Lectures on the Sūtra of the Collection of the Father and Son (Pitāputrasamāgamanasūtra) (50)

Original text: 若时业缘。引生六处。诸处生已。围绕空界。此说名入。内空界数。然彼空界。从何所来。又若方处。外所显现。离质碍性。名外空界。

Explanation: When karmic conditions ripen, the tathāgatagarbha gives rise to the six sense-objects: form, sound, scent, taste, touch, and dharmas. After these six sense-objects arise, they are encompassed within the space element; these spaces are all counted among the internal space element. But where do these spaces come from? Furthermore, if in various places outside the physical body, what manifests is devoid of the nature of material obstruction and contains no material form—this is the external space element.

The place outside the body where there is no material form is empty space, called the external space element. The external space element is boundlessly vast; all worlds of the ten directions are established within empty space. However many buddha-lands one wishes to establish, all can be established. Why is this so? Because empty space does not truly exist. If empty space truly existed, it would have fixed limits and boundaries and could not be boundless, and the establishment of buddha-lands could not exceed that range. But since empty space has no range or boundary, the trichiliocosms can be established at will—even if all sentient beings became buddhas, with each person having one trichiliocosm, the worlds would neither overlap nor be crowded. Because empty space has no boundary and is not material form, being without any thing, it can therefore contain all things. Such is the external space element.