The Principle of Refraction Explains the Illusion When Seeing Colors

Seeing forms with the eyes requires light; light is one of the conditions for seeing forms—without light, forms cannot be seen. Light serves the function of revealing material sense-objects (rūpa-viṣaya). As long as a form is within a light source, the light can reveal it. Then the tathāgatagarbha takes in the four great element particles on the form and transmits them to the gross physical eye faculty, and further transmits them through the nervous conduction system into the black box. The realms of the six sense-objects, such as the forms recognized by the eye consciousness, are all illusory shadows, differing to some degree from the original six sense-object realms. The six sense-objects in the black box are not the substantial object-realms outside; they are images conjured up in a mirror.

The principle of refraction can demonstrate that the form seen by the eye consciousness within the black box is not the true original form outside, but a form that has undergone change and merely resembles the original form—it is not true form. Light travels at a certain speed, and its speed differs in different media, because different media have different material structures and thus different resistance. When light passes through two media, its direction of propagation changes at the boundary between the media, and refraction occurs. If a form happens to be present at the boundary between the media, the light will reveal it there, and the image revealed in the two media will undergo change.

Take, for example, air and water as two media: their resistance to the propagation of light differs. When light travels from air into water, its direction of propagation changes, and the revealed form changes accordingly, while the form itself does not change. For instance, if a chopstick is half-inserted into water, the light reveals the portion of the chopstick in the air and the portion in the water separately, and their relative positions change, so the eye consciousness sees the chopstick as bent. Does this phenomenon of bending occur in the black box of the supreme faculty (indriya), or does it occur at the external object-aspect, the substantial object-realm, before it is transmitted to the eye faculty?

If the chopstick in the external substantial object-realm were truly bent, would the chopstick still be bent when taken out of the water? The chopstick of the substantial object-realm does not change regardless of what medium it is in; otherwise, it would look different when taken out of the medium. In reality, it does not look different—it is the same as before. Does the black box deceive people? Does the eye consciousness deceive people? Do you still trust your own eyes? Do you believe that everything you see is real? Do you believe that all the dharmas discriminated by your six consciousnesses are real? Are you still so self-assured? Still talking about this and that every day, saying this is right and that is wrong—have you truly seen anything clearly?

Even seeing with your own eyes someone stealing does not necessarily mean they were stealing; even catching someone red-handed with the stolen goods may not be the truth; even eyewitness testimony and physical evidence may not be true evidence; someone hitting or scolding you does not necessarily mean they hate you; someone caring for and looking after you does not necessarily mean they love you; sharp words are not necessarily harshness; overwhelming thunderous force is not necessarily viciousness. When the eye's vision is not upright, one cannot see the truth; when the mind's light is not upright, one cannot perceive the facts.

The bending of the chopstick is in fact an illusion brought to us by light. The chopstick has not bent; it is because the direction of light propagation changed that the relative position of the chopstick as revealed by the light appears changed, when in fact nothing has changed. The tathāgatagarbha transmits the shadow of the two segments of the chopstick as revealed by the light into the supreme faculty, and the eye consciousness and mind consciousness then see the bent chopstick.

Similarly, when sunlight shines into water, the direction of the light beam changes, making the water appear very shallow, when in fact the water is not shallow—the shallowness is an illusion of the eye consciousness and mind consciousness. The light beam also makes the position of the fish in the water appear shallower than it is, so that if you grab for the fish at that position, you will never catch it. The fish is not at the position seen by your eye consciousness and mind consciousness, but diagonally below that position, invisible to the eye consciousness.

Brightness can bring us illusions, and darkness can likewise bring us illusions. In darkness, we always feel there is something frightening, something unpredictable, something beyond our control, that might invade or threaten us. In reality, there is nothing there—it is merely the solitary consciousness (mano-vijñāna-eka-citta) indulging in wild fancies.