Looked at, but cannot be seen That is called the Invisible (yi). Listened to, but cannot be heard - That is called the Inaudible (xi). Grasped at, but cannot be touched - That is called the Intangible (wei). These three elude our inquiries And hence blend and become One.

We look at it, and we do not see it, and we name it 'the Equable.' We listen to it, and we do not hear it, and we name it 'the Inaudible.' We try to grasp it, and do not get hold of it, and we name it 'the Subtle.' With these three qualities, it cannot be made the subject of description; and hence we blend them together and obtain The One.

The skilful masters (of the Tao) in old times, with a subtle and exquisite penetration, comprehended its mysteries, and were deep (also) so as to elude men's knowledge.

Because the eye gazes but can catch no glimpse of it, It is called elusive. Because the ear listens but can not hear it, It is called the rarefied. Because the hand feels for it but cannot find it, It is called the infinitesimal. There three, because they cannot be further scrutinized, Blend into one.