If the gospel is to challenge the public life of our society, if Christians are to occupy the "high ground" which they vacated in the noontime of "modernity," it will not be by forming a Christian political party, or by aggressive propaganda campaigns. Once again it has to be said that there can be no going back to the "Constantinian" era. It will only be by movements that begin with the local congreation in which the reality of the new creation is present, known, and experienced, and from which men an women will go into every sector of public life to claim it for Christ, to unmask the illusions which have remained hidden and to expose all areas of public life to the illumination of the gospel. But that will only happen as and when local congregations renounce an introverted concern for their own life and recognize that they exist for the sake of those who are not members, as sign, instrument, and foretaste of God's redeeming grace for the whole life of society.
From Greg Wood @ the Carpenter's Project blog