The Profound Consciousness-Only Meaning of the Diamond Sutra (39)

When sentient beings' eyes see form, they believe they are truly seeing form; in fact, sentient beings have never seen the external form. What the eye faculty contacts is only a false image, a shadow. If external form were truly pressed against the eye faculty, one would not be able to see that external form. If the eye could truly contact form, then when the eye sees a sharp knife, the tip of the knife touching the eye would certainly pierce and injure the eyeball; when the eye sees fire, the fire touching the eye would certainly burn the eyeball; when the eye sees sand, the sand touching the eye would certainly get into and irritate the eye. The eye faculty and form cannot make contact; only when there is a certain distance between form and the eye faculty can the four great elements' particles of the form sense-object be transmitted. The tathāgatagarbha, through the eye faculty contacting the external form, transforms the external form into an identical shadow, and only then can it be seen; if the form were pressed against the eye faculty, with no spatial distance, form could not be seen. The nose faculty, tongue faculty, and body faculty, however, can directly contact the external scent objects, taste objects, and touch objects, without needing a certain distance or space, and the three consciousnesses can then be generated to discern scents, tastes, and touches.

This shadow seen by the eye consciousness differs from the matter of the external form; it is not the actual object. Only then can it be transmitted through the retina and the conducting nerves to the supreme faculty (indriya) in the back of the brain that governs vision, where the tathāgatagarbha produces the eye consciousness, and the eye consciousness then discerns the form sense-object. This form appears to be the same as the external form, but in reality it is only similar; sentient beings take it to be real, but in fact it is all shadows. By the same token, the ear faculty, nose faculty, and tongue faculty likewise cannot contact external sounds, scents, or tastes; it is all the tathāgatagarbha that makes contact and then manifests them. Whatever is born is illusory and transformed; this is the principle that all dharmas are created by the mind alone. In short, all marks are false and illusory; if one sees that all marks are no-marks, one then sees the Tathāgata. If, among the various marks of the five aggregates and eighteen realms, one can find a tathāgatagarbha that has no mark and is not a mark, that is seeing the Tathāgata—seeing the mind, realizing enlightenment, and beholding ultimate reality.