In a 2000 sermon, John Piper draws out six truths from 1 Peter 2:9-17 about how Christians should be involved in society and culture.
1. We were once all in darkness, along with the whole world.
Notice the phrase near the end of verse 9: "Him who has called you out of darkness." We were once in darkness. The darkness of sin and unbelief and ignorance about God and his ways. It was the darkness of deadness in sin, as Paul says in Ephesians 2:5. This is the condition of our culture and our society. And we were once a part of it by nature. Why are we no longer?
2. God called us out of darkness into his marvelous light.
This truth comes from the same phrase in verse 9: "Him who has called you out of darkness into His marvelous light." We are not by nature smarter or wiser or more courageous than those who remain in darkness. The difference is that God exerted toward us an absolutely undeserved and compelling kindness: he called us. Paul put it like this in1 Corinthians 1:23-24, "We preach Christ crucified, to Jews a stumbling block and to Gentiles foolishness, but to those who are the called, both Jews and Greeks, Christ the power of God and the wisdom of God." It was the omnipotent call of God that wakened us from the spiritual sleep of death and opened our eyes to the power and wisdom of God in Christ. Let us never forget: Free and powerful grace alone is the decisive reason that we are able to see the darkness of our culture and be free in some measure from it.
[Read the rest of the article at Desiring God.]