What Sustains the Physical Body in the Fourth Dhyāna?

When one cultivates to the fourth dhyāna, what phenomena occur in the body? Originally we breathe through the mouth and nose, but now the breathing stops; not only does breathing stop, the beating of the heart and pulse also stops, and the circulation of qi and blood ceases as well. What function do the heart and pulse serve? With each contraction and expansion of the heart, blood is delivered throughout the body, moistening and nourishing it. For the body to function normally, it needs qi and blood: qi drives the blood to circulate back and forth throughout the body. Blood is nutrition—the nourishment required by the machine of our body; without nourishment, the machine cannot run. Under ordinary circumstances, the faster this machine runs, the more nourishment it needs, the more ample the qi and blood required, and this demands a sounder heart function to ensure the body operates normally. This qi and blood are the four great elements the body needs, and the body is composed of these four great elements.

When meditative concentration becomes very deep, the body's operation slows down, the internal organs consume less nourishment, and not so much qi and blood are needed. When the body consumes only a minimal amount of nourishment, with slow metabolism, no longer requiring so much nourishment from the four great elements, the breathing stops, and the beating of the heart and pulse also stops. But at this time a small amount of qi and blood is still needed to sustain the existence and functioning of the living organism; it is simply that the coarse nourishment of the four great elements from breathing and eating is no longer required—the body absorbs the subtle particles of the four great elements from the surrounding air through its pores, and that is sufficient, and the waste in the body is also expelled through the pores. If a person in samādhi were placed in a sealed jar, they would suffocate to death from the lack of supply of the four great elements in the air.
The physical body is also composed of the four great elements. The physical body and the surrounding environment merge, interpenetrate, and mutually influence each other; material substances can also transmit particles of the four great elements to one another. Thus the four great elements of matter are constantly radiating outward, with a mutually perfuming quality. That is to say, external substances can, through every cell of the body, transmit these material particles, which are then absorbed and become the matter within the body; at the same time, the matter in the body also sends out particles of the four great elements. When this input and output reach a state of balance, the body is normal. The physical body can absorb the nourishment of the external four great elements to sustain its operation, so the external material environment can influence the physical body; likewise, the body's four great elements also radiate outward, so the body can also influence the external material environment. Thus there is a certain connection between the bodies of sentient beings, and they can influence one another—for now, let us call this phenomenon shared karma.

After sentient beings of the desire realm enter the fourth dhyāna, the body is nourished by the surrounding environment; sentient beings of the form realm in samādhi also rely on subtle four great elements for nourishment; sentient beings of the formless realm have no physical body, so they no longer need the nourishment of material four great elements. Without meditative concentration, the body consumes a great deal of the four great elements: the more bodily and mental activity, the more of the four great elements is consumed, and the more qi and blood are needed. People with many wandering thoughts consume more qi and blood and need to eat more food than others; those with few wandering thoughts consume less, and those with little bodily activity also consume less.

We should regard the physical body as a machine—in fact, it is a machine. The operation of this machine requires the consumption of nourishment; for it to function normally, nourishment must be replenished. The faster the machine runs and the greater the workload, the more nourishment it needs and the more energy it requires. The energy humans need comes from food and drink, from the material living environment; a machine needs lubricating oil to run. If you want this machine to last long, you must reduce its operation and reduce its workload. Because when a machine runs, there is wear and tear, which consumes the machine; the more it runs, the more it wears down, and the machine gradually grows old, with all its functions declining. It is the same with people: the greater a person's activity, the more the machine of the human body wears down, and the shorter the lifespan.

In meditative concentration, a person has very few wandering thoughts, or none at all, and the body is not active; the nourishment needed is minimal, the activity of the internal organs is reduced, and wear and tear is minimal. People with meditative concentration generally have healthy physical bodies and long lives. Modern people do not understand this; they all strive to live well, eat well, and play well, to enjoy food and drink, not knowing that the more one eats and the richer the nourishment one eats, the greater the workload of the body's internal organs and the more severe the wear and tear, and thus the worse the body becomes and the harder it is to live long. Therefore, eating a lot and eating highly nutritious food makes it very difficult for the internal organs to digest and absorb, requiring an enormous workload; the internal organs are heavily consumed, and longevity is not easy to attain. If you want longevity, you must reduce the body's wear and tear, reduce the workload, reduce the amount of activity, and further cultivate meditative concentration to reduce wandering thoughts.

Meditative concentration can calm the mind; the activity of body and mind is reduced, wear and tear is less, and life is long. Once the fourth dhyāna has been attained, the length of one's lifespan is decided by oneself. If one wishes to relinquish one's lifespan early and go to other worlds, such as heavenly realms, one can decide for oneself; if one does not wish to relinquish one's lifespan early, or wishes to live for a thousand or ten thousand years, that too is decided by oneself, because within the fourth dhyāna there are supernormal powers, and one can freely decide whether the body remains or departs; the time of birth and death is determined by oneself. But one still cannot be completely at ease, because self-view has not yet been eliminated and one cannot escape the cycle of the six realms of rebirth; it is only that the birth and death of this life are up to you. Without the fourth dhyāna, one has no freedom over the birth and death of this life; to relinquish one's lifespan early, one would have to commit suicide, and whether you wish to live an extra year, half a year, a day, or an hour is not up to you.

The body is merely an instrument for our cultivation. View it objectively, take good care of it, but do not cling to it, do not take it as self or as belonging to self; then you can make good use of the body to cultivate the Path, and at the very least, the body will not become a burden dragging us into endless birth and death in saṃsāra.