Selected Discourses on the Sutra of the Assembly of Father and Son (XXIV)

Original Text: Great King, if form deteriorates, everything becomes emptiness. Why is that? Because the realm of space is fundamentally inexhaustible. It is tranquil and unmoving, like nirvana. It pervades all places, without any obstruction.

Explanation: Great King, after material form deteriorates, it becomes nothingness, which is the realm of space. Why does everything become empty when matter disappears? Because the realm of space is boundless and limitless; everything can become emptiness. And space itself is fundamentally tranquil and unmoving, neither born nor destroyed, neither increasing nor decreasing, just like the nature of nirvana. Space pervades all places, and there is no phenomenon that can obstruct it.

When matter deteriorates, it becomes space. For example, when a house is destroyed, that entire location becomes space; when the Earth is destroyed, the entire location of the Earth becomes space; when a three thousand great thousand world system is destroyed, the entire three thousand great thousand world system becomes space. Within space, there is absolutely nothing.

Space is tranquil and unmoving. Why is it motionless? Because it is devoid of substance. Objects are also illusory, but objects can move, yet no one can move space itself. If one builds a very tall building within space, can it move the void? Space is unmoving; no one can move space because space has no substance and is boundless—how could it move? Within space, there are no material forms; it is utterly devoid of anything, completely empty. We constantly need space and emptiness to be able to move our bodies and place objects, precisely because space has no obstruction. Sentient beings need this unobstructed nature for movement and for storing things.

Some people say that air is also empty and should be as boundless and immovable as space. But in reality, air and space are vastly different. Air may appear insubstantial on the surface—invisible and intangible—but instruments can detect its presence or absence. Air is material; it contains various gases we need, all composed of the four elements as material forms. Therefore, air can flow. Sentient beings need air primarily for the oxygen within it.