Chapter Four: How to Utilize the Mental Faculty for Deliberation and Investigative Contemplation

I. The Meaning of "Constant" in the Mental Faculty's Constant and Deliberate Examination

Since the mental faculty is also a conditioned dharma subject to arising and cessation, how should the "constant" in its constant and deliberate examination be understood? "Constant" has two meanings: one signifies being unborn, unceasing, eternally existent and indestructible; the other signifies being extremely long-lasting and enduring, remaining unchanged for a considerable length of time, consistently so. The first kind is the constancy of the eighth consciousness, which is absolute, incomparable, unborn and unceasing. The second kind is the constancy of the mental faculty. The constancy of the mental faculty is relative, meaning that it perpetually maintains its function of examination without change as long as the mental faculty itself does not cease.

The constancy of the mental faculty can persist even after Buddhahood and will not cease. Therefore, as long as the mental faculty exists, its nature of examination exists. However, not extinguishing the mental faculty does not mean it cannot be extinguished. Arhats and Pratyekabuddhas can completely extinguish the mental faculty and enter the remainderless nirvana. Seventh Ground Bodhisattvas and above, as well as all Buddhas, can extinguish the mental faculty but intentionally choose not to. The mental faculty is produced by the eighth consciousness projecting seeds of consciousness; it relies on the eighth consciousness for its arising and functioning. It is not the originally unborn and unceasing dharma. Once the mental faculty no longer clings to worldly dharmas of the three realms, the eighth consciousness ceases to project the seeds for the mental faculty, and the mental faculty ceases. Therefore, the "constant" in the mental faculty's constant and deliberate examination is only relative to the six consciousnesses and cannot compare to the constancy of the eighth consciousness.

II. How to Mobilize the Mental Faculty's Examination Within Meditation

Within meditation, not using the thinking of the mental consciousness but employing the examination of the mental faculty is a practice of considerable depth, difficult for ordinary people to achieve. It requires a profound foundation in meditation and a certain level of contemplative practice skill. When meditation and contemplative practice reach a certain stage, one can shift from the thinking of the mental consciousness to the examination of the mental faculty. The thinking of the mental consciousness is relatively shallow, floating on the surface, and generally observable by anyone. For example, by introspecting what thoughts are present in the mind at this moment, one knows what one is currently thinking about, pondering, or planning. These thoughts are generally superficial and constitute the thinking of the mental consciousness.

Simultaneously, there is the support and guiding role of the mental faculty operating behind this. If concentration power and wisdom are insufficient, it is not easy to observe this, and one cannot clearly discern one's true inner thoughts. When the mind is cultivated to a very subtle state, one can observe that while the mental consciousness is thinking, there is a force operating behind it that plays a guiding role; that force and train of thought belong to the mental faculty. Once one discovers that force of the mental faculty behind the mental consciousness and can grasp the mental faculty, one should gradually diminish the thinking function of the mental consciousness. After diminishing it to a certain degree, one then relinquishes the thoughts of the mental consciousness. After relinquishing them, one must still maintain thoughts within the mind, maintaining the mental faculty's thinking activity, not allowing oneself to become completely thoughtless and devoid of mental activity. This is very difficult.

Within meditation, one must learn to diligently discover that force deep within the mind. It actually has thoughts, has mental activity, and is capable of thinking—that is the examination activity of the mental faculty. After discovering it, one diligently maintains that examination activity, not letting it disappear, and hands over the Dharma meanings contemplated by the mental consciousness to it, allowing it to continue examining alone. This belongs to a relatively deep state of investigative contemplation. Chan (Zen) meditation is like this; contemplating that the five aggregates are not the self employs such skill. In this way, the examination of the mental faculty is mobilized. This mode of thinking, this skill, is called the examination of the mental faculty.

Achieving this is inseparable from profound meditation. The skill in meditation needs to be very good, capable of relinquishing coarse distracting thoughts, and at a certain point, even fine distracting thoughts must be relinquished. Distracting thoughts are thoughts thinking about other insignificant dharmas, that is, miscellaneous thoughts and multiple thoughts. These thoughts are all disturbances to right mindfulness and must be eliminated, leaving only the Dharma that the mental consciousness needs to contemplate. Then, the thinking of the mental consciousness is also relinquished, allowing the mental faculty to examine this Dharma. The mental consciousness and mental faculty exchange roles in contemplating the issue. At this time, the mental consciousness still exists; it performs a very subtle function of discernment but does not engage in deep thinking, analysis, or reasoning. Instead, it allows the mental faculty to examine deeply, without language, words, or sound. This function of examination is not easy to observe when meditation and wisdom are insufficient.

