Selected Lectures on the Sūtra of the Collection of the Father and Son (Pitāputrasamāgamanasūtra) (24)

Original text: 大王。若色变坏。一切皆空。所以者何。是虚空界。本无尽故。安静不动。犹如涅盘。遍一切处。无有障碍。

Explanation: Great King, when material form deteriorates and perishes, it becomes empty nothingness—it becomes the realm of space. Why is it that when material form disappears, everything becomes empty? Because the realm of space is endless and boundless, everything can become empty. And space is by nature tranquil and unmoving, neither arising nor ceasing, neither increasing nor decreasing, like the nature of nirvāṇa. Space pervades all places, and there is no dharma that can obstruct it.

When things perish, they become empty space. For example, when a house is destroyed, that place entirely becomes empty space; when the earth is destroyed, the place of the earth entirely becomes empty space; when the trichiliocosm is destroyed, the entire trichiliocosm becomes empty space, and in that empty space there is nothing at all.

Space is tranquil and unmoving. Why is it unmoving? Because it is an unreal fabrication of nothingness. Material objects are also unreal, yet objects can be moved, whereas no one can move space even a little. If you build a very tall building in space, can you shift the space? Space does not move; no one can move space, because space has no substance and no boundaries—how could it be moved? Since there is no material form in space, it is nothing at all, sheer emptiness. We constantly need space and emptiness in order to move our bodies and place objects, because space has no obstruction; sentient beings need this quality of non-obstruction for moving about and storing things.

Some people say that air is also empty and should, like space, be boundless and immovable. But in fact air and empty space are vastly different. On the surface, air also appears to be without substance—invisible and intangible—yet instruments can detect the presence or absence of air. Air does contain matter: within it are the various gases we need, all of which are material form composed of the four great elements, and therefore air can flow and move. What sentient beings need from air is, above all, the oxygen it contains.