Darkness is the world estranged from God, spiritually ignorant and blind, fallen and sinful, dominated by Satan. Isaiah 9:2 depicts the coming Messiah as light entering darkness. Isaiah 60:1–5 sees a time when the nations walk in God’s light. In the battle between Jesus and Satan, Jesus is the overwhelming victor.1
The light shining in the darkness thus refers to the Word coming into the world and revealing truth about God.
5 The light shines in the darkness, and the darkness has not overcome it.