Again, these words embody more than we may ordinarily take them to mean, so I will talk about the special meanings of the following words: world, sound, contemplation, and liberation. ‘World,’ for instance, is not limited to the planet Earth or even the known universe. It refers to all dimensions of reality, all directions, and all times.

Likewise, ‘sound’ is not limited to physical sound. It refers to all phenomena perceived by the mind—from subtlest to most apparent, including thoughts. How does one contemplate sound? At first, one listens to actual sounds in the environment. Eventually, the listening turns inward, and the minds, contemplating the very nature of the self, becomes so one-pointedly focused that the hearing faculty no longer perceives sound.

Ultimately, when you realize the most profound emptiness of self, you can use the five sense faculties—seeing, hearing, smelling, tasting, and touching—interchangeably. You can listen with the eyes or see with your whole physical being. This is not the same as a blind person using the other senses to compensate for lost sight. Using all sense faculties interchangeably is an outcome of training and an expedient skill of liberation. Having freed themselves from attachment to self and realizing emptiness, it is as if bodhisattvas do not see anything when they look at things. This is not stupidity or inattentiveness. This is so because bodhisattvas are not attached to their sense perceptions or to the objects of their perception.