The inner mental sense-object is the image of the outer mental sense-object

Question: Do the shapes and forms of material objects—such as height, size, and posture—already exist in the external world, or do they only appear in the supreme faculty (rūpa-prasāda)?

Answer: The tathāgatagarbha manifests all dharmas as they truly are. If something does not exist in the external world, how could the tathāgatagarbha rely upon it to manifest an inner dharma? On the five external sense-objects of form, sound, smell, taste, and touch, there is a roughly fixed amount of the four great elements, which continuously radiate particles of the four great elements outward. The particles of the four great elements of each material form are different. These particles cannot possibly pile up in a disordered manner; their arrangement must certainly be ordered and rule-governed, and thus there is shape. Since there is shape, there is the mental sense-object of visible form (saṃsthāna-rūpa); by the same reasoning, there must be the mental sense-object of expressive form (vijñapti-rūpa), and some also require the mental sense-object of unexpressed form (avijñapti-rūpa). Therefore, mental sense-objects exist outside the supreme faculty; they have long existed. They are dharmas of material form produced by the tathāgatagarbha from the four great elements; they are real dharmas, already existing in the external world in the first place, and the tathāgatagarbha then relies upon them to manifest the inner material sense-objects, which the six consciousnesses can then discern by taking them as object.

The tathāgatagarbha manifests the myriad dharmas just as a mirror displays images, manifesting images identical to the external objects, or similar images. What do "identical" and "similar" mean? For example, when we see a person, that person is an image within our own mind, not the real person outside, not the appearance of the original substance, but it should be consistent with the actual person—identical or similar. The image we see within the supreme faculty is manifested as-it-truly-is by our own tathāgatagarbha in accordance with the real person outside. Only the tathāgatagarbha can see and contact the real person outside. So does the real person outside have height, tallness, shortness, length, squareness, roundness, and build? Certainly yes, and these were produced in the womb by his tathāgatagarbha, including the mental sense-objects of limbs, head and feet, weight, height and size, and so forth. When another person sees this person, that person's tathāgatagarbha will, in accordance with this person's original appearance, manifest within his own supreme faculty an identical or similar image of the inner six sense-objects, and that person will simultaneously see this person's colors, his height and build, his size, the shapes of his five faculties, his temperament and disposition, and other such mental sense-object characteristics.

Therefore, when the tathāgatagarbha manifests one's own body of the five aggregates, it also simultaneously manifests one's own height, build, shape, and weight. When others look, the tathāgatagarbha can rely upon these to manifest an identical image within their minds, and only then can others truly discern this person's size, height, build, and weight.

The periscope of a submarine, or the refracting lens on a tank that resembles a periscope, displays in the mirror scenes and figures exactly identical to the real ones, without the slightest discrepancy. This is the same as the mirror-image principle of the tathāgatagarbha; this is precisely the mirror-like contemplation the Buddha taught. If there is a problem with the eye faculty, and the information gathered by the tathāgatagarbha undergoes distortion as it passes through the eye faculty, the information arriving at the supreme faculty will also be distorted, and the mirror image given by the tathāgatagarbha will likewise appear distorted. What the eye consciousness and the mind consciousness see will also be distorted—possibly a distortion of color or of shape. Setting aside the constraints of identical karma and healthy five faculties, the mirror image manifested by the tathāgatagarbha is certainly exactly identical to the actual object.

We can reason from our own material body: whether the tathāgatagarbha has fashioned for us the limbs and the head, and whether the head and limbs of others that we see should be more or less the same as those persons themselves; and when others look at our own limbs and head, whether these are also more or less the same as our real limbs and head.

If the tathāgatagarbha had not fashioned for us the shapes of the limbs and head—these external mental sense-objects of visible form—then by what means would each sentient being know that he has a head and limbs, and be able to see the inner mental sense-objects of head and feet, limbs, five faculties, height and build? By what means could he have the various functions of the body faculty? These inner mental sense-objects cannot possibly arise out of nothing; they cannot possibly appear without something to rely upon. It must be that the tathāgatagarbha, in the womb, produced the sentient being's head and limbs and so forth—the visible form, expressive form, and unexpressed form. The same applies to other material forms: at their initial formation, there must certainly be the external mental sense-objects of visible form, expressive form, and unexpressed form.