The Profound Meaning of Yogācāra in the Diamond Sutra (XXV)

Now, let's examine the eighteen dhātus (realms), which include the six sense faculties (ṣaḍ indriyāṇi), the six sense objects (ṣaḍ viṣayāḥ), and the six consciousnesses (ṣaḍ vijñānāni). The six sense faculties are the eye, ear, nose, tongue, body, and mind faculties. The eye faculty is divided into the gross sense organ (audārika indriya) and the subtle sense organ (sūkṣma indriya). Composed of the four great elements (mahābhūtāni)—earth, water, fire, and wind—the part resembling a grape cluster outside the body is called the gross sense organ, also known as the external eye faculty. Connected by the optic nerves in the posterior part of the brain, the visual cortex in the occipital lobe, which governs vision, is the subtle sense organ; it is the basis upon which eye consciousness arises, and it is there that eye consciousness originates. If the subtle sense organ is damaged, even if the gross eye organ is intact, one cannot see forms; this is called being functionally blind. The eye faculty is created by the tathāgatagarbha absorbing the four great elements (nutrients) from the mother's body at the stage of the fertilized egg. It is a phenomenon subject to arising and ceasing, impermanent, illusory, is suffering, and is devoid of self.

The ear faculty is divided into the gross sense organ and the subtle sense organ. The part visible externally on the body, resembling a newly curled leaf, is called the gross sense organ. The auditory cortex in the posterior part of the brain, connected by the auditory nerves and governing hearing, is called the subtle sense organ; it is the basis upon which ear consciousness arises, and it is there that ear consciousness originates. The ear faculty is created by the tathāgatagarbha absorbing nutrients from the mother's body during the embryonic stage. It is a phenomenon subject to arising and ceasing, impermanent, illusory, is suffering, and is devoid of self.

The nose faculty is divided into the gross sense organ and the subtle sense organ. The gross sense organ is on the surface of the body, resembling two olfactory bulbs or suspended gallbladders; it is the receptor for scents. After scent is received, it is transmitted via the olfactory nerves to the cerebral cortex, where nose consciousness arises, enabling the discrimination of fragrant and foul odors. The cerebral cortex in the posterior part of the brain is the subtle sense organ, governing the sense of smell; it is the basis upon which nose consciousness arises. The nose faculty is also created by the tathāgatagarbha at the stage of the fertilized egg. It is subject to arising and ceasing, impermanent, illusory, is suffering, and is not the self.

The tongue faculty is composed of the four great elements—earth, water, fire, and wind—and is produced by the tathāgatagarbha at the stage of the fertilized egg. It is divided into the gross sense organ and the subtle sense organ. The part visible externally when the mouth is open, resembling a half-moon shape, is the gross sense organ; it is the receptor for taste. Taste sensations are transmitted via the gustatory nerves to the cerebral cortex, where the tathāgatagarbha gives rise to tongue consciousness, enabling the discrimination of various taste objects. The cerebral cortex in the posterior part of the brain is the subtle sense organ. The tongue faculty is subject to arising and ceasing, illusory, impermanent, is suffering, and is devoid of self.

The body faculty is created by the four great elements—earth, water, fire, and wind—and is an accumulation of thirty-six components. The twelve external forms are: hair on the head, body hair, nails, teeth, eye discharge, tears, saliva, spit, feces, urine, grime, and sweat. The twelve bodily containers are: skin, outer skin (dermis?), blood, flesh, sinews, veins, bones, marrow, fat, grease, brain, and membranes. The twelve internal organs are: liver, gallbladder, intestines, stomach, spleen, kidneys, heart, lungs, raw viscera, digested viscera, red phlegm, and white phlegm. Every part, from the skin and muscles to the internal organs, possesses sensation. Sensations are transmitted via nerves to the spinal cord and then to the cerebral cortex, where body consciousness arises, enabling the perception of touch. The cerebral cortex is the subtle sense organ, located in the posterior part of the brain. If this part is damaged, the entire body becomes paralyzed, turning into a vegetative state. The gross sense organ resembles a barrel of flesh, visible to the human eye, and is called the gross sense organ. The body faculty is subject to arising and ceasing, impermanent, illusory, is suffering, and is devoid of self.