What Is the Principle of the Physical Body's Self-Repair?

The physical body possesses a self-repairing function: when the body is damaged, it repairs itself automatically; when internal organs fail, they repair themselves automatically; when the body is exhausted, resting for a period of time restores its energy; after surgery, the incision heals automatically; missing muscle, skin, and so forth are automatically replenished. When blood is lost, it can be regenerated; when there is no food or drink in the stomach and intestines, the body can replenish energy on its own—the practice of abstaining from grain to regulate the physical body makes use of this miraculous mechanism. What mechanisms are all of these? Whose functions and operations are they? When did this miraculous source of life first appear?

Master Kuiji, in a previous life, entered meditative concentration and waited several thousand years for Śākyamuni Buddha to appear in the world, but missed Him while in samādhi, and so wished to enter concentration again and wait for Maitreya Buddha to appear. A human body sustained by the four great elements of food and drink, going without food or water for thousands or tens of thousands of years in samādhi, yet without the slightest discomfort, and able to remain in concentration for tens of millions of years without dying—by what mechanism do Master Kuiji and others who attain longevity through concentration sustain their lives? There is said to be an experiment showing that thin people live longer than fat people, and that those who eat less live longer than those with large appetites—what is the principle behind this?

Modern medical health theory holds that one must sleep between eleven o'clock and one o'clock at midnight (the hour of zǐ); otherwise, staying up late deprives the internal organs of rest and repair, and the body will be depleted. Yet sitting in meditation and entering samādhi at midnight causes no harm. In the Buddha's time, He encouraged His disciples to cultivate diligently, exerting themselves unremittingly through the first, middle, and last watches of the night, yet the monks were never heard to suffer any physical discomfort; on the contrary, their energy was more vigorous and their minds more acute in thought. Modern medicine also says that skipping breakfast makes one prone to gallstones. Yet in the Buddha's era, monastics ate only one meal a day at midday, and no one was ever heard to have gallstones. By the operation of what mechanisms are all these things?

When one sunbathes, the body automatically replenishes yang energy and vitality; if one can contemplate with single-minded focus, the replenishment will be greater and the body regulated even better. Apart from the devas of the formless realm, who have no bodies and thus need no nourishment from the material four great elements, all sentient beings with bodies require nourishment from the four great elements. The higher the realm of a sentient being, the fewer the material elements it needs, and the more subtle and refined those materials are. Sentient beings in lower realms, due to their meager merit (alpa-puṇya), must partake of extremely coarse and inferior material elements. Humans dwell in the middle stratum of the desire realm and are not among its most advanced beings; the material elements they partake of are all rather coarse and inferior, yet they believe that what they enjoy is high-grade substance and that they eat refined fare—when in reality it is very coarse. It is the devas of the form realm who partake of the highest and most refined four great elements; next come the devas of the desire realm, and after them the immortals. All humans fall short of the enjoyment of the devas: their food and drink are not only coarse but also extremely filthy, poor in color, fragrance, and taste. Because their karmic conditions are such, they do not feel anything is wrong; on the contrary, they are deeply attached to it—just as dogs delight in dung and worms delight in cesspits.

All the material elements of the four great elements that the repair mechanisms of the physical body partake of are the functions and operations of the tathāgatagarbha, produced by the tathāgatagarbha in accordance with sentient beings' karmic seeds and merit. Because sentient beings have karmic connections with the human world of the desire realm—having the karmic seeds and karmic conditions to be humans or animals—if the five aggregates are to survive normally in the desire realm, the physical body must be endowed with a sufficient supply of nutrients from the four great elements. If the four great elements in the physical body are deficient, the normal functioning of the five aggregates will be affected, and the tathāgatagarbha will, in accordance with karmic seeds and karmic conditions, automatically replenish the missing material elements. If karmic obstructions do not permit replenishment, then the five aggregates continue to function imperfectly with an incomplete physical body—this reveals the evil karmic conditions of sentient beings. For sentient beings whose wholesome karma is complete, whatever the physical body lacks, the tathāgatagarbha will automatically replenish; if it cannot be replenished, that is the evil karmic retribution of a body that is disabled and incomplete.