Lectures on the Sūtra of the Collection of the Father and Son (Pitāputrasamāgamanasūtra) (49)

What is the internal space element?

Original text: 大王。云何内空界。若此身内。皮肉血等。显现增长。离质碍性。谓若眼窍。耳穴面门咽喉。咽啖饮食。所引滋味。于肠胃间。通彻而出。

Explanation: The Buddha said: Great King, what is the internal space element? If the skin, flesh, blood, and so forth within this body can manifest growth without the nature of material obstruction, that is the internal space element. If skin, flesh, sinews, and bones had the nature of material obstruction, they could not grow; they would be restricted. The eye sockets, the ear canals, the nostrils on the face, the throat, and other places that are empty and without substance constitute the space element; after swallowing and tasting food and drink, the food can pass along the esophagus into the stomach and intestines, and after being digested, it is expelled again. This passage—from the mouth to the esophagus to the stomach to the small and large intestines—is the space element, without material obstruction. If there were material obstruction, it would not be empty, and food could not enter the body, much less be expelled from it.

What is the space element? Here "space" refers to empty space, an emptiness containing nothing, the meaning of being empty and open. Where there is no skin, no blood, no flesh within the body, and no obstruction, that is emptiness. There is space within the blood vessels so that blood can flow; the windpipe is hollow so that we can breathe; there is the space element in the stomach and intestines so that food can move within them; there is space within the body so that gases, liquids, food and drink, urine and feces, and so forth can flow within it, so that cells can divide, and so that muscles, sinews, bones, and so forth can grow.

There are gaps and spaces within the body's cells, so that the various particles within a cell can move along their respective orbits within those gaps. There are gaps between the electrons, protons, ions, nucleons, and other particles within a cell, so that various physical and chemical reactions can occur between the particles, so that the cell can divide and grow, and so that the material body can undergo change. There are also gaps between cells, so that the oxygen breathed in can enter the body's cells to produce blood and flow within the body. The various gaps within the body are called the internal space element.

The six sense bases are form, sound, smell, taste, touch, and dharma. Each kind of material form is composed of the four great elements of earth, water, fire, and wind, and there is also the space element, which together compose material form. Thus material form is composed of the five great elements, and within material form there are spaces and gaps. The four great material elements within material form envelop the space; because the size of the space within material form differs, and the proportion occupied by the space element differs, the density of the material form differs, and the physical properties of the material differ.

Moreover, these six sense bases of material form are all manifested within the minds of the six consciousnesses, forming images at the supreme faculty in the back of the brain; therefore they belong to the inner six sense-objects, and the space at the supreme faculty belongs to the internal space element. From where does the internal space element come? When it comes, there is no place it comes from; when it goes, there is no place it goes to.