Ken Wilbur

The Witness is that which is capable of observing the flow of what is—without interfering with it, commenting on it, or in any way manipulating it. The Witness simply observes the stream of events both inside and outside the mind-body in a creatively detached fashion, since, in fact, the Witness is not exclusively identified with either. In other words, when you realize that your mind and your body can be perceived objectively, you spontaneously realize that they cannot constitute a real subjective self. As Huang Po put it, "Let me remind you, the perceived cannot perceive."