The short quatrain in verses 6:22 and 6:23 of the Gospel of Matthew is like a Zen koan. The King James Version is particularly troublesome due to the mistranslation of the Greek word for “healthy” to the word “single”.
The light of the body is the eye. Therefore, if your eye is single, your whole body will be full of light. But if your eye is evil, your whole body will be full of darkness. If the light that is in you is darkness, how great that darkness will be!
This led Ethan Walker III, in his excellent book “The Mystic Christ”, to write:
Here Jesus is not talking about the two eyes in our heads. In this scripture, he only uses “eye” in the singular form. By this, he means our understanding, our vision, our minds eye if you will.
But the word “single” is due to a mistranslation. The translators of the New International Version went back to the original Greek. They render the quatrain as:
The eye is the lamp of the body. If your eyes are healthy[c], your whole body will be full of light. But if your eyes are unhealthy[d], your whole body will be full of darkness. If then the light within you is darkness, how great is that darkness!
This still doesn’t make much sense, but the translators include the following helpful notes:
[c] 22 The Greek for healthy here implies generous.
[d] 23 The Greek for unhealthy here implies stingy.
Jesus believed that the self was identical with the body, which is why he said that when the Kingdom of Heaven came, the dead would be physically resurrected. Combining this fact with the translators notes, the meaning becomes clear:
The eyes are the lights of the self. If you see the world through generous eyes, you will be full of light. But if you see the world through the eyes of scarcity, your self will be filled with darkness. If the light within you becomes darkness, how great that darkness will be!