When a person shouts in an empty valley, there is a reverberation of sound. In folklore this is called the spirit. Because it has a voice but no form, it is called the spirit of the valley.
What I realize as I observe this is the Tao of nurturing the spirit in emptiness.
If people can be empty within, this is the valley. Within emptiness there is a point of spiritual energy, hidden inside; this is the spirit.
This valley is tranquil and unperturbed, this spirit is sensitive and effective. Only the valley can be spiritual- without the valley there is no spirituality. The marvel of the spirit is only in the valley.
People of the world are full of personal desires that block up the spiritual opening, polluting it in a hundred ways – how can they have a valley? Since they do n o t have the valley, they are confused and troubled, like drunkards or dreamers; their spiritual energy wanes away, so how can they have the spirit? Once they have lost the spirit, even though alive they are as if dead.
If you can sweep away all entanglements and wash away accumulated obsessions, so as to be clean and naked, bare and free, with nothing at all, then in that empty valley there will naturally be something indefinable with essential vitality, a non psychological spirit that is responsive, effective, and wise. Let go, it fills the universe; wrapped up, it is stored in secrecy. Thereby one can be a peer of heaven above and earth below.
Reference: Awakening to the Tao Lui I-ming translated by Thomas Cleary