Paul seems to make a pretty weighty statement here. Christians are not just brought from a state of darkness to a state of light. Rather, we have been delivered from a domain. Darkness is not just a state, it is a kingdom, it is a domain, it is a stronghold. When we are under the domain of darkness, we belong to this kingdom. Our citizenship belongs to darkness, to the Evil One and we are under his rule. Yet, God has delivered us. He has completely transferred us. Reality has completely changed. Our citizenship is no longer in the kingdom of darkness, but in the kingdom of Jesus. The new kingdom reverses the affect of darkness.
Whereas before, when I lived under the domain of the Evil One, under the kingdom of darkness, my life was defined by the one who ruled me. But now, having been delivered from the darkness, into the glorious kingdom of Christ, my life is defined by my New King. I am under His rule. My citizenship is in Heaven. I belong to Him. I am defined by what my New King has accomplished, which Paul states so plainly saying, 'in whom we have redemption, the forgiveness of sins.'
This verse encourages me to live under the reality of my new domain. I am no longer under the allegiance of sin because I have transferred kingdoms. My allegiance, my life, my everything is with Christ. What a glorious truth! I once was a slave, under the oppressive rule of darkness, but Jesus died to redeem me, to set me free from my bondage. Now I am free. And in my freedom, I gladly bow to my New King.