The contrast between darkness and the light of Christ appears often in the Gospel according to John and was addressed by Pope Francis in first encyclical.There is a spiritual battle that continually goes on between light and darkness. It is a battle between the light of Christ that is in each of us, and is to shine through us, versus the darkness that comes from the evil one and his kingdom.
“I am the light of the world. Whoever follows me will never walk in darkness, but will have the light of life” (John 8:12).
“You are the light of the world. A city set on a mountain cannot be hidden. Nor do they light a lamp and then put it under a bushel basket; it is set on a lamp stand, where it gives light to all in the house. Just so, your light must shine before others, that they may see your good deeds and glorify your heavenly Father (Matthew 5:14-16).
“For He rescued us from the power of darkness, and brought us into the kingdom of His beloved Son, in whom we have redemption, the forgiveness of sins” (Colossians 1:13-14).