The world is a place of darkness, dominated by sin and ungodliness.  Long before God sent His Son to rescue man, Gentiles turned their backs on God.  Paul wrote the following concerning them.

Romans 1:21 (ESV)
21  For although they knew God, they did not honor him as God or give thanks to him, but they became futile in their thinking, and their foolish hearts were darkened.

In place of God, they worshipped images of man, birds, animals, and even creeping things (Romans 1:23).  Their rejection of God led them to the vilest behavior possible (vers. 26-32).  They walked in darkness.

The Jews did not do much better.  The truth is, they were more morally corrupt than even the Gentiles, for they had access to the revealed will and ways of the Lord through the law that He gave them, but they refused to live by it.  Paul had some harsh words for them in the book of Romans as well.

Romans 2:17-24 (ESV)
17  But if you call yourself a Jew and rely on the law and boast in God 18  and know his will and approve what is excellent, because you are instructed from the law; 19  and if you are sure that you yourself are a guide to the blind, a light to those who are in darkness, 20  an instructor of the foolish, a teacher of children, having in the law the embodiment of knowledge and truth— 21  you then who teach others, do you not teach yourself? While you preach against stealing, do you steal? 22  You who say that one must not commit adultery, do you commit adultery? You who abhor idols, do you rob temples? 23  You who boast in the law dishonor God by breaking the law. 24  For, as it is written, “The name of God is blasphemed among the Gentiles because of you.”

If both Jews and Gentiles failed to live the life God designed for them to live, who was left to do good in His eyes?  The answer is no one.  Paul wrote, “All have turned aside; together they have become worthless; no one does good, not even one” (Romans 3:12). 

It was into this kind of world that God sent His Son to be the light.  John said of Jesus, “In Him was life, and the life was the light of men” (John 1:4).  Jesus, Himself, bore witness of this truth.  

John 8:12 (ESV)
12  Again Jesus spoke to them, saying, “I am the light of the world. Whoever follows me will not walk in darkness, but will have the light of life.”
 

Light is revealing.  It makes it possible to see clearly.  By His life, and through His teaching, both His own, and that of His inspired messengers, Jesus revealed God’s saving will to mankind.  We know how we should live because Jesus has shown us the way.  He has shown us by His life how to deny ungodliness and worldly lust, and through His Word He has taught us to live soberly, righteously, and godly, in this present world (Titus 2:12).  Now we can walk in the light and maintain fellowship with God (1 John 1:7).

The light of Christ has also revealed God to us.  We know what our heavenly Father is like because we can see Him in Christ.  When Philip asked Jesus to show them the Father, He said, “Have I been with you so long, and you still do not know me, Philip?  Whoever has seen me has seen the Father…” (John 14:9).  What do we know about Jesus?  We know that He is loving, good, compassionate, kind, and morally perfect.  Since Jesus is the image of God (Colossians 1:15), and the exact imprint of His nature (Hebrews 1:3), we know that the Father is loving, good, compassionate, kind, and morally perfect.  We know this because the Light of this world has revealed it to us.

As you wind down for the night, think about these things.