This examining function of the mental faculty is also called the thoughts deep within the mind. Everyone's inner thoughts are divided into two kinds: one floats on the surface, being the shallow thoughts of the mental consciousness; the other is hidden deep within, being the deep-seated thoughts, that is, the thoughts of the mental faculty deep within the mind, representing one's true thoughts. For example, if I now tell someone I intend to do something, but in reality, I do not have such a thought, the expressed thought carries an element of perfunctoriness, while within there is another voice and thought. That thought is relatively concealed, and one does not wish others to know, so one uses the language of the mental consciousness to cover it up or divert attention.

Continuously introspect the inner mind of the mental faculty, grasp one's own inner mental faculty, and then transfer the Dharma originally held and contemplated by the mental consciousness to the mental faculty, letting the mental faculty hold onto it. In this way, the mental faculty can constantly and everywhere hold onto this Dharma, and the examining nature of the mental faculty becomes manifest. If the mental faculty agrees, the imprinting is successful; if the mental faculty does not accept it, the imprinting is not successful. Only when the skill is sufficient can it succeed.

In daily life, we all use the mental faculty and its function of examination, but we cannot observe it, cannot distinguish it, and do not know how to summarize, so we cannot clearly differentiate whether it is the thinking of the mental consciousness or the examination of the mental faculty. This requires increasing the skill in meditation and the wisdom of contemplative practice to clarify these issues. Only when meditation deepens can the mind become subtle, enabling one to discover the distinction between the mental consciousness and the mental faculty, and also to distinguish the inner voice from the surface voice, thereby understanding the state of the mental faculty's examination, grasping that examining nature of the mental faculty, and gradually learning to utilize it.

To reach this level, one must strengthen the practice of meditation, enhance the discerning power of wisdom, subdue afflictions, reduce distracting thoughts, and let the mind engage with the Buddha Dharma without clinging to worldly dharmas. As meditation is cultivated deeper and deeper, the mind becomes increasingly focused, distracting thoughts become fewer and fewer, to the point where one can relinquish distracting thoughts at will. When the mind becomes increasingly subtle and wisdom increasingly profound, the functional role of the mental faculty will be exercised very well.

After the physical body is subdued, reaching a state of balanced concentration and wisdom, one can directly use the examination of the mental faculty to resolve problems. When doubt regarding a particular Dharma is strong, directly hang that Dharma within the mind. Initially, the mental consciousness holds it, then the function of the mental consciousness is reduced and diminished, allowing the mental faculty to hold onto this Dharma. At this point, one enters a relatively deeper meditation, letting the mental faculty deeply examine this Dharma. The more focused the mental faculty's examination, the deeper the meditation; the deeper the meditation, the more focused, deep, and subtle the mental faculty's examination becomes. Finally, one can clarify this issue, simultaneously entering a state of samadhi, filled with Dharma joy, experiencing physical and mental lightness and ease, with meditative bliss arising. Samadhi is the state of balanced concentration and wisdom. After this state emerges, one's mental state throughout the day will be very good, both body and mind feeling very light and at ease.

III. How to Enter Meditation Quickly and Investigate Dharma Meanings

Now, I will introduce a method that allows one to enter meditation quickly while simultaneously engaging in investigation and contemplative practice, enabling everyone to swiftly enter the state of investigative contemplation.

To sever the view of self, the "I" within the five aggregates is crucial. Contemplate what exactly this "I" is. If contemplating while sitting, after sitting down and crossing the legs, adjust the breath—generally take several deep breaths—to ensure the Ren meridian in front of the body is unobstructed and the mind is clear, not dull. Then, single-pointedly raise the "I." Initially, the word "I" and its meaning appear in the mind of the mental consciousness. Then, let the mental consciousness transmit this doubt about "I" to the mental faculty. After handing it over to the mental faculty, the mental consciousness's thoughts should gradually disappear, feeling as if the mind is empty, without any thoughts.

