I am currently enjoying reading Radical Reformission by Mark Driscoll of Mars Hill Church in Seattle - a book about trying to engage with culture without losing the (gospel) plot. Driscoll's big passion for the world and for the Lord Jesus is on every page. Moreover, his chapter on the twin pitfalls of syncretism (when the Church becomes too much like the world) and sectarianism (when the Church hides away from the world) reveals strong convictions about the scope of the gospel's power.
The problem with both syncretism and sectarianism is that they deny the clear teaching of the Scriptures that the power of God unleashed through the gospel of Jesus Christ can transform anyone. Sectarians do not live by the necessary faith in the gospel and therefore believe that evil hearts and sinful actions and worldly social structures are more powerful than God, unable to be redeemed, and therefore are a waste of our energies because they are destined to be meat on God's grill anyway, so why bother? Likewise, syncretists do not live by the necessary faith in the gospel and therefore believe that the hearts of people aren't that bad, their actions aren't that sinful, and since people are doing the best they can, we can't expect any sort of radical transformation, and so we should simply bless them with a sentimental love.
What he says at the end of the chapter is pure gospel optimism rooted in a reformed model of culture.
Here's what I'd like you to remember from this chapter: reformission is not about abstention; it is about redemption. We must throw ourselves into the culture so that all that God made good is taken back and used in a way that glorifies him. Our goal is not to avoid drinking, singing, working, playing, eating, love-making, and the like. Instead, our goal must be to redeem those things through the power of the gospel so that they are used rightly according to Scripture, bringing God glory and his people a satisfied joy.
[Previous posts on Gospel Optimism HERE]