"In Him (Jesus) was life, and the life was the light of men. And the light shines in the darkness, and the darkness did not comprehend it."
John 1:4-5

I quote from "Vine's Expository Dictionary":
"Light requires an organ adapted for its reception. (Matthew 6:22-23, "The lamp of the body is the eye. If therefore your eye is good, your whole body will be full of light. But if your eye is bad, your whole body will be full of darkness..."). Man, naturally, is incapable of receiving spiritual light inasmuch as he lacks the capacity for spiritual things, (1Corinthians 2:14, "But the natural man does not receive the things of the Spirit of God, for they are foolishness to him; nor can he know them, because they are spiritually discerned.") Hence believers are called 'sons of light'.not merely because they have received a revelation from God, but because in the New Birth they have received the spiritual capacity for it." End of quote.

"The earth was without form, and void; and darkness was on the face of the deep...Then God said, 'Let there be light' and there was light."
Genesis 1:2-3
"For it is the God who commanded light to shine out of darkness who has shone in our hearts to give the light of the knowledge of the glory of God in the face of Jesus Christ." 2 Corinthians 4:6

The Lord Jesus is the illuminator of men as we see in our opening verse as well as the following-- Speaking to Nicodemus who came to Jesus at night, "He who believes in Him is not condemned; but he who does not believe is condemned already, because he has not believed in the name of the only begotten Son of God. And this is the condemnation, that the light has come into the world, and men loved darkness rather than light, because their deeds were evil.'" John 3:18-19 (Read Vs. 1-21 for the whole scenario.)

Speaking to the Pharisees,
"Jesus spoke to them again, saying, 'I am the light of the world. He who follows Me shall not walk in darkness, but have the light of life."
John 8:12

Speaking to His disciples,
"As long as I am in the world I am the light of the world." John 9:5

Jesus teaching the people in John 12,
"'While you have the light, believe in the light that you may become sons of light'..." Vs. 36 "I have come as a light into the world, that whoever believes in Me should not abide in darkness." Vs. 46

As for Believers, we are no longer in the dark, but we have passed from darkness into light.
Jesus says of Believers,
"You are the light of the world..." Matthew 5:14 "Let your light so shine before men, that they may see your good works and glorify your Father in heaven." Vs. 16

"But you are a chose generation, a royal priesthood, a holy nation, His own special people, that you may proclaim the praises of Him who called you out of darkness into His marvelous light." 1 Peter 2:9

"You are all sons of light and sons of the day. We are not of the night or darkness." 1 Thessalonians 5:5

"For you were once darkness, but now you are light in the Lord, Walk as children of light. Ephesians 5:8

Our walk as children of light is--
By faith:
"For we walk by faith not by sight." 2 Corinthians 5:7

In the Spirit:
"...Walk in the Spirit, and shall not fulfill the lust of the flesh."
Galatians 5:16

In love:
"And walk in love, as Christ also has loved us and given Himself for us..."
Ephesians 5:2

With caution:
"See then that you walk circumspectly, not as fools but as wise."
Ephesians 5:15

In Christlikeness:
"He who says he abides in Him ought himself also to walk just as He walked."  1 John 2:6

Holy Spirit lead in the way we should go, so that this light of Christ in us will be seen by those still in darkness, so that they may be translated into God's kingdom of light. Thank You Lord God for this life in Christ which is life and light indeed. Amen