Yet the mind is not truly empty; the mental faculty is suspending this doubt about "I," feeling very deep, seemingly present yet absent, as if graspable yet not quite graspable. At this time, the mental consciousness should not stir thoughts; let the doubt about "I" in the mental faculty's mind become increasingly clear and deep, as if carved firmly into the heart. In this way, meditation arises, single-mindedly investigating the "I." At this point, the mental consciousness seems to disappear as if stupefied, but the mental faculty is not like that. The mental faculty's kind of examination is not easy for the mental consciousness to grasp or perceive, but concentration power increases. When the mind is subtle, one can still perceive that deep examination of the mental faculty, continuous and unbroken, extremely deep and subtle.

At this time, the mind should be extremely still; apart from that doubt about "I," there should be nothing else in the mind. This is both profound meditation and the skill of single-minded investigation and contemplative practice, balanced concentration and wisdom, impartial and centered. Because the meditation is deep, the body feels extremely comfortable, and the mind is very clear. Within this state, if one feels dull or about to enter a thoughtless concentration, the mental consciousness should remind the mental faculty again, raising the word "I," placing all attention on the word "I," keeping the mind neither empty nor scattered. An hour will pass very quickly. When rising from the seat, one feels refreshed and clear-headed, full of energy, and mentally joyful. The results examined by the mental faculty may be clear and definite, or may not be very clear and definite, but there is confidence within, much clearer than before.

As long as a clear answer and result have not yet appeared, the samadhi of balanced concentration and wisdom has not arisen, and the view of self has not been severed, continue applying effort in this way in the future until satisfactory results are achieved. Based on this method, then contemplate other unclear Dharma meanings in sequence. For example, contemplate the aggregate of form, contemplate the aggregate of feeling, contemplate the aggregate of perception, contemplate the aggregate of mental formations, contemplate the six sense bases, six sense objects, and six consciousnesses. Contemplate any Dharma meaning in this way to fundamentally eliminate doubts and sever the three fetters.

At the beginning of sitting, the mental faculty has no experience and cannot enter the role of the examiner. Even after entering the role, it may not know what to examine. This requires the mental consciousness to prompt and guide the mental faculty towards the direction of examination, yet the prompting should not be excessive. Each time, only a little prompting is needed, vague and indistinct. Once the mental faculty can examine with concentration, it will become increasingly clear and penetrating. After emerging from meditation, the mental consciousness should organize and summarize, contemplating all the Dharma meanings examined by the mental faculty once more. This can deepen the impression and provide confirmation.

Applying effort like this while sitting in meditation, one should also apply effort similarly while walking and doing things, although it is more difficult, requiring more dispersed energy, and taking much longer to achieve the same effect. The methods are identical. When the mental faculty's doubt is deep, one can concentrate on applying effort while walking, standing, sitting, or lying down. Why is it so? What mystery lies within? Then one will know the reason why. Once the origin and development of the Dharma are thoroughly investigated, realization is attained.

IV. How to Enter Meditation Through Wisdom

After sitting down and adjusting the breath, bring forth the question requiring contemplation in the mind. After the mental consciousness clarifies the connotation of the question, do not analyze, reason, speculate, or imagine; do not engage the superficial thinking of the mental consciousness. Mobilize the mental faculty, deeply implanting the question into the mind of the mental faculty, letting the mental faculty suspend this question. At this time, there are no words, language, or sounds in the minds of either the mental consciousness or the mental faculty. In this way, profound meditation appears, and concentration power arises. The mental faculty is in a state of examining the problem. If the physical body has no obstructions and the mind has no distracting thoughts, the more the mental faculty examines, the more focused it becomes; the deeper the meditation, the more wisdom unfolds; the state of body and mind becomes increasingly harmonious, and the spirit more joyful.

Examining Dharma meanings within such profound meditation is completely equivalent to profound contemplative practice, Chan meditation, and investigative contemplation. The understanding of Dharma meanings in the mind will become increasingly clear. Once one can examine it penetratingly, the mind will be very certain, free from doubt, eliminating perplexity. If one uses this method to contemplate the content of severing the view of self and matters related to realizing the self-nature mind, once the investigation and contemplation become clear, the three fetters will be severed, and the fetter of doubt will certainly be broken. If it is reasoned out or speculated upon by the mental consciousness, and the mental faculty does not understand it clearly, the fetter of doubt will not be broken, karmic obstacles will not be removed, and the cycle of birth and death cannot be ended.

