-objects; it may be an idea or concept, a memory, a longing for the future, or the deliberation, analysis, and judgment of a problem. When the manas wants to recall something, the mind consciousness recollects people and events of the past; when the manas wants to know the meaning of a certain sentence, the mind consciousness deliberates and analyzes that sentence; when the manas wants to consider the next day's itinerary, the mind consciousness deliberates the arrangements for the next day. 

The arising of thoughts in the solitary consciousness is drawn forth by the manas, arising, ceasing, and moving in accordance with the manas's thoughts and ideas. For example, when the manas thinks of a person, the eighth consciousness immediately manifests the dharmas related to that person. After the manas makes contact and deliberates, it makes a decision to think it over, and so the solitary consciousness appears, attending to the dharmas of that person—making contact, feeling, perceiving, and volition. Thus, after the manas knows, a decision will follow. Then the solitary consciousness may continue to operate in depth, or it may vanish from this dharma and appear on some other dharma that the manas grasps at. 

The manifold stray thoughts of the solitary consciousness arise from the various graspings of the manas. At the very moment a thought first arises, no realm has yet manifested; the first instant is knowing that a thought has arisen, and only then does the image of the realm appear—there is a process between the arising of the thought and the manifestation of the realm. The realm was there all along, but without the mind consciousness it cannot be known. When the mind consciousness appears, in the first and second instants its discernment is incomplete and unclear; only in the third and fourth instants can its discernment reach a conclusion, producing an outline of the dharma; only afterward comes deliberation and analysis, and only then is the dharma fully understood. Most of the stray thoughts in the mind are things experienced in the past, called "habitually experienced realms" (曾习境). This shows that the manas often grasps at dharmas intentionally or unintentionally, with strong habitual force; the mind is not empty and cannot let go of all the people, events, things, and principles it has experienced, keeping them circling in the mind, unwilling to discard them—the mind is piled full of garbage, filthy and dirty, never knowing to clean and tidy it up.

Cultivation means regularly cleaning and tidying up the hygiene of the mind—a thorough sweeping and cleansing—maintaining the purity of the mind-ground so that the chamber of the mind can radiate great light. The cleaning is led and supervised by the mind consciousness, with the manas's consent; still, it is the mind consciousness that does the cleaning. Both devising plans and carrying out tasks are the work of the mind consciousness; the manas only needs to nod, give orders, and make the final decision.