Dietrich Bonhoeffer

Let the Christian remain in the world, not because of the good gifts of creation, nor because of his responsibility for the course of the world, but for the sake of the Body of the incarnate Christ and for the sake of the Church. Let him remain in the world to engage in frontal assault on it, and let him live the life of his secular calling in order to show himself as a stranger in this world all the more. But that is only possible if we are visible members of the Church.

Dietrich BonhoefferThe Cost of Discipleship1961 edition, 297.