The vast majority of people only know how to use the superficial thinking mode of the mental consciousness; they do not know how to use the deep examination mode of the mental faculty. Therefore, they do not know how to apply effort in Chan meditation and investigation, leading to emotional understanding and intellectual comprehension, where doubt does not cease and the fetter of doubt remains unbroken. When encountering disturbances, doubt flares up intensely, and the Dharma meanings previously deduced may be overturned. Even if not overturned, it is not actual realization or direct experience, having no practical use. Therefore, nowadays, among many who consider themselves awakened, the ratio of false awakening is like the purity rate of gold, or even higher, certainly not less. This is the current state in the Dharma-ending age. No matter how many people feel unwilling, this is the fact, corresponding and matching the faculties of sentient beings and the era background of the Dharma-ending age. It will not be better than the True Dharma Age or the Semblance Dharma Age; absolutely not.

V. How to Induce Meditation Through Wisdom

Inducing meditation through wisdom allows for very fast entry into concentration. The prerequisite is that the foundation in both meditation and contemplative practice is relatively good, so that upon sitting down, the mind can quickly eliminate distracting thoughts and deluded thoughts. Contemplate a Dharma meaning in the mind, its connotation clear, enabling swift and focused contemplation, becoming increasingly focused. Diminish and eliminate the obvious thinking of the mental consciousness, but the mental faculty within the mind is still contemplating and examining, without language, without sound, without words, contemplating very deeply. When first practicing, it may feel forced and difficult to endure. Once accustomed, entry into meditation is very fast, both body and mind feel very comfortable, the whole body feels clear and unobstructed, the mind is lucid. After emerging from meditation, body and mind are joyful, full of energy, far more effective than sleep.

During the mental faculty's examination process, one can observe that the mental faculty does not reference other Dharma meanings, does not compare them with other Dharma meanings, nor does it speculate or imagine. Therefore, the mental faculty does not have the modes of thinking involving inference or non-valid cognition; its thinking is entirely based on direct perception. Once a conclusion is reached, it is wisdom based on direct perception, relatively true, not easily overturned or regretted, and trustworthy. Thinking with the mental consciousness is not like this. Because the mental faculty's examination has no language, words, or sound, if the conclusion it examines needs to be formed into language, words, or sound, it requires the help of the mental consciousness. The mental consciousness needs to be awakened, the conclusion transmitted to it, and after the mental consciousness understands it, it organizes language, forming words and sounds. The language and words formed will be very concise, clear, penetrating, and precise.

This process is relatively complex and slow, much slower than the mental consciousness thinking alone. But although slow, it is deep, thorough, and precise, representing one's true wisdom. Therefore, if a person thinks very much with the mental consciousness, primarily relying on mental consciousness thinking, although their writing and speaking may be fast, the content may be abundant and complex, the quality cannot be guaranteed, let alone guaranteed to be wisdom based on direct perception. Components of inference and non-valid cognition will be numerous, referenced content may be more, memory can be good, and expression can be good, but it does not fully represent one's true wisdom. Therefore, good food is worth waiting for and is not afraid of being slow; exquisite flavor is the most enjoyable.

VI. How to Enter Meditation Quickly

While sitting in meditation, contemplating Dharma meanings allows for faster and deeper entry into concentration than silently reciting the Heart Sutra or mantras, faster than entering concentration by regulating the breath, and faster than using other methods to enter concentration. This is the case for people with sharp faculties whose afflictions are slight and distracting thoughts are few, because these people already have a foundation in meditation cultivation, and preliminary expedient methods can be omitted. For beginners in concentration whose minds are heavily clinging and full of thoughts, the more they contemplate, the more chaotic the mind becomes; without meditation, it is merely miscellaneous thinking that disturbs the mind. Therefore, wait until there is a foundation in meditation before contemplating. When I sit down, once my legs are crossed, I use no preliminary methods at all, directly entering deep contemplation without the thinking of the mental consciousness; it is all the examination of the mental faculty. After crossing the legs, first focus on the Dharma to be contemplated, then stabilize the mind on that Dharma without moving, without a single distracting thought. This is the state of the mental faculty engaging in Chan meditation and investigation.

The mental faculty's examination is deep and slow but thorough. The mental consciousness's thinking is fast and shallow, not thorough or penetrating. The thinking of the mental consciousness is a preliminary expedient method, the purpose being to induce the mental faculty's contemplation. Initially, this is a necessary process to go through. Within the mental faculty's examination and investigation, there is almost no acquired knowledge; it does not increase the volume of knowledge, yet it is very interesting, possessing a deep sense of exploratory interest, a hazy joy of discovering something. What is developed is the wisdom within one's own mind-field. This wisdom is not obtained from outside; what is obtained from outside is knowledge. Reaching this level, one no longer feels tired. I can sit for a morning or even a whole day; it's just that there are worldly concerns, forcing me to rise from the seat.

