The Principle of Refraction Explains the Illusion When Seeing Form

Seeing form with the eye requires light; light is one of the conditions for seeing form, and without light, form cannot be seen. Light serves to reveal material sense-objects: as long as a material sense-object is within a light source, the light can reveal it. Then the tathāgatagarbha takes in the four great element particles on the material sense-object and transmits them to the gross physical sense organ of the eye, and further, through the nervous conduction system, transmits them into the black box. The six sense-object realms, such as the material sense-object, that eye consciousness discerns 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 sense-object realms outside; they are images conjured in a phantom mirror.

The principle of refraction can demonstrate that the material sense-object seen by eye consciousness inside the black box is not the true original material sense-object outside, but a form that has changed and merely resembles the original material sense-object—it is not true form. Light travels at a definite 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 material sense-object happens to appear right at the boundary between media, the light will reveal it there, and the image revealed in the two media will undergo a change.

For example, air and water are two media with different resistance to the propagation of light. When light travels from air into water, its direction of propagation changes, and the revealed material sense-object changes accordingly, while the material sense-object itself does not change. For instance, when a chopstick is half-inserted in water, the light reveals the part of the chopstick in the air and the part in the water separately, and their relative positions change, so eye consciousness sees the chopstick as bent. Does this phenomenon of bending occur in the supreme faculty, the black box, or does it occur at the outer representation, the substantial object realm, before it is transmitted to the eye faculty?

If the chopstick in the outer substantial object realm of material sense-objects were truly bent, then when you take the chopstick out of the water, would it be bent? The chopstick of the substantial object realm, no matter what medium it is in, does not change; otherwise, it would be altered when taken out of the medium. In fact, it is not altered—it is the same as before. Does the black box deceive people? Does 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 discerned by your six consciousnesses are real? Are you still so self-assured? Still going around every day saying this and that, declaring this right and that wrong—have you really seen anything clearly?

Even seeing someone steal something with your own eyes may not mean they were stealing; even catching them red-handed with the stolen goods may not be the truth; even eyewitness testimony and physical evidence may not be true evidence; even if someone hits you or scolds you, it may not mean they hate you; even if someone cares for and looks after you, it may not mean they love you; sharp words are not necessarily harshness; thunderous force is not necessarily viciousness. When the eye's light 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 actually 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 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 eye consciousness and mind consciousness. The light beam also makes the position of the fish in the water appear very shallow, 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, where eye consciousness cannot see it.

Light 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 fact, there is nothing there at all—it is merely the solitary mental consciousness indulging in wild fancies.