From the Kena Upanishad or kenopanishad:
Not that which the eye can see, but that whereby the eye can see: know that to be Brahman the eternal, and not what people here adore;Not that which the ear can hear, but that whereby the ear can hear: know that to be Brahman the eternal, and not what people here adore;Not that which speech can illuminate, but that by which speech can be illuminated: know that to be Brahman the eternal, and not what people here adore;Not that which the mind can think, but that whereby the mind can think: know that to be Brahman the eternal, and not what people here adore.
The One Power that illumines everything and everyone is indivisible. It is the Ear behind the ears, Mind behind the mind, Speech behind speech, Vital Life behind life. The ears cannot hear it; it is what makes the ears hear. The eyes cannot see it; it is what makes the eyes see. You cannot speak about it; it is what makes you speak. The mind cannot imagine it; it is what makes the mind think. It is different from what all we know; yet it is not known either. Those who feel they know Him know Him not. Those who know that anything amenable to the senses is not Brahman, they know it best. When it is known as the innermost witness of all cognitions, whether sensation, perception or thought, then it is known. One who knows thus reaches immortality.
Kena is Sanskrit meaning “by whom”.
