Jesus’ light powers and fills the universe. A portion of that light is within each of us, too.
In the Gospel of John, it says
In him was life, and that life was the light of all mankind.
The light shines in the darkness, and the darkness has not overcome it.
There was a man sent from God whose name was John.
He came as a witness to testify concerning that light, so that through him all might believe.
He himself was not the light; he came only as a witness to the light.
The true light that gives light to everyone was coming into the world.
He was in the world, and though the world was made through him, the world did not recognize him (NIV, John 1:4 - 10).
Nothing in the universe could shine without this light, but this light also enlightens our hearts and minds. There can be no life without light, but there can be no righteousness or eternal life without the light of Christ. You bring this light with you when you are born but it can increase and decrease during your life, depending upon several things. If you seek evil and are unkind, the light decreases. If you seek Christ and His righteousness, it increases. If you become so finely tuned to the things of God that you desire nothing more, your body can be filled with light. As it fills with light, it begins to understand eternal truth. You can grow in light until you are like Christ--that is, that you share in His attributes.
“Then spake Jesus again unto them, saying, I am the light of the world: he that followeth me shall not walk in darkness, but shall have the light of life” (KJV, John 8:12).
“But if thine eye be evil, thy whole body shall be full of darkness. If therefore the light that is in thee be darkness, how great is that darkness!” (KJV, Matt. 6:23).