Earlier this year I attended a seminar at which Bishop Todd Hunter was one of the speakers. I was struck by a simple two-part truth he laid down for us- He said we most effectively grow God's Kingdom here on Earth when we are both (1) differentiated from the culture, and (2) committed to the culture:
Differentiated from the culture by being a community centered on the uniqueness of Christ (God incarnate) and work of Christ (His Cross and Resurrection).
Committed to the culture by being ambassadors of Christ for the sake of the world. In the great economy of the Kingdom of God, we live the Faith for the sake of others.