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

When sentient beings see form with their eyes, they believe they truly perceive form. In reality, external form is never directly perceived by sentient beings. What the eye faculty contacts is merely an illusion, a shadow. If the external form were truly pressed against the eye faculty, that external form would become invisible. If the eye could truly contact form, then seeing a sharp knife, with the knife tip contacting the eye, would inevitably injure the eyeball; seeing fire, with the fire contacting the eye, would inevitably burn the eyeball; seeing sand, with the sand contacting the eye, would inevitably irritate the eye. The eye faculty and form cannot actually make contact. Only when there is a certain distance between form and the eye faculty can the particles of the four elements constituting the form-dust be transmitted. The Tathagatagarbha, through contact between the eye faculty and the external form, transforms the external form into an identical shadow, enabling perception. If form were pressed against the eye faculty, leaving no spatial distance, form would not be seen. The nose faculty, tongue faculty, and body faculty, however, can directly contact the external smell-dust, taste-dust, and touch-dust without requiring a specific distance or space. The three consciousnesses (of smell, taste, and touch) can then arise to perceive smell, taste, and touch.

The shadow seen by the eye consciousness differs from the substance of the external form; it is not the actual object. It is transmitted via the retina and optic nerves to the sheng-yi faculty (the subtle organ governing vision) in the hindbrain. There, the Tathagatagarbha manifests the eye consciousness, which then discriminates the form-dust. This form appears identical to the external form, but in reality, it is only similar. Sentient beings mistake it for real, but it is actually all shadow. Similarly, the ear faculty, nose faculty, and tongue faculty also do not contact external sound, smell, or taste directly. It is the Tathagatagarbha that makes contact and then manifests the perception. All that is born (conditioned) is illusory and fabricated. This is the principle that all dharmas are created by mind. In short, all appearances are illusory. "If you see all appearances as non-appearances, then you see the Tathagata." If, amidst the various appearances of the five aggregates and the eighteen elements, one can find the Tathagatagarbha—which has no appearance and is not an appearance—that is to see the Tathagata. It is to realize the mind, attain enlightenment, and perceive the true reality.