What is the Principle of Self-Repair of the Physical Body?

The material body possesses a self-repairing mechanism. When the body is damaged, it automatically mends itself; when internal organs are impaired, they are automatically repaired; when the body is exhausted, rest restores its energy; after surgery, incisions heal automatically; missing muscles, skin, and other tissues are automatically replenished. Lost blood can be regenerated; when the stomach and intestines lack food, the body automatically replenishes energy. The practice of regulating the material body through fasting utilizes this miraculous mechanism. What mechanisms are these? Whose function is this? When did this wondrous source of life begin to manifest?

In a past life, Master Kuiji entered samadhi for thousands of years awaiting the advent of Shakyamuni Buddha, yet missed it while in meditation. He then sought to enter samadhi again to await the advent of Maitreya Buddha. A human body sustained by the four great elements (earth, water, fire, wind) and nourishment remained in samadhi for thousands or even tens of thousands of years without eating or drinking, yet experienced no discomfort whatsoever, and could even enter samadhi for millions of years without perishing. What mechanism did Master Kuiji and others who attained longevity through meditation rely on to sustain life? It is said that an experiment showed thin people live longer than the obese, and those who eat less live longer than those who eat more. What principle underlies this?

Modern medical and health theories assert that one must sleep between 11 PM and 1 AM (the Zi hour), otherwise staying up late prevents internal organs from resting and recuperating, leading to bodily depletion. Yet, sitting in meditation at midnight causes no harm. The Buddha encouraged his disciples to diligently practice without rest during the first watch, middle watch, and last watch of the night. No records indicate the bhikkhus suffered physical discomfort; instead, their energy increased and their minds became more agile. Modern medicine also claims that skipping breakfast increases the risk of gallstones. However, during the Buddha's time, monastics ate only one meal a day at noon, and no records mention anyone developing gallstones. What mechanisms are responsible for these phenomena?

Basking in sunlight automatically replenishes the body's yang energy and vitality. If one focuses the mind in contemplation during this process, the replenishment increases, leading to better bodily regulation. Except for formless realm devas who lack a physical body and thus require no nourishment from the four great elements, all sentient beings with physical forms need sustenance from these elements. Sentient beings of higher realms require fewer and more subtle forms of the four great elements. Due to their meager merit, beings in lower realms must endure very coarse and inferior forms of the four great elements. Humans reside in the middle level of the desire realm, not among its highest forms of life. The four great elements they experience are relatively coarse, yet they mistakenly believe they enjoy superior substances and consume refined food, when in reality it is very crude. Beings in the Form Realm experience the highest and most subtle four great elements, followed by desire realm devas, and then immortals. All humans are inferior to devas in their experience; not only is their food coarse, it is also very impure, lacking good color, fragrance, or taste. Due to their karmic conditions, they perceive no fault in this and instead cling to it greedily, much like dogs delighting in feces or worms thriving in latrines.

All mechanisms for repairing the material body and all the four great elements it utilizes are functions of the tathagatagarbha (Buddha-nature). The tathagatagarbha creates these based on the sentient being's karmic seeds and merit. Because sentient beings have karmic connections to the human realm of desire, possessing the karmic seeds and conditions for being human or animal, the five aggregates (form, feeling, perception, mental formations, consciousness) require adequate nourishment from the four great elements to survive normally in the desire realm. If the four great elements in the material body are deficient, it disrupts the normal functioning of the five aggregates. The tathagatagarbha then automatically replenishes the missing four great elements according to karmic seeds and conditions. If karmic obstacles prevent replenishment, the five aggregates continue functioning imperfectly within an incomplete material body, manifesting the sentient being's unwholesome karmic conditions. For sentient beings with abundant wholesome karma, the tathagatagarbha automatically replenishes any deficiency in the material body. If replenishment is impossible, it signifies the karmic retribution of an incomplete or defective material body resulting from unwholesome karma.