The Profound Meaning of Consciousness-only in the Diamond Sutra (25)

Next, let us look at the eighteen dhātus, which include the six faculties, six sense objects, and six consciousnesses. The six faculties are the eye, ear, nose, tongue, body, and mental faculties. The eye faculty is divided into the gross faculty and the supreme faculty (indriya), both composed of the four great elements of earth, water, fire, and wind. The grape-like structure located on the outside of the body is called the gross faculty, also known as the external eye faculty. Connected via the optic nerves to the occipital cortex at the back of the brain, which governs vision, is the supreme faculty; it is that upon which the eye consciousness depends, and it is there that the eye consciousness arises. If the supreme faculty is damaged, even if the eye faculty is intact, one cannot see forms—this is called being blind with open eyes. The eye faculty is formed at the embryonic stage when the tathāgatagarbha absorbs the four great elements of earth, water, fire, and wind (nutrients) from the mother's body. It is a dharma of arising and ceasing, an impermanent dharma, a false and illusory dharma; it is suffering, and thus it is not-self.

The ear faculty is divided into the gross faculty and the supreme faculty. The gross faculty is what everyone can see on the outside of the body, resembling a newly rolled leaf; connected via the auditory nerves to the cerebral cortex at the back of the brain that governs hearing is the supreme faculty, upon which the ear consciousness depends, and it is there that the ear consciousness arises. The ear faculty is formed in the embryo by the tathāgatagarbha absorbing nutrients from the mother's body. It is a dharma subject to arising and ceasing, an impermanent and false dharma, suffering and devoid of self-nature.

The nose faculty is divided into the gross faculty and the supreme faculty. The gross faculty is on the surface of the body, resembling a pair of olfactory bulbs or a hanging gallbladder; it is the receptor for odors. After receiving an odor, the olfactory nerves transmit it to the cerebral cortex, where the nose consciousness arises, and only then can one distinguish fragrant from foul. The cerebral cortex at the back of the brain is the supreme faculty, governing the sense of smell, and it is that upon which the nose consciousness depends. The nose faculty is also formed by the tathāgatagarbha at the embryonic stage; it is subject to arising and ceasing, impermanent, false and illusory, suffering, and not the self.

The tongue faculty is composed of the four great elements of earth, water, wind, and fire, and is transformed and generated by the tathāgatagarbha at the embryonic stage; it is divided into the gross faculty and the supreme faculty. On the outside of the body, visible upon opening the mouth, the half-moon-shaped structure is the gross faculty; it is the receptor for taste. Taste sensations are transmitted via the gustatory nerves to the cerebral cortex, where the tathāgatagarbha generates the tongue consciousness to discriminate the various taste objects; the cerebral cortex at the back of the brain is the supreme faculty. The tongue faculty is subject to arising and ceasing, false and illusory, and impermanent; it is suffering, and thus it is not-self.

The body faculty is formed from the four great elements of earth, water, fire, and wind, an aggregation of thirty-six components. The twelve external features: hair, body hair, nails, teeth, eye discharge, tears, nasal mucus, saliva, feces, urine, grime, and sweat. The twelve bodily constituents: skin, flesh, blood, muscle, sinews, vessels, bones, marrow, fat, lard, brain, and membranes. The twelve internal organs: liver, gallbladder, intestines, stomach, spleen, kidneys, heart, lungs, the upper viscera, the lower viscera, red phlegm, and white phlegm. The skin and muscles of every part, down to the internal organs, all have sensation, which is transmitted via the nerves to the spinal cord and then to the cerebral cortex; only when the body consciousness arises there can tactile contact be perceived. The cerebral cortex is the supreme faculty, located at the back of the brain; if this part is damaged, the entire body becomes paralyzed, resulting in a vegetative state. The gross faculty is like a barrel of flesh, visible to the human eye, and is therefore called the gross faculty. The body faculty is subject to arising and ceasing, impermanent, false and illusory, and suffering; it is not-self.