VII. The Benefits of Using the Mental Faculty for Examination

Question: I seem to understand how to use the mental faculty for examination. It is a kind of mental activity that cannot be done by "thinking," because as soon as one "thinks," the mental consciousness participates. Once the mental consciousness participates, that state becomes less deep and subtle. Is that so? This state lasts a short time. When the examination encounters a sticking point in the problem, I use the mental consciousness to "think," and immediately the state becomes less deep and subtle. Also, while sitting in meditation, when observing the state of the body with concentrated awareness, a feeling arises of not having this physical body, only a body constituted by subtle sensations and consciousness, very insubstantial. Suddenly, there is a thought that the things seen in daily life are merely images and projections, manifested. There is such a feeling, but after emerging from meditation, looking around, everything still seems so real.

Answer: You now can roughly distinguish whether it is the mental consciousness thinking or the mental faculty examining during sitting meditation. The method is also used correctly; it's just that the skill is not yet proficient and natural. Take it slowly, gradually deepening the foundation. When contemplating the Buddha Dharma in stillness, indeed, when using the mental faculty, the mind is very deep and subtle; when using the mental consciousness, it feels somewhat shallow, as if separated by a layer, not deep or penetrating enough.

While sitting in meditation, when observing the physical body with concentrated attention, concentration power increases. When concentration deepens, awareness instead becomes subtle, the perception of the physical body disappears, and the mind becomes empty. Concentration power can make the mind subtle and precise, often enabling the observation of things not usually observable, discovering the true nature of things, thereby penetrating and realizing the truth. Then, feeling in meditation that seeing some things seems like images, not so real, this is a correct view. On the basis of this correct view, if one further refines the skill to proficiency, there is hope for realization.

After realization, upon emerging from meditation, one will no longer mistake illusory dharmas as real. Before realization, the view is merely a view; it cannot change anything. However, a correct view does involve some departure from false cognition, tending towards discovering the true nature of things. Maintaining and deepening this state of practice allows one to see more clearly how all phenomena and principles are extremely illusory and unreal. When the causes, conditions, and time are sufficient, it is possible to realize emptiness. Therefore, the realization of all dharmas occurs within profound meditation. Even during activity, there is concentration power, which all stems from the meditation skill cultivated while sitting, an extension and continuation of the concentration attained in stillness.

VIII. How to Accord with Principle and Enter Principle

The five aggregates, eighteen elements, and twelve sense fields arise from the aggregation of various causes and conditions; they cease when the causes and conditions disperse. How should this principle be realized? The mental consciousness thinking about it can roughly understand it, but you yourself also know this is not true understanding; deep and precise comprehension of its meaning is still needed, with reason and basis. This requires, within meditation, to suspend this principle in the mind, letting the mental faculty contemplate it single-mindedly, constantly and continuously examining it meticulously. The mental faculty's examination is subtle, continuous, and unattached to objects, possessing a certain height and depth, called "viewing from a high vantage point."

IX. A Mind Like a Wall Can Enter the Path

Question: One night, I entered meditation within a dream. My mind was vividly clear; the surrounding people and things were all distinctly known, yet I felt as if these people and events had no connection to me whatsoever and could not affect me. It was as if I was in a vacuum; there was not a single distracting thought in my mind, only the thought of contemplating a Dharma meaning (I don't remember the specific Dharma meaning). It was like a solitary sun shining in the sky without a single cloud. Simultaneously, my whole body and mind felt incomparably light, at ease, and comfortable. I finally understood that meditation feels so comfortable! After waking up, I could still feel that comfort. If one had such meditation, one truly would no longer crave worldly pleasures. That feeling was extremely light, at ease, and free, incomparable to the pleasures of the five worldly desires. Please teach me, Master: Why did this state, which I have never experienced in reality, appear in a dream?

Answer: This kind of dream state is the state of engaging in Chan meditation within concentration, possessing both concentration and wisdom, the dual practice of śamatha (calm abiding) and vipaśyanā (insight). You practiced this kind of meditation in a past life; it is the state of the mental faculty having experienced it before, possessing memory. Now, your mind yearns for it, still wanting to experience this meditative state. But in this present life, you are relatively busy, and the causes and conditions for cultivating concentration are not complete. Therefore, the mental faculty has no choice but to dream, enjoying the joy of meditation and Chan contemplation in the dream. It seems the mental faculty is also quite pitiful and helpless. Modern society is too chaotic and bustling; it is actually impossible to shut out the hectic life and wholeheartedly cultivate the path.

