The light of the body is the eye: therefore when thine eye is single, thy whole body also is full of light; but when thine eye is evil, thy body also is full of darkness. Take heed therefore that the light which is in thee be not darkness. If thy whole body therefore be full of light, having no part dark, the whole shall be full of light, as when the bright shining of a candle doth give thee light.
The eye is the lamp of the body. Not an eye, but the eye. Not the hand, not the tongue, but the eye. Specifically, it is the eye that is the organ that illuminates the man.
Specifically, when the eye is set correctly, the entire body is filled with light. This means the solution to being fully illuminated is not in the performance of a thing, nor in the individual execution of any deed, but solely based upon the focus, or gaze of an individual.