To live life as God designed it we must have light.
This goes all the way back to the first day of creation when God created day and night and said "Let there be light."
God made us to live out our purpose in the light... specifically, the light of His presence.
When the first man and woman chose to live apart from God and hid from His presence, they set humanity on a path of darkness -- where men love darkness rather than light.
Yet this didn't deter God from fulfilling His plan for mankind to live in His light.
In fact, the entire Old Testament is really about preparing those who live in darkness for the light to come.
When Jesus was born, He came as the light of the world... and as the light shines in the darkness, the darkness cannot overcome it.
And as we walk with Him now we have the light of life... as His blood cleanses us from all sin.
Also... in Him we have become the light of the world. A city set on a hill that can't be hidden.
Eventually, that city will be built up as God planned... and it will have no need of sun or moon to shine on it, for the glory of God will give it light, and its lamp will be the Lamb.
In the meantime, we who were once darkness are to walk as children of light.
And we can do so with confidence and rejoicing... knowing true light, which enlightens everyone, has come into the world.