In the dream, the mental consciousness was in a clear, thoughtless state, vividly clear without thoughts. It was likely in the state of the "access to concentration" (anāgamya-samādhi, "not yet reached" dhyāna). But the mental faculty was functioning in the state of investigating Dharma meanings, contemplating the Buddha Dharma. Only by contemplating the Buddha Dharma in this way can fundamental problems be resolved and realization attained. Chan meditation and investigation are precisely this state: not a single distracting thought in the mind, external objects not entering the mind, the mind unmoving like a copper wall or iron fortress. The Patriarch Bodhidharma said, "A mind like a wall can enter the path." This is what he meant. If concentration and contemplation do not reach this level, do not expect to realize the path.

This state of examination and investigation by the mental faculty can only arise and remain continuous under extremely quiet environmental conditions; only then can the deep, extremely deep principles of Dharma be investigated. Therefore, true practitioners shut out all external conditions; it is absolute solitude and loneliness. Cultivating the path is fundamentally a great undertaking done by a solitary individual; it cannot be accomplished amidst clamor and companionship. Those who cannot endure loneliness cannot walk the true path of cultivation. Meditation can subdue and eradicate afflictions, can obtain lightness, ease, joy, and happiness. Nothing is more joyful than cultivating the path. Therefore, those with meditation do not like worldly dharmas; their minds do not cling to the world, do not pursue wealth, sex, fame, food, sleep, fame and gain, nor do they delight in power, status, or position. Craving worldly dharmas is truly unwise.

Some say that as long as one contemplates Dharma meanings without distracting thoughts for just over ten minutes, one can realize the fruit and realize the mind. Such a statement is utterly reckless. Contemplating the Buddha Dharma for such a short time simply cannot produce very deep and subtle contemplation, nor can one cultivate to the state of balanced concentration and wisdom in Chan meditation. It is like wanting to boil a large pot of water, which requires an hour. If one boils it for five or ten minutes and then stops, resuming the next day, continuing like this for a year or ten years, one still cannot boil this pot of water. Treating the Buddha Dharma so frivolously, playing with it, bears quite unwholesome karmic retribution. If the Buddha Dharma were so easy to cultivate and realize, how could there be so many sentient beings in the three evil destinies? People in the world like to seek shortcuts, but the result of seeking shortcuts harms themselves. You reap what you sow. To achieve something, one must let go of body and mind and be willing to put in the effort.

X. Why Does the Mental Faculty's Constant and Deliberate Examination Still Require Sleep?

Sleep is the cessation of the six consciousnesses, allowing the physical body and the six consciousnesses to rest. However, the mental faculty neither ceases nor rests. Therefore, sleep does not affect the mental faculty's constant and deliberate examination, and the mental faculty's constant and deliberate examination does not affect sleep.

Sleep is for restoring the physical body's energy, eliminating the physical body's fatigue, enabling the six consciousnesses to function normally and effectively. The mental faculty regards the physical body as belonging to itself, regards the six consciousnesses as belonging to itself, regards the five aggregates and eighteen elements as belonging to itself, and also relies on the eighth consciousness to know the state of the physical body moment by moment. The activities of the six consciousnesses consume energy. To reduce energy consumption, the mental faculty decides not to let the six consciousnesses continue their activities, actively shutting down the six consciousnesses' discernment of the six sense objects, no longer wishing to know the sense objects, relying only on the mental faculty's own knowing. As energy continuously accumulates and vitality is restored to a certain level, the mental faculty decides to wake up, contact the sense objects, and continue the activities of the five aggregates.

If the physical body becomes fatigued, sleep is needed to restore energy. The mental faculty will then decide to sleep, not allowing the six consciousnesses to continue their activities. The mental faculty itself wishes to shut off the sense objects, not to know them. In this way, the five sense consciousnesses and the mental consciousness gradually cease. Therefore, it is not that the mental faculty needs sleep, but that the physical body needs rest, replenishing energy and restoring vitality. This is precisely the result of the mental faculty's constant and deliberate examination. However, sleep does not affect the mental faculty's constant and deliberate examination. The mental faculty can continue examining during sleep and can also manifest dreams, examining within the dreams.