The eyes are the lamp of the body (v22). Jesus seems to be teaching that the ἁπλοῦς (simple singularity, wide-open perfection, generosity) of our aim and attention has the ability to let us see our world in a way that is bathed in light. It is not a way that I viewed the world in the past. What a marvelous idea: that our body—our temple we are called to keep; the place of our action, the creation we are given to tend—will light up everywhere: It will be full of light—it is a completely different way of looking at the world. To see with a perfect eye seems to mean that our landscape (a landscape of action where the kingdom of heaven meets the kingdom of earth) will glimmer with light. It is something much more like: “If I set my eye on Jesus, my responsibilities will shine forth before me. And if I accept and follow that flawlessly lit path, I get to be a royal priest transforming this world into a new heaven and a new earth.
A lamp is simply a lamp. It has no light of its own. It must receive light to give light. But beware of improper aim and attention. That lamp is lit with a dark light. And the light it gives is a darkness that fills the body—this kind of darkness is not an absence of light—it is a great and terrible presence.
A C.S. Lewis quote that I often think about is:
“I believe in Christianity as I believe the sun has risen: not only because I see it, but because by it I see everything else.”