The light of the body is the eye: if therefore your eye be single, your whole body shall be full of light.
The "eye" is "single," not because it sees one thing, but because it looks in one direction. It is a simplicity, not of the intellectual, but of the moral regards. It marks one ruling passion to which all others are pressed into subservience. A navigator may set his mind on the discovery of some distant region, and may repel all the temptations he meets with in his way; not allowing the luxury of one place, or the gain of another, to detain him. Here is singleness of eye; but yet he attends to the waters below, and to the firmament above, and to the compass by which he steers his course. Here the object is one, but its pursuit is illuminated by the light of many sciences.
Parallel VersesKJV: The light of the body is the eye: if therefore thine eye be single, thy whole body shall be full of light.