"Further, I believe ... that the God in whom we trust for the fulfillment of the promise is also the Creator of the universe and Lord of history in a manner that assures a certain correspondence, albeit disordered by sin, between His will and human reason and the laws of nature. As a result, ethics grounded in and thoroughly compatible with Christian faith is “accessible” also to non-Christians. It is, in other words, a public ethic. The Christian tradition provides various ways of describing such an ethic—e.g., natural law, common grace, orders of preservation, the twofold kingdom. This is the ethic that is pertinent to the right ordering of the earthly polis, and Christians are not “compromised” when they employ it. Indeed they have a Christian duty to do so. Why there should be such a public ethic is itself part of the Christian story about the nature of God’s world." Source: http://www.firstthings.com/article.php3?id_article=5704