There is a great upheaval in the evangelical church regarding how Christians should engage culture. The most common form of understanding, at least among American evangelicals, is the "Christ and Culture" model set forward by H. Richard Niebuhr. In this model the theory of "two kingdoms," namely the kingdom of Christ and the kingdom of the world, is central. This emphasis resulted in the strong secular and sacred distinctions that we find in fundamentalism, as well as in much evangelicalism.
This view is correct in so far as it reminds us of the very real enmity that exists between these two kingdoms until Christ comes again. While we live in both kingdoms now, and have responsibilities to both (cf. Romans 13) kingdoms, we are to give absolute homage to Christ alone. We will not bring in his kingdom by our efforts to transform the kingdom of the world. He stands over the world and thus must always remain our higher authority. Niebuhr referred to this thinking as "Christ-and-culture-in-paradox." The paradox explains the dominant way that most evangelicals, until the last twenty years